Through Casing Coring

Abstract

Devices and methods for obtaining core samples from a formation that surrounds a cased wellbore. A coring tool includes a casing cutter for cutting an opening in the casing and a coring device for obtaining a core sample from the formation.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to devices and methods for obtaining core samples from the sidewall of a cased wellbore. The device is also useful for obtaining cores from the sidewall of an openhole wellbore.

2. Description of the Related Art

Coring devices are more typically known for obtaining core samples from the uncased sidewall of a wellbore. The inventors have recognized that there might be an to advantage to evaluating certain formation zones after a well has been cased.

SUMMARY OF THE INVENTION

The invention provides devices and methods for obtaining core samples from the sidewall of a cased wellbore. In a described embodiment, a coring tool is provided includes an outer housing that encloses a plurality of bit boxes. The bit boxes are moveable within the housing so that they may be selectively aligned with an opening in the outer housing. In a particular embodiment, the bit boxes are contained within a carriage that is axially moveable within the outer housing between separate operational positions wherein the tools within the bit boxes are selectively aligned with a portion of the wellbore from which it is desired to obtain a core sample.

In certain embodiments, the housing contains a first bit box with a casing cutter having a casing cutting bit that is suitable for cutting through the surrounding casing and cement. The housing preferably also contains a second bit box with a coring device having a coring bit that is suitable for cutting and obtaining a core sample from the surrounding formation. Preferably also, the coring device can articulate or move angularly to separate the core sample from the formation. The separated core sample is preferably deposited into a coring tube or receptacle within the coring tool housing.

In particular embodiments, the coring tool contains a third bit box that includes a device for placement of a casing plug into the opening that was previously cut into the casing.

According to a further preferred feature of the invention, the carrier is rotatable to within the outer casing of the coring tool. An operator can rotate the carrier within the coring tool housing in order to obtain core samples from other angular locations within the wellbore. A coring tool in accordance with the present invention can preferably be disposed within a wellbore on wireline conveyance. Power and data communication with the coring tool can then be conducted via the wireline. In particular embodiments, the coring tool includes an electronic and power section that controls and provides power to the casing cutter device, the coring device and the hole plugging subassembly. In addition, the coring tool preferably includes a power transfer medium for movement of the carriage within the coring tool outer housing.

The invention provides methods for obtaining coring samples from cased wellbores. In exemplary operation, a coring tool is disposed into a cased wellbore to a depth or location at which it is desired to obtain one or more core samples. Stabilizers may be set within the wellbore to secure the coring tool in place within the wellbore. Thereafter, the carrier is axially moved within the outer housing of the coring tool so as to selectively align first the casing cutter device and then the coring device so that each of these tools can operate at a preselected location and a core sample is obtained. If desired, the carrier is then moved axially within the outer housing to align the hole plugging subassembly with the opening that was previously formed in the casing. The hole plugging subassembly is then operated to secure a plug within the opening in the casing. The devices and methods of the present invention allow for multiple cores to be obtained from multiple locations.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary cased wellbore with an exemplary coring tool disposed therein which is constructed in accordance with the present invention.

FIG. 2 is an enlarged side, cross-sectional view of portions of the coring tool shown in greater detail and being used to form an opening in the wellbore casing.

FIG. 3 is a side, cross-sectional view of the portions of the coring tool of FIG. 2, now in an operational configuration to obtain a core sample from surrounding formation.

FIG. 4 is a side, cross-sectional view of the portions of the coring tool shown in FIGS. 2 and 3, now in a configuration for plugging an opening previously created in the surrounding casing.

FIG. 5 is a detail view depicting a core sample being obtained by a coring bit.

FIG. 6 is a schematic axial cross-sectional view illustrating exemplary rotation of a bit box carrier within the coring tool outer housing.

FIG. 7 depicts an alternative embodiment for an exemplary coring arrangement wherein the coring tool is moved within the wellbore to reposition cutting, coring and plugging components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary wellbore 10 that has been drilled through the earth 12 from the surface (not shown). The wellbore 10 is surrounded by a formation 14 at a lo depth from which it is desired to obtain one or more sidewall core samples. The wellbore 10 is lined with a metallic casing 16 which has been secured in place with cement 18.

