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United States Patent Application 20110297371
Kind Code A1
Church; Nathan ;   et al. December 8, 2011

DOWNHOLE MARKERS

Abstract

The present disclosure relates to one or more methods and apparatus to dispose one or more markers within a subterranean formation. The method includes positioning a drill probe assembly in a borehole extending into the subterranean formation, drilling a hole through a sidewall of the borehole with a flexible shaft of the drill probe assembly, the hole penetrating the subterranean formation, and disposing a marker in the hole.


Inventors: Church; Nathan; (Missouri City, TX) ; Fitzgerald; Peter; (Paris, FR)
Serial No.: 796137
Series Code: 12
Filed: June 8, 2010

Current U.S. Class: 166/255.1; 166/66
Class at Publication: 166/255.1; 166/66
International Class: E21B 47/09 20060101 E21B047/09; E21B 47/01 20060101 E21B047/01


Claims



1. A method, comprising: positioning a drill probe assembly in a borehole extending into a subterranean formation; drilling a hole through a sidewall of the borehole with a flexible shaft of the drill probe assembly, the hole penetrating the subterranean formation; and disposing a marker in the hole.

2. The method of claim 1 wherein disposing the marking in the hole comprises using a plugging piston of the drill probe assembly to dispose the marker, at least partially, in the hole.

3. The method of claim 1 further comprising pushing the marker in the hole with the flexible shaft.

4. The method of claim 1 further comprising: drilling a through hole into a casing disposed within the borehole with the flexible shaft; and disposing a casing plug in the through hole formed in the casing.

5. The method of claim 1 wherein the hole is a first hole, and wherein the marker is a first marker, the method further comprising: re-positioning the drill probe assembly in the borehole; drilling a second hole through a sidewall of the borehole with the flexible shaft, the second hole penetrating the subterranean formation; and inserting a second marker into the second hole.

6. The method of claim 1 wherein casing is disposed within the borehole and cement is disposed, at least partially, within an annulus formed between the casing and the borehole.

7. The method of claim 1 wherein the marker comprises a radioactive material.

8. The method of claim 1 further comprising measuring a distance between the marker and a reference location.

9. The method of claim 8 wherein measuring the distance between the marker and the reference location comprises disposing a measurement tool within the borehole.

10. The method of claim 9 wherein the marker comprises a radioactive material and the measurement tool comprises a gamma radiation detector.

11. The method of claim 8 wherein the hole is a first hole, wherein the marker is a first marker, and wherein the reference location comprises a second marker disposed in a second hole, the second hole penetrating the subterranean formation.

12. The method of claim 8 wherein the distance is a first distance, the method further comprising: measuring a second distance between the marker and the reference location; and comparing the first distance and the second distance to each other.

13. An apparatus, comprising: a drill probe assembly configured to be disposed within a borehole extending into a subterranean formation, the drill probe assembly comprising a flexible shaft and a marker; wherein the flexible shaft is configured to drill a hole through a sidewall of the borehole, the hole penetrating the subterranean formation; and wherein the drill probe assembly is configured to dispose the marker within the hole.

14. The apparatus of claim 13 wherein the flexible shaft is configured to dispose the marker, at least partially, within the hole.

15. The apparatus of claim 13 wherein the drill probe assembly further comprises a plugging piston and a casing plug, wherein the plugging piston is configured to dispose the plug within a through hole formed within casing.

16. The apparatus of claim 15 wherein the plugging piston is configured to dispose the marker, at least partially, within the hole.

17. The apparatus of claim 15 wherein the drill probe assembly further comprises a moveable carriage configured to move with respect to the subterranean formation.

18. The apparatus of claim 17 wherein the flexible shaft and the plugging piston translate in unison with the movable carriage and are configured to extend from the moveable carriage.

19. The apparatus of claim 15 wherein the drill probe assembly further comprises a holder in which the plug and the marker are disposed.

20. The apparatus of claim 13 wherein the marker comprises a radioactive material.
Description



BACKGROUND OF THE DISCLOSURE

[0001] Wells are generally drilled into the ground or ocean bed to recover natural deposits of oil and gas, as well as other desirable materials that are trapped in geological formations in the Earth's crust. Wells are typically drilled using a drill bit attached to the lower end of a drill string. Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the bit, and may additionally carry drill cuttings from the borehole back to the surface.

