WO2017008078A2 - Apparatuses, methods and systems for downhole imaging - Google Patents

Apparatuses, methods and systems for downhole imaging Download PDF

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Publication number
WO2017008078A2
WO2017008078A2 PCT/US2016/041792 US2016041792W WO2017008078A2 WO 2017008078 A2 WO2017008078 A2 WO 2017008078A2 US 2016041792 W US2016041792 W US 2016041792W WO 2017008078 A2 WO2017008078 A2 WO 2017008078A2
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Prior art keywords
neutron
data
gas
detector
collision
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PCT/US2016/041792
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French (fr)
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WO2017008078A3 (en
Inventor
Christopher J. Gintz
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Advanced Nuclear Devices Corporation
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Publication of WO2017008078A2 publication Critical patent/WO2017008078A2/en
Publication of WO2017008078A3 publication Critical patent/WO2017008078A3/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/002—Survey of boreholes or wells by visual inspection
    • E21B47/0025—Survey of boreholes or wells by visual inspection generating an image of the borehole wall using down-hole measurements, e.g. acoustic or electric
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T3/00—Measuring neutron radiation
    • G01T3/008—Measuring neutron radiation using an ionisation chamber filled with a gas, liquid or solid, e.g. frozen liquid, dielectric
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/04—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
    • G01V5/08—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
    • G01V5/10—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/04—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
    • G01V5/08—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
    • G01V5/10—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
    • G01V5/107—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources and detecting reflected or back-scattered neutrons

Definitions

  • TITLE APPARATUSES, METHODS AND SYSTEMS FOR DOWNHOLE IMAGING
  • Embodiments of this invention relates to apparatuses, methods, and systems for downhole imaging to determine formation properties or characteristics and formation fluid properties or characteristics, especially properties of hydrocarbon fluids in oil and gas wells during and/or after drilling.
  • the following description relates to an apparatus, a method and a system for using fast neutron energy to determine the composition of matter and specifically the hydrocarbon content down hole during drilling of an oil and gas well.
  • embodiments of this invention relates to apparatuses, methods, and systems for downhole imaging to determine formation properties or characteristics and formation fluid properties or characteristics, especially properties of hydrocarbon fluids in oil and gas wells during and/or after drilling, where the imagining uses fast neutron energy, where the apparatuses comprise a down hole tool including a neutron generator subsystem, a neutron detection subsystem, and an analyzing subsystem, where the apparatuses and systems convert detectable neutron induced events into formation and formation fluid properties or characteristics.
  • neutrons have the unique property of being able to penetrate through matter and are used uniquely to probe bulk condensed matter. Since neutrons can be deflected by some surfaces when incident at glancing angles, neutrons can be used as a surface probe without destroying the matter it is being used to analyze. Spectral identification with neutrons of varying energies are being used with proppant that are placed in a subterranean fracture zones are captured with neutron cross sections to identify materials in gas wells.
  • the petroleum industry uses various methods to characterize geological formations. Characteristics of the deposits down hole are determined from the measurements taken and the quantities of hydrocarbons, rock types, etc. Among the characteristics of geological formations the thermal neutron cross section (SIGMA), density, porosity, hydrogen index, salinity and photoelectric factor are usually measured by wireline tools or logging while drilling (LWD) that include neutron and gamma ray detectors. They are placed some distance from the source and generally use the principle of Compton scattering to derive formation density. These measurements were made with single detector tools that had no capability to compensate for borehole effects. The limitations inherent in these tools led to the further development of multiple dual detector density tools in which compensation is based on the spacing between the sources and the detectors. Each source measures a different formation property characteristic and multiple tools are used together in the same logging operation. They also tend to interfere with each other that make the tool string long. See e.g., United States Patent No.7,482,578.
  • United States Published Application No. 20060192096 disclosed methods for formation logging in accordance with one embodiment of the invention includes emitting neutrons and gamma rays into a formation, using a source on a logging tool disposed in a borehole penetrating the formation; and detecting gamma-ray signals and neutron signals scattered by the formation, using at least one detector on the logging tool.
  • United States Published Application No. 20020170348; disclosed a logging tool includes an elongated body housing a neutron source and at least one neutron detector positioned along one side of the neutron source.
  • the logging tool include at least one gamma ray detector longitudinally separated from and to one end of the neutron source, and may be used to make simultaneous gamma ray and neutron logging measurements.
  • the logging tool also includes a (n, 2n)-neutron shield positioned to one end of the neutron detector, longitudinally between the neutron detector and the neutron source.
  • Detection of neutrons requires that the neutron interact with the nucleus of an atom in a material from which it is exiting. The usual result of such an interaction is the emission or recoil of a charged radioactive particle which is subsequently detected.
  • the neutron recoiling emission with matter is then recoiled with a scintillation gas that creates an electron.
  • the electron creates an imaging track from which useful information can be interpreted about the neutrons original interaction with matter.
  • Embodiments of this invention include systems, apparatuses, and methods for detecting detectable neutron events to generate neutron event data, analyzing the neutron event data, and converting the neutron event data into formation solid, liquid, and/or gas properties or characteristics.
  • Embodiments of this invention further include software programs and software methods implemented by or on at least one processing unit for analyzing the neutron event data from the apparatuses or systems of this invention generating the formation solid, liquid, or gas properties or characteristics.
  • the systems, apparatuses, and methods are substantially insensitive or completely insensitive to other forms of radiation including naturally occurring radiation downhole or other radiation forms used in downhole oil and/or gas exploration, but are sensitive to fast neutrons having energies between 100 keV and 15 MeV.
  • Embodiments of the present invention apparatuses and systems include a fast neutron generation subsystem, a detection subsystem, and an imaging subsystem.
  • the fast neutron generation subsystem includes at least one fast neutron source.
  • the detection subsystem also includes at least one detector having a gas chamber and a voltage unit capable of producing a voltage drift region in the gas chamber.
  • Each gas chamber contains a gas mixture including at least one perfluorinated hydrocarbon gas having between 1 and 5 carbon atoms and 4He at a pressure of at about one atmosphere.
  • the gas mixture includes between about 5 vol.% and about 25 vol.% of the at least one perfluorinated hydrocarbon gas and between about 75 vol.% and about 95 vol.% of 4He.
  • Each voltage drift unit includes a plurality of parallel ring (vertically stacked) conductive elements configured to generate a voltage profile across the chamber in its longitudinal direction.
  • the image subsystem includes at least one imaging unit that is capable of detecting or imaging scintillation light produced from fast neutron-4He collisions, resulting electron cascades and drifting through the drift region.
  • the apparatuses and systems may also include a communication subsystem including communication hardware and software capable of transmitting or sending detected neutron event data from the imaging subsystem to and at least one analyzing subsystem
  • Embodiments of the methods and software methods involve detecting, imaging, and/or analyzing fast neutron events occurring in the detection subsystem arising from fast neutron reflected, scattered, and/or refracted by and/or from downnhole formation solids, liquids, and/or gases irradiated by fast neutrons from the at least one fast neutron generator or source.
  • the methods and software methods involve controlling and directing fast neutrons at a geological or downhole structure, detecting neutrons entering the detection subsystem, and capturing images of neutron events within the detection subsystem, and/or capturing neutron event data using the imaging subsystem.
  • the methods and software methods may also include storing the captured images and/or data, transmitting the capturing images and/or data and/or analyzing captured images and/or data to determine formation solid, liquid, and/or gas properties and characteristics.
  • the captured images and/or data are processed downhole and transmitted uphole for output to a user or for further processing, temporarily stored downhole for later processing uphole, transmitted uphole for immediate processing, and/or a combination of thereof.
  • the images and/or data are used in one or more formation evaluation models to derive the desired formation solid, liquid, and/or gas properties or characteristics. Formation models are typically software programs used to evaluate the geological formation based on the images and data gathered downhole.
  • the formation data and/or images are often combined with other measurements (e.g., neutron porosity measurements and resistivity measurements) to determine formation solid, liquid, and/or gas properties or characteristics including, without limitation, gas saturation, lithology, porosity, the density of hydrocarbons, formation pore space, properties of shale sands, and/or other parameters of interest.
  • other measurements e.g., neutron porosity measurements and resistivity measurements
  • the apparatuses, systems, and methods of this invention are designed to assist a driller in improving drilling, thereby improving the rate of recovery of hydrocarbons principally from natural gas wells.
  • the apparatuses, systems, and methods of this invention may also be useful in improving vertical drilling, horizontal drilling or drilling wells including vertical, horizontal or angled sections to improving detection and recovery of formation fluids including hydrocarbons, both gases and liquids.
  • the computer subsystems of this invention are used to capture fast neutron gas collision events occurring within the gas chamber of the neutron detector of a downhole tool as images and associated image data, while a well is being continuously drilled or when a wire line is used during drilling or drill stoppages.
  • the computer subsystems may also include a storage device capable of storing neutron event images and associated data from the imaging subsystem produced by fast neutron returning towards the detector after interaction with formation materials, solid, liquids, and/or gases within a geological formation.
  • the computer subsystems may also include an analyzing subsystem to permit preliminary and/or thorough analysis of the images to determine desired formation solid, liquid, and/or gas properties and characteristics.
  • Embodiments of the invention provide methods for continuously monitoring a location of the detector(s) relative to the fast neutron source and its position within the well.
  • Embodiments of the invention provide methods for continuously measuring interactions between fast neutrons and the gas mixture within the gas chamber of the detection subsystem by creating images of events occurring within the chamber, where the images may be continuously captured over a set period of time before, during and/or after a neutron irradiation event, semi- continuously captured before, during and/or after a neutron irradiation event, or captured due to a threshold triggering event based on monitoring a response of a monitoring unit within the imaging or data capturing component of the imaging subsystem.
  • the neutron detection subsystems of this invention include at least two fast neutron detectors placed at a precise distance from each neutron source, where each detector captures images and associated data of interactions between the fast neutrons entering the gas chamber and the gas mixture in the gas chamber, where the fast neutrons entering the chamber comprise fast neutron reflected by, scattered by, refracted by, absorbed and reemitted by the formation and/or formation fluids after fast neutron irradiation from at least one fast neutron source.
  • the apparatuses and systems of this invention also include a computer and/or processing unit used to operate the imaging subsystem such as a CCD imaging unit, especially a CMOS/CCD imaging unit, that captures images and associated data for subsequent interpretation and image analysis.
  • the apparatuses and systems also include a set of software routines capable of analyzing the images and associated data.
  • the apparatuses and systems also include a tool including the subsystems that is integrated into drilling apparatus.
  • the apparatuses and systems include a tools affixed to a wire line.
  • the detection subsystem comprise directional fast neutron detection subsystem that are capable of detecting fast neutron events within the gas chamber to determine not only energetic properties of the events, but the direction from which the neutrons entered the gas chamber.
  • the apparatuses and systems are attached to a wire line typically used in oil and gas well logging.
  • This attachment may be a physical attachment and may be supplemented by a remote capability that will disconnect the sonde in case the device gets stuck in the pipe and cannot be fished out.
  • the apparatuses and systems send event images and associated data up a data cable to an analyzing subsystem, which is monitored by a remote operator interpreting the data above ground.
  • This operator may be located in proximity to the bore hole such as adjacent to the drilling site or the interpreter may be located remotely over a communication link for remote monitoring and analyzing.
  • the apparatuses and systems provides improved well logging tools for performing nuclear measurements on a subsurface earth formation surrounding a borehole.
  • the tools include detectors capable of detecting gamma rays.
  • the tools improve hydrogen index and neutron porosity measurements.
  • Embodiments of this invention relate to tools for formation logging, where the tools include a support configured for movement in a borehole.
  • the tools also include a neutron irradiation subsystem including at least one neutron source, a neutron detection subsystem including at least one detector, and an imaging or data capturing subsystem including at least one imager or data capture unit.
  • the tools may also include a communication subsystem including communication hardware and software.
  • the tools may also include an uphole and/or downhole analyzing subsystem including at least one processing unit and software routines that interprets the images and associated data to generate formation and formation fluid properties or characteristics.
  • Other embodiments of the invention relate to methods for formation logging that include emitting neutrons into a formation, using a neutron source on a logging tool disposed in a borehole penetrating the formation, and detecting neutron signals from neutrons scattered by the formation, using at least one neutron detector associated with the logging tool.
  • Other embodiments of the invention relate to methods for formation logging that include emitting neutrons into a formation, using a neutron source on a logging tool disposed in a borehole penetrating the formation.
  • the methods also include detecting neutron signals scattered by the formation using at least one neutron detector on the logging tool, the signals being associated with the neutron-gas interactions or neutron events occurring in the neutron detectors.
  • the methods also include deriving a correction signal using high-energy signal spectra from the detected signals, and applying the correction signal to the detected signals to correct for neutron interference and/or borehole effects on the detected signals.
  • Embodiments of this invention provide systems, methods and calculation procedures including a detection scheme that is insensitive to all other forms of radiation used downhole in oil and gas exploration except for fast neutrons having energies between 100 keV and 15 MeV.
  • a tubular structure including a gas chamber containing a mixture of a halogenated hydrocaron (e.g., CF 4 or other halogenated hydrocarbons such as a FREON®, a registered trademark of DuPont) and an inert gas (e.g., 4He) at a given temperature and pressure.
  • a halogenated hydrocaron e.g., CF 4 or other halogenated hydrocarbons such as a FREON®, a registered trademark of DuPont
  • an inert gas e.g., 4He
  • the gas mixture includes from about 75 vol.% to about 95 vol.% of 4He and from about 5 vol.% to about 25 vol.% CF 4 .
  • the interactions between the fast neutrons generated by a neutron generator, referred to herein as initial fast neutrons, and materials in a geological structure downhole produce fast neutrons, referred herein as returning fast neutrons, that are either scattered, reflected, refracted, and/or otherwise directed back toward a detector located within a borehole of an oil/gas well or injection well by or from the materials.
  • a detection subsystem captures via an imager and reported the images to an analyzing subsystem for analysis. The analysis of these images provides drillers with data to improve drilling trajectories, especially in horizontal sections, and thereby improve hydrocarbon production from oil/gas wells, especially gas production from natural gas wells.
  • the present systems and methods may be used for drilling vertical wells, horizontal well or well segments.
  • the analyzing subsystem is used to store and analyze images captured downhole by the downhole detection subsystem either while drilling or during wire line logging.
  • the detection subsystem may operate continuous, periodically, or intermittently while drilling.
  • the analyzing subsystem may include both a downhole component and a surface component. Both the downhole component and the surface component may be involved in analysis of the images and the analysis work may be distributed between to the components so that the downhole component would produce preliminary results and the surface component would produce refined results.
  • Embodiments of the invention provide methods for continuously monitoring formation materials while drilling or during wireline logging based on images captured from at least one detector positioned relative to at least one fast neutron source position within the well.
  • Embodiments of the invention provide methods for continuously capturing and analyzing images generated from detecting returning fast neutrons, which correspond to interactions between formation materials and initial fast neutrons.
  • Embodiments of this invention provide systems including 1) a detection subsystem including at least one fast neutron generator, at least two fast neutron detectors including a gas chamber unit and an imaging unit placed at a precise distance from the at least one neutron generator, where the detectors detect and that capture images of returning fast neutrons collisions of gases of a gas mixture of a gas chamber in the detectors, where the returning fast neutrons correspond to interactions between the initial fast neutrons and the materials in the wellbore and/or in the formation penetrated by the well bore; 2) an analyzing subsystem including at least one processing unit used to operate the imaging unit (e.g., CMOS/CCD imaging system) to detect and capture images of the collisions for subsequent interpretation and image analysis; 3) a data storage subsystem for storing the images; 4) a communication subsystem interconnecting the subsystems; 5) software algorithms for analyzing and interpreting, 6) a power subsystem connected to the subsystems for supplying power to the subsystems; and 7) a connector to aff
  • the detection systems are based on the use of a mixture of a noble gas and a halogenated hydrocarbon gas (e.g.,4He and CF 4 ) that limits interactions with other radiation sources or are tuned to limit interactions with other radiation sources, which would produce spurious signals and/or noise.
  • the detection systems are directional fast neutron detectors that produces images of fast neutron gas collisions including energetics and directional data.
  • the detection subsystems are designed to be attached to a wire line typically used in oil and gas well logging. This attachment is a physical attachment and may be supplemented by a remote communication component that will disconnect the sonde in case the device gets stuck in the pipe and cannot be fished out.
  • the surface analyzing component may be located in proximity to the bore hole such as adjacent to the drilling site or the interpreter may be connected remotely over a communication link and monitored remotely.
  • Figure 1A depicts a functional block diagram of an embodiment of a system of this invention.
  • Figure 1B depicts a functional block diagram of an embodiment of a system of this invention.
  • Figure 2A depicts a functional block diagram of another embodiment of a system of this invention.
  • Figure 2B depicts a functional block diagram of another embodiment of the system of this invention.
  • Figure 3A depicts an embodiment of a wireline tool system of this invention.
  • Figure 3B depicts another embodiment of a wireline tool system of this invention.
  • Figure 4A depicts an embodiment of a drilling and logging system of this invention.
  • Figure 4B depicts another embodiment of a drilling and logging system of this invention.
  • Figure 5 depicts a two detection subsystem embodiment of this invention and illustrative penetration profiles and detection profiles.
  • Figure 6A depict an embodiment of a fast neutron detection subsystem of this invention.
  • Figure 6B depicts an embodiment of a gas delivery subsystem of this invention.
  • Figure 7 depicts illustrates that neutron detection process of the fast neutron detection subsystem of this invention of Figure 6A.
  • Figure 8 depicts an embodiment of a method illustrating the events and steps that lead to the capture, analysis and interpretation of logging data using the systems of this invention.
  • Figures 9A-B depict an embodiment of a method for operating the systems of this invention.
  • Figures 9A and C-D depict another embodiment of a method for operating the systems of this invention.
  • Figures 10A-B depict embodiments of a method for operating the imaging subsystem of this invention.
  • Figures 11-20 depict an embodiment of a CIE imaging analysis used to analyze returning fast neutron energetics.
  • Figure 21 depicts a schematic diagram of a CMOS Sensor Chip.
  • Figure 22 depicts a diagram of typical CMOS Sensor Chip vertical/horizontal shift register associated with image acquisition.
  • Figure 23 depicts a diagram of CMOS Sensor Chip image processing
  • Figure 24 depicts a diagram of a routing matrix associated with associated with memory array architecture.
  • the term "about” means that a value of a given quantity is within ⁇ 20% of the stated value. In other embodiments, the value is within ⁇ 15% of the stated value. In other embodiments, the value is within ⁇ 10% of the stated value. In other embodiments, the value is within ⁇ 5% of the stated value. In other embodiments, the value is within ⁇ 2.5% of the stated value. In other embodiments, the value is within ⁇ 1% of the stated value.
  • the term "substantially” means that a value of a given quantity is within ⁇ 5% of the stated value. In other embodiments, the value is within ⁇ 2.5% of the stated value. In other embodiments, the value is within ⁇ 1% of the stated value. In other embodiments, the value is within ⁇ 0.5% of the stated value. In other embodiments, the value is within ⁇ 0.1% of the stated value.
  • the term "neutron source” means a device that generates fast neutrons having an having energies between 100 keV and 15 MeV so called fast neutrons.
  • the neutron source may include radio nuclei known to emit neutrons having energies between 100 keV and 15 MeV at a desired flux density.
  • the neutron source may be any device that generates neutrons by bombarding a target with particles having a sufficient energy to generate neutrons having energies between 100 keV and 15 MeV at a desired flux density.
  • flux density or flux means the number of particles passing through an unit area per unit of time. Generally, the flux or flux density is in units of particles/m2s or particles/cm2 ⁇ s. Specifically, neutron flux or neutron flux density means neutrons/m2 ⁇ s or neutrons/cm2 ⁇ s.
  • neutron detector means a neutron detector including a body having a gas chamber, a portion of which is surrounded by conductive plates that define a voltage drift region within the gas chamber and the associated electronics and electrical power systems to charge the plates in a differential manner to produce the voltage drift region.
  • the term "logging tool” means an apparatus that is designed to be inserted or dropped into a borehole either as part of a drill string or on a wireline, where the tool includes at least one neutron source and at least one neutron detector and where the tool is capable of detecting and storing data corresponding to formation properties that can be gleaned from detecting neutrons entering the neutron detectors, where the entering neutron may be neutrons scattered, reflected, refracted, and/or reemitted from the formation or formation components.
  • the term "at least one", “one or a plurality”, or “one or more” all mean that the item immediately following these terms include a single item (singular) or many items and the terms may be used interchangeably in the present specification.
  • the terms mean from 1 to 100.
  • the terms mean from 1 to 50.
  • the terms means from 1 to 25.
  • the terms means from 1 to 10.
  • the terms means from 1 to 5.
  • the exact number may be any value between the limits set forth, e.g., from 1 to 100, may be 1, 2, 3, ⁇ , 98, 99, or 100 of the designated items.
  • the term "real time” means that adjustments are made to fracturing parameters during a fracturing operation without a temporal delay due to downhole data correction, processing, transmitting, and implementing the adjustments.
  • the term “near real time” means that adjustments are made to fracturing parameters during a fracturing operation with no temporal delay or substantially no temporal delay due to downhole data correction, processing, transmitting, and implementing the adjustments without a temporal delay due to downhole data correction, processing and implementing the adjustments, where substantially here means that the delay is less than or equal to 2 days. In certain embodiments, the delay is less than or equal to 1 day. In certain embodiments, the delay is less than or equal to 8 hours. In certain embodiments, the delay is less than or equal to 4 hours. In certain embodiments, the delay is less than or equal to 2 hours. In certain embodiments, the delay is less than or equal to 1 hour. In certain embodiments, the delay is less than or equal to 30 minutes.
  • the delay is less than or equal to15 minutes. In certain embodiments, the delay is less than or equal to 10 minutes. In certain embodiments, the delay is less than or equal to 5 minutes. In certain embodiments, the delay is less than or equal to 1 minute. In certain embodiments, the delay is less than or equal to 30 seconds. In certain embodiments, the delay is less than or equal to 10 seconds. In certain embodiments, the delay is less than or equal to 5 seconds.
  • CFA color filter array
  • R,G,B red green, blue
  • STEM stack memory architecture used to move images at high speed thru the computer.
  • CMOS complementary metallic oxide semi-conductor (a semiconductor technology).
  • CIE means French agency that developed the color chromaticity diagram or color palate.
  • ANML means automata network markup language (the computer language use in the imager software).
  • ANDED means adding a value at a computer memory location.
  • TIFFS means multi layer thin film filters for handing geothermal temperatures down hole.
  • nanometer means nanometer
  • new downhole nuclear logging, imaging, or detecting apparatuses and systems may be constructed to include a neutron generator subsystem, a neutron detection subsystem, and an analysis subsystem, where each subsystem is in electronic or electrical communication with the other subsystems.
  • the neutron generator subsystem includes at least one neutron source or neutron generating unit capable of generating a neutron flux of neutrons having energies between 100 keV and 15 MeV.
  • the neutron detection subsystem includes at least one neutron detector including a gas chamber containing a mixture of a halogenated gas and a noble gas at an operating pressure and temperature, a detection cage surrounding the gas chamber, and an electrical or electronic unit for charging the detection cage.
  • the cage includes a plurality of conductive rings and electronic or electrical unit is capable of producing a differential electric field in the chamber to define a voltage drift region within the chamber.
  • Neutrons interact with the gas to generate electrons, which are accelerated in the voltage drift region giving rise to detectable neutron- gas events.
  • the neutron-gas events are then detected by the detection subsystem and analyzed by the analyzing subsystem to determine formation properties and characteristics, where the neutron detection event properties and characteristics include directions from which the neutrons enter the chamber, times from bombardment to detection, neutron energies, and other detectable neutron properties, induced electron properties and induced light properties, and where the formation properties and characteristics including thermal neutron cross section (SIGMA), density, porosity, hydrogen index, salinity and photoelectric factor, and other measurable formation and formation fluid properties and characteristics.
  • SIGMA thermal neutron cross section
  • Embodiments of this invention broadly relate to methods including lowering a neutron detection tool into a borehole of an oil or gas well to a location of a formation to be imaged, where the tool includes at least one neutron source, at least one neutron detector, and at least one processing unit, where each detector includes an imaging unit, a gas chamber having a voltage drift region and a voltage unit capable of generating the voltage drift region and where the source and the detector are separated from each other by a distance D1.
  • the methods also include irradiating the location with initial fast neutrons from the at least one neutron source and capturing images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data.
  • the methods also include analyzing the images on a pixel by pixel basis to determine the collision data, converting the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database, producing a logging record evidencing the location solid/liquid/gas data, and classifying the location solid/liquid/gas data.
  • the at least one neutron source comprises a single neutron source.
  • the single neutron source is an 241Am9Be neutron source.
  • the methods further include conveying the tool within the borehole on a wireline and repeating the irradiating, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole.
  • the methods further include conveying the tool within the borehole on a drill string, where the tool is situated in the drill string proximate a drill bit section or situated in the drill bit section or collar and repeating the exposing, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole.
  • the analyzing step comprises computing a relative location of each collision between an initial fast neutron and a solid, liquid, and/or gas at the location based on the collision data of each gas-returning fast neutron event, calculating an energy of each collision between the initial fast neutrons and the solid, liquid, and/or gas at the location, and modifying each calculation due to interactions between the initial fast neutrons and borehole pipe with or without openings in the pipe.
  • the solid, liquid, and/or gas at the location are characterized and indexed using a hydrogen index.
  • the initial fast neutrons have energies ranging between 100 keV and 15 MeV and the mixture includes CF 4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF 4 and between about 99 vol.% and about 99vol.% 4He.
  • each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software.
  • the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof
  • the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location, and the processing/analyzing unit is local and/or remote.
  • CCD charge coupled device
  • the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1.
  • the processing/analyzing unit is remote from the tool.
  • each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm).
  • the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location.
  • the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
  • Embodiments of this invention broadly relate to methods for creating and capturing an image based on a collision between a gas molecule in a detector and a fast neutron including (a) capturing an image or a plurality of images of each collision between a gas molecule of a gas mixture and a returning fast neutron occurring in a gas chamber of a neutron detector, where the returning fast neutron represents a collision between a solid, liquid, or gas molecule and an initial fast neutron occurring outside of the neutron detector and where each image includes collision data including neutron speed, neutron energetics, neutron entry direction, neutron travel path or track through the detector, (b) determining the collision data on pixel by pixel basis, (c) indexing a precise neutron location of each collision within the detector and relating it to a physical location outside of the detector from which the returning fast neutron entered the detector creating the image or images, and (d) classifying a type of the solid, liquid, or gas molecule from which the returning fast neutron originated based on a comparison to
  • the initial fast neutrons are generated by a single neutron source.
  • the single neutron source is a241Am/9Be fast neutron source.
  • the initial fast neutrons having energies between 100 keV and 15MeV, and the mixture comprises CF 4 and 4He a ratio between about 1 vol.% to about 30 vol.% CF 4 and between about 99 vol.% to about 70 vol.% 4He.
  • the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
  • the methods further include updating and/or refining database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
  • Embodiments of this invention broadly relate to systems for logging oil and/or gas wells including a neutron detection tool having at least one neutron source, at least one neutron detector comprising an imaging unit, a gas chamber having a voltage drift region and a voltage unit capable of generating the voltage drift region within the chamber, and at least one processing unit, where each detector.
  • the source and the detector are separated from each other by a distance D1
  • the at least one source irradiates a location with initial fast neutrons
  • the imaging unit captures an image or a plurality of images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data
  • the at least one processing unit : (a) analyzes the image or images on a pixel by pixel basis to determine the collision data, (b) converts the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database, (c) produces a logging record evidencing the location solid/liquid/gas data, and (d) classifies the location solid/liquid/gas data.
  • the at least one neutron source comprises a single neutron source.
  • the systems further include a wireline on which the tool is lowered into a well or tripped out of the well or a drill string or drill collar in which the tool is situated for logging while drilling.
  • the initial fast neutrons have energies ranging between 100 keV and 15MeV
  • the gas mixture comprises CF 4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF 4 and between about 99 vol.% and about 99vol.% 4He.
  • each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software
  • the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof
  • the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location, the at least one processing unit is local and/or remote, and the at least one processing unit update and/or refines the database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
  • the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1.
  • each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm).
  • the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location.
  • the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
  • the neutron detection subsystem uses a mixture of non flammable, non explosive gasses.
  • the gas mixtures generally include mixtures of a noble gas such as 4He and a halogenated gas such as CF 4 at a desired operating pressure and temperature.
  • Fast neutrons produced by the neutron source are directed at a formation surrounding a borehole of a gas and/or oil well, irradiating or bombarding the formation solids, liquids, and/or gases.
  • a portion of the incident fast neutrons that interact with the formation solids, liquids, and/or gases are scattered, reflected, refracted, and/or otherwise directed back toward the downhole tool or system of this invention entering the detectors of the detection subsystem.
  • the returning fast neutrons collide with the noble gases in the gas mixture.
  • the neutron-gas collision events are analyzed based on a speed and direction of the returning fast neutrons.
  • a strength of interaction between the returning fast neutrons and gases in the noble/halogenated hydrocarbon gas mixture corresponds to energetics the electrons resulting from the interactions and the resulting light generated by the scintillation tracks. That is, a portion of the fast neutrons that are directed at the formation surrounding the borehole enter the neutron detectors producing detectable neutron-gas interactions or events. These events are detected producing event images.
  • the event images are then analyzed to provide information concerning the formation and/or formation fluids.
  • the neutron source comprises a body in which is disposed an effective amount of 241Am, 252Cf, 9Be, or mixtures or combinations thereof, where the effective amount is adjusted to produce a desired flux of fast neutrons having energies between 100 keV and 15 MeV. Additionally, the body is designed so that the neutron flux may be interrupted.
  • the apparatuses and systems of this invention are in the shape of a bullet shaped downhole tool, where the detector or detectors are separated from the fast neutron source by a prescribed distance and the returning neutrons from the neutron bombardment creating images in the detectors.
  • the detectors of this system are capable of detecting neutrons entering the detectors from directionally radial direction and any angle, where other neutron detectors are capable of only detecting neutrons coming from a specific cone of incidence.
  • Sophisticated software methods and software routines are used to capture image and interpret data associated with collisions between returning fast neutrons after interacting with formation solids and/or formation fluids and gases within the neutron detectors of this invention.
  • the neutron-gas events result in electron production, electron acceleration through a voltage drift region of the chamber and the production of scintillation tracks, which are then detected by cameras such as CMOS/CCD cameras and photomultiplier tubes.
  • cameras such as CMOS/CCD cameras and photomultiplier tubes.
  • the detectors of this invention are uniquely designed so that the detectors are sensitive almost exclusively to interactions between fast neutrons returning from interactions with the formation solids and/or formation fluids. Because the detectors are used underground, the gases are shielded from both gamma radiation and thermal neutrons. Thus, the detectors of this invention are capable of very accurately detecting fast neutron-gas interactions with in the chamber with a low noise level and low occurrences of false positives.
  • Embodiments of the methods, systems, apparatuses, and interpretative systems of this invention related to logging or imaging while drilling into downhole reservoirs or formations to determine formation solid properties and characteristics and well as properties and characteristics of gaseous and/or liquid hydrocarbons that may be associated with the formation, specifically crude oil and/or natural gas.
  • An external radiation source typically 241Am (americium) and 9Be (beryllium) is used to generate fast neutrons to bombard downhole formations during oil and/or gas drilling operations.
  • a wire line is placed in the hole to control various instruments and the drill assembly. This wire line typically carries bidirectional electrical and data communication lines to instruments mounted on the drill string at various locations during well drilling operations.
  • two detectors are placed a proscribed geometrical distance apart from the source to read the interaction between the fast neutrons returning from collisions with the materials in the reservoir.
  • the precise location of the collisions used to describe the materials down hole are mapped and indexed to their specific location.
  • the materials are indexed according to their type using a proprietary set of calculations such as a hydrogen index.
  • the gas in the detectors is formulated to be blind to any other form of radiation used down hole for other purposes such as density calculations.
  • the gas detector used in this drilling process is blind to both forms of energy such as thermal neutrons and/or gamma radiation.
  • Each detector typically includes a chamber containing a mixture of CF 4 and 4He gas at a desired compositional mix, a desired pressure (generally, atmospheric pressures), and a desired operating temperature; a electrical and electronic assembly surrounding the chamber adapted to create an interior drift region within the gas chamber; a remote power supply subsystem and connections thereto; a local power supply subsystem; an external communication link; an electrical data transfer link to a uphole analyzing subsystem used for analyzing and interpreting images of neutron-gas interactions or events remotely and for detector control, imaging control and analysis and a physical connection device connecting the detector to the wireline.
  • the detectors may also include a downhole analyzing subsystem also used for analyzing and interpreting images of neutron-gas interactions or events downhole.
  • connections may be operated remotely and electronically.
  • the collisions caused by the interaction of the returning neutrons with the gas molecules in the gas chamber produce a streak or image that is interpreted with imaging software a pixel at a time of an imaging system such as a CMOS/CCD camera or other digital imaging system based on pixelated imaging devices.
  • imaging software such as a CMOS/CCD camera or other digital imaging system based on pixelated imaging devices.
  • the strength of the collisions and the direction of the returning neutrons interacts generated in the chamber filled with the gas mixture are captured by the sensor or imaging subsystem.
  • the detection means uses a mixture of non flammable, non explosive gases.
  • the gas mixtures generally include a noble gas such as 4He and a halogenated hydrocarbon gas such as CF 4 or a FREON® gas at one atmosphere.
  • the fast neutron from a neutron generating source returning from bombarding the surrounding geological formation interact with the gas mixture generating light, which is captured by the imaging subsystem.
  • the captured images include information about the direction and energetic of the returning fast neutrons, which is then analyzed to generate information about formation solids, liquids, and/or gases. This information is used to guide the drilling operations.
  • the traditional means for bombarding a formation is 241Am and/ or 9Be as the source of the fast neutrons.
  • the detection method is located in a bullet shaped tube of a prescribed length and distance from the fast neutron source and the returning neutrons from bombarding the formation creates the image.
  • Two identical fast neutron detectors are located a fixed distance away from the fast neutron source and one detector captures the image from the left side of the bore hole while the other detector captures the image from the other side of the bore hole.
  • Sophisticated computer algorithms are used to image and interpret the collisions between the fast neutrons and the material down the bore hole. These computer algorithms are then used to compare the images that are reduced to a look up table comparing the respective hydrogen indices of the material down hole.
  • Each detector only looks at the interactions between fast neutrons and the resulting collisions with materials down the hole. Since the detectors are used underground and the gas concentration is blind to the energy level of both gamma radiation and thermalize neutrons the system is very accurate with a low noise level and no false positives.
  • a method, an apparatus, and an interpretative system for imaging while drilling down-hole reservoirs of hydrocarbons, specifically natural gas is disclosed.
  • An external radiation source typically 241Am/9Be is used to generate fast neutrons down the bore hole of an oil or gas well being drilled.
  • a wire line is placed in the hole to control various instruments and the drill assembly. This wire line is typically carrying bidirectional electrical and data lines to instruments mounted on the drill string at various locations while a well drilling is in operation.
  • two detectors are placed a proscribed geometrical distance apart from the source to read the interaction between the fast neutrons returning from collisions with the materials in the reservoir. The precise location of the collisions used to describe the materials down hole are mapped and indexed to their specific location.
  • the materials are indexed according to their type using a proprietary set of calculations such as a hydrogen index.
  • One detector is oriented orthogonally to read the left side of the formation while the other detector is oriented in the opposite direction to read the right side of the formation.
  • the gas in the detectors is formulated to be blind to any other form of radiation used down hole for other purposes such as density calculations.
  • the gas detector used in this drilling process is blind to both forms of energy such as thermalize neutrons or gamma radiation.
  • Each detector typically consists of a capsule containing a proprietary mixture of a freon (e.g., CF 4 ) and an inert gas (4He) at a desired temperature and pressure; an amplification circuit and charge amplifier that electronically creates an interior drift region within the gas cell; a remote power system connection; a local battery storage module; a external communication link, an electrical data link to a computer system used for interpretation images remotely and for detector control, imaging control and analysis and a physical connection device connecting the detector to the wore line.
  • This connection may be operated remotely and electronically.
  • the collisions caused by the interaction of the returning neutrons with the gas molecules in the sonde produce a streak or image that is interpreted with imaging software a pixel at a time.
  • the strength of the collisions and the direction from the returning neutrons interact are captured in the sonde filled with the gas mixture.
  • FIG. 1A a schematic representation of an embodiment of a neutron detection system, generally 100, is shown to include a surface component 110 and a downhole component 130.
  • the surface components 110 includes a surface control subsystem 112, a surface analyzer subsystem 114, a user interface subsystem 116, a power supply subsystem 118 and optionally a surface cooling subsystem 120.
  • the surface control subsystem 112 is in two-way communication with the surface analyzer subsystem 114 via a communication link 122a, with the user interface subsystem 116 via a communication link 122b, and with the surface cooling subsystem 120 via a communication link 122e.
  • the surface analyzer subsystem 114 is in communication with the user interface subsystem 116 via a communication link 120c.
  • the surface power supply system 118 is connected to the other subsystems 112, 114, and 116 via power cables 124, which supply power thereto.
  • the downhole components 130 includes a downhole control subsystem 132, a neutron generation subsystem 134, a neutron detection subsystem 136, a downhole power supply subsystem 138, and optionally a downhole cooling subsystem 140.