A coring tool 20 has been disposed within the wellbore 10 by wireline 22, in a manner known in the art. The coring tool 20 includes a generally cylindrical outer housing 24 that encloses the various components used to accomplish coring, as will be described. An opening 26 is formed in the outer housing 24. Stabilizers 28, of a type known in the art, have been extended radially outwardly from the coring tool 20 to secure it within the wellbore 10. Preferably, the stabilizers 28 maintain the coring tool 20 in proximity to one side of the wellbore 10.

FIG. 2 depicts interior components of an exemplary coring tool 20 as the coring tool 20 is being used to cut an opening in the casing 16 and cement 18 lining the wellbore 10. The coring tool 20 includes an electronics and power section, indicated schematically at 30. The electronics and power section 30 receives electrical power for the coring tool 20 via the wireline 22. The electronics and power section 30 may be electrically coupled to any of the components in the coring tool 20 requiring electrical power to operate. Also, the electronics and power section 30 may include any number of electrical components to facilitate operation of coring tool components. As depicted in FIG. 2, the electronics and power section 30 includes a processing system 32 having at least one information processor 34 of a type known in the art for actuation and control of the various components of the coring tool 20. The electronics and power section 30 also includes transmitter and receiver circuits 36 to convey information to surface and to receive information and commands from the surface via a wireline communication cable. Additionally, the electronics and power section 30 includes a memory unit 38 for storing programs and information processed by the processor 34 in order to operate the various components of the coring tool 20. The electronics and power section 30 may also include electronic components used for cooling, radiation hardening, vibration and impact protection, potting and other packaging details that do not require in-depth discussion as they are known in the art. A data bus 40 is used to communicate information between the various components of the electronics and power section 30 as well as externally to a power transfer medium 42.

The electronics and power section 30 is operably associated with a power transfer medium, schematically shown at 42. The power transfer medium 42 may be selected according to the particular power generating devices used to actuate and position bit boxes within the coring tool housing 24. The power transfer medium 42 may be a hydraulic fluid conduit where the power transfer device includes a hydraulic pump. The power transfer medium 42 may be an electrical conductor where the power generating device includes an electrical power generator. Alternatively, the power transfer medium 42 may be a drive shaft or gearbox where the power generating device includes a mechanical power output for extending a tool radially outwardly from the coring tool 20.

A bit box carriage 44 is retained within the coring tool 20 and is axially moveable and repositionable within the coring tool housing 24 between multiple operational positions. In order to ensure proper alignment and prevent undesirable radial movement of the bit box carriage 44, a guide rail or track (not shown), of a type known in the art, may be incorporated into the coring tool housing 24 along which the bit box carriage 44 can slidably move. One example of a suitable guide rail arrangement would be an opposing pair of rigid plates. Each of the plates would have an elongated slot formed therein, while the bit box carriage 44 would have complimentary lugs that would ride within these slots. However, other suitable guide rail or track arrangements could also be used to help ensure precision alignment and movement of the bit box carriage 44 within the housing 24. The bit box carriage 44 depicted in FIG. 2 contains two individual bit boxes: a casing cutter bit box 46 and a coring bit box 48. The bit boxes 46 and 48 are each adapted to orient and extend a cutting tool radially outwardly from the coring tool 20 through opening 26. In certain embodiments, the bit box carriage 44 also includes a hole plugging subassembly 50 that is located in a separate box 52 within the carriage 44. The bit box carriage 44 can be moved axially within the coring tool housing 24 by the power transfer medium 42, which in turn may be actuated and controlled by the processing system 32 in accordance with a preprogrammed scheme. In FIG. 2, the bit box carriage is oriented within the coring tool housing 24 such that the casing cutter bit box 46 is aligned with the opening 26 of the coring tool housing 24.

The casing cutter bit box 46 includes a casing cutter in the form of a casing cutting mill bit 54 that is mounted upon a rotary cutting device 56. The rotary cutting device 56 is capable of rotating the cutting mill bit 54 and extending it radially outwardly through the opening 26 and into cutting engagement with the casing 16 lining the wellbore 10. The casing cutting mill bit 54 is preferably a generally cylindrical cutter with an open center portion that is capable of forming a circular cut within the casing 16 and the cement 18. When the casing cutting mill bit 54 cuts through the casing 16 and cement 18, the cutaway portions will typically be retained within the open center portion of the bit 54 in this instance. Alternatively, the cutting mill bit 54 might be a drill tip type cutter which forms an opening in to the casing 16 and cement 18 in the manner of a rotary drill. In certain embodiments, the rotary cutting device 56 may also swivel to allow the cutting mill bit 54 to be rotated between a position wherein the bit 54 is facing away from the opening 26 (see phantom position 54a) and a position wherein the bit 54 is facing toward the opening 26 and can be extended toward the casing 16.