[0002] In various oil and gas exploration operations, it may be beneficial to have information about the subterranean formations that are penetrated by a borehole. For example, certain formation evaluation schemes include measurement and analysis of the formation pressure and permeability. These measurements may be essential to predicting the production capacity and production lifetime of the subterranean formation.

[0003] Furthermore, additional formation evaluation schemes include placing radioactive markers in the subterranean formation along the borehole at predetermined intervals to measure formation changes over time. Typically, a first tool is run down the borehole, and radioactive markers, formed as bullets, are fired into the formation using explosives. After the placement of radioactive markers in the subterranean formation, a second tool featuring an array of gamma ray detectors is run down the borehole to measure the distance between the radioactive markers.

[0004] As such, subsequent measurements may show changes in the distance between radioactive markers, indicating compaction of the subterranean formation. Compaction of the subterranean formation may cause subsidence, defined as the local sinking of the Earth's surface due to changes occurring below the surface. However, traditional placement methods and techniques may be limited in operation, such as by requiring the use of explosives, and further requiring the placement of radioactive markers prior to casing the borehole to avoid residual holes. The methods may further be limited in that the penetration depth of the radioactive marker may not be controllable, thus, introducing uncertainty that may have a detrimental effect on the measurement quality.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0006] FIG. 1 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0007] FIG. 2 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0008] FIG. 3 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0009] FIG. 4 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0010] FIG. 5 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0011] FIG. 6 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0012] FIG. 7 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0013] FIG. 8 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0014] FIG. 9 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0015] FIG. 10 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0016] FIG. 11 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0017] FIG. 12 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0018] FIG. 13 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0019] FIG. 14 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0020] FIG. 15 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0021] FIG. 16 is a schematic view of apparatus according to one or more aspects of the present disclosure.

DETAILED DESCRIPTION

[0022] It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.

[0023] Referring now to FIG. 1, illustrated is a side view of a wellsite 100 having a drilling rig 110 with a drill string 112 suspended therefrom according to one or more aspects of the present disclosure. The wellsite 100 shown, or one similar thereto, may be used within onshore and/or offshore locations. A borehole 114 may be formed within a subterranean formation F, such as by using rotary drilling, or any other method known in the art. As such, one or more aspects according to the present disclosure may be used within a wellsite, similar to the one as shown in FIG. 1 (discussed more below). Those having ordinary skill in the art will appreciate that the present disclosure may be used within other wellsites or drilling operations, such as within a directional drilling application, without departing from the scope of the present disclosure.

[0024] Continuing with FIG. 1, the drill string 112 may suspend from the drilling rig 110 into the borehole 114. The drill string 112 may include a bottom hole assembly 118 and a drill bit 116, in which the drill bit 116 may be disposed at an end of the drill string 112. The surface of the wellsite 100 may have the drilling rig 110 positioned over the borehole 114, and the drilling rig 110 may include a rotary table 120, a kelly 122, a traveling block or hook 124, and may additionally include a rotary swivel 126. The rotary swivel 126 may be suspended from the drilling rig 110 through the hook 124, and the kelly 122 may be connected to the rotary swivel 126 such that the kelly 122 may rotate with respect to the rotary swivel.

[0025] An upper end of the drill string 112 may be connected to the kelly 122, such as by threadingly connecting the drill string 112 to the kelly 122, and the rotary table 120 may rotate the kelly 122, thereby rotating the drill string 112 connected thereto. As such, the drill string 112 may be able to rotate with respect to the hook 124. Those having ordinary skill in the art, however, will appreciate that though a rotary drilling system is shown in FIG. 1, other drilling systems may be used without departing from the scope of the present disclosure. For example, a top-drive (also known as a "power swivel") system may additionally or alternatively be used. In such a top-drive system, the hook 124, swivel 126, and kelly 122 are replaced by a drive motor (electric or hydraulic) that may apply rotary torque and axial load directly to drill string 112.

[0026] The wellsite 100 may include drilling fluid 128 (also known as drilling "mud") stored in a pit 130. The pit 130 may be formed adjacent to the wellsite 100, as shown, in which a pump 132 may be used to pump the drilling fluid 128 into the wellbore 114. The pump 132 may pump and deliver the drilling fluid 128 into and through a port of the rotary swivel 126, thereby enabling the drilling fluid 128 to flow into and downwardly through the drill string 112, the flow of the drilling fluid 128 indicated generally by direction arrow 134. This drilling fluid 128 may then exit the drill string 112 through one or more ports disposed within and/or fluidly connected to the drill string 112. For example, the drilling fluid 128 may exit the drill string 112 through one or more ports formed within the drill bit 116.

