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Publication numberUS3288210 A
Publication typeGrant
Publication dateNov 29, 1966
Filing dateNov 4, 1963
Priority dateNov 4, 1963
Publication numberUS 3288210 A, US 3288210A, US-A-3288210, US3288210 A, US3288210A
InventorsBryant Harvey L
Original AssigneeExxon Production Research Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Orienting method for use in wells
US 3288210 A
Abstract  available in
Images(4)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Immun HUU- T N A Y R B I.- H. 6 6 9 l 9.. 2 V. o N

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ORIENTING METHOD FOR USE IN WELLS 4 Sheets-Sheet 1 Filed NOV. 4, 1965 coMPAss Harvey L. Bryant INVENTOR.

BYJQF M ATTORNEY Nov. 29, 1966 H. L.. BRYANT 3,288,210

ORIENTING METHOD FOR USE IN WELLS Filed Nov. 4, 1963 4 Sheets-Sheet 2 92 sELsYN mmc/HDR 42\ 4I 0R RECORDER 89 DETECTION INDICATOR- RECORDER 4,44 9| MOTOR swlTcH i L l SOPOWER SUPPLY FIG. 4

Harvey L. Bryan` INVENTOR.

ATTORNEY NOV- 29, 1966 H. BRYANT 3,288,210

ORIENTING METHOD FOR USE IN WELLS Filed Nov. 4, 1963 4 Sheets-Sheet 5 FIG'. 5 FIG. 6

Harvey L. Bryant INVENTOR.

BY 0. M

ATTORNEY Nov. 29, 1966 H. BRYANT 3,288,210

ORIENTING METHOD FOR USE IN WELLS Filed Nov. 4, 1963 4 Sheets-Sheet 4 500 C.P.M.

FRACTURE AZIMUTH DEPTH N0.l

FRACTUIRE AZIMUTH DEPTH N0 2 FIG'. 8 F/'. 9

Harvey L. Bryqnf INVENTOR ATTORNEY Unitedy States Patent() 3,288,210 ORIENTING METHGD FOR USE IN WELLS Harvey L. Bryant, Tulsa, Okla., assigner, by mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed Nov. 4, 1963, Ser. No. 321,229 4 Claims. (Cl. 166-4) The present invention concerns a system for orienta. tion of operations within a well bore. More particularly, the invention relates to an apparatus and method for determining the orientation of well logging or other instruments or devices in a cased hole although it does nd use in certain uncased borehole operations.

In conducting various operations in the drilling or logging or completion of wells drilled into the earth, it is quite frequently desirable to know the orientation of a tool or exploring device or the like in the remote location of the borehole. For example, in uncased boreholes it is frequently desirable to determine the orientation of natural fractures; in cased boreholes, it is frequently desirable to perforate at a given azimuth with respect to North, and in determining the orientation of man-made fractures.

In the past, various means have been provided fon orienting downhole operations. For example, various compass devices have been designed for such downhole operations. While they are quite helpful in certain instances, they have certain rather serious limitations in that they cannot be successfully used in boreholes which have been cased with steel pipe, nor can they be used successfully where there is a large amount of steel in the tool which ,is being used or inside a metallic drill string. One method of completing a Well is to set casing through the producing formation and then perforate the casing by the lowering of a gun perforator to the selectedl stratum and firing the gun through the casing, Under existing practices, the direction with respect to North which the gun is red is not usually known. A compass cannot be used in cased boreholes and gyroscopes are usually too large or otherwise expensive.

Certain refined recovery processes can be more effectively operated if the direction of the perforating of casing can be determined and controlled. Also, many formations when subjected to fracturing pressures, fracture in planes having generally the same direction. If the direction of the planes of the fracture can be determined,v then wells can be spaced and oriented with respect to North to take advantage of such knowledge. It is thus seen that there is a need for the reliable orientation of various logging, perforation and other operations performed within a well bore so that the actual directions of such orientation with respect to North can be accurately determined at any time within the life of thewell.

