US20060202122A1

US20060202122A1 - Detecting gas in fluids

Info

Publication number: US20060202122A1
Application number: US11/079,921
Authority: US
Inventors: Scott Gunn; John DeBliek
Original assignee: Varco IP Inc
Current assignee: Varco IP Inc
Priority date: 2005-03-14
Filing date: 2005-03-14
Publication date: 2006-09-14
Also published as: NO340293B1; GB2438127A; GB2438127B; CA2600290A1; US7741605B2; GB0716165D0; US20090008560A1; NO20074306L; CA2600290C; WO2006097670A1

Abstract

A method for detecting gas in a fluid, the system including flowing fluid bearing gas through a gas trap apparatus, flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the gas, the infrared gas detection system having apparatus for isolating absorption spectra of the gas, producing with the infra-red gas detection system analog signals indicative of levels of the gas, transmitting the analog signals to a first processor for converting the analog signals to digital signals, transmitting the digital signals from the first processor to a second processor, producing with the second processor digital signals indicative of the level of the gas.

Description

BACKGROUND OF THE INVENTION

1. Field Of The Invention
The present invention is directed to detecting gas in fluids, e.g. drilling fluid that has been circulated through a wellbore and, in one particular aspect, to systems and methods for detecting individual hydrocarbons, e.g., but not limited to, methane and propane, with infrared sensing apparatus.
2. Description of Related Art
The prior art discloses a wide variety of systems and methods for detecting gas in drilling fluid or “mud” that is circulated down a drillstring, through a bit, and then back out of a wellbore during drilling. During a drilling operation, the mud is continuously pumped down through the drill string and into the region around the drill bit and then back up a borehole annulus to the surface. Often the mud is made up of clays, chemical additives and an oil or water base and performs several important functions. The mud cools and lubricates the drill bit, carries drill cuttings back up out of the well, and serves to maintain a hydrostatic pressure which prevents pressurized fluids in the earth formation from blowing out through the drilled well.
Various measurements may be taken while drilling a well both of the drilling mud entering the drill string and returning to the surface and of other parameters as determined by tools at or near the drill bit. The measurements at or near the drill bit are typically called measurements while drilling (“MWD”) and provide a log of the drilling operations from which one may attempt to analyze the earth formations which the drill bit is penetrating. These logs are important as they enable the drilling operator to ascertain the presence of oil or gas in the formation being drilled. Mud logging measurements, including temperature, electrical conductivity, pH, sulfide ion content and oxidation-reduction potential of the drilling mud returning from the well may also be made. In addition, measurements may be made on the returning mud to ascertain total hydrocarbon content and to ascertain the presence of certain specific gases such as carbon dioxide and hydrogen sulfide in the mud. The gas content of the mud may serve as an indicator of the pore pressure of the drilled section, and if properly determined can be used to identify “oil shows” and “pay zones”. The gas content of the mud is proportional to the pore pressure of the section being drilled, and if properly determined can be used to identify producible zones.
Several prior art systems and techniques have been used to detect and analyze gas in drilling mud. Gas is typically extracted from the mud by mechanical agitation in a gas trap which is located in a possum belly tank (also called “header tank”) or in a box of a shale shaker. The extracted gas is analyzed for hydrocarbons and/or “total gas”; e.g. by one or more of several different detectors such as a catalytic combustion detector (CCD) apparatus, thermal conductivity detectors (TCD), and flame ionization detectors (FID). Separation and quantification of the different light hydrocarbon (e.g. methane through pentanes) gases are then typically carried out via gas chromatography techniques with similar or different detectors. In certain prior art systems, chromatography techniques require several minutes for analysis and the gas content of the mud is determined for batch samples taken at discrete intervals of several minutes apart.
U.S. Pat. No. 4,635,735 discloses that spectrographic analysis of separated gases permits a continuous analysis of the gas content of the mud. In U.S. Pat. No. 4,635,735, at least a portion of the drilling mud returning from the well is subjected to gas separation in a mud/gas separator. The separated gas is then subjected to analysis in a gas spectral analyzer apparatus (spectrophotometers) to produce a gaseous component concentration signal whose value at any instant represents the concentration at that instant of the given gaseous component in the separated gas. By also monitoring the low rate of the returning mud through the separation device, and the flow rate of the separated gas, a continuous determination is made of the concentration of the given gaseous components in the drilling mud. The drilling mud is passed through an agitating type mud/gas separation device while a carrier gas is simultaneously flowed through the mud/gas separation device. The carrier gas is thoroughly mixed in the mud/gas separation device. The resulting mixture of carrier gas and mud gas is separated from the mud in the separation device and is subjected to analysis in a gas analyzer to produce a component gas signal whose value corresponds to the concentration of the component in the gas mixture. By measuring the carrier gas volume flowing into the mud/gas separation device, the flow rate of the mud into the separation device, and the component gas signal, a continuous concentration signal representing the concentration of the component gas in the drilling mud may be obtained.
U.S. Pat. No. 4,887,464 discloses a system which samples substantially all of the volatile constituents evolving from a well and captures substantially all of the gases evolving from a well by suction and extraction techniques. This system analyzes and provides quantitative determinations of at least the various hydrocarbon gases evolving from a well. The system has apparatus for capturing liberated gases in a bell nipple and return line, extraction means for extracting gases entrained and dissolved in drilling mud, and means for analyzing and quantifying the captured and extracted gases.