[0027] As such, the drilling fluid 128 may flow back upwardly through the borehole 114, such as through an annulus 136 formed between the exterior of the drill string 112 and the interior of the borehole 114, the flow of the drilling fluid 128 indicated generally by direction arrow 138. With the drilling fluid 128 following the flow pattern of direction arrows 134 and 138, the drilling fluid 128 may be able to lubricate the drill string 112 and the drill bit 116, and/or may be able to carry formation cuttings formed by the drill bit 116 (or formed by any other drilling components disposed within the borehole 114) back to the surface of the wellsite 100. As such, this drilling fluid 128 may be filtered and cleaned and/or returned back to the pit 130 for recirculation within the borehole 114.

[0028] Though not shown, the drill string 112 may include one or more stabilizing collars. A stabilizing collar may be disposed within and/or connected to the drill string 112, in which the stabilizing collar may be used to engage and apply a force against the wall of the borehole 114. This may enable the stabilizing collar to prevent the drill string 112 from deviating from the desired direction for the borehole 114. For example, during drilling, the drill string 112 may "wobble" within the borehole 114, thereby enabling the drill string 112 to deviate from the desired direction of the borehole 114. This wobble may also be detrimental to the drill string 112, components disposed therein, and the drill bit 116 connected thereto. However, a stabilizing collar may be used to minimize, if not overcome altogether, the wobble action of the drill string 112, thereby possibly increasing the efficiency of the drilling performed at the wellsite 100 and/or increasing the overall life of the components at the wellsite 100.

[0029] As discussed above, the drill string 112 may include a bottom hole assembly 118, such as by having the bottom hole assembly 118 disposed adjacent to the drill bit 116 within the drill string 112. The bottom hole assembly 118 may include one or more components included therein, such as components to measure, process, and store information. The bottom hole assembly 118 may also include components to communicate and relay information to the surface of the wellsite.

[0030] As such, in FIG. 1 the bottom hole assembly 118 may include one or more logging-while-drilling ("LWD") tools 140 and/or one or more measuring-while-drilling ("MWD") tools 142. The bottom hole assembly 118 may also include a steering-while-drilling system (e.g., a rotary-steerable system) and motor 144, in which the rotary-steerable system and motor 144 may be coupled to the drill bit 116.

[0031] The LWD tool 140 shown in FIG. 1 may include a thick-walled housing, commonly referred to as a drill collar, and may include one or more of a number of logging tools known in the art. Thus, the LWD tool 140 may be capable of measuring, processing, and/or storing information therein, as well as capabilities for communicating with equipment disposed at the surface of the wellsite 100.

[0032] The MWD tool 142 may also include a housing (e.g., drill collar), and may include one or more of a number of measuring tools known in the art, such as tools used to measure characteristics of the drill string 112 and/or the drill bit 116. The MWD tool 142 may also include an apparatus for generating and distributing power within the bottom hole assembly 118. For example, a mud turbine generator powered by flowing drilling fluid therethrough may be disposed within the MWD tool 142. Alternatively, other power generating sources and/or power storing sources (e.g., a battery) may be disposed within the MWD tool 142 to provide power within the bottom hole assembly 118. As such, the MWD tool 142 may include one or more of the following measuring tools: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, an inclination measuring device, and/or any other device known in the art used within an MWD tool.

[0033] Referring now to FIG. 2, illustrated is a side view of a tool 200 according to one or more aspects of the present disclosure. The tool 200 may be a "wireline" tool, in which the tool 200 may be suspended within a borehole 204 formed within a subterranean formation F. As such, the tool 200 may be suspended from an end of a multi-conductor cable 206 located at the surface of the formation F, such as by having the multi-conductor cable 206 spooled around a winch (not shown) disposed on the surface of the formation F. The multi-conductor cable 206 is then couples the tool 200 with an electronics and processing system 208 disposed on the surface.

[0034] The tool 200 may have an elongated body 210 that includes a formation tester 212 disposed therein. The formation tester 212 may include an extendable probe 214 and an extendable anchoring member 216, in which the probe 214 and anchoring member 216 may be disposed on opposite sides of the body 210. One or more other components 218, such as a measuring device, may also be included within the tool 200.