Briey, this invention includes a method of orienting an operation or a tool within a well bore drilled into a subterranean formation. A radioactive mass is placed in the wall of the well bore such as by the ring of a radioactive bullet into the formation. The bullet is placed in the well bore preferably not too far vertically from the proposed subsequent operations. The horizontal orientation of this mass, that is, its azimuth with relation to North, is determined. Subsequent logging or other operations are oriented from and in relation to the radio-f active mass whose azimuth is known. The azimuth of the radioactive bullet can be determined in a cased hole or with tools using a considerable amount of steel.

Various objects and a better understanding of the invention can be had with the following description taken in conjunction with the drawings in which:

FIG. 1 illustrates a tool useful in determining the azimuth of a red radioactive bullet.

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FIG. 2 illustrates schematically a remote magnet for use with the device shown in FIG. 1.

FIG. 3 is a section through line 3-3 of FIG. 1.

FIG. 4 illustrates a tool useful for orienting a perforating gun.

FIG. 5 illustrates a means of orienting a Whipstock drilling operations.

FIG. 6 illustrates an inilated impression packer in an uncased portion of a borehole.

FIG. 7 illustrates a plot of radiation intensity in an open hole to locate the azimuth of a radioactive bullet.

FIG. 8 illustrates a plot of a radiation intensity in a cased hole to locate the bullet azimuth.

FIG. 9 illustrates plots of radiation to locate a fracture.

Referring to the drawing and FIG. 1 in particular,4 there is shown a borehole 10 penetrating a subsurface formation 12. A radioactive bullet or mass 14 has been randomly shot into formation 12. The borehole in FIG.' l is open hole-that is, it has no casing set therein. Be-

fore discussing the apparatus shown in FIG. l, a brief discussion will be given on radioactive bullet 14. The radioactive bullet can be an iodine isotope. The radioactive material should have a half life of at least as long as it is contemplated that operations needing orientation with respect to North may be performed in the well. For example, the radioactive bullets should remain active for many years, for example, thirty to forty years or longer.) The radioactive material 14 is placed reasonably close vertically to the point in the well bore at which a subsequent operation requiring orientation is to be per. formed. For example, for use in a subsequent fracturing operation, bullet 14 is placed at a point approximately 2O feet, for example, above the zone to be frac tured. In general, bullet 14 should be close enough to the area of operation, i.e., the area at which subsequent orientation is to be conducted, so that when the radio\ active detector tool, described hereinafter, is lowered or raised from the radioactive bullet to the area of operation, the tool does not rotate any substantial amount. It is normally preferred that the radioactive bullet be placed above or below the area at which orientation operations may be conducted in the fracture so that other operations, will not dislodge the bullet or cause mistaken readings and the like.

Shown in FIG. 1 is a device for locating the orientation of radioactive bullet 14. Included therein is remote reading or recording radioactive directional detector 24 and a remote recording compass 18 connected below the the detector 24. Radioactive directional detector tool 16 is similar to that described in co-pending patent application Serial No. 780,387 filed December 15, 1958 for John C. McDue, Jr. Tool 16 includes a housing 20 in which is arranged a reversible motor 22, operable from the surface, and to which is connected a gear box 23, which in turn is connected to a rotatable shaft 26. This shaft 26 is connected to radiation detector 24 and a selsyn transmitter 30. Shaft 26 extends through the lower end of housing 20 and connects with the housing of compass 18 in a iixed position through a collar orunion or other desirable connectable joint 29, and a sub shaft 31. Subshaft 31 is made of a nonmagnetic material and is of a length to place compass 18 at a position suiciently removed from detector tool 16 so that any magnetic material in the detector tool does not seriously interfere with the compass.

Housing 20 is provided with bearings 32 which permit shaft 26 to rotate relative to housing 20 and sealing means such as O rings 34 are adapted to prevent fluid from entering housing 20. Drag springs 36 are arranged on the exterior of housing 20 and function to prevent rotation of housing 20 and to centralize the housing. The latter function is desired in order to maintain consistent radiation detection readings in any direction. Shaft 26 is provided with a slip ring assembly 38 for conducting electrical signals transmitted through a multiple conductor cable 40 which in turn is connected to multiple conductor cable 42 which leads to the surface. Conductor 44 conducts signals from compass 18 through one of the slip rings of assembly 38 to one conductor of multiple conductor 40 which is connected to multiple conductor cable 42 which extends to the surface. Other slip rings of assembly 38 conduct electrical signals from detector 24 to other conductors within multiple conductor unit 4) to multiple conductor cable 42 which transmits such electrical signals from the detector 24 to the surface. A conductor 46 connects multiple conductor cable 42 to motor 22; thus, there are individual electrical connections between the surface and motor 22, from the surface to detector 24 and from the surface to compass 44. Selsyn motor or transmitter 30, mounted about shaft 26, is connected through one ring of assembly 38 through a conductor circuit in multiple cables 40 and 42 to a selsyn indicator 92 located at the surface and as shown in FIG. 4. Selsyn transmitter 30 is not needed for operations in which compass 18 is operative but is useful in other operations discussed hereinafter.