  • the downhole control subsystem 132 is in two-way communication with the neutron generation subsystem 134 via a communication link 142a, with the neutron detection subsystem 136 via a communication link 142b, and with the downhole cooling subsystem 140 via a communication link 142c.
  • the downhole power supply system 138 is connected to the other subsystems 132, 134, 136, and 120 via power cables 144, which supplies power thereto.
  • the surface control subsystem 112 is in communication with the downhole control subsystem 132 via a communication link 120d. If the system 100 includes the surface and downhole cooling subsystems 120 and 140, then the surface cooling subsystem 120 includes a coolant delivery conduit 124a and a coolant return conduit 124b, which deliver coolant to the downhole cooling subsystem 140 and receive coolant from the surface cooling subsystem 120.
  • the downhole cooling subsystem 140 supplies coolant to the downhole control subsystem 132 and the neutron detection subsystem 136 via coolant delivery conduits 146a and coolant return conduits 146b.
  • the coolant is adapted to keep the electronic components at a desired temperature.
  • the coolant may also be circulated to the neutron generation subsystem 134 as well is the electronic associated that subsystem as needs cooling.
  • FIG. 1B a schematic representation of an embodiment of a neutron detection system, generally 150, is shown to include a surface component 160 and a downhole component 180.
  • the surface components 160 includes a surface control subsystem 162, a surface analyzer subsystem 164, a user interface subsystem 166, a power supply subsystem 168 and optionally a surface cooling subsystem 170.
  • the surface control subsystem 162 is in two-way communication with the surface analyzer subsystem 164 via a communication link 172a, with the user interface subsystem 166 via a communication link 172b, and with the surface cooling subsystem 170 via a communication link 172e.
  • the surface analyzer subsystem 164 is in communication with the user interface subsystem 166 via a communication link 172c.
  • the surface power supply system 168 is connected to the other subsystems 162, 164, and 166 via power cables 174, which supply power thereto.
  • the downhole components 180 includes a downhole control subsystem 182, a neutron generation subsystem 184, a neutron detection subsystem 186, a downhole analyzer subsystem 188, a downhole power supply subsystem 190, and optionally a downhole cooling subsystem 192.
  • the downhole control subsystem 182 is in two-way communication with the neutron generation subsystem 184 via a communication link 194a, with the neutron detection subsystem 186 via a communication link 194b, with the downhole analyzer subsystem 188 via a communication link 194c, and with the downhold cooling subsystem 192 via a communication link 194d.
  • the neutron detection subsystem 186 is in communication with the downhole analyzer subsystem via a communication link 192e.
  • the downhole power supply system 190 is connected to the other subsystems 182, 184, 186, 188, and 192 via power cables 196, which supplies power thereto.
  • the surface control subsystem 162 is in communication with the downhole control subsystem 182 via a communication link 170d.
  • the surface cooling subsystem 120 includes a coolant delivery conduit 124a and a coolant return conduit 124b, which deliver coolant to the downhole cooling subsystem 140 and receive coolant from the surface cooling subsystem 120.
  • the downhole cooling subsystem 140 supplies coolant to the downhole control subsystem 132 and the neutron detection subsystem 136 via coolant delivery conduits 198a and coolant return conduits 198b.
  • the coolant is adapted to keep the electronic components at a desired temperature.
  • the coolant may also be circulated to the neutron generation subsystem 134 as well is the electronic associated that subsystem as needs cooling.
  • FIG. 2A a schematic representation of an embodiment of a neutron detection system, generally 200, is shown to include a control subsystem 202, a user interface subsystem 204, and a power supply subsystem 206.
  • the system 200 also includes a downhole tool 208 including a neutron generation subsystem 210, a neutron detection subsystem 212, and a downhole analyzer subsystem 214.
  • the system 200 may also includes an uphole analyzer subsystem 216.
  • the power supply subsystem 206 is connected to the other subsystems 202, 204, 210, 212, 214 and 216 via electrical connections 218a-f.
  • the subsystems 202, 204, 210, 212, 214 and 216 are in two way communication via communication pathways 220a-h. It should be recognized that not all of the subsystems 202, 204, 210, 212, 214 and 216 are in two way communication with each other, e.g., the neutron generation subsystem 210 is in two way communication with the control subsystem 202, but not necessarily with the neutron detection subsystem 212, not necessarily with the downhole and uphole analyzer subsystems 214 and 216 or not necessarily with the user interface subsystem 204.
  • FIG. 2B a schematic representation of an embodiment of a neutron detection system, generally 250, is shown to include a control subsystem 252, a user interface subsystem 254, and a power supply subsystem 256.
  • the system 250 also includes a downhole tool 258 including a neutron generation subsystem 260, a neutron detection subsystem 262, a downhole analyzer subsystem 264, and a downhole drilling subsystem 266.
  • the system 250 may also includes an uphole analyzer subsystem 268.
  • the power supply subsystem 256 is connected to the other subsystems 252, 254, 260, 262, 264, 266, and 268 via electrical connections 270a-g.
  • the subsystems 252, 254, 260, 262, 264, 266, and 268 are in two way communication via communication pathways 272a-i. It should be recognized that not all of the subsystems 252, 254, 260, 262, 264, 266, and 268 are in two way communication with each other, e.g., the neutron generation subsystem 260 is in two way communication with the control subsystem 252, but not necessarily with the neutron detection subsystem 262, not necessarily with the downhole and uphole analyzer subsystems 264 and 268, not necessarily with the downhole drilling subsystem 266 or not necessarily with the user interface subsystem 254.
  • FIG. 3A an embodiment of a wire line downhole neutron logging tool apparatus, generally 300, is shown to include a wire line, cable, fiber optic cable or wire 302, an electronic power supply and communication cable 304, and a wire line tool system 306.
  • the wire line tool system 306 includes a housing 308.
  • the housing 308 includes a wire line attachment 310.
  • the housing 308 also includes an imaging subsystem 312, a detection subsystem 314, a fast neutron generation subsystem 316, a communication subsystem 318, and a downhole cooling subsystem 319, which supplies coolant to the electronic components associated with the other subsystems.
  • the housing 308 may also include a downhole analyzer subsystem 320.
  • the detection subsystem 314 includes a detector 322.
  • the detector 322 includes a gas chamber 324, a top electric grid 326, a bottom electric grid 328, a voltage drift cage 330, a bottom plate 332 and a window/lens 334.
  • the tool system 306 also includes mounts 336 for mounting the detector 322 on a support/spacer 338.
  • the fast neutron generation subsystem 316 includes a fast neutron source 340.
  • the support/spacer 338 provides a space between the detector 322 and the fast neutron source 340, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 322.
  • the tool 306 is shown situated in a borehole 342, which may be cased or open, adjacent a formation 344 for which logging data is desired. Coolant is delivered and returns via a coolant umbilical conduits 345.
  • FIG. 3B another embodiment of a wire line downhole neutron logging tool apparatus, generally 350, is shown to include a wire line, cable, fiber optic cable or wire 352, an electronic power supply and communication cable 354, and a wire line tool system 356.
  • the wire line tool system 356 includes a housing 358.
  • the housing 358 includes a wire line attachment 360.
  • the housing 358 also includes two imaging subsystems 362a&b, two detection subsystems 364a&b, a fast neutron generation subsystem 366, and two-way communication subsystem 368a&b.
  • the housing 358 may also include two downhole analyzer subsystems 370a&b. Each of the detection subsystems 364a&b includes a detector 372a&b.
  • Each of the detectors 372a&b includes a gas chamber 374a&b, a top electric grid 376a&b, a bottom electric grid 378a&b, a voltage drift cage 380a&b, a bottom plate 382a&b, and a window/lens 384a&b.
  • the tool system 356 also includes mounts 386a&b for mounting the detectors 372a&b on support/spacers 388a&b.
  • the fast neutron generation subsystem 366 includes a fast neutron source 390 having a window 391, which opens and closes under the control of the control subsystem.
  • the tool 306 is shown situated in a borehole 392, which may be cased or open, adjacent a formation 394 for which logging data is desired.
  • the support/spacer 388a provides a space between the detectors 364a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 364a&b, while the support/spacer 388b provides a space between the detectors 364a&b and the fast neutron source 390, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 364a&B.
  • FIG. 4A an embodiment of a drilling and neutron logging tool apparatus, generally 400, is shown to include drill string 402, an electronic power supply and communication cable 404 extending along an outside 403 of the string 402, and a drilling and logging tool system 406.
  • the tool system 406 includes a housing 408.
  • the housing 408 includes a drill string coupler 410.
  • the housing 408 also includes two imaging subsystems 412a&b, two detection subsystems 414a&b, a fast neutron generation subsystem 416, and two-way communication subsystem 418a&b.
  • the housing 408 may also include two downhole analyzer subsystems 420a&b.
  • Each of the detection subsystems 414a&b includes a detector 422a&b.
  • Each of the detectors 422a&b includes a gas chamber 424a&b, a top electric grid 426a&b, a bottom electric grid 428a&b, a voltage drift cage 430a&b, a bottom plate 432a&b, and a window/lens 434a&b.
  • the tool system 406 also includes mounts 436a&b for mounting the detectors 422a&b on support/spacers 438a&b.
  • the fast neutron generation subsystem 416 includes a fast neutron source 440.
  • the tool 406 is shown situated in a borehole 442, which may be cased or open, adjacent a formation 444 for which logging data is desired.
  • the housing 408 also includes a drilling subsystem 446.
  • the drilling subsystem 446 includes a drill control unit 448 and a drill bit apparatus 450.
  • the support/spacer 438a provides a space between the detectors 414a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 414a&b, while the support/spacer 438b provides a space between the detectors 414a&b and the fast neutron source 440, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 414a&b.
  • FIG. 4B another embodiment of a wire line downhole neutron logging tool, generally 400, is shown to include drill string 402, an electronic power supply and communication cable 404 extending along an outside 403 of the string 402, a drilling and logging tool system 406.
  • the tool system 406 includes a housing 408.
  • the housing 408 includes a drill string coupler 410.
  • the housing 408 also includes two imaging subsystems 412a&b, two detection subsystems 414a&b, a fast neutron generation subsystem 416, and two-way communication subsystem 418a&b.
  • the housing 408 may also include two downhole analyzer subsystem 420a&b. Each of the detection subsystems 414a&b includes a detector 422a&b.
  • Each of the detectors 422a&b includes a gas chamber 424a&b, a top electric grid 426a&b, a bottom electric grid 428a&b, a voltage drift cage 430a&b, a bottom plate 432a&b, and a window/lens 434a&b.
  • the tool system 406 also includes mounts 436a&b for mounting the detectors 422a&b on support/spacers 438a&b.
  • the fast neutron generation subsystem 416 includes a fast neutron source 440.
  • the tool 406 is shown situated in a borehole 442 adjacent a formation 444 for which logging data is desired.
  • the housing 408 also includes a drilling subsystem 446.
  • the drilling subsystem 446 includes a drill control unit 448 and a drill bit apparatus 450.
  • the housing 408 also includes a gamma ray detection subsystem 452.
  • the gamma ray detection subsystem 452 includes two gamma ray detectors 454a&b and a gamma ray source 456 and two support/spacers 455a&b.
  • the support/spacer 438a provides a space between the detectors 414a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 414a&b, while the support/spacer 438b provides a space between the detectors 414a&b and the fast neutron source 440, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 414a&B.
  • the support/spacer 455a provides a space between the gamma ray detectors 454a&b by a distance to optimize or differentiate between the fast neutrons returning to the two gamma ray detectors 454a&b, while the support/spacer 455b provides a space between the gamma ray detectors 454a&b and the gamma ray source 456, where the space is a distance or gap that optimizes an incidence of returning gamma rays onto the gamma ray detector 454a&B.
  • All of the other embodiments described above may include a surface cooling subsystem and a downhole cooling subsystem, which may provide coolant to the electronic components of the other subsystems.
  • FIG. 5 an illustrative depiction of fast neutron detection is shown using a wire line neutron detection tool system 500 including a wire line attachment 502, a housing 504 and a first neutron detection subsystem 506 and second neutron detection subsystem 508.
  • the first neutron detection subsystem 506 includes detectors D11 and D12 and a fast neutron source N1
  • the second neutron detection subsystem 508 includes detectors D21 and D22 and a fast neutron source N2.
  • the system 500 is attached to a wire line, cable, fiber optic cable or wire 510 via the attachment 502 connected to or integral with the housing 504.
  • the wire line , cable, fiber optic cable or wire 510 also include a electronic power supply and communication component (not shown) for supply power to the detectors and other controllable components as well as providing control and data transmission functions.
  • Fast neutrons are emitted by the sources N1 and N2.
  • the fast neutrons from the sources N1 and N2 penetrate into the formation to a total penetration depths of d3 and d6, where the depths d3 and d6 may be the same or different depending on the nature of the neutron emitted by the sources N1 and N2, which may be the same or different type of sources.
  • the total penetration depths d3 and d6 give rise to two different types of formation and/or formation fluid responses.
  • first portions d1 and d4 of the total penetration depths d3 and d6 neutron are scattered, reflected, and/or refracted from a borehole surface and/or near surface of a borehole 512 as represented by the penetration depths d1 and d4.
  • second portions d2 and d5 of the total penetration depths d3 and d6 neutron are scattered, reflected, refracted, and/or absorbed and reemitted from formation solid, formation gasses, and/or formation liquids deeper in the formation in the second portions d2 and d5 of the total penetration depths d3 and d6.
  • the system 500 is lowered into the borehole 514 relative to a center line 514, where the borehole 514 extends from a surface assembly 516 of a ground surface 518 into a formation 520 to be logged. Because the system 500 includes two detection subsystems 506 and 508, two portions 522 and 524 of the formation 522 may be simultaneously logged.
  • Probes generally vary with bore hole diameter.
  • the Petroleum industry demonstrated that the shape of the hole matters when it is interrogated with gamma sources.
  • Various drilling techniques are used depending upon the rock type or lithography.
  • Percussion type drilling creates holes that are determined by the rock strain. Variation of grades of ores from place to place has been extensively studied.
  • the Matheron variogram for example, has become the basic tool of geostatistics of the natural variability of a region variable set such as are grade. It is defined as:
  • the hole size may vary from 150 mm to 400 mm at a depth typically of from 0.5 m to 5000 m.
  • the drill bit at this depth encounters all types of rock hardness and types as the drill punches deeper into the well.
  • the whole spectrum of rock types from sentiments to extremely hard rock deposits are encountered as well as hole full of various viscosities of fluids from water to drilling fluids.
  • the only constant is that the lithography varies from hole to hole.
  • the volume of the cylindrical shell of rock probed and then drilled is proportional to the energy of the energy source and the nature of the rock materials being penetrated.
  • the bulk sample penetrated by gamma radiation is calculated as:
  • t 1 ⁇ 2 is the thickness needed to reduce the transmission through a material with total linear gamma-ray coefficient m to the value of one half.
  • a typical percussion drill hole with the smallest diameter of a gas collection pipe with a radius of 5.8 cm (58 mm) (2.8") allows a radiation penetration of only 5 centimeters is sufficient to probe a volume approximately 2.5 times that of the corresponding core; for 15 cm penetration, the corresponding penetration ⁇ is a factor of 12 times or 6'.
  • For average rock penetration at 5 MeV is capable of probing 70 such core volumes with an equivalent type of rock. With dense materials such as haematite, core volumes probed in this size hole are greatly diminished. The actual depth of rock from which information can be gathered varies with the type of core log employed.
  • a fast neutron imager with a higher energy source that can penetrate further from the hole tells us more about the location of oil deposits and whether they are in gas or liquid form. This information must be interpreted from information about either the resulting characterization of the drilling fluids or the porosity level of the soil types permeated by water.
  • an embodiment of a directionally sensitive neutron detector is shown to include a gas chamber 602 having a gas chamber interior 604 filled with a gas mixture 606.
  • the gas mixture 606 is effective to interact with incident fast neutrons n and to generate scintillation light due to the interaction between the neutrons n and molecules in the gas mixture 606.
  • the gas mixture 606 is tunable via gas supply lines, gas delivery assemblies and gas sources shown in Figure 6B below.
  • the ability to tune the gas mixture composition permits on the fly optimization of gas composition, pressure, and/or temperature based on the type of neutrons n being detected.
  • the detector subsystem 600 also includes a detector assembly 608.
  • the detector assembly 608 includes a plurality of flattened conductive rings 610 separated by a plurality of ring insulation and resistor assemblies 612 including a ring insulator 612a and a ring resistor 612b.
  • the detector assembly 608 also includes a top grid 614 and a bottom grid 616.
  • the detector assembly 608 also includes a bottom plate assembly 618 supporting the bottom grid 616 via bottom plate insulators 620.
  • the detector assembly 608 is connected to the power supply subsystem 622 via an input wire 624 and an output wire 626.
  • the potential difference across between the grids 616 and 618 is controlled by the power supply subsystem 622 and the insulation disk and resistor assemblies 612 control a step wise change in the potential difference at each of the rings 610 as one traverse down the chamber 602 from the top grid 616 to the bottom grid 618.
  • This potential difference operates to permit the detector assembly 608 to react to incoming a neutron n generating electrons that are accelerated toward the bottom grid 618 generating light detected by a sensor subsystem 628.
  • the sensor subsystem 628 includes at least a CCD camera or a CMOS sensor 630, photomultiplier tubes 632 and a sensor window/lens assembly 634.
  • the camera 630 and the photomultiplier tubes 632 are used to detect the neutron n events recording the tracks, which is analyzed to generate neutron event data including neutron entry energy, neutron entry direction, and other neutron interaction data.
  • the sensor subsystem 628 is connected to the power supply subsystem 622 via an input wire 636 and an output wire 638.
  • the system 600 also includes a processing subsystem 640, which is connected to the power supply subsystem 622 via an input wire 642 and an output wire 644.
  • the processing subsystem 640 controls the charging of the detector assembly 608 and controls the capture and storage of images of the neutron gas interactions or neutron detected events detected by the sensor subsystem 628.
  • the processing subsystem 640 may also include software for performing preliminary analysis of neutron detected events.
  • the processing subsystem 640 is in two way communication with the detector assembly 608 via detector assembly communication pathway 646 and with the sensor subsystem 628 via sensor subsystem communication pathway 648.
  • the system 600 also includes a coolant subsystem 650 having a coolant delivery conduit 652 and a return coolant conduit 654.
  • the subsystem 650 is in thermal contact with the photomultiplier tubes 632 and the camera or sensor 630.
  • the coolant cools the subsystem 650, which in turn cools the photomultiplier tubes 632 and the camera or sensor 630.
  • a schematic representation of an embodiment of the gas chamber 602 include a 4He valve 660, a 4He delivery line 662, a 4He source 664 and a 4He flow controller 666.
  • the gas chamber 602 include a CF 4 valve 668, a CF 4 delivery line 670, a CF 4 source 672 and a CF 4 flow controller 674.
  • the gas chamber 602 may also include a 3He valve 676, a 3He delivery line 678, a 3He source 680 and a 3He flow controller 682.
  • the 4He valve 650, the 4He flow controller 656, CF 4 valve 658, and the CF 4 flow controller 664 are controlled by the processing subsystem 640. If the gas mixture 606 also includes 3He, then the 3He valve 666 and the 3He flow controller 672 are also controlled by the processing subsystem 640.
  • FIG 7 represents a side section view of a schematic representation of the detector system 700.
  • the detector chamber 600 encloses a volume oriented in the z direction per a Z axis, which defines a generally axial direction of the detector system 700.
  • the detector system 700 may be generally of a cylindrical shape and thus has a circular cross section orthogonal to the Z axis.
  • the detector system 700 includes a "field cage" having a plurality of stacked, spaced-apart conductive rings 702 orthogonal to the Z axis, along with an upper wire mesh or upper grid 704 at the top of a relatively large drift region 706. At the lower end is a lower wire mesh or lower grid 708 and a closely spaced conductive plate 710, which together define a much smaller amplification region 712. Voltages are applied as described below to establish a first, relatively low electric field in the drift region 706 and a second, relatively high electric field in the amplification region 712.
  • An imaging system 714 which in the illustrated embodiment includes a lens 716 as well as a light sensitive component 718 such as charge-coupled device (CCD) imaging unit, a cooled CCD imaging unit, a CMOS imaging unit, etc., located outside the upper end of the detector chamber 700.
  • the detector may also include photomultiplier tubes (PMTs) 720 also at the upper end, two of which are shown in Figure 7. The function of the PMTs 720 is described below.
  • the field in the drift region 706 is established by the combination of a ground potential on the lower grid 708 and a negative potential V drift applied to the upper grid 704 and the uppermost ring 702t.
  • a series of resistors 722 serve as a voltage divider network to distribute the voltage V drift across the rings 702.
  • the voltage V drift is -2500 volts
  • the resistors 722 provide generally equally spaced voltages in the range between -2500 and 0 to the rings 702.
  • the sequence of ring voltages progressing downwards is -2500, -2000, -1500, -1000, -500 and 0.
  • a larger number of rings e.g., 20 to 30 or more
  • the field in the amplification region 712 is established by the combination of the ground potential on the lower grid 708 and a high positive potential Vamp applied to the plate 710.
  • the voltage Vamp is +620 volts and the spacing between the lower grid 708 and plate 710 is 0.5 millimeters.
  • the sensor subsystem 714 together with a processing subsystem (not shown here, but shown in other figures) generate two- dimensional (2D) and three-dimensional (3D) images of these scintillation tracks and process the images to identify those tracks generated by neutrons of interest, differentiated from other types of tracks and from other artifacts that may be created in operation.
  • the ionization track of the recoiling He may have a Z-direction component, which is not reflected in the path of scintillation occurring in the plane-like amplification region 712.
  • the two-dimensional information from the scintillation tracks alone may be sufficient for identifying the direction of incident neutrons.
  • the PMTs 720 may be used for this purpose.
  • the PMTs 720 are fast-response devices that provide an electrical output pulse for each scintillation, with the pulse duration being equal to the duration of the scintillation.
  • the duration of a pulse from a PMT 720 is directly proportional to the Z component of the ionization track whose scintillation light caused the pulse.
  • the processing subsystem can include the Z component in its estimation of neutron direction. As described in more detail below, the estimation of direction is also based on the shape of the scintillation tracks.
  • the system 700 also may also include coolant units 724a-c.
  • Each coolant unit 724a-c includes a coolant delivery conduits 726 and a coolant return conduit 728.
  • the coolant units 724a-c are in thermal contact with the photomultiplier tubes 720 and the imaging unit 718, where the coolant cools the photomultiplier tubes 720 and the imaging unit 718 electronic.
  • Embodiments of this invention relate to imaging methods and systems that include a sensor or tool subsystem, where the systems are adapted to image, detect, diagnose, and/or identify properties of a borehole penetrating subterranean formations and/or zones thereof.
  • the systems may be used in both open or cased boreholes.
  • the systems and methods are configured to: 1) evaluate a formation or a zone thereof; 2) determine wellbore integrity; and 3) map fluid movement during production/injection.
  • the sensor or tool subsystems are attached on a wireline having a power cable that provides power to the sensor or tool subsystem and a data cable that enables bidirectional communication between the sensor or tool subsystem and a surface control and analyzer subsystem.
  • the sensor or tool subsystems are attached in a slickline and dropped or lowered into a borehole. In other embodiments, the sensor or tool subsystems are incorporated into on a drill string so that data may be collected while drilling. In certain embodiments, the sensor or tool subsystems collect formation data and then send the data to the surface for the analysis. In other embodiments, the sensor or tool subsystems collect and pre- process or analyze formation data and then send the pre-processed and analyzed data to the surface for further analysis. In other embodiments, the data is retrieved from the sensor or tool subsystems after the sensor or tool subsystems are pulled from the borehole as the sensor or tool subsystem includes memory sufficient to store the data. The collected and analyzed data is used by operator personnel to: (1) adjust the course of drilling, (2) identify formation or zone properties, and/or (3) identify formation or zone fluid properties (types and amounts of fluids).
  • the sensor or tool subsystems include at least one fast neutron source and at least one fast neutron detector.
  • the neutron detectors take advantage of the scientific principals of neutron emission spectrometry.
  • the neutron generator(s) or source(s) is(are) positioned on the sensor or tool subsystems to irradiate the formation with fast neutrons, while the neutron detector(s) is(are) positioned on the sensor or tool subsystems to detect fast neutrons incident thereon.
  • a certain portion of the fast neutrons interact with the formation materials (solids, liquids, and/or gases) and return towards the detector(s), and a portion of these returning neutrons enter the neutron detector(s).
  • each detector includes a gas mixture designed to interact with returning fast neutrons generating electrons, which drift through an electron drift chamber. These electrons generate light focused onto a dark field of an imagining unit of each detector.
  • each imagining unit also includes a prism that separates the generated light into its spectral components. The spectral components are focused onto a dark field with colored lines that correspond to the electron transitions resulting in the light emission. Given the color or frequency of light emitted, software is used to analyze the energetics of the collisions. The electrical discharges create images called tracks and are captures or collected by the detector(s) and analyzed by the software. The images or tracks are then sorted, analyzed and correlated with solids, liquids, and/or gasses, which correspond to energies of the detected neutrons that include information about the fast neutron-formation component interactions.
  • the detectors in the sensor or tool subsystems are designed to improve the quality of available information about formations and any gasses or liquid in the formations providing enhanced information during drilling operations.
  • the information may be gathered during down times or in real time or near real time while drilling.
  • the exact information collected by the sensor or tool subsystems will depend on the information needed and on the configuration and types and numbers of detectors and sensors present on a particular sensor or tool subsystem.
  • the sensor or tool subsystems are generally controlled by a control subsystem including processing units.
  • the control subsystems may include a local (tool based) processing unit, a remote (surface based) processing unit, or a combination of local and remote processing units. These processing units are adapted to control the operation of hardware and software components in the sensor or tool subsystems.
  • the local or tool-based processing unit may simply collect and store the images. In other embodiments, the local or tool-based processing unit may collect, store and transmit the images to a remote processing units for data analysis. In other embodiments, the tool-based and remote processing units are used in data analysis.
  • the hardware components of the sensor or tool subsystems include at least one conventional fast neutron generator or source, at least one neutron detector of this invention, and software components that detect, capture and analyze the detected and captured data to generate formation information during drilling operations and/or while drilling.
  • the data collected by the sensor or tool subsystems corresponds to photographic and/or spectroscopic data associated with elastic and/or inelastic collisions between fast neutrons emitted by the neutron source and the formation or formation components that have a direction toward the sensor or tool subsystems (returning neutrons) in real time or near real time. These collisions are interpreted producing specific data concerning the formation and the formation components.
  • the detectors in the sensor or tool subsystems capture images, tracks and/or events corresponding to collisions between returning fast neutrons and a gas mixture in the detector before the neutrons thermalize.
  • the returning fast neutrons comprise reflected, refracted, scattered, or any other fast neutron that traveling back towards the sensor or tool subsystem after interacting with the formation components (gases, liquids, and/or solids).
  • the sensor subsystems and analysis subsystems are implemented to exclude captured collisions that do not meet a threshold energy value, e.g., neutrons that have thermalized to the extent that insufficient information is readily ascertained.
  • the threshold energy excludes neutron having energies below about 100 keV. In other embodiments, the threshold energy excludes neutron having energies below about 0.5 MeV. In other embodiments, the threshold energy excludes neutron having energies below about 1 MeV.
  • An example of neutron energy states in electron volts (eV) after generation and collision may be summarized as follows.
  • Initial fast neutrons having energies of about 4.5 MeV produced by a neutron source irradiate a formation or formation zone.
  • a portion of these neutrons are elastically and/or inelastically scattered in a direction back towards the sensor or tool subsystems, where a portion of these neutrons enter the detector.
  • the scattered neutrons have energies between about 2.5 MeV and about 100 keV, and are commonly referred to a epithermal neutrons– neutrons having an energy $100 keV.
  • these ethermal neutrons are not detected soon after production, they thermalize producing thermal neutrons having energies between about 100 keV and about 10 eV, but below 100 keV.
  • the detectors are designed to detect neutron having an energy between about 4.5 MeV and greater than about 100 keV, while rejecting neutron energies less than about 100 keV.
  • the sensor or tool subsystems or analyzing subsystems detect and create three dimensional images or tracks without regard to the geometry of the borehole. From experiments, it can be shown that the sensor subsystems or tools creates a two or three dimensional image generally shaped as a cylinder with a resolution up to thirty meters from the center line of a bore hole in an x, y or z direction. Generally, most of the current indirect measurement systems used on wirelines down hole have a resolution of no more than up to 2 feet from the centerline of the bore hole.
  • the present sensor or tool subsystems can be deployed in one of two embodiments; 1) either in a stand-alone mode or 2) operated on a wire line over a fiber optic cable creating a networked environment.
  • the system operation, retrieval speed and recovery of the track images created by the spectrometer are dependent upon the form of its preferred embodiment.
  • the imager’s power is self-contained and its operating performance is limited by the size of its battery power.
  • the imaging system capturing the collisions is self-contained and the imaging system module is subsequently recovered when the imager is pulled up the drill string and removed from out of the ground.
  • the second embodiment enables real-time image capture by the use of a computer system and display console tethered up on a drilling platform linked to the imager over a combination fiber optic/power cable that is connected to a power source out of the bore hole.
  • This second embodiment enables the driller to image while drilling with an operational delay proportional to the length of the data cable between the image detector below ground and the operating console/computer on the platform.
  • the computer system functions operating the sensor or tool subsystems of this invention contain an industry standard operating system, software imaging interpretative applications, an image compiler, and removable data storage. It is designed to be self-contained and requiring only periodic scheduled maintenance.
  • the data from the imager is formatted to be used on standard interpretative software packages for later evaluation and use by the drillers and geologists.
  • a display device/monitor is configured with the computer for use as an interface to a human operator. An operator familiar with a basic personal computer can operate the display component and computer system associated with the sensor or tool subsystems of this invention. Specific graphical visual information is provided to the user so that the geologist or an untrained drilling operator does not need to undergo specialized training to interpret the images created by the present imaging tool.
  • the computer system provides each of the operational functions for system initialization, self-test and tool operation.
  • the system is ruggedized for use in an outdoor environment.
  • the computer system is networked; in this network configuration, it can be configured for remote communications operation with a module containing a data link for data transmission, tool control and remote data analysis.
  • the Computer System has a hierarchical set of resources that provides all of the operating controls of the sensor or tool subsystems. This includes system initialization, self-test, data collection and analysis modules. The methods of operation of the system and the processing subsystem are illustrated in Figures 8, 9A-D and 10A-B and the accompanying text.
  • a software package of this invention resides on the computer system.
  • the package has a generic stand-alone operating system and is designed to manage the system's hardware tool resources.
  • the software applications are specifically designed to interpret, capture, display and store the information generated from the present neutron imaging component during its downhole operation. This information is put into a Microsoft ExcelTM 2010 spreadsheet format for manipulation and subsequent analysis.
  • the algorithms coded for interpretation of the data are described herein.
  • Three hardware components are required for imaging to take place.1)
  • the neutron source must be "on”.
  • the imaging tool must be correlated to the neutron source. 2)
  • the tool must be initialized to the information control system.3)
  • the computer system that controls the tool must be initialized to the tool and the neutron source for creation of the imaging data base.
  • the software components used by the system document the interaction between the neutron source, the geological (rock) formation and other and the second module containing the sensor or tool subsystems of this invention.
  • the imaging steps create a data base of information about the rock formation in the following order:
  • Initialization Fast neutrons are released from the first module near the well bore surface and the tool located in the second module goes through a calibration routine. Handshaking occurs between the digital computer and the tool during the initialization step.
  • Data Base A data base including an architecture resident on the computer component of the systems.
  • the database stores system operating parameters and captured track data representing the collisions that have occurred between the geological formation and the fast neutrons released by the neutron source.
  • Image Capture The returning fast neutrons, moderated by these collisions with formation solids, liquids, and/or gases, are captured as "tracks" or images created when the returning fast neutrons strike or collides with atoms of the penning gas in the gas chamber of the detectors in the downhole tool.
  • An imaging unit e.g., a charge coupled device (CCD)
  • CCD charge coupled device
  • the images or tracks include neutron event data including energetic data, directional data, time data, location indexing data, etc. associated with each detected collision between atoms of the penning gas and the returning fast neutrons.
  • the event data are then correlated or interpreted using a CIE Chromaticity index using software residing in the analyzing subsystem of this invention and collected and stored in an image data base.
  • the event data are stored sequentially, but the event data may also be stored randomly indexed so that sequential data analysis may be performed.
  • the database contains continuously captured event data comprising tracks or images including color/hue/intensity data and directional data.
  • the continuously captured data may be continuously correlated using analysis software associated with the database that compares the capture event data with event data associated with known data either from know geological formations or from simulated data of different solids, liquids, and/or gases. Over time, the system "learns" from collected and analyzed event data relating to whole sample geological structures based on the analysis of the images or tracks created by the returning neutron collision data and improves and/or refines event data in the database so the interpretation can be improved.
  • the capture event data is correlated using the database, it is then converted into output data, such as an Microsoft ExcelTM spread sheet, that contains both the interpreted event data and an identifier containing the location from where the event data was captured.
  • the output data may be in the form of a map of the borehole showing the type of solids, liquids and/or gas collected during the logging operation. 7.
  • the captured event data about the formation is recorded and converted into graphic information that is then transmitted out of the hole and up to the driller's user interface.
  • the driller may then adjust the drilling sweet spot based on the images coming from the graphical user interface coming continually from the updated imaging or track data base.
  • the newly captured and subsequently interpreted event data is digitally linked with other data captured during the drilling operation from other tools that is specific to the current formation being drilled and the resulting data is transmitted over a communications link to a remote location for real-time geological interpretation and analysis.
  • the color/hue/intensity event data are color coded which represents a proportional relationship between the strength of the interaction between the initial fast neutrons and the geological elements identified and continuously measured the borehole during logging operation or during logging while drilling operations. Color decoding used to decode the data represented by the track images is described more fully below in Figures 11-16.
  • the detectors of the systems of this invention are analytical spectrometers that capture fast neutron-penning gas collision images or tracks that include neutron event data that are passed to the analysis subsystem where software analyzes and interprets the event data producing formation solid, liquid, and/or gas properties and/or characteristics.
  • the systems of this invention are designed to be used in open boreholes and/or cased boreholes during drilling, during wire line operations, or during any other operation where a tools in capable of being inserted down hole.
  • the tools may be dropped downhole on a wire line or may be a tool in the drill string.
  • the diameter of an open borehole or the drill pipe is between 2 and 9 inches.
  • the minimum diameter of the tools of this invention are about 1and 11/16 inches so as to clear the inside of a 2 inch diameter drill pipe or borehole.
  • the maximum diameter of the tool of this invention are about 8.5 inches so that the tool passes through a drill pipe or borehole having a 9" diameter.
  • the tools of this invention are designed to have an appropriate diameter to fit down an borehole or drill string pipe, and not become stuck in the open borehole or the drill pipe. Its design takes into account the use of modern fishing tools used to remove stuck tools. In embodiments where the tool is part of the drill string, then the tools should have a diameter sufficient to allow the tool to pass through borehole as it is being formed.
  • the tools of this invention include two hardware components, each with a unique set of features situated to work in a unique set of circumstances intended for use in oil and/or gas exploration applications: A) a neutron generating subsystem including at least one commercially available fast neutron generator or source commonly used in the oil and gas drilling operations, and B) a detection/imaging subsystem that detects and captures data concerning collisions between returning fast neutrons and atoms of the penning gas in the detectors of the detection/imaging subsystem, where the returning fast neutrons are generated by initial fast neutron collisions with formation solids, liquids, and/or gases.
  • Each drilling environment has unique operational performance criteria and operating characteristics.
  • the tools of this invention are initialized by a hand shaking routine between a control subsystem of this invention and tool based neutron source such as an americium source embedded in the neutron generating subsystem.
  • the analyzing subsystem of this invention includes software for implementing computer based methods designed to receive neutron-penning gas collision event data and interpreter the data to determine formation solid, liquid and/or gas properties and/or characteristics as the event data corresponds to energetics and directional data for elastic or inelastic collisions between formation atoms and initial fast neutrons emitted by neutron source used in the oil and gas industry.
  • the initial fast neutrons may be generated by a 241Am/9Be neutron source.
  • the source has a known starting energy level.
  • the detector measures returning fast neutrons (neutrons scattered, reflected, refracted or otherwise having their direction directed back toward the tools of the systems of this invention through interactions with formation solids, liquids, and/or gases.
  • the energetics of the returning fast neutrons are determined from the track and/or image data captured by the detection/imagining subsystem of this invention.
  • the returning fast neutrons such as fast neutrons that have been elastically scattered off formation solids, liquids, and/or gases, entering into the detector(s) of the tools through a detector window(s) and interact with the atoms of the gas mixture(s) in the gas chamber(s), where the gas mixtures include a penning gas and a quenching gas.
  • the initial energy level of fast neutrons created by the neutron source is about 4.5 MeV.
  • the energies of the returning fast neutrons that have collided with the formation solids, liquids, and/or gases generally have energies range between about 4.5 MeV and about 100 keV; in certain embodiments, the returning fast neutrons have energies range between about 4.5 MeV and about 1 MeV; and in certain embodiments, the returning fast neutrons have energies range between about 4.5 MeV and about 2.25 MeV.
  • the penning gas mixture is a mixture of a noble gas referred to as a penning gas such as 4He or a mixture of 3He and 4He and a quenching gas such as a freon or a mixture of freons, especially CF 4 or mixtures of CF 4 and other low molecular weight perfluorocarbons.
  • the gas mixtures are held at a pressure of about 1 atmosphere in its normal state.