[0035] The probe 214 may be included within the tool 200 such that the probe 214 may be able to extend from the body 210 and then selectively seal off and/or isolate selected portions of the wall of the borehole 204. This may enable the probe 214 to establish pressure and/or fluid communication with the subterranean formation F to draw fluid samples from the formation F. The tool 200 may also include a fluid analysis tester 220 that is in fluid communication with the probe 214, thereby enabling the fluid analysis tester 220 to measure one or more properties of the fluid. The fluid from the probe 214 may also be sent to one or more sample chambers or bottles 222, which may receive and retain fluids obtained from the formation F for subsequent testing after being received at the surface. The fluid from the probe 214 may also be sent back out into the borehole 204 or formation F.

[0036] Referring now to FIG. 3, illustrated is a side view of a wellsite 300 having a drilling rig 310 according to one or more aspects of the present disclosure. A borehole 314 may be formed within a subterranean formation F, such as by using a drilling assembly, or any other method known in the art. A wired pipe string 312 may be suspended from the drilling rig 310. The wired pipe string 312 may be extended into the borehole 314 by threadably coupling multiple segments 320 (i.e., joints) of wired drill pipe together in an end-to-end fashion. As such, the wired drill pipe segments 320 may be similar to that as described within U.S. Pat. No. 6,641,434, filed on May 31, 2002, entitled "Wired Pipe Joint with Current-Loop Inductive Couplers," and incorporated herein by reference.

[0037] Wired drill pipe may be structurally similar to that of typical drill pipe. However, the wired drill pipe may additionally include a cable installed therein to enable communication through the wired drill pipe. The cable installed within the wired drill pipe may be any type of cable capable of transmitting data and/or signals therethrough, such an electrically conductive wire, a coaxial cable, an optical fiber cable, and or any other cable known in the art. The wired drill pipe may include having a form of signal coupling, such as having inductive coupling, to communicate data and/or signals between adjacent pipe segments assembled together.

[0038] As such, the wired pipe string 312 may include one or more tools 322 and/or instruments disposed within the pipe string 312. For example, as shown in FIG. 3, a string of multiple borehole tools 322 may be coupled to a lower end of the wired pipe string 312. The tools 322 may include one or more tools used within wireline applications, may include one or more LWD tools, may include one or more formation evaluation or sampling tools, and/or may include any other tools capable of measuring a characteristic of the subterranean formation F.

[0039] The tools 322 may be connected to the wired pipe string 312 during drilling the borehole 314, or, if desired, the tools 322 may be installed after drilling the borehole 314. If installed after drilling the borehole 314, the wired pipe string 312 may be brought to the surface to install the tools 322, or, alternatively, the tools 322 may be connected or positioned within the wired pipe string 312 using other methods, such as by pumping or otherwise moving the tools 322 down the wired pipe string 312 while still within the borehole 314. The tools 322 may then be positioned within the borehole 314, as desired, through the selective movement of the wired pipe string 312, in which the tools 322 may gather measurements and data. These measurements and data from the tools 322 may then be transmitted to the surface of the borehole 314 using the cable within the wired drill pipe 312.

[0040] A flexible shaft assembly, and one or more methods of using a drill probe assembly, in accordance with the present disclosure may be included within one or more of the tools and devices shown in FIGS. 1-3, in addition to being included within other tools and/or devices that may be disposed downhole within a subterranean formation. The drill probe assembly may be used to drill a hole through a sidewall of a borehole with a drilling probe, in which the hole may penetrate the subterranean formation. A marker may then be inserted into the hole, such as by the drill probe assembly, in which the marker may be detectable by a measuring tool to detect the location of the marker within the subterranean formation. The drill probe assembly may be used to dispose multiple markers within the subterranean formation, thereby enabling multiple locations of markers to be detected. As such, the location of the markers may be measured over a time period to determine movement of the markers with respect to each other and/or movement of the markers with respect to known other locations. This movement of the markers may be used to determine shifts and/or other movement that may be present within the subterranean formation.

[0041] Referring now to FIG. 4, illustrated is a schematic view of a drill probe assembly 402 according to one or more aspects of the present disclosure. The drill probe assembly 402, as shown, may be positioned in a borehole 404 formed within a subterranean formation F. For example, the drill probe assembly 402 may be anchored in the borehole 404. Anchoring the drill probe assembly 402 in the borehole 404 may be performed by extending an extendable anchoring member (not shown), in which an aperture 416 and the anchoring member may be disposed on opposite sides of the drill probe assembly 402. The drill probe assembly 402 may include a flexible shaft 406 configured to extend from the drill probe assembly 402. For example, the flexible shaft 406 may extend through the aperture 416, and substantially perpendicular to a central axis of the borehole 404. However, those having ordinary skill in the art will appreciate that the present disclosure is not so limited, as the flexible shaft 406 may extend in any direction with respect to the central axis of the borehole 404.

