WO2025224475A1

WO2025224475A1 - Pipe string disconnect

Info

Publication number: WO2025224475A1
Application number: PCT/IB2024/053896
Authority: WO
Inventors: Rafael VILLA DE SANTANA; David Stephenson
Original assignee: Deep Casing Tools Ltd
Current assignee: Deep Casing Tools Ltd
Priority date: 2024-04-22
Filing date: 2024-04-22
Publication date: 2025-10-30
Anticipated expiration: 2026-10-22

Abstract

A string disconnect for a pipe string has a top sub (12) comprising a sub body (12A) having a threaded connection at each end and a through bore. The top sub has a piston (16) having a ball seat (16A) at one end and an elongated slot at another end disposed in the bore. The piston is held at a top end of the top sub by a biasing device (18) or restraint, and is rotationally locked to the top sub. The slot subtends an angle to a longitudinal axis of the piston. A bottom sub comprises a sub body (14A) having a threaded connection at each end and a release pin (20) extending inwardly from a through bore in the bottom sub and rotationally fixed to the bottom sub. Movement of the piston toward the bottom sub engages the slot (16D) with the release pin (18) to induce torque between the top sub and the bottom sub.

Description

PIPE STRING DISCONNECT

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

[0003] Not Applicable.

BACKGROUND

[0004] This disclosure relates to the field of pipes used in construction and servicing of underground wells. More particularly, the present disclosure relates to devices to disconnect one segment of a pipe “string” in a well from another segment, which may have become stuck in the well.

[0005] String disconnects are known in the oil and gas industry in well construction and servicing for use in well pipe assemblies (“strings”) to provide a point of separation at the location of the string disconnect. String disconnects are used in a variety of circumstances, including fishing operations and during normal operations to allow the majority of the string to be recovered should some element lower on the string become stuck.

[0006] String disconnects when used in well construction are often run just above an annular seal (“packer”), so that the greatest number of tools can be removed from the well. Other string disconnects are run below a packer. The applicability of a string disconnect to either of these circumstances depends on the order of operations used to disconnect the string disconnect and to set the packer. If a string disconnect below a packer disconnects using the same order of operations as setting the packer, then it will not be known which tool received the operation.

[0007] When used in well drilling as part of a drill string, string disconnects known in the art may require many rotations of the drill string, often in combination with downward force, to transmit a high level of torque along the drill string to thereby separate the string at the string disconnect. Certain components of the string disconnect are normally connected by a threaded section and are separated by reverse rotation of the drill string. The string disconnect threaded section typically is designed to unscrew at lower torque than other parts of the drill string. Because torque often does not transmit well along the drill string, many rotations are required, and the string itself can be put under large amounts of force. This can damage the drill string and takes time to accomplish. Further, such low torque threaded connections may increase risk of inadvertent disconnection in the event of stick slip motion of the drill string in certain drilling conditions.

[0008] US Patent Application Publication No. 2007/0261889 Al filed by De Clute- Melancon discloses a type of string disconnect that does not require rotation of the pipe string to uncouple one string segment from another. The disclosed disconnect has internal components that may not provide full load ratings for a comparably sized threaded connection (“tool joint”) as may meet standards set by the American Petroleum Institute, Washington, DC (“API Standards”).

[0009] Another string disconnect method is disclosed in US Patent Application Publication No. 2007/0030156 filed by Churchill. The disclosed string disconnect method comprises reducing the load bearing cross-sectional area of the neck of a connection. The reduction in the area of the neck may be achieved using a precisely located flow-actuated cutter. The cutter may be pumped into the string to land on a seat above the connection. A bypass valve may be provided below the connection to facilitate fluid circulation. The disclosed method requires the use of abrasive cutting action on the interior of the drill string, which may itself increase risk of inadvertent disconnection or other drill string failure.

[0010] Thus, there is a need in the art for a way to disconnect tools from a pipe string, or to separate two parts of a pipe string, without the need to perform rotations of the pipe string to release a threaded connection, while maintaining full tool joint load ratings such as to API Standards.

SUMMARY

[0011] One aspect of the present disclosure is a string disconnect for use in a pipe string. A string disconnect according to this aspect has a top sub comprising a top sub body having a threaded connection at each longitudinal end and a through bore, the top sub has a piston having a ball seat at one end and an elongated slot at another end disposed in the through bore. The piston is axially urged to a top end of the top sub by a biasing device, or is held in place by a restraint, and is rotationally locked to the top sub. The at least one elongated slot subtends an angle with respect to a longitudinal axis of the piston. A bottom sub comprises a bottom sub body having a threaded connection at each longitudinal end and at least one release pin extending inwardly from a through bore in the bottom sub and rotationally fixed to the bottom sub body. Movement of the piston toward the bottom sub engages the at least one slot with the at least one release pin to induce torque between the top sub and the bottom sub.

