CA2064279A1 - Seismic data method and apparatus - Google Patents
Seismic data method and apparatusInfo
- Publication number
- CA2064279A1 CA2064279A1 CA 2064279 CA2064279A CA2064279A1 CA 2064279 A1 CA2064279 A1 CA 2064279A1 CA 2064279 CA2064279 CA 2064279 CA 2064279 A CA2064279 A CA 2064279A CA 2064279 A1 CA2064279 A1 CA 2064279A1
- Authority
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- Canada
- Prior art keywords
- sensing means
- vibration sensing
- earth
- drill bit
- drill string
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
TITLE: SEISMIC DATA METHOD AND APPARATUS
ABSTRACT OF THE DISCLOSURE
Method and apparatus are disclosed which incorporate a geophone at the lower end of a drill string immediate the drill bit for detecting seismic signals generated at the earth's surface for determining formation characteristics, structural conformation, well parameters, and the location of the drill bit relative to known surface locations. In an embodiment, the geophone device is provided within a mud motor housing carried on the drill string for reciprocation of the drill bit. In a preferred embodiment, a procedure incorporates the invention in a horizontal well application. Additional geophones may be provided on the surface for detecting reverberation of sonic waves generated at the earth's surface.
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ABSTRACT OF THE DISCLOSURE
Method and apparatus are disclosed which incorporate a geophone at the lower end of a drill string immediate the drill bit for detecting seismic signals generated at the earth's surface for determining formation characteristics, structural conformation, well parameters, and the location of the drill bit relative to known surface locations. In an embodiment, the geophone device is provided within a mud motor housing carried on the drill string for reciprocation of the drill bit. In a preferred embodiment, a procedure incorporates the invention in a horizontal well application. Additional geophones may be provided on the surface for detecting reverberation of sonic waves generated at the earth's surface.
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Description
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BACKGFCOuND OF THE INVENTION
2 (1) FIELD OF ~HE INVENTION: The invention relates to a 3 method and apparatus for the determination of the end of a drill 4 bit in a subterranean wellbore and/or for determininy selected characteristics of one or more formations in and below such 6 wellbore, incorporatin~ a qeophone in the drill string conduit, 7 whereby seismic waves generated at the surface of the earth may be 8 detected by the geophone for purposes of ascertaining the location 9 of the bit andtor for indicating formation andlor well parameters, structural conformation, and the like.
11 (2) ~RIEF DE~CRIP~ION OF THE PRIOR ART: It is now common 12 practice to perform seismic exploration of the earth by imparting 13 an acoustic wave to the earth at a first location and detecting the 14 return of the wave after reflection from subterranean rock formations at plura~ additional locations. The signals output by 16 the detectors, usually referred to as "geophones" when used in 17 earth-based exploration and as 'Ihydrophones'' in ocean-going 18 operations, can then be processed in known fashion to generate 19 representations of-the interfaces between rock layers of varying depth and density which then can be used by earth scientists in the 21 search for oil and gas.
22 Seismic exploration methods are well known to the prior 23 art. SeisDic expl~ration is normally utilized to obtain broad 24 general information about subsurface strata. These techniques are generally implemented by utilizing an explosive or vibratory sou~ce 26 which is disposed at multiple locations on the surfa~e of the earth s60s~ 623:03704.l000:03ns/s~:s~3am 2 :
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1 and plurality of geophone sensors which are laid out at regular 2 intervals near each source or "sho~ point".
3 Ordinarily, seismic data is collected by placing a shock 4 or impulse source on the surface of the earth, creating a shock wave which is propagated through the earth, reflected from the 6 underground horizons. Small signals are detected for recordation 7 from a geophone spread at the surface o~ the earth. Geophones are 8 extremely sensitive devices. They are built to receive extremely 9 small vibrations travelling long distances through the earth and provide electrical signals indicative of such vibrations.
11 A typical geophone spread includes any number of 12 geophones which are placed on the ground. The several geophones 13 are co~nected by a long cable to truck-located equipment ~hich 14 includes individual geophone amplifiers, data or signal conditioning circuits, and a recorder with a timing reference 16 placed on the recorded data. Where data is to be gathered relative 17 to off-shore locations, geophones in the form of "hydrophones" are 18 used and the related equip~nent LS ~oat-located.
19 Seismic exploration activities include use of geophones in which movement is measured ~y the curren~ induced in a coil that 21 moves in a magnetic field due to an inertia~ In this type of 22 geophone, the coil o~ wire is wrapped on a coil-form, which along 23 with the wire itself provides a mass having sufficient inertia to 24 cause relevant movement between the coil-mass and the permanent magnet of the geophone, when the geophone is moved by seismic 26 energy. Usually, in this type of geophone, the permanent magnet is 56094/ll:Q3:03704.1000:03/28/91:8:53~m 3 1 cylindrical in shape and is mounted in the housing for movement 2 with the housing. The coil-mass is annular and surrounds or 3 encircles the magnet with its longitudinal axes, along which it is 4 mounted to move, coinciding with the longitudinal axes of the S magnet.
6 In general, most commercially available geophones are 7 similar in that they con~ai~ a sin~le magnetized mass oscillating 8 in a coil in which there is generated a voltage in response to the 9 oscillation. The detector is coupled to the earth, or, in instances in which it has been arranged for detection of a signal 11 through a drilling conduit, introduced throuyh such conduit on a 12 wire or electric line, so that it oscillates in response to a 13 returned wa~e of seismic energy. The magnetic mass is typically 14 spring loaded and its oscillatory motion is damped by a dashpot or similar device. ~ny such system typically has a frequency response 16 which is nonlinear, and therefore the voltage generated in the 17 coil, which is recorded as the seismic signal, will bear a 18 similarly nonlinear relationship to the actual received seismic 19 signal as well.
In ~he past, geophones have also bee~ placed in a well 21 borehole near a spread o~ surface geophones. Sometimes, the 22 geophones have been placed in the well borehole simultaneously with 23 recording ~a~a ~rom surface located ~eophons. Sometimes, the data 24 can be collected on two or more different shots so that the data observed downhole is obtained prior to or after the collection of 26 data from the surface geophone spread.
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1 Well-logging techniques are also well known in the art 2 and are generally utilized to obtain additional information about 3 the strata through which the borehole is drilled. While highly 4 detailed information concerning porosity, permeability, structural conformation and other factors may be obtained by utilizing these 6 techniques, the information is generally limited to the vicinity of 7 the borehole.
8 The acoustic values in well logging may be measured by 9 means of an acoustic well-logging tool which may be of the type disclosed in French Patent No. 2,431,710. In such measurements, 11 the velocities and attenuations o~ the compressional waves and 12 shear waves ~hi~h are used are representative of the rock traversed 13 by the acoustic paths of the Stoneley waves. Pseudo-Rayleigh waves 14 also are used, which are representative both of the rock traversed and of the geometry of the wellbore. This measurement is made by 16 transmitting an acoustic wave through the fluid which fills the 17 vertical wellbore from one or a number of transmitting sources, and 18 by receiving at one or a number of receivers waves of various types ~9 produ¢ed by the transmitted wave. The waves arriving at the receiver or receivers are converted to electrical signals by the 21 receiver or receivers (of the piezoelectric type, ~or example~.
22 The electrical signals are transmitted to the surface by an 23 electric ca~le~ ~hen recorded, preferably, in diqital form in a 24 suitable recording instrument. The recorded signals are then processed by computer in order to identify the arrivals Z6 corresponding to each type of wave, especially compressional waves 560941~:Q3:0370~.1000:03/28/91:8:53~m - 5 ``:
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1 and shear waves and in order to determine the properties of 2 interests such as propagation velocities (or arrival times), or 3 amplitude. various processing operations may be performed in order 4 to improve the accuracy and quality of the measurements to be made.
A distinguishing property of all well-logging 6 measurements lies in the fact that they are performed within the 7 vertical wellbore and that they relate a small portion of the rocks 8 strata surrounding the vertical wellbore. This applies to all 9 well-logging systems, whether they are of the acoustic, electrical, nuclear or other types. In particular, in the case of acoustic 11 logs, this is d~e ~o the fact that the paths of the acoustic waves 12 are paths of the refracted type. In ~act~ the waves transmitted 13 through the vertical wellbore fluid are refracted at the wall of 14 the well~ore, follow the wall over a certain distance, are then again refracted and final~y arrive at the receiver or receivers of 16 the logging tools.
17 In the prior art, various means have been devised for 18 determining the position of a borehole using geophones in North-19 South, East-West co~rdinates, at selected depths, during a drilling operation. This has been done by using geophones specially 21 de~igned ~for introduction into the borehole, and sometimes 22 introduced through the drill pipe, which, by their internal 23 mechanism provide sig~ls ~dicating the slope, (or angle with 24 respect to vertical)~ of the borehole at each of a plurality of selected depths, and a measure, in relation to the magnetic 26 compass, of the azimuth of the slope of the borehole. Knowing the SM~ 613:03~0~.100003128/gl:8:53~ 6 , `'` ; '' . `: ' ' ., , . ~
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1 direction of the slope, and maynitude of slope, at each of a 2 plurality of selected known depths, and assuming that the borehole 3 is straight in between the points of reception of geophone signals 4 at which measurements are made, certain characteristics indicative the profile of the borehole can be determined.
6 A co~siderable volume of prior art exists in the field of 7 drill bit logging. In this art, a seism~c source is built into the 8 drilling apparatus near the bit, so that seismic signals can be 9 transmitted without substantial interruption of the drilling process. These seismic signals are then detected at the surface of ll the earth by a two-dimensional_array of ~eophones. ~easurements 12 are made of the arrival time of the seismic signals at geophones 13 located at the surface. From these measurements the travel time of 14 the seismic waves from the source to t~e geophones are determined.
Knowing ~he positions of the geophones with respect to the mouth of 16 the borehole, it is possible to calculate the position of the bit 17 in the earth in three dimensions, at any time. Typical of such 18 prior art bit logging techniques is that as disclosed in United 19 States Patent ~o~ 4!~03,017.
More recently, it has been discovered that a combination 21 of seismic exploration techni~ues with selective borehole 22 measurements may be utilized to obtain m~re detailed information 23 over a broader area of ~esti~a*ion. This technique is oft2n 24 referred to as ~rtical Seismic Profiling (VSP~ and involves a placement of geophone sensors in the borehole and the utilization 26 of more shot points on the surface near the borehole. This 56094/1~:623:0370~.1000:03128/91:8-.53am 7 ,,.,.,~ - ~ ' .
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1 technique can provide considerable additional information to help 2 delineate subsurface formations and reservoirs. However, the 3 information provided is frequently sparse and can be quite 4 expensive to obtain.
A single source VSP setup can often take 3-6 hours to rig 6 and more complex multi-offset-source setups can take several days.
7 Drilling rig operators do not generally wish to incur the costs 8 involved with these techniques for the amount of information 9 received. Additionally, the high costs associated with the surface sources and recording systems can add significantly to the costs 11 associated with this technique. It should therefore be obvious 12 that an improved technique must be discovered that provides similar 13 information without the h~gh costs involved with VSP.
14 One approach to solving the aforementioned problem is the so-called "Inverse VSP" technique, in which the geophones are 16 disposed on the surface of the earth and a seismic source is 17 utilized within the borehole. Among the problems associated with 18 this technique i5 the provision of a seismic source which is ;19 sufficiently repeatable and powerful for a useful acoustic wave ~2~0 field to be de~ected at the surface and sufficiently robust to Z1 permit easy recording of the resultant seismic waves and which does 22 not damage the borehole or the downhole equipment.
24 Downhole drilling motors have been used for many years in ~25 the drilling of oil and gas wells. Usually, the bearing shaft of 26 the motor, and the drill bit, will rotate with resp~ct to the ~60ss/ll:623:0370~.l000:03ns/sls~3a~ 8 . ~.