The coring bit box 48 is preferably located axially below the casing cutter box 46 within the chassis 44. Also, the coring bit box 48 preferably includes an opening 58 along its lower side so that captured cores can be released into a core tube 60 within the coring tool housing 24. The coring tool bit box 48 retains a coring device in the form of a coring bit 62 which is capable of cutting and capturing a core sample from the formation 14. Suitable coring bits for this purpose are described in U.S. Pat. No. 7,373,994 entitled “Self Cleaning Coring Bit” and issued to Tchakarov et al. This patent is owned by the assignee of the present application and is hereby incorporated by reference in its entirety. The coring bit 62 is mounted upon a rotary cutting device 64. The rotary cutting device 64 is capable of rotating the coring bit 62 and extending it radially outwardly through the opening 26 and into cutting engagement with the formation 14 to obtain a core sample. Additional details relating to the operation of rotary coring tools to obtain a core sample from a wellbore sidewall are described in U.S. Pat. No. 7,530,407 issued to Tchakarov et al. This patent is owned by the assignee of the present application and is hereby incorporated by reference in its entirety. Suitable rotary cutting devices for this purpose include the MaxCOR™ rotary sidewall coring system that is available commercially from Baker Hughes Incorporated of Houston, Tex.

The hole plugging subassembly 50 includes a magazine 66 which contains one or more circular plugs 68. Each of the plugs 68 is shaped and sized to close of an opening in the casing 16 that has been cut by the casing cutting mill bit 54. In addition, the hole plugging subassembly 50 includes an extendable piston assembly 70 that can urge the plugs 68 within the magazine 66 outwardly so that the outermost plug 68 is seated within such a milled opening.

The bit box carriage 44 is selectively moveable between axial operational positions within the housing 24 in order to position the carriage 44 to enable it to perform operations that will permit a core sample to be obtained from a cased wellbore 10 These positions are illustrated by FIGS. 2, 3 and 4. In FIG. 2, the carriage 44 is positioned in a first operational position so that the casing cutter bit box 46 is located proximate the opening 26 in the housing 24 to allow the casing cutting mill bit 54 to cut an opening in the casing 16 and cement 18 at a desired target position Once an opening is formed in the casing 16 and cement 18, the casing cutting mill bit 54 is withdrawn back into the coring tool outer housing 24. The bit box carriage 44 is then axially shifted by the power transfer medium 42 from the first operational position shown in FIG. 2 to a second operational position, as illustrated in FIG. 3.

When the coring tool 20 is in the second operational position shown in FIG. 4, the coring bit box 48 is generally aligned with the opening 26 in the coring tool housing 24. As depicted in FIG. 3, the rotary cutting device 64 rotates the coring bit 62 and extends the coring bit 62 outwardly through the opening 26 and into cutting engagement with the formation 14. As FIG. 5 depicts, a core sample 72 is formed as the coring bit 62 creates a circular cut 74 in the formation 14. Articulation or angular movement of the shaft 76 that retains the coring bit 62 (as illustrated at 78) will break off the core sample 72 from the lo formation 14. The core sample 72 can then be ejected into the core tube 60 The core sample 72 will be brought to the surface when the coring tool 10 is withdrawn from the wellbore 10.

FIG. 4 illustrates the coring tool 20 in a third operational configuration wherein the carriage 44 has been aligned by the power transfer medium 42 so that the box 52 is aligned with the opening 26 in the coring tool housing 24. The piston assembly 70 urges the stack of plugs 68 radially outwardly until the outermost plug 68 is seated into the opening 80 that was formed in the casing 18. The plug 68 is preferably secured within the opening 80 by an interference fit. It is noted that this step of plugging the opening 80 in the casing 18 is not always required. If the coring operation is being performed, for example, in a formation zone wherein production is already occurring through perforated casing 16, then it is unnecessary to plug the opening 80.

