Downhole disconnect

Abstract

A tool assembly configured to connect to a downhole end of a wellbore tubing string includes an upper sleeve and a lower sleeve and defines a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly. The lower sleeve contacts the upper sleeve at an interface between a surface of the upper sleeve and a surface of the lower sleeve. The interface is dimensioned for an interference fit that at least partially fastens the lower sleeve to the upper sleeve. The interference fit is unseated, to thereby unfasten the lower sleeve from the upper sleeve, by application of one or both of (i) a specified tensile force along a central axis of the tool and (ii) a specified hydraulic pressure to the interface.

Description

TECHNICAL FIELD

[0001] This disclosure relates to a disconnect assembly for a tubing string or other apparatus used in wellbore operations.BACKGROUND

[0002] In wellbore operations, downhole disconnect tools allow for a lower section of a wellbore apparatus to be parted from an upper section of the wellbore apparatus. For example, in drilling operations, a disconnect can provide a joint that can reliably disconnect a bottom-hole assembly (BHA) from the drill string, should the need arise; for example, if the BHA becomes stuck. The drill string can be retrieved from the wellbore and appropriate measures can be taken to fish or retrieve the BHA.SUMMARY

[0003] Certain aspects of the present disclosure encompass tool assembly configured to connect to a downhole end of a wellbore tubing string. The tool assembly includes an upper sleeve and a lower sleeve and defines a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly. The lower sleeve contacts the upper sleeve at an interface between a surface of the upper sleeve and a surface of the lower sleeve. The interface is dimensioned for an interference fit that (a) at least partially fastens the lower sleeve to the upper sleeve and (b) is unseated, to thereby unfasten the lower sleeve from the upper sleeve, by application of one or both of (i) a specified tensile force along a central axis of the tool and (ii) a specified hydraulic pressure to the interface.

[0004] Certain aspects of the present disclosure encompass a system for well operations. The system includes a tubing string disposed in a wellbore and a tool assembly configured connected to a downhole end of the tubing string, the tool assembly that defines a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool. The tool assembly includes an upper sleeve and a lower sleeve and defines a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly. The lower sleeve contacts the upper sleeve at an interface between a surface of the upper sleeve and a surface of the lower sleeve. The interface is dimensioned for an interference fit that (a) at least partially fastens the lower sleeve to the upper sleeve and (b) is unseated, to thereby unfasten the lower sleeve from the upper sleeve, by application of one or both of (i) a specified tensile force along a central axis of the tool and (ii) a specified hydraulic pressure to the interface.

[0005] Certain aspects of the present disclosure encompass a method for well operations. The method includes supporting a lower sleeve of a tool assembly from an upper sleeve of the tool assembly while the tool assembly is subject to a tensile force less than a specified tensile force. The supporting is at least in part by a fastening of the lower sleeve to the upper sleeve by an interference fit at an interface between a surface of the upper sleeve contacting a surface or the lower sleeve. The tool assembly defines a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly. The method further includes unfastening the lower sleeve from the upper sleeve by an unseating of the interference fit, the unseating in response to application of one or both of (i) the specified tensile force along a central axis of the tool and (ii) a specified hydraulic pressure to the interface.

[0006] The above aspects can include some, none, or all of the following features.

[0007] The interference fit can be configured to be unseated by the application of both the specified tensile force and the specified hydraulic pressure, and to, prior to the application of the specified hydraulic pressure, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

[0008] The interference fit can be configured to, prior to application of a torsional force about the central axis of the tool, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

[0009] The tool assembly can include a fluid passageway fluidically connecting a fluid volume to the interface, the fluid passageway and the interface configured to, when the tool assembly is connected to the downhole end of the tubing string and the tubing string is disposed within the wellbore, permit, in response to the application of the specified hydraulic pressure, a passing of fluid through the fluid passageway into the interface to loosen the interference fit.

[0010] The tool assembly bore can at least partially define the fluid volume, the fluid passageway can fluidically connect the tool assembly bore to the interface, and the application of the specified hydraulic pressure can be by increasing a fluid pressure within the tool assembly bore.