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1 housing of the drilling ~otor. The housing is connected to the 2 bottom of a conventional drill string, made up of drill collars, 3 and sections of drill pipe and, perhaps, other components well 4 known to those skilled in the art. At the surface, the drill string is connected to a kelly, which is bounded in the rotary 6 table of a drilling rig.
7 Drilling fluid, or "mud", is pumped through the drill 8 string to the bottom of the hole, and returns up the annulus 9 between the dx ll string and the wall of the borehole. The mud cools the drilling tools and removes the cuttings from the hole.
11 If a downhole drilling motor is hydraulic, the mud also supplies 12 the hydraulic power to operate the motor.
13 One type o~ hydraulic downhole motor is the progressive 14 cavity type, also known as the Moineau motor. This type of motor has a helical rotor within the cavity of a stator, and the stator 16 is connected to a housing. As mud is pumped through the stator, 17 the rotor is rotated. As the rotor rotates, it also gyrates, or 18 orbits, in the reverse direction relative to its rotation. A
19 universal joint or rod or other connection must be used to connect the gyrating rotor to the bearing shaft of the motor, kecause the 21 bearing shaft does not gyrate.
22 one type of connector has universal joints, which connect 23 the en~s of a straight rod to the rotor and to the bearing shaft.
24 The universal joints take only torsional load, so a ball and race assembly is used to take the thrust load. Rubber boots are clapped 5609J/11:623:0370`1.1000:03/28/91:8:53~ 9 ;
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2 ~ 2 ~ 9 1 over the univ~rsal joints to keep mud out of the ball and race 2 assembly.
3 Other downhole motors have long, flexible connecting 4 rods, which flex to compensate for the gyration of the rotor. Such connecting rods must be able to bear both thrust loads and torque 6 loads. The rods must also be flexible enough to allow the 7 eccentricity between the rotor and the bearing shaft, with a 8 reasonably small side load. A one-piece connecting rod, or a rod 9 assembly, that has a required ~lexibility, also has torsional flexi~ility and helps the rotor run smoothly when dynamic external 11 torques are encountered.
12 Mud motors may also be of the "turbodrill" variety, 13 wherein a bi~ is suspended o~ a lower end of a shaft which is, in 14 turn, supported within a case suspended ~rom the lower end of a drill string, and a turbine motor is arranged within an angular 16 space between the case and shaft to cause the shaft and bit to 17 rotate with respect to the case and string in response to the 18 circulation ~ dril~-ng Pluids downwardly through the drill string 19 and motor and out the bit into the annular space of the borehole.
Typical o~ such turbine motors for drilling is as described in U.S.
21 Patent No. 3,971,450.
22 It is an increasingly wide spread practice to drill 23 horizontal boreholes, especia~y in productive hydrocarbon deposits Z4 in order to drain the deposit to a distance which is considerably g~eater than its thickness, whereas a vertical borehole drains the 26 deposit only to a distance corresponding to its thickness. Within 56094/1~:623:03704.1000:031~8191:8:53am lO
' ~ ' , 1 the deposit zone, a horizontal borehole cuts through geological 2 strata at a small angle or even passes through the same stratum 3 over an appreciable distance of the order of several hundrPd 4 meters, the axis of said borehole being substantially parallel to S the limits of said geological stratum.
6 The horizontal borehole drilled from a vertical well is 7 usually drilled within a productive form~tion. Most production 8 formations have substantial horizontal portions and, when 9 conventional vertical wellbores are employed to tap such production formationsr a large number of vertical bores must ~e employed.
11 With the drilling of a wellbore_having a non-vertical or horizontal 12 portion traversing the production formation, a much greater area of 13 the production formation may be traversed by the wellbore and the 14 total drilling ca5t5 in the field may be substantially decreased.
Additionally, after a particular horizontal wellbore has produced 16 all of the economically available hydrocarbons, the same vertical 17 wellbore may be re-drilled to establish another horizontal portion 18 extending in another direction, and thus prolong the utility of the 19 vertical portion o~ the we~l a~d increase the productivity of the well to inClu~e the total production formation.
21 By use of the phrase "deviated well", "deviated 22 wellbore", and "horizontal section", it is meant to refer to wells 23 and wellbores which comprise a vertical entry section communicating 24 through ~ re~ati~ely short-radius curvature portion with a non-vertical or horizontal portion communicating with the producing 26 formation. In most instances, the producing formation extends for 5609~ 623:03704.1000:03/28/91:8:S3am 1 1 ,:
` ' ' -1 a substantial horizontal extent and the generally linear wellbore 2 portion traverses a substantial horizontal extent of the producing 3 formation, at least up to a distance of 1000 to 2000 feet, or more.
4 The radius portion of the wellbore has a curvature of at least 10 per 100 feet of length, and preferably a curvature in the range of 6 about 10 to about 30 per 100 feet of length.
7 A study of the strata located above the horizontal 8 borehole and therefore traversed by the vertical well bore is very 9 important i~ order to obtain information relating to lithologic properties (chemical and geometric compositions), sedimentologic 11 and fracturing properties of rocXs, ~luid content and petrophysical 12 parameters (porosi~y, per~eability, compressibility, and the like~, 13 as well as structural conformation.
14 Up to the present time, formation analysts have been unable to gain direct access to data relating to geological strata 16 located beneath the horizontal borehole. In order to permit access 17 to these data, it has been necessary to carry out a very 18 approximate study based on geological survey-map assumptions, 19 dynamic meas~remen~s (p~ess~e-flow relations) within the horizontal borehole or between boreholes (intexferences) and 21 seismic surface measurements. Unfortunately, surface measurements 22 have low selectivity and are uncertain, in the first place, by 23 reason of the presence of a modified zone at the ground surface 24 and, in the second place, by reason of the considerable distance which has to be traversed by the sonic waves between the surface 26 and a very deep geological strataO Apart from the large amount of 5609~ 623:0370J.1000:03/28191:8:53nm 12 - . , .
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1 energy to be produced in order to permit propagation of waves to 2 the deepest geological strata, it is to be noted in addition that 3 the accuracy of measurements is relatively low for the reason that 4 the frequency employed has to be fairly low. In practice, measurements are accurate to within approximation of a few tenths 6 of meters. Moreover, data relating to strata located beneath a 7 horizontal borehole are very difficult if not actually impossible 8 to obtain by reason of the ~ct that these strata are too remote 9 from the borehole for a traditional well-log.
On acoustical well logging, the sonic waves which arrive 11 at the receiver or receivers (the logging tool) are therefore 12 practically those which have followed a path along the wall of the 13 vertical wellbore. In consequence, the measurements concern only 14 a small lateral portion of material of the geological stratum located between the transmitter or transmitters and the receiver or 16 receivers of the well-logging tool.
17 By "lateral portion of material'l is meant the thickness 18 of material tTave~sed by the transmitted acoustic wave and 19 considered in a direction substantially perpendicular to the vertical axis of the wellbore. It is readily apparent that the 21 measurements made relate primarily to the thickness of the 22 geological stratum as considered vertically and therefore the 23 Yertical portion of str~ located between the transmitter or 24 transmitters and the receiver or receivers.
Although the transmitted acoustic waves propagate over 26 considerable distance throughout the medium which surrounds the 56094/11:623:03704.1000:03/28/91:8:53an~ 13 .
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, 1 vertical wellbore, it has in fact proved impossible to receive and 2 record reflected waves except in rare cases due to heterogeneities 3 such as faults, fractures or salt domes~ for example.
This invention relates to data gathering instruments and 6 methods. More specifically, the invention relates to improYements 7 including use of geophones to detect return of seismic signals 8 transmitted into the earth, for example, during seismic exploration 9 for oil, gas and other minerals, and for purposes of detecting the proximate location of a drill bit, particularly in a horizontal 11 drilling application.
12 The invention is directed to providing an apparatus and 13 method for determining while drilling in the earth with a drill bit 14 the position of a well tool i.e. a bit, using seismic wav~s reflecting geologic formations in the earth, in which differences 16 in travel time and other characteristics of seismic waves generated 17 at the surface of the earth are sensed at a position on the drill i8 conduit immediate the drill bit, and seismic wave signals are 19 subjected to signal processing techniques that will give a better characteristic of the geologic formations in and around the 21 borehole.
22 The present invention also provides an apparatus and 23 method ~hich all~w subsurface s~ruc~ures to be delineated, so that 24 gas pockets, ~aults, fractures, stratigraphic layers andtor other subsurface characteristics can be detected and mapped, reflection 26 coefficients can be measured, drill bit location can be determined, ~609411~:623:0370~.1000:03128191.8:53a~n 14 '~ ' ," '~ ' ' ' ' ~
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1 hardness of the rock being drilled can be determined, condition of 2 the drill bit can be ascertained and structural conformation can be 3 evaluated.
4 In the present invention, geophone signals are processed S so that seismic wave generation sources at the surface of the earth 6 can be detected and imaged through sensing located at the drill 7 bit. Differences in travel time and other characteristics of the 8 seismic radiation will be sensed, and this will be the means by 9 which reflections from multiple causes can be distinguished and imaged.
11 The apparatus in accordance with the invention includes 12 a plurality of seismic w~Ye generators such as vibrators, 13 "thumpers" or explosives, or the l~ke, which are positioned at the 14 surface of the earth a~ a plurality of known positions with respect to a borehole. The seismic waves are received by geophones 16 immediate the drill bit, as such waves are being reflected by the 17 geologic formations between the surface signal generators and the 18 geophones immediate the bit, as well as $~rmations below the bit.
19 In the present invention, a seismic wave receiver is provided as part of ~he drilling equipment, at or near the bit, 21 and, preferably, immediate a Moineau or turbine mud motor and 22 provides one or more of a plurality of seismic wave sensors, ~23 detectors or ~eop~ones co~ec$ed thro~gh an electrical conduit 24 extending to the top of the well and which is amplified by a conventional amplifier extending to a seismic recording system. By 26 such capturing of measurements of amplitude, energy, character, 56094/ll:U3:03704.1000:03/28/91:8-53~n 15 , ~ ' .
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2 7 g 1 etc. of the received signals through the geophone in detection of 2 seismic shock waves initiated at the surface of the well from each 3 of one or a plurality of selected positions, a determination can be 4 made as to whether there is a gas-filled porous rock formation, or other hydrocarbon-containing formation, which is reflecting energy 6 from the seismic source at the top of the well to the geophone in 7 the drill string~ The presence of such a geologic formation would 8 be indicated by variation in amplitude or energy of the received 9 signals when the reflected seismic wave creates an interference pattern with a direct wave from a seismic source at the surface and 11 the geophones are in the resulting interference pattern at the 12 location of the drill string.
13 In the case of horizontal applications, conventional 14 recording reflections of reverberated sound waves at the surface of the earth may not allow a comparatively accurate depiction of 16 strata. By placing the geophone in proximity to the drill bit, a 17 more accurate depiction of such strata above and below can be 18 obtained because the reflection o~ the reverberated sound waves are 19 direct to the geophone in the well, itself.
Additionally, if the geophone is coupled with real time 21 processing of impulses fro~ the geophone, the exact location of the 22 drilling tool in proximity to the ~arget formation can be 23 ascertained~ The drilling t~ol can then be adjusted to alter its 24 course to follow the target formation.
