AU8146982A - Methods and apparatus for well investigation and development - Google Patents

Description

METHODS AND APPARATUS FOR WELL INVESTIGATION AND DEVELOPMENT

SPECIFICATION

This invention relates to methods and apparatus for analyzing materials in or from a well borehole and providing the results of the analysis as a function of borehole depth, and for facilitating development of the well.

BACKGROUND OF THE INVENTION One of the most complex and difficult problems in the overall task of obtaining oil or gas from beneath 0 the earth's surface involves the drilling operation itself in which a rotating drill produces a borehole one or several thousand feet deep. Despite the impressive development in recent years of seismic and other exploration techniques preliminary to drilling, the 5 drilling operation itself is one which still involves a substantial measure of guesswork and estimation, based on the experience of the individuals involved, because one can never know in advance exactly what is being or will be encountered by the drill as it passes through various 0 formations. It will be apparent that various factors such as drill rotation rate and loading must be varied depending on the hardness and other characteristics of the formation being cut by the drill, but those characteristics are only known from deductions from 5 events apparent at the surface, such as the amount of vibration felt at the drilling table and the drill advance rate which is known only after the drill has been working in a specific formation for some interval of time. Thus, response to changed conditions is slow. 0 It is also important to be able to know when to stop drilling and use other techniques for recovery of oil or gas. Many fields being drilled today do not involve reservoirs under such pressure that oil suddenly appears at the surface- The oil must be pumped or other 5 techniques must be used to recover it from, for example, oil bearing sands. Thus, partly because of the cost of drilling, it is important to be able to determine rather quickly when a formation of interest has been encountered and penetrated.

Still further, geological evidence can be used to identify particular kinds of strata which are known to exist in a specific relation to oil bearing formations. Such evidence includes lithology composition, fabric such as grain size and porosity, structure, paleontological data such as the presence or absence of certain forms of fossils, and also evidence of the pressure or absence of hydrocarbons and in what form they exist, as well as numerous other data.

Much of this information is not obtainable at all, and that which is obtainable is done so only by relatively expensive and cumbersome techniques usually involving removing the drill string and sending a special tool down the hole to take a core sample which is then brought to the surface and analyzed, or to "log" the hole by electrical or radioactive techniques. In 1928, the Schlumberger Brothers made the first electrical well measurements in the Pechelbrσn oil field in France. Their goal in doing so, and the reason that geophysical well logging has become a standard operation in petroleum explorations since then, is due to the fact that it has been impossible -to observe the geological section exposed within an oil well by visual means.

The following table presents a list of most of the conventional logging techniques presently applied. It should be kept in mind that these techniques have all been developed and are all being used as substitutes for direct visual examination of the sedimentary column in oil wells. TABLΞ I. CONVENTIONAL BOREHOLE LOGGING TECHNIQUES

1. Electrical induction log

2. Induction log

3. Guard log

4. Electrical log

5. Spontaneous potential log

6. Density log

7. Mechanical caliper log

8. Gamma ray log

9. Compensated sonic log

10. 3-D Velocity log

11. Microguard log

12. Micro-electrical log

13. Dip meter log

14. Continuous direction log

15. Neutron log

16. Micro-contact caliper log

17. Epithermal neutron log

18. Cement bonding log

19. Borehole camera

20. Seisviewer

21. Temperature log

22. Thermal neutron decay time log

23. Neutron/carbon log

24. Neutron activation log

25. SNAP/VA logs

During the fifty-two years since that first log, research and investigation by geophysical well logging companies has shown that certain physical parameters can be measured directly or calculated from the actual measurements taken down hole by well logging tools. Those parameters which are directly determined are listed in Table II, and other parameters ^rhich can be empirically determined in an indirect fashion from geophysical well logging data are listed in Table III.

TABLE II. PARAMETERS DIRECTLY DETERMINED BY CONVENTIONAL LOGGING TECHNIQUES

1. True resistivity

2. Water and hydrocarbon saturation

3. 3ulk density

4. Borehole diameter

5. Mud cake thickness 6. Acous-tic transit time

7. Fracture identification

8. Flushed zone resistivity

9. Flushed zone filtrate saturation 10. Mud cake presence 11. Resistivity adjacent to borehole

12. Formation dip angle and direction

13. Borehole direction

14. Borehole angle of deviation from vertical

15. Carbon concentration 16. Elemental density (O, Si, Al, Mg)

TABLE III. PARAMETERS INDIRECTLY ESTIMATED FROM CONVENTIONAL LOGGING DATA

1. Water resistivity

2. Lithology, correlation

3. Porosity

4. Lithology, identification

5. Permeability

6. Young's modulus

7. Shear modulus

8. Bulk Moduls

9. Poisson's Ratio

10. Hydrocarbon displacement

11. Formation structure 12. Location of Stratigraphic features

13. Recognition of sedimentary features

14. Depositional environment

15. Thermal history of basin

5 It should be noted that, in order for all of the parameters listed in Tables II and III to be determined from geophysical well logging data, twenty-five logs must be taken and subsequently analyzed. It is also important to keep in mind that such important 10 parameters as correlation lithology, lithologic type and porosity are not measured directly by any method currently in use. That information, as well as samples from micropaleontological studies, can only be determined through geologic analysis of mud cutting or core samples. 15 Core sampling, either in the axis cf the drill string or in the sidewalls of the drill hole, is the technique which most nearly approximates the geologic examination of outcropping rocks. However, the difficulties in recovering a core sample and the expense 20 involved severely limit the use of actual ceres. Also, due to the expense of recovering cores, a complete analysis is warranted and at present this is only done at a facility such as a core laboratory.

Accordingly, some attention has been given to

25. observing and analyzing material carried to the surface by drilling mud. As is well known, a liquid called drilling mud, containing clays and other materials, is pumped into the well, through the drill string, to facilitate drilling and to carry cut and ground material

30 away from the drill bit, and that material is carried to the surface in the mud. The term "drill mud return" will be used here to refer to the mud as it emerges from the well with the other materials. Normally, the drill mud return is processed to remove cuttings, cunped into a

35 pit, and recycled down the string. Various substances are added to cause the mud to have SDecial characteristics of caking ability, viscosity, etc. , but these are of minimal interest here.

Of greater interest is the material carried by the drill mud return which is that material cut or worn away from the bottom of the hole by the drill bit or by the mud itself along with fluids from formations penetrated which can be water, gas or oil. Interest in this material is shown by U.S. Patents 2,591,737 to Souther, Jr. (1952) and 2,692,755 to Nowak (1954), which recognized the possible value of such material and made some effort to gain information therefrom. Souther was looking for evidence of oil in the mud and disclosed techniques for steam-distilling mud samples to extract vapors from crude in the return and detect evidence thereof. Nowak extracted samples of mud, separated chips or cuttings therefrom and examined the radioactivity characteristics thereof. The natural radioactivity was first measured and then the samples were neutron irradiated and gamma ray activity was measured. The readings could be correlated with depth. _

While these techniques could provide useful information. Souther was able to tell one only about the presence of crude in return, and Nowak examined only radioactive characteristics. Thus, these techniques are of quite limited value.

In addition to the discussions in these patents, it is known that mud cuttings are regularly sampled by simple means at the well site. At given intervals, the well-site geologist or technician physically dips from the mud stream a small fraction of cuttings which are then dried, cleaned and analyzed by simple devices according to the methods given in the following table. As will be recognized, the problems involved in this procedure include the low rate of sampling, the level of competence of the geological technician performing the analysis and the limited data drawn from the procedure for application to overall

geologic analysis of the sedimentary column. The second and third of these problems, of operator competence and limited data output, are partially solved at present by sending sample cuts to a geologic laboratory for further analysis. The overriding disadvantage of this procedure is the time involved which ranges, currently, from forty-eight hours to three weeks.