[0012] In some embodiments, the biasing device comprises a spring.

[0013] In some embodiments, the restraint comprises a shear pin.

[0014] In some embodiments, the piston comprises splines on an exterior surface and the top sub body comprises corresponding splines on an interior surface of the through bore therein.

[0015] In some embodiments, the at least one release pin is disposed in a retaining sleeve inserted into a through bore in the bottom sub body, the retaining sleeve being rotationally locked to the bottom sub body.

[0016] Some embodiments further comprise splines on at least one of the retaining sleeve or the through bore in the bottom sub body to effect the rotational locking.

[0017] A method according to another aspect of the present disclosure includes pumping a ball or dart into a string disconnect as in the previous aspect of the disclosure. The string disconnect has a top sub comprising a top sub body having a threaded connection at each longitudinal end and a through bore. An upper part of the pipe string is connected to one end of the top sub. The top sub has a piston having a ball seat at one end and an elongated slot at another end disposed in the through bore. The piston is axially urged to a top end of the top sub by a biasing device, or held in place by a restraint, and is rotationally locked to the top sub. The at least one elongated slot subtends an angle with respect to a longitudinal axis of the piston. A bottom sub comprises a bottom sub body having a threaded connection at each longitudinal end and at least one release pin extending inwardly from a through bore in the bottom sub and rotationally fixed to the bottom sub body. Movement of the piston toward the bottom sub engages the at least one slot with the at least one release pin to induce torque between the top sub and the bottom sub. A lower part of the pipe string is connected to the bottom sub. The method includes continuing pumping after the ball or dart engages the ball seat in the string disconnect so as to move the piston in the string disconnect to engage and apply torque between the top sub and bottom sub of the string disconnect to unthread the top sub from the bottom sub. The pressure is released to disengage the piston from the release pin(s) in the bottom sub, and the upper part of the pipe string is fully decoupled from the lower part by reverse rotating the upper part of the pipe string.

[0018] Other aspects and possible advantages will be apparent from the description and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 shows a cross section of an example implementation of a string disconnect according to the present disclosure.

[0020] FIG. 2 shows an enlarged cross section of part of the string disconnect of FIG. 1.

[0021] FIG. 3 shows an oblique view of the piston part of the string disconnect of FIG. 1.

[0022] FIG. 4 shows a cross section at a first position along the length of the string disconnect of FIG. 1 to illustrate splines on the piston and on an inner wall of an upper sub portion of the string disconnect. [0023] FIG. 5 shows a cross section at a second position along the length to illustrate engagement of slots on an end of the piston with pins disposed within a bottom sub portion of the string disconnect.

[0024] FIG. 6 shows a cross section at a third position along the length to illustrate a pin retaining sleeve disposed in the bottom sub.

[0025] FIG. 7 shows a pipe string in a well having a string disconnect according to the present disclosure.

DETAILED DESCRIPTION

[0026] FIG. 1 shows a cross section of an example implementation of a string disconnect 10 according to the present disclosure that may be connected within a pipe string such as a drill string to be further explained below. The term “pipe string” generally refers to a pipe that is assembled from pipe segments coupled end to end. The coupling may be by way of threaded connectors, and such pipe segment and threaded connectors may be required to meet industry standards for performance, such as those provided by the American Petroleum Institute (API) as explained in the Background section herein. The string disconnect 10 may comprise a top sub 12 threadedly connected to a bottom sub 14. “Top” and “bottom” as used herein refer to the relative positions along a pipe string used in an underground well, wherein the top end of the pipe string is understood to be proximate the surface end of the well, and the bottom end of the pipe string is understood to be proximate the axial end of the well in underground formations. The top sub 12 may comprise a sub body 12A having a first threaded connection 12B at one longitudinal end and a second threaded connection 12C at the opposed longitudinal end. The threaded connections 12B, 12C may be, for example, any type of threaded connection known to be used in connecting segments end to end of a pipe string used in well construction operations. Such connections 12B, 12C may have dimensions and thread parameters made according to API Standards (see the Background section herein) for such connections when used in well construction. The sub body 12A may likewise have dimensions and be made from materials according to API Standards. The top threaded connection 12B may in some implementations be a female (box) connection and the bottom threaded connection 12C may be a male (pin) connection to enable connecting the string disconnect 10 into a drill string in the manner of any other ordinary well construction tool. The bottom sub 14 may comprise a sub body 14A and corresponding threaded connections 14B, 14C to those on the top sub 12. The top sub 12 and the bottom sub 14 may be threadedly coupled to each other to the same torque as any similarly dimensioned and rated threaded connection used in a drill string (not shown).