In certain prior art systems a gas trap is used which is a metal box immersed in a shale-shaker ditch. Ports in the lower part of the trap allow mud to enter and leave the trap. An agitator motor provides pumping and degassing of mud passing through the trap. In certain prior art systems, the extraction of gas samples from the mud includes bubbling an extractant gas directly through the mud slurry, then separating the gas from the slurry and cleaning the gas for inputting to analytical instruments used for hydrocarbon detection, identification, and quantitative determination. In one prior art system (see U.S. Pat. No. 5,469,917) a supported capillary-membrane sampling device is used which has a grooved support member having a tubular membrane, capillary column, or the like supported within the groove of the support member. This apparatus is used for analytical and/or fluid-separation purposes and allows the elimination of the sample extraction—cleanup train. One particular prior art method includes providing a device with a support member, a capillary membrane permeable to hydrocarbons, and flights on the surface of the support member within which the capillary member is supported; disposing the device in a stream returning mud from a drill hole to the surface of an oil well; passing a stream of inert gas through the capillary membrane, thereby entraining hydrocarbon vapors in the gas stream; and inputting the gas stream containing the entrained hydrocarbon vapors to an analytical instrument capable of identifying and quantitatively determining the concentration of the hydrocarbons.
In several prior art systems liberated gas is directed past a gas sensor, e.g. a gas chromatography sensor, which produces a record of the constituents of the gas. In other prior art systems producing a continuous gas trace, a catalytic, rare earth or a hot wire gas sensor is used. The sensor detects the presence of combustible gases. These devices are also called explosimeters and indicate the relative fraction of volatile hydrocarbons in a gas stream. Often these apparatuses are used to determine if a gas mixture may be explosive. In a typical gas sensor using a rare earth (hot-wire) sensor, an electrical current is passed though the sensor. The sensor heats up and dissipates energy dependent upon its ability to exchange energy with the surrounding environment. In these applications it is the gas flow and gas composition which affect the heat dissipation. Heat or power dissipation results in a change in the resistance of the sensor. The sensor is either epoxy coated for limiting the sensor from thermal effects and for excluding chemical interaction with the sensor's rare-earth portion, or the sensor is stripped of its epoxy coating (see U.S. Pat. No. 6,276,190). Stripped of their coatings, individual sensors have individual responses. Certain sensors which respond differently and predictably to known ranges of hydrocarbons can be used for analyses of the relative concentrations within gases.
In one prior art system of U.S. Pat. No. 6,276,190, two rare earth sensors are provided. Each sensor is sensitive to different ranges of hydrocarbons in sampled gases. Changes in relative concentration of the selected hydrocarbon in the sampled gas result in a change in the output of the corresponding sensor. Thus, where the sampled gas is a mixture of light and heavy hydrocarbon gases, the two sensors generally respond differently as the relative concentrations in the mixture change. The different response can be accentuated by obtaining the difference of the two signals. So, as drilling progresses through subterranean zones having different qualities of gases, the gas sensors provide distinctive outputs dependent upon whether they detect light or heavy hydrocarbons. Different gas qualities are distinguishable using such a system.
In several prior art systems, the total gas from a mud pit is analyzed by a separate instrument, a total gas analyzer, to determine the total amount of gases produced. Also the amount of each individual gas is determined by a second instrument, a chromatograph. The quantity of methane, ethane, propane, isabutane, butane and pentane are each measured by the chromatograph as to the amount each is present. In certain prior art systems the two instruments are combined into one small unit. With a single unit the total gas produced and the amount of each gas is determined. The only lines to the gas analyzer are a single gas line from the mud pit and a single electric power line. The results of analysis are automatically continually available. The results may be recorded every 5 minutes. In one particular prior art method (U.S. Pat. No. 6,374,668) using such a system for analyzing methane series of gas produced from a drilling rig, the method includes: a) pumping a small gas specimen from a mud pit, b) flowing the small gas specimen to a sample valve, c) splitting the flow in the sample valve into a TGA (total gas analyzer) stream and a CG (chromatograph) stream, d) creating a closed time period and normal time period with the normal time period much longer than the closed time period, e) continually flowing, during normal time period and closed time period, the TGA stream to a total gas analyzer, and f) intermittently flowing the CG stream during the closed time period to a chromatograph.
Prior art catalytic and thermo conductive (TCD) sensor technology has been widely used in detecting gas while drilling. These sensors can have several disadvantages. The most inherent disadvantage is that the physical sensor itself reacts with the gas/air mixture flowing by it. This allows several problems to occur. The reaction of the sensor to gas can deteriorate the sensor over time and eventually the sensor's sensitivity and repeatability cannot be duplicated. Consistency can be lost on long wells or when units are in the field for long periods of time. Moisture in the gas/air sample can corrode or react with the physical sensor reducing the sensors sensitivity and lifespan. Several diesel-based and polymer-type mud systems used on drilling rigs will release small particles into the gas/air sample. These particles will react with the compound forming the physical sensor and corrode it or give a false output signal not representing hydrocarbon shows. The mud system particle can have a negative affect on the sensor giving a negative gas value output, this can overshadow the gas being liberated from the well. H₂S, N₂and CO₂can cause sensors to react giving false gas indications, going negative and poisoning the sensor until sensitivity is lost. Any coatings applied on top of the physical surface of the sensor can reduce the sensor's sensitivity. Many prior art sensors which are sensitive-specific to methane (C₁) alone do not work as a total gas detector. Some of these sensors never show any indication when zones rich in heavy hydrocarbons are drilled.
There is a need, recognized by the present inventors, for efficient and effective gas detector systems and methods for using them which provide consistency, repeatability, sensitivity, and have a long lifespan.
There is a need, recognized by the present inventors, for such systems and methods in which there is no physical reaction with the gas being detected or with the fluid bearing the gas.
There is a need, recognized by the present inventors, for such a gas detector which is hydrocarbon-specific and which can detect light hydrocarbons and/or heavier hydrocarbons.