Detector 24 is provided with a shield 48 having a window 49 so designed to conne the area of detection to a limited arc, as for example, an arc of of the well bore. This limited arc of investigation is more clearly seen in FIG. 3.

Compass 18 can be any compass which gives a remote reading at the surface of the direction in which a reference point on the tool is directed. For example, it can comprise, as shown in FIG. 2 a magnetic needle 50 which actuates a wiper 52 of a potentiometer 54. The measured resistance corresponds to the azimuth (angle a) of contact 53 which is taken as a reference electrode in defining the instrument position. The housing of potentiometer 54 is fixed with respect to shaft 26. The relationship of the radial position of reference contact 53 of potentiometer 54 and window 49 are the same or are known. Thus, by measuring the resistance of potentiometer S4, the direction of window 49 of detector 24 is at all times known. A suitable compass can be similar to that shown in U.S. Patent 2,609,513.

An important step in the system of this invention is the determination of the horizontal azimuth or radial position or orientation of radioactive bullet 14 with respect to a standard direction such as magnetic north. Attention will now be directed to the operation of the tool in FIG. 1 for determining the azimuth with respect to north of radioactive bullet 14. As stated above, radioactive bullet 14 is shot at random into the borehole wall. Such means for doing this are known. After bullet 14 has been placed in the formation, the tool shown in FIG. 1 is lowered into the open hole to the depth at which bullet 14 was fired. Means, such as bow or drag springs 36, are provided to prevent the tool from rotating. When the tool is placed in the borehole opposite bullet 14, its radial orientation is immediately known by the signal received at the surface through conductor 44 from compass 18. The actual radial position of window 49 can be aligned at the corresponding radial position of FIG. 7 with respect to north. Reversible motor 22 is then started and continuous readings or spot readings are made of the intensity detected by detector 24 as it is rotated 360. As detector 24 is rotated, shield 48 permits detector 24 to detect radiation only in a limited arc described by window 49 as the arc sweeps around 360 of the borehole. As shown in FIG. 7 a chart or record is made of the intensity of the radiation detected as the detector sweeps around the circumference of the borehole. The radiation from bullet 14 is of much greater intensity than that of the rest of the borehole. Thus, when the window of the shielded detector, which can be a standard commercially available sector-type gamma ray logging tool, points in the direction of the radioactive bullet, the increase in radiation caused by the radioactive bullet gives a large increase in reading as shown at 56 on the chart of FIG. 7. The azimuth of bullet 14 with response to magnetic north is thus located accurately as the position of the compass 18 is recorded or known at the time the detector detects or points in the direction of the radioactive bullet as indicated by the detection of maximum radiation intensity. On the chart of FIG. 7, from the center outwardly reects an increase in radiation detected by detector 24. Such a chart as shown in FIG. 7 is made by a suitable detector recorder or can be manually plotted as illustrated by the xs of FIG. 7. In FIG. 4 reference numeral 89 represents a detection indicator and/or recorder.

After the radioactive bullet has been shot into the formation and its azimuth determined, many different operations can be conducted from the marker thus established. For example, the system of the invention is especially useful in precisely locating the depth, azimuth, and nature of naturally occurring fractures in open hole. The determination of depth and azimuth of naturally occurring fractures is quite important to improve the engineering of secondary recovery projects, that is, Where a driving fluid is injected through one well and fluid is produced from a second well. For example, the Sprayberry Field in West Texas utilizes wells located along azimuth of natural fracture systems. It was found there, after a long and tedious reservoir engineering study, that the natural fractures of the system extended in planes which were more or less parallel, i.e., all in the same direction. The permeability in the direction of the azimuth of the natural fractures of the system Was about 144 times greater than the permeability perpendicular to the trend of the natural fracturing system.