  • the "normal state” is defined as a gas mixture at a temperature of about 20°C.
  • the pressure of the gas mixture in the detector increases as the tools are exposed to higher temperatures, when the tools are subjected to downhole conditions.
  • the energies of the returning fast neutrons are converted into photonic energy via the collisions between the returning fast neutrons and atoms of the penning gas in the gas mixture contained in the detector chamber(s) of the detectors of this invention.
  • the penning gas a noble gas such as 4He, has a large crosssectional surface area with fast neutrons.
  • the collisions are quenched by the quenching gas generating electrons, which are accelerated down the drift region of the gas chamber causing an electron cascade that is then converted into scintillation light.
  • the scintillation light is captured a images or tracks as a photonic image stream.
  • the images or tracks are produced as energy from the collision is returned to the detector through a precise angle and distance between the neutron generating source and the spectrometer through its imaging window.
  • the energy from the collisions is converted into photonic energy as it drifts a precise distance through the voltage drift region of the gas chamber.
  • the precise direction of the collisions and the resulting energetices of the collision events are continually captured.
  • These collisions are measured by the photonic energy output and are captured using a specially designed camera system with a specially designed CMOS Charge Coupled Device (CMOS/CCD) and the event data (color/hue/intensity data and directional data) are subsequently analyzed with the imaging software on the computer system.
  • CMOS/CCD CMOS Charge Coupled Device
  • the resulting event data are either recorded on the imager solid state computer storage component in string line mode or transmitted up the data cable to the operator at the surface.
  • the operation comprises a continuous stream of images randomly or sequentially stored on portable or fixed mass storage device, such as an internal hard drive, an external portable drive, a USB thumb drive, or any other fixed or portable mass storage device. All event data are periodically calibrated with a precise test sequence from a known location in the formation.
  • the images are continuously distributed over the remotely controlled fiber optic data/power cable. This design eliminates the problem associated with the complexity from the degradation of epithermal and thermal neutron capture.
  • the spectrometer only detects the energy level from the elastic collisions between the formation and the fast neutrons generated by the attached neutron source in proximity to the detector.
  • the 241Am/9Be neutron source initially generates 4 ⁇ 107 neutrons per second. These neutrons are channeled toward the formation at a 90° angle and returned at a 39° angle to the detection window. Depending upon the lithography, some neutrons are immediately absorbed. Some neutrons are partially scattered. Other neutrons are deflected.
  • the detector imaging window is constructed with fluorine doped tin oxide with a sensitivity of from 7 ⁇ square to 3 ⁇ square at 80% transmittance. Sensitivity is a function of the size of the aperture, the columnation, and the grating in the camera component. The neutron energy that returns to the detector is analyzed through the use of the imaging application software. The strength of the deflected neutrons is used to create a picture of the materials in the formation either in the open borehole or through the borehole pipe.
  • the detection means measures the nondestructive energy level of the neutrons measured from their deflection off the formation surface to the detector as compared with those generated from a fixed distance from the neutron source.
  • the deflected neutrons are deflected back towards the detector and are captured by entering a window on the detector that is situated at a geometrically determined distance from the neutron generating source.
  • the strength of the deflected energy caused from the collision between the fast neutrons and the formation is a function of the composition of the geological structure, the porosity of the formation and the amount of liquid and gas hydrocarbons.
  • the expected range of the permeabilities and hydraulic conductivity of the energy source into various rock types determines the distance that the fast neutrons either collide or are absorbed or otherwise penetrated into the formation.
  • a key feature of this software package of this invention is its ability to both simultaneously capture and subsequently graphically display the energies of collisions between the initial fast neutrons generated by the fast neutron source and formation components that return toward the sensor or tool subsystems and enter the detector. These collisions may be displayed in one of two embodiments.
  • the collision data is captured on a computer system storage medium (a fast drive) for further review and analysis, when the instrument is pulled from the hole.
  • the images are sequentially captured as the wire line lowers the sensor or tool subsystems in the well. As the cable releases the sensor or tool subsystems attached over the wireline down the bore hole the imaging takes place, while drilling or other measurements are taking place.
  • This first embodiment of the invention relies on so-called “slickline data", because it is not sent to the surface until the test is run and the sensor or tool subsystem is retrieved from the bore hole. It requires a minimal specific battery powered system and the spectrometer is a self-contained unit mode.
  • the sensor or tool subsystem when configured to be tethered on the drill string using a bi-directional fiber optic energy and data cable tethered over the drill string into the bore hole from a remote control platform with the imaging information can be provided in real time subject to the delay proportional to the length of the fiber optic cable and the depth of the instrument in the bore hole.
  • the real time capture of the information is subject to the length of the cable between the operator console and the sensor or tool subsystem. Theoretically, if the sensor or tool subsystem is at the bottom of the bore hole at 10,000 feet, the delay of the signal from the platform operator is proportional to the distance and the signal travels 20,000 feet before the operator receives a response back from the sensor or tool subsystem.
  • the image analysis software component of this invention interfaces to the active area of the CMOS/CCD imaging camera component in the detector with the computer component of this invention and performs the following five activities:
  • the image is displayed in color as a series of pixels that reflect the energy captured by the CMOS/CCD component from the collision.
  • the pixel size is optimized to achieve maximum resolution. They are a function of the size of the imager in the camera component and are in a range of from 8 ⁇ to 14 ⁇ .
  • the pixel density drives the optical performance specification.
  • CTE charge transfer efficiency
  • CCD Charge Coupled Device
  • the image analysis software is adapted to the unique diameter of the spectrometer imager component and is specific to the geometry of the well bore hole and whether the bore hole is open or cased.
  • the software algorithms work on the principal of the identification of the energy level of the resulting scattering elastic collisions between the down hole materials and the fast neutrons from a specifically designed 241Am/9Be commercial chemical nuclear source. Let us consider source in a scattering medium which emit neutrons with an energy E or with an energy distribution (E). These neutrons exchange kinetic energy with the atoms of the scattering substance through elastic collisions. This exchange is captured before the neutrons ethermalize or subsequently thermalize. If the neutrons are emitted with energies higher than the kinetic energy of the thermal motion of the scattering atoms, they lose energy in successive collisions until they are in equilibrium with the thermal motion of their surroundings. The inventive step is to capture the energy of the neutron collisions before ethermal and subsequent thermal equilibrium is reached.
  • Variable List (*Measuring the time, space, and energy of elastically colliding fast neutrons to determine the com osition of matter in a drill hole :
  • n(r, ⁇ ,E)dVd ⁇ dE the number of neutrons in this volume element whose flight direction, characterized by the unit vector ⁇ , lies in the differential solid angle d ⁇ around ⁇ and whose kinetic energy lies between E and E + n(r, ⁇ ,E) (cm-3steradian-1ev-1) is thus the number per cm3; i.e., the density of the neutrons with energies unit interval at E and flight directions in a unit solid angle around ⁇ . Specifying the differential density, which is time dependent, is sufficient to describe the neutron field.
  • the total number of neutrons with a given flight direction is obtained by integration over all energies as:
  • n(r,W) is called the vector density and replaces n(r,E) when we are dealing with a neutron field of constant energy. If we now integrate over all flight directions as well, we obtain the total number of neutrons in a volume element dV at the point r.
  • n(r) is the density of the neutrons at point r.
  • the flux of neutrons is called the flux of neutrons.
  • the flux ⁇ (cm-2sec-1) is the datum most frequently used for describing neutron fields, and for this reason it is important to make its physical significance clear.
  • F can be represented as a function of only one angle h that is measured from a distributed axis with respect to which the field is considered to be rotationally symmetric.
  • F(r, ⁇ ) in Legendre polynomials we can always expect the quantity F(r, ⁇ ) in Legendre polynomials as a rule with considerable advantage insofar as the mathematical treatment of the problem is concerned as:
  • the first four Legendre polynomials are:
  • the second expansion coefficient also has physical significance. In order to see this, let us introduce an important new quantity, the current density J in the direction of the distribution axis. The magnitude of this vector is the net number of neutrons which penetrate a 1 cm2 surface perpendicular to the distribution axis per second.
  • the space and time behavior of a neutron field may be described by setting up a "neutron balance".
  • the number of neutrons n(r, ⁇ ,E)dVd ⁇ dE in a volume element dV with flight directions in the solid angle d ⁇ and energies in the interval dE may change for the following reasons:
  • This integro-differential equation in seven variables is called the transport equation or the Boltzmann equation. Together with appropriate boundary conditions, it determines the vector flux arising from the given source distribution. The most important boundary condition occurs at:
  • Eq. (10) can be simplified in some important special cases including the time and energy independent cases.
  • the transport equation takes the form:
  • the integration extends to infinity if the scattering medium is infinite; in a finite medium, integrate to the value of Rmax at which the straight line r-R ⁇ reaches the surface.
  • Eq.16 can be derived directly from Eq.13.
  • an inventive aspect of the present invention is the importance in knowing the initial starting energy of the fast neutrons and to channel only those neutrons that are focused on the formation and calculate only those that are elastically scattering anisotropically. Conversely, if the neutrons scatter both elastically and inelastically, a complex calculation including the time, space, and independent cases require integration over all of the angles. Such a calculation is possible but difficult to calculate quickly impacting the speed of the measurement.
  • the Legendre polynomial P l (cosh) expresses the measurement of the angle of the anisotropically scattered fast neutron.
  • the speed for capturing the collision is also critical to its accurate measurement.
  • the deflected energy of the collision is directly captured by the gas in the detector. If we expand the vector flux F in Legendre polynomials and break the expansion off after the second term, we set:
  • Eq.22 is the continuity condition which states that in one cm3 of a stationary neutron field the losses through leakage and absorption are equal to the number of neutrons provided by the source (S). This relation is independent of the special approximation (Eq. 9); this is physically obvious and can be easily proven formally if one notes that if additional terms of the expression for F are kept they drop out in the integration over ⁇ . From Eq.23 one obtains, via Fick's Law of diffusion;
  • the current density is proportional to the flux gradient.
  • the constant of proportionality D(cm) is called the diffusion coefficient; if the trans ort cross-section:
  • the diffusion length is measured by:
  • the detection system of this invention includes at least one detector and at least one imager.
  • the detector converts returning neutrons into light energy through neutron-gas collision producing electrons, which drift through a voltage drift zone producing light.
  • the imager is a spectroscope that captures images the light produced by these neutron-gas collisions in the detector.
  • the light generated in the detector corresponds to the energetics of returning fast neutrons after interacting with downhole materials including formation solids, liquids, and/or gases during exploration and production.
  • the imager measures light of varying wavelengths or frequencies corresponding to the energetics of the returning fast neutrons.
  • Collisions between fast neutrons and particles comprising varying states of matter are used to create energy measurements from which a picture of the formation characteristics in the vicinity of the bore hole during oil and gas drilling is derived.
  • Each particle has its own characteristic form or wavelength from which energy measurements are subsequently calculated and compared with data cumulatively generated in a data base.
  • the features of the detected images are correlated by a set of algorithms based on color, hue, and saturation based on a color tree system, which has 10 basic hues, each of the hues having 10 gradations, developed by Albert H. Munsell. This system is the official system for evaluating soils in the United States. Chroma scales represent different wavelengths depending upon the hue and gradation.
  • tristimulus values of a spectrum components X, Y, and Z are found by multiplying the xG, Gy and zG curve times of the spectrum in question, a detected image event. They are compared using a chromaticity diagram constructed according to the following formula defining the color coordinates x, y, and z as follows:
  • the formula provides that if two coordinates are given, the third is automatically determined.
  • the International Commission on Illumination (CIE) chromaticity or tristimulus diagram shows colors determined by CIE graphs and equations working on formulas not on color samples. The color samples are used to derive the subsequent formulas.
  • An additive mixture of two colors is represented by a point on a line connecting the points corresponding to the two colors.
  • the system includes a digital software platform operating on a high speed digital image capture and calculating engine, where image data is captured, shared, and interpreted by various users simultaneously in "real time”– delayed only by the time lapse between fast neutron return, detection and imaging.
  • the image data interpretation may be simultaneously retransmitted so that analysis of the data may occur locally or over a remote communications link in real-time as the data is being generated.
  • Drillers, service company personnel and geophysicists may all collaborate and have access to the same data at the same time anywhere in the world. This is meant to make the exploration process more efficient and effective especially in complex geophysical environments.
  • Fast neutrons of a known energy distribution are generated in a neutron source, initial fast neutrons. These fast neutron sources have long (more than 400 year) half-lives so the number of neutrons generated over a proscribed period of time is very stable.
  • the initial neutrons are focused mechanically by the construction of the tool toward the formation downhole using the detection apparatus.
  • a radiation hardened image sensor component is positioned inside the detector a fixed distance from the neutron source on a wire line.
  • the imager contains a shutter that opens and closes capturing the neutrons that are reflected back to a detector after their collision with the formation elements. These elements may take the form of solids, liquids or gasses. Depending on their type, the energy returned from the collision may be characterized and stored for further comparison in a data base.
  • the data is converted into a histogram used to illustrate the energy from the collision between the Penning gas with various types of rock structures, compositions and states of matter downhole. These histograms are represented by Gaussian distributions because their theoretical properties can be used to approximate a large number of practical energy distributions (discussion taken from Trussell and Vrbel Fundamentals of Digital Imaging).
  • a stochastic model of imaging is used to characterize a class of random images. The basis for it is a set of instructions that define how the class of images is generated. These instructions are reduced to a set of proprietary imaging algorithms written for this purpose.
  • Gaussian or normal probability densities are:
  • ⁇ is the mean and a is the standard deviation of the distribution
  • results may also be exponential: or Laplacian:
  • the prediction error is orthogonal to the data on which the prediction is based.
  • the set of indices needed for the correlation function is usually larger than that of the Auto Regeneration coefficient.
  • the symmetry of the autocorrelation can be used to reduce the number of distinct values.
  • the correlations generated by the model may not match the correlations used to generate the model.
  • the Auto Regeneration model has the same advantage in 2D as it does in 1D in that it is possible to obtain improved separation of frequency components over the Fourier transform based methods.
  • (k,l) are the prediction coefficients.
  • S 1 is a subset of the indices in a two dimensional lattice that defines the prediction region and (m,n) is the prediction error.
  • (m,n) is the white noise input with variance â2.
  • the imaging processing used in this application is based on Bayer color filtering methodologies. For additional information, the reader is directed to US3971065, US20070145273, US20070024879, and US20050231618. The methodology is brief recounted below.
  • the color filter array treats each channel separately and computes the interpolations as a reconstruction. Using spline interpolation on all three channels of a Bayer array results in good color reproduction of smoothly varying areas, but extreme color artifacts in regions of high spatial activity like a picket fence as the distance from the camera increases. The three color channels are significantly correlated.
  • the green channel of a color filter array (CFA) which approximates the CIE luminance efficiency function, provides the main information that is used to determine the presence and orientation of edges. The presence of an edge is indicated by the significant differences in the local values. To obtain good resolution, the neighborhood that is used to detect an edge must be relatively small.
  • demosaicking methods use a minimal 3 ⁇ 3 pixel neighborhood to estimate edge properties. Having estimated the presence and direction of a local edge, the information used to interpolate the green values in adjacent pixels, where only a red or blue measurement exists. This will give a full resolution image in the green or luminance channel.
  • the data may be used to determine how to interpolate the other channels.
  • the interpolation may operate directly on the red (R) and blue (B) channels or one of the color difference channels, because the R - G and B - G vales are available after the interpolation of the green channel. Correlation between the color channels is used in a multi-step- process.
  • Most demosaicking algorithms use an interpolation scheme that does not alter the original data.
  • the interpolation scheme uses the frequency domain allows the software algorithm to exploit freely the high and low pass nature of various features in the image. Hyperspectral imaging outside the visible range may be used, where the primary application is detection and classification of objects and terrain features.
  • the bin widths of the samples of N should be large enough to show sufficient detail and be consistent with the quantization of the signal values. For most images the values are between 1 and 255.
  • Using simple algorithms such as setting the bin width to the range of the signal divided by a fixed number of bins can yield an error.
  • the appearance of nearly periodic zeros in a histogram is an indication that the original signal is quantized and the bin width chosen is not well matched with that quantization.
  • a stochastic process is an indexed set of random variables.
  • the index set can be continuous or discrete.
  • An example of a discrete stochastic process is the sequential values of different types of materials found in a bore hole.
  • each pair (m,n) identifies a random variable.
  • the stochastic process can be indexed by a continuous variable as in the case of the relationship of fast neutron radiation as a function of spatial location.
  • the usual definitions of mean and variance may be used for stochastic processes. However, it is important to realize that those statistics are defined for each index, that is the mean index n1 is not necessarily the same as the mean at index n2.
  • the mean of an stochastic process, E[X(n)] is a deterministic function of n. Likewise the variance is a deterministic function of n.
  • the architecture of the computer and imaging system is a massively parallel array meeting our pattern recognition requirements.
  • FPGA's and custom logic can be used to take advantage of parallel processing.
  • STE's state transition elements
  • An expression is matched to a set of STE's and at least one terminal event that allows the host computer to recognize an imaging event and the chain that triggered it.
  • An Automata Processor hosts multiple expressions which are evaluated in parallel.
  • Each STE has 256 bits of information associated with it.
  • An STE matches a single pixel stream that will have one bit out of 256 to process many bit streams such as in a continuously imaging chip.
  • An eight bit symbol accesses a 256 but array per STE.
  • the output is ANDED with the output of a 512 bit array indexed by a 9 bit address of the logical data stream. This translates into 768 bits per STE's within a block can enable any STE within the block. STEs may also connect to adjacent blocks and an STE output can enable one or more other STEs.
  • Automata Network Markup Language is the XML based programming language for an AP. It provides linkages between STEs. ANML implements rule based system for controlling an imaging data stream generated by the CMOS/CCD imaging chip.
  • the user interface generates an image on the operator screen used to monitor the system.
  • the imaging component contains a CIE chromaticity diagram with the color coordinates represented in three axis by (x, y, and z.).
  • the strength of the collision between the returning neutrons that elastically collided with the formation elements is converted into a track or wavelength in nanometers that is scaled to the strength of the collision measured by algorithms written in the proprietary application software.
  • the returning fast neutrons strike the gas molecules triggering photons whose energy is captured by the camera. the and determined by their strength converted photonic energy in color that is mapped according to its chromaticity diagram.
  • Neutrons that elastically collide with rock will return the greatest strength neutrons and neutrons that are partially adsorbed by the liquid or gas hydrocarbons or the liquids from the drilling fluids partially absorb the neutrons and will return less powerful strength collisions.
  • Water principally containing hydrogen, has unique properties in this imaging system since neutrons consisting of hydrogen and oxygen and the neutrons will be greatly absorbed and return the weakest neutrons collision energy since hydrogen atoms have about the same size and mass as the returning neutron.
  • the following Figure 16 demonstrates the relationship of the wavelength in nanometers to their relative value as neutron sources.
  • the Oswald System uses the dominant wavelength, purity and luminance to measure the strength of the elastically collided neutron.
  • a schematic diagram of the resulting conversion of the strength of the returning collision between the fast neutron and the gas that creates the picture of the strength of the collision is shown on the Oswald dominant wavelength, purity, luminance color tree, a relationship between the saturation, (variable shown on the x-axis), the color lightness (variable on the y-axis) and the color hue (variable on the z-axis) is shown in Figure 12.
  • the strength of any resulting collision equates to a value expressed as a single integer representing the (x, y and z) values shown in color on the display.
  • Thermal imaging wavelengths in the region 400 nm to 700 nm are controlled by multi-layer thin film filters (TIFFS). They enable wavelength division multiplexing amplification gain flattening and dispersion compensation in high capacity fiber optic networks (1300 nm to 1600 nm). Temperatures are generally room temperature ranging from 20°C to 50°C.
  • the detectors of this invention are directional detectors and are capable of measuring neutrons entering the detector from a 4 ⁇ solid angle of entry. Ionization energy is released as the fast neutron collide with the penning gas, generally4He, producing scattered alpha particles, helium nuclei. These nuclei are quenched by the quenching gas. The generated electrons lose energy as they drift in a static electric field to an amplification region. Here the electrons enter a high voltage region that generates an avalanche or cascade of secondary electrons thereby enhancing the signal.
  • the imaging methods of this invention are designed to operate this imaging units that collect data in rows of imaging elements, generally pixels, of the imaging unit such as the pixels associated with a CMOS/CCD imaging unit.
  • the imaging unit includes p pixels, these p pixels are generally arranged in a matrix format including n row and m columns.
  • the unit scans the p pixels row by row or column by column.
  • the most efficient format for capturing neutron event data is to analyze pixel data on a row by row or column by column basis. Data associated with each pixel as is it received by the image processing components of the imaging system are analyzed for threshold signature values.
  • the threshold signatures may be pinned to photomultiplier data, where the photomultiplier data signifies amplitude of any generated scintillation light.
  • the photomultiplier data signifies amplitude of any generated scintillation light.
  • the tracks or images include information on the energetics of each event and on the direction from which the fast neutron entered the detector for each event.
  • the event data includes color and/or hue data and intensity data.
  • the data are then compared to data stored in a database.
  • the data in the database include color and/or hue data and intensity data that has been corrected with various solids, liquids, and/or gases commonly found in a downhole setting.
  • the database includes pixels data collected from fast neutrons of different energies colliding with gas mixtures having different mixtures of penning gases and quenching gases and different relative concentrations of penning gases and quenching gases.
  • the database also includes pixel data collected from fast neutrons irradiating different materials– solids, liquids, and gases and mixtures thereof.
  • the analyzing subsystem also includes software for updating and/or refining database of pixel data based on data collected while using the tools of this invention so that the database learns during use of the tools especially during logging wells that have known solid, liquid, and gas profiles.
  • the more the tools are used the more refined the pixel data stored in the database for interpreting an unknown pixel data or event data during downhole data collection during drilling and/or logging.
  • an embodiment of a method of this invention is shown to include returning fast neutrons enter the gas chamber of the detectors of this invention in an enter step 802.
  • the returning fast neutrons collide with atoms of the penning gas in the gas chamber in a collide step 804 to generate energized penning atoms/ions.
  • the energized atoms/ions are quenched by the quenching gas in a quench step 806 to generate electrons.
  • the generated electrons drift down a voltage drift region of the chamber in a drift step 808 generating scintillation light.
  • the scintillation light is captured in a light capture step 810 by one or more photomultiplier tubes, which also triggers the imager if the light intensity of detected by the photomultiplier tube meets a threshold intensity.
  • Capture pixel data associated with a triggered collision event in a pixel capture 812 on a pixel by pixel basis generally as a row or a column in the imager is collected.
  • a pixel collect step 816 where activated pixels are collected to form a collision track or image.
  • the track data is analyzed in an analyze step 818 to produce event data comprising track pixel color/hue/intensity data and track directional data.
  • the track pixel color/hue/intensity data is compared to known pixel color/hue/intensity data in a compare step 820 and the event data is stored. The comparison is used to determine and identify downhole materials (solids, liquids, and/or gases) and map identified materials based on track direction data in a determine, identify and map step 822.
  • the identification and map data is then transmitted to an operator in a transmit step 824.
  • the methods may also include software to refined known data base pixel data or to produce new pixel data for better identification of downhole solids, liquids and/or gases.
  • the operator may then use the identification and map data to adjust drilling trajectories, to stop drilling or to change drilling trajectories.
  • the methods include a system power on step 902.
  • CS test computer subsystem
  • control is sent to a test computer subsystem (CS) step 904. If the computer subsystem does not initialize, then control is sent back to the power on step 904 along a No path. If the computer subsystem initializes, then control is sent along a Yes path to an instrument calibration step 906. After the calibration step 906, control is transferred to an initialize read out step 908, where elevation location data is read. Control is then transferred to a neutron generator subsystem (NGS) test step 910, if the NGS test fails, control is sent along a No path back to the CS step 904.
  • NGS neutron generator subsystem
  • control is transferred along a Yes path to a read neutron generator step 912, where the direction and orientation of the generator is read. Control is then transferred to a first detector D1 test step 914. If the D1 test fails, then control is transferred along a No path to the CS step 904. If the D1 test is successful, then control is transferred along a Yes path to a D1 ready for image capture step 916. Control is then transferred to a second detector D2 test step 918. If the D2 test fails, then control is transferred along a No path to the CS step 904. If the D2 test is successful, then control is transferred along a Yes path to a D2 ready for image capture step 920. Control is then transferred to a D1, D2, and CS ON step 922 to determine whether the two detectors and the computer system are ON and ready for data collection.
  • control is transferred to a computer subsystem communication ON (CS Com ON) test step 924. If the CS Com ON test fails, then control is processes along a No path to the CS step 904. If the CS Com ON test is successful, then control is transferred to an initiate storage for image image capture step 926. Once initiated in the initiate step 926, control is transferred to an initialize index depth locator step 928 so that downhole location data may be read. After initialization of the depth locator, control is transferred to a synchronize detector 1, D1, detector 2, D2, storage, and depth locator in a synchronize step 930. Control is then transferred to a read imaging results step 932.
  • CS Com ON computer subsystem communication ON
  • Control is then transferred to an output synchronized test step 934. If the output synchronized test step fails, then control is transferred along a No path to the initiate storage step 926. If the output synchronized test step is successful, then control is transferred along a Yes path to a capture image from D1 step 936. Control is then transferred to a capture image from D2 step 938. Control is then transferred to an increment locator step 940 and then to a mark locator step 942. Control is then transferred to a capture image and conduct analysis step 944 and then to an end of log test step 946. If the end of log test fails, then control is transferred is transferred along a No path to the capture image for D1 step 936. If the end of log test is successful, then control is transferred along a Yes path to a termination data capture step 947. Control is then transferred to a prepare log step 948 and finally to a output written log step 949.
  • control is transferred to a computer system power up and initialization step 954, where the computer subsystem (CS) is powered up and software is initialized.
  • Control is then sent to detector subsystem power up and initialization step 956.
  • Control is then sent to a detector 1 (D1) pulse charge amplifier test 958. If the test 958 fails, then control is sent along a No path to the step 956. If the test 958 is successful, then control is transferred along a Yes path to a detector 1 (D1) pulse charge circuit test 960. If the test 960 fails, then control is sent along a No path to the step 956.
  • test 960 If the test 960 is successful, then control is transferred along a Yes path to a detector 2 (D2) pulse charge amplifier test 962. If the test 962 fails, then control is sent along a No path to the step 956. If the test 962 is successful, then control is transferred along a Yes path to a detector 2 (D2) pulse charge circuit test 964. If the test 964 fails, then control is sent along a No path to the step 956. If the test 964 is successful, then control is transferred along a Yes path to a commence imaging sequence step 966, where the imaging unit is initialized sequence procedure.
  • D2 detector 2
  • commence imaging sequence step 966 where the imaging unit is initialized sequence procedure.
  • control is transferred to an initialize location proximity sensor step 968, which generators location data as the imaging system collected event data for neutron-gas collisions occurring in the detectors D1 and D2.
  • the event data comprises color/hue/intensity data and track directional data.
  • the method proceeds along to parallel paths concerning the two detectors.
  • the method include simultaneous or parallel steps 970a&b, where event data are collected or captured in detector D1 and detector D2 simultaneously as the two detectors are at different distances from the fast neutron generator of the tools of this invention.
  • the methodd include transmitting the D1 and D2 event data to the computer subsystem CS in simultaneous transmit event data steps 972a&b.
  • control is transferred to parallel or simultaneous interpret event data steps 974a&b.
  • control is transferred to parallel or simultaneous indexing or registering steps 976a&b, where the D1 event data is indexed or registered with D1 location data and the D2 event data is indexed or registered with D2 location data.
  • indexing steps 976a&b control is transferred to parallel or simultaneous logging producing steps 978a&b, where indexed D1 and D2 data is accumulated and organized into D1 and D2 logging data.
  • control is transferred to parallel or simultaneous display D1 and D2 log steps 980a&b, where the produced logging data is displayed for a user or operator to observe so that the logging data is available for determining well drilling direction, when it re-commences or while drilling is proceeding.
  • control is transferred to parallel or simultaneous store logging result step 982a&b, where the D1 and D2 logging results are stored for further analysis or for archival purposes.
  • control is transferred to a stop step 984. The entire process may be started and stopped numerous times during a logging or drilling operation or the process may be continued during the entire drilling operation.
  • FIG. 10A the methods start with an initialize imager step 1002, which initializes the imaging units of the detectors of this invention.
  • the methods then include a capture pixel data on a row by row or column by column basis in a capture pixel data step 1004.
  • the imaging unit such as CCDs, iCCDs, CMOS/CCDs, etc.
  • the software associated the imaging units generally collect data on the pixels on a row by row or column by column basis depending on array orientation and the particular imaging unit.
  • the manner in which the pixels are read also changes.
  • the present methodology is assuming a row by row or column by column pixel data capture format, the same technique is amenable to any pixel data capture format such as two rows at a time, four rows at a time, etc., where each read may be controlled by different processing units so that more of the pixels may be polled on a near simultaneous basis.
  • the entire methodology may be easily implemented on a parallel basis, where different processors analysis pixel data on a parallel basis.
  • the methods include an analyze data captured for each pixel is a capture pixel data step 1006, where data associated with each pixel is analyzed for color, hue, and intensity data. Once analyzed, the color/hue/intensity data of each pixel is compared to threshold values in the threshold test step 1008. If a pixel fails the threshold test, then control is transferred along a No path to the analyze step 1006, where another pixel is analyzed. If the pixel passes the threshold test, then control is transferred along a Yes path to a correlated test step 1010. If the pixel data are not correlated with a photomultiplier threshold event, then control is transferred along a No path back to the capture pixel step 1004.
  • a collect pixels step 1012 to form or generate a track/image of a neutron-gas collision event in the gas chamber.
  • the collecting step 1012 continues until a track/image of the neutron-gas collision event is complete– all pixels associated with an event have been collected. Of course, as if with the other method steps, these steps may be performed on a parallel basis.
  • the collected track/image is analyzed in an analyze track/image step 1014 to generate event data including color/hue/intensity data and direction data.
  • the methods include a compare step 1016, where event data is compared to event data stored in an event database.
  • the database includes color/hue/intensity data from known events, which correspond to data collected from other formations having known solid, liquid, and/or gas compositions and/or event data collected from simulated formations having known solid, liquid, and/or gas compositions.
  • interpreted output of the event data occurs in an data output step 1018.
  • FIG. 10B another embodiment of the methods of this invention, again starts with an initialize imager step 1052, which initializes the imagining unit of the detectors of this invention.
  • the methods then include a capture pixel data on a row by row or column by column basis in a capture pixel data step 1054.
  • the methods include an analyze each capture pixel data step 1056, where data associated with each pixel is analyzed for color, hue, and intensity data. Once analyzed, the color/hue/intensity data of each pixel is compared to threshold values in the threshold step 1058. If a pixel fails the threshold test, then control is transferred along a No path to the analyze step 1056, where another pixel is analyzed.
  • control is transferred along a Yes path to a correlated test step 1060. If the pixel data are not correlated with a photomultiplier threshold event, then control is transferred along a No path back to the capture pixel step 1054. If the pixel data are correlated, then control is transferred along a Yes path to a collect pixels step 1062 to form or generate a track/image of a neutron-gas collision event in the gas chamber. The collecting step continues until a track/image of the neutron-gas collision event is complete– all pixels associated with the event have been collected.
  • the collected track/image is analyzed in an analyze track/image step 1064 to generate event data including color/hue/intensity data and directional data.
  • the methods include a compare step 1066, where event data is compared against event data stored in an event database.
  • the database includes color/hue/intensity data from known events, which correspond to data collected from other formations having known solid, liquid, and/or gas compositions and/or event data collected from simulated formation having known solid, liquid, and/or gas compositions.
  • control goes back to the compare step 1066 to re-evaluate the comparision and the certainty test. If the certainty test is passed, then control is transferred along a Yes path to an data output step 1072, where interpreted event data is outputted to the user. Once a logging operations is completed or a logging while drilling operation is completed, then the methods proceed to a stop imager step 1074, which stops image processing unit the initialize imager step 1052 activated.
  • the XYZ Tristimulus values describe any visible color.
  • the XYZ system is based on color matching experiments called the trichromatic color theory. Every color may be represented by 3 values, generally expressed as a column vector of values e 1 , e 2 , and e 3 .
  • the space of visible colors is represented in a 3D space.
  • Calculating the CIE-XYZ Color Coordinate System is based on the three monochromatic primary colors red, green and blue, which have absorption maxima of 435.8 nm, 546.1 nm, and 700 nm in a 2 degree field as shown in Figure 11. These were defined as CIE-RGB primaries and color matching function (CMF).
  • CIE-RGB primaries and color matching function (CMF) color matching function
  • CIEXYZ color coordinate system is shown graphically in Figure 12.
  • CIE-RGB to CIE- XYZ is shown graphically in Figure 13, where Cr, Cg, Cb must enclose the Gamut.
  • Line Cr-Cg is tangent at 650+ (z is zero beyond 650). Thus Cr is defined.
  • Cb and Cg are defined.
  • the ma in is iven in matrix form as follows:
  • tristimulus values of the spectrum X, Y and Z corresponding to the color matching functions are found by multiplying their primes times the spectrum in question. If two coordinates are given the third is automatically determined.
  • the CIE system works on formulas not on color samples. The entire spectrum of fully saturated hues lies on the perimeter of the curve. The CIE system determines the z(Z), y(Y), and x(X) from the spectrum being analyzed from which the matching function values are determined.
  • a MULTI-DIMENSIONAL LOOK-UP TABLE DRIVEN BY OUR CIE COLOR CHART Math Model of What Is down the Hole [0251] A look up table is a function from one space to another that is defined in terms of a few samples, their corresponding function values and a method for calculating a mapping from one of those samples. Mathematically this is represented as:
  • I(x) is the function or algorithm that is used to compute the value in the range space for an arbitrary point in the domain space x.
  • the function I(x) interpolates the output if the point x is within the convex hull of the sample set (x k ) and the extrapolates the output if it is not.
  • the first step is to determine which samples in the table to use for interpolation. Since the tri-linear method uses all eight points of a cube around the point to be computed, it is easy to determine the approximate samples using sample indexing.
  • the approximation using tri-linear interpretation consists of three steps:
  • index [i, j, k] defines the cube with vertices C(i, j, k), (i+1, j, k) ](i, j+1,
  • ,(i, j, k) ⁇ ,(i, j, k), ,(i+1, j, k), ,(i, j+1, k), ,(i, j, k+1]), ,(i+1, j+1, k) ,(i+1, j+1, k+l), ,(I, j+1, k+1), ,(i+1, j+1, k+1) ⁇
  • the methodology illustrates calculating a value of an integer in the Color Database called BASE using tri-linear interpolation, where the numeric variables are given by v and w
  • variables v and w are stored as sixteen bit numbers (4 Hex).
  • the interpolated value methods is based on the Database as follows values are given by ordinals c. Three dimensional vectors are ordinal numbers defined respectively as i,j,k.
  • Color sensitivity correlate the CCD-CMOS imager to the McAdams ellipses as shown in Figure 20. MacAdam ellipses are small ellipses arc actual size, large ellipses are 10 times actual size for better viewing.
  • Figure 19 correlates with the following X, Y table correlating frequencies to X and Y values as shown below.
  • CMOS active pixel sensor color imaging array 2102 including green light sensitive elements 2104, blue light sensitive elements 2106 and red light sensitive elements 2108 as shown in the expanded insert.
  • the chip 2100 also includes analog-to-digital conversion region 2110 and an analog signal processing region 2112.
  • the chip 2100 also includes a digital logic regions 2114 supporting interface, timing, processing and output circuitry.
  • the chip 1700 also includes a clock and timing control region 2116 and a pad ring 2118.
  • CMOS sensor chip vertical/horizontal shift registers associated with image acquisition generally 2200, is shown to include light sensing elements arranged in rows 2202 and columns 2204.
  • the CMOS sensor chip also include vertical shift registers 2206 and horizontal shift registers 2208 resulting in a CMOS sensor chip output 2210.
  • This architecture is used by the CMOS sensor chips to collect and perform initial processing on the pixel data and generating an output for processing by imaging processing units.
  • FIG. 23 a schematic diagram of a memory array architecture for processing CMOS sensor chip output in parallel, generally 2300, is shown to include an input signal 2302 the CMOS sensor chip to an input symbol row decoder 2304.
  • the architecture 2300 also includes a state transition clock input 2306.
  • the row decoder 2304 produces row enabled data channels 2308 connected to memory busses 0 through n associates with a zeroth symbolic trajectory evaluation (STE 0 ) and associated symbolic trajectory evaluation memory columns STE 1-m .
  • the processing is controlled by logic elements L associated with each STE element.
  • the logic is triggered by the clock input 2306 and controlled by an automate routing matrix structure 2310.
  • FIG. 24 a schematic diagram of a routing matrix associated with memory array architecture, generally 2400, is shown to include a first end block 2402 and a second end block 2404.
  • the first end block 2402 includes two block switches 2406a&b and two column switches 2408a&b.
  • the second end block 2404 includes two block switches 2410a&b and two column switches 2412a&b.
  • the matrix 2400 also includes a plurality of light element blocks 2414 (a single one shown here).
  • Each light element block 2414 include row switches 2416a&b and elements 2418a-d, which extend vertically and horizontally depending on the number of STE's.
  • the block switches 2406a&b and the column switches 2408a&b and the block switches 2410a&b and the column switches 2412a&b are in communication via light grey communication pathways.