[0011] The fluid volume can be within the tool assembly and is at least partially defined by a piston, and the application of the specified hydraulic pressure can be by application of a force applied to the piston thereby increasing a fluid pressure of the fluid volume. The fluid volume can be an annular volume exterior of the tool.

[0012] The central axis of the tool assembly can be parallel with an axis of the tubing string center bore. The central axis of the tool assembly can be parallel with an axis of the tool assembly bore.

[0013] Other aspects and features will be apparent from the following drawings and detailed description.BRIEF DESCRIPTION OF DRAWINGS

[0014] FIGS. 1A-1B are schematic illustrations of a wellbore system in accordance with the concepts herein.

[0015] FIG. 2 is a schematic half cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.

[0016] FIG. 3A is a schematic half cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.

[0017] FIG. 3B is a schematic quarter cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.

[0018] FIG. 3C is a schematic half cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.

[0019] FIGS. 4A-4D are schematic half cross-sectional illustrations of a disconnect tool assembly and system in accordance with the concepts herein.

[0020] FIG. 5 is a schematic half cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.

[0021] FIGS. 6A-6B are schematic half cross-sectional illustrations of a disconnect tool assembly and system in accordance with the concepts herein.

[0022] FIGS. 7A-7C are schematic half cross-sectional illustrations of a disconnect tool assembly and system in accordance with the concepts herein.

[0023] FIG. 8 is a schematic half cross-sectional illustration of a disconnect tool assembly and system in accordance with the concepts herein.DETAILED DESCRIPTION

[0024] Disconnect devices are typically used to separate a bottom hole assembly (BHA) from a drill string if, for example, the BHA becomes stuck. The geometries and internal mechanisms of conventional release tools mechanisms can cause pressure drop across the tool and inhibit the flow to a less than desirable rate. Such flow rate inhibition can be further exacerbated by check valves installed to maintain well control after disconnect. This can present a particular problem during drilling operations, in which it can be desirable to have a high fluid flow rate in order to remove drilling debris more effectively. Moreover, on long lateral wells, the maximum fluid flow rates are sometimes limited by the pressure capacity of surface equipment or tubing. Pressure drop through the tubing string is very significant and consumes the majority of available pumping pressure capacity. Furthermore, vibration downhole can damage or undesirably loosen components of conventional disconnects.

[0025] This disclosure is directed to a disconnect assembly that includes an upper and lower sleeve that are held together (fastened) by an interference fit. As described in greater detail, the interference fit can in some instances be configured such that it can be unseated (to thereby unfasten the lower sleeve from the upper sleeve) by application of a specified tensile force along a central axis of the tool. The disconnect assemblies of the present disclosure provide for a larger flow area compared to conventional disconnects, minimizing the contribution of the disconnect to pressure drop. Furthermore, by reducing or eliminating many of the moving or movable mechanical components of conventional disconnects, the disconnect assemblies of the present disclosure are more resistant to the effects of downhole vibration.

[0026] In some instances (described in greater detail below), application of a specified hydraulic pressure between the interference fit can loosen the interference fit to enable axial separation of the two sleeves by a lesser tensile force than otherwise would be required. In some instances, the assembly can include a check valve to maintain well control after disconnect.

[0027] FIGS. 1A-1B are a schematic diagrams of a wellbore drilling system 10 configured to drill a wellbore 12, in accordance with an embodiment of the present disclosure. Wellbore 12 can extend from the surface 14 through the Earth to one or more subterranean zones 16 of interest. The wellbore drilling system 10 includes a wellhead 18 supporting tubing string 20 disposed in wellbore 12. In the illustrated instance, wellhead 18 comprises a drilling rig and tubing string 20 comprises a drill string; in other instances, tubing string 20 can comprise a tool string, injection string, production string, or other string, In the illustrated instance, tubing string 20 comprises coiled-tubing; in other instances tubing string 20 can comprise jointed tubular segments. BHA 24 can include a drill bit that rotates for penetration through (for example) frac plugs, debris, or rock formations under the combined effect of axial load and rotation of tubing string 20. BHA 24 can further include collars, directional drilling (MWD / LWD) instrumentation, and various electrical, electronic, or mechanical components for operating and / or controlling the drill bit. BHA in the illustrated instance includes a disconnect assembly 22 connecting BHA 24 to tubing string 20. Disconnect assembly 22 includes an upper body 23a releasably attached to a lower body 23b. In FIG. 1B, BHA 24 has been disconnected from tubing string 20 by unfastening lower body 23b from upper body 23a, as described in further detail below.