TABLE IV. GEOLOGIC ANALYSIS PRESENTLY PERFORMED AT WELL SITE

1. Rock type

2. Color

3. Grain or crystal size

4. Major characteristics (major minerals, fissility, etc.) 5. Minor characteristics (presence of heavies, microfossils, etc.)

6. Hardness

7. Approximate porosity

8. Oil shows

The following Table summarizes the common procedures involved with the laboratory analysis of both cores and mud cuttings.

TABLE V. ^• GEOLOGIC LABORATORY ANALYSIS

1. Fluid saturation by: retort method hot solvent method vacuum distillation method

2. Porosity by gravimetric method

3. Bulk volume by gravimetric method

4. Gas volume by: Boyles law method Helium injection method

Resaturation method

5. Air Permeability

OMPI 6. Heavy minerals by: magnetic separation electrostatic separation optical identification

7. Miσropaleontological separation and analysis 8. Insoluble residue analysis

9. Micro-sedimentological examination

10. Kerogen color

11. Vitrinite reflectance

BRIEF DESCRIPTION OF THE INVENTION

Q An object of the present invention is to provide a system for optically examining materials indigenous to the subsurface region adjacent the drill bit, generating information signals about those materials and providing that information to the individuals 5 controlling a drilling operation.

A further object is to provide methods and apparatus for developing optical signals representative of the materials, optically and electrically processing those signals to enhance the useful information therein 0 and identifying characteristics of the materials.

A further object is to provide methods and apparatus for optically, automatically and promptly examining the materials at the surface of the earth to generate the information signals. 5 Yet another object is to provide apparatus for optically examining exposed surfaces of the borehole using optical fibers ' for conducting electromagnetic energy to and from the investigation site.

Another object is to provide a method of 0 conducting energy to a downhole location at a depth to be developed for perforating the well casing and adjacent formation.

Another object is to provide a method of generating steam at the downhole location to facilitate 5 recovery of hydrocarbons therefrom. Briefly described, the invention includes a method of analyzing subsurface earth formations comprising the steps of providing a stored data base including descriptive data on characteristics of geological and paleontological features commonly encountered in materials penetrated by a well borehole; optically examining material indigenous to the subsurface region penetrated by the borehole and forming signals representative of selected characteristics of the material; comparing the signals formed following the optical examination with data in the stored data base to identify the nature of geological and paleontological features present in the borehole; and providing a display of those features identified. In another aspect, .the invention includes a system for separating and analyzing materials from drill mud return for use in combination with a well drilling apparatus of the type having a drill string and bit, means for supporting and rotating the string to drill a borehole, means for delivery drilling mud to the string, and means for conducting drill mud return emanating from the bore annulus away from the borehole, the system comprising the combination of means for receiving and degassing at least a portion of the drill mud return and capturing gas emanating therefrom; means for analyzing the captured gas and providing a plurality of signals representative of the presence of selected constituents in said gas; means for continuously extracting a preselected percentage of the degassed drill mud return; a plurality of serially connected separation means for receiving said preselected percentage and sequentially removing therefrom chips, particles and grains of material in selected size categories; a plurality of optical scanning means for receiving, respectively, the removed material in each of said categories, for optically examining the material for ΞMR characteristics and for providing signals representative of selected ones σf those characteristics; and data processing means for receiving and storing said signals from said means for analyzing and from said scanning means, correlated with signals representative of drilling depth. In order that the manner in which the foregoing and other objects are attained in accordance with the invention can be understood in detail, particularly advantageous embodiments thereof will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:

Fig. 1 is a schematic simplified block diagram of a system in accordance with the present invention;

Figs. 2A, 2B and 2C taken together are a functional block diagram" illustrating the architecture of the processing portion of a system according to Fig. 1;

Fig. 3 is a schematic diagram of a system for obtaining cutting samples for processing in accordance with Figs. 1 and 2;

Fig. 4 is a schematic perspective view of a sample preparation and optical viewing apparatus;

Fig. 5 is a sectional view along line 5-5 of Fig. 4;

Fig. 6 is a side elevation, in section, of one embodiment of an optical sample illuminating and viewing apparatus usable in the apparatus of Figs. 4 and 5;

Fig. 7.is a partial side elevation, in section, of a further embodiment of an optical sample illuminating a viewing apparatus usable in the apparatus of Figs. 4 and 5; Fig. 8 is a top plan view of the apparatus of

Fig. 7;

Fig. 9 is a schematic block diagram of a portion of an optical image analysis apparatus usable in conjunction v/ith the apparatus of Figs. 2 and 4-8; Fig. 10 is a simplified side elevation, in partial section of a down.-hole optical examining apparatus usable in the system of Fig. 1; Fig. 11 is an enlarged partial side elevation of an optical foot portion of the apparatus of Fig. 10;

Fig. 12 is a side elevation of an embodiment of a down-hole optical examining apparatus usable with a drill string in place;

Fig. 13 is a bottom partial plan view of the apparatus of Fig. 12;

Fig. 14 is a graphical illustration of the characteristics of fiber optics usable in the system and particularly the apparatus of Figs. 10-13; and

Figs. 15A-C taken together are an information flow diagram for geological data bases usable in accordance with the invention.

OVERALL INVESTIGATION SYSTEM

Fig. 1 shows a simplified block diagram of a system in accordance with the invention, in a functional form, the system including a data base 20 which is interconnected with a pattern recognition portion of an assembly of data processors 21. Optical examination apparatus 22 is provided to inspect lithologic materials and produce a series of groups of signals which can either be initially in digital form or optical form, subsequently converted to digital form, as indicated by clock 23, the digital signals to be supplied to data processors 21. Drilling operation data is also gathered, including depth and other factors, as indicated at 24, and supplied to the data processors. The pattern recognition processor analyzes signals extracted from the data base and those supplied by the optical examination and digital signal blocks and presents the results of the pattern recognition analysis to a display device 25 which can be in the form of a transitory display on a CRT or by printing of hard copy.

The function of processors 21, in the rather generalized context of Fig. 1, is to analyze each group of digital information representative of characteristics of material optically examined with reference to characteristics of known materials stored in data base 20. The data processors then determine whether the analysis results in recognition of the optically examined material as being a material the characteristics of which are stored in the data base. When this analysis results in recognition, the display unit 20 is provided with a statement that the material is recognized and an identification of the recognized material, along with the depth to which the material is indigenous. The printout or display presents this information together. If the analysis does not initially result in recognition, the new pattern of characteristics can be separately analyzed and added to the data base with suitable identification. The ultimate purpose of the information to be presented is, in addition to recognition information, a statement of the significance of that recognition, i.e., whether it indicates the likelihood of the presence of oil or gas of no such substances.

In addition, the signals from generator 23 along with the drilling operation data are provided to a data store 30 which is a high density storage unit for the purpose of receiving and storing all data relating to a specific borehole for possible different, forms of future analysis. As will be recognized, the output of processors 21 can also be provided to the same or a different high density storage device to retain, in machine-readable form, the results of the comparison process.

Optical examination can provide a wide variety of information relating to the characteristics of mater¬ ials found in, or brought out of, a borehole previously drilled or being drilled. For example, the grain size, shape and distribution of various minerals can be opti¬ cally determined, along with the porosity and the charac¬ teristics of the minerals, i.e., whether they are predominantly sandstone, shale, limestone or dolomite. In addition, microbiological characteristics of fossils existing in the strata penetrated by the borehole can be optically determined. As will be recognized, fossils of various types have characteristic shapes, sizes and these can be determined by optical investigation.