In the practice of this system for determining the natural azimuth of natural fractures, a radioactive bullet 14a is first shot into the formation and then its orientation or its azimuth is determined as well as its depth. This is similar as described above in relation to FIG. 1 and FIG. 3. Attention is next directed to FIG. 6. Shown in FIG. 6 is a standard impression packer which can, for example, be a Lynes Pip packer which is described on page 3085 of the 196263 Composite Catalog of Oil Field Equipment and Services, published by World Oil, Houston, Texas. Shown thereon is a hole 60. A tubing 66 is suspended from the surface within the borehole. The packer of FIG. 6 has been modified from the standard version. A radioactive bead 68 is fixed at one radial position on the packer assembly and the packer assembly is supported from the lower end of tubing 66. The packer assembly includes an elastic inflatable sealing element 70 which is made, for example, from a resilient resistant rubber. The packer includes a hollow mandrel 72 which is secured to the lower end of tubing 66. The interior of mandrel 72 is in fluid communication with the interior of tubing 66. The ends 74 and 75 of sealing element 70 are sealings aixed to the exterior of mandrel 72. Ports 76 provide uid communication between the interior of mandrel 72 and the interior 71 of sealing element '70. Mandrel 72 has a valve seat 77 below port 76. A wire-line operated dog 78 seats or mates with seat 77 so as to close the lower ends of the interior of mandrel 72. The dog 78 is retrievable by wire line 79 to which a conventional overshot latch is attached.

The packer element 70 is inflated in a normal manner in the open hole at the depth corresponding to formation 64 where it is desired to determine the orientation of naturally occurring fractures. For example, dog 78 is dropped against seat 77 closing the lower end of mandrel 72. The tubing is lled with fluid and pressure is applied to the fluid and held. The packer is thus set. When the packer 70 is expanded against the borehole wall, it is expanded with such pressure that any fractures or cracks in the borehole wall are indicated on the exterior of packer element 70 inasmuch as the rubber material tends to be forced into such fissures or fractures and such indications are observable when the tool is removed to the surface. After the packer has been inflated, it is held long enough for impressions to set up which need take only a relatively short period of time depending on the rubber", but in most cases will be from about ive minutes to an hour.

When packer 70 is set by iniiation, radioactive bead 68 is also set in a fixed position. At this time, detector tool 16, shown in FIG. 1 from which compass 18 has been removed as by manipulation of joint 29, is lowered through tubing 66 until it reaches the depth of radioactive bullet 14a. At this time, the tool is operated similarly as in the obtaining of the chart of FIG. 7. This time the plot of the radiation intensity is made through or from within the tubing to locate the bullet azimuth as illustrated in FIG. 8 which shows the maximum intensity when the tool window 49 is pointed toward the active bullet as illustrated at 72. Thus, it is known that when the window of the detector 24 reaches maximum intensity it is at the azimuth previously determined when the compass 18 was connected to the tool in open hole. Thus, the orientation of tool 16 with respect to north is known. The detector tool 16 is then lowered a short distance until it is adjacent radioactive bead 68 fixed to the packer mandrel. This is easily accomplished as it is known how many joints of tubing are suspended in the well bore and the exact depth to bead 68 is known. When the tool 16 is lowered the short distance, it is in substantially the same radial position as it was when it surveyed the radioactive bullet 14a.

The azimuth is next determined for the bead 68 which is done in a manner similar to that described above with regard to the radioactive bullet 14. A plot of intensity of radiation detected is plotted as detector 16 is rotated. Such a plot is similar to that shown in FIG. 8 with the point of maximum intensity being pointed toward bead 68. The exact radial position of bead 68 in relation to the bullet is known as selsyn indicator 92, shown in FIG. 4, shows or indicates the rotation of detector 24 from its position at which window 49 was adjacent bullet 14a. As the horizontal azimuth of the bullet 14a is known, from previous determinations, then the orientation of the bead 68 is known. This determines the orientation of packer element 70 with respect to north. After the packer has been inflated long enough to obtain impressions thereon, pressure is equalized across the packer by removing dog 78 with a wire line overshot. The packer is then removed to the surface where it is examined. When the packer 70 is removed to the surface, the impressions on the packer can be studied and observed and an orientation of the fractures with respect to north can be determined precisely and accurately.