SUMMARY OF THE PRESENT INVENTION

The present invention, in at least certain embodiments, discloses a gas detection system which includes infra-red gas detector apparatus that is specific to hydrocarbon components through which a sample gas flows, a computer system for receiving data from the infra-red gas detector apparatus and for processing such data, a display (e.g. screen and/or strip chart) to display results (in one aspect, in real time) and, optionally, connections and interfaces for providing test results at sites remote from the test site. In certain aspects, the present invention discloses a method for detecting gas in a fluid, the method including flowing fluid bearing gas through a gas trap apparatus; flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the gas, the infrared gas detection system having a first processor and apparatus for isolating absorption spectra of the gas; producing with the infra-red gas detection system analog signals indicative of levels of the gas; converting the analog signals to digital signals with the first processor; transmitting the digital signals from the first processor to a second processor; and producing with the second processor digital signals indicative of the level of gas. In certain aspects, the present invention discloses a system for detecting gas in a fluid, the system including an enclosure; an infra-red gas sensor apparatus within the enclosure; an interface board apparatus within the enclosure and in communication with the infra-red gas sensor apparatus; analog signal apparatus in the infra-red gas sensor apparatus for producing analog signals indicative of a level of gas in a fluid; conversion apparatus on the interface board apparatus for converting the analog signals to digital signals; and transmission apparatus on the interface board apparatus for transmitting the digital signals to a host system.
In one particular aspect, a gas detection system according to the present invention has a methane sensor and a propane sensor, each of which is connected to a corresponding gas chamber interface board (GCIB). The GCIB's provide an interface between the sensors and a drive for an infra-red lamp (one lamp in each sensor); and each GCIB performs amplification and signal conditioning on the sensor output signals and does an analog-to-digital (A/D) conversion of data from the sensors. By doing this on the GCIB's, susceptibility to noise is reduced. The sensors are calibrated on the basis of the digitized signals (digitized signals produced by the GCIB's), thus the calibration can be handled completely in software.
A WSGD main board contains a primary processor for the system which handles communications and control within the system. The main board reads the digitized data from the GCIB's via a serial interface. In certain aspects, the main board communicates with a host computer (e.g. a desk top or a laptop, on site or remote), in one aspect via a wireless modem. The host computer provides the user interface to the system and performs and displays the calibration of the sensor data and generates results for gas content, e:g. but not limited to, methane and propane content.
Systems according to the present invention can measure levels of hydrocarbons (e.g. methane, ethane, propane, butane, and iso-butane). In one aspect, the sensors are calibrated for 0 to 100% volume of gas in air of methane and propane, however both sensors are sensitive at some level to other hydrocarbons. The sensors in such an embodiment do not completely isolate methane and propane from other hydrocarbons, but rather, the methane sensor provides a stronger response to methane and ethane (see, e.g. curve C1+C2, FIG. 6) and the propane sensor provides a stronger response to propane, butane, and iso-butane (see, e.g. curve C3+C4+C5, FIG. 6). Systems according to the present invention can be portable with an easily emplaceable lightweight-polyurethane-encased gas trap, in one aspect with a gas dryer; a component-specific infra-red gas detector system, a laptop computer, and a wireless modem. In one particular aspect, using a wireless modem or similar device, a wireless portable gas monitor is provided.
In one particular aspect, an infra-red gas detector system used with systems according to the present invention has a light source and a dual channel infrared detector with a narrow band infrared filter on each channel. In one aspect, the filters are on a sapphire substrate, and an overall quartz window covers the sensor to protect the filter surfaces and provide additional thermal isolation for the sensor. One channel of the detector is used to detect the infrared absorbed by the target gas; the other channel is used as a reference channel to provide compensation of the sensor for temperature and luminance variations. There is never any physical reaction with the gas/air mixture and thus sensor consistency and repeatability does not deteriorate. In certain aspects, routine calibrations of such system can be good for over 6 months. The sensor is sealed in a capsule and quartz window and contaminants in gases have little effect on its sensitivity and repeatability. High levels of humidity can generate false readings on a sensor, so it is preferable, in certain aspects, to filter out moisture from the input gas stream. The sensors use frequency-specific molecular absorption to indicate hydrocarbons. Particles of mud systems do not react with the sensors and the sensors use filters on the lenses so only the specific frequency for hydrocarbons gases are detected by the sensor. H₂S, N₂and CO₂are at different frequencies and are not detected. The sensors, in certain embodiments, indicate methane and propane in their pure form, but can also indicate gases of multi-component composition. In certain aspects, the methane sensor is calibrated for 0 to 100% volume ethane, or the propane sensor is calibrated specifically for 0 to 100% volume butane, isobutane, or pentane. This does not change the response of the sensors to other gases. This gives a geologist a full evaluation of each hydrocarbon-bearing zone and can indicate secondary zones that were not previously considered.
What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention's teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide new, unique, useful, and nonobvious systems and methods of their use—all of which are not anticipated by, rendered obvious by, suggested by, or even implied by any of the prior art, either alone or in any possible legal combination.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs. To one skilled in this art who has the benefits of this invention's realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent's object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.
The Abstract that is part hereof is to enable the United States Patent and Trademark Office and the public generally, and scientists, engineers, researchers, and practitioners in the art who are not familiar with patent terms or legal terms of phraseology to determine quickly from a cursory inspection or review the nature and general area of the disclosure of this invention. The Abstract is neither intended to define the invention, which is done by the claims, nor is it intended to be limited of the scope of the invention in any way.