[0028] In some instances disconnect assembly 22 can be disposed further uphole on the tubular string; for example, in some instances, a disconnect assembly 22 can releasably connect an uphole segment of tubing to a downhole segment of tubing. In some instances, disconnect assembly 22 can be a component of the BHA. In accordance with instances of the present disclosure, disconnect assembly 22 can be (or can comprise), for example, disconnect assembly 200 of FIG. 2, disconnect assemblies 300a, 300b, or 300c of FIGS. 3A, 3B, and 3C, respectively, disconnect assembly 400a of FIGS. 4A-4D, disconnect assembly 400b of FIG. 5, disconnect assembly 400c of FIG. 6, disconnect assembly 400d of FIG. 7, disconnect assembly 800 of FIG. 8, or another suitable disconnect assembly.

[0029] FIG. 2 is a schematic illustration of a downhole disconnect assembly 200 that could be used as the disconnect assembly 22 of FIGS. 1A-1B in accordance with an instance of the present disclosure. The assembly 200 includes an upper body 102 (an uphole end of which is configured to attached to a downhole end of a tubing string 150 (which can be, as in the illustrated instance, tubing string 20 of FIGS. 1A-1B) via a threaded connection or other suitable connection) and a lower body 104 (a downhole end of which is configured to attach to the BHA, to a tubing segment, or to another downhole apparatus or tubing string component, via a threaded connection or other suitable connection). Assembly 200 is configured to permit flow of fluid (such as drilling fluid, completion fluid, or another type of fluid) downhole therethrough. More specifically, assembly 200 defines a tool assembly bore 114 configured to permit flow of fluid from tubing string 150 through the tool assembly to a downhole end of the tool assembly (to thence flow to the BHA or other downhole components). In the illustrated instance, central axis 106 of assembly 200 is parallel and coincident with a central axis 152 of tubing string 20 and with the axis 110 of the tool assembly bore.

[0030] Upper body 102 comprises an upper sleeve 124 contacting a lower sleeve 128 of lower body 104 at an interface 118 between an outer surface 122 of upper sleeve 124 of upper body 102 and a inner surface 126 of lower sleeve 128 of lower body 104, such that upper sleeve 124 is an inner sleeve within (outer) lower sleeve 128. Although in the illustrated instance the upper sleeve 124 is an inner sleeve within the lower sleeve 128, it will be understood that in other instances the lower sleeve may be an inner sleeve within an outer upper sleeve. Interface 118 is dimensioned for an interference fit, the friction of which at least partially fastens lower sleeve 128 to upper sleeve 124. More specifically, when not fastened together, the outer diameter of upper sleeve 124 is greater than the inner diameter of lower sleeve 128 at a corresponding location, such that one or both of the sleeves are elastically or plastically deformed when the upper sleeve is fully received into the lower sleeve. Interface 118 is dimensioned such that a specified tensile force transmitted along central axis 106 overcomes the friction of the interference fit to unseat the interference fit and thereby unfasten the lower sleeve from the upper sleeve. For example, in some instances, the interface can be dimensioned such that the specified tensile force is about 50,000 to 55,000 pounds. In other instances the interface can be dimensioned for a greater or lesser specified tensile force than such a range. In some instances interference fit is configured to be loosened by application of a torsional force about the central axis of the tool, thus reducing the specified tensile force required for such unfastening.