[0042] The drill probe assembly 402 may include a plugging piston 408 that extends in substantially the same direction as the flexible shaft 406. The plugging piston 408 may be configured to push a marker 410, or multiple markers, at least partially, into a hole drilled by the flexible shaft 406. One or more markers 410 may be disposed in a holder 412, which may be, for example, a revolver, a magazine, and/or any other holder known in the art. The holder 412 may axially align the marker 410 with the plugging piston 408. As shown, the flexible shaft 406, the plugging piston 408, and/or the holder 412 may be attached to a moveable carriage 414 that is configured to move with respect to the borehole 404 and/or other components of the drill probe assembly 402 to align the plugging piston 408 and marker 410 with the hole drilled by the flexible shaft 406. The moveable carriage 414 may additionally align the flexible shaft 406, the plugging piston 408, and/or the holder 412 with the aperture 416 in the drill probe assembly 402 and/or a tool body (not shown) housing the drill probe assembly 402. Components of the drill probe assembly 402 may then be able to move with respect to the moveable carriage 414, such as by having the flexible shaft 406, the plugging piston 408, and/or the holder 412 to be able to move with respect to the moveable carriage 414. For example, the flexible shaft 406 and the plugging piston 408 may be able to extend from the moveable carriage 414.

[0043] As shown in FIG. 4, casing 418 may be disposed within the borehole 404. An annulus 420 may then be formed between the casing 418 and the borehole 404, in which the annulus 420 may include cement 422. Therefore, the drill probe assembly 402 may also include one or more casing plugs 424 configured to seal the casing 418 after a marker 410 is disposed in the subterranean formation F. The casing plugs 424 may be disposed in the holder 412, such as by having an alternating sequence between the casing plugs 424 and the markers 410. The casing plug 424 may be positioned within the drill probe assembly 402 such that the casing plug 424 is axially aligned with, and pushed by, the plugging piston 408, into a through-hole formed within the casing 418, similarly to the description of the marker 410 above.

[0044] Referring now to FIG. 5, illustrated is a schematic view of a drill probe assembly 502 according to one or more aspects of the present disclosure. The flexible shaft 506 may be used to drill a through-hole in the casing 518, and/or may be used to drill a hole 526, as shown, such as by drilling the hole 526 through the sidewall 528 of the borehole 504, into the subterranean formation F. The flexible shaft 506 and, accordingly, the hole 526 are shown extending away from the drill probe assembly 502 at a substantially perpendicular angle relative to a central axis of the borehole 504. However, one of ordinary skill in the art will appreciate that the flexible shaft 506 may form the hole 526 at any angle with respect to the central axis of the borehole 504 without departing from the scope of the present disclosure. In FIG. 5, the flexible shaft 506 drills through the casing 518 and through the cement 522 disposed in the annulus 520 between the casing 518 and the sidewall of the borehole 528. One of ordinary skill in the art will appreciate that the drill probe assembly 502 may also be used for drilling a hole in a subterranean formation prior to the installation of the casing and/or the cement.

[0045] Referring now to FIG. 6, illustrated is a schematic view of a drill probe assembly 602 according to one or more aspects of the present disclosure. FIG. 6 shows the drill probe assembly 602 after the retraction of the flexible shaft 606 from the hole 626. The hole 626 may be drilled to a predetermined depth by the flexible shaft 606. Additionally, the angle of the hole 626 with respect to the central axis of the borehole 604 may vary. As shown in FIG. 6, cement 622 may be included within the annulus 620 formed between the casing 618 and the sidewall of the borehole 628. As such, the hole 626 may extend through the casing 618, the cement 622, and the subterranean formation F. The moveable carriage 614 is positioned such that the flexible shaft 606 is aligned with the aperture 616 and the hole 626. The plugging piston 608 may not be aligned with the hole 626.