In some operations it is desired to perforate, in a specific direction, a casing which has been set in a borehole. An example of such a situation is when it is desired to inject a fluid from one well bore to drive formation iiuid toward a second well bore. In such instances it is frequently desired that the casing in the first well be perforated in the radial direction toward the second or producing well. Attention is now directed to FIG. 4 which shows a well bore 80 having casing 82 suspended therein. In this system, the radioactive bullet 14b was shot into the formation and its orientation determined as shown above in regard to bullet 14 before casing 82 was set. Tool 16 can be similar to the tool to that shown in FIG. l. However, in FIG. 4 compass 18 has been disconnected by manipulation of joining means 29. In FIG. 4, connected to shaft 26 of tool 16 is a swiveled joint 84. Extension joint 85 is connected to flexible joint 84. At the lower end of extension 85 is a second exible joint 86 to which is connected gun perforator 87. Gun perforator 87 has gun elements 88 which are arranged in a vertical row and are of a character such that when red, are all fired in the same radial direction within the borehole. Gun perforator 87 is connected through conductor and multiple conductor cable 42 to gun switch 94. When it is desired to perforate in a selected direction, the tool as shown in FIG. 4 is lowered through the casing 82 until the detector 24 of tool 16 is opposite bullet 14b. At this time detector 24 is rotated until the bullet is detected as illustrated above in regard to FIG. 8. When detector 24 is rotated, the gun perforator 87 is also rotated as they are both nonrotatably connected to shaft 26. After the orientation of window 49 is determined the entire tool is lowered until gun perforator 87 is in the vertical position at which itA is desired to perforate the casing 82. As the tool can be lowered several feet without any substantial rotation within the casing, e.g. 50 to feet, the direction in which gun elements 88 are pointed are known. In other words, the direction of iire of gun elements 88 is fixed relative to the location of the radioactive bullet 14b. Detector 24 then may be rotated by means of motor 22 to a position wherein the direction of re is that selected at the surface. The gun elements are then red by means of gun switch 94 in a conventional manner. A power supply 90 is provided for motor switch 91 and the gun switch 94.

In the drilling of boreholes in the ground, quite frequently it is desired to directionally deviate such holes. Directionally deviating means to change the drilling of the hole from the vertical to an angle with the vertical in a desired direction. A typical example of such a situation is when it is desired to drill several wells from one location. This can occur when the location of the drilling derrick is on land and the location at which the well bore is desired to penetrate the producing formation is under water. One of the problems in such directional drilling is the determination of the direction in which the directional deviation tool is oriented. This invention includes a system whereby the direction of the tool can be accurately determined and oriented.

Attention is now directed to FIG. 5. Shown thereon is a borehole 100 in which a radioactive bullet 14e` has been placed at a point above the elevation indicated at 102 Where it is desired to start deviating the hole 100 from the vertical. Shown in Well 100 is tubular drill string 104 suspended in a conventional manner from the surface by equipment not shown. At the lower end of drill pipe 104 is a bit 106. A whipstock 108 is shown suspended from casing 104. A radioactive bead 114 is placed off-center on the upper portion of whipstock 108 similarly as bead 68 of FIG. 6 to form an orienting point. A shear pin 110 connected to drill string 104 just above bit 106 supports the whipstock 108 in a lixed relationship with the drill string until the shear pin is sheared. The whipstock illustrated in FIG. 5 can, for example, be any well-known commonly used whipstock such as the Homco circulating and releasing whipstock shown on page 247 of the above-mentioned Composite Catalog of Oil Field Equipment and Services.