The data base constitutes a library of known materials and their characteristics as to shape, size, distribution, etc.; and also the shapes and other characteristics of the microbiological features which can yield paleontological data. The presence or absence of certain fossil forms is indicative of proximity to formations which can be expected to contain hydrocarbon deposits, and the prompt recognition of such character- istics can be a valuable guide to the desirability of stopping or continuing drilling.

The term "optical examination" as used herein is not intended to be limited to examination with visible light. On the contrary, it is contemplated that various spectral regions of electromagnetic energy wil-1 be used, including ultraviolet, visible light, possibly infrared, and also scanning with X-rays for defraction and spectral data.

A more detailed diagram of a portion of a system in accordance with the .invention is shown in Fig. 2, this figure also including other examination charac¬ teristics including examination of the gases derived, the gas analysis being particularly significant if the materials under examination are derived from drill mud return.

Figs. 2A, 2B and 2C show the major processing portions of the system and identify various items of hardware which are readily available, are compatable with each other and which can therefore be assembled to perform the necessary control and processing steps. It should be recognized that the specific processors and other components identified are, in most cases, not the

OMPI only ones which can be used and that functional equiva¬ lents can be substituted, if desired.

A plurality of transducers 24 provide the various signals representative of the drilling parameters including those from which drilling rate, depth, mud flow characteristics and other related information can either be directly determined or calculated. As previously indicated, these parameters are important because it is from them that depth and lag time can continuously be calculated. These generally analog signals are supplied to a multi-channel signal conditioning unit 31 which normalizes and otherv/ise conditions the signals so that they are scaled as needed, depending upon the choices of transducers used to make the measurements. These analog signals are supplied to a 16 channel analog-to-digital converter (ADC) which is one portion of a CAMAC crate 32. As will be recognized by those skilled in the art, the crate is a commercially available powered enclosure and is the basic unit of a computer automated measurement and control system (of which name CAMAC is an acronym) based on a set of IEEE mechanical, electrical and logic standards including standards 583-1975, 395-1976, 596-1976. Crate 32 includes, in addition to the ADC, a DEC LSI 11/23 processor with a RSX 11/M operating system and DECNΞT distributed communication software. This unit is mounted in a Kinetic Systems 3923 Processor Adaptor to become functionally compatible with the other CAMAC modules. Also included in the crate is a 64K word memory; a DLV-11J Quad Serial Port; and a DEC 488 interface which received input from a gas chromatograph 33 for analyzing gas supplied by the sampling discussed in connection with Fig. 3. The crate also includes a 24 bit digital input module to receive inputs from limit switches on a sample preparation and analysis apparatus 34, to be discussed v/ith reference to Fig. 4; a 24 bit relay control output module to supply relay signals for control of apparatus 34; a 16 channel ADC to receive and convert to digital form position information from the sample preparation apparatus; and an 8 channel digital-to-analog converter for supplying analog control signals to motors and other components of that apparatus.

Crate 32 communicates with other processing portions of the system through the DLV-11J Quad Serial Port, one port PO of which is connected to one port of a similar quad serial port in a master crate 35 (Fig. 2C) . A second port, PI of crate 32 is connected to a quad serial port in a crate 36 in a microprocessor based data processing subunit 37a (Fig. 2B) for image analysis system control and data processing. The overall system includes a plurality of subunits like subunit 37a, four such subunits being shown in Fig. 2B. Unit 37a analyzes chips while units 37b, 37c and 37d analyze sand, silt and clay, respectively. These subunits are substantially identical and, therefore, only unit 37a is shown in- detail. Crate 36 is of a similar nature to crate 32 and includes three 3923 crate controllers, one master and two auxiliaries; three LSI 11/23 and processor adapter units; three 64K word memories; two DLV 11J Quad Serial Ports; a 24 bit digital input-output interface unit; a three channel step motor controller; a video digitizer; a 128K word buffer memory; and RL02 disk controller; and two DL11 Serial Ports, all organized as illustrated. The 24 bit digital I/O unit interfaces with an image analysis system preprocessor 38 which can be an Omnicon Alpha 500. This unit receives optical inputs from an optical system 39 connected through fiber optics to a chalnico^'n video camera 40 which produces a sequence of images in a form compatible with the 500. The output of preprocessor 38 is a composite video signal which is delivered to the video digitizer unit in crate 36.

The three channel step motor controller is connected to the optical stage and focus control 41 which operates in conjunction with optical system 39. The RL02 disk controller operates a 10 megabyte disk drive which is the image work file storage location.

The subunits 37a-d are interconnected through one of the quad serial ports, port PI being connected to port PI of crate 32 and port P3 being connected to port PI of the next processor, these being 9600 baud communication links. Port P2 in each crate is a 9600 baud diagnostic port, and port P0 in each crate 36 communicates through one port in a DLV 11J quad serial port in crate 35. For reasons of capacity, the DL 11 serial ports are coupled to the second DLV 11J quad for intracrate communication. It should also be noted that the top DEC LSI 11/23 microprocessor runs an RSX 11/D operating system used for crate communication, crate control, position stage and focus control. Alpha control and Alpha data collection. The second and third LSI 11/23 microprocessors perform video image processing and Alpha data processing for classification of physical characteristics of specimens.

Turning now to Fig. 2c, it will be seen that crate 36 includes three 3923 crate controllers (one master and two auxiliaries) ; three LSI 11/23 and processing adapters; three 64K word memories; a 300 megabyte disk 43; three DLV 11J Quad Serial Ports; a 20 megabyte fixed head disk controller which controls and communicates with a DEC 20 megabyte fixed head disk 44; a FPS 120 controller coupled to a FPS 120 floating point and array processor 45; a DL 11 serial port; an RL02 disk controller operating with an RL02 ten megabyte disk and drive 46; a 300 LPM printer controller communicating with a Printronix 300 P line printer 47; and a color graphics controller communicating with a Ramtek Color Graphics CRT 48. The bottom quad serial port communicates with a data display CRT 49 such as a Lear Siegler ADM3A and, through a fiber optic link including two fiber optic

transmitter/receiver units, with a data CRT 50 located at the drill platform.

The top LSI 11/23, running with RSX 11/M operating system, provides loading on all other pro- cessors of the crate using DECNET protocol, control of the other processors and maintenance of data bases. The second LSJ 11/23 (also running RXS 11/M) provides access to the floating point peripheral processor for processing pattern recognition routines as well as the geological classifier analysis. The bottom LSI 11/23 provides graphics and data output functions.

As will be described hereinafter, the system, when used in conjunction with flowing mud to analyze the materials extracted from drill mud return, includes an agitator for removing gas from the mud and analyzing that gas. Thus agitator fluid level and the degassed mud weight or density and characteristics of the samples of degassed mud, such as density, flov/ rate and the like, can be supplied. It is important to continuously track the characteristics of the well itself during drilling, which characteristics can be continuously changing. When analyzing materials derived from drill mud return, it is important to continuously keep track of the depth from which materials are being brought to the surface. In order to determine this, it is necessary to know the depth of the well, along with the mud flow rates and the like, from which the delay in bringing the material from the locations adjacent the drill bit to the surface can be determined. Thus, the total depth of the well, determined from the number of sections below the kelly and the position of the kelly must be known to give a depth. The casing depths and diameters along with pipe lengrhs and diameters must also be known for calculating the total well volume. This, in conjunction with the mud flow rates, permits calculating, with reasonable

__OMPI y H accuracy, the depth from which the materials are derived at any given time.

The geological data base (GDB) includes high speed disc data storage in units 43 and 44 operating with the recognition processor which accesses to the central managing processor to obtain processed data from the optical, σhromatographic and other analysis and make "comparisons" with the data found in the data base storage. The GDB is a matrix of geologic information through which geologic parameters may be classified to produce a new set of specific characteristics of greater substance than was possessed by the original input parameters alone. A simple example will illustrate this concept.