[0046] Referring now to FIG. 7, illustrated is a schematic view of a drill probe assembly 702 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 702 with the plugging piston 708 and marker 710 may be aligned with the hole 726. As discussed above, the flexible shaft 706, the plugging piston 708, and/or the holder 712 may all be attached to and/or move with the moveable carriage 714, such as translate in unison with the moveable carriage. Therefore, the moveable carriage 714 may move to align the plugging piston 708, the marker 710 held by the holder 712, with the hole 726. The moveable carriage 714 may also move the flexible shaft 706 out of alignment with the hole 726 as the plugging piston 708 is moved into alignment with the hole 726. One of ordinary skill in the art will appreciate that other mechanisms, in addition or in alternative to the moveable carriage 714, may be used to align the flexible shaft 706, the plugging piston 708, and/or the marker 710 with the hole 726. For example, the flexible shaft 706 and the plugging piston 708 may move independently using separate moveable structures (not shown).

[0047] Referring now to FIG. 8, illustrated is a schematic view of a drill probe assembly 802 according to one or more aspects of the present disclosure. As shown in FIG. 8, the drill probe assembly 802 may be used to dispose the marker 810 in a hole 826. For example, a component, such as the plugging piston 808, may extend towards the hole 826, pushing the marker 810 from the holder 812. Those of ordinary skill in the art will appreciate that components other than the plugging piston 808 may be capable of inserting the marker 810 into the hole 826, such as, for example, the flexible shaft 806. Additionally, while FIG. 8 shows the plugging piston inserting the marker 810 only partially in the hole 826, those of ordinary skill in the art will appreciate that the plugging piston 808 may be configured to insert the marker 810 to any depth within the hole 826.

[0048] Referring now to FIG. 9, illustrated is a schematic view of a drill probe assembly 902 according to one or more aspects of the present disclosure. As shown in FIG. 9, the drill probe assembly 902 may be used to retract the component, such as the plugging piston 908 and/or the flexible shaft 906, that inserted the marker 910, at least partially, in the hole 926. In FIG. 9, the plugging piston 908 retracts after inserting the marker 910 to a particular depth in the hole 926. Although FIG. 9 shows that the plugging piston 908 inserts the marker 910 not to the full depth of the hole 926 formed in the subterranean formation F, as the drill probe assembly 902 may not be configured to insert the marker 910 into the full depth of the hole 926, drill probe assemblies in accordance with the present disclosure may be used to insert the marker fully into a final position in the subterranean formation, such as at the full depth of the hole 926. Therefore, assuming there is no need to seal the casing 918 at this time, once the marker 910 is located in a final position in the subterranean formation F, the drill probe assembly 902 may be re-positioned to a second location, such as a position to dispose another marker within the borehole, or, if the operation and use is complete, the drill probe assembly 902 and/or any tool attached thereto may be removed from the borehole 904. Additionally, although FIG. 9 shows casing 918 and cement 922 in the borehole 904, the borehole 904 may not include the casing 918 and cement 922, in which the hole 926 may not require a seal and the drill probe assembly 902 may be re-positioned to the second location.

[0049] Referring now to FIG. 10, illustrated is a schematic view of a drill probe assembly 1002 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 1002 may be used to align the flexible shaft 1006 with the marker 1010 in the hole 1026. The moveable carriage 1014 may move the plugging piston 1008 to allow the flexible shaft 1006 to be aligned with the marker 1010 and/or the hole 1026. As such, the flexible shaft 1006 and the plugging piston 1008 may both be attached to the moveable carriage 1014 and/or translate in unison with the moveable carriage 1014. However, the plugging piston 1008 and the flexible shaft 1006 may be attached to separate structures, allowing independent movement therebetween.

[0050] Referring now to FIG. 11, illustrated is a schematic view of a drill probe assembly 1102 according to one or more aspects of the present disclosure. In FIG. 11, the flexible shaft 1106 may be used to dispose, such as push, the marker 1110 in the hole 1126. As shown, as the plugging piston 1108 may not dispose the marker 1110 to a final depth, the flexible shaft 1106 may be used to push the marker 1110 deeper in the hole 1126 to a final depth. As such, the drill probe assembly 1102 may be used to dispose multiple markers 1110 in the hole 1126, if desired to have more than one marker 1110 within the hole 1126.

[0051] Referring now to FIG. 12, illustrated is a schematic view of a drill probe assembly 1202 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 1202 may be used to retract the flexible shaft 1206 from the hole 1226. Once the marker 1210 is located at a final depth, the flexible shaft 1206 may be removed from the hole 1226. As such, if the borehole 1204 does not have the casing 1218, the drill probe assembly 1202 may be re-positioned to a second location, such as to dispose another marker within the subterranean formation and/or remove the drill probe assembly from the borehole. If the borehole 1204 includes the casing 1218 and there is no need to seal the casing 1218, the drill probe assembly 1202 may also be re-positioned to a second location.