2~ In particular, the present invention is directed to a 26 method and apparatus for obtaining seismic data pertaining to an s60s~lH:623:037~.l000:03ns/sl:ss3~ 16 ~ ~ 2 ~ 9 1 earth formation while forming a wellbore in the formation with a 2 drill string having a drill bit disposed at the distal end ther~of 3 The method includes providing vibration sensing means carried by 4 the drill string and immediate the drill bit. The vibration sensing ~eans are adapted to produce electrical signals related to 6 the seismic Yibrations generated at the earth's surface. Such 7 sensing means may also be placed in a "string" at the surface of 8 the earth to detect seismic wave reflections from formations and/or 9 drilling tools in the wellbore. Acoustic vibration generation means are also provided upon the earth's surface for activating and 11 transmitting ac~us-tic shock waves for detection by the vibration 12 sensing means. The first seismic wave signals generated by the 13 acoustic vibration generating means are captured such a~ by 14 amplifications, recordation, radio frequency or telephone cable transmissiQn, and ~e ~e, as well as the second signals which are 16 generated by the vibration sensing means or geophones. The second 17 signals are transmitted to the earth's surface, such as through the 18 drill string by means of a conduit inserted therein, or the like, 19 and wellbore and format~on parameters ~s well as the location of ZO the drill ~it, re~ative to a formation, are determined through 21 analyses~of the second signals, which may, or may not, be compared 22 with the first signals.
23 When th~ invention is inc~porated in conjunction with 24 the use of a drilling mud motor, such apparatus may include means for securing the motor between the drill string and the drill bit.
26 ~ stator of the progressive cavity type is preferably provided 5609~ 623:0370~.1000:03/28191:8:S3alu 17 ........ .
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1 which will includ~ operation with a rotor within the stator such 2 that the rotor rotates and gyrates in response to fluid flow of mud 3 through the stator. A housing is connected to the stator and a 4 bearing shaft is concentrically located within the housing and is rotatable about the longitudinal axis of the bearing 5haft and the 6 housinq. Bearing means are also provided between the housing and 7 the bearing shaft. Drive means extend between the rotor and the 8 bearing shaft for translating the rotation and gyration of the 9 rotor to the true rotation of the bearing sha~t. M~ans are provided for connecting the driv~ means to the rotor and for 11 connecting the draft means to the bearing shaft, respectively.
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12 Vibration sensin~ ~eans are placed within the housing of the mud 13 motor and are adapted to produce the electrical signals relating to 14 the seismic vibration generated at the earth's surface and through at least a portion of the formation.
16 BRIEF DE~CRI2TION OF ~HE DRAWINGS
17 FIG. la is a schematic illustration depicting the apparatus 18 incorpora~ed in drilling through a lateral portion of material in 19 a horizontal wellbore, with surface seismic equipmant, as illustrated.
21 FIG. lb is an enlarged schematic illustration similar to Fig.
22 la, showing the wellbore tools.
~23 FIGs. 2a, 2b, and 2c each are longitudinal sectional drawings 24 of a mud motor ~or incorporation in the present invention.
FIG. 3 is an enlarged view of the upper portion of the device 26 shown in FIG. 2a.
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1FIG. 4 is an enlarged sectional view of the geophone device 2shown in FIG. 3.
3FIG. 5 is a perspective view of the geophone in the housing 4for the mud motor guidance system.
5Di:~CRIPTION OF ~HE ~REFERREI) E~BODINEN~8 6Now with respect to FIGs. lA and 1~, there is shown at the top 7surface 1 of the wellbore 2 a rotary drilling rig 3 and a rotary 8table 4 through which is disposed a drilling conduit 5 ~ade up of 9sections of drill pipe 6, normally provided in 30 to 60 foot 10lengths. The drill pipe conduit 5 is introduced into the wellbore Il2 and is shown passing through a comparatively short vertical I2section 7 and into a horizontal section 8 below a lateral portion 13of material or production formation 9. At the lowermost end of the 14drill string conduit 5 is provided a bit 10 which is attached to a 15housing or pup joint 11 extending to a stabilizer 12 which, in 16turn, has its upper most end 13 secured at a bearing section 14 to 17a mud motor 323 having a housing 325.
18~At the upper most end 311 (FIG. 2A) of the mud motor housing l9325 is secured an adjustable bent sub 15, which assists in 20orienting the mud motor for traversing that portion o~ the wellbore 21extending between the completely vertisal ko the full or partially 22ho~izontal section of the wellbore. A second stabilizer 16 is 23provided at the upper most end 15a of the bent sub housing which, 24in turn, is secured to the lowermost end of the drill string 5.
25As shown in FIG. lAj there is illustrated a conventional 26seismic exploration operation at the surface 1 of the wellbore 2.
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1 A source of acoustic energy is shown at 17. Commonly, this may be 2 dynamite or a truck 18 having a base plate 19 mounted on a jack 20, 3 so that the entire truck may be lifted of f the ground, upon the 4 base plate 19. Vibration is then imparted to the entire truck 18.
The acoustic wave 21 is shown generated by the dynamite 17 and 6 passes înto the surf~ce of the earth and varying rock layers 9 7 along wave paths indicated general~y at 21.
8 The waves may be reflected from a subsur~ace layer, such 9 as 9 to a geophone 23 in the wellbore 2, as described below. The wave may also be reflected from the subsurface layer 9 backupwardly 11 50 to be dete ted by geophones 23, at the suxface of the wellbore.
12 ~ypically, such surface geophvnes 23 will simply ~omprise a body 13 having a spike portion for firm insert~oD into the surface of the 14 earth.
The geophones 23 used at the surface of the earth may, or 16 may not, be the same as the geophone 23 contemplated for use within 17 the well and in association with the drill string S immediate the 18 drill ~it 10.
19 ~any types of sensing arrays or geophones 23 can be used at the top surface 1 oP t~e wellbore to detect seismic waves 21 generated éither at the top of the wellbore (waves 21) or reflected 22 within the wellbore itself, (waves 50) such as arrays extending 23 radially outward from a ~oint near t~e mouth o~ the wellbore 2.
24 Alternatively, the sensing arrays can ~e in a circle, the center of which i5 at the mouth of the wellbore 2. The sensing array might 26 be spaced, in a selected manner, in one or more concentric circles.
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1 The sensing arrays can be irregular in geometry. A single geophone 2 2.3 can be moved from point to point to form the sensing array or a 3 plurality of geophones or sensors may be used to form a sensing 4 array.
Now referring to FIG. 4, within the body portion or 6 housing 35 of the geophone 23 is mounted a magnetic mass 25 within 7 a coil 39 for oscillation purposes, so that when the geophone 23 8 oscillates in response to receipt of the acoustic wave 21 through 9 the formation 9, the magnetic ~ass 25 oscillates with respect to the coil 39, so tha~ the coil 39 outputs an electric signal through ll lines 26a, 26b which is provided to the interior of the drill 12 ~tring 5 to the top l of the wellbore 2.
13 The geophonP 23 also has upper and lower spring members 14 28, 29 between ~ch ars placed magnet caps, 30, 31. A header 32 is positioned at the top of the geophone 23 through which are 16 received electric terminals 26a, 26b extending to the conduit 26 17 disposed within the drill string conduit 5 and extendable to the 18 top surface 1 of the wellbore 2. A coil terminal 33 and a pigtail 19 (not s~own) extend to respective terminals 26a, 26b. A bottom support 34 holds in place the housing 35 having its upper end 21 received around the lower portion of the header 32.
~22 The geophone 23 used in such seismic exploration 23 ~ activities typi~ally is placed in a hermetically sealed housing.
24 This protects the geophone 23 from invasion of drilling fluid, when the geophones are to be placed in the wellbore 2. The housing 26 provides a North seekin~ reference element. The North-seeking 56094ill:623:n370~.1000:03/28/91:8:53am . 2 1 ~, ' ' .
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ri g 1 reference may ~e constructed with and made of a North-seeking 2 gyroscope and cooperative accelerometer system~ Thus, the 3 equipment may "tumble" as it moves to any relative orientation in 4 the well. Even though it may take any angular position in space, it is not blind to its orientation. That is, it is able to locate 6 its orientation relative to a particular reference system (North on 7 the earth in this instance) and is therefore able to provide an 8 azimuthal reference relative to a seismic wave generation signal at 9 the surface of the well.
With reference to FIGS. 2A and 2B, typically, the mud ll motor 323 of the present invention will include a guidance system 12 (not shown), which may be in the ho~sing 311, which responses to 13 signals received through the electric conduit 26 to the top of the 14 well. Such guidance system enables the m~d motor 323 to alter its course through the uel~re as ~he wellbore moves from vertical to 16 horizontal relative to the formation 9. Alternatively, such 17 downhole guidance system may be contained in a tubular housing or 18 joint in proximity to the uppermost end of the mud motor 323.
19 Accordingly, it is contemp~ated in this invention that the geophone ~3 may be placed ~'~her in the mud motor housing itself, such as 21 housing 311, or, alternatively, within a housing immediately above 22 or adjacent to the mud motor 323, such as in the housing for the 23 downhole guidance system components. Such location for the 24 yeophone 23 will ~e sufficiently immediate the drill bit to make a satisfactory determination of the proximate location of the drill 26 bit relative to a fixed location.
56094/11:~23:0370~t.1000:03128/91:8~S3~D 2 2 ~ . .
l The signal can then be amplified and recorded by mobile 2 e~uipment carried within a second truck 27, and may be processed in 3 conventional way. The signal generated by the downhole geophone 23 4 may also be compared to a signal generated by one or more geophones 23 at the surface 1 of the wellbore 2, which signals extend through 6 line 23a to a conventional amplifier recorder in such mobile 7 equipment 27, and compared with the signal sent by the downhole 8 geophone 23 through the conduit 26 to the top 1 of the wellbore for 9 detecting the location of the drill bit 10 and for determining other well parameters.
11 Referring now to FIGs. 2a, 2b and 2c, a bypass valve 12 housing 311 is connected to the lower end of the drill string 5.
13 The drill string 5 consists of drill collars tnot shown) and 14 sections of drill p~pe ~, and extends upward to the drilling rig 3 at the top sur~ace 1. Drilling fluid, or "mud," is pumped through 16 the bore 315 of the drill string 5 into the bore 317 of the bypass 17 valve housing 311.
18 The mud forces a shuttle 319 downward to close off some 19 bypass ports 321. When the bypass ports 321 are open, mud can escape from the bore 315 of the drill string 313 while the drill 21 string 313 is being removed from the hole. Mud can enter the bore 22 315 of the drill string 5, through the bypass ports 321, when the 23 drill string 5 is put into the wel~k~re 2. When the bypass ports 24 321 are closed by the shuttle 319, the mud is directed downward into a downhole drilling motor 323.
S609~ 623:0370~.1000:031~8/91:8:53am 23 ~.
1 The housing of the downhole drilling motor 323 has three 2 parts; an upper housing 325, a connecting rod housing 327, and a 3 bearing housing 329. The cylindrical upper housing 325 is 4 connected to the lower end of the bypass valve 311, and houses a progressive cavity motor. The progressive cavity motor has a 6 flexihle stator 331, which is connected to the inner surface of the 7 upper housing 325. A helical rotor 333 is mounted within the 8 stator 331. As mud flows downward through the cavities 335 between 9 the stator 331 and the rotor 333, fluid pressure causes the rotor 333 to rotate.
11 As the rotor 333 rotates, it also gyrates, or orbits in 12 the reverse directi~n. As shown in FIG. 26, a connecting rod 13 assembly 337 c~nnsc~s the lowe~ end 339 of the rotor 333 to a 14 rotating shaft cap 341, which is firmly secured to a rotating bearing shaft 343. The connecting rod asse~bly 337 must be 16 flexlble enough to translate the gyrating motion of the rotor 333 17 to the true rotation of the bearing shaft 343.
18 The connecting rod housing 327 is connected to the lower 19 end of the upper housing 32~, and encloses the connecting rod assembly 3;37. -The bearing housing 339 is connected to the lower 21 end of the connecting rod housing 327, and completes the housing of 22 the drilling motor 323. The bearing shaft 343 is mounted 23 concentri~al~y within the ~earing housing 329.