[0027] The string disconnect 10 has internal features, to be explained in more detail below, to enable unthreading of the bottom sub 14 from the top sub 12 by pumping a ball, dart or other sealing device (not shown) into the string disconnect 10 and increasing fluid pressure on the interior of the pipe string to effect unthreading. The components that effect the unthreading will be explained in more detail below.

[0028] A disconnect piston 16 may be disposed in a through bore 12C in the upper sub body 12A. The disconnect piston 16 may be urged upwardly within the through bore by a spring 18 resting on a spring seat 12D within the through bore 12C at one end and at the other end against a ball seat 16A at such longitudinal end. The disconnect piston 16 may have splines (FIG. 3) on its exterior surface (see FIG. 4) to engage corresponding splines in the through bore 12C. Thus, the disconnect piston 16 is prevented from rotating with respect to the top sub body 12 A. The opposed longitudinal end of the disconnect piston 16 may comprise one or more longitudinally extending, elongated slots 16D (also see FIG. 3). The one or more slots 16D subtend a non-zero selected oblique angle with respect to the longitudinal axis A of the top sub body 12 A, the bottom sub body 14A and the disconnect piston 16. The disconnect piston 16 may be urged in a direction toward the top of the pipe string (not shown) and away from the bottom sub 14 by a biasing device 18 such as a spiring (e.g., a coil spring). In some embodiments, the disconnect piston 16 may be held in place by a shear pin 18A, shear ring or other device which may fail at a selected axial force exerted by the disconnect piston 16 on application of sufficient fluid pressure. In general, whether a spring, shear pin, shear ring or other device is used to hold the disconnect piston 16, any of the foregoing may act as a restraint to axial movement of the disconnect piston 16 until sufficient fluid pressure is exerted against the disconnect piston 16 when an object such as a ball or dart is disposed in the ball seat 16A to stop fluid flow through the disconnect piston 16.

[0029] The bottom sub body 14A may also comprise a through bore 14C within which may be disposed a retaining sleeve 22. The retaining sleeve 22 may comprise external splines (FIG. 6) to rotationally lock the retaining sleeve 22 to the bottom sub body 14A. The retaining sleeve 22 may have therein one or more release pins 20 extending radially inwardly, whereby the release pins 20 are effectively rotationally locked to the bottom sub body 14A.

[0030] FIG. 2 shows an enlarged view of the upper longitudinal end of the disconnect piston 16. The ball seat 16A may be tapered, such that when a ball or dart of suitable diameter is inserted into the pipe string (not shown) above the string disconnect (10 in FIG. 1), it becomes lodged in the ball seat 16A and effectively closes the through bore 12C to fluid flow. In such instance, further fluid pumping through the pipe string (not shown) and thus into the top sub body 12A will increase fluid pressure and cause the disconnect piston 16 to act against the spring 18. The disconnect piston 16 will thereby be urged axially and will move in the direction of the bottom sub (14 in FIG. 1). When the disconnect piston 16 is assembled within the top sub body 12A, the disconnect piston 16 may be urged axially against the spring 18 to enable insertion of a retainer 17, such as an internal snap ring. The ball seat end of the piston 16 may be sealed with reference to the through bore 12C by an o-ring or other seal enabling sealed longitudinal movement of the disconnect piston 16. In some implementations when a dart is used, the dart may be hollow to enable continuous circulation, e.g., to commence pumping cement immediately after disconnecting the string disconnect (10 in FIG. 1).

[0031] FIG. 3 shows an oblique view of the disconnect piston 16 to illustrate some of the functional features. The splines explained with reference to FIG. 1 are shown at 16C. The one or more elongated slots are shown at 16D. In the present example implementation there may be three, circumferentially spaced apart slots 16D extending longitudinally along the disconnect piston 16 from its lower longitudinal end. Because the slots 16D as explained above subtend an oblique angle, or expressed another way, traverse a helical path with respect to the longitudinal axis (A in FIG. 1), the circumferential position of the slots 16D with respect to a fixed longitudinal position (e.g., in the bottom sub body) will change as the disconnect piston moves longitudinally. As will be explained in more detail below, such circumferential movement will cause torque to be induced between the top sub body (12A in FIG. 1) and the bottom sub body (14A in FIG. 1), thereby releasing the threaded coupling between the top sub and the bottom sub.