[0052] Referring now to FIG. 13, illustrated is a schematic view of a drill probe assembly 1302 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 1302 may be used to align the plugging piston 1308 with the hole 1326. As such, if the casing 1318 disposed in the borehole 1304 is to be sealed, the plugging piston 1308 may be re-aligned with the hole 1326. The plugging piston 1308 may be moved into alignment by moving the moveable carriage 1314. The casing plug 1330 may also be aligned with the plugging piston 1308 and the hole 1326. The casing plug 1330 may be moved into alignment by the holder 1312 after the insertion of the marker 1310 into the hole 1326. Those of ordinary skill in the art will appreciate that the holder 1312 may be loaded with an alternating sequence of markers 1310 and casing plugs 1330, such that a casing plug 1330 may be moved into alignment with the plugging piston 1308 after the insertion of each marker 1310. If the casing 1318 is not present or the casing 1318 is not to be sealed immediately after the placement of the marker 1310, the holder 1312 may be loaded with only markers 1310, such that a second marker 1310 may be aligned with the plugging piston 1308 after the first marker 1310 is inserted into the hole 1326. Those having ordinary skill in the art will also appreciate that other sequences may be used for the casing plugs and/or the markers within the holder without departing from the scope of the present disclosure.

[0053] Referring now to FIG. 14, illustrated is a schematic view of a drill probe assembly 1402 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 1402 may be used to plug the hole 1426 in the casing 1418 with a casing plug 1430. The plugging piston 1408 may dispose the casing plug 1430 in a through hole 1432 of the casing 1418, in which the through hole 1432 was drilled by the flexible shaft 1406 prior to or at the same time as the hole 1426. The casing plug 1430 may then be disposed in the through hole 1432 to seal the casing 1418.

[0054] Referring now to FIG. 15, illustrated is a schematic view of a drill probe assembly 1502 according to one or more aspects of the present disclosure. As shown, the drill probe assembly 1502 may be used to retract the component that disposed the casing plug 1530 in the through hole 1532 of the casing 1518. For example, after the placement of the casing plug 1530 in the through hole 1532, the plugging piston 1508 may be retracted. Once the plugging piston 1508 is retracted, the drill probe assembly 1502 may be re-positioned in the borehole 1504, such as to a second location within the borehole 1504, and/or removed from the borehole 1504.

[0055] Referring generally to FIGS. 4-15, the present disclosure may allow the drill probe assembly to be positioned and re-positioned to multiple locations within a borehole. The drill probe assembly may be loaded with multiple markers, and casing plugs if necessary, such that the drill probe assembly may be re-positioned in the borehole without needing to remove the drill probe assembly from the borehole. Once re-positioned to a second location, a second hole may be drilled through the sidewall of the borehole with the flexible shaft and a second marker may be inserted into the second hole. The steps used after re-positioning the drill probe assembly may follow one or more of the examples as shown above in reference to FIGS. 4-15.

[0056] Referring now to FIG. 16, illustrated is a schematic view of a marker 1630 according to one or more aspects of the present disclosure. The marker 1630 may have a similar structure to a casing plug, such as by having a similar size and/or similar shape to a casing plug. For example, the marker 1630 may comprise a capsule, cylindrical in shape, may have a conical or frustro-conical nose 1634, and/or may have a pushing surface 1636. The capsule may be provided with barbs or other structure configured to resist forces that may otherwise cause the marker to come out of the drilled hole. A marking element may be included in the capsule, such as by including the marking element disposed within the nose 1634 or the body of the marker 1630. For example, the marking element may include a radioactive element, such as a radioactive pellet, and/or may include any other element or material capable of being detected within a subterranean formation, such as detectable by a measuring tool. As such, a radioactive pellet may be 1 mm.sup.3 in volume and/or may be formed from a cesium isotope. Radioactive materials may allow for the marker to be detected many years after initially inserted in the subterranean formation.

[0057] The present disclosure may be used to place multiple markers in the subterranean formation along the length of a borehole. Measurements may be taken between a marker and a second location, in which the second location may include a second marker and/or may include any other known location (e.g., a surface location). An initial measurement of the distance between the marker and a second location may be taken after placing the marker in the subterranean formation. Later measurements of the distance between the marker and the second location may then be taken and compared to the initial measurement. The changes in distance and comparison of the measured distances may indicate geological changes in the subterranean formation, such as, for example, compaction, expansion, sliding, shifting, and/or any other movement within the subterranean formation. Indications of compaction in the subterranean formation may provide information about possible subsidence at the surface.