24 The lower end of the drilling motor 323 is shown in FIG.
2c. Various radial bearings 345 and thrust bearings 347 transmit 26 loads between the rotating bearing shaft 343 and the bearing s60s~ 6z3:037~.l~:03ns/sl:s~3~ 24 -.
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1 housing 329. A rock bit 349, which is threaded onto the bearing 2 shaft 343, digs the borehole as it rotates. In order to drive the 3 rock bit 349 properly, the bearing shaft 343 must rotate with a 4 true rotation about the longitudinal axis 351 of the bearing shaft 343 an~ ~he housing 329.
6 During operati~n, ~ circulates through the drilling 7 motor 323 to rotate the rotor 333. As the rotor 333 rotates the 8 lower end 339 of the rotor 333 also gyrates. The connecting rod 9 assembly 337 must translate the rotation and gyration of the rotor 333 to the ~rue rotation of the bearing shaft 343. The flexible 11 rod 353 bends and flexes to co~pensate for the eccentricity between 12 the rotor 333 and the ~earing ~haft 343.
13 Now, with re~erence to FIG. 5, th~ housing 3~1 of the mud 14 motor 323 contain~ ~be ~Pop~o~e Z3 centrally axially oriented therein and secured in place of internally of a donut 41. The 16 donut 41 has a series of radially spaced splines 37 securing the 17 housing 35 to the mud motor housing 311. Mud flow passages 38 are 18 defined between each of the splines 37. Accordingly, the l9 positioning of the geophone within the housing 311 will not adversely inter~ere with efficient mud flow through the housing 311 :21 and to the-valve member 319, for proper activation of the m~d motor :22 323.
23 The cond~t 26 extends ~el~w the geophone 23 by means of 24 a conduit member 26a to a central electronic control assembly generally depicted at 39 to generally indicate positioning of the 26 guidance controls for the mud motor 323.
5609~ 623:0370$.1000:03/28/91:~:53am 25 ~, :
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, l The conduit elements 26a, 26b extending from the top 32 2 of the geophone 23 are secured within a wet connection 40 on the 3 conduit 26, joining conduit elements 26a therein. The conduits 4 26a, 26b of the geophone 23, together with conduits forming a part of the downhole mud motor guidance system extending from the 6 control 5~ throuqh the conduit elements 26c, all extend within the 7 interior the drill string 5 to the top of the wellbore l, with the 8 conduits for the geophone 23 extending to the conventional 9 amplifier (not shown), recorder ~not shown), radio or telephone transmitter (not shown) in the control vehicle 27.
12 As state~ a~o~e, the present invention is directed to a 13 method and apparatus for utilizing seismic wave signals during the 14 actual formation of the wellbore to determine formation characteristics, wellbore integrity, proximate location of a 16 particular downhole tool, such as a drill bit, or the like, as well 17 as structural confor~ation data. Accordingly, a drill string 5 is 18 made up at the ~op s~r~ace ~ ~y securing sections of drill pipe 6 19 to the lower end of which is secured an upper centralizer 16, which ZO is joined at its lowermost end by a bent sub 15 which, in turn, is 21 secured at its lowermost end to a mud motor 323 which activates a 22 drill blt 10 when a rotorlstator assembly in the mud motor 323 is 23 hydraulic~l~y activated by drilling fluid. The assembly is 24 introduced into the wellbore 2 and extends through a generally 2~ vertical section 7 immediate a formation 9 ~or ultimate directional .
~609~ 623:0370~.1000:03/28/91:8:53a~n 26 ,.. .,,~ :., : , 7 rj 9 1 drilling into a lateral portion of material or horizontal sectiOn 2 8 (FIG. la).
3 As the borehole 2 is extended, additional section 6 of 4 the drill string 5 will have to be inserted through the rotary table 4 on the rig 3. Accordingly, typically, reciprocation of the 6 bit lO is temporarily aborted by terminating circulation of mud 7 down the drill string ~ and to the mud motor 323. During such 8 time, the acoustic vibration generation means are activated at the 9 surface 1 of the wellbore 2, such as by excitement of the vibrator 19 on the truck 18, or by explosion, indicated at 17, of dynamite, 11 or other material, sending a_patterned series of seismic shock 12 waves 21. Such shock waves wi~l reverberate as a result of the 13 presence of the formation 9 and will be reflected in echo signals 14 50 redirected to the top sur$ace 1 in the vicinity of the wellbore 2. Su~h s~ic ~aves 21 wi~l also be detected by the downhole 16 geophone 23, as the vibration sensing means. Accordingly, electric 17 signals will be produced by the downhole geophone 23 and will ~e 18 sent to the top of the well through the conduit 26 within the 19 interior of the ~rill s~ring 5. The seismic wav~ signals 21 generated by the explosi~n 17 (or the vibrator 19) are captured, 21 such as by recording~ radio/telephone transmission, electronic 22 storage, and the like through appropriate conventional mechanisms 23 in the control truck 27. Additionally, the signals generated by 24 the downhole geophone 23 at the m~d motor 323 are likewise captured. By comparing the seismic wave signals 21 with the 26 signals generated by the downhole geophone 23, in numerous manners 5609~ 623:037W.1~00:03/2819t:8:53a~ 27 `
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1 and alternatives )cnown to those skilled in the art, the proximate 2 three-dimensional location of the drill bit 10, together with other 3 parameters, as described above, relative to the explosion 17 can be 4 determined, and the direction of the mud motor 323 and drilling conduit or string 5 may be altered, accordingly, or confirmed, if 6 no alteration of direction is required.
7 When surface geophones 23 are provided, such geophones 23 8 will detect seismic echoes generated by the initial seismic wave 21 9 reflections 50 through one or more formations, such as formation 9, back to the surface 1, and additional conventional formation and 11 other data can be obtained, in conventional fashion.
12 Althou~h the invention has been described in terms of 13 specified embodiments which are set forth in detail, it should be ~4 understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments 16 and operating techniques will become apparent to those skilled in 17 the are in view of the disclosure. Accordingly, modification are 18 contemplated which can be made without departing from the spirit of l9 the descri~ed invention.
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BACKGFCOuND OF THE INVENTION
2 (1) FIELD OF ~HE INVENTION: The invention relates to a 3 method and apparatus for the determination of the end of a drill 4 bit in a subterranean wellbore and/or for determininy selected characteristics of one or more formations in and below such 6 wellbore, incorporatin~ a qeophone in the drill string conduit, 7 whereby seismic waves generated at the surface of the earth may be 8 detected by the geophone for purposes of ascertaining the location 9 of the bit andtor for indicating formation andlor well parameters, structural conformation, and the like.
11 (2) ~RIEF DE~CRIP~ION OF THE PRIOR ART: It is now common 12 practice to perform seismic exploration of the earth by imparting 13 an acoustic wave to the earth at a first location and detecting the 14 return of the wave after reflection from subterranean rock formations at plura~ additional locations. The signals output by 16 the detectors, usually referred to as "geophones" when used in 17 earth-based exploration and as 'Ihydrophones'' in ocean-going 18 operations, can then be processed in known fashion to generate 19 representations of-the interfaces between rock layers of varying depth and density which then can be used by earth scientists in the 21 search for oil and gas.
22 Seismic exploration methods are well known to the prior 23 art. SeisDic expl~ration is normally utilized to obtain broad 24 general information about subsurface strata. These techniques are generally implemented by utilizing an explosive or vibratory sou~ce 26 which is disposed at multiple locations on the surfa~e of the earth s60s~ 623:03704.l000:03ns/s~:s~3am 2 :
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1 and plurality of geophone sensors which are laid out at regular 2 intervals near each source or "sho~ point".
3 Ordinarily, seismic data is collected by placing a shock 4 or impulse source on the surface of the earth, creating a shock wave which is propagated through the earth, reflected from the 6 underground horizons. Small signals are detected for recordation 7 from a geophone spread at the surface o~ the earth. Geophones are 8 extremely sensitive devices. They are built to receive extremely 9 small vibrations travelling long distances through the earth and provide electrical signals indicative of such vibrations.
11 A typical geophone spread includes any number of 12 geophones which are placed on the ground. The several geophones 13 are co~nected by a long cable to truck-located equipment ~hich 14 includes individual geophone amplifiers, data or signal conditioning circuits, and a recorder with a timing reference 16 placed on the recorded data. Where data is to be gathered relative 17 to off-shore locations, geophones in the form of "hydrophones" are 18 used and the related equip~nent LS ~oat-located.
19 Seismic exploration activities include use of geophones in which movement is measured ~y the curren~ induced in a coil that 21 moves in a magnetic field due to an inertia~ In this type of 22 geophone, the coil o~ wire is wrapped on a coil-form, which along 23 with the wire itself provides a mass having sufficient inertia to 24 cause relevant movement between the coil-mass and the permanent magnet of the geophone, when the geophone is moved by seismic 26 energy. Usually, in this type of geophone, the permanent magnet is 56094/ll:Q3:03704.1000:03/28/91:8:53~m 3 1 cylindrical in shape and is mounted in the housing for movement 2 with the housing. The coil-mass is annular and surrounds or 3 encircles the magnet with its longitudinal axes, along which it is 4 mounted to move, coinciding with the longitudinal axes of the S magnet.
6 In general, most commercially available geophones are 7 similar in that they con~ai~ a sin~le magnetized mass oscillating 8 in a coil in which there is generated a voltage in response to the 9 oscillation. The detector is coupled to the earth, or, in instances in which it has been arranged for detection of a signal 11 through a drilling conduit, introduced throuyh such conduit on a 12 wire or electric line, so that it oscillates in response to a 13 returned wa~e of seismic energy. The magnetic mass is typically 14 spring loaded and its oscillatory motion is damped by a dashpot or similar device. ~ny such system typically has a frequency response 16 which is nonlinear, and therefore the voltage generated in the 17 coil, which is recorded as the seismic signal, will bear a 18 similarly nonlinear relationship to the actual received seismic 19 signal as well.
In ~he past, geophones have also bee~ placed in a well 21 borehole near a spread o~ surface geophones. Sometimes, the 22 geophones have been placed in the well borehole simultaneously with 23 recording ~a~a ~rom surface located ~eophons. Sometimes, the data 24 can be collected on two or more different shots so that the data observed downhole is obtained prior to or after the collection of 26 data from the surface geophone spread.
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1 Well-logging techniques are also well known in the art 2 and are generally utilized to obtain additional information about 3 the strata through which the borehole is drilled. While highly 4 detailed information concerning porosity, permeability, structural conformation and other factors may be obtained by utilizing these 6 techniques, the information is generally limited to the vicinity of 7 the borehole.
8 The acoustic values in well logging may be measured by 9 means of an acoustic well-logging tool which may be of the type disclosed in French Patent No. 2,431,710. In such measurements, 11 the velocities and attenuations o~ the compressional waves and 12 shear waves ~hi~h are used are representative of the rock traversed 13 by the acoustic paths of the Stoneley waves. Pseudo-Rayleigh waves 14 also are used, which are representative both of the rock traversed and of the geometry of the wellbore. This measurement is made by 16 transmitting an acoustic wave through the fluid which fills the 17 vertical wellbore from one or a number of transmitting sources, and 18 by receiving at one or a number of receivers waves of various types ~9 produ¢ed by the transmitted wave. The waves arriving at the receiver or receivers are converted to electrical signals by the 21 receiver or receivers (of the piezoelectric type, ~or example~.
22 The electrical signals are transmitted to the surface by an 23 electric ca~le~ ~hen recorded, preferably, in diqital form in a 24 suitable recording instrument. The recorded signals are then processed by computer in order to identify the arrivals Z6 corresponding to each type of wave, especially compressional waves 560941~:Q3:0370~.1000:03/28/91:8:53~m - 5 ``:
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1 and shear waves and in order to determine the properties of 2 interests such as propagation velocities (or arrival times), or 3 amplitude. various processing operations may be performed in order 4 to improve the accuracy and quality of the measurements to be made.