[0031] The sleeves can be assembled together by, for example, pressing the sleeves together with force sufficient to cause the deformation of one or both of the sleeves to achieve the interference fit with a specified tensile force required for separation. However, because the frictional force resisting a single instance of applied pressing force may be primarily due to dynamic friction, and because dynamic friction is typically lower than static friction, a single instance of pressing may result in an interference fit that requires more than the specified tensile force to separate. Therefore, in some instances, a more precise interference fit can be achieved by pressing the sleeves together in short, staggered increments. For example, the sleeves can initially be pressed together with a force at (or just below) the specified tensile force, and then the system allowed to settle. Then sleeves can again be pressed at (or just below) the specified tensile force and the system allowed to settle. Such pressing at (or just below) the specified tensile force and letting the system settle can be repeated until application of the specified tensile force does not cause the sleeves to further move relative to one another. Incrementally applying force and letting the system settle in this way can ensure that the specified tensile force being applied is being resisted by static friction between the sleeves as opposed to dynamic friction between the sleeves. In some instances, prior to (or instead of) pressing the sleeves together, lower sleeve 128 is heated relative to upper sleeve 124 to expand lower sleeve 128 (and / or upper sleeve 124 cooled relative to lower sleeve 128), with the sleeves then allowed to return to their previous temperatures, thus establishing the interference fit.

[0032] In some instances, the interference fit is achieved during assembly by applying axial force and / or by rotation. The interference fit may also be achieved by the plastic expansion of an inner sleeve or plastic compression of the outer sleeve, via, for example, the application of heating and / or cooling to the components and / or a shrink-fit process. In some instances, the sleeves can include threads to enhance the plastic deformation.

[0033] The specified tensile strength to separate can be selected so that the sleeves do not inadvertently separate due to tension encountered in the string during use (e.g., during drilling). The specified tensile strength to separate can also be established through the use of different surface finishes (coarser / finer, patterns) and coatings (for example, hard surfacing, Teflon coating, or coating with grit) to affect the friction. In some instances, the fastening may be in part by the friction of the interference fit and in partially by a supplemental fastening mechanism (such as one or more shear pins, as described below). In such instances, the specified tensile strength reflects not only the friction of the interference fit but also the strength of the supplemental fastening mechanism.

[0034] Materials, bonding agents, lubricating agents, coatings, surface finishes (such as coarser of finer finishes), bonding agents or other coatings or materials, surface grooves or patterns, intermediate sleeves, and / or machined profiles can be selected to reach the desired friction of the pressed sleeves. In some instances, a higher coefficient of friction between the press fit sleeves can reduce the required length of the sleeves.

[0035] In the illustrated instance, the mating surfaces of upper sleeve 124 and lower sleeve 128 are tapered cylinders; i.e., the outer diameter of the upper body is smaller at the downhole end than at the uphole end, with the inner diameter of the lower body is larger at the uphole end than at the downhole end. However, in other instances sleeves may not be tapered and / or may have other shapes such as elliptic cylinders or polygonal cylinders. In some instances, one or more sleeves being tapered can make assembly easier. Tapering sleeves can also facilitate attaining the amount of friction needed (by the length of overlap of the sleeves) while making disconnect easier and consistent. For example, during disconnect, as the two bodies part, the contact force (and thus friction) between the sleeves may decrease because the inner diameter of the uphole end of the outer sleeve is larger than the outer diameter of the inner sleeve.

[0036] In some instances, one or both of upper sleeve 124 and lower sleeve 128 can have a constant thickness. For example, in the illustrated instance, the thickness of lower sleeve 128 is constant. In some instances, one or both of upper sleeve 124 and lower sleeve 128 can have a thickness that varies along the axis of the assembly.

[0037] In certain instances, the upper sleeve 124 and lower sleeve 128 can be provided with interlocking splines. Although interface 118 with the interference fit provides a seal against flow of fluids into or out of the assembly when fastened, seals 140 (which can comprise, for example, a flexible elastomer such as an o-ring or another elastomer seal, metal, fiber-reinforced composite and / or another type of seal) can augment the seal when the upper and lower bodies are fastened and can maintain the seal (at least partially) during disconnect.