DESCRIPTION OF THE DRAWINGS

A more particular description of embodiments of the invention briefly summarized above may be had by references to the embodiments that are shown in the drawings which form a part of this specification. These drawings illustrate certain embodiments and are not to be used to improperly limit the scope of the invention that may have other equally effective or legally equivalent embodiments.
FIG. 1 is a schematic view of a system according to the present invention.
FIG. 2 is a schematic view of a prior art infra-red sensor system.
FIG. 3 is a schematic view of a system according to the present invention.
FIGS. 4A and 4B are schematic views of parts of a system according to the present invention.
FIG. 5 is a schematic of a system according to the present invention.
FIG. 6 shows a typical display of results using a system according to the present invention with, inter alia, specific curves for methane and propane and a calculated total hydrocarbon curve.

DESCRIPTION OF EMBODIMENTS PREFERRED AT THE TIME OF FILING FOR THIS PATENT

As shown in FIG. 1 a gas detector 50 according to the present invention receives gas samples in a polyflow line 37 from a gas trap 12. A drilling rig 11 drills a well 13 into a formation 25. A mud pump 33 pumps mud M in a line 36 into the well 13 down a drillstring 22, to and through a bit apparatus 23, and then up in an annulus 26 to an exit line 27 which feeds into the gas trap 12. The mud M exits the gas trap 12 and flows into a mud tank 17 from which the mud pump 33 pumps the mud in a line 35 back to the line 36. A transmitter or modem 15 (e.g. wireless or hardwired) transmits signals from the gas detector 50 to apparatus or systems such as a computer, computer system, network, or a data acquisition system or apparatus.
FIG. 2 shows a typical prior art infra-red sensor system in which infra-red light from an infra-red source passes through material to be analyzed in a chamber C, then through a narrow band filter, to an infra-red detector. The material flows into the chamber C through a “Sample In” port and out through a “Sample Out” port.
FIG. 3 shows a wireless portable system 70 according to the present invention useful as one embodiment of the system 50, FIG. 1, which has a gas trap system 71, a gas dryer 71 a, a wireless portable gas monitor system 72, a laptop computer 73 (to serve as a host with host software), and a wireless radio modem 74.
FIGS. 4A and 4B show schematically one arrangement for components of a system 80 (like the systems 50 and 70) according to the present invention. The gas detector system 80 has two GCIB's 81 (Gas Chamber Interface Boards). The system 80 has two gas detectors 82 (e.g. two commercially available detectors) paired with the GCIB's 81 with sensors to provide gas data, e.g., in one aspect, methane and propane level data. In one aspect, the detectors 82 provide analog data which, in one aspect, is an alternating sinusoidal waveform whose amplitude is reduced by the infrared absorption in the band of interest. A main board 83 receives digitized data from the GCIB's 81 and, via a wireless modem 84 (or land line) communicates with a host 85 (e.g. a computer system). With host application software 86, the host 85 provides a graphic presentation of gas levels, e.g. methane and propane levels. The detectors 82 are each connected to a GCIB 81 which provides an interface for each detector 82 and a drive for the lamp (infra-red source, e.g. like the infra-red source, FIG. 2) in each detector 82. The GCIB's 81 perform amplification and signal conditioning on the sensor output signals (analog signals indicative of gas level) which, following digitization and calibration indicate actual gas levels (as a % by volume of gas in air) before doing an A/D conversion on board (or off board). In one aspect, by doing the AID conversions on the GCIB's, system susceptibility to noise is reduced. Optionally, analog conditioning is done. In one aspect, the analog conditioning performed takes the alternating waveform from the sensor and rectifies and filters it to give a DC voltage output that can be digitized. The waveform is also inverted before digitization so that the signal will actually increase as the gas concentration increases. The calibration of the sensor is performed on the digitized signals, so calibration can be handled completely in software in the host computer (e.g. a laptop).
Each GCIB 81 has a small microprocessor that controls the A/D conversion on its board and also handles a serial interface to the main board 83. The main board 83 has a primary microprocessor 89 which requests sensor and temperature data from the GCIB's, handles temperature control of the system, does some digital processing, (e.g. exponential averaging) on the sensor data, handles timing and control of the system, and provides a serial interface to the wireless modem 84, through which the host application software 86 can remotely issue commands and receive sensor data from the system. The main board 83 also has non-volatile memory 83 a to store the calibration data for the system.