A distinguishing property of all well-logging 6 measurements lies in the fact that they are performed within the 7 vertical wellbore and that they relate a small portion of the rocks 8 strata surrounding the vertical wellbore. This applies to all 9 well-logging systems, whether they are of the acoustic, electrical, nuclear or other types. In particular, in the case of acoustic 11 logs, this is d~e ~o the fact that the paths of the acoustic waves 12 are paths of the refracted type. In ~act~ the waves transmitted 13 through the vertical wellbore fluid are refracted at the wall of 14 the well~ore, follow the wall over a certain distance, are then again refracted and final~y arrive at the receiver or receivers of 16 the logging tools.
17 In the prior art, various means have been devised for 18 determining the position of a borehole using geophones in North-19 South, East-West co~rdinates, at selected depths, during a drilling operation. This has been done by using geophones specially 21 de~igned ~for introduction into the borehole, and sometimes 22 introduced through the drill pipe, which, by their internal 23 mechanism provide sig~ls ~dicating the slope, (or angle with 24 respect to vertical)~ of the borehole at each of a plurality of selected depths, and a measure, in relation to the magnetic 26 compass, of the azimuth of the slope of the borehole. Knowing the SM~ 613:03~0~.100003128/gl:8:53~ 6 , `'` ; '' . `: ' ' ., , . ~
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1 direction of the slope, and maynitude of slope, at each of a 2 plurality of selected known depths, and assuming that the borehole 3 is straight in between the points of reception of geophone signals 4 at which measurements are made, certain characteristics indicative the profile of the borehole can be determined.
6 A co~siderable volume of prior art exists in the field of 7 drill bit logging. In this art, a seism~c source is built into the 8 drilling apparatus near the bit, so that seismic signals can be 9 transmitted without substantial interruption of the drilling process. These seismic signals are then detected at the surface of ll the earth by a two-dimensional_array of ~eophones. ~easurements 12 are made of the arrival time of the seismic signals at geophones 13 located at the surface. From these measurements the travel time of 14 the seismic waves from the source to t~e geophones are determined.
Knowing ~he positions of the geophones with respect to the mouth of 16 the borehole, it is possible to calculate the position of the bit 17 in the earth in three dimensions, at any time. Typical of such 18 prior art bit logging techniques is that as disclosed in United 19 States Patent ~o~ 4!~03,017.
More recently, it has been discovered that a combination 21 of seismic exploration techni~ues with selective borehole 22 measurements may be utilized to obtain m~re detailed information 23 over a broader area of ~esti~a*ion. This technique is oft2n 24 referred to as ~rtical Seismic Profiling (VSP~ and involves a placement of geophone sensors in the borehole and the utilization 26 of more shot points on the surface near the borehole. This 56094/1~:623:0370~.1000:03128/91:8-.53am 7 ,,.,.,~ - ~ ' .
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1 technique can provide considerable additional information to help 2 delineate subsurface formations and reservoirs. However, the 3 information provided is frequently sparse and can be quite 4 expensive to obtain.
A single source VSP setup can often take 3-6 hours to rig 6 and more complex multi-offset-source setups can take several days.
7 Drilling rig operators do not generally wish to incur the costs 8 involved with these techniques for the amount of information 9 received. Additionally, the high costs associated with the surface sources and recording systems can add significantly to the costs 11 associated with this technique. It should therefore be obvious 12 that an improved technique must be discovered that provides similar 13 information without the h~gh costs involved with VSP.
14 One approach to solving the aforementioned problem is the so-called "Inverse VSP" technique, in which the geophones are 16 disposed on the surface of the earth and a seismic source is 17 utilized within the borehole. Among the problems associated with 18 this technique i5 the provision of a seismic source which is ;19 sufficiently repeatable and powerful for a useful acoustic wave ~2~0 field to be de~ected at the surface and sufficiently robust to Z1 permit easy recording of the resultant seismic waves and which does 22 not damage the borehole or the downhole equipment.
24 Downhole drilling motors have been used for many years in ~25 the drilling of oil and gas wells. Usually, the bearing shaft of 26 the motor, and the drill bit, will rotate with resp~ct to the ~60ss/ll:623:0370~.l000:03ns/sls~3a~ 8 . ~.
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1 housing of the drilling ~otor. The housing is connected to the 2 bottom of a conventional drill string, made up of drill collars, 3 and sections of drill pipe and, perhaps, other components well 4 known to those skilled in the art. At the surface, the drill string is connected to a kelly, which is bounded in the rotary 6 table of a drilling rig.
7 Drilling fluid, or "mud", is pumped through the drill 8 string to the bottom of the hole, and returns up the annulus 9 between the dx ll string and the wall of the borehole. The mud cools the drilling tools and removes the cuttings from the hole.
11 If a downhole drilling motor is hydraulic, the mud also supplies 12 the hydraulic power to operate the motor.
13 One type o~ hydraulic downhole motor is the progressive 14 cavity type, also known as the Moineau motor. This type of motor has a helical rotor within the cavity of a stator, and the stator 16 is connected to a housing. As mud is pumped through the stator, 17 the rotor is rotated. As the rotor rotates, it also gyrates, or 18 orbits, in the reverse direction relative to its rotation. A
19 universal joint or rod or other connection must be used to connect the gyrating rotor to the bearing shaft of the motor, kecause the 21 bearing shaft does not gyrate.
22 one type of connector has universal joints, which connect 23 the en~s of a straight rod to the rotor and to the bearing shaft.
24 The universal joints take only torsional load, so a ball and race assembly is used to take the thrust load. Rubber boots are clapped 5609J/11:623:0370`1.1000:03/28/91:8:53~ 9 ;
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2 ~ 2 ~ 9 1 over the univ~rsal joints to keep mud out of the ball and race 2 assembly.
3 Other downhole motors have long, flexible connecting 4 rods, which flex to compensate for the gyration of the rotor. Such connecting rods must be able to bear both thrust loads and torque 6 loads. The rods must also be flexible enough to allow the 7 eccentricity between the rotor and the bearing shaft, with a 8 reasonably small side load. A one-piece connecting rod, or a rod 9 assembly, that has a required ~lexibility, also has torsional flexi~ility and helps the rotor run smoothly when dynamic external 11 torques are encountered.
12 Mud motors may also be of the "turbodrill" variety, 13 wherein a bi~ is suspended o~ a lower end of a shaft which is, in 14 turn, supported within a case suspended ~rom the lower end of a drill string, and a turbine motor is arranged within an angular 16 space between the case and shaft to cause the shaft and bit to 17 rotate with respect to the case and string in response to the 18 circulation ~ dril~-ng Pluids downwardly through the drill string 19 and motor and out the bit into the annular space of the borehole.
Typical o~ such turbine motors for drilling is as described in U.S.
21 Patent No. 3,971,450.
22 It is an increasingly wide spread practice to drill 23 horizontal boreholes, especia~y in productive hydrocarbon deposits Z4 in order to drain the deposit to a distance which is considerably g~eater than its thickness, whereas a vertical borehole drains the 26 deposit only to a distance corresponding to its thickness. Within 56094/1~:623:03704.1000:031~8191:8:53am lO
' ~ ' , 1 the deposit zone, a horizontal borehole cuts through geological 2 strata at a small angle or even passes through the same stratum 3 over an appreciable distance of the order of several hundrPd 4 meters, the axis of said borehole being substantially parallel to S the limits of said geological stratum.
6 The horizontal borehole drilled from a vertical well is 7 usually drilled within a productive form~tion. Most production 8 formations have substantial horizontal portions and, when 9 conventional vertical wellbores are employed to tap such production formationsr a large number of vertical bores must ~e employed.
11 With the drilling of a wellbore_having a non-vertical or horizontal 12 portion traversing the production formation, a much greater area of 13 the production formation may be traversed by the wellbore and the 14 total drilling ca5t5 in the field may be substantially decreased.
Additionally, after a particular horizontal wellbore has produced 16 all of the economically available hydrocarbons, the same vertical 17 wellbore may be re-drilled to establish another horizontal portion 18 extending in another direction, and thus prolong the utility of the 19 vertical portion o~ the we~l a~d increase the productivity of the well to inClu~e the total production formation.
21 By use of the phrase "deviated well", "deviated 22 wellbore", and "horizontal section", it is meant to refer to wells 23 and wellbores which comprise a vertical entry section communicating 24 through ~ re~ati~ely short-radius curvature portion with a non-vertical or horizontal portion communicating with the producing 26 formation. In most instances, the producing formation extends for 5609~ 623:03704.1000:03/28/91:8:S3am 1 1 ,:
` ' ' -1 a substantial horizontal extent and the generally linear wellbore 2 portion traverses a substantial horizontal extent of the producing 3 formation, at least up to a distance of 1000 to 2000 feet, or more.
4 The radius portion of the wellbore has a curvature of at least 10 per 100 feet of length, and preferably a curvature in the range of 6 about 10 to about 30 per 100 feet of length.
7 A study of the strata located above the horizontal 8 borehole and therefore traversed by the vertical well bore is very 9 important i~ order to obtain information relating to lithologic properties (chemical and geometric compositions), sedimentologic 11 and fracturing properties of rocXs, ~luid content and petrophysical 12 parameters (porosi~y, per~eability, compressibility, and the like~, 13 as well as structural conformation.
14 Up to the present time, formation analysts have been unable to gain direct access to data relating to geological strata 16 located beneath the horizontal borehole. In order to permit access 17 to these data, it has been necessary to carry out a very 18 approximate study based on geological survey-map assumptions, 19 dynamic meas~remen~s (p~ess~e-flow relations) within the horizontal borehole or between boreholes (intexferences) and 21 seismic surface measurements. Unfortunately, surface measurements 22 have low selectivity and are uncertain, in the first place, by 23 reason of the presence of a modified zone at the ground surface 24 and, in the second place, by reason of the considerable distance which has to be traversed by the sonic waves between the surface 26 and a very deep geological strataO Apart from the large amount of 5609~ 623:0370J.1000:03/28191:8:53nm 12 - . , .
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1 energy to be produced in order to permit propagation of waves to 2 the deepest geological strata, it is to be noted in addition that 3 the accuracy of measurements is relatively low for the reason that 4 the frequency employed has to be fairly low. In practice, measurements are accurate to within approximation of a few tenths 6 of meters. Moreover, data relating to strata located beneath a 7 horizontal borehole are very difficult if not actually impossible 8 to obtain by reason of the ~ct that these strata are too remote 9 from the borehole for a traditional well-log.
On acoustical well logging, the sonic waves which arrive 11 at the receiver or receivers (the logging tool) are therefore 12 practically those which have followed a path along the wall of the 13 vertical wellbore. In consequence, the measurements concern only 14 a small lateral portion of material of the geological stratum located between the transmitter or transmitters and the receiver or 16 receivers of the well-logging tool.
17 By "lateral portion of material'l is meant the thickness 18 of material tTave~sed by the transmitted acoustic wave and 19 considered in a direction substantially perpendicular to the vertical axis of the wellbore. It is readily apparent that the 21 measurements made relate primarily to the thickness of the 22 geological stratum as considered vertically and therefore the 23 Yertical portion of str~ located between the transmitter or 24 transmitters and the receiver or receivers.
Although the transmitted acoustic waves propagate over 26 considerable distance throughout the medium which surrounds the 56094/11:623:03704.1000:03/28/91:8:53an~ 13 .
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, 1 vertical wellbore, it has in fact proved impossible to receive and 2 record reflected waves except in rare cases due to heterogeneities 3 such as faults, fractures or salt domes~ for example.
This invention relates to data gathering instruments and 6 methods. More specifically, the invention relates to improYements 7 including use of geophones to detect return of seismic signals 8 transmitted into the earth, for example, during seismic exploration 9 for oil, gas and other minerals, and for purposes of detecting the proximate location of a drill bit, particularly in a horizontal 11 drilling application.