In particular embodiments of the present invention, the coring tool 20 is capable of obtaining multiple core samples from the wellbore 10. In addition, the coring tool 20 is preferably capable of plugging multiple openings 80 formed within the casing 16 of the wellbore 10. According to an exemplary embodiment, the carriage 44 is capable of axial rotation with respect to the outer housing 24 of the coring tool. A torsional motor 82 applies rotational force to the carriage 44 to rotate it angularly within the housing 24. FIG. 6 illustrates an embodiment for the coring tool 10 wherein there are multiple openings 26 in the outer housing 24. Rotation of the carriage 44 thereby allows the cutting tools 54, 62 to be angularly aligned with each of the openings 26a, 26b, 26c, or 26d. Although there are four openings 26a, 26b, 26c, 26d shown in FIG. 6, it should be understood that there may be more or fewer than four such openings. The carriage 44 may be rotated in the angular directions indicated by arrows 84 in FIG. 6. This feature permits the carriage 44 to be repositioned so that it can obtain further core samples.

If it is desired to obtain core samples from other depths or locations within the wellbore 10, the stabilizers 28 can be unset and the coring tool 20 then raised or lowered to another depth or location within the wellbore 10 from which it is desired to obtain further core samples. Thereafter, additional core samples can be obtained in the manner previously described.

According to an exemplary method of operation, the coring tool 20 is disposed into the wellbore 10 to a depth or location within the cased wellbore 10 from which it is desired to obtain one or more core samples 72. The stabilizers 28 are then set to secure the coring tool 20 in place within the wellbore 10. The carriage 44 is positioned in the first operational position depicted in FIG. 2. This may occur prior to running the coring tool 20 to its desired depth or afterward. The rotary cutting device 56 is actuated so that the casing cutting bit 54 cuts an opening 80 in the casing 16 of the wellbore 10. The carriage 44 is moved to the second operational position depicted in FIG. 3. The rotary cutting device 64 then operates the coring bit 62 to obtain a core sample 72 from the formation 14 that lies radially outside of the casing 16 and cement 18. The core sample 72 is then disposed into a core tube 60 or other core sample receptacle. The carriage 44 may then be moved to the third operational position depicted in FIG. 4. The hole plugging subassembly 50 is then actuated to close off the opening 80 in the casing 16. If desired, an operator can then rotate the carriage 44 within the outer housing 24 to align with other openings, such as 26b, 26c or 26d and obtain additional coring samples.

FIG. 7 illustrates an alternative arrangement for obtaining a core from a cased wellbore 10. An exemplary coring tool 90 is disposed within the wellbore 10 by wireline 22 suspension. The coring tool 90 includes an outer housing 92 which contains bit boxes 46, 48 which are preferably fixed against axial movement with respect to the outer housing 92. In addition, the coring tool 90 preferably contains a hole plugging subassembly 50. The outer housing 92 is provided with three lateral openings 94, 96, 98. Opening 94 is aligned with the casing cutter rotary cutting device 56 so that the casing cutting mill bit 54 may be extended radially outwardly through the opening 94. The mill bit 54 can cut an opening in the casing 16 when aligned with a target point 100 (shown in phantom in FIG. 7) within the wellbore 10. Opening 96 is aligned with the rotary cutting device 64 so that the coring bit 62 can be extended radially outwardly through the opening 96. The coring bit 62 can obtain a core sample, as described above, when the opening 96 is aligned with the target point 100. Opening 98 is aligned with the hole plugging subassembly 50. The hole plugging subassembly 50 can emplace a plug 68 within a previously-milled opening within the casing 16 when the opening 98 is aligned with the target point 100.