To read sensor data from the GCIB's 81 the main board 83 sends a command to put the GCIB's 81 into a gas sample mode. When the GCIB's 81 receive this command, they do an A/D conversion, e.g. they do 4096 A/D conversions of the sensor signals over a 1.2 second period (five lamp drive pulse periods), and average these to produce an output value for each sensor channel. The main board 83 reads these values after the 1.2 second period. The main board 83 then issues a command to put the GCIB's into a temperature sample mode, and reads the temperature data for each detector 82. The temperature data is not averaged on the GCIB, although analog filtering (to remove higher frequency noise from the signal in order to improve the signal-to-ratio) is performed prior to the A/D conversion. In one aspect, the main board 83 reads the data from both detectors 82 every two seconds. Some additional exponential averaging may, optionally, be performed on the sensor and temperature data by the main board processor before it is sent to the host 85 via the wireless modem 84. Temperature control can also be performed at regular, e.g. two second, intervals. Case heaters 87 (see FIG. 5) are controlled by a temperature sensor (e.g., part of a temperature control system, e.g. like the “Temperature Controls” 120, FIG. 4B) on the main board 83. If the temperature reading is lower than the case temperature set point, heater resistors 105 are turned on for the two second period. The detectors 82 have a heater 87 and a cooler 88 (e.g. a heater and thermal electric cooler, “TEC”) to control the sensor temperature. A second order temperature control loop is used to modulate the sensor's heater and cooler to provide greater stability of the sensor temperature. In one aspect, the heater or TEC power is modulated so that the power input is related to the temperature error (differential component) to create a proportional-differential (PD) type of controller.
In one particular aspect, data packets containing all the sensor and system data are sent to the host 85 every two seconds. The host application software 86 takes the sensor data and applies calibration information for the unit to generate proper gas readings. The host application software 86 can issue commands to read or write the non-volatile memory 83 a on the main board 83, allowing the calibration information to be stored in the gas detector on the main board 83 rather than, e.g., with the host 85. In another aspect this information is stored with the host. When the host application software 86 is started, it requests the calibration information from the main board 83 in the gas detector.
Each GCIB 81 has two sensor input channels, two temperature sensor input channels, and two infra-red source drive outputs. In one aspect the drive outputs are pulsed at a 4.17 Hz rate and the detectors 82 detect the variation in temperature as the lamps are pulsed, creating a small alternating output voltage. A selected narrow band filter (see the Filter, FIG. 2) filters the infra-red radiation so that the detector is sensitive only to infra-red radiation at a wavelength of interest (e.g. 3190 to 3330 nm for methane, 3330 to 3540 nm for propane). If a gas with an infrared absorption at that wavelength passes through the sensor, less light will reach the sensor, and it will not see as large a temperature variation, resulting in the amplitude of the output signal decreasing. In one aspect, on the GCIB, this signal first goes through a fixed 10 times gain low noise amplifier 81 a (see FIG. 4A), followed by a gain stage with selectable 6, 12, 24, or 48 times gain. The signal is then rectified, inverted and filtered (on the GCIB) to generate a DC voltage output that increases as the sensor signal decreases due to absorption of the light. There is an offset adjustment to set the base output voltage (similar to the zero adjustment), and there is an output gain adjustment similar to the span adjustment. The adjustments on the GCIB do not do the actual sensor calibration, but rather set up a nominal offset and gain for the sensor such that the output is within a valid operating window. In one aspect, these adjustments on the GCIB are done when a sensor is first connected to the board, after which point calibration is handled through software parameters that are stored in the non-volatile memory 83 a on the main board 83 in the gas detection unit.
As shown in FIG. 5, in the system 80 the wireless modem 84 is connected to an antenna 93. A power supply 90 provides power for the GCIB's 81, the main board 83, the wireless modem 84, the detectors 82, a power supply fan 94, a cooler 88, a pump 97 and an air vacuum transducer (flow sensor) 98. The case heater resistors 105 are controlled by a case heater relay 104 powered from 120 VAC. The case heater relay is used to open and close the circuit to maintain the system within an operational temperature range, e.g. above 25 degrees Celsius. The AC power plug 103, circuit breaker 101, and power switch 102 are for power control protection for the entire unit. Power for a gas trap 96 flows through a switch 106 and a 120 VAC plug 107. Optionally a filter FR filters moisture from the gas. A fan regulator 100 provides 9 VDC current to power the fans.
FIG. 4B shows a block diagram schematic for a main board 83.
In one aspect the main board 83 is a PIC micro based data gathering and communications board or card, for receiving analog and digital transducer information and converting it to digital data to be sent to a computer or data acquisition system for examination and/or archiving. A power supply (“External Power Supply”) supplies power. In one aspect the data is sent via RS 232 or, alternatively, over a wireless connection that is based on a wireless modem 84. The data transmission circuitry is set up as a population option where either the modem 84 or a daughter board (not shown) containing the RS 232 is populated. Used in conjunction with the GCIB's 81, the GCIB's interface via an interface 130 directly to the gas detectors 82 and do the digitization of the sensor signals. Four connections to each sensor include power, ground, gas channel output, and reference channel output connections. A serial interface between the GCIB's 81 and the main board 83 is used to read the digital sensor data.