12 The invention is directed to providing an apparatus and 13 method for determining while drilling in the earth with a drill bit 14 the position of a well tool i.e. a bit, using seismic wav~s reflecting geologic formations in the earth, in which differences 16 in travel time and other characteristics of seismic waves generated 17 at the surface of the earth are sensed at a position on the drill i8 conduit immediate the drill bit, and seismic wave signals are 19 subjected to signal processing techniques that will give a better characteristic of the geologic formations in and around the 21 borehole.
22 The present invention also provides an apparatus and 23 method ~hich all~w subsurface s~ruc~ures to be delineated, so that 24 gas pockets, ~aults, fractures, stratigraphic layers andtor other subsurface characteristics can be detected and mapped, reflection 26 coefficients can be measured, drill bit location can be determined, ~609411~:623:0370~.1000:03128191.8:53a~n 14 '~ ' ," '~ ' ' ' ' ~
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1 hardness of the rock being drilled can be determined, condition of 2 the drill bit can be ascertained and structural conformation can be 3 evaluated.
4 In the present invention, geophone signals are processed S so that seismic wave generation sources at the surface of the earth 6 can be detected and imaged through sensing located at the drill 7 bit. Differences in travel time and other characteristics of the 8 seismic radiation will be sensed, and this will be the means by 9 which reflections from multiple causes can be distinguished and imaged.
11 The apparatus in accordance with the invention includes 12 a plurality of seismic w~Ye generators such as vibrators, 13 "thumpers" or explosives, or the l~ke, which are positioned at the 14 surface of the earth a~ a plurality of known positions with respect to a borehole. The seismic waves are received by geophones 16 immediate the drill bit, as such waves are being reflected by the 17 geologic formations between the surface signal generators and the 18 geophones immediate the bit, as well as $~rmations below the bit.
19 In the present invention, a seismic wave receiver is provided as part of ~he drilling equipment, at or near the bit, 21 and, preferably, immediate a Moineau or turbine mud motor and 22 provides one or more of a plurality of seismic wave sensors, ~23 detectors or ~eop~ones co~ec$ed thro~gh an electrical conduit 24 extending to the top of the well and which is amplified by a conventional amplifier extending to a seismic recording system. By 26 such capturing of measurements of amplitude, energy, character, 56094/ll:U3:03704.1000:03/28/91:8-53~n 15 , ~ ' .
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2 7 g 1 etc. of the received signals through the geophone in detection of 2 seismic shock waves initiated at the surface of the well from each 3 of one or a plurality of selected positions, a determination can be 4 made as to whether there is a gas-filled porous rock formation, or other hydrocarbon-containing formation, which is reflecting energy 6 from the seismic source at the top of the well to the geophone in 7 the drill string~ The presence of such a geologic formation would 8 be indicated by variation in amplitude or energy of the received 9 signals when the reflected seismic wave creates an interference pattern with a direct wave from a seismic source at the surface and 11 the geophones are in the resulting interference pattern at the 12 location of the drill string.
13 In the case of horizontal applications, conventional 14 recording reflections of reverberated sound waves at the surface of the earth may not allow a comparatively accurate depiction of 16 strata. By placing the geophone in proximity to the drill bit, a 17 more accurate depiction of such strata above and below can be 18 obtained because the reflection o~ the reverberated sound waves are 19 direct to the geophone in the well, itself.
Additionally, if the geophone is coupled with real time 21 processing of impulses fro~ the geophone, the exact location of the 22 drilling tool in proximity to the ~arget formation can be 23 ascertained~ The drilling t~ol can then be adjusted to alter its 24 course to follow the target formation.
2~ In particular, the present invention is directed to a 26 method and apparatus for obtaining seismic data pertaining to an s60s~lH:623:037~.l000:03ns/sl:ss3~ 16 ~ ~ 2 ~ 9 1 earth formation while forming a wellbore in the formation with a 2 drill string having a drill bit disposed at the distal end ther~of 3 The method includes providing vibration sensing means carried by 4 the drill string and immediate the drill bit. The vibration sensing ~eans are adapted to produce electrical signals related to 6 the seismic Yibrations generated at the earth's surface. Such 7 sensing means may also be placed in a "string" at the surface of 8 the earth to detect seismic wave reflections from formations and/or 9 drilling tools in the wellbore. Acoustic vibration generation means are also provided upon the earth's surface for activating and 11 transmitting ac~us-tic shock waves for detection by the vibration 12 sensing means. The first seismic wave signals generated by the 13 acoustic vibration generating means are captured such a~ by 14 amplifications, recordation, radio frequency or telephone cable transmissiQn, and ~e ~e, as well as the second signals which are 16 generated by the vibration sensing means or geophones. The second 17 signals are transmitted to the earth's surface, such as through the 18 drill string by means of a conduit inserted therein, or the like, 19 and wellbore and format~on parameters ~s well as the location of ZO the drill ~it, re~ative to a formation, are determined through 21 analyses~of the second signals, which may, or may not, be compared 22 with the first signals.
23 When th~ invention is inc~porated in conjunction with 24 the use of a drilling mud motor, such apparatus may include means for securing the motor between the drill string and the drill bit.
26 ~ stator of the progressive cavity type is preferably provided 5609~ 623:0370~.1000:03/28191:8:S3alu 17 ........ .
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1 which will includ~ operation with a rotor within the stator such 2 that the rotor rotates and gyrates in response to fluid flow of mud 3 through the stator. A housing is connected to the stator and a 4 bearing shaft is concentrically located within the housing and is rotatable about the longitudinal axis of the bearing 5haft and the 6 housinq. Bearing means are also provided between the housing and 7 the bearing shaft. Drive means extend between the rotor and the 8 bearing shaft for translating the rotation and gyration of the 9 rotor to the true rotation of the bearing sha~t. M~ans are provided for connecting the driv~ means to the rotor and for 11 connecting the draft means to the bearing shaft, respectively.
.
12 Vibration sensin~ ~eans are placed within the housing of the mud 13 motor and are adapted to produce the electrical signals relating to 14 the seismic vibration generated at the earth's surface and through at least a portion of the formation.
16 BRIEF DE~CRI2TION OF ~HE DRAWINGS
17 FIG. la is a schematic illustration depicting the apparatus 18 incorpora~ed in drilling through a lateral portion of material in 19 a horizontal wellbore, with surface seismic equipmant, as illustrated.
21 FIG. lb is an enlarged schematic illustration similar to Fig.
22 la, showing the wellbore tools.
~23 FIGs. 2a, 2b, and 2c each are longitudinal sectional drawings 24 of a mud motor ~or incorporation in the present invention.
FIG. 3 is an enlarged view of the upper portion of the device 26 shown in FIG. 2a.
~C609~1/11:623:03701.1000:03128/91:8:53am 18 -, , ` ,, ~. . . - ` - ` .
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1FIG. 4 is an enlarged sectional view of the geophone device 2shown in FIG. 3.
3FIG. 5 is a perspective view of the geophone in the housing 4for the mud motor guidance system.
5Di:~CRIPTION OF ~HE ~REFERREI) E~BODINEN~8 6Now with respect to FIGs. lA and 1~, there is shown at the top 7surface 1 of the wellbore 2 a rotary drilling rig 3 and a rotary 8table 4 through which is disposed a drilling conduit 5 ~ade up of 9sections of drill pipe 6, normally provided in 30 to 60 foot 10lengths. The drill pipe conduit 5 is introduced into the wellbore Il2 and is shown passing through a comparatively short vertical I2section 7 and into a horizontal section 8 below a lateral portion 13of material or production formation 9. At the lowermost end of the 14drill string conduit 5 is provided a bit 10 which is attached to a 15housing or pup joint 11 extending to a stabilizer 12 which, in 16turn, has its upper most end 13 secured at a bearing section 14 to 17a mud motor 323 having a housing 325.
18~At the upper most end 311 (FIG. 2A) of the mud motor housing l9325 is secured an adjustable bent sub 15, which assists in 20orienting the mud motor for traversing that portion o~ the wellbore 21extending between the completely vertisal ko the full or partially 22ho~izontal section of the wellbore. A second stabilizer 16 is 23provided at the upper most end 15a of the bent sub housing which, 24in turn, is secured to the lowermost end of the drill string 5.
25As shown in FIG. lAj there is illustrated a conventional 26seismic exploration operation at the surface 1 of the wellbore 2.
5609~ 623:0370~.1000:03n8/91:8~3am 1~
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1 A source of acoustic energy is shown at 17. Commonly, this may be 2 dynamite or a truck 18 having a base plate 19 mounted on a jack 20, 3 so that the entire truck may be lifted of f the ground, upon the 4 base plate 19. Vibration is then imparted to the entire truck 18.
The acoustic wave 21 is shown generated by the dynamite 17 and 6 passes înto the surf~ce of the earth and varying rock layers 9 7 along wave paths indicated general~y at 21.
8 The waves may be reflected from a subsur~ace layer, such 9 as 9 to a geophone 23 in the wellbore 2, as described below. The wave may also be reflected from the subsurface layer 9 backupwardly 11 50 to be dete ted by geophones 23, at the suxface of the wellbore.
12 ~ypically, such surface geophvnes 23 will simply ~omprise a body 13 having a spike portion for firm insert~oD into the surface of the 14 earth.
The geophones 23 used at the surface of the earth may, or 16 may not, be the same as the geophone 23 contemplated for use within 17 the well and in association with the drill string S immediate the 18 drill ~it 10.
19 ~any types of sensing arrays or geophones 23 can be used at the top surface 1 oP t~e wellbore to detect seismic waves 21 generated éither at the top of the wellbore (waves 21) or reflected 22 within the wellbore itself, (waves 50) such as arrays extending 23 radially outward from a ~oint near t~e mouth o~ the wellbore 2.
24 Alternatively, the sensing arrays can ~e in a circle, the center of which i5 at the mouth of the wellbore 2. The sensing array might 26 be spaced, in a selected manner, in one or more concentric circles.
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1 The sensing arrays can be irregular in geometry. A single geophone 2 2.3 can be moved from point to point to form the sensing array or a 3 plurality of geophones or sensors may be used to form a sensing 4 array.
Now referring to FIG. 4, within the body portion or 6 housing 35 of the geophone 23 is mounted a magnetic mass 25 within 7 a coil 39 for oscillation purposes, so that when the geophone 23 8 oscillates in response to receipt of the acoustic wave 21 through 9 the formation 9, the magnetic ~ass 25 oscillates with respect to the coil 39, so tha~ the coil 39 outputs an electric signal through ll lines 26a, 26b which is provided to the interior of the drill 12 ~tring 5 to the top l of the wellbore 2.
13 The geophonP 23 also has upper and lower spring members 14 28, 29 between ~ch ars placed magnet caps, 30, 31. A header 32 is positioned at the top of the geophone 23 through which are 16 received electric terminals 26a, 26b extending to the conduit 26 17 disposed within the drill string conduit 5 and extendable to the 18 top surface 1 of the wellbore 2. A coil terminal 33 and a pigtail 19 (not s~own) extend to respective terminals 26a, 26b. A bottom support 34 holds in place the housing 35 having its upper end 21 received around the lower portion of the header 32.
~22 The geophone 23 used in such seismic exploration 23 ~ activities typi~ally is placed in a hermetically sealed housing.
24 This protects the geophone 23 from invasion of drilling fluid, when the geophones are to be placed in the wellbore 2. The housing 26 provides a North seekin~ reference element. The North-seeking 56094ill:623:n370~.1000:03/28/91:8:53am . 2 1 ~, ' ' .