[0038] In some instances of the present disclosure, the disconnect assembly is configured such that, when disconnection is desired, the operator can loosen the interference fit by initiating a passing of fluid (such as wellbore fluid or hydraulic fluid) into the interface between the sleeves. An instance of such a configuration is shown as disconnect assembly 300a of FIG. 3A. Disconnect assembly 300a is similar to assembly 200 of FIG. 2 (including the same numbered components) except that it also includes fluid passageway (port) 158 and a ball seat 132 (and, as described below, also includes a shear pin 144). By increasing fluid pressure within central bore 114 to above a specified pressure threshold, fluid passes from central bore 114 through port 158 into interface 118, thereby loosening the interference fit by at least partially deforming upper sleeve 124 and / or lower sleeve 128. Thus, prior to the application of the specified hydraulic pressure, the interface may remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force required when the specified hydraulic pressure is applied. For example, assembly 300a can be configured such that, in the absence of application of hydraulic pressure, a specified tensile force of 50,000 pounds would be required to unseat the interference fit. However, in such example configuration, with the application of a specified hydraulic pressure of (for example) 3000 pounds per square inch at the interface, the specified tensile force required to unseat the interface would be less than 50,000 pounds (for example, 30,000 pounds). In other words, an assembly can be configured such that greater specified hydraulic pressure results in a lesser specified tensile force than would otherwise be required for unseating, and vice-versa. In some instances, the assembly can be configured that a sufficiently high specified hydraulic pressure can unseat the interference fit and the assembly thereby unfastened without the application of any tensile force. In other words, in some instances, the assembly can be configured such that, with application of a hydraulic pressure that is sufficiently high, the specified tensile force can be zero (or approximately zero).

[0039] The hydraulic pressure increase to the specified hydraulic pressure can be initiated simply by pressuring up the tubing but can be enhanced by dropping a ball, dart, or activating another device in the tubing string. In the instance shown in FIG. 3A, ball 130 can be dropped into string, travelling down into bore 114 to land in ball seat 132. With ball 130 so seated, the pressure is increased to above the specified pressure threshold. In the illustrated instance, ball seat 132 is part of upper body 102; however, in some instances the ball seat may be part of lower body 104 or elsewhere downhole of upper body 102 in the disconnect assembly 300a or in the tubing string 150. Seals 142 (in combination with seals 140) isolate interface 118 as the fluid initially flows through port 158 into the interface.

[0040] The fastening of the lower body to the upper body can in some instances be in part by releasable mechanical lock, in addition to the interference fit. For example, in the illustrated instance, lower body 104 of assembly 300a is fastened not only by the interference fit but also by shear pin 144. Other suitable fasteners can include shear screws, snap rings, frictional devices, bonding, or necked-down sleeves configured to fail or separate under specified tensile loads. In some instances the fastening is only by the interference fit (with no shear pin or other fastening devices).

[0041] In some instances interference fit is configured to be loosened by application of a torsional force about the central axis of the tool, thus reducing the tensile force required for unfastening. One or both of the sleeves 124, 128 may include one or more grooves oriented generally axially to provide passages for fluid movement between the sleeves to facilitate release. Such grooves can be, for example, straight, helical, or circular extending from proximate the port 158 toward the uphole end.