  • Each column switch 2408a&b and 2412a&b is in communication with other column switches (not shown) via light dark gray communication pathways.
  • the row switches 2416a&b are in communication with other row switches (not shown) and the elements 2418a&b via dark gray communication pathways.
  • the block switches 2406b and 2410b and the row elements 2420a&b are in communication via the black communication pathways.
  • the CMOS sensor chip 2400, the register configuration 2200, the memory array architecture 2300, and the matrix configuration 2400 are configured so that image captured by the CMOS sensor chip 2100 is outputted and analyzed. In this case, the output is analyzed to determine the nature and make up of solids, liquids and/or gases in downhole formation.
  • Bombardment of solids is dependent upon the surface area or cross section being bombarded. Collisions between energy particles and solid surfaces can be calculated from classical mechanics with good accuracy. A moving atom colliding with a stationary atom will be deflected from its course by an amount which is dependent on its energy and its distance; the deflection being greater for smaller energies and for closer approaches. The energy's momentum, transferred to the stationary atom increases as the angle of deflection increases. The probability for any given amount of energy transfer can be measured by a ring shaped region in which the path of an incident particle must lie in order for this energy transfer to occur. This area is the differential cross section for energy transfer.
  • e F is approximately equal to (3p2)b(a 0 )2(N e )bE R
  • E R is the Rydberg Energy (13.60 eV)
  • N e is the number of conduction electrons per unit volume.
  • the Fermi energy of most metals lie between 2 and 12 ev.
  • E is the energy of the moving atom
  • v is its velocity
  • Z 1 Ne is its charge
  • x is the distance it has traversed
  • N 0 is the density of the atoms in the medium
  • m is the electron mass
  • J is the mean excitation potential of the electrons in the stopping material
  • Z 2 N is their effective atomic number. J and Z 2 Ncan only be found approximately from theory.
  • Z 2 N is the number of electrons likely to be excited, namely the number for which the excitation energy is less than (m/M 1 )E and J can be approximated to 10Z 2 (eV).
  • Moving charged particles produce displacements primarily by elastic collisions interacting essentially one at a time with the stationary atoms. According to the Bohr analysis, it is adequate to assume that in such collisions the moving and stationary atoms interact with the screened Coulomb potential energy of the form:
  • b 2Z 1 Z 2 e2/ ⁇ v2 2-7
  • v is the velocity of the incident particle
  • b is the distance to which the two nuclei would approach in a head-on collision in the absence of screening (Bohr called this the "collision diameter" and is the reciprocal of the energy of the incident atom.
  • the elastic collisions are of the Rutherford type when E o E A and approximately of hard sphere type when E n E A .
  • E A E R [2(M 1 +M 2 )/M 2 ]Z 1 Z 2 (sqrt((Z 1 ))a + (Z 2 )b 2-8
  • ds (s T /T m )dT 2-19 where s T is the total neutron elastic cross section (now considered due to elastic collisions).
  • Neutrons from fission have a broad range of energies from 0 -15 Mev with an average of 2 Mev. Calculation of irridation effects assume that neutrons have an average energy 1 and 2 Mev.
  • T (4/A)(1+(1/A))!2 ⁇ 4/A (MeV) 2-21
  • A is the atomic mass of the target material.
  • hydrogen a principal component of hydrocarbons and water receive a mean energy of 1 Mev and carbon 280 keV.
  • the anisotropy effect reduces the mean energy transferred by a factor of between 1 ⁇ 2 and b in most elements.
  • the correction factor is more important at higher neutron energies.
  • the scattering involved in collisions that produce displacements is primarily due to Coulomb interaction between the electron and the target nucleus.
  • Measuring the effect of radiation on atoms and molecules permits the analyzes and calculations to determine and identify solid, liquid, and/or gas atoms and/or molecules that have interacted with initial fast neutrons based on the interactions between returning fast neutrons and gas molecules in the gas chamber of the detector or detectors allowing determination of the properties and characteristics of the materials downhole.
  • the purpose of this discussion is to describe the mathematical methodology used for calculating the penetration strength of the nuclear sources for imaging a formation while drilling.
  • the indicator that has the greatest effect on the calculations is the percentage of water.
  • Neutrons, in down hole drilling have traditionally been used for this purpose to determine the water table.
  • Our limits on the distance we can detect hydrocarbons depends upon the porosity of the soil and its impact on the energy of the instrument's returning energetic parameters.
  • Bessel functions For calculating the depth of penetration we use Bessel functions to describe the radiative power of our initial source. The resulting energy calculation is based on the penetrating power of the fast neutrons and is not dependent upon the angle of radiation penetration.
  • the energy depicted by an indicator in the far-ultra violet region is sufficient to demonstrate the power to ionize an atom or molecule by the process:
  • the typical ionization energy is about 10 eV or 960 kJ mol–1.
  • E is the electric field and B is the magnetic field.
  • Bessel functions of half integer order in terms of the standard trigonometric functions include: [0314] We are measuring the amount of energy in the form of light absorbed by a rock sample as a function of the percentage of the energy of the light transmitted from our nuclear source. We start with a known radiation energy level from our Americium/Beryllium source. We measure the amount of the light absorbed from the radiation directed at the surrounding environment in a 180° arc for each detector. For example, it is measured as:
  • g is called the extinction coefficient. If C is in moles per liter, and R is in centimeters, g has the unit's liter mole–1cm–1 (M–1cm–1) it is referred to as the molar absorptivity. When e is reported without units, the extinction coefficient tells you how strong a particular sample absorbs light at a particular wavelength.
  • the absorption is also called the optical density (OD).
  • OD optical density
  • Our camera's CMOS imaging chip is measuring A.
  • the amount of absorbance A is compared to a chart of materials independently derived for identification purposes. They convey the level of porosity of the resulting sample.
  • Several substances that we are looking for such as water and selected hydrocarbons have known absorption rates.
  • imaging absorbance software By using imaging absorbance software to screen out some materials, it is possible to identify the hydrocarbons and water in our sample.
  • the energy given by the equation is that associated with a single photon of radiation of frequency v or wavenumber and is extremely small.
  • the wavelength of radiation depends upon the medium through which it is traveling. It is necessary in spectroscopy to convert all wavelengths to vacuum wavelengths using the relationship:
  • ç air is the refractive index of air, and is related to the speed of light in the two media by:
  • Wavenumber is not independent of the medium but in spectroscopy is invariably taken to be defined as:
  • the electric and magnetic character of a single photon of radiation is represented by two waves in the xy plane.
  • the wave (or photon) we are capturing in the visible region is traveling in the x direction.
  • a photon in the visible region falls on the human eye, it is the interaction of the electric component with the retina which results in detection.
  • a photon falls upon our detector its color is used to identify the substance we are attempting to identify.
  • Bond Order (net number of bonding electrons) divided by 2.
  • AO atomic orbitals
  • MO molecular orbital
  • Oxygen: O 2 (s g 1s)2(s u ls)2(s g 2s)2(s u 2s)2(s g 2p)2(p u 2p)4(p g 2p)2
  • Fast neutron source (241Am/242Cm/9B with flux of 9 x 107, fast unthermalized neutrons/cm2/s. Counts in the photo peaks of the spectra, per gram target element are plotted in the reference.
  • the system provides a depth profile which is a plot of the concentration of a material as a function of depth of the surface being analyzed.
  • the functions contributing to the depth are: 1) the actual concentration profile; 2) sampling depth of the energy beam from the fast neutrons; 3) the sampling width of the energetic neutrons; and 4) the observed depth profile. Setting the sensitivity and detection limits for quantitative application is extremely important and can only be verified by experiment. The relationship measures the differences between the material concentration and the measured intensities.
  • the detection limit is the minimum amount of material detected using a spectral line.
  • Embodiments of this invention relate to methods for creating an industrial geological database using electron spectroscopy based on collision between returning fast neutron and gas molecules in the gas chamber of the detectors of this invention. These collisions contain information about interactions between initial fast neutrons as solids, liquids and/or gases associated with a formation or zone thereof irradiated by fast neutrons from a fast neutron source associated with the tools of this invention. The collision data is then used to determine, identify and classify the properties and characteristics of the formation or zone being logged using the tools of this invention. Important properties of light that aid in the analysis of the collision data contained in an image or a plurality of images from the imaging unit of this invention, are given in Table II.
  • a molecule with n atoms will have 3n - 6 modes of vibration.
  • a linear molecule will have 3n - 5 modes of vibration because there is no rotation about the molecular axis.
  • a normal coordinate is a single coordinate along which the progress of a single normal mode of vibration can be followed. If the carbon atom C moves 15.995/12.000 as far as the oxygen atom by motion along the normal coordinate we mean that the carbon atom moves a distance ⁇ r(C) and the oxygen atom moves a distance ⁇ r(O) as:
  • the kinetic energy is:
  • a streamlined procedure for constructing a similar matrix for (H 2 O) water has the following rules:
  • a i is the number of times the ith irreducible representation appears in the reducible representation
  • h is the order of the point group
  • R is an operation of the group
  • ⁇ R is the character of the Rth operation in the reducible representation
  • ⁇ R is the character of the Rth
  • CR is the number of operations in the class.
  • the wavelengths of absorbed light are approximate.
  • the following colors relate from a color wheel the relationship between light absorbed and recorded on the camera and the color of the complex (light transmitted).
  • Color complexes absorb a wide range of colors not a single wavelength. This measures the energy absorbed by a single complex that absorbs a single photon.
  • Avogadro's number (6.02 ⁇ 1023). The calculation is made as follows:
  • PES photoemission spectroscopy

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Abstract

Logging tools include at least one neutron source, at least one neutron detector positioned a prescribed distance from the neutron source, and at least one processing/analyzing unit or subsystem, where the detectors include a gas chamber having a voltage drift region and containing a gas mixtures capable of interacting with fast neutrons to produce detectable events that are imaged by an imaging subsystem and interpreted by an analyzing subsystem and systems and methods using the tools. The tools may be disposed on a wire line or integrated into a drill string so that logging may be performed while drilling.

Description

TITLE: APPARATUSES, METHODS AND SYSTEMS FOR DOWNHOLE IMAGING
RELATED APPLICATIONS
[0001] The present invention claims priority to and the benefit of Unites States Provisional Patent Application Serial No.62/190,539 filed 07/09/2015 (9 July 2015).
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] Embodiments of this invention relates to apparatuses, methods, and systems for downhole imaging to determine formation properties or characteristics and formation fluid properties or characteristics, especially properties of hydrocarbon fluids in oil and gas wells during and/or after drilling. The following description relates to an apparatus, a method and a system for using fast neutron energy to determine the composition of matter and specifically the hydrocarbon content down hole during drilling of an oil and gas well.
[0003] More particularly, embodiments of this invention relates to apparatuses, methods, and systems for downhole imaging to determine formation properties or characteristics and formation fluid properties or characteristics, especially properties of hydrocarbon fluids in oil and gas wells during and/or after drilling, where the imagining uses fast neutron energy, where the apparatuses comprise a down hole tool including a neutron generator subsystem, a neutron detection subsystem, and an analyzing subsystem, where the apparatuses and systems convert detectable neutron induced events into formation and formation fluid properties or characteristics.
2. Description of the Related Art
[0004] The detection of fast neutrons as a probe of material structure and composition has been used for seventy years. Fast neutrons were discovered by Rutherford in 1932. Using charged radioactive particles probes is straightforward as they leave a path through the material under investigation. Fast neutrons penetrate all types of matter including steel drilling pipe.
Energetic or fast neutrons, neutrons with varying energy levels depending upon their original source, were discovered by Chadwick in the laboratory of Rutherford in 1932. Subsequent study led to their characterization. Some of the characteristics of neutrons are: 1) an electric charge of zero (0); 2) a mass of 1.0087 atomic mass units; 3) a spin of ½; 4) a magnetic moment of -1.9132 nuclear magnetrons; 5) a lifetime of approximately 894 seconds, and 6) a decay profile into a proton, an electron, and an antineutrino, over their fifteen minute lifetime, with a small number of neutrons decaying into a proton, an electron, an antineutrino, and a gamma ray. We are specifically interested in this invention in capturing information about the energetic activity of the electrons. Interactions between neutrons and other types of matter are confined to short range nuclear and magnetic interactions. Neutrons have the unique property of being able to penetrate through matter and are used uniquely to probe bulk condensed matter. Since neutrons can be deflected by some surfaces when incident at glancing angles, neutrons can be used as a surface probe without destroying the matter it is being used to analyze. Spectral identification with neutrons of varying energies are being used with proppant that are placed in a subterranean fracture zones are captured with neutron cross sections to identify materials in gas wells.
[0005] The petroleum industry uses various methods to characterize geological formations. Characteristics of the deposits down hole are determined from the measurements taken and the quantities of hydrocarbons, rock types, etc. Among the characteristics of geological formations the thermal neutron cross section (SIGMA), density, porosity, hydrogen index, salinity and photoelectric factor are usually measured by wireline tools or logging while drilling (LWD) that include neutron and gamma ray detectors. They are placed some distance from the source and generally use the principle of Compton scattering to derive formation density. These measurements were made with single detector tools that had no capability to compensate for borehole effects. The limitations inherent in these tools led to the further development of multiple dual detector density tools in which compensation is based on the spacing between the sources and the detectors. Each source measures a different formation property characteristic and multiple tools are used together in the same logging operation. They also tend to interfere with each other that make the tool string long. See e.g., United States Patent No.7,482,578.
[0006] United States Published Application No. 20060192096 disclosed methods for formation logging in accordance with one embodiment of the invention includes emitting neutrons and gamma rays into a formation, using a source on a logging tool disposed in a borehole penetrating the formation; and detecting gamma-ray signals and neutron signals scattered by the formation, using at least one detector on the logging tool. United States Published Application No. 20020170348; disclosed a logging tool includes an elongated body housing a neutron source and at least one neutron detector positioned along one side of the neutron source. Some embodiments of the logging tool include at least one gamma ray detector longitudinally separated from and to one end of the neutron source, and may be used to make simultaneous gamma ray and neutron logging measurements. In some embodiments, the logging tool also includes a (n, 2n)-neutron shield positioned to one end of the neutron detector, longitudinally between the neutron detector and the neutron source.
[0007] The detection of fast neutrons as a probe of material structure and composition has been used for seventy years. Fast neutrons were discovered by Rutherford in 1932. Using charged radioactive particles probes is straightforward as they leave a path through the material under investigation. Fast neutrons penetrate all types of matter including steel drilling pipe. Direct calculations can be made using this technique without the cost of either having to pull the pipe out of the borehole or to perforate the pipe in order to take imaging measurements. This apparatus does not require that neutrons first be thermalized in order to calculate the effects down hole with matter which is customarily done in the industry to measure water and density. The challenge in detecting neutrons has usually been that a method was necessary to slow them down or thermalize them in order to evaluate their path. Detection of neutrons requires that the neutron interact with the nucleus of an atom in a material from which it is exiting. The usual result of such an interaction is the emission or recoil of a charged radioactive particle which is subsequently detected. In this apparatus the neutron recoiling emission with matter is then recoiled with a scintillation gas that creates an electron. The electron creates an imaging track from which useful information can be interpreted about the neutrons original interaction with matter. When indexed with a locator, this technique provides a more precise method for categorizing the materials down hole.
[0008] While several systems, methods and apparatuses have been proposed and used for downhole formation imaging or logging (in real time or at different points during the drilling operation) using fast neutrons, there is still a need in the art for new, novel and improved well imaging or logging systems, apparatuses and methods using fast neutrons to determine formation characteristics, formation fluid compositions, and formation permeabilities.
SUMMARY OF THE INVENTION
[0009] Embodiments of this invention include systems, apparatuses, and methods for detecting detectable neutron events to generate neutron event data, analyzing the neutron event data, and converting the neutron event data into formation solid, liquid, and/or gas properties or characteristics. Embodiments of this invention further include software programs and software methods implemented by or on at least one processing unit for analyzing the neutron event data from the apparatuses or systems of this invention generating the formation solid, liquid, or gas properties or characteristics. The systems, apparatuses, and methods are substantially insensitive or completely insensitive to other forms of radiation including naturally occurring radiation downhole or other radiation forms used in downhole oil and/or gas exploration, but are sensitive to fast neutrons having energies between 100 keV and 15 MeV.
[0010] Embodiments of the present invention apparatuses and systems include a fast neutron generation subsystem, a detection subsystem, and an imaging subsystem. The fast neutron generation subsystem includes at least one fast neutron source. The detection subsystem also includes at least one detector having a gas chamber and a voltage unit capable of producing a voltage drift region in the gas chamber. Each gas chamber contains a gas mixture including at least one perfluorinated hydrocarbon gas having between 1 and 5 carbon atoms and 4He at a pressure of at about one atmosphere. In certain embodiments, the gas mixture includes between about 5 vol.% and about 25 vol.% of the at least one perfluorinated hydrocarbon gas and between about 75 vol.% and about 95 vol.% of 4He. Each voltage drift unit includes a plurality of parallel ring (vertically stacked) conductive elements configured to generate a voltage profile across the chamber in its longitudinal direction. The image subsystem includes at least one imaging unit that is capable of detecting or imaging scintillation light produced from fast neutron-4He collisions, resulting electron cascades and drifting through the drift region. The apparatuses and systems may also include a communication subsystem including communication hardware and software capable of transmitting or sending detected neutron event data from the imaging subsystem to and at least one analyzing subsystem
[0011] Embodiments of the methods and software methods involve detecting, imaging, and/or analyzing fast neutron events occurring in the detection subsystem arising from fast neutron reflected, scattered, and/or refracted by and/or from downnhole formation solids, liquids, and/or gases irradiated by fast neutrons from the at least one fast neutron generator or source. The methods and software methods involve controlling and directing fast neutrons at a geological or downhole structure, detecting neutrons entering the detection subsystem, and capturing images of neutron events within the detection subsystem, and/or capturing neutron event data using the imaging subsystem. The methods and software methods may also include storing the captured images and/or data, transmitting the capturing images and/or data and/or analyzing captured images and/or data to determine formation solid, liquid, and/or gas properties and characteristics. In certain embodiments, the captured images and/or data are processed downhole and transmitted uphole for output to a user or for further processing, temporarily stored downhole for later processing uphole, transmitted uphole for immediate processing, and/or a combination of thereof. Typically, once uphole, the images and/or data are used in one or more formation evaluation models to derive the desired formation solid, liquid, and/or gas properties or characteristics. Formation models are typically software programs used to evaluate the geological formation based on the images and data gathered downhole. For example, the formation data and/or images are often combined with other measurements (e.g., neutron porosity measurements and resistivity measurements) to determine formation solid, liquid, and/or gas properties or characteristics including, without limitation, gas saturation, lithology, porosity, the density of hydrocarbons, formation pore space, properties of shale sands, and/or other parameters of interest.
[0012] The apparatuses, systems, and methods of this invention are designed to assist a driller in improving drilling, thereby improving the rate of recovery of hydrocarbons principally from natural gas wells. The apparatuses, systems, and methods of this invention may also be useful in improving vertical drilling, horizontal drilling or drilling wells including vertical, horizontal or angled sections to improving detection and recovery of formation fluids including hydrocarbons, both gases and liquids.
[0013] The computer subsystems of this invention are used to capture fast neutron gas collision events occurring within the gas chamber of the neutron detector of a downhole tool as images and associated image data, while a well is being continuously drilled or when a wire line is used during drilling or drill stoppages. The computer subsystems may also include a storage device capable of storing neutron event images and associated data from the imaging subsystem produced by fast neutron returning towards the detector after interaction with formation materials, solid, liquids, and/or gases within a geological formation. The computer subsystems may also include an analyzing subsystem to permit preliminary and/or thorough analysis of the images to determine desired formation solid, liquid, and/or gas properties and characteristics.
[0014] Embodiments of the invention provide methods for continuously monitoring a location of the detector(s) relative to the fast neutron source and its position within the well.
[0015] Embodiments of the invention provide methods for continuously measuring interactions between fast neutrons and the gas mixture within the gas chamber of the detection subsystem by creating images of events occurring within the chamber, where the images may be continuously captured over a set period of time before, during and/or after a neutron irradiation event, semi- continuously captured before, during and/or after a neutron irradiation event, or captured due to a threshold triggering event based on monitoring a response of a monitoring unit within the imaging or data capturing component of the imaging subsystem.
[0016] In certain embodiments, the neutron detection subsystems of this invention include at least two fast neutron detectors placed at a precise distance from each neutron source, where each detector captures images and associated data of interactions between the fast neutrons entering the gas chamber and the gas mixture in the gas chamber, where the fast neutrons entering the chamber comprise fast neutron reflected by, scattered by, refracted by, absorbed and reemitted by the formation and/or formation fluids after fast neutron irradiation from at least one fast neutron source. The apparatuses and systems of this invention also include a computer and/or processing unit used to operate the imaging subsystem such as a CCD imaging unit, especially a CMOS/CCD imaging unit, that captures images and associated data for subsequent interpretation and image analysis. The apparatuses and systems of this invention may also include a data storage unit for storing the images and associated data and a communication subsystem for transmitting the images and associated data between the imaging subsystem and a human operator. The apparatuses and systems may also include a power subsystem for providing power to the detection subsystem, the imaging subsystem, and the other subsystems.
[0017] In certain embodiments, the apparatuses and systems also include a set of software routines capable of analyzing the images and associated data. [0018] In other embodiments, the apparatuses and systems also include a tool including the subsystems that is integrated into drilling apparatus. In other embodiments, the apparatuses and systems include a tools affixed to a wire line.
[0019] In other embodiments, the detection subsystem comprise directional fast neutron detection subsystem that are capable of detecting fast neutron events within the gas chamber to determine not only energetic properties of the events, but the direction from which the neutrons entered the gas chamber.
[0020] In other embodiments, the apparatuses and systems are attached to a wire line typically used in oil and gas well logging. This attachment may be a physical attachment and may be supplemented by a remote capability that will disconnect the sonde in case the device gets stuck in the pipe and cannot be fished out.
[0021] When in operation, the apparatuses and systems send event images and associated data up a data cable to an analyzing subsystem, which is monitored by a remote operator interpreting the data above ground. This operator may be located in proximity to the bore hole such as adjacent to the drilling site or the interpreter may be located remotely over a communication link for remote monitoring and analyzing.
[0022] In other embodiments, the apparatuses and systems provides improved well logging tools for performing nuclear measurements on a subsurface earth formation surrounding a borehole. In certain embodiments, the tools include detectors capable of detecting gamma rays. In other embodiments, the tools improve hydrogen index and neutron porosity measurements.
[0023] Embodiments of this invention relate to tools for formation logging, where the tools include a support configured for movement in a borehole. The tools also include a neutron irradiation subsystem including at least one neutron source, a neutron detection subsystem including at least one detector, and an imaging or data capturing subsystem including at least one imager or data capture unit. The tools may also include a communication subsystem including communication hardware and software. The tools may also include an uphole and/or downhole analyzing subsystem including at least one processing unit and software routines that interprets the images and associated data to generate formation and formation fluid properties or characteristics.
[0024] Other embodiments of the invention relate to methods for formation logging that include emitting neutrons into a formation, using a neutron source on a logging tool disposed in a borehole penetrating the formation, and detecting neutron signals from neutrons scattered by the formation, using at least one neutron detector associated with the logging tool.
[0025] Other embodiments of the invention relate to methods for formation logging that include emitting neutrons into a formation, using a neutron source on a logging tool disposed in a borehole penetrating the formation. The methods also include detecting neutron signals scattered by the formation using at least one neutron detector on the logging tool, the signals being associated with the neutron-gas interactions or neutron events occurring in the neutron detectors. The methods also include deriving a correction signal using high-energy signal spectra from the detected signals, and applying the correction signal to the detected signals to correct for neutron interference and/or borehole effects on the detected signals.
[0026] Embodiments of this invention provide systems, methods and calculation procedures including a detection scheme that is insensitive to all other forms of radiation used downhole in oil and gas exploration except for fast neutrons having energies between 100 keV and 15 MeV.
[0027] Other embodiments of the present invention provide systems or apparatuses including a tubular structure including a gas chamber containing a mixture of a halogenated hydrocaron (e.g., CF4 or other halogenated hydrocarbons such as a FREON®, a registered trademark of DuPont) and an inert gas (e.g., 4He) at a given temperature and pressure. In certain embodiments, the gas mixture includes from about 75 vol.% to about 95 vol.% of 4He and from about 5 vol.% to about 25 vol.% CF4.
[0028] The interactions between the fast neutrons generated by a neutron generator, referred to herein as initial fast neutrons, and materials in a geological structure downhole produce fast neutrons, referred herein as returning fast neutrons, that are either scattered, reflected, refracted, and/or otherwise directed back toward a detector located within a borehole of an oil/gas well or injection well by or from the materials. A detection subsystem captures via an imager and reported the images to an analyzing subsystem for analysis. The analysis of these images provides drillers with data to improve drilling trajectories, especially in horizontal sections, and thereby improve hydrocarbon production from oil/gas wells, especially gas production from natural gas wells. The present systems and methods may be used for drilling vertical wells, horizontal well or well segments.
[0029] The analyzing subsystem is used to store and analyze images captured downhole by the downhole detection subsystem either while drilling or during wire line logging. The detection subsystem may operate continuous, periodically, or intermittently while drilling. The analyzing subsystem may include both a downhole component and a surface component. Both the downhole component and the surface component may be involved in analysis of the images and the analysis work may be distributed between to the components so that the downhole component would produce preliminary results and the surface component would produce refined results.
[0030] Embodiments of the invention provide methods for continuously monitoring formation materials while drilling or during wireline logging based on images captured from at least one detector positioned relative to at least one fast neutron source position within the well.
[0031] Embodiments of the invention provide methods for continuously capturing and analyzing images generated from detecting returning fast neutrons, which correspond to interactions between formation materials and initial fast neutrons.
[0032] Embodiments of this invention provide systems including 1) a detection subsystem including at least one fast neutron generator, at least two fast neutron detectors including a gas chamber unit and an imaging unit placed at a precise distance from the at least one neutron generator, where the detectors detect and that capture images of returning fast neutrons collisions of gases of a gas mixture of a gas chamber in the detectors, where the returning fast neutrons correspond to interactions between the initial fast neutrons and the materials in the wellbore and/or in the formation penetrated by the well bore; 2) an analyzing subsystem including at least one processing unit used to operate the imaging unit (e.g., CMOS/CCD imaging system) to detect and capture images of the collisions for subsequent interpretation and image analysis; 3) a data storage subsystem for storing the images; 4) a communication subsystem interconnecting the subsystems; 5) software algorithms for analyzing and interpreting, 6) a power subsystem connected to the subsystems for supplying power to the subsystems; and 7) a connector to affix the detection subsystem to a wire line or to mount the detection subsystem in a tool associated with a drilling string.
[0033] In certain embodiments, the detection systems are based on the use of a mixture of a noble gas and a halogenated hydrocarbon gas (e.g.,4He and CF4) that limits interactions with other radiation sources or are tuned to limit interactions with other radiation sources, which would produce spurious signals and/or noise. The detection systems are directional fast neutron detectors that produces images of fast neutron gas collisions including energetics and directional data.
[0034] The detection subsystems are designed to be attached to a wire line typically used in oil and gas well logging. This attachment is a physical attachment and may be supplemented by a remote communication component that will disconnect the sonde in case the device gets stuck in the pipe and cannot be fished out.
[0035] The imager(s), when in operation, capture images and either analyze image data downhole via a downhole analyzing component and/or send image data up a data cable to a surface analyzing component, where an operator monitoring the data may adjust drilling trajectory based on the analyzed data. The surface analyzing component may be located in proximity to the bore hole such as adjacent to the drilling site or the interpreter may be connected remotely over a communication link and monitored remotely.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The invention can be better understood with reference to the following detailed description together with the appended illustrative drawings in which like elements are numbered the same:
[0037] Figure 1A depicts a functional block diagram of an embodiment of a system of this invention.
[0038] Figure 1B depicts a functional block diagram of an embodiment of a system of this invention.
[0039] Figure 2A depicts a functional block diagram of another embodiment of a system of this invention.
[0040] Figure 2B depicts a functional block diagram of another embodiment of the system of this invention.
[0041] Figure 3A depicts an embodiment of a wireline tool system of this invention.
[0042] Figure 3B depicts another embodiment of a wireline tool system of this invention.
[0043] Figure 4A depicts an embodiment of a drilling and logging system of this invention.
[0044] Figure 4B depicts another embodiment of a drilling and logging system of this invention.
[0045] Figure 5 depicts a two detection subsystem embodiment of this invention and illustrative penetration profiles and detection profiles.
[0046] Figure 6A depict an embodiment of a fast neutron detection subsystem of this invention.
[0047] Figure 6B depicts an embodiment of a gas delivery subsystem of this invention.
[0048] Figure 7 depicts illustrates that neutron detection process of the fast neutron detection subsystem of this invention of Figure 6A.
[0049] Figure 8 depicts an embodiment of a method illustrating the events and steps that lead to the capture, analysis and interpretation of logging data using the systems of this invention.
[0050] Figures 9A-B depict an embodiment of a method for operating the systems of this invention.
[0051] Figures 9A and C-D depict another embodiment of a method for operating the systems of this invention.
[0052] Figures 10A-B depict embodiments of a method for operating the imaging subsystem of this invention.
[0053] Figures 11-20 depict an embodiment of a CIE imaging analysis used to analyze returning fast neutron energetics.
[0054] Figure 21 depicts a schematic diagram of a CMOS Sensor Chip.
[0055] Figure 22 depicts a diagram of typical CMOS Sensor Chip vertical/horizontal shift register associated with image acquisition.
[0056] Figure 23 depicts a diagram of CMOS Sensor Chip image processing;
[0057] Figure 24 depicts a diagram of a routing matrix associated with associated with memory array architecture.
DEFINITIONS USED IN THE INVENTION
[0058] The term "about" means that a value of a given quantity is within ±20% of the stated value. In other embodiments, the value is within ±15% of the stated value. In other embodiments, the value is within ±10% of the stated value. In other embodiments, the value is within ±5% of the stated value. In other embodiments, the value is within ±2.5% of the stated value. In other embodiments, the value is within ±1% of the stated value.
[0059] The term "substantially" means that a value of a given quantity is within±5% of the stated value. In other embodiments, the value is within ±2.5% of the stated value. In other embodiments, the value is within ±1% of the stated value. In other embodiments, the value is within ±0.5% of the stated value. In other embodiments, the value is within ±0.1% of the stated value.
[0060] The term "neutron source" means a device that generates fast neutrons having an having energies between 100 keV and 15 MeV so called fast neutrons. The neutron source may include radio nuclei known to emit neutrons having energies between 100 keV and 15 MeV at a desired flux density. The neutron source may be any device that generates neutrons by bombarding a target with particles having a sufficient energy to generate neutrons having energies between 100 keV and 15 MeV at a desired flux density.
[0061] The term "flux density or flux" means the number of particles passing through an unit area per unit of time. Generally, the flux or flux density is in units of particles/m2s or particles/cm2·s. Specifically, neutron flux or neutron flux density means neutrons/m2·s or neutrons/cm2·s.
[0062] The term "neutron detector" means a neutron detector including a body having a gas chamber, a portion of which is surrounded by conductive plates that define a voltage drift region within the gas chamber and the associated electronics and electrical power systems to charge the plates in a differential manner to produce the voltage drift region.
[0063] The term "logging tool" means an apparatus that is designed to be inserted or dropped into a borehole either as part of a drill string or on a wireline, where the tool includes at least one neutron source and at least one neutron detector and where the tool is capable of detecting and storing data corresponding to formation properties that can be gleaned from detecting neutrons entering the neutron detectors, where the entering neutron may be neutrons scattered, reflected, refracted, and/or reemitted from the formation or formation components.
[0064] The term "at least one", "one or a plurality", or "one or more" all mean that the item immediately following these terms include a single item (singular) or many items and the terms may be used interchangeably in the present specification. Generally, the terms mean from 1 to 100. In other embodiments, the terms mean from 1 to 50. In other embodiments, the terms means from 1 to 25. In other embodiments, the terms means from 1 to 10. In other embodiments, the terms means from 1 to 5. In all of these embodiments, the exact number may be any value between the limits set forth, e.g., from 1 to 100, may be 1, 2, 3, ÿ , 98, 99, or 100 of the designated items.
[0065] The term "real time" means that adjustments are made to fracturing parameters during a fracturing operation without a temporal delay due to downhole data correction, processing, transmitting, and implementing the adjustments.
[0066] The term "near real time" means that adjustments are made to fracturing parameters during a fracturing operation with no temporal delay or substantially no temporal delay due to downhole data correction, processing, transmitting, and implementing the adjustments without a temporal delay due to downhole data correction, processing and implementing the adjustments, where substantially here means that the delay is less than or equal to 2 days. In certain embodiments, the delay is less than or equal to 1 day. In certain embodiments, the delay is less than or equal to 8 hours. In certain embodiments, the delay is less than or equal to 4 hours. In certain embodiments, the delay is less than or equal to 2 hours. In certain embodiments, the delay is less than or equal to 1 hour. In certain embodiments, the delay is less than or equal to 30 minutes. In certain embodiments, the delay is less than or equal to15 minutes. In certain embodiments, the delay is less than or equal to 10 minutes. In certain embodiments, the delay is less than or equal to 5 minutes. In certain embodiments, the delay is less than or equal to 1 minute. In certain embodiments, the delay is less than or equal to 30 seconds. In certain embodiments, the delay is less than or equal to 10 seconds. In certain embodiments, the delay is less than or equal to 5 seconds.
[0067] The term "CFA" means color filter array– R,G,B (red green, blue) typically used to describe a VGA or method for demonstrated data on a computer screen– R-G = red– green and G-B = green blue.
[0068] The term "STE" means stack memory architecture used to move images at high speed thru the computer.
[0069] The term "CMOS" means complementary metallic oxide semi-conductor (a semiconductor technology).
[0070] The term "CIE" means French agency that developed the color chromaticity diagram or color palate.
[0071] The term "ANML" means automata network markup language (the computer language use in the imager software).
[0072] The term "ANDED" means adding a value at a computer memory location.
[0073] The term "TIFFS" means multi layer thin film filters for handing geothermal temperatures down hole.
[0074] The term "nm" means nanometer.
DETAILED DESCRIPTION OF THE INVENTION
[0075] The inventor has found that new downhole nuclear logging, imaging, or detecting apparatuses and systems may be constructed to include a neutron generator subsystem, a neutron detection subsystem, and an analysis subsystem, where each subsystem is in electronic or electrical communication with the other subsystems. The neutron generator subsystem includes at least one neutron source or neutron generating unit capable of generating a neutron flux of neutrons having energies between 100 keV and 15 MeV. The neutron detection subsystem includes at least one neutron detector including a gas chamber containing a mixture of a halogenated gas and a noble gas at an operating pressure and temperature, a detection cage surrounding the gas chamber, and an electrical or electronic unit for charging the detection cage. The cage includes a plurality of conductive rings and electronic or electrical unit is capable of producing a differential electric field in the chamber to define a voltage drift region within the chamber. Neutrons interact with the gas to generate electrons, which are accelerated in the voltage drift region giving rise to detectable neutron- gas events. The neutron-gas events are then detected by the detection subsystem and analyzed by the analyzing subsystem to determine formation properties and characteristics, where the neutron detection event properties and characteristics include directions from which the neutrons enter the chamber, times from bombardment to detection, neutron energies, and other detectable neutron properties, induced electron properties and induced light properties, and where the formation properties and characteristics including thermal neutron cross section (SIGMA), density, porosity, hydrogen index, salinity and photoelectric factor, and other measurable formation and formation fluid properties and characteristics.
[0076] Embodiments of this invention broadly relate to methods including lowering a neutron detection tool into a borehole of an oil or gas well to a location of a formation to be imaged, where the tool includes at least one neutron source, at least one neutron detector, and at least one processing unit, where each detector includes an imaging unit, a gas chamber having a voltage drift region and a voltage unit capable of generating the voltage drift region and where the source and the detector are separated from each other by a distance D1. The methods also include irradiating the location with initial fast neutrons from the at least one neutron source and capturing images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data. The methods also include analyzing the images on a pixel by pixel basis to determine the collision data, converting the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database, producing a logging record evidencing the location solid/liquid/gas data, and classifying the location solid/liquid/gas data. In certain embodiments, the at least one neutron source comprises a single neutron source. In other embodiments, the single neutron source is an 241Am9Be neutron source. In other embodiments, the methods further include conveying the tool within the borehole on a wireline and repeating the irradiating, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole. In other embodiments, the methods further include conveying the tool within the borehole on a drill string, where the tool is situated in the drill string proximate a drill bit section or situated in the drill bit section or collar and repeating the exposing, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole. [0077] In other embodiments, the analyzing step comprises computing a relative location of each collision between an initial fast neutron and a solid, liquid, and/or gas at the location based on the collision data of each gas-returning fast neutron event, calculating an energy of each collision between the initial fast neutrons and the solid, liquid, and/or gas at the location, and modifying each calculation due to interactions between the initial fast neutrons and borehole pipe with or without openings in the pipe. In other embodiments, the solid, liquid, and/or gas at the location are characterized and indexed using a hydrogen index.
[0078] In other embodiments, the initial fast neutrons have energies ranging between 100 keV and 15 MeV and the mixture includes CF4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF4 and between about 99 vol.% and about 99vol.% 4He.
[0079] In other embodiments, each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software. In other embodiments, the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof, the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location, and the processing/analyzing unit is local and/or remote.
[0080] In other embodiments, the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1. In other embodiments, the processing/analyzing unit is remote from the tool. In other embodiments, each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm). In other embodiments, the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location.