If an analysis describes particles of quartz sand of a certain size and angularity, that information alone has no true significance. However, when applied through a matrix of information based on the geomorphological principle that detrital sedimentologiσal material becomes smaller in size and more well-rounded as it is transported by fluvial prosesses from its source, then the size and shape characteristics of the sand that was analyzed produces an indication of the location of the sample point with respect to the source of the sand.

Three types of GDB's can be constructed. They are: areal, columnar, and a combination. The areal data base contains information with respect to geologic materials and conditions over a horizontal area. The columnar data base contains similar information through a vertical scale. The combination GDB contains both areal or horizontal and columnar or vertical information.

It should be kept in mind the difference between physical location and chronologic relationship in stratigraphic relationships. A transgressive shore line v/ill produce a continuous areal deposition, but the time of deposition of those sediments varies across the area. In a similar sense, the columnar or vertical GDB will be based intrinsically upon the overriding principle of stratigraphy, that is, super-position. The principle of super-position simply states that that which lies above came later. This principle is violated only through structural realignment by faulting or overturned folds.

Examples of these three types of geologic data bases can be given. A structural contour map is an areal data base. A stratigraphic column is a vertical data base. The complete stratigraphic analysis of a depositional basin in area, depth and time combines the characteristics of both. Numerous geologic data bases have been formulated, but are not in a computerized format. However, within the past 15 years, numerous applications of the concept of constructing a data base covering a defined and partially explored region, with automatic data processing as a basic constraint, have been performed. A computerized data base of all geologic, geophysical, petrological and hydrographic data for the entire surface of the United Republic of Tanzania is in compilation at this time.

Of particular usefulness and relevance to the system disclosed herein are several available data sources from which different forms of data can be drawn to form a GDB for the present system or for other pur¬ poses. These sources are well known to geologists and exploration companies and are widely used. Two of these data bases, known as API and GEOREF, are available through ORBIT System Development Corp. , 2500 Colorado Ave., Santa Monica, California. In addition, considerable data is available from the Texas Well Log Archive, at the University of Texas, Austin, Texas and the Petroleum Data System, University of Oklahoma, Norman, Oklahoma. Related data is also available from numerous commercial organizations such as T-D Velocity Trades, Inc., 2400 McCue, Houston, Texas.

OMPI Two specific but interrelated forms of GDB can be employed. One is for developmental fields, and the other for exploration plays.

The Development GDB is defined with respect to specific basins including known reservoirs, and already documented stratigraphic columns. It contains areal and columnar relationships correlative to known geology throughout specific basins matrixed against characteristics which are essentially equivalent to parameters measured. Therefore, given sets of measured parameters in a new well within a basin under development, automatic synthesis through the Development GDB will produce information as to wherein space (position in the basin and in the lithostratigraphic column) and time (chronostratigraphic position) is any part of the well being drilled or logged. Additionally, qualitative information can. be directly analyzed from the parameters and indirectly through correlation with the GDB matrix regarding the reservoir characteristics within zones intersected by the well.

The Exploration GDB will be defined with respect to general concepts of sedimentary environment, and global or regional stratigraphy. In its first application in a given area, the Exploration GDB will correlate the parameters measured with those general concepts, then gradually will grow towards a form of Development GDB. The conceptual basis of the Exploration GDB is to reorder and rationalize measured parameters from the standpoint of general stratigraphic theory to provide a continuously updated environmental model of the sedimentary column through v/hich the well is being drilled.

Both forms are based, not only upon specific and general stratigraphic information and theory, but also take into account other related disciplines in¬ cluding seismic stratigraphy and the micropaieontological aspects of biostratigraphy. It will be recognized that

OMPI the information derivable from several wells in a speci¬ fic basin can be correlated to produce a three dimen¬ sional representation of the stratigraphy in that basin, giving increasingly reliable and useful information about that specific basin as the number of samples increases. Further, information about a basin can be applied to other basins which show similar stratigraphic charac¬ teristics even though they lie in other parts of the world. Thus, the system is capable of permitting_, pre- dictions in new fields, much more expeditiously than has previously been possible.

Fig. 3 shows, in a rather schematic diagram, a system which can be employed to recover and separate materials from drill mud return for analysis. To the left of Fig. 3 some of the basic elements of a drilling mechanism are shown including the well and casing 60 and a drill string 61 which extends into the well, the string having a bit 62 at the lower end thereof forming the hole. The string is rotated by a drilling table 63 in a well-known manner.

Drill mud is normally accumulated in a suction pit 64 and extracted therefrom and conveyed through a conduit 65 by a mud pump 66 and into the drill string, under pressure, to assist with the drilling operation. The mud emerges through bit 62 and flows upwardly in the annulus surrounding the string. This drill mud return is extracted through a conduit 68 and, in the normal system, is processed and returned ultimately to a settling pit 69 v/hich leads back to the suction pit for reuse of the mud. In the system of Fig. 3, the mud is delivered to a degassing agitator indicated generally at 70 in which the mud is forcibly agitated to permit gases trapped therein to emerge into the upper portion of the agitator chamber. Any such gases are extracted through a conduit 71 and at least a sample thereof is delivered to a gas detector and gas chromatography apparatus for analysis as previously described. Excess gas can be bled off through a conduit 72 to a flare.

The degassed mud is conveyed through a conduit 73, the density thereof being measured by a density measuring device 74 in the conduit. The mud is then split in a flow splitter 75 and a portion thereof is delivered through a conduit 77 to a series of separating devices. Devices 78 and 79 are connected in conduit 77 to measure the sample density and the sample flow rate for delivery to the data processing equipment. The remainder of the mud, other than the sample, is conveyed through a conduit 80 to a decanting centrifuge 81. The coarse materials from the drillmud return are conducted through a conduit 82 to a waste pit, and the remainder of the mud, containing fine sand and silt, is conveyed to a series of separators indicated generally at 84 for removing sand and silt and for salvaging baritε from the mud, the partially cleaned mud being returned through conduit 85 to the settling pit 69. After settling, the mud can then be reconditioned by the addition of various materials in the suction pit for reuse.

The degassed mud sample on conduit 77 is delivered to a series of separators 87a-87f which, sequentially, remove chips, coarse sand, fine sand, coarse silt, and fine silt, the final separator being a clarifier to remove clay which may remain in the mud. The outputs of these separators are largely dewatεred particulate materials in the various sizes as determined by the separators, and the particulate fractions are delivered to individual dryers 89a-89f. Each dryer is a continuous belt drying filter in which a continuous conveying belt carries the chip, sand silt or clay fraction supplied thereto through a chamber which is subjected to a vacuum, each chamber being coupled through a conduit 90^' which is connected to a wet-type low vacuum centrifugal pump 91. Clarified water from separator 87f and water extracted by pump 91 are delivered for disposal or to a liquid chroma ograph for further analysis through a conduit 92.