In one embodiment, the main board 83 handles temperature control of the unit and of the gas detectors 82. The case heater 105 is used to maintain a minimum unit temperature to prevent the flame arrestors 87 c from freezing. The flame arrestors have an intake 87A and an outtake 87B. The heaters dissipate heat directly to the required area when necessary. Whenever the temperature reported by the onboard temperature sensor 110 is below the specified threshold, the case heaters are enabled. The heater 87 and thermal electric cooler 88 control the temperature of the gas detectors 82 using the fan 95. Proportional-differential control (e.g. “Temperature Controls” 120) is used for the sensor temperature: to enhance, and in one aspect to provide maximum stability, of the temperature. The temperature set point is specified, as well as a controller gain for both the heater and cooler (multiplier for the proportional term), and a single damping factor is applied to both the heater and cooler (multiplier for the differential term). Control values for temperature control of the unit are programmable via a microcontroller EEPROM 83 c. The temperature control values can be set in the host laptop software and stored on the WSGD PCB microchip on the main board 83.
The main board 83 has three analog to digital channels 131 that accept either a 4-20 mA or 2-5V analog signal from external sources. There are outputs to drive the case and sensor heaters as well as the thermal electric cooler. The on-board temperature sensor in the Temperature Controls module 120 is interfaced through the analog-to-digital converter on the main board 83.
An on-board PIC microcontroller 140 reads the data from the detectors 82, handles control of the unit and sensor temperatures, and performs some processing of the data, such as averaging it to improve the signal-to-noise ratio. It then transmits the information to the host 85 via the wireless modem 84 (or via direct RS 232 link, not shown). The main board 83 can drive LEDs 133 to indicate the status of the card, main board processor and modem. Non-volatile memory 83 a in the microcontroller 140 is used to store temperature control parameters, as well as the unit's gas calibration data required by the host application software 86 to convert the raw sensor readings into calibrated values. The cooler 88 cools the sensors and the power supply. In one aspect, the cooler fan 95 is on top of the cooler 88.
FIG. 6 shows one typical display produced by a system according to the present invention. One curve indicates methane (“C1”); one curve indicates propane (“C3”) and one curve indicates total gas content (“TOTAL GAS”). A numerical read out NR indicates total gas (“tg”); methane content (“mc”); and propane content (“pc”). The date is indicated in the DATE column and the time (actual real time) is indicated in minute increments in the TIME column. The curves and the numerical read outs correspond to real times in the TIME column and to actual depths in the DEPTH column. Rate of penetration of the drill bit for increasing depths is indicated by the ROP curve.
The present invention, therefore, in at least some, but not necessarily all embodiments, provides a method for detecting gas in a fluid, the method including flowing fluid bearing gas through a gas trap apparatus, flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the gas, the infrared gas detection system having a first processor and apparatus for isolating absorption spectra of the gas, producing with the infra-red gas detection system analog signals indicative of levels of the gas, converting the analog signals to digital signals with the first processor, transmitting the digital signals from the first processor to a second processor, and producing with the second processor digital signals indicative of the level of gas. Such a method may have one or some (in any possible combination) of the following: wherein the fluid is drilling fluid and the gas is hydrocarbon gas from a wellbore; wherein the analog signals are transmitted wirelessly; producing with the second processor a visual display (screen, strip chart) of a level of the gas; wherein the production of the analog signals and the production of the digital signals is done in real time; wherein the first processor includes an interface board for receiving the analog signals, for converting the analog signals to the digital signals, and for then transmitting the digital signals to the second processor, the second processor including a host computer for receiving the digital signals and for processing the digital signals to produce an indication of level of the gas, the method further including the interface board receiving the analog signals and converting the analog signals to the digital signals, the interface board transmitting the digital signals to the host computer, and producing with the host computer an indication of the level of the gas; wherein the host computer produces an indication of a level of total gas in the