[0081] In other embodiments, the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
[0082] Embodiments of this invention broadly relate to methods for creating and capturing an image based on a collision between a gas molecule in a detector and a fast neutron including (a) capturing an image or a plurality of images of each collision between a gas molecule of a gas mixture and a returning fast neutron occurring in a gas chamber of a neutron detector, where the returning fast neutron represents a collision between a solid, liquid, or gas molecule and an initial fast neutron occurring outside of the neutron detector and where each image includes collision data including neutron speed, neutron energetics, neutron entry direction, neutron travel path or track through the detector, (b) determining the collision data on pixel by pixel basis, (c) indexing a precise neutron location of each collision within the detector and relating it to a physical location outside of the detector from which the returning fast neutron entered the detector creating the image or images, and (d) classifying a type of the solid, liquid, or gas molecule from which the returning fast neutron originated based on a comparison to a hydrogen index. In certain embodiments, the initial fast neutrons are generated by a single neutron source. In other embodiments, the single neutron source is a241Am/9Be fast neutron source. In other embodiments, the initial fast neutrons having energies between 100 keV and 15MeV, and the mixture comprises CF4 and 4He a ratio between about 1 vol.% to about 30 vol.% CF4 and between about 99 vol.% to about 70 vol.% 4He. In other embodiments, the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling. In other embodiments, the methods further include updating and/or refining database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
[0083] Embodiments of this invention broadly relate to systems for logging oil and/or gas wells including a neutron detection tool having at least one neutron source, at least one neutron detector comprising an imaging unit, a gas chamber having a voltage drift region and a voltage unit capable of generating the voltage drift region within the chamber, and at least one processing unit, where each detector. The source and the detector are separated from each other by a distance D1, the at least one source irradiates a location with initial fast neutrons, the imaging unit captures an image or a plurality of images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data, the at least one processing unit: (a) analyzes the image or images on a pixel by pixel basis to determine the collision data, (b) converts the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database, (c) produces a logging record evidencing the location solid/liquid/gas data, and (d) classifies the location solid/liquid/gas data. In certain embodiments, the at least one neutron source comprises a single neutron source. In other embodiments, the systems further include a wireline on which the tool is lowered into a well or tripped out of the well or a drill string or drill collar in which the tool is situated for logging while drilling. In other embodiments, the initial fast neutrons have energies ranging between 100 keV and 15MeV, and the gas mixture comprises CF4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF4 and between about 99 vol.% and about 99vol.% 4He. In other embodiments, each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software, the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof, the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location, the at least one processing unit is local and/or remote, and the at least one processing unit update and/or refines the database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data. In other embodiments, the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1. In other embodiments, each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm). In other embodiments, the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location. In other embodiments, the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
[0084] The neutron detection subsystem uses a mixture of non flammable, non explosive gasses. The gas mixtures generally include mixtures of a noble gas such as 4He and a halogenated gas such as CF4 at a desired operating pressure and temperature. Fast neutrons produced by the neutron source are directed at a formation surrounding a borehole of a gas and/or oil well, irradiating or bombarding the formation solids, liquids, and/or gases. A portion of the incident fast neutrons that interact with the formation solids, liquids, and/or gases are scattered, reflected, refracted, and/or otherwise directed back toward the downhole tool or system of this invention entering the detectors of the detection subsystem. Once the returning fast neutron enter the detectors, the returning fast neutrons collide with the noble gases in the gas mixture. The neutron-gas collision events are analyzed based on a speed and direction of the returning fast neutrons. A strength of interaction between the returning fast neutrons and gases in the noble/halogenated hydrocarbon gas mixture corresponds to energetics the electrons resulting from the interactions and the resulting light generated by the scintillation tracks. That is, a portion of the fast neutrons that are directed at the formation surrounding the borehole enter the neutron detectors producing detectable neutron-gas interactions or events. These events are detected producing event images. The event images are then analyzed to provide information concerning the formation and/or formation fluids. In certain embodiments, the neutron source comprises a body in which is disposed an effective amount of 241Am, 252Cf, 9Be, or mixtures or combinations thereof, where the effective amount is adjusted to produce a desired flux of fast neutrons having energies between 100 keV and 15 MeV. Additionally, the body is designed so that the neutron flux may be interrupted.
[0085] In certain embodiments, the apparatuses and systems of this invention are in the shape of a bullet shaped downhole tool, where the detector or detectors are separated from the fast neutron source by a prescribed distance and the returning neutrons from the neutron bombardment creating images in the detectors. The detectors of this system are capable of detecting neutrons entering the detectors from directionally radial direction and any angle, where other neutron detectors are capable of only detecting neutrons coming from a specific cone of incidence.
[0086] Sophisticated software methods and software routines are used to capture image and interpret data associated with collisions between returning fast neutrons after interacting with formation solids and/or formation fluids and gases within the neutron detectors of this invention. The neutron-gas events result in electron production, electron acceleration through a voltage drift region of the chamber and the production of scintillation tracks, which are then detected by cameras such as CMOS/CCD cameras and photomultiplier tubes. These software methods and software routines are then used to produce formation solid and/or formation fluid properties and characteristics.
[0087] The detectors of this invention are uniquely designed so that the detectors are sensitive almost exclusively to interactions between fast neutrons returning from interactions with the formation solids and/or formation fluids. Because the detectors are used underground, the gases are shielded from both gamma radiation and thermal neutrons. Thus, the detectors of this invention are capable of very accurately detecting fast neutron-gas interactions with in the chamber with a low noise level and low occurrences of false positives.
[0088] To calculate the precise locations of the interactions between the fast neutrons and the materials down hole requires: 1) calibration of the detectors; 2) indexing the locations of the detectors relative to the precise measurements, and 3) calculating a precise speed of imaging assembly to enable accurate data capture of all fast neutron-gas events.
[0089] Embodiments of the methods, systems, apparatuses, and interpretative systems of this invention related to logging or imaging while drilling into downhole reservoirs or formations to determine formation solid properties and characteristics and well as properties and characteristics of gaseous and/or liquid hydrocarbons that may be associated with the formation, specifically crude oil and/or natural gas. An external radiation source, typically 241Am (americium) and 9Be (beryllium) is used to generate fast neutrons to bombard downhole formations during oil and/or gas drilling operations. In certain embodiments, a wire line is placed in the hole to control various instruments and the drill assembly. This wire line typically carries bidirectional electrical and data communication lines to instruments mounted on the drill string at various locations during well drilling operations. At a fixed distance from the neutron source, two detectors are placed a proscribed geometrical distance apart from the source to read the interaction between the fast neutrons returning from collisions with the materials in the reservoir. The precise location of the collisions used to describe the materials down hole are mapped and indexed to their specific location. The materials are indexed according to their type using a proprietary set of calculations such as a hydrogen index. To improve the apparatus accuracy the gas in the detectors is formulated to be blind to any other form of radiation used down hole for other purposes such as density calculations. Specifically, the gas detector used in this drilling process is blind to both forms of energy such as thermal neutrons and/or gamma radiation.
[0090] Each detector typically includes a chamber containing a mixture of CF4 and 4He gas at a desired compositional mix, a desired pressure (generally, atmospheric pressures), and a desired operating temperature; a electrical and electronic assembly surrounding the chamber adapted to create an interior drift region within the gas chamber; a remote power supply subsystem and connections thereto; a local power supply subsystem; an external communication link; an electrical data transfer link to a uphole analyzing subsystem used for analyzing and interpreting images of neutron-gas interactions or events remotely and for detector control, imaging control and analysis and a physical connection device connecting the detector to the wireline. The detectors may also include a downhole analyzing subsystem also used for analyzing and interpreting images of neutron-gas interactions or events downhole. These connections may be operated remotely and electronically. The collisions caused by the interaction of the returning neutrons with the gas molecules in the gas chamber produce a streak or image that is interpreted with imaging software a pixel at a time of an imaging system such as a CMOS/CCD camera or other digital imaging system based on pixelated imaging devices. The strength of the collisions and the direction of the returning neutrons interacts generated in the chamber filled with the gas mixture are captured by the sensor or imaging subsystem.
[0091] The detection means uses a mixture of non flammable, non explosive gases. The gas mixtures generally include a noble gas such as 4He and a halogenated hydrocarbon gas such as CF4 or a FREON® gas at one atmosphere. The fast neutron from a neutron generating source returning from bombarding the surrounding geological formation interact with the gas mixture generating light, which is captured by the imaging subsystem. The captured images include information about the direction and energetic of the returning fast neutrons, which is then analyzed to generate information about formation solids, liquids, and/or gases. This information is used to guide the drilling operations.
[0092] The traditional means for bombarding a formation is 241Am and/ or 9Be as the source of the fast neutrons.
[0093] The detection method is located in a bullet shaped tube of a prescribed length and distance from the fast neutron source and the returning neutrons from bombarding the formation creates the image. Two identical fast neutron detectors are located a fixed distance away from the fast neutron source and one detector captures the image from the left side of the bore hole while the other detector captures the image from the other side of the bore hole.
[0094] Sophisticated computer algorithms are used to image and interpret the collisions between the fast neutrons and the material down the bore hole. These computer algorithms are then used to compare the images that are reduced to a look up table comparing the respective hydrogen indices of the material down hole.
[0095] Each detector only looks at the interactions between fast neutrons and the resulting collisions with materials down the hole. Since the detectors are used underground and the gas concentration is blind to the energy level of both gamma radiation and thermalize neutrons the system is very accurate with a low noise level and no false positives.
[0096] To calculate precise locations relating to interactions between initial fast neutrons and the materials downhole requires 1) calibrating detectors, 2) indexing detector locations relative to precise measurements, and 3) calculating a precise speed of imaging enabling accurate data capture.
[0097] A method, an apparatus, and an interpretative system for imaging while drilling down-hole reservoirs of hydrocarbons, specifically natural gas is disclosed. An external radiation source, typically 241Am/9Be is used to generate fast neutrons down the bore hole of an oil or gas well being drilled. A wire line is placed in the hole to control various instruments and the drill assembly. This wire line is typically carrying bidirectional electrical and data lines to instruments mounted on the drill string at various locations while a well drilling is in operation. At a fixed distance from the neutron source, two detectors are placed a proscribed geometrical distance apart from the source to read the interaction between the fast neutrons returning from collisions with the materials in the reservoir. The precise location of the collisions used to describe the materials down hole are mapped and indexed to their specific location. The materials are indexed according to their type using a proprietary set of calculations such as a hydrogen index. One detector is oriented orthogonally to read the left side of the formation while the other detector is oriented in the opposite direction to read the right side of the formation. To improve the apparatus accuracy the gas in the detectors is formulated to be blind to any other form of radiation used down hole for other purposes such as density calculations. Specifically the gas detector used in this drilling process is blind to both forms of energy such as thermalize neutrons or gamma radiation.
[0098] Each detector typically consists of a capsule containing a proprietary mixture of a freon (e.g., CF4) and an inert gas (4He) at a desired temperature and pressure; an amplification circuit and charge amplifier that electronically creates an interior drift region within the gas cell; a remote power system connection; a local battery storage module; a external communication link, an electrical data link to a computer system used for interpretation images remotely and for detector control, imaging control and analysis and a physical connection device connecting the detector to the wore line. This connection may be operated remotely and electronically. The collisions caused by the interaction of the returning neutrons with the gas molecules in the sonde produce a streak or image that is interpreted with imaging software a pixel at a time. The strength of the collisions and the direction from the returning neutrons interact are captured in the sonde filled with the gas mixture.
DETAILED DESCRIPTION OF SYSTEM DRAWINGS
General System Embodiments
[0099] Referring now to Figure 1A, a schematic representation of an embodiment of a neutron detection system, generally 100, is shown to include a surface component 110 and a downhole component 130.
[0100] The surface components 110 includes a surface control subsystem 112, a surface analyzer subsystem 114, a user interface subsystem 116, a power supply subsystem 118 and optionally a surface cooling subsystem 120. The surface control subsystem 112 is in two-way communication with the surface analyzer subsystem 114 via a communication link 122a, with the user interface subsystem 116 via a communication link 122b, and with the surface cooling subsystem 120 via a communication link 122e. The surface analyzer subsystem 114 is in communication with the user interface subsystem 116 via a communication link 120c. The surface power supply system 118 is connected to the other subsystems 112, 114, and 116 via power cables 124, which supply power thereto.
[0101] The downhole components 130 includes a downhole control subsystem 132, a neutron generation subsystem 134, a neutron detection subsystem 136, a downhole power supply subsystem 138, and optionally a downhole cooling subsystem 140. The downhole control subsystem 132 is in two-way communication with the neutron generation subsystem 134 via a communication link 142a, with the neutron detection subsystem 136 via a communication link 142b, and with the downhole cooling subsystem 140 via a communication link 142c. The downhole power supply system 138 is connected to the other subsystems 132, 134, 136, and 120 via power cables 144, which supplies power thereto. [0102] The surface control subsystem 112 is in communication with the downhole control subsystem 132 via a communication link 120d. If the system 100 includes the surface and downhole cooling subsystems 120 and 140, then the surface cooling subsystem 120 includes a coolant delivery conduit 124a and a coolant return conduit 124b, which deliver coolant to the downhole cooling subsystem 140 and receive coolant from the surface cooling subsystem 120. The downhole cooling subsystem 140 supplies coolant to the downhole control subsystem 132 and the neutron detection subsystem 136 via coolant delivery conduits 146a and coolant return conduits 146b. The coolant is adapted to keep the electronic components at a desired temperature. Of course, the coolant may also be circulated to the neutron generation subsystem 134 as well is the electronic associated that subsystem as needs cooling.
[0103] Referring now to Figure 1B, a schematic representation of an embodiment of a neutron detection system, generally 150, is shown to include a surface component 160 and a downhole component 180.
[0104] The surface components 160 includes a surface control subsystem 162, a surface analyzer subsystem 164, a user interface subsystem 166, a power supply subsystem 168 and optionally a surface cooling subsystem 170. The surface control subsystem 162 is in two-way communication with the surface analyzer subsystem 164 via a communication link 172a, with the user interface subsystem 166 via a communication link 172b, and with the surface cooling subsystem 170 via a communication link 172e. The surface analyzer subsystem 164 is in communication with the user interface subsystem 166 via a communication link 172c. The surface power supply system 168 is connected to the other subsystems 162, 164, and 166 via power cables 174, which supply power thereto.
[0105] The downhole components 180 includes a downhole control subsystem 182, a neutron generation subsystem 184, a neutron detection subsystem 186, a downhole analyzer subsystem 188, a downhole power supply subsystem 190, and optionally a downhole cooling subsystem 192. The downhole control subsystem 182 is in two-way communication with the neutron generation subsystem 184 via a communication link 194a, with the neutron detection subsystem 186 via a communication link 194b, with the downhole analyzer subsystem 188 via a communication link 194c, and with the downhold cooling subsystem 192 via a communication link 194d. The neutron detection subsystem 186 is in communication with the downhole analyzer subsystem via a communication link 192e. The downhole power supply system 190 is connected to the other subsystems 182, 184, 186, 188, and 192 via power cables 196, which supplies power thereto.
[0106] Finally, the surface control subsystem 162 is in communication with the downhole control subsystem 182 via a communication link 170d. If the system 150 includes the surface and downhole cooling subsystems 120 and 140, then the surface cooling subsystem 120 includes a coolant delivery conduit 124a and a coolant return conduit 124b, which deliver coolant to the downhole cooling subsystem 140 and receive coolant from the surface cooling subsystem 120. The downhole cooling subsystem 140 supplies coolant to the downhole control subsystem 132 and the neutron detection subsystem 136 via coolant delivery conduits 198a and coolant return conduits 198b. The coolant is adapted to keep the electronic components at a desired temperature. Of course, the coolant may also be circulated to the neutron generation subsystem 134 as well is the electronic associated that subsystem as needs cooling.
[0107] Referring now to Figure 2A, a schematic representation of an embodiment of a neutron detection system, generally 200, is shown to include a control subsystem 202, a user interface subsystem 204, and a power supply subsystem 206. The system 200 also includes a downhole tool 208 including a neutron generation subsystem 210, a neutron detection subsystem 212, and a downhole analyzer subsystem 214. The system 200 may also includes an uphole analyzer subsystem 216. The power supply subsystem 206 is connected to the other subsystems 202, 204, 210, 212, 214 and 216 via electrical connections 218a-f. The subsystems 202, 204, 210, 212, 214 and 216 are in two way communication via communication pathways 220a-h. It should be recognized that not all of the subsystems 202, 204, 210, 212, 214 and 216 are in two way communication with each other, e.g., the neutron generation subsystem 210 is in two way communication with the control subsystem 202, but not necessarily with the neutron detection subsystem 212, not necessarily with the downhole and uphole analyzer subsystems 214 and 216 or not necessarily with the user interface subsystem 204.
[0108] Referring now to Figure 2B, a schematic representation of an embodiment of a neutron detection system, generally 250, is shown to include a control subsystem 252, a user interface subsystem 254, and a power supply subsystem 256. The system 250 also includes a downhole tool 258 including a neutron generation subsystem 260, a neutron detection subsystem 262, a downhole analyzer subsystem 264, and a downhole drilling subsystem 266. The system 250 may also includes an uphole analyzer subsystem 268. The power supply subsystem 256 is connected to the other subsystems 252, 254, 260, 262, 264, 266, and 268 via electrical connections 270a-g. The subsystems 252, 254, 260, 262, 264, 266, and 268 are in two way communication via communication pathways 272a-i. It should be recognized that not all of the subsystems 252, 254, 260, 262, 264, 266, and 268 are in two way communication with each other, e.g., the neutron generation subsystem 260 is in two way communication with the control subsystem 252, but not necessarily with the neutron detection subsystem 262, not necessarily with the downhole and uphole analyzer subsystems 264 and 268, not necessarily with the downhole drilling subsystem 266 or not necessarily with the user interface subsystem 254.
Specific Embodiments of Wire Line Downhole Neutron Logging Tools
[0109] Referring now to Figure 3A, an embodiment of a wire line downhole neutron logging tool apparatus, generally 300, is shown to include a wire line, cable, fiber optic cable or wire 302, an electronic power supply and communication cable 304, and a wire line tool system 306. The wire line tool system 306 includes a housing 308. The housing 308 includes a wire line attachment 310. The housing 308 also includes an imaging subsystem 312, a detection subsystem 314, a fast neutron generation subsystem 316, a communication subsystem 318, and a downhole cooling subsystem 319, which supplies coolant to the electronic components associated with the other subsystems. The housing 308 may also include a downhole analyzer subsystem 320. The detection subsystem 314 includes a detector 322. The detector 322 includes a gas chamber 324, a top electric grid 326, a bottom electric grid 328, a voltage drift cage 330, a bottom plate 332 and a window/lens 334. The tool system 306 also includes mounts 336 for mounting the detector 322 on a support/spacer 338. The fast neutron generation subsystem 316 includes a fast neutron source 340. The support/spacer 338 provides a space between the detector 322 and the fast neutron source 340, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 322. The tool 306 is shown situated in a borehole 342, which may be cased or open, adjacent a formation 344 for which logging data is desired. Coolant is delivered and returns via a coolant umbilical conduits 345.
[0110] Referring now to Figure 3B, another embodiment of a wire line downhole neutron logging tool apparatus, generally 350, is shown to include a wire line, cable, fiber optic cable or wire 352, an electronic power supply and communication cable 354, and a wire line tool system 356. The wire line tool system 356 includes a housing 358. The housing 358 includes a wire line attachment 360. The housing 358 also includes two imaging subsystems 362a&b, two detection subsystems 364a&b, a fast neutron generation subsystem 366, and two-way communication subsystem 368a&b. The housing 358 may also include two downhole analyzer subsystems 370a&b. Each of the detection subsystems 364a&b includes a detector 372a&b. Each of the detectors 372a&b includes a gas chamber 374a&b, a top electric grid 376a&b, a bottom electric grid 378a&b, a voltage drift cage 380a&b, a bottom plate 382a&b, and a window/lens 384a&b. The tool system 356 also includes mounts 386a&b for mounting the detectors 372a&b on support/spacers 388a&b. The fast neutron generation subsystem 366 includes a fast neutron source 390 having a window 391, which opens and closes under the control of the control subsystem. The tool 306 is shown situated in a borehole 392, which may be cased or open, adjacent a formation 394 for which logging data is desired. The support/spacer 388a provides a space between the detectors 364a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 364a&b, while the support/spacer 388b provides a space between the detectors 364a&b and the fast neutron source 390, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 364a&B.
Specific Embodiments of Drilling and Neutron Logging Tools [0111] Referring now to Figure 4A, an embodiment of a drilling and neutron logging tool apparatus, generally 400, is shown to include drill string 402, an electronic power supply and communication cable 404 extending along an outside 403 of the string 402, and a drilling and logging tool system 406. The tool system 406 includes a housing 408. The housing 408 includes a drill string coupler 410. The housing 408 also includes two imaging subsystems 412a&b, two detection subsystems 414a&b, a fast neutron generation subsystem 416, and two-way communication subsystem 418a&b. The housing 408 may also include two downhole analyzer subsystems 420a&b. Each of the detection subsystems 414a&b includes a detector 422a&b. Each of the detectors 422a&b includes a gas chamber 424a&b, a top electric grid 426a&b, a bottom electric grid 428a&b, a voltage drift cage 430a&b, a bottom plate 432a&b, and a window/lens 434a&b. The tool system 406 also includes mounts 436a&b for mounting the detectors 422a&b on support/spacers 438a&b. The fast neutron generation subsystem 416 includes a fast neutron source 440. The tool 406 is shown situated in a borehole 442, which may be cased or open, adjacent a formation 444 for which logging data is desired. The housing 408 also includes a drilling subsystem 446. The drilling subsystem 446 includes a drill control unit 448 and a drill bit apparatus 450. The support/spacer 438a provides a space between the detectors 414a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 414a&b, while the support/spacer 438b provides a space between the detectors 414a&b and the fast neutron source 440, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 414a&b.
[0112] Referring now to Figure 4B, another embodiment of a wire line downhole neutron logging tool, generally 400, is shown to include drill string 402, an electronic power supply and communication cable 404 extending along an outside 403 of the string 402, a drilling and logging tool system 406. The tool system 406 includes a housing 408. The housing 408 includes a drill string coupler 410. The housing 408 also includes two imaging subsystems 412a&b, two detection subsystems 414a&b, a fast neutron generation subsystem 416, and two-way communication subsystem 418a&b. The housing 408 may also include two downhole analyzer subsystem 420a&b. Each of the detection subsystems 414a&b includes a detector 422a&b. Each of the detectors 422a&b includes a gas chamber 424a&b, a top electric grid 426a&b, a bottom electric grid 428a&b, a voltage drift cage 430a&b, a bottom plate 432a&b, and a window/lens 434a&b. The tool system 406 also includes mounts 436a&b for mounting the detectors 422a&b on support/spacers 438a&b. The fast neutron generation subsystem 416 includes a fast neutron source 440. The tool 406 is shown situated in a borehole 442 adjacent a formation 444 for which logging data is desired. The housing 408 also includes a drilling subsystem 446. The drilling subsystem 446 includes a drill control unit 448 and a drill bit apparatus 450. The housing 408 also includes a gamma ray detection subsystem 452. The gamma ray detection subsystem 452 includes two gamma ray detectors 454a&b and a gamma ray source 456 and two support/spacers 455a&b. The support/spacer 438a provides a space between the detectors 414a&b by a distance to optimize or differentiate between the fast neutrons returning to the two detectors 414a&b, while the support/spacer 438b provides a space between the detectors 414a&b and the fast neutron source 440, where the space is a distance or gap that optimizes an incidence of returning fast neutrons onto the detector 414a&B. The support/spacer 455a provides a space between the gamma ray detectors 454a&b by a distance to optimize or differentiate between the fast neutrons returning to the two gamma ray detectors 454a&b, while the support/spacer 455b provides a space between the gamma ray detectors 454a&b and the gamma ray source 456, where the space is a distance or gap that optimizes an incidence of returning gamma rays onto the gamma ray detector 454a&B.
[0113] All of the other embodiments described above may include a surface cooling subsystem and a downhole cooling subsystem, which may provide coolant to the electronic components of the other subsystems.
Neutron Penetration Profiles of Neutron Logging Tools
[0114] Referring now to Figure 5, an illustrative depiction of fast neutron detection is shown using a wire line neutron detection tool system 500 including a wire line attachment 502, a housing 504 and a first neutron detection subsystem 506 and second neutron detection subsystem 508. The first neutron detection subsystem 506 includes detectors D11 and D12 and a fast neutron source N1, while the second neutron detection subsystem 508 includes detectors D21 and D22 and a fast neutron source N2. The system 500 is attached to a wire line, cable, fiber optic cable or wire 510 via the attachment 502 connected to or integral with the housing 504. The wire line , cable, fiber optic cable or wire 510 also include a electronic power supply and communication component (not shown) for supply power to the detectors and other controllable components as well as providing control and data transmission functions. Fast neutrons are emitted by the sources N1 and N2. The fast neutrons from the sources N1 and N2 penetrate into the formation to a total penetration depths of d3 and d6, where the depths d3 and d6 may be the same or different depending on the nature of the neutron emitted by the sources N1 and N2, which may be the same or different type of sources. The total penetration depths d3 and d6 give rise to two different types of formation and/or formation fluid responses. In first portions d1 and d4 of the total penetration depths d3 and d6, neutron are scattered, reflected, and/or refracted from a borehole surface and/or near surface of a borehole 512 as represented by the penetration depths d1 and d4. In second portions d2 and d5 of the total penetration depths d3 and d6, neutron are scattered, reflected, refracted, and/or absorbed and reemitted from formation solid, formation gasses, and/or formation liquids deeper in the formation in the second portions d2 and d5 of the total penetration depths d3 and d6. The system 500 is lowered into the borehole 514 relative to a center line 514, where the borehole 514 extends from a surface assembly 516 of a ground surface 518 into a formation 520 to be logged. Because the system 500 includes two detection subsystems 506 and 508, two portions 522 and 524 of the formation 522 may be simultaneously logged.
ENERGY, MATERIALS, AND RADIATION SOURCES
Using Fast Neutron Sources as a Penetrating Radiation Sources
[0115] Gamma radiations, X-rays and thermal neutrons have been used as water logging sources while penetrating bore holes. Only thermal neutron sources are generally used for this task. We are aware of no effort using fast neutron sources as nuclear imaging sources for imaging while drilling. We have overcome several of their technical constraints in our new design. Logging probes have been used to assay materials down hole. These probes are generally small in diameter and like our invention have proven their value over time and careful study. Current industry practice for core samples follow the bore hole material model described here.
[0116] Probes generally vary with bore hole diameter. The Petroleum industry demonstrated that the shape of the hole matters when it is interrogated with gamma sources. Various drilling techniques are used depending upon the rock type or lithography. Percussion type drilling creates holes that are determined by the rock strain. Variation of grades of ores from place to place has been extensively studied. The Matheron variogram, for example, has become the basic tool of geostatistics of the natural variability of a region variable set such as are grade. It is defined as:
Figure imgf000026_0001
where (xi) is the grade at a point xi and G(xi+ h) is the grade at a point h units of distance away, N is the number of paired observations.
[0117] Larger scale irregularities across a bore hole cross section caused by changes in rock composition, drill pressure fractured or fissured zones are investigated using bore hole calipers. Hole stability is affected by soft dirt and rocks. The bore hole can simply collapse imposing design changes to a logging probe. Unimpeded passage uphole or down requires simple, streamlined and pressure resistant shell configuration of minimum length in proportion to the diameter of the hole being drilled. Gamma radiation or X-ray sources cannot even penetrate even thin layers of extraneous material or Simple fluids may surround a drilling apparatus defeating its ability to tell the operator much about the material surrounding the hole. Satisfactory transmission of low energy radiation through several centimeters of even clear water is not feasible until energies exceed 50 keV to 100 keV.
[0118] The extraction of information from down the hole while drilling an oil well presents substantial room to maneuver creates a different set of economics for the drilling industry. In the petroleum industry the hole size may vary from 150 mm to 400 mm at a depth typically of from 0.5 m to 5000 m. The drill bit at this depth encounters all types of rock hardness and types as the drill punches deeper into the well. The whole spectrum of rock types from sentiments to extremely hard rock deposits are encountered as well as hole full of various viscosities of fluids from water to drilling fluids. The only constant is that the lithography varies from hole to hole. The volume of the cylindrical shell of rock probed and then drilled is proportional to the energy of the energy source and the nature of the rock materials being penetrated. The bulk sample penetrated by gamma radiation is calculated as:
Figure imgf000027_0001
where t½ is the thickness needed to reduce the transmission through a material with total linear gamma-ray coefficient m to the value of one half. If follow from this formula that
Figure imgf000027_0002
[0119] Gamma radiation transmitted through 1, 2 or 3 half thickness values of a given material thus falls to 50%, 25% an 12.5% respectively of its initial intensity I0 and very little (< 2%) of such radiation is received at a detector after the primary radiation has been attenuated by six half thicknesses of material between it and the source. For 5 MeV primary gamma radiation these values range from 14-27 centimeters for dense are materials to 54 centimeters for average rock. At 1 MeV corresponding figures are 8-15 cm and 24 cm, while for 100 keV radiation corresponding values drop for dense mineral material to 3 cm or less and to some 8.6 cm for average rock. The presence of homogenous distributed heavy materials reduces values for host rock on a pro rata basis. Gamma radiation therefore provides little information about the characteristics of minerals away from the immediate bore hole. We can use the same formula relationships to calculate the penetration power of fast neutrons.
[0120] A typical percussion drill hole with the smallest diameter of a gas collection pipe with a radius of 5.8 cm (58 mm) (2.8") allows a radiation penetration of only 5 centimeters is sufficient to probe a volume approximately 2.5 times that of the corresponding core; for 15 cm penetration, the corresponding penetration· is a factor of 12 times or 6'. For average rock penetration at 5 MeV is capable of probing 70 such core volumes with an equivalent type of rock. With dense materials such as haematite, core volumes probed in this size hole are greatly diminished. The actual depth of rock from which information can be gathered varies with the type of core log employed.
What is the relationship between the Core Assay and Bulk Sample Assay?
[0121] If the rock type were spatially distributed around the bore hole in a totally homogenous fashion there would be no significant difference between assays of core and the surrounding cylindrical shell if sample errors and chemical analysis errors were taken into consideration. The comparison of the actual geological features at depth when compared with simulated values, while a hole can be probed are subject to the hole radius, the shell radius, the core volume, the shell volume and the ratio of the shell/core volumes. Typical shell volume comparison measures below are measured in centimeters. Large radius holes lead to large radius core samples but they still reflect relatively close proximity to the hole itself and do not lend themselves necessarily to an interpretation to sites further away from the bore hole. A fast neutron imager with a higher energy source that can penetrate further from the hole tells us more about the location of oil deposits and whether they are in gas or liquid form. This information must be interpreted from information about either the resulting characterization of the drilling fluids or the porosity level of the soil types permeated by water. Sam le relationshi s:
Figure imgf000028_0001
[0122] Notes: Distance and direction are spatially dependent. Geovariance affects outcomes; every formation is different. The three sources of error in core samples are 1) the error in sampling proper; 2) quartering due to improper mixing; 3) the error in chemical assaying. Each can contribute to different types of analytical error. Each sample is affected by the logging speed. For determining the geological whether it is by core sample or analyzing any core sample while drilling, the problems whether it is conducted while drilling or after the fact always includes the following design engineering challenges:
1) making equipment miniaturized to go into the hole;
2) use of radiation sources and windows strong enough and durable enough to
resist radiation, the pressures from the rock or fluids down the hole;
3) physically robust enough detectors given the downhole pressure and
temperatures;
4) high performance enough electronics to gather the data so as not to impede the
drilling process;
5) communication speed up/down out of the hole operator;
6) knowing the proper location of the formation being imaged;
7) a robust method for calculating errors.
In continuous logging while drilling, the precision is dependent upon statistical precision. In practice logging speeds greater than 1-2 meters per minute for assays gathered while drilling in the 1-5% range from the hole are less expensive than the current core array method currently being utilized.
Neutron Radiation Imaging Model Factors
[0123] We have developed a complete practical approach comparing simulated values of neutron radiation penetration in bore holes and the description of neutron probe calibration and response in soil and rocks. Thermal neutrons have been used since the 1960's to determine porosity or the presence and location of the water table depth in the bore hole. Probe spacing from the source is extremely important for careful calibration of the detection system. Long probe spacing enables the probe to image a greater distance from the hole. The geometry of the source to the detector is extremely important. Formerly, neutron logging results were limited to elements with large thermal adsorption cross sections. One cannot ignore bore hole diameter effects.
[0124] Factors contributing to an accurate measurement: 1) Bore hole diameter; 2) Bore hole shape; 3) Presence of water; 4) Strength of energy source; 5) Number of detectors; 6) Distance between the fast neutron source and each of the detectors; 7) Spacing between the source and the detector; 8) the presence of other elements in the hole.
Advanced Work
[0125] We have developed an interpretation of the geometry across a cross section of elements and geological properties for making a determination for interpreting fast neutron responses for something other than water. Parameters for the construction of an imaging data base using fast neutrons may be characterized against existing standard rock models maintained by the industry. We have further developed calculation of the instrument responses from neutron parameters as already described using mathematical models to create physical parameter data as one approach for characterization of formation properties. Field calibrations and interpretation of geological properties in digital form may be based on the construction of a data base when using the instrument over time further enhancing its historical value. Creating multiple regressions for gaging the response to deposits could be represented by the expression:
Material (iron for example)
Figure imgf000029_0001
Yielding a Correlation Coefficient for Iron in a Drill Hole Core Section
[0126] With the measurement of a small c ratio and the addition of our knowledge about the percentage of fluids and water the driller may make intelligent decisions about the direction of drilling. Such calculations for gamma ray logging and detection and elemental estimation already exists. Fast neutron calibration and spectral window for high energy fast neutrons can be an extension of this existing scientific approach giving us one more tool to analyze a deposit without the delay of having to physically core and interpret a sample in our well located either in proximity to two extremes where exploration is close to population centers or conversely the severity of the drilling environment may be physically challenging to human operation.
Specific Embodiments of Direction Downhole Neutron Detectors
[0127] Referring now to Figure 6A, an embodiment of a directionally sensitive neutron detector, generally 600, is shown to include a gas chamber 602 having a gas chamber interior 604 filled with a gas mixture 606. The gas mixture 606 is effective to interact with incident fast neutrons n and to generate scintillation light due to the interaction between the neutrons n and molecules in the gas mixture 606. The gas mixture 606 is tunable via gas supply lines, gas delivery assemblies and gas sources shown in Figure 6B below. The ability to tune the gas mixture composition permits on the fly optimization of gas composition, pressure, and/or temperature based on the type of neutrons n being detected.
[0128] The detector subsystem 600 also includes a detector assembly 608. The detector assembly 608 includes a plurality of flattened conductive rings 610 separated by a plurality of ring insulation and resistor assemblies 612 including a ring insulator 612a and a ring resistor 612b. The detector assembly 608 also includes a top grid 614 and a bottom grid 616. The detector assembly 608 also includes a bottom plate assembly 618 supporting the bottom grid 616 via bottom plate insulators 620. The detector assembly 608 is connected to the power supply subsystem 622 via an input wire 624 and an output wire 626. The potential difference across between the grids 616 and 618 is controlled by the power supply subsystem 622 and the insulation disk and resistor assemblies 612 control a step wise change in the potential difference at each of the rings 610 as one traverse down the chamber 602 from the top grid 616 to the bottom grid 618. This potential difference operates to permit the detector assembly 608 to react to incoming a neutron n generating electrons that are accelerated toward the bottom grid 618 generating light detected by a sensor subsystem 628.
Sensor Subsystem
[0129] The sensor subsystem 628 includes at least a CCD camera or a CMOS sensor 630, photomultiplier tubes 632 and a sensor window/lens assembly 634. The camera 630 and the photomultiplier tubes 632 are used to detect the neutron n events recording the tracks, which is analyzed to generate neutron event data including neutron entry energy, neutron entry direction, and other neutron interaction data. The sensor subsystem 628 is connected to the power supply subsystem 622 via an input wire 636 and an output wire 638.
Processing Subsystem
[0130] The system 600 also includes a processing subsystem 640, which is connected to the power supply subsystem 622 via an input wire 642 and an output wire 644. The processing subsystem 640 controls the charging of the detector assembly 608 and controls the capture and storage of images of the neutron gas interactions or neutron detected events detected by the sensor subsystem 628. The processing subsystem 640 may also include software for performing preliminary analysis of neutron detected events. The processing subsystem 640 is in two way communication with the detector assembly 608 via detector assembly communication pathway 646 and with the sensor subsystem 628 via sensor subsystem communication pathway 648.
Coolant Unit
[0131] The system 600 also includes a coolant subsystem 650 having a coolant delivery conduit 652 and a return coolant conduit 654. The subsystem 650 is in thermal contact with the photomultiplier tubes 632 and the camera or sensor 630. The coolant cools the subsystem 650, which in turn cools the photomultiplier tubes 632 and the camera or sensor 630.
Gas Chamber
[0132] Referring now to Figure 6B, a schematic representation of an embodiment of the gas chamber 602 include a 4He valve 660, a 4He delivery line 662, a 4He source 664 and a 4He flow controller 666. The gas chamber 602 include a CF4 valve 668, a CF4 delivery line 670, a CF4 source 672 and a CF4 flow controller 674. The gas chamber 602 may also include a 3He valve 676, a 3He delivery line 678, a 3He source 680 and a 3He flow controller 682. The 4He valve 650, the 4He flow controller 656, CF4 valve 658, and the CF4 flow controller 664 are controlled by the processing subsystem 640. If the gas mixture 606 also includes 3He, then the 3He valve 666 and the 3He flow controller 672 are also controlled by the processing subsystem 640.