[0042] FIG. 3B is a schematic illustration of a downhole disconnect assembly 300b in accordance with another instance of the present disclosure that could be used as the disconnect assembly 22 of FIGS. 1A and 1B. The disconnect assembly 300b is similar to assembly 300a of FIG. 3A, except as noted below. As above, assembly 300b is configured to be connected to a downhole end of a tubing string disposed within a wellbore and includes an upper body 102 and a lower body 104, configured for flow of fluid (such as drilling fluid) downhole therethrough. Also similar to assembly 300a, upper body 102 and lower body 104 are dimensioned for an interference fit at an interface between an outer surface of upper sleeve 124 of upper body 102 and a inner surface of lower sleeve 128 of lower body 104, and the friction of the interference fit at least partially fastens the lower body 104 to upper body 102. In the instance illustrated in FIG. 3B, a clutch 170 is included to provide additional torque capacity to the disconnect. In FIG. 3B, the clutch comprises castellated surface 172 on the uphole end of the lower sleeve 128 that mates with corresponding castellated surface 174 on the uphole end of the upper sleeve 124 when the upper and lower sleeves 124, 128 are fully received together. Teeth of the interfacing castellated surfaces 172, 174 engage to prevent relative rotation of the upper and lower sleeves 124, 128 when torque is applied to the disconnect assembly 300b.

[0043] FIG. 3C is a schematic illustration of a downhole disconnect assembly 300c in accordance with another instance of the present disclosure in which compression rings are used to (at least in part) achieve the desired interference fit. The disconnect assembly 300c is similar to assembly 300a of FIG. 3A, except as noted below. As above, assembly 300c of FIG. 3 is configured to be connected to a downhole end of a tubing string disposed within a wellbore and includes an upper body 102 and a lower body 104, configured for flow of fluid (such as drilling fluid) downhole therethrough. Also similar to assembly 300a, upper body 102 and lower body 104 are dimensioned for an interference fit at an interface between an outer surface of upper sleeve 124 of upper body 102 and a inner surface of lower sleeve 128 of lower body 104. The friction of the interference fit at least partially fastens the lower body 104 to upper body 102. Compression rings 190 are shown installed on the outer surface of the lower sleeve 128 and expansion rings 192 are installed on the inner surface of the upper sleeve 124. When unfastened, the inner diameter of compression rings 190 is smaller than the outer diameter of lower sleeve 128; likewise, when unfastened, the outer diameter of expansion rings 192 is larger than the inner diameter of upper sleeve 124, such that the clamping force of the compression rings and the outward force of the expansion rings causes (or enhanced) the interference fit when fastened. Compression rings 190 and / or expansion rings 192 may in some instances be comprised of a different material than sleeves 124 and 128 and can be selected based on (for example) their Young's modulus and / or yield strength to provide the desired frictional force and / or augment the modulus and / or yield strength of the sleeves. In some instances, the compression rings may be used without the expansion rings and still achieve and interference fit; in other instances, the expansion rings may be used without the compression rings and still achieve and interference fit.

[0044] Downhole tubing strings sometimes include a check valve to help maintain well control in the event that a tool or tubing at or above a wellhead develops a fluid leak or is opened. This check valve is conventionally located above the disconnect mechanism in order for it to be useful when the disconnect is activated. When a ball is pumped through the drill string, in order to activate the disconnect, the ball must pass through the check valve. Since the activation ball must pass through the check valve, the check valve is usually a flapper type check valve because the central opening passage is large enough to pass a ball. A flapper check valve has the disadvantage of being more fragile and having a smaller flow area than other check valve types such as ball or poppet types.

[0045] FIGS. 4A-4D are a schematic illustration of a downhole disconnect assembly including a ball-type check valve, in accordance with an instance of the present disclosure, which can avoid the above-described problems associated with flapper valves. As shown in FIG. 4A, assembly 400a is configured to be connected to a downhole end of a tubing string disposed within a wellbore and includes an upper body 402 and a lower body 404, configured for flow of fluid (such as drilling fluid) downhole therethrough. Upper body 402 and lower body 404 are dimensioned for an interference fit at an interface 418 between an outer surface of upper sleeve 424 of upper body 402 and a inner surface 426 of lower sleeve 428 of lower body 404. The friction of the interference fit at least partially fastens the lower body 404 to upper body 402. Like seals 140 and 142 of FIG. 3A, seals 440, 454, and 456 can maintain the seal (at least partially) during disconnect.