Before drill pipe 104 and whipstock 108 are positioned as shown in FIG. 5, a radioactive bullet 14e is randomly shot into the borehole at a point which will be slightly above shear pin 110. The azimuth of bullet 14C with respect to North is then determined as shown above. The drill pipe-whipstock combination shown in FIG. 5 is then lowered to where the point 112 of the whipstock is just above the bottom of the borehole so that the Whipstock can be rotated easily. A tool 16 is then lowered to the wellbore until it is opposite radioactive bullet 14C. At that time the orientation of the tool 16 is determined with respect to the bullet by rotating detector 24 until window 49 is facing bullet 14C. Tool 16 then is lowered from the level of bullet 14c down to where the detector 24 is at the same depth as bead 114. The detector is then rotated by reversible motor 22 and a record or indication made of the azimuth or radial location of bead 114 with respect to the azimuth of bullet 14e which is the same azimuth as the position of window 49 prior to rotation of detector 24. The radial relationship determines the direction at which the whipstock will direct the bit. As it is known which direction it is desired to direct the bit and the azimuth with respect to North of the radioactive bullet 14C is known, then the required radial relationship of the bullet 14c and radioactive bead 114 can be determined. The drill pipe is then rotated from the surface until this relationship is obtained.

Alternatively, tool 16 may be lowered to adjacent bead 114 initially. Detector 24 then is rotated until window 49 faces bead 114. When tool 16 is in this position, it is raised to the level of bullet 14C. The drill pipe is then rotated until a maximum reading is obtained which occurs when window 49 of detector 24 faces bullet 14e. The whipstock then can be properly oriented with respect to the direction of the radioactive bullet 14C, and consequently, with respect to North by rotating the drill string and placing the face of the whipstock in any desired direction, as selected at the surface. At this time, the whipstock is properly oriented with the direction as selected at the surface. At this time, pressure or force is applied to whipstock 108 as by letting the weight of the drill string downwardly onto the whipstock. The point of whipstock 112 is then set in the borehole. Additional pressure shears shear pin 110, then the bit is guided oif the face of the whipstock and drilling proceeds in desired direction.

In recent years hydraulic fracturing procedures for increasing uid production from subterranean formations have been used quite extensively. Basically, these hydraulic methods consist of pumping iluid into a formation, which contains uid desired to be produced, under suiiicient pressure to cause fracturing of the formation under treatment. The hydraulic pressure applied is sufficient to overcome rock stresses, thus creating a parting or fracturing within the formation. When the formation fractures, pumping of the fracturing fluid into the formation is continued so as to enlarge the fracture and extend them away from the well bore. Usually the fluid injected carries suspended grains of material which remain in the fractures as a propping agent to keep the fractures from closing when applied pressure of the fracturing fluid on the rock formation is released. Quite frequently such hydraulic fracturing method is performed in formations through which a casing has been set and the fracturing uid is injected through perforations of the casing.

Studies of reservoir engineering can be greatly improved or simplified if it can accurately be determined what the orientation of the man-made fractures are. The system of this invention permits the accurate determination of the azimuth or orientation of the fractures behind cased well bores. To accomplish this, a radioactive bullet is shot into the wall of the Well bore before the casing is run at a point either above or below where the fracturing is to take place. The orientation with respect to North of the radioactive bullet is determined as described above in relation to bullet 14 in FIG. 1. After the azimuth with respect to North of the radioactive bullet is determined, casing is set in the well bore in the usual manner. After the casing is set, it is perforated. Then a hydraulic fracturing fluid is pumped into the well bore through the perforations to fracture the formation. The fracturing fluid used in this invention, however, has a radioactive tracer added thereto. The radioactive tracer can be added toward the end of the fracture operation so that it is in that part of the fractures that are adjacent the casing at the end of the fracturing operation so that it can be easily detected by a radioactive detector within the well bore. The radioactive material can comprise a part of the propping agent which is normally placed in the fracturing iluid to maintain the fractures apart. Thus, when the pressure is released from the fracturing iluid, the particles having radioactive material or tracer will remain in the fractured zones and not be displaced by subsequent operations.

Tool 16 shown in FIG. l with compass 18 removed is then used to form a plot of the radioactive intensity detected at a point in the well bore at the same depth at which the formation is fractured. The orientation of the detector 24 at the depth of the fractured formation is determined relative to the azimuth of the radioactive bullet, similarly as described in the other operations hereinbefore. Usually, in determining the fracturing pattern it is desired to run the survey at more than one vertical location opposite the fractured formation. For example, there are two fracture azimuths plotted in FIG. 9, at depth No. l and at depth No. 2. From the two fracture azimuths determined in FIG. 9, the fracture pattern can be oriented. In general, it can be said if there is a high point of intensity detected as the detector tool 24 is rotated, then the fractures are more or less vertical, whereas, if the intensity is essentially the same as the tool is rotated, the fractures are more or less horizontal.