Detection Methodology Illustrated
[0133] Referring now to Figure 7, represents a side section view of a schematic representation of the detector system 700. The detector chamber 600 encloses a volume oriented in the z direction per a Z axis, which defines a generally axial direction of the detector system 700. In certain embodiments, the detector system 700 may be generally of a cylindrical shape and thus has a circular cross section orthogonal to the Z axis.
[0134] The detector system 700 includes a "field cage" having a plurality of stacked, spaced-apart conductive rings 702 orthogonal to the Z axis, along with an upper wire mesh or upper grid 704 at the top of a relatively large drift region 706. At the lower end is a lower wire mesh or lower grid 708 and a closely spaced conductive plate 710, which together define a much smaller amplification region 712. Voltages are applied as described below to establish a first, relatively low electric field in the drift region 706 and a second, relatively high electric field in the amplification region 712. An imaging system 714, which in the illustrated embodiment includes a lens 716 as well as a light sensitive component 718 such as charge-coupled device (CCD) imaging unit, a cooled CCD imaging unit, a CMOS imaging unit, etc., located outside the upper end of the detector chamber 700. The detector may also include photomultiplier tubes (PMTs) 720 also at the upper end, two of which are shown in Figure 7. The function of the PMTs 720 is described below.
[0135] Here the field in the drift region 706 is established by the combination of a ground potential on the lower grid 708 and a negative potential V drift applied to the upper grid 704 and the uppermost ring 702t. A series of resistors 722 serve as a voltage divider network to distribute the voltage V drift across the rings 702. In one embodiment, the voltage V drift is -2500 volts, and the resistors 722 provide generally equally spaced voltages in the range between -2500 and 0 to the rings 702. As a simplified example to illustrate, if six rings are used then the sequence of ring voltages progressing downwards is -2500, -2000, -1500, -1000, -500 and 0. In a system it is expected that a larger number of rings (e.g., 20 to 30 or more) will be used to provide desirable spatial uniformity in the electric field within the drift region 706.
[0136] The field in the amplification region 712 is established by the combination of the ground potential on the lower grid 708 and a high positive potential Vamp applied to the plate 710. In one embodiment the voltage Vamp is +620 volts and the spacing between the lower grid 708 and plate 710 is 0.5 millimeters.
[0137] It will be appreciated that the electric fields are established by the relative voltages of the various elements. In alternative embodiments it may be convenient to apply the ground potential to another conductive node of the field cage.
[0138] In operation of the detection system 700, neutrons n entering the drift region 702 collide with He atoms of the gas mixture, each collision causing a recoil of a struck He nucleus in generally the same direction as the incident neutron. The large cross section at 1 Me V and the generally faithful agreement of the recoil direction with the neutron direction is due to the nuclear reaction of neutron + 4He proceeding through a resonant state of 5He. The recoiling He nucleus induces ionization along a short path or track of travel in the drift region 706. The free electrons generated by the ionization are directed toward the amplification region 712 under the influence of the field in the drift region 706 (shown generally as drifting electrons 724). As the electrons pass through the lower grid 708 they are accelerated by the high field in the amplification region 712. The accelerated electrons undergo avalanche multiplication which is accompanied by scintillation (emission of light) of CF4 along paths in the amplification region 712, which are referred to as "scintillation tracks". The sensor subsystem 714 together with a processing subsystem (not shown here, but shown in other figures) generate two- dimensional (2D) and three-dimensional (3D) images of these scintillation tracks and process the images to identify those tracks generated by neutrons of interest, differentiated from other types of tracks and from other artifacts that may be created in operation.
[0139] It will be observed that the ionization track of the recoiling He may have a Z-direction component, which is not reflected in the path of scintillation occurring in the plane-like amplification region 712. In some embodiments the two-dimensional information from the scintillation tracks alone may be sufficient for identifying the direction of incident neutrons. However, in other applications it may be desirable to obtain information regarding the Z component of the ionization track. The PMTs 720 may be used for this purpose. The PMTs 720 are fast-response devices that provide an electrical output pulse for each scintillation, with the pulse duration being equal to the duration of the scintillation. To a first approximation, the duration of a pulse from a PMT 720 is directly proportional to the Z component of the ionization track whose scintillation light caused the pulse. By correlating the pulse shapes from the PMTs 720 with the appearance of scintillation tracks in the images obtained from the sensor subsystem 714, the processing subsystem can include the Z component in its estimation of neutron direction. As described in more detail below, the estimation of direction is also based on the shape of the scintillation tracks.
[0140] The system 700 also may also include coolant units 724a-c. Each coolant unit 724a-c includes a coolant delivery conduits 726 and a coolant return conduit 728. The coolant units 724a-c are in thermal contact with the photomultiplier tubes 720 and the imaging unit 718, where the coolant cools the photomultiplier tubes 720 and the imaging unit 718 electronic.
COMPUTER AND SOFTWARE SUBSYSTEM
Theory of Operation
[0141] Embodiments of this invention relate to imaging methods and systems that include a sensor or tool subsystem, where the systems are adapted to image, detect, diagnose, and/or identify properties of a borehole penetrating subterranean formations and/or zones thereof. The systems may be used in both open or cased boreholes. In certain embodiments, the systems and methods are configured to: 1) evaluate a formation or a zone thereof; 2) determine wellbore integrity; and 3) map fluid movement during production/injection. In certain embodiments, the sensor or tool subsystems are attached on a wireline having a power cable that provides power to the sensor or tool subsystem and a data cable that enables bidirectional communication between the sensor or tool subsystem and a surface control and analyzer subsystem. In other embodiments, the sensor or tool subsystems are attached in a slickline and dropped or lowered into a borehole. In other embodiments, the sensor or tool subsystems are incorporated into on a drill string so that data may be collected while drilling. In certain embodiments, the sensor or tool subsystems collect formation data and then send the data to the surface for the analysis. In other embodiments, the sensor or tool subsystems collect and pre- process or analyze formation data and then send the pre-processed and analyzed data to the surface for further analysis. In other embodiments, the data is retrieved from the sensor or tool subsystems after the sensor or tool subsystems are pulled from the borehole as the sensor or tool subsystem includes memory sufficient to store the data. The collected and analyzed data is used by operator personnel to: (1) adjust the course of drilling, (2) identify formation or zone properties, and/or (3) identify formation or zone fluid properties (types and amounts of fluids).
[0142] In certain embodiments, the sensor or tool subsystems include at least one fast neutron source and at least one fast neutron detector. The neutron detectors take advantage of the scientific principals of neutron emission spectrometry. The neutron generator(s) or source(s) is(are) positioned on the sensor or tool subsystems to irradiate the formation with fast neutrons, while the neutron detector(s) is(are) positioned on the sensor or tool subsystems to detect fast neutrons incident thereon. During or after irradiation, a certain portion of the fast neutrons interact with the formation materials (solids, liquids, and/or gases) and return towards the detector(s), and a portion of these returning neutrons enter the neutron detector(s). The neutrons entering the detector(s) and evidencing fast neutron formation interactions or collisions are captured by the detector(s). Each detector includes a gas mixture designed to interact with returning fast neutrons generating electrons, which drift through an electron drift chamber. These electrons generate light focused onto a dark field of an imagining unit of each detector. In certain embodiments, each imagining unit also includes a prism that separates the generated light into its spectral components. The spectral components are focused onto a dark field with colored lines that correspond to the electron transitions resulting in the light emission. Given the color or frequency of light emitted, software is used to analyze the energetics of the collisions. The electrical discharges create images called tracks and are captures or collected by the detector(s) and analyzed by the software. The images or tracks are then sorted, analyzed and correlated with solids, liquids, and/or gasses, which correspond to energies of the detected neutrons that include information about the fast neutron-formation component interactions.
[0143] The detectors in the sensor or tool subsystems are designed to improve the quality of available information about formations and any gasses or liquid in the formations providing enhanced information during drilling operations. The information may be gathered during down times or in real time or near real time while drilling. The exact information collected by the sensor or tool subsystems will depend on the information needed and on the configuration and types and numbers of detectors and sensors present on a particular sensor or tool subsystem. The sensor or tool subsystems are generally controlled by a control subsystem including processing units. The control subsystems may include a local (tool based) processing unit, a remote (surface based) processing unit, or a combination of local and remote processing units. These processing units are adapted to control the operation of hardware and software components in the sensor or tool subsystems. In certain embodiments, the local or tool-based processing unit may simply collect and store the images. In other embodiments, the local or tool-based processing unit may collect, store and transmit the images to a remote processing units for data analysis. In other embodiments, the tool-based and remote processing units are used in data analysis. The hardware components of the sensor or tool subsystems include at least one conventional fast neutron generator or source, at least one neutron detector of this invention, and software components that detect, capture and analyze the detected and captured data to generate formation information during drilling operations and/or while drilling.
[0144] The data collected by the sensor or tool subsystems corresponds to photographic and/or spectroscopic data associated with elastic and/or inelastic collisions between fast neutrons emitted by the neutron source and the formation or formation components that have a direction toward the sensor or tool subsystems (returning neutrons) in real time or near real time. These collisions are interpreted producing specific data concerning the formation and the formation components. The detectors in the sensor or tool subsystems capture images, tracks and/or events corresponding to collisions between returning fast neutrons and a gas mixture in the detector before the neutrons thermalize. The returning fast neutrons comprise reflected, refracted, scattered, or any other fast neutron that traveling back towards the sensor or tool subsystem after interacting with the formation components (gases, liquids, and/or solids). In certain embodiments, the sensor subsystems and analysis subsystems are implemented to exclude captured collisions that do not meet a threshold energy value, e.g., neutrons that have thermalized to the extent that insufficient information is readily ascertained. In certain embodiments, the threshold energy excludes neutron having energies below about 100 keV. In other embodiments, the threshold energy excludes neutron having energies below about 0.5 MeV. In other embodiments, the threshold energy excludes neutron having energies below about 1 MeV.
[0145] An example of neutron energy states in electron volts (eV) after generation and collision may be summarized as follows. Initial fast neutrons having energies of about 4.5 MeV produced by a neutron source irradiate a formation or formation zone. A portion of these neutrons are elastically and/or inelastically scattered in a direction back towards the sensor or tool subsystems, where a portion of these neutrons enter the detector. The scattered neutrons have energies between about 2.5 MeV and about 100 keV, and are commonly referred to a epithermal neutrons– neutrons having an energy $100 keV. If these ethermal neutrons are not detected soon after production, they thermalize producing thermal neutrons having energies between about 100 keV and about 10 eV, but below 100 keV. Alternatively, the detectors are designed to detect neutron having an energy between about 4.5 MeV and greater than about 100 keV, while rejecting neutron energies less than about 100 keV.
[0146] It is a characteristic of fast neutrons that they non-destructively penetrate further than any energy source and even penetrates through most of the materials found in the borehole such as casing, cement, and/or steel drill pipe. The sensor or tool subsystems or analyzing subsystems detect and create three dimensional images or tracks without regard to the geometry of the borehole. From experiments, it can be shown that the sensor subsystems or tools creates a two or three dimensional image generally shaped as a cylinder with a resolution up to thirty meters from the center line of a bore hole in an x, y or z direction. Generally, most of the current indirect measurement systems used on wirelines down hole have a resolution of no more than up to 2 feet from the centerline of the bore hole.
Configurations
[0147] The present sensor or tool subsystems can be deployed in one of two embodiments; 1) either in a stand-alone mode or 2) operated on a wire line over a fiber optic cable creating a networked environment. The system operation, retrieval speed and recovery of the track images created by the spectrometer are dependent upon the form of its preferred embodiment. In stand-alone mode, the imager’s power is self-contained and its operating performance is limited by the size of its battery power. The imaging system capturing the collisions is self-contained and the imaging system module is subsequently recovered when the imager is pulled up the drill string and removed from out of the ground. The second embodiment enables real-time image capture by the use of a computer system and display console tethered up on a drilling platform linked to the imager over a combination fiber optic/power cable that is connected to a power source out of the bore hole. This second embodiment enables the driller to image while drilling with an operational delay proportional to the length of the data cable between the image detector below ground and the operating console/computer on the platform.
Computer System Component
[0148] The computer system functions operating the sensor or tool subsystems of this invention contain an industry standard operating system, software imaging interpretative applications, an image compiler, and removable data storage. It is designed to be self-contained and requiring only periodic scheduled maintenance. The data from the imager is formatted to be used on standard interpretative software packages for later evaluation and use by the drillers and geologists. A display device/monitor is configured with the computer for use as an interface to a human operator. An operator familiar with a basic personal computer can operate the display component and computer system associated with the sensor or tool subsystems of this invention. Specific graphical visual information is provided to the user so that the geologist or an untrained drilling operator does not need to undergo specialized training to interpret the images created by the present imaging tool.
[0149] Additionally, the computer system provides each of the operational functions for system initialization, self-test and tool operation. The system is ruggedized for use in an outdoor environment. The computer system is networked; in this network configuration, it can be configured for remote communications operation with a module containing a data link for data transmission, tool control and remote data analysis.
Computer System Software Component
[0150] The Computer System has a hierarchical set of resources that provides all of the operating controls of the sensor or tool subsystems. This includes system initialization, self-test, data collection and analysis modules. The methods of operation of the system and the processing subsystem are illustrated in Figures 8, 9A-D and 10A-B and the accompanying text.
[0151] A software package of this invention resides on the computer system. The package has a generic stand-alone operating system and is designed to manage the system's hardware tool resources. The software applications are specifically designed to interpret, capture, display and store the information generated from the present neutron imaging component during its downhole operation. This information is put into a Microsoft Excel™ 2010 spreadsheet format for manipulation and subsequent analysis.
[0152] The algorithms coded for interpretation of the data are described herein. Three hardware components are required for imaging to take place.1) The neutron source must be "on". The imaging tool must be correlated to the neutron source. 2) The tool must be initialized to the information control system.3) The computer system that controls the tool must be initialized to the tool and the neutron source for creation of the imaging data base. The software components used by the system document the interaction between the neutron source, the geological (rock) formation and other and the second module containing the sensor or tool subsystems of this invention. The imaging steps create a data base of information about the rock formation in the following order:
1. Initialization: Fast neutrons are released from the first module near the well bore surface and the tool located in the second module goes through a calibration routine. Handshaking occurs between the digital computer and the tool during the initialization step.
2. Data Base: A data base including an architecture resident on the computer component of the systems. The database stores system operating parameters and captured track data representing the collisions that have occurred between the geological formation and the fast neutrons released by the neutron source.
3. Image Capture: The returning fast neutrons, moderated by these collisions with formation solids, liquids, and/or gases, are captured as "tracks" or images created when the returning fast neutrons strike or collides with atoms of the penning gas in the gas chamber of the detectors in the downhole tool. An imaging unit (e.g., a charge coupled device (CCD)) continuously captures the images or tracks. The images or tracks include neutron event data including energetic data, directional data, time data, location indexing data, etc. associated with each detected collision between atoms of the penning gas and the returning fast neutrons.
4. The event data are then correlated or interpreted using a CIE Chromaticity index using software residing in the analyzing subsystem of this invention and collected and stored in an image data base. In certain embodiments, the event data are stored sequentially, but the event data may also be stored randomly indexed so that sequential data analysis may be performed.
5. In certain embodiments, the database contains continuously captured event data comprising tracks or images including color/hue/intensity data and directional data. The continuously captured data may be continuously correlated using analysis software associated with the database that compares the capture event data with event data associated with known data either from know geological formations or from simulated data of different solids, liquids, and/or gases. Over time, the system "learns" from collected and analyzed event data relating to whole sample geological structures based on the analysis of the images or tracks created by the returning neutron collision data and improves and/or refines event data in the database so the interpretation can be improved.
6. Once the capture event data is correlated using the database, it is then converted into output data, such as an Microsoft Excel™ spread sheet, that contains both the interpreted event data and an identifier containing the location from where the event data was captured. The output data may be in the form of a map of the borehole showing the type of solids, liquids and/or gas collected during the logging operation. 7. The captured event data about the formation is recorded and converted into graphic information that is then transmitted out of the hole and up to the driller's user interface.
8. Here the geological information is tied to the location information. The driller may then adjust the drilling sweet spot based on the images coming from the graphical user interface coming continually from the updated imaging or track data base.
9. The newly captured and subsequently interpreted event data is digitally linked with other data captured during the drilling operation from other tools that is specific to the current formation being drilled and the resulting data is transmitted over a communications link to a remote location for real-time geological interpretation and analysis.
10. The color/hue/intensity event data are color coded which represents a proportional relationship between the strength of the interaction between the initial fast neutrons and the geological elements identified and continuously measured the borehole during logging operation or during logging while drilling operations. Color decoding used to decode the data represented by the track images is described more fully below in Figures 11-16.
[0153] The detectors of the systems of this invention are analytical spectrometers that capture fast neutron-penning gas collision images or tracks that include neutron event data that are passed to the analysis subsystem where software analyzes and interprets the event data producing formation solid, liquid, and/or gas properties and/or characteristics. The systems of this invention are designed to be used in open boreholes and/or cased boreholes during drilling, during wire line operations, or during any other operation where a tools in capable of being inserted down hole. The tools may be dropped downhole on a wire line or may be a tool in the drill string. Generally, the diameter of an open borehole or the drill pipe is between 2 and 9 inches. Thus, in those embodiments where the tool is dropped down an open borehole or down a drill string, the minimum diameter of the tools of this invention are about 1and 11/16 inches so as to clear the inside of a 2 inch diameter drill pipe or borehole. The maximum diameter of the tool of this invention are about 8.5 inches so that the tool passes through a drill pipe or borehole having a 9" diameter. The tools of this invention are designed to have an appropriate diameter to fit down an borehole or drill string pipe, and not become stuck in the open borehole or the drill pipe. Its design takes into account the use of modern fishing tools used to remove stuck tools. In embodiments where the tool is part of the drill string, then the tools should have a diameter sufficient to allow the tool to pass through borehole as it is being formed.
[0154] The tools of this invention include two hardware components, each with a unique set of features situated to work in a unique set of circumstances intended for use in oil and/or gas exploration applications: A) a neutron generating subsystem including at least one commercially available fast neutron generator or source commonly used in the oil and gas drilling operations, and B) a detection/imaging subsystem that detects and captures data concerning collisions between returning fast neutrons and atoms of the penning gas in the detectors of the detection/imaging subsystem, where the returning fast neutrons are generated by initial fast neutron collisions with formation solids, liquids, and/or gases. Each drilling environment has unique operational performance criteria and operating characteristics.
[0155] At system start up, the tools of this invention are initialized by a hand shaking routine between a control subsystem of this invention and tool based neutron source such as an americium source embedded in the neutron generating subsystem.
[0156] The analyzing subsystem of this invention includes software for implementing computer based methods designed to receive neutron-penning gas collision event data and interpreter the data to determine formation solid, liquid and/or gas properties and/or characteristics as the event data corresponds to energetics and directional data for elastic or inelastic collisions between formation atoms and initial fast neutrons emitted by neutron source used in the oil and gas industry. The initial fast neutrons may be generated by a 241Am/9Be neutron source. The source has a known starting energy level. The detector measures returning fast neutrons (neutrons scattered, reflected, refracted or otherwise having their direction directed back toward the tools of the systems of this invention through interactions with formation solids, liquids, and/or gases. The energetics of the returning fast neutrons (especially fast neutrons elastically scattered from formation atoms and/or molecules) are determined from the track and/or image data captured by the detection/imagining subsystem of this invention.
[0157] The returning fast neutrons, such as fast neutrons that have been elastically scattered off formation solids, liquids, and/or gases, entering into the detector(s) of the tools through a detector window(s) and interact with the atoms of the gas mixture(s) in the gas chamber(s), where the gas mixtures include a penning gas and a quenching gas. The initial energy level of fast neutrons created by the neutron source is about 4.5 MeV. The energies of the returning fast neutrons that have collided with the formation solids, liquids, and/or gases generally have energies range between about 4.5 MeV and about 100 keV; in certain embodiments, the returning fast neutrons have energies range between about 4.5 MeV and about 1 MeV; and in certain embodiments, the returning fast neutrons have energies range between about 4.5 MeV and about 2.25 MeV. The penning gas mixture is a mixture of a noble gas referred to as a penning gas such as 4He or a mixture of 3He and 4He and a quenching gas such as a freon or a mixture of freons, especially CF4 or mixtures of CF4 and other low molecular weight perfluorocarbons. The gas mixtures are held at a pressure of about 1 atmosphere in its normal state. The "normal state" is defined as a gas mixture at a temperature of about 20°C. The pressure of the gas mixture in the detector increases as the tools are exposed to higher temperatures, when the tools are subjected to downhole conditions.
Imaging Subsystem or Component
[0158] The energies of the returning fast neutrons are converted into photonic energy via the collisions between the returning fast neutrons and atoms of the penning gas in the gas mixture contained in the detector chamber(s) of the detectors of this invention. The penning gas, a noble gas such as 4He, has a large crosssectional surface area with fast neutrons. The collisions are quenched by the quenching gas generating electrons, which are accelerated down the drift region of the gas chamber causing an electron cascade that is then converted into scintillation light. The scintillation light is captured a images or tracks as a photonic image stream. The images or tracks are produced as energy from the collision is returned to the detector through a precise angle and distance between the neutron generating source and the spectrometer through its imaging window. The energy from the collisions is converted into photonic energy as it drifts a precise distance through the voltage drift region of the gas chamber. The precise direction of the collisions and the resulting energetices of the collision events are continually captured. These collisions are measured by the photonic energy output and are captured using a specially designed camera system with a specially designed CMOS Charge Coupled Device (CMOS/CCD) and the event data (color/hue/intensity data and directional data) are subsequently analyzed with the imaging software on the computer system.
Data Storage Component
[0159] Depending upon the tools or systems of this invention and on their configuration, the resulting event data are either recorded on the imager solid state computer storage component in string line mode or transmitted up the data cable to the operator at the surface. In stand-alone mode, the operation comprises a continuous stream of images randomly or sequentially stored on portable or fixed mass storage device, such as an internal hard drive, an external portable drive, a USB thumb drive, or any other fixed or portable mass storage device. All event data are periodically calibrated with a precise test sequence from a known location in the formation. In the networked version, the images are continuously distributed over the remotely controlled fiber optic data/power cable. This design eliminates the problem associated with the complexity from the degradation of epithermal and thermal neutron capture. The spectrometer only detects the energy level from the elastic collisions between the formation and the fast neutrons generated by the attached neutron source in proximity to the detector.
Measurement Component
[0160] The 241Am/9Be neutron source initially generates 4 × 107 neutrons per second. These neutrons are channeled toward the formation at a 90° angle and returned at a 39° angle to the detection window. Depending upon the lithography, some neutrons are immediately absorbed. Some neutrons are partially scattered. Other neutrons are deflected. The detector imaging window is constructed with fluorine doped tin oxide with a sensitivity of from 7Ù square to 3Ù square at 80% transmittance. Sensitivity is a function of the size of the aperture, the columnation, and the grating in the camera component. The neutron energy that returns to the detector is analyzed through the use of the imaging application software. The strength of the deflected neutrons is used to create a picture of the materials in the formation either in the open borehole or through the borehole pipe.
[0161] The detection means measures the nondestructive energy level of the neutrons measured from their deflection off the formation surface to the detector as compared with those generated from a fixed distance from the neutron source. The deflected neutrons are deflected back towards the detector and are captured by entering a window on the detector that is situated at a geometrically determined distance from the neutron generating source. The strength of the deflected energy caused from the collision between the fast neutrons and the formation is a function of the composition of the geological structure, the porosity of the formation and the amount of liquid and gas hydrocarbons. The expected range of the permeabilities and hydraulic conductivity of the energy source into various rock types determines the distance that the fast neutrons either collide or are absorbed or otherwise penetrated into the formation. Some of these expected permeabilities are summarized below in Table I:
Figure imgf000041_0001
[0162] A key feature of this software package of this invention is its ability to both simultaneously capture and subsequently graphically display the energies of collisions between the initial fast neutrons generated by the fast neutron source and formation components that return toward the sensor or tool subsystems and enter the detector. These collisions may be displayed in one of two embodiments. In the first embodiment, the collision data is captured on a computer system storage medium (a fast drive) for further review and analysis, when the instrument is pulled from the hole. The images are sequentially captured as the wire line lowers the sensor or tool subsystems in the well. As the cable releases the sensor or tool subsystems attached over the wireline down the bore hole the imaging takes place, while drilling or other measurements are taking place. This first embodiment of the invention relies on so-called "slickline data", because it is not sent to the surface until the test is run and the sensor or tool subsystem is retrieved from the bore hole. It requires a minimal specific battery powered system and the spectrometer is a self-contained unit mode.
[0163] In a second embodiment, when the sensor or tool subsystem is configured to be tethered on the drill string using a bi-directional fiber optic energy and data cable tethered over the drill string into the bore hole from a remote control platform with the imaging information can be provided in real time subject to the delay proportional to the length of the fiber optic cable and the depth of the instrument in the bore hole. The real time capture of the information is subject to the length of the cable between the operator console and the sensor or tool subsystem. Theoretically, if the sensor or tool subsystem is at the bottom of the bore hole at 10,000 feet, the delay of the signal from the platform operator is proportional to the distance and the signal travels 20,000 feet before the operator receives a response back from the sensor or tool subsystem.
[0164] The image analysis software component of this invention interfaces to the active area of the CMOS/CCD imaging camera component in the detector with the computer component of this invention and performs the following five activities:
1) pattern recognition to sort and identify the resulting collisions from the elastically scattered fast neutron;
2) measurement of the total light output creating tracks produced by the resulting interactions between the gas atoms and the returning fast neutrons;
3) continuous measurement of a length or a range of elastic collisions between the formation and the initial fast neutrons;
4) comparison of the resulting image data from the most recently detected event with a stored image from a look up table to identify the characteristics of previously stored collision data source. Solids, liquids and gas data collision images are stored with successive new images collected in the computer system by the software data system over time; and
5) compare raw test data without a source. [0165] The image is displayed in color as a series of pixels that reflect the energy captured by the CMOS/CCD component from the collision. The pixel size is optimized to achieve maximum resolution. They are a function of the size of the imager in the camera component and are in a range of from 8µ to 14µ. The pixel density drives the optical performance specification. In conjunction with the charge transfer efficiency, (CTE) a measurement of how well the Charge Coupled Device (CCD) electronics moves the pixel elements from its collection point in the detector to the output sensor so that data can be obtained from it. The larger the radius of the imager, the more CCD elements the imager and the larger proportional display area the imager has. The smallest detector has one CCD element; the largest detector has four elements whose image is further constructed.
[0166] The image analysis software is adapted to the unique diameter of the spectrometer imager component and is specific to the geometry of the well bore hole and whether the bore hole is open or cased.
Analytical Methodology and Theory of Neutron Fields
[0167] The software algorithms work on the principal of the identification of the energy level of the resulting scattering elastic collisions between the down hole materials and the fast neutrons from a specifically designed 241Am/9Be commercial chemical nuclear source. Let us consider source in a scattering medium which emit neutrons with an energy E or with an energy distribution (E). These neutrons exchange kinetic energy with the atoms of the scattering substance through elastic collisions. This exchange is captured before the neutrons ethermalize or subsequently thermalize. If the neutrons are emitted with energies higher than the kinetic energy of the thermal motion of the scattering atoms, they lose energy in successive collisions until they are in equilibrium with the thermal motion of their surroundings. The inventive step is to capture the energy of the neutron collisions before ethermal and subsequent thermal equilibrium is reached.
[0168] There is no scattering medium which does not absorb neutrons. In applied neutron physics, great attention is placed to substances that: (1) scatter neutrons strongly; meaning having a large scattering (Ós) cross section; (2) moderate neutrons strongly (having low atomic weight); and (3) absorb neutrons weakly. The neutron intensity in a scattering and absorbing medium depends on the strength of the source and is not stationary. The totality of neutrons in a scattering medium is characterized by their distribution in time, space and energy resulting in a neutron diffusion field or more simply the neutron field. The software algorithms measure the resulting collisions distributed by time space and energy.
[0169] Variable List (*Measuring the time, space, and energy of elastically colliding fast neutrons to determine the com osition of matter in a drill hole :
Figure imgf000043_0001
Figure imgf000044_0005
[0170] Let us consider a volume element dV = dxdydz of the scattering medium with the position vector r. Let n(r,Ù,E)dVdÙdE be the number of neutrons in this volume element whose flight direction, characterized by the unit vector Ù, lies in the differential solid angle dÙ around Ù and whose kinetic energy lies between E and E + n(r,Ù,E) (cm-3steradian-1ev-1) is thus the number per cm3; i.e., the density of the neutrons with energies unit interval at E and flight directions in a unit solid angle around Ù. Specifying the differential density, which is time dependent, is sufficient to describe the neutron field. The total number of neutrons with a given flight direction is obtained by integration over all energies as:
Figure imgf000044_0001
n(r,W) is called the vector density and replaces n(r,E) when we are dealing with a neutron field of constant energy. If we now integrate over all flight directions as well, we obtain the total number of neutrons in a volume element dV at the point r.
Figure imgf000044_0002
where n(r) is the density of the neutrons at point r. Next we introduce the concept of the differential neutron flux which is defined by:
Figure imgf000044_0003
where í =(2E/m)½ is the neutron velocity. It is the number of neutrons at the point r with energies between E and E + dE and flight directions in the differential solid angle dÙ which penetrate a surface area 1 cm2 perpendicular to the direction Ù in one second. By integration of the differential flux F(r,Ù,E)(cm-2sec-1steradian-1ev-1) over energy we obtain the flux vector F(r,Ù), which is the number of neutrons that penetrates a 1 cm2 surface perpendicular to the direction Ù through the differential solid angle dÙ per second. Finally,
Figure imgf000044_0004
is called the flux of neutrons. In practice, the flux Ö (cm-2sec-1) is the datum most frequently used for describing neutron fields, and for this reason it is important to make its physical significance clear.
[0171] Let us consider a circular disc with a surface area described as: ðR2 = 1 cm2 whose center is rigidly fixed to a point r. F(r,Ù)dÙ is the number of neutrons, which penetrate through the solid angle element dÙ around the direction of the normal Ù per second. In this picture, the integration by which the flux is formed can be represented by rotation of the disc in all directions keeping the center fixed. In such a rotation, the disc describes a sphere of cross section ðR2=1cm² and of surface 4ðR2 = 4 cm². Thus the flux Ö is the number of neutrons which penetrate this sphere per second from all sides. It follows from this fact that in an isotropic neutron field, a field in which all flight directions are equally represented, Ö/2 neutrons penetrate a 1 cm²surface per second. For, in the isotropic field equally many neutrons pass through each surface element of the sphere introduced above. Since altogether 2Ö neutrons pass through 4 cm2 per second (each neutron passes once form the outside to the inside and once from the inside to the outside), Ö/2 neutrons go through 1 cm2/s.
[0172] In most cases, F can be represented as a function of only one angle h that is measured from a distributed axis with respect to which the field is considered to be rotationally symmetric. In such a case, we can always expect the quantity F(r,Ù) in Legendre polynomials as a rule with considerable advantage insofar as the mathematical treatment of the problem is concerned as:
Figure imgf000045_0001
The first four Legendre polynomials are:
Figure imgf000045_0004
The equation:
Figure imgf000045_0002
The formula holds for the quantities Fl(r). In particular:
Figure imgf000045_0005
[0173] The second expansion coefficient also has physical significance. In order to see this, let us introduce an important new quantity, the current density J in the direction of the distribution axis. The magnitude of this vector is the net number of neutrons which penetrate a 1 cm² surface perpendicular to the distribution axis per second. Thus:
Figure imgf000045_0006
[0174] By comparison with Eq. 6, it follows that J(r) = F1(r). Thus the first two terms of the expression Eq.5 can be wr
Figure imgf000045_0003
And it will turn out that in many cases the vector flux F(r, ) may be approximated by these two terms with adequate accuracy. [0175] The space and time behavior of a neutron field may be described by setting up a "neutron balance". The number of neutrons n(r,Ù,E)dVdÙdE in a volume element dV with flight directions in the solid angle dÙ and energies in the interval dE may change for the following reasons:
[0176] Leakage out of dV:
Figure imgf000046_0005
[0177] Loss due to absorption and scattering into other directions. Even for the highest achievable neutron densities, neutron-neutron collisions do not occur; thus we only need to consider neutron collisions.
Figure imgf000046_0001
[0178] Gain due to in scattering of neutrons from other directions and energy intervals.
Figure imgf000046_0002
[0179] Produc on o neu rons y sources n source ens y r, , : r, , dVdÙdE.
[0180] The sum of all of these contributions ives the time rate of chan e of the differential densit .
Figure imgf000046_0003
This integro-differential equation in seven variables (three position, two direction, one energy, and one time coordinate) is called the transport equation or the Boltzmann equation. Together with appropriate boundary conditions, it determines the vector flux arising from the given source distribution. The most important boundary condition occurs at:
a) the interface G between two scattering media A and B. By reason of continuity, the following equation must clearly hold for all rG, Ù and E:
Figure imgf000046_0007
b) the interface between a scattering medium and a vacuum or a totally absorbing medium. Since no neutrons can return to the medium through the interface:
Figure imgf000046_0006
must obviously hold for all inwardly directed Ù.
[0181] Eq. (10) can be simplified in some important special cases including the time and energy independent cases. For this case, the transport equation takes the form:
Figure imgf000046_0004
and describes the diffusion of mono-energetic neutrons in a medium which contains stationary sources and in which a collision causes no change in energy. Eq. 13 will be treated later. Also important is the time- and space -independent cases. Here the term Ù• LF in equation (10) drops out and it becomes possible to integrate over all angles. One then obtains:
Figure imgf000047_0005
[0182] Here 3s(Ù'6Ù, E'6E)dÙdE is the neutron flux per unit energy at E. Eq.14 describes the moderation of neutrons in an infinite medium with homogeneously distributed sources. The transport equation for the case of stationary but space and energy dependent neutron fields, the neutron diffusion with energy exchange with the atoms of the scattering medium is:
Figure imgf000047_0001
For a description of time and energy dependent fields, the terms (1/í)(MF/Mt) and (1/í)(M )(Mt) must appear on the left side of Eq.13 and 14, respectively.
[0183] The transport equation is limited to time and energy independence. Let us consider a circular disc with a surface area of 1cm2 and calculate the number of neutrons crossing the surface per second with directions in the element of solid angle dÙ around the normal to the disc. The contribution of the volume element R is obviously equal to:
Figure imgf000047_0006
times the probability that the neutrons reach the surface of the disc. The latter is equal to the solid angle multiplied by the probability that no collision occurs along the path R. If we divide by the element of the solid an le dÙ it then follows that:
Figure imgf000047_0002
The integration extends to infinity if the scattering medium is infinite; in a finite medium, integrate to the value of Rmax at which the straight line r-RÙ reaches the surface. Eq.16 can be derived directly from Eq.13.
[0184] Assume that the spatially distributed sources radiate isotropically (uniform in all directions) such that:
Figure imgf000047_0003
[0185] Now if we integrate over Ù' on the right hand side and obtain:
Figure imgf000047_0004
[0186] If we replace r-R on the right hand side by a new position coordinate r' and replace dRdÙ = R2dRdÙ/R2 by dV/(r-r')2 , we can integrate Ù and obtain:
Figure imgf000047_0007
In contrast to the transport Eq. 13 no longer contains the direction coordinate Ù when all of the neutron and all of the incident angles are required to be part of the calculation.
[0187] It is important to note that an inventive aspect of the present invention is the importance in knowing the initial starting energy of the fast neutrons and to channel only those neutrons that are focused on the formation and calculate only those that are elastically scattering anisotropically. Conversely, if the neutrons scatter both elastically and inelastically, a complex calculation including the time, space, and independent cases require integration over all of the angles. Such a calculation is possible but difficult to calculate quickly impacting the speed of the measurement.
Spherical Harmonics– Fick's Law
[0188] It is important to derive from Eq.13 a simple diffusion equation of the Fick's Law type, one that represents a linear relation between the current density introduced in (Eq.8) and the gradient of the neutron flux. Assume that the neutron field is rotationally symmetric around a distribution axis; furthermore, we assume plane symmetry and let the distribution axis be the x-axis. Eq. 13 then becomes:
Figure imgf000048_0001
[0189] The Legendre polynomial Pl(cosh) expresses the measurement of the angle of the anisotropically scattered fast neutron. The speed for capturing the collision is also critical to its accurate measurement. The deflected energy of the collision is directly captured by the gas in the detector. If we expand the vector flux F in Legendre polynomials and break the expansion off after the second term, we set:
Figure imgf000048_0002
[0190] This is known as the elementary diffusion equation. These are important relations.
Figure imgf000048_0003
Eq.22 is the continuity condition which states that in one cm³ of a stationary neutron field the losses through leakage and absorption are equal to the number of neutrons provided by the source (S). This relation is independent of the special approximation (Eq. 9); this is physically obvious and can be easily proven formally if one notes that if additional terms of the expression for F are kept they drop out in the integration over Ù. From Eq.23 one obtains, via Fick's Law of diffusion;
Figure imgf000048_0004
the current density is proportional to the flux gradient. The constant of proportionality D(cm) is called the diffusion coefficient; if the trans ort cross-section:
Figure imgf000049_0001
[0191] Is introduced, and can be expre
Figure imgf000049_0002
The diffusion length is measured by:
[0192] We obtain:
Figure imgf000049_0003
or in the general three dimensional
Figure imgf000049_0004
We now have a simple differential equation which permits the calculation of the flux arising from a specified source distribution.