[0032] FIG. 4 shows a first cross section of the top sub (12 in FIG. 1), the position of which is shown at 4- 4’ in FIG. 1, to illustrate engagement of the splines 16C on the exterior of the disconnect piston 16 with corresponding splines 12A1 on the inner wall of the top sub body 12A.

[0033] A second cross section, the position of which is shown at 5 - 5’ in FIG. 1 is shown in FIG. 5 to illustrate interaction between the slots 16D on the disconnect piston (16 in FIG. 1) and the one or more release pins 20 explained above. The release pins 20 may be disposed within the retaining sleeve 22, which as explained with reference to FIG. 1 may be inserted into the through bore (14D in FIG. 1) in the bottom sub body 14A to facilitate assembly and to avoid the need for any transverse bores within the bottom sub body 14. The foregoing will avoid creating structurally weak places in the bottom sub body 14 A.

[0034] FIG. 6 shows another cross section, the position of which is shown at 6 - 6’ in FIG. 1 to illustrate the retaining sleeve 22, the release pins 20 and how the retaining sleeve 22 may be rotationally locked to the bottom sub body 14 A. In the present example implementation, the interior surface of the bottom sub body 14A may comprise splines 24, and one or more locking keys 26 may hold the retaining sleeve 22 rotationally within the bottom sub body 14A.

[0035] Assembly and use of the string disconnect, and referring once again to FIG. 1, may be performed as follows. The release pins 20 may be assembled to the retaining sleeve 22 as well as the rotational locking keys 26, and the assembled retaining sleeve 22 may be inserted into the through bore 14C in the bottom sub body 14A. The retaining sleeve 22 may be locked in place using any suitable device, e.g., a snap ring 22A. The top sub body 12A may then be threadedly connected to the bottom sub body 14A and torqued to specification. The disconnect piston 16 and the spring 18 may be inserted into the through bore 12C in the top sub body 12A and in so doing, the disconnect piston 16 may be rotationally oriented such that the one or more slots 16D will rotationally correspond to the orientation of the one or more release pins 20. Such rotational orientation may be obtained by suitable engagement of the splines (see FIG. 4). The disconnect piston 16 may then be locked in place longitudinally by inserting the snap ring (17 in FIG. 2) into its place in the through bore 12C.

[0036] FIG. 7 shows schematically an arrangement of a string disconnect 10 according to the present disclosure disposed at a selected position along a pipe string 102, such as a drill string or workover string. The pipe string 102 is suspended in a subsurface well 104 from hoisting equipment (not shown separately) in a derrick 101 forming part of a drilling or workover unit 100. An upper part of the pipe string 102A may be suspended by the drilling or workover unit 100 and connected at its upper end, e.g., to a top drive 103 which can rotate the pipe string 102 and form hydraulic connection to a fluid (mud) pump 105 to pump fluid such as drilling mud through the pipe string 102. The opposed (lower) end of the upper part 102A of the pipe string 102 is coupled to the top sub (12 in FIG. 1) of the string disconnect 10. A lower part of the pipe string 102A is connected at one end to the bottom sub (14 in FIG. 1) of the string disconnect 10. The bottom end of the lower part 102B may be connected to various drilling tools, including, e.g., a drill bit 107. The foregoing parts of the arrangement in FIG. 7 will be referred to in explaining below how to operate the string disconnect 10.

[0037] To operate the string disconnect 10, the well operator may perform the following acts. The well operator may insert a ball or dart (106 in FIG. 7) into the pipe string (102 in FIG. 7). The ball or dart (106 in FIG. 7) could be shearable to enable inducing a certain pressure inside the pipe string (102 in FIG. 7), above which the ball or dart will fail and be pumped through the disconnect piston 16. Fluid pumping (e.g., using the mud pump 105 in FIG. 7) may resume until the ball or dart (106 in FIG. 7) lands in the ball seat 16A. Continued fluid pumping will urge the disconnect piston 16 longitudinally such that the slots 16D induce torque between the top sub body 12A and the bottom sub body 14 A. The well operator may maintain a predetermined unthreading (e.g., counterclockwise) torque on the pipe string (102 in FIG. 7, using e.g., top drive 103) to help identify when sufficient unthreading of the top sub 12 from the bottom sub 14 has taken place by reason of the interaction between the slots 16C and the release pins 20.

[0038] The subtended angle of the slots 16 creates a wedge force effect that allow enough torque to back-off the connection. The operator may then bleed off the fluid pressure in the pipe string (either by shearing the ball/dart, or simply releasing pressure at the surface) which will cause the spring 18 to urge the disconnect piston 16 away from the bottom sub 14, thereby disengaging the release pin(s) 20 and the slots 16D. The well operator may then counter rotate the pipe string one full turn and recognize that the pipe string down to the top sub 12 is free from the bottom sub 14. The well operator may then pump the shearable ball or dart off the ball seat 16A into a catcher (not shown) or finish unthreading and pump cement to plug the well so as to allow for a well sidetrack if desired.