fluid and/or displays said indication; wherein the interface board has a programmable medium programmed to calibrate the infra-red gas detection system and the method further including calibrating the infra-red gas detection system with the interface board; wherein the host computer provides a user interface for conducting the method; conditioning the analog signals with the interface board to reduce noise in said signals; wherein the infra-red gas detection system has gas sensor apparatus and there is no physical reaction between the gas and the gas sensor apparatus; controlling temperature of the infra-red gas detection system; wherein the infra-red gas detection system includes the first processor and the infra-red gas detection system is in an enclosure and heater apparatus and cooling apparatus are connected to the enclosure for controlling temperature therein; wherein the infra-red gas detection system is portable; wherein the gas is hydrocarbon gas; wherein the hydrocarbon gas is methane and/or propane; wherein the infra-red gas detection system includes a gas detector with a detection channel and a reference channel, the method further including detecting with the detection channel infra-red radiation absorbed by the gas, and compensating with the reference channel for variations in the gas; filtering moisture from the gas prior to flowing the gas to the infra-red gas detection system to inhibit or prevent the generation of false readings due to moisture; and/or wherein the infra-red gas detection system includes an infra-red lamp, an infra-red lamp drive, and a gas sensor and the interface board provides an interface between the infra-red lamp drive and the gas sensor.
The present invention, therefore, in at least some, but not necessarily all embodiments, provides a method for detecting gas in drilling fluid, the method including flowing drilling fluid bearing hydrocarbon gas from a wellbore through a gas trap apparatus; flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the hydrocarbon gas, the infrared gas detection system having narrow band infrared filter apparatus for isolating absorption spectra of the hydrocarbon gas; producing with the infra-red gas detection system analog signals indicative of levels of the hydrocarbon gas; transmitting the analog signals to a first processor for converting the analog signals to digital signals; transmitting the digital signals from the first processor to a second processor, producing with the second processor digital signals indicative of the level of hydrocarbon gas; the first processor including an interface board for receiving the analog signals, for converting the analog signals to the digital signals, and for then transmitting the digital signals to the second processor; the second processor including a host computer for receiving the digital signals and for processing the digital signals to produce an indication of level of the gas; the method further including the interface board receiving the analog signals and converting the analog signals to the digital signals; the interface board transmitting the digital signals to the host computer; producing with the host computer an indication of the level of the gas; wherein the infra-red gas detection system has gas sensor apparatus and there is no physical reaction between the gas and the gas sensor apparatus; controlling temperature of the infra-red gas detection system; wherein the infra-red gas detection system includes the first processor and the infra-red gas detection system is in an enclosure and heater apparatus and cooling apparatus are connected to the enclosure for controlling temperature therein.
The present invention, therefore, in at least some, but not necessarily all embodiments, provides a system for detecting gas in a fluid, the system including an enclosure; an infra-red gas sensor apparatus within the enclosure; an interface board apparatus within the enclosure and in communication with the infra-red gas sensor apparatus; analog signal apparatus in the infra-red gas sensor apparatus for producing analog signals indicative of a level of gas in a fluid; conversion apparatus on the interface board apparatus for converting the analog signals to digital signals; and transmission apparatus on the interface board apparatus for transmitting the digital signals to a host system.
In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein and those covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited in any of the following claims is to be understood as referring to all equivalent elements or steps. The following claims are intended to cover the invention as broadly as legally possible in whatever form it may be utilized. The invention claimed herein is new and novel in accordance with 35 U.S.C. § 102 and satisfies the conditions for patentability in § 102. The invention claimed herein is not obvious in accordance with 35 U.S.C. § 103 and satisfies the conditions for patentability in § 103. This specification and the claims that follow are in accordance with all of the requirements of 35 U.S.C. § 112. The inventors may rely on the Doctrine of Equivalents to determine and assess the scope of their invention and of the claims that follow as they may pertain to apparatus not materially departing from, but outside of, the literal scope of the invention as set forth in the following claims. All patents referred to herein by number are incorporated fully herein for all purposes.