Maxwell Distribution of Energies
[0193] According to the Maxwell Distribution Law, the number of neutrons dn per cm3 with energies between E and E + dE is:
or
Figure imgf000049_0005
where is the total density. It follows that the average energy is:
Figure imgf000049_0008
Figure imgf000049_0006
Using = 2 =
Figure imgf000049_0007
The most probable velocity is
Figure imgf000050_0001
[0194] Furthermore,
Figure imgf000050_0006
[0195] Rewritten as: kT = ET, so that
Figure imgf000050_0007
when T = 293.6°K (20.4°C), ET = kT= 0.0253 eV and vT =2200 m/s = v0.
[0196] The average velocity is
[0197] Therefore
Figure imgf000050_0002
[0198] The distribution of the neutron flux is iven b :
Figure imgf000050_0003
or
[0199] Here
Figure imgf000050_0004
is the total flux. It is easy to see that compared to the density, the flux is always shifted to higher energies. When the Maxwell distribution of neutron flux and density is compared to the density, the flux is always shifted to higher energies.
[0200] It is worthwhile to derive some general formulas for averaging expressions of the type (E/ET)l over the densit an flux distributions. Avera in over the densities ives:
Figure imgf000050_0005
While averaging over the flux gives:
Figure imgf000051_0001
Here is the gamma flux function. Some special values of the gamma function
Figure imgf000051_0002
are
Figure imgf000051_0003
Operational Details
[0201] The detection system of this invention includes at least one detector and at least one imager. The detector converts returning neutrons into light energy through neutron-gas collision producing electrons, which drift through a voltage drift zone producing light. The imager is a spectroscope that captures images the light produced by these neutron-gas collisions in the detector. The light generated in the detector corresponds to the energetics of returning fast neutrons after interacting with downhole materials including formation solids, liquids, and/or gases during exploration and production. The imager measures light of varying wavelengths or frequencies corresponding to the energetics of the returning fast neutrons.
[0202] From the energy of the fast neutrons, digital images called photonic tracks are captured and converted into image data. The image data is used for comparative analysis against known image data. The comparison between detected image data and known image data enables the characterization of geological structures and states of matter downhole without destroying them.
[0203] Collisions between fast neutrons and particles comprising varying states of matter are used to create energy measurements from which a picture of the formation characteristics in the vicinity of the bore hole during oil and gas drilling is derived. Each particle has its own characteristic form or wavelength from which energy measurements are subsequently calculated and compared with data cumulatively generated in a data base. The features of the detected images are correlated by a set of algorithms based on color, hue, and saturation based on a color tree system, which has 10 basic hues, each of the hues having 10 gradations, developed by Albert H. Munsell. This system is the official system for evaluating soils in the United States. Chroma scales represent different wavelengths depending upon the hue and gradation.
[0204] The tristimulus values of a spectrum components X, Y, and Z are found by multiplying the xG, Gy and zG curve times of the spectrum in question, a detected image event. They are compared using a chromaticity diagram constructed according to the following formula defining the color coordinates x, y, and z as follows:
Figure imgf000051_0004
The formula provides that if two coordinates are given, the third is automatically determined. The International Commission on Illumination (CIE) chromaticity or tristimulus diagram shows colors determined by CIE graphs and equations working on formulas not on color samples. The color samples are used to derive the subsequent formulas. An additive mixture of two colors is represented by a point on a line connecting the points corresponding to the two colors.
[0205] The interpretation of these calculations provides useful descriptions of the characteristic information about the conditions downhole. This information is available for simultaneous evaluation by multiple users during oil drilling exploration and hydrocarbon exploration processes. Images called ''tracks" are made from collisions of the returning fast neutrons with a Penning gas in the detector. These "tracks" are interpreted using software algorithms written to directly characterize and interpret the energetics of the returning fast neutrons resulting from the interactions of the initial fast neutrons with formation components downhole. The collisions between the initial fast neutrons and formation components can occur continuously, intermittently, and/or periodically allowing continuous, intermittent, and/or periodic detection, analysis, interpretation, and transmission of image data to an operator during logging and drilling operations.
[0206] The system includes a digital software platform operating on a high speed digital image capture and calculating engine, where image data is captured, shared, and interpreted by various users simultaneously in "real time"– delayed only by the time lapse between fast neutron return, detection and imaging. The image data interpretation may be simultaneously retransmitted so that analysis of the data may occur locally or over a remote communications link in real-time as the data is being generated. Drillers, service company personnel and geophysicists may all collaborate and have access to the same data at the same time anywhere in the world. This is meant to make the exploration process more efficient and effective especially in complex geophysical environments.
[0207] Fast neutrons of a known energy distribution are generated in a neutron source, initial fast neutrons. These fast neutron sources have long (more than 400 year) half-lives so the number of neutrons generated over a proscribed period of time is very stable. The initial neutrons are focused mechanically by the construction of the tool toward the formation downhole using the detection apparatus. A radiation hardened image sensor component is positioned inside the detector a fixed distance from the neutron source on a wire line. The imager contains a shutter that opens and closes capturing the neutrons that are reflected back to a detector after their collision with the formation elements. These elements may take the form of solids, liquids or gasses. Depending on their type, the energy returned from the collision may be characterized and stored for further comparison in a data base.
[0208] When the returning fast neutrons slowed by their collision with particles down hole are captured by the detector, their energy is measured by a collision with a known quantity of a penning gas in the detector. This collision converts the energy of the fast neutron into a photon captured by the imager photographic elements. The chain of photons created by this collision with the gas is called an image track. The colors generated by the collision between the gas and returning fast neutrons create image tracks which are analyzed using sophisticated imaging algorithms stored in a second data base. Over time, the image data base expands to represent and encompass many types of collisions between the fast neutrons and various energetic particles represented by the image tracks. These track images are interpreted providing complex formation information representing the conditions downhole. These track images are used to characterize the formation characteristics at varying distances from the vicinity of the bore hole. These images are used to guide the interpretation of the formation to optimize the speed direction and operation of the drilling apparatus.
[0209] The data is converted into a histogram used to illustrate the energy from the collision between the Penning gas with various types of rock structures, compositions and states of matter downhole. These histograms are represented by Gaussian distributions because their theoretical properties can be used to approximate a large number of practical energy distributions (discussion taken from Trussell and Vrbel Fundamentals of Digital Imaging). A stochastic model of imaging is used to characterize a class of random images. The basis for it is a set of instructions that define how the class of images is generated. These instructions are reduced to a set of proprietary imaging algorithms written for this purpose.
[0210] The most common continuous probability densities are either uniform or Gaussian: Uniform over the range:
a #x# b, p(x) = 1/b-a for a#x#b and zero otherwise.
[0211] Gaussian or normal probability densities are:
Figure imgf000053_0001
where, ì is the mean and a is the standard deviation of the distribution;
[0212] Depending upon the structure encountered, the results may also be exponential:
Figure imgf000053_0002
or Laplacian:
Figure imgf000053_0003
[0213] All data is subject to the orthogonally principle, that is, the prediction error of the data is orthogonal to the data on which the prediction is based. Estimating the rock type coefficients for an autoregressive model, the single model can be written as a typical least squares minimization problem. [0214] Determining the prediction coordinates can be written as:
Figure imgf000054_0001
The region of support, Sx will be assumed to be limited to a finite number of terms. The solution is obtained by differentiating å2(m,n) with respect to a(k,l)and setting the result to zero or by using the orthogonally principle directly. Since (k,l) is used for the index of summation, we will denote the differentiation with res ect to a as:
Figure imgf000054_0002
which is a realization of the orthogonality principle, that is, the prediction error is orthogonal to the data on which the prediction is based. The result looks like the above equation except for the âä(p,q) term and the range of (p,q).
[0215] Gathering terms of (k,l) we have:
Figure imgf000054_0006
[0216] Using the definition of autocorrelation for a stationary process,
Figure imgf000054_0003
[0217] We obtain the equation:
Figure imgf000054_0007
Setting the result to zero, we have:
Figure imgf000054_0008
Using the definition of autocorrelation for a stationary process: for (p-q)0Sx
Figure imgf000054_0009
which is a realization of the orthogonality principal, that is, the prediction error is orthogonal to the data on which the prediction is based.
[0218] The auto-regeneration image model can be written as in equation:
Figure imgf000054_0004
where ù(m,n) is the white noise input with variance â2. We can also represent the output as the convolution of the impulse res onse h m n and the in ut noise
Figure imgf000054_0005
where Qx is the infinite set of casual indices for the equivalent system; writing this in Z-transform domain, we have:
Figure imgf000054_0010
[0219] From equation 1 we have:
Figure imgf000055_0003
which is the 2D equivalent of equation
Figure imgf000055_0004
Using the relations between autocorrelations and power spectra of the shift invariant systems of previous section, we can obtain the Z-transform representation of the spectrum of the output:
Figure imgf000055_0005
[0220] The basic equation for finite rediction re ion Sx is:
Figure imgf000055_0001
[0221] It is noted that the set of indices needed for the correlation function is usually larger than that of the Auto Regeneration coefficient. The symmetry of the autocorrelation can be used to reduce the number of distinct values. The correlations generated by the model may not match the correlations used to generate the model. The Auto Regeneration model has the same advantage in 2D as it does in 1D in that it is possible to obtain improved separation of frequency components over the Fourier transform based methods.
Image Processing
[0222] The Auto Regeneration AR ima e eneration model can be written as:
Figure imgf000055_0002
where (k,l) are the prediction coefficients. S1 is a subset of the indices in a two dimensional lattice that defines the prediction region and (m,n) is the prediction error. (m,n) is the white noise input with variance â2. The imaging processing used in this application is based on Bayer color filtering methodologies. For additional information, the reader is directed to US3971065, US20070145273, US20070024879, and US20050231618. The methodology is brief recounted below.
A. Demosaicking
[0223] The color filter array treats each channel separately and computes the interpolations as a reconstruction. Using spline interpolation on all three channels of a Bayer array results in good color reproduction of smoothly varying areas, but extreme color artifacts in regions of high spatial activity like a picket fence as the distance from the camera increases. The three color channels are significantly correlated. The green channel of a color filter array (CFA), which approximates the CIE luminance efficiency function, provides the main information that is used to determine the presence and orientation of edges. The presence of an edge is indicated by the significant differences in the local values. To obtain good resolution, the neighborhood that is used to detect an edge must be relatively small. To obtain a good estimate of the presence of an edge and its direction, the neighborhood should be larger; however, there are conflicting requirements. In practice most demosaicking methods use a minimal 3 × 3 pixel neighborhood to estimate edge properties. Having estimated the presence and direction of a local edge, the information used to interpolate the green values in adjacent pixels, where only a red or blue measurement exists. This will give a full resolution image in the green or luminance channel. The data may be used to determine how to interpolate the other channels. The interpolation may operate directly on the red (R) and blue (B) channels or one of the color difference channels, because the R - G and B - G vales are available after the interpolation of the green channel. Correlation between the color channels is used in a multi-step- process. Most demosaicking algorithms use an interpolation scheme that does not alter the original data.
[0224] The interpolation scheme uses the frequency domain allows the software algorithm to exploit freely the high and low pass nature of various features in the image. Hyperspectral imaging outside the visible range may be used, where the primary application is detection and classification of objects and terrain features.
B. Histograms
[0225] The histogram of a signal is an array that records the frequency of occurrence of the values of the signal. For the purposes of our analysis, the values in the hydrogen index are reduced to a set of histograms. If the signal is scalar valued the histogram can be defined as a vector and plotted as a graph or bar chart. By analyzing the histogram, certain types of downhole materials (i.e. hydrocarbons, rock types etc.) are grouped for analysis. For that signal, s(n), for 1#n#N each such element of the occurrence histogram h0(k) is the number of times the value s(n) lies in the interval dk#s(n)<dk+1, for k=0,..., M. The probability histogram is obtained by dividing the occurrence histogram by the total number of samples h(k) = h0(k)/N. This gives an approximation distribution of the signal values that is, the signal s(n) is a sample of a random variable X, then
Figure imgf000056_0001
is the probability that X lies in the interval [dk, dk+1], the bin widths of the samples of N should be large enough to show sufficient detail and be consistent with the quantization of the signal values. For most images the values are between 1 and 255. Using simple algorithms such as setting the bin width to the range of the signal divided by a fixed number of bins can yield an error. The appearance of nearly periodic zeros in a histogram is an indication that the original signal is quantized and the bin width chosen is not well matched with that quantization.
[0226] A stochastic process is an indexed set of random variables. The index set can be continuous or discrete. An example of a discrete stochastic process is the sequential values of different types of materials found in a bore hole. In an image example, each pair (m,n) identifies a random variable. The stochastic process can be indexed by a continuous variable as in the case of the relationship of fast neutron radiation as a function of spatial location. The usual definitions of mean and variance may be used for stochastic processes. However, it is important to realize that those statistics are defined for each index, that is the mean index n1 is not necessarily the same as the mean at index n2. The mean of an stochastic process, E[X(n)] is a deterministic function of n. Likewise the variance is a deterministic function of n.
C. Parallel Pattern Recognition System
[0227] The architecture of the computer and imaging system is a massively parallel array meeting our pattern recognition requirements. FPGA's and custom logic can be used to take advantage of parallel processing. Using state transition elements (STE's) embedded for each item in an image expression, an expression is matched to a set of STE's and at least one terminal event that allows the host computer to recognize an imaging event and the chain that triggered it. An Automata Processor (AP) hosts multiple expressions which are evaluated in parallel. Each STE has 256 bits of information associated with it. An STE matches a single pixel stream that will have one bit out of 256 to process many bit streams such as in a continuously imaging chip. An eight bit symbol accesses a 256 but array per STE. The output is ANDED with the output of a 512 bit array indexed by a 9 bit address of the logical data stream. This translates into 768 bits per STE's within a block can enable any STE within the block. STEs may also connect to adjacent blocks and an STE output can enable one or more other STEs.
[0228] Automata Network Markup Language (ANML) is the XML based programming language for an AP. It provides linkages between STEs. ANML implements rule based system for controlling an imaging data stream generated by the CMOS/CCD imaging chip.
D. The Image Display Function
[0229] The user interface generates an image on the operator screen used to monitor the system. The imaging component contains a CIE chromaticity diagram with the color coordinates represented in three axis by (x, y, and z.). The strength of the collision between the returning neutrons that elastically collided with the formation elements is converted into a track or wavelength in nanometers that is scaled to the strength of the collision measured by algorithms written in the proprietary application software. The returning fast neutrons strike the gas molecules triggering photons whose energy is captured by the camera. the and determined by their strength converted photonic energy in color that is mapped according to its chromaticity diagram. Neutrons that elastically collide with rock will return the greatest strength neutrons and neutrons that are partially adsorbed by the liquid or gas hydrocarbons or the liquids from the drilling fluids partially absorb the neutrons and will return less powerful strength collisions. Water, principally containing hydrogen, has unique properties in this imaging system since neutrons consisting of hydrogen and oxygen and the neutrons will be greatly absorbed and return the weakest neutrons collision energy since hydrogen atoms have about the same size and mass as the returning neutron. The following Figure 16 demonstrates the relationship of the wavelength in nanometers to their relative value as neutron sources. The Oswald System uses the dominant wavelength, purity and luminance to measure the strength of the elastically collided neutron.
[0230] Using a CIE Chromatography Diagram, the entire spectrum of fully saturated hues from 400 nm to 700 nm lies on the smooth outer curve shown in Figure 15. The x-axis and y-axis of the chromatography diagram shows the plot of the relationship of the relative strengths of the elastically bounded neutrons and their collision with the proprietary gas mixture. The vertical axis (y-axis) represents lightness and the distance from the x - axis represents the hue.
[0231] A schematic diagram of the resulting conversion of the strength of the returning collision between the fast neutron and the gas that creates the picture of the strength of the collision is shown on the Oswald dominant wavelength, purity, luminance color tree, a relationship between the saturation, (variable shown on the x-axis), the color lightness (variable on the y-axis) and the color hue (variable on the z-axis) is shown in Figure 12. The strength of any resulting collision equates to a value expressed as a single integer representing the (x, y and z) values shown in color on the display.
[0232] This calculated value is compared in a look up table with the states of matter, and the types of rocks found downhole in the geological formation. The collision of the fast neutrons with the states of matter and rock types and their densities is correlated to the colors in the chart. [BIN 255-1] E. Filtering
[0233] Thermal imaging wavelengths in the region 400 nm to 700 nm (the visible region) are controlled by multi-layer thin film filters (TIFFS). They enable wavelength division multiplexing amplification gain flattening and dispersion compensation in high capacity fiber optic networks (1300 nm to 1600 nm). Temperatures are generally room temperature ranging from 20°C to 50°C.
[0234] Plank's radiation law is given by:
Figure imgf000058_0001
where ë is the wavelength, T is the temperature, h is Plank's constant, c is the speed of light kB is Boltzmann's constant. The intensity of the detector has inverse proportionality to the concentration of the gas according to Lambert-Beer's law I = I0ekP , where I is the intensity of light at the detector; I0 is the reference intensity (no gas present); k is the absorption coefficient constant for the system and Pis the concentration of the gas being measured.
[0235] The detectors of this invention are directional detectors and are capable of measuring neutrons entering the detector from a 4ð solid angle of entry. Ionization energy is released as the fast neutron collide with the penning gas, generally4He, producing scattered alpha particles, helium nuclei. These nuclei are quenched by the quenching gas. The generated electrons lose energy as they drift in a static electric field to an amplification region. Here the electrons enter a high voltage region that generates an avalanche or cascade of secondary electrons thereby enhancing the signal. The electron cascades generate scintillation light, and these scintillation photons are read out with a silicon photomultiplier tube that makes a track of the alpha particle.1) neutrons are focused by designing the neutron source so that the initial fast neutrons are directed through a narrow opening in the source.2) Source emits fast neutrons at 105 n/s.3) What is the curie equation Nsource = (6.56* óbackground for a 99% confidence level? Time= (6.562) * (Ratebackground) = (Rate 2
source ) is the time to detect 105 n/s a directional system detects faster because of a reduction in the background.
IMAGING METHODS OF THE INVENTION
[0236] The imaging methods of this invention are designed to operate this imaging units that collect data in rows of imaging elements, generally pixels, of the imaging unit such as the pixels associated with a CMOS/CCD imaging unit. Thus, if the imaging unit includes p pixels, these p pixels are generally arranged in a matrix format including n row and m columns. As an image is collected, the unit scans the p pixels row by row or column by column. Thus, the most efficient format for capturing neutron event data is to analyze pixel data on a row by row or column by column basis. Data associated with each pixel as is it received by the image processing components of the imaging system are analyzed for threshold signature values. The threshold signatures may be pinned to photomultiplier data, where the photomultiplier data signifies amplitude of any generated scintillation light. As the pixel data is collected, pixels passing the threshold signature tests are collected a group to form an event track or image. The tracks or images include information on the energetics of each event and on the direction from which the fast neutron entered the detector for each event. The event data includes color and/or hue data and intensity data. The data are then compared to data stored in a database. The data in the database include color and/or hue data and intensity data that has been corrected with various solids, liquids, and/or gases commonly found in a downhole setting. Thus, the database includes pixels data collected from fast neutrons of different energies colliding with gas mixtures having different mixtures of penning gases and quenching gases and different relative concentrations of penning gases and quenching gases. The database also includes pixel data collected from fast neutrons irradiating different materials– solids, liquids, and gases and mixtures thereof. The analyzing subsystem also includes software for updating and/or refining database of pixel data based on data collected while using the tools of this invention so that the database learns during use of the tools especially during logging wells that have known solid, liquid, and gas profiles. Thus, the more the tools are used, the more refined the pixel data stored in the database for interpreting an unknown pixel data or event data during downhole data collection during drilling and/or logging.
DETAILED DESCRIPTION OF METHOD DRAWINGS
General Method Embodiments [0237] Referring now to Figure 8, an embodiment of a method of this invention, generally 800, is shown to include returning fast neutrons enter the gas chamber of the detectors of this invention in an enter step 802. After entering the gas chamber, the returning fast neutrons collide with atoms of the penning gas in the gas chamber in a collide step 804 to generate energized penning atoms/ions. The energized atoms/ions are quenched by the quenching gas in a quench step 806 to generate electrons. The generated electrons drift down a voltage drift region of the chamber in a drift step 808 generating scintillation light. The scintillation light is captured in a light capture step 810 by one or more photomultiplier tubes, which also triggers the imager if the light intensity of detected by the photomultiplier tube meets a threshold intensity. Capture pixel data associated with a triggered collision event in a pixel capture 812 on a pixel by pixel basis generally as a row or a column in the imager is collected. Analyze each captured pixel in a threshold test step 814 to determine whether a captured pixel include color/hue/intensity data above color/hue/intensity threshold values. If the pixel data is below the threshold values, control is directed along a No path to the pixel capture step 812. If the pixel data is equal to or exceeds the threshold value, controlled is transferred along a Yes path to a pixel collect step 816, where activated pixels are collected to form a collision track or image. The track data is analyzed in an analyze step 818 to produce event data comprising track pixel color/hue/intensity data and track directional data. The track pixel color/hue/intensity data is compared to known pixel color/hue/intensity data in a compare step 820 and the event data is stored. The comparison is used to determine and identify downhole materials (solids, liquids, and/or gases) and map identified materials based on track direction data in a determine, identify and map step 822. The identification and map data is then transmitted to an operator in a transmit step 824. The methods may also include software to refined known data base pixel data or to produce new pixel data for better identification of downhole solids, liquids and/or gases. The operator may then use the identification and map data to adjust drilling trajectories, to stop drilling or to change drilling trajectories.
Specific Embodiments
[0238] Referring now to Figures 9A-D, other embodiments of methods of this invention, generally 900, are shown. Looking at Figure 9A, the methods include a system power on step 902. Next control is sent to a test computer subsystem (CS) step 904. If the computer subsystem does not initialize, then control is sent back to the power on step 904 along a No path. If the computer subsystem initializes, then control is sent along a Yes path to an instrument calibration step 906. After the calibration step 906, control is transferred to an initialize read out step 908, where elevation location data is read. Control is then transferred to a neutron generator subsystem (NGS) test step 910, if the NGS test fails, control is sent along a No path back to the CS step 904. If the NGS test is successful, then control is transferred along a Yes path to a read neutron generator step 912, where the direction and orientation of the generator is read. Control is then transferred to a first detector D1 test step 914. If the D1 test fails, then control is transferred along a No path to the CS step 904. If the D1 test is successful, then control is transferred along a Yes path to a D1 ready for image capture step 916. Control is then transferred to a second detector D2 test step 918. If the D2 test fails, then control is transferred along a No path to the CS step 904. If the D2 test is successful, then control is transferred along a Yes path to a D2 ready for image capture step 920. Control is then transferred to a D1, D2, and CS ON step 922 to determine whether the two detectors and the computer system are ON and ready for data collection.
First Specific Embodiment
[0239] Looking at Figure 9B, in a first embodiment of a method of this invention, control is transferred to a computer subsystem communication ON (CS Com ON) test step 924. If the CS Com ON test fails, then control is processes along a No path to the CS step 904. If the CS Com ON test is successful, then control is transferred to an initiate storage for image image capture step 926. Once initiated in the initiate step 926, control is transferred to an initialize index depth locator step 928 so that downhole location data may be read. After initialization of the depth locator, control is transferred to a synchronize detector 1, D1, detector 2, D2, storage, and depth locator in a synchronize step 930. Control is then transferred to a read imaging results step 932. Control is then transferred to an output synchronized test step 934. If the output synchronized test step fails, then control is transferred along a No path to the initiate storage step 926. If the output synchronized test step is successful, then control is transferred along a Yes path to a capture image from D1 step 936. Control is then transferred to a capture image from D2 step 938. Control is then transferred to an increment locator step 940 and then to a mark locator step 942. Control is then transferred to a capture image and conduct analysis step 944 and then to an end of log test step 946. If the end of log test fails, then control is transferred is transferred along a No path to the capture image for D1 step 936. If the end of log test is successful, then control is transferred along a Yes path to a termination data capture step 947. Control is then transferred to a prepare log step 948 and finally to a output written log step 949.
Second Specific Embodiment
[0240] Looking at Figures 9C&D, a second embodiment of a method of this invention is shown, In this method, control is transferred to a computer system power up and initialization step 954, where the computer subsystem (CS) is powered up and software is initialized. Control is then sent to detector subsystem power up and initialization step 956. Control is then sent to a detector 1 (D1) pulse charge amplifier test 958. If the test 958 fails, then control is sent along a No path to the step 956. If the test 958 is successful, then control is transferred along a Yes path to a detector 1 (D1) pulse charge circuit test 960. If the test 960 fails, then control is sent along a No path to the step 956. If the test 960 is successful, then control is transferred along a Yes path to a detector 2 (D2) pulse charge amplifier test 962. If the test 962 fails, then control is sent along a No path to the step 956. If the test 962 is successful, then control is transferred along a Yes path to a detector 2 (D2) pulse charge circuit test 964. If the test 964 fails, then control is sent along a No path to the step 956. If the test 964 is successful, then control is transferred along a Yes path to a commence imaging sequence step 966, where the imaging unit is initialized sequence procedure. After imaging unit initialization, control is transferred to an initialize location proximity sensor step 968, which generators location data as the imaging system collected event data for neutron-gas collisions occurring in the detectors D1 and D2. Again the event data comprises color/hue/intensity data and track directional data. Once the imaging unit and the location proximity sensor have been initialized, then the method proceeds along to parallel paths concerning the two detectors. The method include simultaneous or parallel steps 970a&b, where event data are collected or captured in detector D1 and detector D2 simultaneously as the two detectors are at different distances from the fast neutron generator of the tools of this invention. After the event data collection or capture, the methodd include transmitting the D1 and D2 event data to the computer subsystem CS in simultaneous transmit event data steps 972a&b. After the transmit steps 972a&b, control is transferred to parallel or simultaneous interpret event data steps 974a&b. After the interpreting steps 974a&b, control is transferred to parallel or simultaneous indexing or registering steps 976a&b, where the D1 event data is indexed or registered with D1 location data and the D2 event data is indexed or registered with D2 location data. After the indexing steps 976a&b, control is transferred to parallel or simultaneous logging producing steps 978a&b, where indexed D1 and D2 data is accumulated and organized into D1 and D2 logging data. After the producing steps 978a&b, control is transferred to parallel or simultaneous display D1 and D2 log steps 980a&b, where the produced logging data is displayed for a user or operator to observe so that the logging data is available for determining well drilling direction, when it re-commences or while drilling is proceeding. After the displaying steps 980a&b, control is transferred to parallel or simultaneous store logging result step 982a&b, where the D1 and D2 logging results are stored for further analysis or for archival purposes. After the storing steps 982a&b, control is transferred to a stop step 984. The entire process may be started and stopped numerous times during a logging or drilling operation or the process may be continued during the entire drilling operation.
IMAGE COLLECTION METHODS OF THE INVENTION
[0241] Referring now to Figures 10A-B, embodiments of image processing methods of this invention, generally 1000, are shown. Looking at Figure 10A, the methods start with an initialize imager step 1002, which initializes the imaging units of the detectors of this invention. Next, the methods then include a capture pixel data on a row by row or column by column basis in a capture pixel data step 1004. [0242] The imaging unit such as CCDs, iCCDs, CMOS/CCDs, etc.) used in this invention comprise a matrix or array of pixels indexed by rows and columns. The software associated the imaging units generally collect data on the pixels on a row by row or column by column basis depending on array orientation and the particular imaging unit. However, as computer technology improves, the manner in which the pixels are read also changes. So although the present methodology is assuming a row by row or column by column pixel data capture format, the same technique is amenable to any pixel data capture format such as two rows at a time, four rows at a time, etc., where each read may be controlled by different processing units so that more of the pixels may be polled on a near simultaneous basis. Thus, the entire methodology may be easily implemented on a parallel basis, where different processors analysis pixel data on a parallel basis.
[0243] Next, the methods include an analyze data captured for each pixel is a capture pixel data step 1006, where data associated with each pixel is analyzed for color, hue, and intensity data. Once analyzed, the color/hue/intensity data of each pixel is compared to threshold values in the threshold test step 1008. If a pixel fails the threshold test, then control is transferred along a No path to the analyze step 1006, where another pixel is analyzed. If the pixel passes the threshold test, then control is transferred along a Yes path to a correlated test step 1010. If the pixel data are not correlated with a photomultiplier threshold event, then control is transferred along a No path back to the capture pixel step 1004. If the pixel data are correlated, then control is transferred along a Yes path to a collect pixels step 1012 to form or generate a track/image of a neutron-gas collision event in the gas chamber. The collecting step 1012 continues until a track/image of the neutron-gas collision event is complete– all pixels associated with an event have been collected. Of course, as if with the other method steps, these steps may be performed on a parallel basis. Once a track/image is collected, then the collected track/image is analyzed in an analyze track/image step 1014 to generate event data including color/hue/intensity data and direction data. After track/image analysis, the methods include a compare step 1016, where event data is compared to event data stored in an event database. The database includes color/hue/intensity data from known events, which correspond to data collected from other formations having known solid, liquid, and/or gas compositions and/or event data collected from simulated formations having known solid, liquid, and/or gas compositions. After comparison, interpreted output of the event data occurs in an data output step 1018. Once a logging operations is completed or a logging while drilling operation is completed, then the methods proceed to a stop imager step 1020, which stops image processing unit the initialize imager step 1002 activated.
[0244] Looking at Figure 10B, another embodiment of the methods of this invention, generally 1050, again starts with an initialize imager step 1052, which initializes the imagining unit of the detectors of this invention. Next, the methods then include a capture pixel data on a row by row or column by column basis in a capture pixel data step 1054. Next, the methods include an analyze each capture pixel data step 1056, where data associated with each pixel is analyzed for color, hue, and intensity data. Once analyzed, the color/hue/intensity data of each pixel is compared to threshold values in the threshold step 1058. If a pixel fails the threshold test, then control is transferred along a No path to the analyze step 1056, where another pixel is analyzed. If the pixel passes the threshold test, then control is transferred along a Yes path to a correlated test step 1060. If the pixel data are not correlated with a photomultiplier threshold event, then control is transferred along a No path back to the capture pixel step 1054. If the pixel data are correlated, then control is transferred along a Yes path to a collect pixels step 1062 to form or generate a track/image of a neutron-gas collision event in the gas chamber. The collecting step continues until a track/image of the neutron-gas collision event is complete– all pixels associated with the event have been collected. Once a track/image is collected, then the collected track/image is analyzed in an analyze track/image step 1064 to generate event data including color/hue/intensity data and directional data. After track/image analysis, the methods include a compare step 1066, where event data is compared against event data stored in an event database. The database includes color/hue/intensity data from known events, which correspond to data collected from other formations having known solid, liquid, and/or gas compositions and/or event data collected from simulated formation having known solid, liquid, and/or gas compositions. After comparison, control is transferred to a certainty test 1068, where the identification of the event data is tested to determine whether the interpretation satisfies one or more certainty tests such as R value, percent confirmation test, a matching value test, or any other test to determine how closely the event data correlates with data in the database. If the certainty test fails, then control is transferred along a No path to an update and/or refine database event data step 1070. This step may involve the creation of new event data in the database, updating of event data in the database, or refinement of database entries. In this way, the systems are able to learn information about different formation solid, liquid, and/or gas combinations so that interpretation may be improved and the database of known formation solid, liquid, and/or gas combinations becomes enriched. Then control goes back to the compare step 1066 to re-evaluate the comparision and the certainty test. If the certainty test is passed, then control is transferred along a Yes path to an data output step 1072, where interpreted event data is outputted to the user. Once a logging operations is completed or a logging while drilling operation is completed, then the methods proceed to a stop imager step 1074, which stops image processing unit the initialize imager step 1052 activated.
CIE Color Imaging Analysis
[0245] In the CIE-XYZ Color Coordinate System, the XYZ Tristimulus values describe any visible color. The XYZ system is based on color matching experiments called the trichromatic color theory. Every color may be represented by 3 values, generally expressed as a column vector of values e1, e2, and e3. The space of visible colors is represented in a 3D space. Calculating the CIE-XYZ Color Coordinate System is based on the three monochromatic primary colors red, green and blue, which have absorption maxima of 435.8 nm, 546.1 nm, and 700 nm in a 2 degree field as shown in Figure 11. These were defined as CIE-RGB primaries and color matching function (CMF). XYZ are a linear transformation away from the observed data.
[0246] CIE criteria for choosing primaries X,Y,Z values and Color Matching Functions (CMF) x,y,z values are: 1) CMFs are non-negative over visible wavelengths (i.e., any color may be represented by 3 positive values); 2) equal amounts of the primaries produce white (i.e., X=Y=Z for stimulus of equal luminance at each wavelength); 3) the y color matching function is defined to match the luminous-efficiency function of the human eye; and 4) primaries are as 'tight' as possible around the set of possible colors (Maxwell triangle Projects to equilateral in XYZ space).
[0247] The CIEXYZ color coordinate system is shown graphically in Figure 12. CIE-RGB to CIE- XYZ is shown graphically in Figure 13, where Cr, Cg, Cb must enclose the Gamut. Line Cb-Cr is defined by Y being Luminance Function (the Alychne = line of zero luminance). Line Cr-Cg is tangent at 650+ (z is zero beyond 650). Thus Cr is defined. Equal Energy (x=y=z=1/3) puts constraint on Cb-Cg. Tight around Gamut ! line Cb-Cg is close to green. Cb and Cg are defined.
[0248] CIE RGB space to XYZ space conversion is a mapping that maps Cb Cg Cr to x=(0,0) y=(0,1) z=(10 . The ma in is iven in matrix form as follows:
Figure imgf000065_0001
where y s pre e ne , non nega ve over e v s e wave eng s , – evera un re s, Y– 0..100), the 3 primaries associated with x y z color matching functions are unrealizable (negative power in some of the wavelengths), integral over the CMF gives equal values, CMF are linear transformation away from CIE-RGB and from Long-Medium-Short (LMS) color space.
[0249] CIE chromaticity diagram is a common representative of color signal [x,y,Y] as shown in Figure 14, where X!X/X+Y+Z=x, Y!Y/X+Y+Z=y, Z!Z/X+Y+Z=z and x+y+z=1. Color naming is shown in Figure 15 according to the CIE chromaticity diagram.
[0250] Referring now to Figure 16, tristimulus values of the spectrum X, Y and Z corresponding to the color matching functions are found by multiplying their primes times the spectrum in question. If two coordinates are given the third is automatically determined. The CIE system works on formulas not on color samples. The entire spectrum of fully saturated hues lies on the perimeter of the curve. The CIE system determines the z(Z), y(Y), and x(X) from the spectrum being analyzed from which the matching function values are determined.
A MULTI-DIMENSIONAL LOOK-UP TABLE DRIVEN BY OUR CIE COLOR CHART Math Model of What Is down the Hole [0251] A look up table is a function from one space to another that is defined in terms of a few samples, their corresponding function values and a method for calculating a mapping from one of those samples. Mathematically this is represented as:
Figure imgf000066_0001
where (xk) are the samples in the domain space and f(xk) are the corresponding function values in the range space, and I(x) is the function or algorithm that is used to compute the value in the range space for an arbitrary point in the domain space x. The function I(x) interpolates the output if the point x is within the convex hull of the sample set (xk) and the extrapolates the output if it is not.
[0252] Our multidimensional look up table is used from our color transformation corresponding to their location on the uniform grid in the color space. The points on the grid can be considered our samples. Tables with non-uniform sampling along each axis provide an approximation with fewer samples. For example:
Let the true mapping between the M-dimensional color space C and the N-dimensional color space D be given by the function F(-) where F:C ! D which denotes:
Figure imgf000066_0002
[0253] Consider that the cases are in the range from 0 to P that is, the vector c = ( c1, c2, ..., cm) has the property that 0 # ci # P. The input dimension M would be three for RGB of CIE diagrams. If we let R be the number of samples in each dimension than for each sample input vector our corresponding N-dimensional output vector. Thus there are N entries in the matrix for each of the RM possible input combinations. This yields a total of NRM entries. For case of notation let us assume that M= 3. In this case, the entries for s uniformly supplied matrix which approximates the mapping of our solid values which approximates the mapping F are the values:
Figure imgf000066_0003
where
Figure imgf000066_0004
[0254] The approximate of a value F(c), where c is not on a sample point, is calculated by an interpolation method. Two methods, the tetrahedral and interpolation methods are commonly used. Let us define a function ,(-) is represented by:
Figure imgf000066_0005
[0255] In this case the value of the table at the location (i, j,k } = [14,6,5] is denoted by the following:
,([14, 6, 5]) = F(223, 125, 95, 625, 79.6875) (we use rounded values for simplicity);
Given the arbitrary value c 0 C the problem is to use our approximation for a value from our function F(c). The first step is to determine which samples in the table to use for interpolation. Since the tri-linear method uses all eight points of a cube around the point to be computed, it is easy to determine the approximate samples using sample indexing. The approximation using tri-linear interpretation consists of three steps:
1) Determine the value of the cube that contains point c, which we will refer to
as the cube index.