While there are disclosed above but a limited number of embodiments of the present invention, it is possible to produce still other embodiments without departing from the spirit or scope thereof. For example, the system is useful for determining the orientation of a core which is cut during the drilling of a borehole. Many core barrel assemblies are composed of an outer barrel which rotates with the bit in cutting the core and an inner core barrel for receiving the core. The inner barrel is used to catch the core when the desired length of core is cut, the core catcher of the inner barrel locks with the core and upon raising the core barrel assembly, the core is broken olf from the formation. That system is modied by placing a radioactive bead in a nonaxial position on the assembly in a fixed relationship with the core catcher of the inner barrel. Just before the core is broken from the formation, the tool 16 is used to determine the orientation of the bead with relation to a radioactive bullet of known azimuth similarly as the orientation of bead 68 with bullet 14h. It is therefore intended that the invention not be limited to the specific examples presented and it is desired that only such limitations be imposed on the appended claims as are stated therein.

What is claimed is:

1. An orienting method for use in wells comprising the steps of:

placing in a stratum surrounding a well bore a radioactive marker capable of being detected by a radiation detector; lowering into said well bore to the level of said radioactive marker a first radiation detector having a selected radical direction of radiation detection and capable, when rotated, of transmitting to the earths surface the angular position of said radioactive marker relative to the selected direction of radiation detection and compass means capable of transmitting to the earths surface the direction of North relative to said selected direction of radiation detection;

rotating said irst radiation detector and compass means and determining thereby the angular position of said radioactive marker relative to the selected direction of radiation detection and thereby the angular position of said radioactive marker relative to the direction of North;

removing said rst radiation detector and compass means from said well bore;

lowering in said well bore to the level of said marker a perforator having a selected radial direction of perforation and connected to a second radiation detector having a selected radial direction of radiation detection and capable when rotated of transmitting to the earths surface the angular position of said radioactive marker relative to the selected direction of radiation detection, said selected radial direction of perforation of said perforator being in a known xed relationship to the selected direction of radiation detection of said second radiation detector;

rotating said second radiation detector and said perforator until said direction of radiation detection is directed toward said radioactive marker;

lowering said radiation detector and said perforator to adjacent a desired level of perforation; and

then orienting said perforator to a desired direction of perforation relative to the angular position of said radioactive marker and the direction of north.

2. An orienting method for use in wells comprising the steps of: A L

placing in a stratum surrounding a well bore a radioactive marker capable of being detected by a radiation detector;

lowering into said well bore to the level of said radioactive marker a first radiation detector having a selected radial direction of radiation detection and capable, when rotated, of transmitting to the earths surface the angular position of said radioactive marker relative to the selected direction of radiation detection and compass means capable of transmitting to the earths surface the direction of north relative to said selected direction of radiation detection;

rotating said rst radiation detector and compass means and determining thereby the angular position of said radioactive marker relative to the selected direction of radiation detection and thereby the angular position of said radioactive marker relative to the direction of north;

removing said rst radiation detector and compass means from said well bore;

lowering a pipe string on which an inflatable impression packer is arranged into said Well bore until said packer is adjacent a section of the strata surrounding said Well bore below said radioactive marker at which it is desired to determine the presence of fractures;

inating said impression packer to a set position against the borehole wall;

said packer being provided with a reference radioactive marker capable of being detected by said radiation detector and having a xed angular position relative to the angular position of said radioactive marker placed in said stratum when said packer is in its set position;

lowering a second radiation detector having a selected radial direction of radiation detection and capable when rotated of transmitting to the earths surface the angular position of said radioactive marker placed in said stratum and the angular position of said radioactive marker provided on said packer relative to the selected direction of radiation detection in said pipe string to adjacent said radioactive marker placed in said stratum;

rotating said second radiation detector until said direction of detection is directed toward said radioactive marker placed in said stratum;

lowering said second radiation detector to adjacent said radioactive marker provided on said packer;

rotating said second radiation detector until the direction of detection is toward said radioactive marker provided on said packer and determining the relative angular positions of said radioactive markers to determine thereby the angular position of said radioactive marker provided on said packer and north; and

then deating said packer and removing it to the surface.