[0046] Turning to FIG. 4B, and similar to assembly 300a of FIG. 3A, to initiate disconnect a ball 430 is dropped into the assembly (via the tubing string) to land in ball seat 432. In contrast to assembly 300a, however, upper body 402 carries a piston 450 within upper sleeve 424 that defines a pressure chamber 452, sealed by upper piston seal 454 and lower piston seal 456 and the interference fit at interface 418, and that is filled with a specified fluid (e.g., mineral oil, silicone oil, water, polyethylene glycol (PEG) or another relatively incompressible fluid) via fill port 458. Due to the size of the chamber 452 and piston 450, when the release ball 430 seats on the ball seat 432 and pressure is applied to shift piston 450, the pressure of the specified fluid in chamber 452 will increase significantly more than the pressure applied to the ball 430. With the increase in pressure, the specified fluid from the chamber 452 flows into the interface 418, thus loosening the interference fit.

[0047] Assembly 400a also includes a check valve 460 that prevents flow of fluid in an uphole direction and thus provides well control prior to disconnect and also upon unfastening of lower body 404 from upper body 402. In the illustrated instance, check valve 460 is a ball-type valve including check valve ball 462. The force of the flow of fluids in a downhole direction pushes ball 462 downhole to maintain an open position (e.g. during drilling operations), as shown in FIG. 4A, but upon disconnect, as shown in FIG. 4C, spring 465 and any uphole flow biases ball 462 to a closed position-with check-valve ball 462 pressed against check valve ball seat 464—thus maintaining well control as lower body 404 separates from upper body 402. FIG. 4D illustrates assembly 400a in which lower body 404 has fully separated from upper body 402, with check valve ball 462 remaining seated so as to prevent flow of well fluid 470 uphole through the assembly. Although in assembly 400a a ball check valve is shown, another type of check valve may be utilized, including a poppet valve, sliding sleeve or other check valve.

[0048] In some circumstances, a tubing string can become stuck because debris accumulates above, below, or otherwise near component exterior shoulders or other protrusions. This can be a particular problem for coiled-tubing strings, in which the diameter of the disconnect tool may be larger than that of the coiled tubing. If the disconnect is located below this shoulder, it may not be able to release the coiled tubing from the tool since debris prevents axial motion of the parts above the disconnect. In the instance shown in FIG. 5, for example, a slick disconnect is included to at least partially avoid hanging up on built-up debris. Assembly 400b of FIG. 5 is similar to assembly 400a of FIGS. 4A-4D with the same components except that, instead of a threaded connection, a coiled tubing connector 502 connects assembly 400b to tubing string150. An area 504 above shoulder 506 is an example of an area where debris buildup might be expected. In the instance shown in FIG. 5, the outer diameters of coiled tubing connector 502 and of upper body 402 are substantially equal to or smaller than the outer diameter of tubing string 150, thus minimizing or eliminating drag on the built-up debris.

[0049] In some instances a portion or the entirety of the interface between the sleeves may be threaded with, for example, box-and-pin threads. In some instances the threads can be non-locking thread forms such that the lower sleeve rotates axially relative to the upper sleeve with the application of tensile force, without application of torsional force.

[0050] In some instances it may be desired to maintain the ability to pump, from surface, through the disconnect device even after a disconnect event has been completed. For example, if a tubing string is stuck above the BHA, an effort will be made to cut the tubing. This tubing cut may require the displacement of an actuating ball or a cutting tool by fluid movement down the tubing string. FIGS. 7A-7B are schematic illustrations of a downhole disconnect assembly in accordance with another instance of the present disclosure, in which such pump-through is enabled. Assembly 400c of FIGS. 6A-6B is similar to assembly 400a of FIGS. 4A-4D with the same components, except that, in lieu of ball seat 432 of assembly 400a, assembly 400c includes ported seat assembly 602 that as shown in FIG. 6A (and similar to seat 432 of FIGS. 4A-4D) catches ball 430. As shown in FIG. 6B and pressure applied to shift piston 450, as described in reference to FIGS. 4A-4D. Port 604 permits fluid to flow through the tool even after seating of the ball and as pressure is increased. Port 604 can be sized such that the increased pressure within the work string above the seated ball will be sufficient to actuate the disconnect while permitting the desired continued flow of fluid.