2) The index [i, j, k] defines the cube with vertices C(i, j, k), (i+1, j, k) ](i, j+1,
k) (i, j, k+1)], (i+1,j+1, k), (i+1, i, k+1), (i, j+1, k+l) (i+1, j+1, k+1)]. 3) Determine the sub-indexing or weigh values within the cube.
4) Computing the interpolation.
Finding the "cube index" of our database called CUBE
[0256] Since M = 3, the matrix consists of (R ! l)3 cubes. Mathematically, the root index d= [d1, d2, d3] = (i, j, k) of the CUBE containing the value c = [cl, c2, c3] can be detennined using:
di = BASE [ci (R ! l)/P] for ci < P, i = 1,2,3 = R ! 2 for ci = P
[0257] The elements (i, j, k) are in the range R ! 2.
[0258] From these values for the root index, we can interpolate our value to be used in our tri-linear interpolation. If the root index is given by the values (i, j, k) < R ! 1, then the set of eight table values that are used in our calculation are given by the following data points:
,(i, j, k) = {,(i, j, k), ,(i+1, j, k), ,(i, j+1, k), ,(i, j, k+1]), ,(i+1, j+1, k) ,(i+1, j+1, k+l), ,(I, j+1, k+1), ,(i+1, j+1, k+1)}
[0259] In addition to the table values, the tri-linear interpolation computation requires subindices into the cube along each of the three dimensions to determine how much weight to give to each of the eight table values in a summation. Assuming that the float values were used to construct the table, the exact sub-indices are given by the elements of the vector as s = c - ci.j.k and the weights are given by the products of the elements of the vectors as:
W = s(R ! l)/P
v = 1 - w
[0260] Graphical illustration of the two dimensional layout of calculating an index for interpolating values in BASE as shown in Figure 17.
Computer Program for Calculating Big Cumulative Imaging Data Base of Geological Data
[0261] The methodology illustrates calculating a value of an integer in the Color Database called BASE using tri-linear interpolation, where the numeric variables are given by v and w
[0262] Values for the variables v and w are stored as sixteen bit numbers (4 Hex). The variable v and w may be expresses as two dimensioned arrays given by v = [v1,v2,v3] and w = [w1,w2,w3]
[0263] The interpolated value methods is based on the Database as follows values are given by ordinals c. Three dimensional vectors are ordinal numbers defined respectively as i,j,k.
Examples [0264] A graph of the CIE XYZ color matching functions is shown in Figure 11.
[0265] The CIELUV color space and its relationship to commonly used color perception terms is shown in Figure 18.
[0266] Color squares for quantifying publishing reproduction accuracy for black and white is shown in Figure 19 for color temperature in a range from 200-700 nm.
[0267] Color sensitivity: correlate the CCD-CMOS imager to the McAdams ellipses as shown in Figure 20. MacAdam ellipses are small ellipses arc actual size, large ellipses are 10 times actual size for better viewing.
Correlating the Vectors X,Y,Z (Red (R), Green (G), Blue (B)) for Rock Characterization
[0268] Given three vectors: [X .................. R] [Y .................. G] [Z .................. B], we can correlate the X,Y,Z coordinates to the RGB vectors to the Color Temperature Coordinates as shown belos.
Figure imgf000068_0001
[0269] Figure 19 correlates with the following X, Y table correlating frequencies to X and Y values as shown below.
Figure imgf000068_0002
Model Interpretation of down Hole Environment Using Fast Neutron Imager
[0270] Using the color temperature locus shown in Figure 20, we can correlate certain chemical types with certain frequencies and to formation properties.
Sample Fast Neutron Interpretation Legend
x1 Light hydrocarbons
x2 High water concentration
x3 Hard mineral reflection (Fe)
Figure imgf000069_0001
CMOS Sensors
[0271] Referring now to Figure 21, a schematic diagram of an embodiment of a CMOS sensor chip, generally 2100, is shown to include CMOS active pixel sensor color imaging array 2102 including green light sensitive elements 2104, blue light sensitive elements 2106 and red light sensitive elements 2108 as shown in the expanded insert. The chip 2100 also includes analog-to-digital conversion region 2110 and an analog signal processing region 2112. The chip 2100 also includes a digital logic regions 2114 supporting interface, timing, processing and output circuitry. The chip 1700 also includes a clock and timing control region 2116 and a pad ring 2118.
[0272] Referring now to Figure 22, a schematic diagram of a typical CMOS sensor chip vertical/horizontal shift registers associated with image acquisition, generally 2200, is shown to include light sensing elements arranged in rows 2202 and columns 2204. The CMOS sensor chip also include vertical shift registers 2206 and horizontal shift registers 2208 resulting in a CMOS sensor chip output 2210. This architecture is used by the CMOS sensor chips to collect and perform initial processing on the pixel data and generating an output for processing by imaging processing units.
[0273] Referring now to Figure 23, a schematic diagram of a memory array architecture for processing CMOS sensor chip output in parallel, generally 2300, is shown to include an input signal 2302 the CMOS sensor chip to an input symbol row decoder 2304. The architecture 2300 also includes a state transition clock input 2306. The row decoder 2304 produces row enabled data channels 2308 connected to memory busses 0 through n associates with a zeroth symbolic trajectory evaluation (STE0) and associated symbolic trajectory evaluation memory columns STE1-m. The processing is controlled by logic elements L associated with each STE element. The logic is triggered by the clock input 2306 and controlled by an automate routing matrix structure 2310.
[0274] Referring now to Figure 24, a schematic diagram of a routing matrix associated with memory array architecture, generally 2400, is shown to include a first end block 2402 and a second end block 2404. The first end block 2402 includes two block switches 2406a&b and two column switches 2408a&b. The second end block 2404 includes two block switches 2410a&b and two column switches 2412a&b. The matrix 2400 also includes a plurality of light element blocks 2414 (a single one shown here). Each light element block 2414 include row switches 2416a&b and elements 2418a-d, which extend vertically and horizontally depending on the number of STE's. The block switches 2406a&b and the column switches 2408a&b and the block switches 2410a&b and the column switches 2412a&b are in communication via light grey communication pathways. Each column switch 2408a&b and 2412a&b is in communication with other column switches (not shown) via light dark gray communication pathways. The row switches 2416a&b are in communication with other row switches (not shown) and the elements 2418a&b via dark gray communication pathways. The block switches 2406b and 2410b and the row elements 2420a&b are in communication via the black communication pathways. The CMOS sensor chip 2400, the register configuration 2200, the memory array architecture 2300, and the matrix configuration 2400 are configured so that image captured by the CMOS sensor chip 2100 is outputted and analyzed. In this case, the output is analyzed to determine the nature and make up of solids, liquids and/or gases in downhole formation.
Interaction of Radiation with Solids
[0275] In constructing a data base of materials that reflect the interaction of radiation with various compositions found geologically there are a number of important variables. Since the materials being bombarded are mixtures, general rules about their packing density is important. The data base of information about these collisions that is constructed over time is extremely important to characterizing the materials that occur during these radiation interactions. At the atomic level, exposing materials to radiation changes them. How these charges are made provides reasonable information that is critically important to characterizing them.
[0276] The state of the matter being bombarded (solid, liquid, gas) is the first determinant that is important. Our first point in this analysis is about the effect of nuclear radiation on solids.
[0277] Bombardment of solids is dependent upon the surface area or cross section being bombarded. Collisions between energy particles and solid surfaces can be calculated from classical mechanics with good accuracy. A moving atom colliding with a stationary atom will be deflected from its course by an amount which is dependent on its energy and its distance; the deflection being greater for smaller energies and for closer approaches. The energy's momentum, transferred to the stationary atom increases as the angle of deflection increases. The probability for any given amount of energy transfer can be measured by a ring shaped region in which the path of an incident particle must lie in order for this energy transfer to occur. This area is the differential cross section for energy transfer.
[0278] In general inelastic collisions are much more frequent while the atom has high energy and elastic collisions become more important after the atom has slowed down. If the moving atom has a velocity much less than that of an electron in a target that electron will usually be left without excitation. If the moving atom has a velocity equal to or greater than that of the electron, electronic excitation becomes probable. A limiting energy E1 can be found such that when the moving atom has energy E less than Ei it will not lose energy to an appreciable extent by ionization and such that when EoEi the ionization losses will exceed those due to elastic collisions by a large factor.
[0279] For insulators:
Figure imgf000071_0002
[0280] Most common insulators have electronic excitation energy I of about 5 eV, and the fermi levels lie between 2 and 12 ev.
[0281] For metals:
where eF is approximately equal to (3p2)b(a0)2(Ne)bER, a0 is the Bohr's radius of hydrogen (a0 = S2/me2 = 5.29 × 10!9 cm), ER is the Rydberg Energy (13.60 eV), and Ne is the number of conduction electrons per unit volume. The Fermi energy of most metals lie between 2 and 12 ev.
[0282] For energies above Ei and below the relativistic region, the following expression for the energy loss per centimeter of path of ionization is:
Figure imgf000071_0001
where E is the energy of the moving atom, v is its velocity, Z1Ne is its charge, x is the distance it has traversed; N0 is the density of the atoms in the medium, m is the electron mass, J is the mean excitation potential of the electrons in the stopping material and Z2N is their effective atomic number. J and Z2Ncan only be found approximately from theory. Z2N is the number of electrons likely to be excited, namely the number for which the excitation energy is less than (m/M1)E and J can be approximated to 10Z2 (eV).
[0283] For rough calculations, it is useful to know that approximately the range R of a charged particle of initial energy E is given by:
Figure imgf000071_0004
where C and g can be empirically determined.
[0284] Moving charged particles produce displacements primarily by elastic collisions interacting essentially one at a time with the stationary atoms. According to the Bohr analysis, it is adequate to assume that in such collisions the moving and stationary atoms interact with the screened Coulomb potential energy of the form:
Figure imgf000071_0005
where r is the separation of the two atoms; and a is the screening constant. At separations on the order of a, the repulsion is lessened by the partial screening of the nuclei by the two electron clouds and at somewhat larger separations the screening is essentially complete.
[0285] Whenever the nuclei of the two atoms approach the distance much less than the screening radius a, the nuclear Coulomb repulsion produces most of the deflection and the collision calculated can be ignored altogether. This calculation is based on the Rutherford Scattering Laws. More distant collisions are partially screened and no simple expressions can be found for the cross sections. Simplicity again sets in for very distant collisions which occur more nearly as if the colliding bodies were hard elastic spheres. The screening radius is given by the formula:
a ^ a0/((Zl)b+(Z2)b)½ 2-6
[0286] The screened Coulomb scattering of intermediate range between the Rutherford and hard sphere limits is governed numerically by the parameter b, given by:
b = 2Z1Z2e2/ìv2 2-7 where ì is the reduced mass given by ì =M1M2/(M1M2), v is the velocity of the incident particle, and b is the distance to which the two nuclei would approach in a head-on collision in the absence of screening (Bohr called this the "collision diameter" and is the reciprocal of the energy of the incident atom.
[0287] The condition for Rutherford scattering for all but the unimportantly small angles of deflection is that the collision diameter must be much smaller than the screening radius b/a n 1. For collisions to be approximately the hard sphere type it is necessary than b/a be much greater than 1. By comparing the energy of the moving atom to a critical energy EA so defined that b/a = 1 at E = EA.
[0288] The elastic collisions are of the Rutherford type when E o EA and approximately of hard sphere type when E n EA.
EA = ER[2(M1+M2)/M2]Z1Z2(sqrt((Z1))a + (Z2)b 2-8
[0289] In Rutherford collisions small energy transfers are more probable than large, the differential cross section for energy transfer:
T to T + dT being ds = C(dT/T2) 2-10
[0290] From energy and momentum conservation theory it is seen that:
Tm = [4M1M2/(M1+M2)2]E 2-9
[0291] Since neutrons carry no charge it produces radiation damage only by direct interaction with nuclei. A fast neutron imparts momentum to a nucleus with which it collides and the nucleus recoils, taking its electron cloud with it. The distribution of recoil energies is related to the distribution of angular deflections of the neutrons. The simplest approximation is that the neutrons are scattered isotropically.
[0292] In hard sphere collisions, all energy transfers from zero to Tm are equally probable and the differential cross section for energy transfer T to T +dT can be shown to be ds = CNdT, where CN = p(a1)2/Tm, a1 is the diameter of the effective hard sphere approximately the screening radius as given by equation 2-6.
[0293] The maximum energy which can be transferred in a collision by an electron of mass m and kinetic energy E is:
Tm = [2(E+2mc2)/M2c2]E 2-17 where c is the velocity of light and it has been assumed that m n M2c2 which reduces to E n mc2. Relativistic Calculations of Particle Bombardment
[0294] Fast neutron scattering theoretically is isotropic, meaning that it does not matter from what direction they are measured; Neutrons in the Mev energy range actually are scattered preferentially in the forward direction. This means that the average energy transferred is less than that calculated under the assumption of isotropy.
[0295] The differential cross section for transfer of energy T to T +dT can be written as
ds = (sT/Tm)dT 2-19 where sT is the total neutron elastic cross section (now considered due to elastic collisions).
[0296] The mean energy transferred is given by:
T = ½Tm 2-20 where sT ranges between 1 and 10 barns ( 1 barn = 10!24 cm2) for neutrons of fission energies. Neutrons from fission have a broad range of energies from 0 -15 Mev with an average of 2 Mev. Calculation of irridation effects assume that neutrons have an average energy 1 and 2 Mev.
[0297] Assuming this the predictive mean energy of primary atomic knock-ons is measured as
T = (4/A)(1+(1/A))!2 ^ 4/A (MeV) 2-21 where A is the atomic mass of the target material. Thus hydrogen, a principal component of hydrocarbons and water receive a mean energy of 1 Mev and carbon 280 keV. The anisotropy effect reduces the mean energy transferred by a factor of between ½ and b in most elements. The correction factor is more important at higher neutron energies.
CASES
Case A
[0298] The scattering involved in collisions that produce displacements is primarily due to Coulomb interaction between the electron and the target nucleus. The threshold electron energy for transferring energy greater than Ed is important for substances with atomic weights greater than about 10 assuming Ed = 25 eV. (Substances with atomic masses less than 10 are hydrogen, helium, lithium, beryllium and boron.) The next 5 in the list are:
Figure imgf000073_0001
Case B
[0299] The total cross section for producing displacements rises steeply from zero at the threshold energy and then becomes constant as the bombardment increases. For Tm between Ed and 2Ed taking Z1 = 1M1 = m the constant cross section approached for Tm » Ed has the value
Figure imgf000074_0001
Case C
[0300] In heavy particle cases the cross section rapidly declines as the bombardment energy decreases.
Case D
[0301] As in particle bombardment, the primary knock-ons are distributed primarily according to the inverse square of the energy. Thus the mean energy transferred to atoms which are displaced are approximatel e ual to:
Figure imgf000074_0002
Case E
[0302] The penetration and energy loss of electrons in matter is more complicated than with heavy particles because of relativist effects and radiative losses. In general, the penetration of Mev electrons is about 2 orders of magnitude greater than that of protons of the same energy and the attenuation of energy with penetration is subject to considerable fluctuation.
[0303] The differential cross section for transfer energy [T to T + dT] can be written as
ds = (sT/Tm)dT 2-19
[0304] Measuring the effect of radiation on atoms and molecules permits the analyzes and calculations to determine and identify solid, liquid, and/or gas atoms and/or molecules that have interacted with initial fast neutrons based on the interactions between returning fast neutrons and gas molecules in the gas chamber of the detector or detectors allowing determination of the properties and characteristics of the materials downhole.
METHODS FOR EVALUATING ROCK, ORGANIC MOLECULES USING LIGHT
[0305] The purpose of this discussion is to describe the mathematical methodology used for calculating the penetration strength of the nuclear sources for imaging a formation while drilling. The indicator that has the greatest effect on the calculations is the percentage of water. Neutrons, in down hole drilling have traditionally been used for this purpose to determine the water table. Our limits on the distance we can detect hydrocarbons depends upon the porosity of the soil and its impact on the energy of the instrument's returning energetic parameters. For calculating the depth of penetration we use Bessel functions to describe the radiative power of our initial source. The resulting energy calculation is based on the penetrating power of the fast neutrons and is not dependent upon the angle of radiation penetration. Our results are based on the speed of the returning fast neutrons and their conversion by our instrument into photons whose returning strength is correlated to the CIE color wheel. We start mathematically with a combination of Legendre polynomials and Bessel functions. These ten functions mathematically define the strength of the returning fast neutrons correlated to the color spectrum.
[0306] For example, the energy depicted by an indicator in the far-ultra violet region is sufficient to demonstrate the power to ionize an atom or molecule by the process:
M + hn ! M+ + e–
[0307] The typical ionization energy, the energy required for this process, is about 10 eV or 960 kJ mol–1.
[0308] Our measurements are subject to the inverse square law as: (a quantity whose power is inversely proportional to the square of the distance to the source of that given quantity), where:
Ia1/r2
[0309] This is true when a source of uniform power is radiated out into a formation. We assume that the radiation will emanate from our radiation source equally in all directions. We use electromagnetic wave equation as a second order partial differential equation. The returning energetic neutron stream reflected from a hard surface will return quickly and would be illustrated with an orange/red color end of the spectrum. The energy of a neutron adsorbed by the hydrogen atoms in porous soil filled with water will appear more weakly and this is reflected by their (violet/blue) color.
[0310] We use Bessel functions of the integer order to mathematically describe the radiative power of our nuclear source. These equations are summarized as follows
Figure imgf000075_0001
where E is the electric field and B is the magnetic field.
[0311] The Bessel functions in the integer order are:
Figure imgf000075_0003
where is the speed of light in a medium with permeability (m0) and (e0) and L2 is the
Figure imgf000075_0002
Laplace operator.
[0312] We use the spherical Hankel functions:
Figure imgf000075_0004
[0313] Bessel functions of half integer order in terms of the standard trigonometric functions include:
Figure imgf000076_0001
[0314] We are measuring the amount of energy in the form of light absorbed by a rock sample as a function of the percentage of the energy of the light transmitted from our nuclear source. We start with a known radiation energy level from our Americium/Beryllium source. We measure the amount of the light absorbed from the radiation directed at the surrounding environment in a 180° arc for each detector. For example, it is measured as:
Figure imgf000076_0003
where I0, no light is absorbed and A =0.
[0315] When I = 0.01I0, the fraction of light passing through the sample is 1/102 and the absorbance is 2. This fraction of light is passed thru our detector and color correlated using the CMOS chip in the detector in our camera. The resulting color coding system, separately derived, is used to identify the substance absorbed. The reason A is the most useful unit of measure of light absorption is that it is directly proportional to the concentration of the sample, C, as well as the length of the light path through the sample cell R expressed by Beer's Law. The higher the concentration of the sample C, the greaterthe amount of the substance in the sample identified. To wit:
Figure imgf000076_0004
[0316] In which the proportionality constant g is called the extinction coefficient. If C is in moles per liter, and R is in centimeters, g has the unit's liter mole–1cm–1 (M–1cm–1) it is referred to as the molar absorptivity. When e is reported without units, the extinction coefficient tells you how strong a particular sample absorbs light at a particular wavelength.
[0317] The absorption is also called the optical density (OD). Our camera's CMOS imaging chip is measuring A. The amount of absorbance A is compared to a chart of materials independently derived for identification purposes. They convey the level of porosity of the resulting sample. Several substances that we are looking for such as water and selected hydrocarbons have known absorption rates. By using imaging absorbance software to screen out some materials, it is possible to identify the hydrocarbons and water in our sample.
[0318] The energy for a hydrogen molecule H2 is 436 kJ mo1–1. There is just sufficient energy in this near violet radiation to disassociate hydrogen molecules into hydrogen atoms. (H2!2H). This is mathematically described in a Balmer series of lines in the emission spectrum of the hydrogen atom. The Energy is associated with the electromagnetic radiation which is related to the frequency of the radiation by the relationship:
Figure imgf000076_0002
where h is Planck constant, which has a value of = 6.62606876 × 10!34Js.
[0319] The energy given by the equation is that associated with a single photon of radiation of frequency v or wavenumber and is extremely small. The wavelength of radiation depends upon the medium through which it is traveling. It is necessary in spectroscopy to convert all wavelengths to vacuum wavelengths using the relationship:
Figure imgf000077_0003
where çair is the refractive index of air, and is related to the speed of light in the two media by:
Figure imgf000077_0004
[0320] The speed of light is defined as c= 2.99792458 × 108 m/s.
[0321] Frequency is independent of the medium in which it is measured because:
Figure imgf000077_0002
[0322] Wavenumber is not independent of the medium but in spectroscopy is invariably taken to be defined as:
Figure imgf000077_0001
[0323] In moving from the radiofrequency to the g-ray region of the spectrum, the photon energy increases. When atoms or molecules are subjected to radiation they suffer more drastic consequences as the frequency of the radiation increases. Frequency rather than wavenumber is usually used in our calculations. Radiation is polarized in a xy plane.
[0324] The visible color range in the electromagnetic spectrum (and in this case our camera/detector) is derived from the resulting energy level:
10–8 to 10–5 (-6 eV 50,000 cm–1 to 400 cm–1)
[0325] The electric and magnetic character of a single photon of radiation is represented by two waves in the xy plane. The wave (or photon) we are capturing in the visible region is traveling in the x direction. When a photon in the visible region falls on the human eye, it is the interaction of the electric component with the retina which results in detection. Conversely, when a photon falls upon our detector, its color is used to identify the substance we are attempting to identify. By loading a table with certain known substances we seek to identify, we limit the amount of searching from a look up table of materials is required It is also the electric character of electromagnetic radiation which is most commonly involved in spectroscopy.
Discussion on Bond Order for Calculating Electronic States of Molecules
[0326] Water is used as the example. The electronic states of the molecules to be identified by our detector are oxygen, hydrogen and various forms of carbon in the liquid and gas states. In characterizing our materials down hole we evaluate each material by its electronic state.
Bond Order= (net number of bonding electrons) divided by 2.
[0327] For example, take oxygen (O2) and hydrogen (H2) molecules which have two pronounced absorption spectra.
[0328] The wave form for a diatomic molecule is Ø = c1÷1 +c2÷2, where 1 and 2 are atomic orbitals (AO) wave functions for atoms 1 and 2 and c1 and c2 are constants reflecting the proportions of ÷1 and ÷2 which constitute the molecular orbital (MO). There are two important rules. The AO must contain the same symmetry with respect to the inter-nuclear axis. The AOs combined must have the same energy.
[0329] In characterizing complex substances we evaluate each molecule using oxygen as an example. There are 16 electrons and the ground configuration with a net number of 4 bonding electrons is:
Oxygen: O2 = (sg1s)2(suls)2(sg2s)2(su2s)2(sg2p)2(pu2p)4(pg2p)2
Using Chemical Analysis of Surlaces as a Determinant
[0330] Using our device to capture surface characteristics during down hole oil exploration, we are concerned with detecting the presence of hydrocarbons or water in the liquid or gas state. Of primary importance is the general applicability of our technique. The verification of the nature of the samples, the type of information we acquire about them, and the detection limit of the technique is what is important. We impose the initial limit in that we are only detecting hydrocarbons or water. This is done initially to impact the speed of the analysis. Other materials are interpreted from the data on subsequent analysis. The energy range and the escape depth of the molecules are specifically linked whether they are in gas or a liquid state. Because of their high energy, fast neutrons have deeper escape depths and less surface selectivity. Elemental selectivity is very important. There is uniform chemical information that can be derived from our analysis on hydrocarbons and water. The approach for using fast neutrons on chemical elements is well understood.
[0331] Using our instrument, we can determine: 1) what geological formation attributes from our research list are present; 2) how much of each element is present; 3) what forms (gas, liquid) are present; 4) the relative percentage of different types of hydrocarbons are present. Our "beam", in this case our stream of energetic neutrons, is incident on the surface and penetrates to the some depth within the surface layer's characteristics. We measure the difference between the number of fast neutrons going out and the photons coming back to interpret the characteristics of the surlace.
[0332] We care most about quantifying the elemental ratios of the hydrocarbon substances. Neutrons out and the interpretation of the photons in are the inventive step in our application. Existing classical measurement techniques cannot identify elements or chemical compounds on surfaces because they must either operate in a vacuum, they are too fragile to be used in a harsh environment, they are not small enough to go downhole, or they are not sensitive enough to meaningfully provide the information required in a timely or useful enough manner. No one technique provides the necessary information to solve a complete problem.
[0333] Calculated as well as experimental thennal neutron sensitivities are available in the literature. Detection sensitivities with small fust neutron unmoderated sources was an approach proven by the US Department of Energy at the Argonne National Laboratory in the mid-1960's.
[0334] The energy and penetration depth of selected particles
Figure imgf000079_0001
[0335] Fast neutron source: (241Am/242Cm/9B with flux of 9 x 107, fast unthermalized neutrons/cm2/s. Counts in the photo peaks of the spectra, per gram target element are plotted in the reference.
Effect of Sampling Depth on Quantitative Surface Analysis
[0336] Consider a material, in this case water, composed of A and B (Hydrogen) and (oxygen) which is richer in component A than B; the depth distribution of A is a simple exponent The concentration of the component is measured periodically at specific sampling depths. Because of its density, it will have lower ratios than materials with higher densities. (See Figure 5 concentration profiles for three hypothetical materials: water, liquid and gas hydrocarbons). Such an analysis enables you to derive two things: 1) the effect of sampling depth on surface analysis; and 2) by deriving data at specific depths you can derive information about the depth distribution of a material in a sample. You can also derive information by varying the angle of the energy source and the surface. Signals deflected from the surface will have enhanced signals from the outer layer and decreased signal intensity from the bulk layers. Our system provides a depth profile which is a plot of the concentration of a material as a function of depth of the surface being analyzed. The functions contributing to the depth are: 1) the actual concentration profile; 2) sampling depth of the energy beam from the fast neutrons; 3) the sampling width of the energetic neutrons; and 4) the observed depth profile. Setting the sensitivity and detection limits for quantitative application is extremely important and can only be verified by experiment. The relationship measures the differences between the material concentration and the measured intensities. The detection limit is the minimum amount of material detected using a spectral line.
Method for the Evaluation of the Absorbance of Light from Selected Organic Molecules
[0337] Embodiments of this invention relate to methods for creating an industrial geological database using electron spectroscopy based on collision between returning fast neutron and gas molecules in the gas chamber of the detectors of this invention. These collisions contain information about interactions between initial fast neutrons as solids, liquids and/or gases associated with a formation or zone thereof irradiated by fast neutrons from a fast neutron source associated with the tools of this invention. The collision data is then used to determine, identify and classify the properties and characteristics of the formation or zone being logged using the tools of this invention. Important properties of light that aid in the analysis of the collision data contained in an image or a plurality of images from the imaging unit of this invention, are given in Table II.
Figure imgf000080_0002
Figure imgf000080_0003
[0338] The rotational state of CO changes with temperature. The spectra of samples in condensed phases also sharpen at low temperature because molecular motion decreases at low temperature. Overlapping bands at room temperature are often resolved at low temperature. A diatomic molecule is simple because it has just a single vibration. Even at absolute zero, this vibration occurs because its molecule cannot have less than a zero point of energy. Polyatomic molecules have a limited number of fundamental motions called normal modes of Vibration. A collection of three particles, water for instance, will have [3• 3 = 9] degrees of freedom. There are three and only three possible rotational degrees of freedom about three mutually perpendicular axes passing through the vibrations.
[0339] In general, a molecule with n atoms will have 3n - 6 modes of vibration. A linear molecule will have 3n - 5 modes of vibration because there is no rotation about the molecular axis.
[0340] A normal coordinate is a single coordinate along which the progress of a single normal mode of vibration can be followed. If the carbon atom C moves 15.995/12.000 as far as the oxygen atom by motion along the normal coordinate we mean that the carbon atom moves a distance Är(C) and the oxygen atom moves a distance Är(O) as:
and
Figure imgf000080_0001
(C)/Är(O) = m0/mc = 15.995/12.000
[0341] Both atomic displacements occur at the same frequency and in phase. Displacement would be measured from the equilibrium atomic separation r0 in the ground state of CO.
[The normal coordinate of CO, q, is equal to (C) + Är(O).]
[0342] The kinetic energy is:
Figure imgf000081_0001
where ëi is a constant.
[0343] Each normal mode of vibration will form a basis for an irreducible representation of the point group of the molecule. This is of concern for the normal critical connection of the book.
TABLE IV
Determining the Symmetries of the Three Modes of Vibration of H2O
Figure imgf000081_0004
[0344] Its value can be computed using a matrix with 12 × 9 elements or summarized by the results shown on the diagonal.
[0345] The operation E is trivial. It accomplishes the following transformations:
Figure imgf000081_0002
Figure imgf000081_0005
[0346] The trace or character of this matrix the sum of the diagonal elements is 9. The operation for element carbon [C] is more interesting:
Figure imgf000081_0003
Figure imgf000081_0006
[0347] The character of the C matrix is !1.
[0348] A streamlined procedure for constructing a similar matrix for (H2O) water has the following rules:
1) Determine the number of atoms which do not change location during each symmetry operation.
2) For each operation, multiple the number of unmoved atoms by the character of Ãxyz at the bottom of the character table. This gives the characters of Ãtot the total representation of all degrees of freedom of the molecule, including translation, rotation and vibration. This is derived from formula:
Figure imgf000082_0001
where ai is the number of times the ith irreducible representation appears in the reducible representation, h is the order of the point group, R is an operation of the group,÷R is the character of the Rth operation in the reducible representation, ÷R is the character of the Rth
i operation in the ith irreducible representation, and CR is the number of operations in the class.
Figure imgf000082_0002
[0349] There are 9 irreducible representations corresponding to the nine degrees of freedom of the three atoms.
Structure of Complexes
[0350] The wavelengths of absorbed light are approximate. The following colors relate from a color wheel the relationship between light absorbed and recorded on the camera and the color of the complex (light transmitted). Color complexes absorb a wide range of colors not a single wavelength. This measures the energy absorbed by a single complex that absorbs a single photon. For calculating a mole of the complex, multiple the result of the following equation by Avogadro's number (6.02 × 1023). The calculation is made as follows:
Ä0 = (6.63 × 10!34)(3.00 × 108 m/s)/437 × 10!9 m = 4.55 × 10!19J
[0351] This is the energy that is absorbed by a single complex that absorbs a single photon. For a mole of the complex, we must multiply this by Avogadro's number 6.02 × 1023:
Ä0(kJ/mol) = 4.55 × 10!19J (6.02 × 1023) = 2.74 × 105 J/mol = 274 kJ/mol
Figure imgf000083_0001
[0352] For solids, (such as rock), photoemission spectroscopy, (PES) is used to analyze the molecular bonding orbitals.
[0353] All references cited herein are incorporated by reference. Although the invention has been disclosed with reference to its preferred embodiments, from reading this description those of skill in the art may appreciate changes and modification that may be made which do not depart from the scope and spirit of the invention as described above and claimed hereafter.

Claims

CLAIMS I claim:
1. A method comprising:
lowering a neutron detection tool into a borehole of an oil or gas well to a location of a formation to be imaged, where the tool includes at least one neutron source, at least one neutron detector, and at least one processing unit, where each detector includes an imaging unit, a gas chamber having a voltage drift region and a voltage unit capable of generating the voltage drift region and where the source and the detector are separated from each other by a distance D1,
irradiating the location with initial fast neutrons from the at least one neutron source, capturing an image or a plurality of images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data,
analyzing the images on a pixel by pixel basis to determine the collision data,
converting the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database,
producing a logging record evidencing the location solid/liquid/gas data, and
classifying the location solid/liquid/gas data.
2. The method of claim 1, wherein the at least one neutron source comprises a single neutron source.
3. The method of claim 2, wherein the single neutron source is an 241Am9Be neutron source.
4. The method of claim 1, further comprising:
conveying the tool within the borehole on a wireline.
5. The method of claim 4, further comprising:
repeating the irradiating, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole.
6. The method of claim 1, further comprising:
conveying the tool within the borehole on a drill string, where the tool is situated in the drill string proximate a drill bit section or situated in the drill bit section or collar.
7. The method of claim 6, further comprising:
repeating the exposing, capturing, analyzing, converting, producing, and classifying steps at a plurality of locations within the borehole.
8. The method of claim 1, wherein the analyzing step comprises:
computing a relative location of each collision between an initial fast neutron and a solid, liquid, and/or gas at the location based on the collision data of each gas-returning fast neutron event,
calculating an energy of each collision between the initial fast neutrons and the solid, liquid, and/or gas at the location,
modifying each calculation due to interactions between the initial fast neutrons and borehole pipe with or without openings in the pipe, and
updating and/or refining database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
9. The method of claim 8, wherein the solid, liquid, and/or gas at the location are characterized and indexed using a hydrogen index.
10. The method of claim 1, wherein:
the initial fast neutrons have energies ranging between 100 keV and 15MeV, and
the gas mixture comprises CF4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF4 and between about 99 vol.% and about 99vol.% 4He.
11. The method of claim 1, wherein each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software.
12. The method of claim 1, wherein:
the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof,
wherein the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location, and
wherein the processing/analyzing unit is local and/or remote.
13. The method of claim 1, wherein the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1.
14. The method of claim 1, wherein the processing/analyzing unit is remote from the tool.
15. The method of claim 1, wherein each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm).
16. The method of claim 1, wherein the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location.
17. The method of claim 1, wherein the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
18. A method for creating and capturing an image based on a collision between a gas molecule in a detector and a fast neutron comprising:
capturing an image or a plurality of images of each collision between a gas molecule of a gas mixture and a returning fast neutron occurring in a gas chamber of a neutron detector, where the returning fast neutron represents a collision between a solid, liquid, or gas molecule and an initial fast neutron occurring outside of the neutron detector and where each image includes collision data including neutron speed, neutron energetics, neutron entry direction, neutron travel path or track through the detector,
determining the collision data on pixel by pixel basis,
indexing a precise neutron location of each collision within the detector and relating it to a physical location outside of the detector from which the returning fast neutron entered the detector creating the image or images, and
classifying a type of the solid, liquid, or gas molecule from which the returning fast neutron originated based on a comparison to a hydrogen index.
19. The method of claim 18, wherein the initial fast neutrons are generated by a single neutron source.
20. The method of claim 19, wherein the single neutron source is a241Am/9Be fast neutron source.
21. The method of claim 20, wherein:
the initial fast neutrons having energies between 100 keV and 15MeV, and
the mixture comprises CF4 and 4He a ratio between about 1 vol.% to about 30 vol.% CF4 and between about 99 vol.% to about 70 vol.% 4He.
22. The method of claim 18, wherein the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
23. The method of claim 22, further comprising:
updating and/or refining database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
24. A system for logging oil and/or gas wells comprising:
a neutron detection tool including:
at least one neutron source,
at least one neutron detector comprising:
an imaging unit,
a gas chamber having
a voltage drift region and
a voltage unit capable of generating the voltage drift region within the chamber, and
at least one processing unit, where each detector,
where the source and the detector are separated from each other by a distance D1, the at least one source irradiates a location with initial fast neutrons, the imaging unit captures an image or a plurality of images of collisions between a gas molecule in the gas chamber of the at least one neutron detector and a returning fast neutron evidencing an interaction between one or more of the initial fast neutrons and solids, liquids, and/or gas molecules present at the location using the imaging unit, where the images comprise collision data including collision energetics data and collision track data, the at least one processing unit: (a) analyzes the image or images on a pixel by pixel basis to determine the collision data, (b) converts the collision data to solid/liquid/gas data at the location based on reference solid/liquid/gas data stored in a solid/liquid/gas reference database, (c) produces a logging record evidencing the location solid/liquid/gas data, and (d) classifies the location solid/liquid/gas data.
25. The system of claim 24, wherein the at least one neutron source comprises a single neutron source.
26. The system of claim 24, further comprising:
a wireline on which the tool is lowered into a well or tripped out of the well or
a drill string or drill collar in which the tool is situated for logging while drilling.
27. The system of claim 24, wherein:
the initial fast neutrons have energies ranging between 100 keV and 15MeV, and
the gas mixture comprises CF4 and 4He in a ratio between about 1 vol.% and about 30 vol.% CF4 and between about 99 vol.% and about 99vol.% 4He.
28. The system of claim 24, wherein:
each detector further includes a power source, a pulse charge circuit and a pulse amplification circuit associated with the voltage unit to form a voltage drift cage generating the voltage drift region, communication hardware and software,
the imaging unit comprises a charge coupled device (CCD) camera, CMOS sensor, or a combination thereof,
the at least one processing unit stores the images captured by the imaging unit, stores tool location data and the collision data, where the tool location data comprises the location of the tools linked to a corresponding physical down hole location,
the at least one processing unit is local and/or remote, and
the at least one processing unit update and/or refines the database of pixel data based on data collected so that the database learns during use of the tools to improve identification of solid, liquid, and gas profiles from the collision data.
29. The system of claim 24, wherein the tool comprises at least two detectors, where the two detectors are separated from each other by a distance D2, while the detector closed to the source is separated from the source by the distance D1.
30. The system of claim 24, wherein each detector has a diameter between 1.7244 inches (120mm) and 8.75 inches (222.25mm).
31. The system of claim 24, wherein the images correspond to a track of an electron generated by the gas molecule-neutron collision and the resulting collision data is compared to reference track image data in a look up table containing an index used to identify the solid/liquid/gas present at the location.
32. The system of claim 24, wherein the collision data comprises color/hue/intensity event data, where each event is color coded representing a proportional relationship between a strength of each interaction between an initial fast neutron and the solid/liquid/gas components at the location and compared to reference color/hue/intensity event data to determine or identify the components at the location or continuously along the borehole during a logging operation or while drilling.
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