The dried particulate material fractions are removed from the drying chambers and delivered to further splitting devices 93a-f each of which extracts a sample, through conduits 94a-f to be delivered to optical scan¬ ning equipment. The remaining material not included in the sample is conveyed to crushing equipment wherein the particles are crushed, in the case of the chip and sand fractions, and grinding operations, in the case of the ship, sand and silt, so that the material can be sub¬ jected to X-ray analysis. The clay fraction sample is delivered directly to X-ray analysis, the remainder thereof being discarded. As previously indicated, a primary objective of the systems of the present invention requires on-site automatic logging and geological assessment of drilling operations from either surface or down-hole methods to help the on-site geologist. Since it has been recognized that optical methods provide sufficient information to replace present petrological and logging techniques, the optical methods must be incorporated in a system to meet this primary objective. In order to be applicable to both surfaces and down-hole applications, the system is based on a hybrid of mechanical, optional, electrical and computer subunits. Although the sensing mechanism and specimen surface preparations will be different for the surface and subsurface configurations, the data processing portion of the system is essentially consistent. Thus, the system is divided into three major system areas, specimen preparation and optics system, processing optics systems, and data processing system.

The specimen preparation and optics uses, in part, methods developed for petrography and optical mineralogy adapted to geological samples. These methods require automation to provide on-site automated operations. There are three generally accepted forms of useful petrolographic samples, each one lending itself to different types of inspection techniques. One such type is the thin section (0.3 millimeter), a second is the one-sided polished section, and the third is the granular sample. The thin section combines the advantages of transmitted light and reflected light examination. However, its preparation by totally automated techniques is, at the present time, more complex than the results justify, primarily because considerable hand manipulation and finishing is necessary, making the preparation overly labor intensive and therefore less attractive.

The one-sided polished section performs well in reflected light analysis and in addition lends itself to cathodoluminescence techniques. An apparatus for preparing sections of this type is shown in Figs. 4 and 5, Fig. 4 being in a rather schematic form. As seen in these figures, the apparatus includes a track 100 which is generally circular and can be continuous, although it is illustrated in Fig. 4 as having an interruption for the removal and replacement of sample-holding platforms. A ring gear 101 extends concentrically below the track and is supported in fixed relationship with respect to the track. The track supports a plurality of platforms 102, only one of which is shown in Fig. 4, each such platform having wheels 103 to ride on the upper, flat surface of the track, a support and drive structure 104 extending downwardly from the platform through an annular gap 105 in the track itself. The drive can include a motor driving a pinion gear 106 which engages gear 101 so that when the motor is energized the platform is driven around the track. Laterally extending guide wheels 107 attached to the support mechanism prevent lateral movement of the platform with respect to the track. Each platform supports, on its upper surface, a chip binder mold 108 which can include a mold 109 made of a material which can support the mold but permit release therefrom, a suitable arrangement for this component being a Teflon surface having transversely extending grooves or flutes.

The apparatus further includes a sequence of components to supply, bind, grind and examine the speci¬ mens as they are carried by the movable platform around the track. These are shown schematically in Fig. 4 and include a chip supply 110 which receives chips from these drying and splitting devices 94a-f shown in Fig. 3 and can consist of a delivery hopper or conveyor having a lower surface with a distributor for spreading a rela¬ tively even layer of chips, granules or particles onto the Teflon surface of the mold. As previously indicated, a plurality of platforms, substantially end-to-end, would be provided on the track to render the system as contin¬ uous as possible. It should also be noted that the chip supply can include, or be preceded by, an impregnation device for impregnating the specimen pores with a liquid which sets to give a hard, easily polished product, one such liquid usable for this purpose being methylmet^'hacry- late. This preparation may not be necessary for many forms of specimens, but would be particularly appropriate to those forms of mineral deposits which are relatively easily broken up or otherwise destroyed in the absence of a compound of this type.

After spreading of the specimens on the mold, the mold is delivered to a station including a binder supply 111 which dispenses onto the mold and specimens a binding material capable of relatively rapid setting to form a plate containing the specimens. A suitable binder for this purpose is a low melt temperature die cast alloy such as alloys normally used in die casting having lead and tin as primary components. It should be recognized that this material is reusable. • It will also be recognized that polyester and epoxy resins can be used, such . components being selected for short setting times and, -since they would probably not be reusable, low cost.

Following this station is a setting air supply which provides either cooling or heating air onto the surface of the particle and binder mixture, cooling air being chosen if a low melt temperature alloy is employed as the binder, and heating air being chosen if the binder is a curable thermo-setting resin.

The specimen arrays produced by using these binders in the manner described will be submitted to analysis by reflected light. Accordingly, the surfaces thereof must be polished to a degree in order to permit this inspection. For this purpose, a plurality of grinding drums, such as drums 113 and 114 can be provided to engage and grind the exposed surface of the specimen plates. These drums are provided as being exemplary, and it will be recognized that belt grinders, or other forms of grinders can be used. Of significance is the fact that the grinders are of graded fineness, i.e., a rough grinding drum is followed by a smoother one, etc., until the desired degree of flatness and polish is achieved. It should be noted, however, that the polishing is not intended to achieve anything approaching optical flatness but, rather, is to reach a rather uniform degree of flatness so that the results of the investigation will not be altered by irregularities.

A cleaning station 115 which can include one or more vacuum or positive pressure air-jets, follows the grinding stages to remove loose material from the surface, after which the sample plates are passed under the optical examining stage indicated at 116. At stage 116, the polished surface of the specimen plate is illuminated with light of desired wave lengths, and light emanating from the specimens is received. After the optical examination, the specimen plate is removed and can be preserved for archival purposes or, particularly if the alloy binder is used, subjected to heat for recovery of the binder and discard of the mineral material. The platform is then recommenced on a new journey around the track.

Fig. 6 shows, in greater detail, a portion of an optical examining apparatus 116 usable in the apparatus of Fig. 4 and includes a support 120 lying above and substantially parallel with the upper surface of the specimen plate 109, the upper surface of which has been ground and polished. Support 120 has apertures therein for receiving a plurality of fiber optic connectors 121a-y, each of which extends transversely perpendicular to the path of travel of the specimen plate, the general direction of which is indicated by_. arrow 122. Each fiber optic connector contains a plurality of optical fibers, the flat ends of which are exposed so that they face downwardly toward the specimens. Selected ones of those connectors can also be disposed in generally concave portions of support plate 120 as shov/n at 123 to receive connectors such as 121c and^' 12Id. Connectors such as 121c are coupled to at least one source of electromagnetic energy 124 which provides light of a preselected wave length to illuminate a portion of the surface of specimen plate 109, and the fibers associated with connector 121d are connected directly to one of a plurality of ^• receivers 125. Thus, light emanating from the exposed ends of the fibers in connector 121e illuminate the specimen region and the receivers receive light emanating therefrom, either reflected or as a result of luminescent activity in the specimens.

Connectors such as 121a and b are arranged so that a selected number of those fibers convey light from sources 124 to the specimen surface, while the same or other fibers in the connector are coupled to receivers 125. With this arrangement, regions of the sample plate surface can be illuminated with various wave lengths of cF.n light and images resulting from that illumination are conveyed by optical fibers to the receivers for analysis. Because of the provision of a plurality of the connec¬ tors, and the arrangement of those connectors extending substantially entirely across the specimen plate surface, each specimen plate can be investigated using as many different wave lengths as are needed to consider various reflectance and luminescence characteristics of the specimens contained therein, as plate 109 is continuously or step-wise carried under support 120. It is, of course, important that each set of samples be depth correlated so that the optical input information is referred to the depth from which the samples came.