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ri g 1 reference may ~e constructed with and made of a North-seeking 2 gyroscope and cooperative accelerometer system~ Thus, the 3 equipment may "tumble" as it moves to any relative orientation in 4 the well. Even though it may take any angular position in space, it is not blind to its orientation. That is, it is able to locate 6 its orientation relative to a particular reference system (North on 7 the earth in this instance) and is therefore able to provide an 8 azimuthal reference relative to a seismic wave generation signal at 9 the surface of the well.
With reference to FIGS. 2A and 2B, typically, the mud ll motor 323 of the present invention will include a guidance system 12 (not shown), which may be in the ho~sing 311, which responses to 13 signals received through the electric conduit 26 to the top of the 14 well. Such guidance system enables the m~d motor 323 to alter its course through the uel~re as ~he wellbore moves from vertical to 16 horizontal relative to the formation 9. Alternatively, such 17 downhole guidance system may be contained in a tubular housing or 18 joint in proximity to the uppermost end of the mud motor 323.
19 Accordingly, it is contemp~ated in this invention that the geophone ~3 may be placed ~'~her in the mud motor housing itself, such as 21 housing 311, or, alternatively, within a housing immediately above 22 or adjacent to the mud motor 323, such as in the housing for the 23 downhole guidance system components. Such location for the 24 yeophone 23 will ~e sufficiently immediate the drill bit to make a satisfactory determination of the proximate location of the drill 26 bit relative to a fixed location.
56094/11:~23:0370~t.1000:03128/91:8~S3~D 2 2 ~ . .
l The signal can then be amplified and recorded by mobile 2 e~uipment carried within a second truck 27, and may be processed in 3 conventional way. The signal generated by the downhole geophone 23 4 may also be compared to a signal generated by one or more geophones 23 at the surface 1 of the wellbore 2, which signals extend through 6 line 23a to a conventional amplifier recorder in such mobile 7 equipment 27, and compared with the signal sent by the downhole 8 geophone 23 through the conduit 26 to the top 1 of the wellbore for 9 detecting the location of the drill bit 10 and for determining other well parameters.
11 Referring now to FIGs. 2a, 2b and 2c, a bypass valve 12 housing 311 is connected to the lower end of the drill string 5.
13 The drill string 5 consists of drill collars tnot shown) and 14 sections of drill p~pe ~, and extends upward to the drilling rig 3 at the top sur~ace 1. Drilling fluid, or "mud," is pumped through 16 the bore 315 of the drill string 5 into the bore 317 of the bypass 17 valve housing 311.
18 The mud forces a shuttle 319 downward to close off some 19 bypass ports 321. When the bypass ports 321 are open, mud can escape from the bore 315 of the drill string 313 while the drill 21 string 313 is being removed from the hole. Mud can enter the bore 22 315 of the drill string 5, through the bypass ports 321, when the 23 drill string 5 is put into the wel~k~re 2. When the bypass ports 24 321 are closed by the shuttle 319, the mud is directed downward into a downhole drilling motor 323.
S609~ 623:0370~.1000:031~8/91:8:53am 23 ~.
1 The housing of the downhole drilling motor 323 has three 2 parts; an upper housing 325, a connecting rod housing 327, and a 3 bearing housing 329. The cylindrical upper housing 325 is 4 connected to the lower end of the bypass valve 311, and houses a progressive cavity motor. The progressive cavity motor has a 6 flexihle stator 331, which is connected to the inner surface of the 7 upper housing 325. A helical rotor 333 is mounted within the 8 stator 331. As mud flows downward through the cavities 335 between 9 the stator 331 and the rotor 333, fluid pressure causes the rotor 333 to rotate.
11 As the rotor 333 rotates, it also gyrates, or orbits in 12 the reverse directi~n. As shown in FIG. 26, a connecting rod 13 assembly 337 c~nnsc~s the lowe~ end 339 of the rotor 333 to a 14 rotating shaft cap 341, which is firmly secured to a rotating bearing shaft 343. The connecting rod asse~bly 337 must be 16 flexlble enough to translate the gyrating motion of the rotor 333 17 to the true rotation of the bearing shaft 343.
18 The connecting rod housing 327 is connected to the lower 19 end of the upper housing 32~, and encloses the connecting rod assembly 3;37. -The bearing housing 339 is connected to the lower 21 end of the connecting rod housing 327, and completes the housing of 22 the drilling motor 323. The bearing shaft 343 is mounted 23 concentri~al~y within the ~earing housing 329.
24 The lower end of the drilling motor 323 is shown in FIG.
2c. Various radial bearings 345 and thrust bearings 347 transmit 26 loads between the rotating bearing shaft 343 and the bearing s60s~ 6z3:037~.l~:03ns/sl:s~3~ 24 -.
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1 housing 329. A rock bit 349, which is threaded onto the bearing 2 shaft 343, digs the borehole as it rotates. In order to drive the 3 rock bit 349 properly, the bearing shaft 343 must rotate with a 4 true rotation about the longitudinal axis 351 of the bearing shaft 343 an~ ~he housing 329.
6 During operati~n, ~ circulates through the drilling 7 motor 323 to rotate the rotor 333. As the rotor 333 rotates the 8 lower end 339 of the rotor 333 also gyrates. The connecting rod 9 assembly 337 must translate the rotation and gyration of the rotor 333 to the ~rue rotation of the bearing shaft 343. The flexible 11 rod 353 bends and flexes to co~pensate for the eccentricity between 12 the rotor 333 and the ~earing ~haft 343.
13 Now, with re~erence to FIG. 5, th~ housing 3~1 of the mud 14 motor 323 contain~ ~be ~Pop~o~e Z3 centrally axially oriented therein and secured in place of internally of a donut 41. The 16 donut 41 has a series of radially spaced splines 37 securing the 17 housing 35 to the mud motor housing 311. Mud flow passages 38 are 18 defined between each of the splines 37. Accordingly, the l9 positioning of the geophone within the housing 311 will not adversely inter~ere with efficient mud flow through the housing 311 :21 and to the-valve member 319, for proper activation of the m~d motor :22 323.
23 The cond~t 26 extends ~el~w the geophone 23 by means of 24 a conduit member 26a to a central electronic control assembly generally depicted at 39 to generally indicate positioning of the 26 guidance controls for the mud motor 323.
5609~ 623:0370$.1000:03/28/91:~:53am 25 ~, :
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, l The conduit elements 26a, 26b extending from the top 32 2 of the geophone 23 are secured within a wet connection 40 on the 3 conduit 26, joining conduit elements 26a therein. The conduits 4 26a, 26b of the geophone 23, together with conduits forming a part of the downhole mud motor guidance system extending from the 6 control 5~ throuqh the conduit elements 26c, all extend within the 7 interior the drill string 5 to the top of the wellbore l, with the 8 conduits for the geophone 23 extending to the conventional 9 amplifier (not shown), recorder ~not shown), radio or telephone transmitter (not shown) in the control vehicle 27.
12 As state~ a~o~e, the present invention is directed to a 13 method and apparatus for utilizing seismic wave signals during the 14 actual formation of the wellbore to determine formation characteristics, wellbore integrity, proximate location of a 16 particular downhole tool, such as a drill bit, or the like, as well 17 as structural confor~ation data. Accordingly, a drill string 5 is 18 made up at the ~op s~r~ace ~ ~y securing sections of drill pipe 6 19 to the lower end of which is secured an upper centralizer 16, which ZO is joined at its lowermost end by a bent sub 15 which, in turn, is 21 secured at its lowermost end to a mud motor 323 which activates a 22 drill blt 10 when a rotorlstator assembly in the mud motor 323 is 23 hydraulic~l~y activated by drilling fluid. The assembly is 24 introduced into the wellbore 2 and extends through a generally 2~ vertical section 7 immediate a formation 9 ~or ultimate directional .
~609~ 623:0370~.1000:03/28/91:8:53a~n 26 ,.. .,,~ :., : , 7 rj 9 1 drilling into a lateral portion of material or horizontal sectiOn 2 8 (FIG. la).
3 As the borehole 2 is extended, additional section 6 of 4 the drill string 5 will have to be inserted through the rotary table 4 on the rig 3. Accordingly, typically, reciprocation of the 6 bit lO is temporarily aborted by terminating circulation of mud 7 down the drill string ~ and to the mud motor 323. During such 8 time, the acoustic vibration generation means are activated at the 9 surface 1 of the wellbore 2, such as by excitement of the vibrator 19 on the truck 18, or by explosion, indicated at 17, of dynamite, 11 or other material, sending a_patterned series of seismic shock 12 waves 21. Such shock waves wi~l reverberate as a result of the 13 presence of the formation 9 and will be reflected in echo signals 14 50 redirected to the top sur$ace 1 in the vicinity of the wellbore 2. Su~h s~ic ~aves 21 wi~l also be detected by the downhole 16 geophone 23, as the vibration sensing means. Accordingly, electric 17 signals will be produced by the downhole geophone 23 and will ~e 18 sent to the top of the well through the conduit 26 within the 19 interior of the ~rill s~ring 5. The seismic wav~ signals 21 generated by the explosi~n 17 (or the vibrator 19) are captured, 21 such as by recording~ radio/telephone transmission, electronic 22 storage, and the like through appropriate conventional mechanisms 23 in the control truck 27. Additionally, the signals generated by 24 the downhole geophone 23 at the m~d motor 323 are likewise captured. By comparing the seismic wave signals 21 with the 26 signals generated by the downhole geophone 23, in numerous manners 5609~ 623:037W.1~00:03/2819t:8:53a~ 27 `
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1 and alternatives )cnown to those skilled in the art, the proximate 2 three-dimensional location of the drill bit 10, together with other 3 parameters, as described above, relative to the explosion 17 can be 4 determined, and the direction of the mud motor 323 and drilling conduit or string 5 may be altered, accordingly, or confirmed, if 6 no alteration of direction is required.
7 When surface geophones 23 are provided, such geophones 23 8 will detect seismic echoes generated by the initial seismic wave 21 9 reflections 50 through one or more formations, such as formation 9, back to the surface 1, and additional conventional formation and 11 other data can be obtained, in conventional fashion.
12 Althou~h the invention has been described in terms of 13 specified embodiments which are set forth in detail, it should be ~4 understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments 16 and operating techniques will become apparent to those skilled in 17 the are in view of the disclosure. Accordingly, modification are 18 contemplated which can be made without departing from the spirit of l9 the descri~ed invention.
~20 :;~
s60s4/il:623:0370~.l000:03n8/sl:s~3am 28 , . .. . . . .
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Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
(1) A method for obtaining seismic data pertaining to one-or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(2) A method for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining the location of said drill bit relative to said acoustic vibration generating means by comparing said first signals and said second signals.
(3) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) comparing said first signals and said second signals to determine selective characteristics of one or more formations including the step of determining the location of origin of said second signals based on the time of arrival at said vibration sensing means of said first seismic wave signals.
(4) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means; and (4) means for capturing said second signals generated by said vibration sensing means.
(5) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(6) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
and (f) comparing said first signals and said second signals.
(7) A method for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
and (f) determining the location of the drill bit in relation to said acoustic vibration generating means by comparing said first signals and said second signals.
(8) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
(f) determining the location of origin of said second signals based on the the of arrival at said vibration sensing means of said first seismic wave signals; and (g) determining the location of the drill bit in relation to said acoustic vibration generating means by comparing said first signals and said second signals.
(9) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) electric conduit means within said drill string having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of wellbore;
(4) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(5) means for capturing second signals generated by said vibration sensing means; and (6) means for determining selected characteristics of one or more of said formations by comparing said first signals and said second signals.
(10) Apparatus for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) electric conduit means within said drill string having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of wellbore;
(4) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(5) means for capturing second signals generated by said vibration sensing means; and (6) means for determining the location of said drill bit in relation to said acoustic vibration generating means.
(11) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and said drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotor rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft;
(b) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means; and (f) comparing said first signals and said second signals.