In operation, the coring tool 90 is moved axially upwardly and downwardly within the wellbore 10 via wireline manipulation, as illustrated by arrows 102 in order to align the appropriate lateral openings 94, 96 or 98 with the target position 100 in order to accomplish the tasks to obtain a core sample from the target position 100 of the wellbore 10. First, the coring tool 90 is positioned within the wellbore 10 so that the opening 94 is aligned with the target position 100. Reversible slips or anchors (not shown) of a type known in the art may be used to secure the coring tool 90 in this position. Thereafter, the rotary cutting device 56 is actuated to cut an opening in the casing 16. The coring tool 90 is then repositioned in the wellbore 10, moving the coring tool 90 with the wireline 22 until the opening 96 is aligned with the target position 100. Again, reversible slips or anchors may be used to secure the coring tool 90 in this position. The cutting device 64 is actuated so that the coring bit 62 extends through the opening in the casing 16 to obtain a core sample from the surrounding formation. Next, the coring tool 90 is moved by wireline 22 until the opening 98 is aligned with the target position 100. Next, the hole plugging subassembly 50 is actuated to emplace a plug 68 within the previously-formed opening in the casing 16. Thereafter, one can remove the coring tool 90 from the wellbore 10 via wireline retrieval.

Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.

Claims

1. A coring tool for obtaining a core sample from a formation surrounding a cased wellbore, the coring tool comprising: a casing cutter for cutting an opening in casing lining the wellbore; anda coring device for obtaining a core sample from the formation.

2. The coring tool of claim 1 further comprising a hole plugging subassembly to close off said opening in the casing lining the wellbore.

3. The coring tool of claim 1 wherein: the coring tool has an outer housing having an opening therein; andthe casing cutter and the coring device are retained within a carrier that is moveable within the outer housing between a first operational position wherein the casing cutter is aligned with the opening in the coring tool housing and a second operational position wherein the coring device is aligned with the opening in the coring tool housing.

4. The coring tool of claim 3 wherein the carrier is rotatable within the casing tool housing.

5. The coring tool of claim 1 wherein the casing cutter comprises a casing cutting mill bit that is mounted upon a rotary cutting device.

6. The coring tool of claim 1 wherein the coring device comprises a coring bit that is mounted upon a rotary cutting device.

7. The coring tool of claim 1 wherein: the coring tool is positioned by wireline manipulation to align the casing cutter with a target position within the wellbore from which it is desired to obtain a core sample; andthe coring tool is then repositioned by wireline manipulation to align the coring device with the target position to obtain a coring sample from the target position.

8. A coring tool for obtaining a core sample from a formation surrounding a cased wellbore, the coring tool comprising: a casing cutter for cutting an opening in casing lining the wellbore;a coring device for obtaining a core sample from the formation; anda hole plugging subassembly to close off said opening in the casing lining the wellbore.

9. The coring tool of claim 8 wherein: the coring tool has an outer housing having an opening therein; andthe casing cutter and the coring device are retained within a carrier that is moveable within the outer housing between a first operational position wherein the casing cutter is aligned with the opening in the coring tool housing and a second operational position wherein the coring device is aligned with the opening in the coring tool housing.

10. The coring tool of claim 9 wherein the carrier is rotatable within the casing tool housing.

11. The coring tool of claim 8 wherein the casing cutter comprises a casing cutting mill bit that is mounted upon a rotary cutting device.

12. The coring tool of claim 8 wherein the coring device comprises a coring bit that is mounted upon a rotary cutting device.

13. A method of obtaining a core sample from a formation surrounding a cased wellbore, the method comprising the steps of: forming an opening in casing lining the wellbore; andobtaining a core sample from the formation.

14. The method of claim 13 further comprising the step of closing o the opening in the casing.

15. The method of claim 14 wherein the step of closing off the opening in the casing further comprises actuating a hole plugging subassembly to emplace a plug in the opening.

16. The method of claim 13 further comprising disposing the core sample in a core sample receptacle within the coring tool.

17. The method of claim 13 wherein the step of forming an opening in the casing comprises rotating a casing cutting bit to form a circular cut within the casing.

18. The method of claim 13 wherein the step of obtaining a core sample comprises rotating a coring bit to form a cylindrical core sample and separating the core sample from the formation.

19. The method of claim 13 wherein: the step of forming an opening in casing lining the wellbore further comprises locating the casing cutter to be aligned with a target position from which it is desired to obtain a core sample and actuating the casing cutter to cut an opening in the casing; andthe step of obtaining a core sample from the formation further comprises locating the coring device to be aligned with the target position and actuating the coring device to obtain a core sample from the target position.

20. The method of claim 19 wherein the coring device is located to be aligned with the target position by moving a bit box carriage within an outer housing of the coring tool.

21. The method of claim 19 wherein the coring device is located to be aligned with the target position by moving an outer housing containing the coring device within the wellbore.