Figs. 7 and 8 show a further embodiment of an optical examining apparatus which can be used in addition to that shown in Fig. 6, or in place thereof. This apparatus includes a substantially hemispherical shell 126 having a plurality of fiber optic connector locations 127, each including an objective lens 128a and a connec¬ tor body 128b which receives and holds at least one light transmitting optical fiber 129t and at least one recei¬ ving fiber 129r. The transmitting and receiving (or source and image) fibers are connected to a number of receivers and selectable light sources as generally described with reference to Fig. 6. The locations 127 are arranged on radii and concentric circles of the hemispherical shell 126 to transmit light and receive reflected light at known angular relationships so that angle-related reflectance characteristics of - he specimen material positioned under the hemisphere can be deter- mined.

The receivers, being coupled to a relatively large number of fibers, are the initial input to the portion of the data processing system which will analyze the characteristics of the specimens. The data process- ing system extracts information via the optical system from prepared specimen surfaces and then interprets the information. The system is an integration of optics, video and digital units. At this stage, it should be noted that selection of the data processing system encompasses the selection of processing methods. It is possible to use substantially pure digital processing or a mixture of optical processing and digital processing. Whereas optical processing provides the fastest methods, digital methods provide the most flexible. Optical processing is analogous to analog computing, whereas digital methods rely primarily on numerical and discrete sample data analysis computing techniques. Geological assessment of data, as well as presentation of reduced data, requires digital computations.

Digital processing requires transformation of the optical signal into a matrix of discrete points, called "pixels". The unit which performs this operation is typically a video camera and video to digital converter for image information. Additionally, new solid state arrays using charge coupled device technolog are also used. Once the optical information is converted to a sampled digital signal, standard computer processing techniques are used. Since a typical stored image matrix contains 660,920 pixels, typical operations of this sort require an extensive number of multiplications and additions requiring considerable computer execution time. Thus, the hardware is capable of reducing the size of the image matrix. Once the image has been analyzed, the data processing system performs other analyses. At the same time, control of the entire automatic processing machine must continue. Thus, the requirement for parallel execution of processors arises. It is therefore highly desirable to use the mixture of optical and digital processing, using optical image processing to remove background and accomplish initial processing which is a form of filtering, and then converting the partially processed images into pixels which can be handled by the digital data processing aspects of the system. Since the basic premise of the system of the present invention involves optical information in the form of images, either from an objective lens on a microscope or as extended through the use of fiber optics, the basic requirements for processing are the same. Image processing techniques involve the spatial measurement of features. Thus, an image is characterized in a two-dimensional function by intensity, i.e., intensity as a function of X and Y coordinates. This intensity is commonly called grey level. Digital techniques parallel temporal signal processing in that the image intensity is sampled at some X and Y interval. This sampled point is called a pixel. Analog methods called optical processing uses lens, mirrors and spacial filters to process complete fields.

Fig. 9 shows an optical processor apparatus usable in conjunction with the apparatus of Figs. 2, 6, 7 and 8 and includes a multiple light source 130 which includes sources of light at preselected wave lengths usable to determine characteristics in the specimens prepared in accordance with Fig. 4. The light produced by the source is passed through an aperture and lens assembly to direct the light from source 130 along desired channels. One or more rotating filter wheels 132 can be incorporated in one or more of the channels to refine the wave length selection, and the light can then be passed through a polarizer assembly which is usable to produce polarized light in one or more of the channels for extinction and other analysis. Finally, the light is conducted to beam launch optics which is a coupling mechanism for introducing the light into optical fibers such as fibers, or groups of fibers, 135, 136 and 137 which are the source fibers for optical assemblies 121a-y, discussed in connection with Figs. 6, 7 and 8. It will be recognized that the fibers illustrated in Fig. 9 can be groups of fibers, and that many more fibers than those illustrated would normally be employed. The light received from the specimens and conducted through the optical assemblies 121a-y is conveyed through image fibers 140-142 which, again, are illustrative of a larger number of fibers, for connection to electro-optical mechanical multiplexing assemblies 145a-y, each of which includes a movable coupler 146 and a drive unit 147, each of couplers 146a-y being movable to align a portion thereof with a single output fiber or group of fibers 148a-y. Couplers 146 are in the nature of optical selector switches such as shown, for example, in U.S. Patent 4,239,330, and permit selection of one or more fibers constituting the outputs from the optical assemblies 121a-y, the outputs 148 thereof being a number of selectable positions. Drivers 147 can be step motors, or the like, capable of moving the couplers to the desired position as a function of a digital input. Fibers 148 constitute the input to a similar selector unit 150 including a ^' drive 151 and a coupler 152 to select the outputs from the selectors 145 for delivery to a microscope 154 having variable focus, the output of the microscope being a partially processed image which is delivered through an optical path 155 to the processing apparatus shown in Fig. 2. A beam splitter 156 can be provided to sample a portion of the image for delivery to a focus detection unit 158 associated with a icroproces- sor and control logic unit 159. The microprocessor and control logic is programmed to sequentially select fibers by supplying control signals to a fiber select unit 160 in accordance with a preselected sequence, and to control the focus of microscope 154 by a focus drive 161 which provides control signals to a focus adjusting step motor 162.

The optical and image processing combines optical physics and digital sampling analysis techniques to process information from an image. The present apparatus involves image analysis, a general theoretical discussion of which can be found in the text "Theory and Application Digital Processing", Rabiner and Gold (Prentice-Hall, 1975),- and "Digital Image Processing", Castlemann (Prentice-Hall, 1979) . Image analysis consists of digitizing an image, detecting a feature and then computing a measure of the feature. Several image analysis systems which are capable of performing these three functions are commercially available from Buehler, Ltd. (OMNIMET) ; Bausch and Lo b (OMINICON) Alpha, OMINICON PAS and OMINICON FAS-11) ; Cambridge Instruments, Inc. (QUANTIMET 720/23C, 720/25C and 800) and Leitz

(T.A.S.) All of these systems are based on video camera image scanning techniques. In order to be sure that the video signal accurately represents the image received, special characteristics are necessary in the cameras employed and such cameras are either specially designed or specially selected for accuracy of scanning. Several video tubes are available for image analysis, and the most common are known as the VIDICON, PLUMBICON, CHAHLNICON and SILICON VIDICON.

Down-Hole Investigation

As previously indicated, the optical examination input can also be derived from a probe inserted into the well bore itself either through a drill string or into a bore not having drilling equipment therein.

A tool which is particularly usable in the absence of drill string, as during tripping, is shown in Figs. 10 and 11, Fig. 10 showing the tool mounted on a section of drill string 160 having rather conventional calipers with arms 161 mounted to the string by conventional mounting devices 162 and 163 which can include tension springs with angle transducers. Normally, four arms 161 would be provided, three of the arms having idle rollers 164 and the fourth arm having an optical foot 165 which is shown, in greater detail in Fig. 11. A cable 166 extends through the interior of string 160, the cable including optical fibers and electrical wires, various ones of the wires being connected to the angle transducers and to a tool attitude package 168 for providing a continuous reading o;f the attitude of the tool as other readings are made. A portion of the cable 169 containing the optical fibers and at least two electrical conductors is connected to foot 165. As will be recognized, rollers 164 maintain contact with the walls of the bore hole 170, causing the outer surface of foot 165 to ride against one side of the bore hole wall. Although not illustrated in Fig. ^'10, it will be recognized that one or more of the rollers can be replaced by an optical foot so that simultaneous investigation of circularly spaced portions of the bore hole wall can be accomplished at the same time, permitting additional information to be derived about the dip of formations penetrated by the bore hole.