[0058] One or more methods of measuring the distance between the marker and a second location may be used. For example, one such method may include running a measurement tool down the borehole, in which the measurement tool has at least one detector, such as a gamma radiation detector. These detectors may detect the markers disposed in the subterranean formation and measurements may be taken between the markers. One of ordinary skill in the art will appreciate that other types of markers, measurement tools, and/or methods of measuring may be used without departing from the scope of the present disclosure.

[0059] Advantageously, the present disclosure may provide a method to place a marker in a borehole formed within a subterranean formation such that the depth of the marker is controlled. Controlling the depth of the marker in the hole may provide more accurate measurements. Another advantage of the present disclosure may be the ability to place markers in the subterranean formation via a borehole with or without casing and/or cement. Additionally, the present disclosure may allow for the sealing of the casing after the placing the marker in the subterranean formation. The present disclosure may also use equipment from the present assignee, such as the CHDT.TM. (Cased Hole Dynamics Tester), available from Schlumberger.RTM.. Another advantage of the present disclosure may be the lack of requiring explosives to place markers within a subterranean formation, as explosives are restricted and/or regulated in many locations around the world.

[0060] In view of all of the above and the figures, those skilled in the art should readily recognize that the present disclosure introduces a method comprising: positioning a drill probe assembly in a borehole extending into a subterranean formation; drilling a hole through a sidewall of the borehole with a flexible shaft of the drill probe assembly, the hole penetrating the subterranean formation; and disposing a marker in the hole. The drill probe assembly may comprise a plugging piston, wherein the plugging piston is used to dispose the marker, at least partially, in the hole. The method may further comprise pushing the marker in the hole with the flexible shaft. The method may further comprise: drilling a through hole into a casing disposed within the borehole with the flexible shaft; and disposing a casing plug in the through hole formed in the casing. The hole may be a first hole and the marker may be a first marker, wherein the method may further comprise: re-positioning the drill probe assembly in the borehole; drilling a second hole through a sidewall of the borehole with the flexible shaft, the second hole penetrating the subterranean formation; and inserting a second marker into the second hole. The drill probe assembly may comprise a moveable carriage, a plugging piston, and the flexible shaft, wherein the flexible shaft is configured to move with respect to the moveable carriage. The drill probe assembly may further comprise a casing plug and a holder, the holder configured to have the marker and the casing plug disposed therein. The casing may be disposed within the borehole and cement may be disposed, at least partially, within an annulus formed between the casing and the borehole. The marker may comprise a radioactive material. The method may further comprise comprising measuring a distance between the marker and a reference location. The measuring the distance between the marker and the reference location may comprise disposing a measurement tool within the borehole. The marker may comprise a radioactive material and the measurement tool comprises a gamma radiation detector. The hole may be a first hole, the marker may be a first marker, wherein the reference location may comprise a second marker disposed in a second hole, the second hole penetrating the subterranean formation. The distance may be a first distance, and the method may further comprise: measuring a second distance between the marker and the second location; and comparing the first distance and the second distance to each other.

[0061] The present disclosure also introduces an apparatus comprising: a drill probe assembly configured to be disposed within a borehole extending into a subterranean formation, the drill probe assembly comprising a flexible shaft and a marker; wherein the flexible shaft is configured to drill a hole through a sidewall of the borehole, the hole penetrating the subterranean formation; and wherein the drill probe assembly is configured to dispose the marker within the hole. The flexible shaft may be configured to dispose the marker, at least partially, within the hole. The drill probe assembly may further comprise a plugging piston and a casing plug, wherein the plugging piston is configured to dispose the plug within a through hole formed within casing. The plugging piston may be configured to dispose the marker, at least partially, within the hole. The drill probe assembly may further comprise a moveable carriage configured to move with respect to the subterranean formation. The flexible shaft and the plugging piston may be able to translate in unison with the movable carriage and may be configured to extend from the moveable carriage. The drill probe assembly may further comprise a holder, wherein the holder has the plug and the marker disposed therein. The marker may comprise a radioactive material.

[0062] The foregoing outlines feature several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

[0063] The Abstract at the end of this disclosure is provided to comply with 37 C.F.R. .sctn.1.72(b) to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

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