3. An orienting method for use in wells comprising the steps of:

placing in a stratum surrounding a well bore a radioactive marker capable of being detected by a radiation detector;

lowering into said well bore to the level of said radioactive marker a first radiation detector having a selected radial direction of radiation detection and capable, when rotated, of transmitting to the earths surface the angular position of said radioactive marker relative to the selected direction of radiation detection and compass means capable of transmitting to the earths surface the direction of north relative to said selected direction of radiation detection;

rotating said rst radiation detector and compass means and determining thereby the angular position of said radioactive marker relative to the selected direction or radiation detection and thereby the angular position of said radioactive marker relative to the direction of north;

removing said first radiation detector and compass means from said Well bore;

lowering in said well bore to below said radioactive marker a drill pipe provided with a whipstock having a face directed in a selected radial direction;

said whipstock being provided with a reference radioactive marker in a known fixed angular relationship to the radial direction of said whipstock face;

lowering a second radiation detector having a selected radial direction of radiation detection and capable when rotated of transmitting to the earths surface the angular positions of said radioactive markers relative to the selected direction of radiation detection in said drill pipe to the level of said radioactive marker placed in said stratum;

rotating said second radiation detector until said direction of detection is directed toward said radioactive marker placed in said stratum;

lowering said second radiation detector to adjacent said radioactive marker provided on said whipstock;

rotating said second radiation detector until the direction of detection is toward said radioactive marker provided on said whipstock and determining the relative angular positions of said radioactive markers to determine thereby the direction of north relative to the direction of the face of said whipstock; and

then orienting the face of said whipstock relative to north.

4. An orienting method for use in wells comprising the steps of:

placing in a stratum surrounding a well bore a radioactive marker capable of being detected by a radiation detector;

lowering into said Well bore to the level of said radioactive marker a first radiation detector having a selected radial direction of radiation detection and capable, when rotated, of transmitting to the earths surface the angular position of said radioactive marker relative to the selected direction of radiation detection and compass means capable of transmitting to the earths surface the direction of north relative to said selected direction of radiation detection;

rotating said first radiation detector and compass means and determining thereby the angular position of said radioactive marker relative to the selected direction of radiation detection and thereby the angular position of said radioactive marker relative to the direction of north:

removing said first radiation detector and compass means from said well bore;

lowering a drill pipe provided with a' whipstock having a face directed in a selected radial direction;

said whipstock being provided with a reference radioactive marker in a known xed angular relationship to the radial direction of said whipstock face;

lowering a second radiation detector having a selected radial direction of radiation detection and capable when rotated of transmitting to the earths surface the angular position of said radioactive marker relative to the selec in said drill pipe to the level of said radioactive marker provided on said whipstock;

rotating said second radiation detector until said direction of detection is directed toward said radioactive marker provided on said whipstock;

raising said second radiation detector to adjacent said radioactive marker placed in said stratum;

rotating said drill pipe and thereby rotating said second radiation detector until the direction of detection is toward said radioactive marker placed in said stratum and determining the relative angular positions of said radioactive markers to determine thereby the direction of north relative to the direction of the face of said whipstock; and

then orienting the face of said whipstock relative to north.

ted direction ofA radiation detection References Cited by the Examiner UNITED STATES PATENTS Doll 166--4 Arutunol 175-45 X Brokaw et al, 166-66 Storm 1661l7.5 Brown 166-l17.5 Goble 166-66 Ring 166-66 Anderson et al. Z-83.6 X Josendal et al 166-4 Hubbert et al 166-4 X Savrenman et al 166-187 Kenneday et al 166-35 X Smith 166187 Staadt 166-42.1 Pennebaker 166-4 Lanmon l66--55.l

Wilson 166-4 FOREIGN PATENTS CHARLES E. OCONNELL, Primary Examiner.

I. A. CALVERT, D. H. BROWN, Assistant Examiners.

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Classifications
U.S. Classification166/254.1, 166/255.1, 166/66, 33/312, 250/265, 166/55.1, 73/152.54
International ClassificationE21B47/024
Cooperative ClassificationE21B47/024
European ClassificationE21B47/024