(12) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and said drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotor rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft;
(b) providing vibration sensing means in communication with the drill string and within the housing of said motor means, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means; and (f) comparing said first signals and said second signals.
(13) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) introducing said drill string into said well to a predetermined approximate location;
(d) temporarily aborting the reciprocation of said drill bit;
(e) actuating said acoustic vibration generating means to transmit acoustic shock waves to said vibration sensing means;
(f) capturing first seismic wave signals generated by said acoustic vibration generation means;
(g) capturing second signals generated by said vibration means; and (h) comparing said first signals and said second signals.
(14) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (c) introducing said drill string into said wellbore to a predetermined approximate location, said drill string including motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft, for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft.
(15) A method for determining selected characteristics of one or more formations and/or to determine the location of a drill bit while obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) actuating fluid driven motor means to reciprocate said drill bit;
(d) temporarily terminating the reciprocation of said drill bit;
(e) actuating said acoustic vibration generation means to transmit acoustic shock waves for detection by said vibration sensing means;
(f) capturing first seismic wave signals generated by said acoustic vibration generating means;
(g) capturing second signals generated by said vibration sensing means; and (h) comparing said first signals and said second signals to determine selected characteristics of one or more formations and/or to determine the location of said drill bit relative to said acoustic vibration generating means.
(16) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a reciprocal drill bit disposed at the distal end thereof, said apparatus comprising: vibration sensing means carried by said drill string immediate said drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface.
(17) The apparatus of claim 16, further comprising:
(a) means for capturing signals generated by said vibration sensing means.
(18) The apparatus of claim 16, further comprising:
(a) means for capturing signals generated by said vibration sensing means; and (b) means for comparing said vibration sensing means signals to acoustic vibration generation signals generated at the earth's surface for determining selected characteristics of at least one of said formations and/or for determining the location of said drill bit relative to a predetermined location.
(19) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (3) means for capturing the signals generated by said vibration sensing means for determining selective characteristics of one or more of said formations and/or for the location of said drill bit relative to said acoustic vibration generating means.
(20) A method for obtaining seismic data pertaining to one or more formations while forming a wellbore through a lateral portion of material with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means, (c) capturing first seismic wave signals generated by said acoustic vibration generating means; and (d) capturing second signals generated by said vibration sensing means.
(21) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising of steps:
(a) providing fluid-driven motor means for reciprocating said drill bit;
(b) providing vibration sensing means in communication with a drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface; and (c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means.
(22) The method of claim 21 further comprising the step of:
(a) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means.
(23) The method of claim 21 further including:
(a) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (b) capturing first seismic wave signals generated by said acoustic vibration generating means.
(24) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising.
(a) fluid-driven downhole motor means for reciprocating said drill bit;
(b) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adaped to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(c) acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) means for capturing second signals generated by said vibration sensing means; and (f) means for comparing said first signals and said second signals.
(25) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by the drill string and immediate the drill bit;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(e) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(26) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by the drill string and immediate the drill bit;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means;
(e) comparing said first signals and said second signals; and (f) determining the location of origin of said second signals based on the time of arrival of said first seismic wave signals at said vibration sensing means.
(27) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means; and (4) means for capturing said second signals generated by said vibration sensing means.
(28) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for comparing said first signals and said second signals.
(29) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means:
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(30) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a reciprocal drill bit disposed at the distal end thereof, said apparatus comprising:
(a) vibration sensing means carried by said drill string immediate said drill bit, and vibration sensing means immediate the top surface of said subterranean wellbore, each of said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
(1) A method for obtaining seismic data pertaining to one-or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(2) A method for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining the location of said drill bit relative to said acoustic vibration generating means by comparing said first signals and said second signals.
(3) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) comparing said first signals and said second signals to determine selective characteristics of one or more formations including the step of determining the location of origin of said second signals based on the time of arrival at said vibration sensing means of said first seismic wave signals.
(4) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means; and (4) means for capturing said second signals generated by said vibration sensing means.
(5) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(6) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by said drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
and (f) comparing said first signals and said second signals.
(7) A method for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
and (f) determining the location of the drill bit in relation to said acoustic vibration generating means by comparing said first signals and said second signals.
(8) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) providing electric conduit means within said drill string, said electric conduit means having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore, for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of the wellbore;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means through said electric conduit means;
(f) determining the location of origin of said second signals based on the the of arrival at said vibration sensing means of said first seismic wave signals; and (g) determining the location of the drill bit in relation to said acoustic vibration generating means by comparing said first signals and said second signals.
(9) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) electric conduit means within said drill string having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of wellbore;
(4) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(5) means for capturing second signals generated by said vibration sensing means; and (6) means for determining selected characteristics of one or more of said formations by comparing said first signals and said second signals.
(10) Apparatus for determining the location in a subterranean wellbore of a drill bit on a drill string using seismic wave generated data, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) electric conduit means within said drill string having a first end connectable to said vibration sensing means and a second end extendable to the earth's surface at the top of the wellbore for transmitting electrical signals produced by said vibration sensing means through the interior of the drill string and to the top of wellbore;
(4) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(5) means for capturing second signals generated by said vibration sensing means; and (6) means for determining the location of said drill bit in relation to said acoustic vibration generating means.
(11) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and said drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotor rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft;
(b) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means; and (f) comparing said first signals and said second signals.
(12) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and said drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotor rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft;
(b) providing vibration sensing means in communication with the drill string and within the housing of said motor means, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) capturing second signals generated by said vibration sensing means; and (f) comparing said first signals and said second signals.
(13) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) introducing said drill string into said well to a predetermined approximate location;
(d) temporarily aborting the reciprocation of said drill bit;
(e) actuating said acoustic vibration generating means to transmit acoustic shock waves to said vibration sensing means;
(f) capturing first seismic wave signals generated by said acoustic vibration generation means;
(g) capturing second signals generated by said vibration means; and (h) comparing said first signals and said second signals.
(14) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (c) introducing said drill string into said wellbore to a predetermined approximate location, said drill string including motor means for reciprocating said drill bit, said motor means including:
(1) means for securing said motor means between said drill string and drill bit;
(2) a stator of the progressive cavity type;
(3) a rotor, within the stator, wherein the rotates and gyrates in response to fluid flow through the stator;
(4) a housing connected to the stator;
(5) a bearing shaft, concentrically located within the housing, and rotatable about the longitudinal axis of the bearing shaft and the housing;
(6) bearing means between the housing and the bearing shaft;
(7) drive means extending between the rotor and the bearing shaft, for translating the rotation and gyration of the rotor to the true rotation of the bearing shaft;
(8) means for connecting the drive means to the rotor; and (9) means for connecting the drive means to the bearing shaft.
(15) A method for determining selected characteristics of one or more formations and/or to determine the location of a drill bit while obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string comprising tubular conduit members, said drill string having a reciprocal drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) actuating fluid driven motor means to reciprocate said drill bit;
(d) temporarily terminating the reciprocation of said drill bit;
(e) actuating said acoustic vibration generation means to transmit acoustic shock waves for detection by said vibration sensing means;
(f) capturing first seismic wave signals generated by said acoustic vibration generating means;
(g) capturing second signals generated by said vibration sensing means; and (h) comparing said first signals and said second signals to determine selected characteristics of one or more formations and/or to determine the location of said drill bit relative to said acoustic vibration generating means.
(16) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a reciprocal drill bit disposed at the distal end thereof, said apparatus comprising: vibration sensing means carried by said drill string immediate said drill bit, said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface.
(17) The apparatus of claim 16, further comprising:
(a) means for capturing signals generated by said vibration sensing means.
(18) The apparatus of claim 16, further comprising:
(a) means for capturing signals generated by said vibration sensing means; and (b) means for comparing said vibration sensing means signals to acoustic vibration generation signals generated at the earth's surface for determining selected characteristics of at least one of said formations and/or for determining the location of said drill bit relative to a predetermined location.
(19) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (3) means for capturing the signals generated by said vibration sensing means for determining selective characteristics of one or more of said formations and/or for the location of said drill bit relative to said acoustic vibration generating means.
(20) A method for obtaining seismic data pertaining to one or more formations while forming a wellbore through a lateral portion of material with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means, (c) capturing first seismic wave signals generated by said acoustic vibration generating means; and (d) capturing second signals generated by said vibration sensing means.
(21) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising of steps:
(a) providing fluid-driven motor means for reciprocating said drill bit;
(b) providing vibration sensing means in communication with a drill string and immediate the drill bit, said vibration sensing means being adapted to produce electrical signals related to the seismic vibrations generated at the earth's surface; and (c) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means.
(22) The method of claim 21 further comprising the step of:
(a) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means.
(23) The method of claim 21 further including:
(a) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means; and (b) capturing first seismic wave signals generated by said acoustic vibration generating means.
(24) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising.
(a) fluid-driven downhole motor means for reciprocating said drill bit;
(b) vibration sensing means carried by the drill string and immediate the drill bit, said vibration sensing means being adaped to produce electrical signals related to the seismic vibrations generated at the earth's surface;
(c) acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(d) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(e) means for capturing second signals generated by said vibration sensing means; and (f) means for comparing said first signals and said second signals.
(25) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by the drill string and immediate the drill bit;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(e) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means; and (e) determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(26) A method for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising the steps of:
(a) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by the drill string and immediate the drill bit;
(b) providing acoustic vibration generation means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(c) capturing first seismic wave signals generated by said acoustic vibration generating means;
(d) capturing second signals generated by said vibration sensing means;
(e) comparing said first signals and said second signals; and (f) determining the location of origin of said second signals based on the time of arrival of said first seismic wave signals at said vibration sensing means.
(27) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means; and (4) means for capturing said second signals generated by said vibration sensing means.
(28) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means;
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for comparing said first signals and said second signals.
(29) An apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a drill bit disposed at the distal end thereof, comprising:
(1) providing vibration sensing means at the top surface of said wellbore and vibration sensing means carried by said drill string and immediate the drill bit;
(2) acoustic vibration generating means upon the earth's surface for activating and transmitting acoustic shock waves for detection by said vibration sensing means:
(3) means for capturing first seismic wave signals generated by said acoustic vibration generating means;
(4) means for capturing said second signals generated by said vibration sensing means; and (5) means for determining selected characteristics of one or more formations by comparing said first signals and said second signals.
(30) Apparatus for obtaining seismic data pertaining to one or more earth formations while forming a subterranean wellbore with a drill string having a reciprocal drill bit disposed at the distal end thereof, said apparatus comprising:
(a) vibration sensing means carried by said drill string immediate said drill bit, and vibration sensing means immediate the top surface of said subterranean wellbore, each of said vibration sensing means being adapted to produce electrical signals related to seismic vibrations generated at the earth's surface.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67685991A | 1991-03-28 | 1991-03-28 | |
| US676,859 | 1991-03-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2064279A1 true CA2064279A1 (en) | 1992-09-29 |
Family
ID=24716318
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2064279 Abandoned CA2064279A1 (en) | 1991-03-28 | 1992-03-27 | Seismic data method and apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2064279A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2279328A4 (en) * | 2008-04-07 | 2015-10-14 | Prad Res & Dev Ltd | Method for determining wellbore position using seismic sources and seismic receivers |
| WO2022093034A1 (en) * | 2020-01-14 | 2022-05-05 | Equinor Energy As | Methods for estimating a position of a well path within a subsurface formation |
-
1992
- 1992-03-27 CA CA 2064279 patent/CA2064279A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2279328A4 (en) * | 2008-04-07 | 2015-10-14 | Prad Res & Dev Ltd | Method for determining wellbore position using seismic sources and seismic receivers |
| WO2022093034A1 (en) * | 2020-01-14 | 2022-05-05 | Equinor Energy As | Methods for estimating a position of a well path within a subsurface formation |
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