Claims

1. A method for detecting gas in a fluid, the method comprising

flowing fluid bearing gas through a gas trap apparatus,

flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the gas, the infrared gas detection system having a first processor and apparatus for isolating absorption spectra of the gas,

producing with the infra-red gas detection system analog signals indicative of levels of the gas,

converting the analog signals to digital signals with the first processor,

transmitting the digital signals from the first processor to a second processor, and

producing with the second processor digital signals indicative of the level of gas.

2. The method of claim 1 wherein the fluid is drilling fluid and the gas is hydrocarbon gas from a wellbore.

3. The method of claim 1 wherein the analog signals are transmitted wirelessly.

4. The method of claim 1 further comprising

producing with the second processor a visual display of a level of the gas.

5. The method of claim 1 wherein the production of the analog signals and the production of the digital signals is done in real time.

6. The method of claim 1 wherein

the first processor includes an interface board for receiving the analog signals, for converting the analog signals to the digital signals, and for then transmitting the digital signals to the second processor,

the second processor including a host computer for receiving the digital signals and for processing the digital signals to produce an indication of level of the gas,

the method further comprising

the interface board receiving the analog signals and converting the analog signals to the digital signals,

the interface board transmitting the digital signals to the host computer, and

producing with the host computer an indication of the level of the gas.

7. The method of claim 6 wherein the host computer produces an indication of a level of total gas in the fluid.

8. The method of claim 6 wherein the interface board has a programmable medium programmed to calibrate the infra-red gas detection system and the method further comprising

calibrating the infra-red gas detection system with the interface board.

9. The method of claim 6 wherein the host computer provides a user interface for conducting the method.

10. The method of claim 6 further comprising

conditioning the analog signals with the interface board to reduce noise in said signals.

11. The method of claim 1 wherein the infra-red gas detection system has gas sensor apparatus and there is no physical reaction between the gas and the gas sensor apparatus.

12. The method of claim 6 further comprising

controlling temperature of the infra-red gas detection system.

13. The method of claim 12 wherein the infra-red gas detection system includes the first processor and the infra-red gas detection system is in an enclosure and heater apparatus and cooling apparatus are connected to the enclosure for controlling temperature therein.

14. The method of claim 1 wherein the infra-red gas detection system is portable.

15. The method of claim 1 wherein the gas is hydrocarbon gas.

16. The method of claim 15 wherein the hydrocarbon gas is methane and propane.

17. The method of claim 1 wherein the hydrocarbon gas is methane.

18. The method of claim 1 wherein the hydrocarbon gas is propane.

19. The method of claim 1 wherein the infra-red gas detection system includes a gas detector with a detection channel and a reference channel, the method further comprising

detecting with the detection channel infra-red radiation absorbed by the gas, and

compensating with the reference channel for variations in the gas.

20. The method of claim 1 further comprising

filtering moisture from the gas prior to flowing the gas to the infra-red gas detection system to inhibit or prevent the generation of false readings due to moisture.

21. The method of claim 6 wherein the infra-red gas detection system includes an infra-red lamp, an infra-red lamp drive, and a gas sensor and the interface board provides an interface between the infra-red lamp drive and the gas sensor.

22. A method for detecting gas in drilling fluid, the method comprising

flowing drilling fluid bearing hydrocarbon gas from a wellbore through a gas trap apparatus,

flowing gas trapped by the gas trap apparatus to and through an infra-red gas detection system for detecting the hydrocarbon gas, the infrared gas detection system having narrow band infrared filter apparatus for isolating absorption spectra of the hydrocarbon gas,

producing with the infra-red gas detection system analog signals indicative of levels of the hydrocarbon gas,

transmitting the analog signals to a first processor for converting the analog signals to digital signals,

transmitting the digital signals from the first processor to a second processor, producing with the second processor digital signals indicative of the level of hydrocarbon gas,

the first processor including an interface board for receiving the analog signals, for converting the analog signals to the digital signals, and for then transmitting the digital signals to the second processor,

the method further comprising

the interface board transmitting the digital signals to the host computer,

producing with the host computer an indication of the level of the gas,

wherein the infra-red gas detection system has gas sensor apparatus and there is no physical reaction between the gas and the gas sensor apparatus,

controlling temperature of the infra-red gas detection system,

wherein the infra-red gas detection system includes the first processor and the infra-red gas detection system is in an enclosure and heater apparatus and cooling apparatus are connected to the enclosure for controlling temperature therein.

23. A system for detecting gas in a fluid, the system comprising

an enclosure,

an infra-red gas sensor apparatus within the enclosure,

an interface board apparatus within the enclosure and in communication with the infra-red gas sensor apparatus,

analog signal apparatus in the infra-red gas sensor apparatus for producing analog signals indicative of a level of gas in a fluid,

conversion apparatus on the interface board apparatus for converting the analog signals to digital signals, and

transmission apparatus on the interface board apparatus for transmitting the digital signals to a host system.