The optical foot itself, as shown in Fig. 11, includes a body 171 having a cavity 172 to receive the ends of the various components of the cable. The cable itself is provided with a termination having flanges 173 bolted or otherwise attached to a threaded gland 174 to maintain the cable in a sealing relationship with the foot. As seen in Fig. 11, the cable itself includes a tube or hose 17.6 which terminates in a nozzle 177 directed toward an opening 178 in the side of the foot adjacent the bore hole wall. . At the bottom portion of the foot, a portion of the opening is spaced away from the bore hole wall, leaving a gap 179 through which fluid can flow out of the foot cavity. The purpose of" the fluid is to provide an optically clear solution within the foot cavity, and adjacent to the bore hole wall, permitting optical examination thereof. To facilitate the cleaning action, an ultrasonic transducer 180 is disposed in cavity 172 with its transducer being oriented so that ultrasonic energy is transmitted toward the portion of the bore hole wall encompassed by opening 178.

OMPI A relatively low energy level of ultrasonic energy, such as that producible by a conventional piezoelectric device, tends to loosen material, such as mud cake, adjacent the bore, hole wall, which material is then flushed away by the fluid passing through conduit 176. Transducer 180 is energized by power supplied through electrical conductors 181.

At least two optical fibers 182 and 183 are included in the cable and terminate at connectors having objectives 184 and 185, respectively, disposed in cavity 172 facing the portion of the bore hole wall encompassed by opening 178. One of the fibers such as, for example, fiber 182, is a source fiber and provides illumination at a preselected wave length or band of wave lengths from a source at the earth's surface to illuminate, through the fluid supplied by conduit 176, the surface of the bore hole wall. Light reflected from that surface is received through objective 185 by fiber 183 and conducted to the surface. Although not illustrated in Fig. 11, the foot can be sufficiently large to accommodate a number of source and receiving fibers, providing a variety of images and providing the possibility for illumination at more than one wave length. The ultrasonic transducer, objectives and fluid conduit can be supported in a generally hemispheral shell 1867 for mechanical mounting of these components in fixed relationship with each other.

In use, the tool can be lowered, during tripping, to the bottom of the hole and then more slowly elevated to the surface, continually providing optical image data which is easily correlatable with depth information and attitude information supplied by package 168. The caliper structure maintains the optical foot in close proximity with the bore hole v/all while viewing is accomplished through the fluid supplied- It should also be recognized that the information derived from this structure can be in the form of an image viewable by an individual having a microscope coupled to the optical fibers at the surface so that a geologist at the surface can directly look at the exposed surface portions of subsurface formations. It will also be recognized that various enhancement techniques can be employed to improve the obtained image.

It is important to recognize that the apparatus shown in Figs. 10 and 11 can advantageously be employed in sequence with the mud analysis system described herein. Assume, for example, that a well is in the process of being drilled and the chips, sand, etc., brought to the surface by drill mud return is continually being analyzed and that, at some stage, the displays indicate the likelihood that an interesting, developable formation may have been penetrated by the drill bit. The apparatus shown in Figs. 10 and 11 can then be employed, during the next trip, to visually inspect the walls of the bore hole which was recently penetrated to either confirm or reverse the indication given by the mud return analysis techniques. This sequential use of the devices provides far more input than is ordinarily available, and provides the geologist with a much more reliable indication of a formation which may be a very thin stratum of a type which is commonly overlooked in the traditional techniques. It will also be recognized that an indication of the drill having entered a region known to normally accompany a developable formation may occur at a time when tripping of the string is not about to occur. In this case, it may be desirable to optically inspect the bottom of the bore hole without extracting the string and drill. An apparatus such as that shown in Figs. 12 and 13 can be employed in these circumstances.

A side elevation of one form of typical drilling bit is partially shown in Fig. 12, the bit being of the type having a body 190 and an externally threaded connector portion 191 which would normally be connected

OMPI to the lower end of the drill string, not shown. The body carries three conical bit cones 192, only one of which is shown in the figure. A mud conduit 193 is formed in the body to permit the flow of mud to the vicinity of the bit to remove cuttings therefrom and flush the bottom of the hole, the mud then flowing up the annulus around the drill string. As will be recognized by those skilled in the art, various configurations of bits are commonly employed, but many such bits contain mud conduits in different con igurations, and an apparatus can be provided to conform to the location of such conduits for optical investigation. Figs. 12 and 13 show a device 194 which can be used for this purpose with the bit shown, the device being suspended on a cable 195 which supports the device and also contains optical and electrical conductors for the investigation. When it is desired to use the device, the drilling operation is stopped and the device is lowered through the drill string, the lowering being _ assisted by mud pumping, causing the device to act as a piston passing through the drill string. Centering arms 199 maintain the device in a centered position, and lowering is stopped when a sensing plunger 196 encounters the inner lower surface of the bit.

It will be recognized that conduits 193 are equally spaced 120° apart so that they cooperate to flush the three bit cones provided. Device 194 is provided with a spring urged plunger 197 which extends outwardly and downwardly and is shaped to enter one of the conduits. Cable 195 is rotated to cause slow rotation of device 194 until plunger 197 enters one of the conduits. This positions the device so that a probe 198 protruding from device 194 points directly at another one of the conduits 193. The probe, connected to an optical fiber cable within the device, can then be extended, as by hydraulic pressure or an electrical device, causing the probe to extend into conduit 193 and to the outer surface of the bit until the outer portion of the probe is adjacent the bore hole wall. An optically clear fluid can then be pumped through the probe, clearing the portion of the bore hole wall adjacent the end of the probe, permitting optical inspection of the wall adjacent the bit. While the area of the borehole wall examined by the probe in this fashion is somewhat smaller than that usable with the device of Figs. 10 and 11, useful information can nevertheless be derived.

Fig. 13 shows a bottom plan view of the device, illustrating the angular relationships of the locating plunger 197 and probe 198. After use, the device can simply be extracted from the bit and string, and returned to the surface.

The devices of Figs. 10 and 11 or 12 and 13 can be used in place of the optical assemblies 121a-y shown in Fig. 9 to transmit light through the fibers of cable

163 and window 161 to the surface of a borehole 170 to be examined. A sequence of different wave lengths of light is supplied to selected ones of the fibers in the cable and reflected or luminescent light from the borehole wall is returned to the fibers and conducted up the hole to the multiplexing and processing equipment at the surface as shown in Fig. 9. The surface- of borehole 170 is normally smoothed to a considerable degree by the action of the drill which formed the hole, preparing the mineral surface for examination so that further grinding or the like is not necessary.

It has been recognized that optical fibers exhibit unique attenuation characteristics and that the transmission efficiency characteristics are a nonlinear function of wavelength. When the fibers are used only for information transmission, as by pulse or otherwise modulated light, the power levels are rather low and the losses, while significant and in some cases annoying, can be tolerated. However, by properly choosing fiber type and wavelengths, efficiencies of betv/een 40% and 90% or better can be obtained. This is particularly important when long runs of fibers such as in cable 163 are involved, and when low reflectance levels of light received through window 161 are to be transmitted directly to the surface. This also becomes critically important in conveying large power levels along long fiber cables.

Fig. 14 is a simplified graphical representation of the transmission characteristics of two types of fibers, the upper curve G being that of a Corning graded index glass fiber and the lower curve S being that of a step index fiber produced by Quartz Products Company. The vertical axis is percent transmission per kilometer and the horizontal axis is wavelength. As will be seen, the, graded index fiber transmission efficiency exceeds 40% toward the red end of the spectrum (yellow-orange region of visible light) and increases with increasing wavelength into the infrared and far infrared region, somewhat beyond the visible range. Light in the visible and infrared regions are particularly useful in optical analysis of minerals. Hence, fibers of either type can be used with appropriate selection of sources, the choice being made partly on the basis of cost and recognizing that, at the present time, graded index fibers are more expensive than step index. Figs. 15A-C, taken together, constitute a flow diagram of the information delivered to, used in, and provided by the geological data bases discussed above. As will be seen, the inputs, which are derived from the optical and digital analyses, involve identification and classification of chips and grains (sand, silt and clays) with identification of the spatial relationships of the mineral grains comprising the chips. Because rather large numbers of chips and grains are viewed by the optical portions of the system, the analysis and classification may be a statistical one rather than being a "single" chip or grain analysis, and this input therefore in terms of percentages of characteristics observed. In the composition analysis, mineralogical and chemical compositions from diffraction data and chromatographic analysis may be similarly statistical except for the identification of hydrocarbons present in either gases or liquids.