[0039] A string disconnect and method according to the present disclosure may provide full pipe string mechanical property rated specifications, while avoiding use of chemical or explosive cutters to release part of the pipe string. While certain example implementations are described with reference to drill strings and used in connection with underground well drilling, the scope of the present disclosure is not limited to well drilling or drill strings but may be applicable to other types of pipe strings.

[0040] In light of the principles and example embodiments described and illustrated herein, it will be recognized that the example embodiments can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific embodiments, but other configurations are also contemplated. In particular, even though expressions such as in “an embodiment," or the like are used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the disclosure to particular embodiment configurations. As used herein, these terms may reference the same or different embodiments that are combinable into other embodiments. As a rule, any embodiment referenced herein is freely combinable with any one or more of the other embodiments referenced herein, and any number of features of different embodiments are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMS What is claimed is:

1. A string disconnect for inclusion in a pipe string, comprising: a top sub comprising a top sub body having a threaded connection at each longitudinal end, the top sub comprising a through bore, the top sub comprising a piston having a ball seat at one end and at least one elongated slot at another end disposed in the through bore, the piston being axially urged to a top end of the top sub body by a biasing device or held in place by a restraint, the piston being rotationally locked to the top sub body, the at least one elongated slot subtending an angle with respect to a longitudinal axis of the piston; and a bottom sub comprising a bottom sub body having a threaded connection at each longitudinal end, the bottom sub comprising at least one release pin extending inwardly from a through bore in the bottom sub body and rotationally fixed to the bottom sub body; wherein movement of the piston toward the bottom sub engages the at least one slot with the at least one release pin to induce torque between the top sub body and the bottom sub body.

2. The string disconnect of claim 1 wherein the biasing device comprises a spring.

3. The string disconnect of claim 1 wherein the restraint comprises a shear pin.

4. The string disconnect of claim 1 wherein the piston comprises splines on an exterior surface and the top sub body comprises corresponding splines on an interior surface of the through bore therein.

5. The string disconnect of claim 1 wherein the at least one release pin is disposed in a retaining sleeve inserted into a through bore in the bottom sub body, the retaining sleeve being rotationally locked to the bottom sub body.

6. The string disconnect of claim 5 further comprising splines on at least one of the retaining sleeve or the through bore in the bottom sub body to effect the rotational locking.

7. A method for disconnecting an upper part of a pipe string from a lower part of the pipe string using a string disconnect, the string disconnect comprising a top sub connected to the upper part, the top sub comprising a top sub body having a threaded connection at each longitudinal end, the top sub comprising a through bore, the top sub comprising a piston having a ball seat at one end and at least one elongated slot at another end disposed in the through bore, the piston being axially urged to a top end of the top sub body by a biasing device or held in place by a restraint, the piston being rotationally locked to the top sub body, the at least one elongated slot subtending an angle with respect to a longitudinal axis of the piston; and a bottom sub connected to the lower part, the bottom sub comprising a bottom sub body having a threaded connection at each longitudinal end, the bottom sub comprising at least one release pin extending inwardly from a through bore in the bottom sub body and rotationally fixed to the bottom sub body, the method comprising: pumping a ball or dart through the upper part until it contacts the ball seat; continuing pumping fluid into the upper part to increase pressure therein and to cause movement of the piston toward the bottom sub to engage the at least one slot with the at least one release pin to induce torque between the top sub body and the bottom sub body; rotating the upper part counter to a thread engagement direction to confirm release of the top sub from the bottom sub; releasing fluid pressure in the upper part; and unthreading the top sub from the bottom sub and removing the upper part from a subsurface well.

8. The method of claim 7 wherein the releasing fluid pressure comprises continuing the pumping fluid until the ball or dart shears and passes through the ball seat.

9. The method of claim 7 wherein the biasing device comprises a spring.

10. The method of claim 7 wherein the restraint comprises a shear pin.

11. The method of claim 7 wherein the piston comprises splines on an exterior surface and the top sub body comprises corresponding splines on an interior surface of the through bore therein.

12. The method of claim 7 wherein the at least one release pin is disposed in a retaining sleeve inserted into a through bore in the bottom sub body, the retaining sleeve being rotationally locked to the bottom sub body.

13. The method of claim 12 wherein the string disconnect further comprises splines on at least one of the retaining sleeve or the through bore in the bottom sub body to effect the rotational locking.