Fossil identification is also direct, although a statistical approach can be used and would be in certain types of formations. It should also be noted that fossil identification by pattern recognition is a useful approach to provide this information, using the apparatus of Figs. 4-8 or 10-13. Assemblages of fossils provide useful information. Finally, the depths from which the specimens were recovered, or are being observed, along with pressures and other drilling parameters are supplied.

These data inputs are supplied to the GDB core which, as previously indicated, takes the forms of an exploration GDB or a development GDB. While there is not an absolute line of demaraction between these types, and recognizing that an exploration GDB will evolve into a development GDB as information is accumulated and stored, the emphasis in exploration is on determining the environment of the deposit from or in which materials are examined, the age of each formation, the position in a basin and the possibility of hydrocarbon accumulation as evidenced by the input factors.

In a development of a basin about which much is already known and stored from data bases such as the ones previously mentioned, the emphasis is placed on lithostratigraphic correlation and biostratigraphic correlation with the known basin characteristics,, along with recognition and correlation of the presence and type of hydrocarbons present. Furthermore, the relative positions, attitudes, thicknesses and ages of specimens and strata encountered in a borehole being formed aid in the placement of that hole in the spatial context of the overall field and permit accurate prediction of the presence of formations of interest, as well as enhancing the information previously known.

It is thus possible to provide outputs, from the exploration GDB analysis, of various parameters for every depth increment including lithologic features, presence and types of hydrocarbons found, an estimate of the biostratigraphic age with good accuracy, and other formation features including the physical parameters such as formation velocity V_ . the position in the basin, the environment of the deposition and the potential for the existence of hydrocarbons.

These outputs are, and should be, regarded as estimated values in an exploration GDB but are in themselves highly useful. In addition, as these values are supplied to and correlated with known sections in the basin in a development GDB, it is possible to extract more specific information such as the geologic age of each formation, the formation name, the member name and the bed description including a refined prediction of the potential for hydrocarbon deposits, bed thickness and its relative position in the basin. Knowing these, one can arrive at specific stratigraphic correlations including the actual thickness of the overlying section, the predicted relation of the bed to the underlying section and a horizontal prediction of the ' formation characteristics.

It will be readily apparent that this information is excellent guidance for controlling the drilling operation and permits most efficient use of the drilling equipment and manpower available. Furthermore, continually updated information adds greatly to the safety of the drilling operation since evidence of approaching difficult or dangerous conditions, such as increasing downhole pressure, are brought to the drilling supervisor's attention promptly. Still further, the information stored in a development GDB permits the generation of any of a variety of "multi-dimensional" displays since the stored data includes spatial data for a large number of subsurface points. Such a display can be generated in a CRT or hard copy form using conventional contour graphic mapping routines such as those employed by Data Plotting Service, Don Mills, Ontario, Canada, which software is also available from IBM Corp. and Control Data Corp. as plotting packages. The displays have the obvious advantage of permitting visualization of a region under investigation.

While certain advantageous embodiments have been chosen to illustrate the invention it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

Claims (12)

What is claimed is:

1. A method of analyzing subsurface earth formations comprising the steps of

providing a stored data base including descriptive data on characteristics of geological and paleontological features commonly encountered in materials penetrated by a well borehole;

optically examining material indigenous to the subsurface region penetrated by the borehole and forming signals representative of selected characteristics of the material;

comparing the signals formed following the optical examination with data in the stored data base to identify the nature of geological and paleontological features present in the borehole; and

providing a display of those features identified.

2. A method according to claim 1 and further including the step of

collecting drill mud return emerging from a borehole during drilling thereof, and

separating from the drill mud return materials indigenous to and carried from the vicinity of the drill bit to the surface by the mud for the optical examination.

3. A method according to claim 2 wherein the step of separating further includes

MPI sorting the separated material in accordance with predetermined size categories into a plurality of groups of materials;

and wherein the step of optical examining includes

providing at least one optical examining station means for directing electromagnetic energy toward material supplied thereto and receiving electromagnetic energy emanating from the material,

substantially continuously conveying each of the groups of materials to one of the examining stations.

exposing materials in each of the groups, at a station, to incident electromagnetic energy having selected spectral characteristics, and

detecting electromagnetic energy emanating from the materials.

4. A method according to claim 3 and further including

washing the materials before the step of exposing them to electromagnetic energy.

5. A method according to claim 4 wherein the material comprises a plurality of p;articles, the method further including

abrading a surface of said particles before exposing the material in the incident electromagnetic energy.

6. A method according to claim 3 and including

providing a plurality of bundles of optical fibers, each bundle having an end at one of said stations with at

OMPI least some of the fibers directed toward the group of materials being conveyed thereto for receiving electromagnetic energy emanating from the materials in said group.

7. A method according to claim 3 and including, before the step of optical examining,

providing a sample carrier with a support surface;

distributing a portion of the materials to be examined over the support surface;

flowing a hardenable binder material onto the support surface and around the material distributed thereon; and

hardening the binder material to firmly hold the material on the support surface, thereby forming a plate of material to be examined.

8. A method according to claim 7 which includes, after the step of hardening,

abrading and polishing the upper surface of the plate of material to be examined before optical examination thereof.

9. A method according to claim 8 and including

providing a source of polarized light at the at least one optical examining station.

10. A method according to claim 1 v/herein the step of optically examining includes

providing an elongated bundle o.f optical fibers; extending the bundle into a well bore so that the distal end thereof closely approaches a wall of the bore adjacent the drill bit;

directing EMR having selected spectral characteristics from the surface through selected ones of the fibers in the bundle for illuminating material on a region of the bore wall, and

receiving and conducting EMR emanating from the illuminated material through selected ones of the fibers to the surface.

11. A system for separating and analyzing materials from mud return for use in combination with a well drilling apparatus of the type having a drill string and bit, means for supporting and rotating the string to drill a borehole, means for delivering drilling mud to the string, and means for conducting drill mud return emanating from the bore, annulus away from the borehole, the system comprising the combination of means for receiving and degassing at least a portion of the drill mud return and capturing gas emanating therefrom;

means for analyzing the captured gas and providing a plurality of signals representative of the presence of selected constituent^'s in said gas;

means for continuously extracting a preselected percentage of the degassed drill mud return;

a plurality of serially connected separation means for receiving said preselected percentage and sequentially removing therefrom chips, particles and grains of material in selected size categories; a plurality of optical scanning means for receiving, respectively, the removed material in each of said categories, for optically examining the material for EMR characteristics and for providing signals representative of selected ones of those characteristics; and

data processing means for receiving and storing said signals from said means for analyzing and from said scanning means, correlated with signals representative of drilling depth.

12. A system according to claim 11 wherein the optical scanning means includes

a plurality of light sources for providing light of at least two distinctly different wavelengths;

first fiber optic means for conducting the light to the removed material to illuminate the material;

second fiber optic means for receiving light emanating from the samples and forming an image thereof?

image processing means for selecting predetermined characteristics from the image; and

means for producing digital signals representative of the selected characteristics.