[0051] FIGS. 7A-7C are schematic illustrations of another instance of the present disclosure in which such pump-through of fluids is enabled. Assembly 400d of FIGS. 7A-7C is similar to assembly 400a of FIGS. 4A-4D with the same components, except that, in lieu of ball seat 432 of assembly 400a, assembly 400d includes dual-seat catcher assembly 702 that includes an upper seat 704 and a lower seat 706, as shown in FIG. 7A. Similar to seat 432 of FIGS. 4A-4D, upper seat 704 is sized to catch ball 430 to shift piston 450 as pressure applied, as described in reference to FIGS. 4A-4D, as shown in FIG. 7B. Upper ball seat 704 includes an expandable or deformable lip 708 upon which ball 430 lands. Lip 708 is configured such that, as pressure is further increased to above a specified threshold, the lip deforms, allowing for the ball 430 to pass through to lower seat 706 as the lower body is disconnected from the upper body, as shown in FIG. 7C. Lower seat 706 includes ports 710 which, like port 604 of FIGS. 6A-6B, permits fluid to flow through the tool even after seating of the ball and as pressure is increased.

[0052] In some instances, the tool can be configured such that ball 430 itself acts as a check valve. Specifically, for example, the tool may be configured such that application of sufficient pressure (for example, 10,000 psi) causes ball 430 to pass through upper seat 704. If the strain in lip 708 caused by the passing of the ball is less than the elastic limit of the lip material, then the lip will return to its original size (or, if the strain in the lip is plastic, then the lip may return elastically a diameter greater than the original size but nevertheless smaller than the ball). A subsequent flow of fluid in uphole direction would push the ball uphole to land on a lower surface of lip 708, thus blocking the flow into the tool. If the lip was strained elastically during the seating process, the pressure required to pass uphole through the lip is expected to be at least the seating pressure. If the lip was strained plastically during the seating process, the pressure required to pass up through the lip may be less than the seating pressure due to the distortion of the lip.

[0053] FIG. 8 is a schematic illustration of a downhole disconnect assembly 800 in accordance with another instance of the present disclosure. Similar to disconnect assembly 400a of FIGS. 4A-4D, upper body 802 and lower body 804 are dimensioned for an interference fit at an interface 818 between an outer surface of upper sleeve 824 of upper body 802 and a inner surface 826 of lower sleeve 828 of lower body 804. The friction of the interference fit at least partially fastens the lower body 804 to upper body 802. Assembly 800 includes a differential pressure chamber 880 defined in part by an outer surface of piston 850, an inner surface of sleeve 824, upper piston seal 854, and lower piston seal 856. Chamber 880 can be filled with mineral oil or another suitable fluid. To initiate disconnect, a ball (not shown) is dropped into the assembly (via the tubing string) to land in ball seat 832, and pressure increased to shift piston 850. In contrast to pressure chamber 452 of FIGS. 4A-4D, as bore pressure increases (urging piston 850), pressure within chamber 880 will decrease (and in some instances may decrease to a vacuum or near-zero pressure). The pressure differential between the annulus 870 surrounding the tool and the chamber 880 elastically strains sleeve 824, loosening the interference fit at interface 818 such that a specified tensile force can separate the upper and lower bodies. In some instances, elastic strain and the pressure differential between annulus 870 and chamber 880 is sufficient to permit fluid from annulus 870 to flow into interface 818, further loosening the interference fit. Once the disconnect is separated and the activation pressure is released, check valve 860 can provide well control similar to check valve 460 of FIGS. 4A-4D.

[0054] The term “uphole” as used herein means in the direction along a wellbore from its distal end towards the surface, and “downhole” as used herein means the direction along a wellbore from the surface towards its distal end. A downhole location means a location along a wellbore downhole of the surface. The terms “a,”“an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

[0055] While this disclosure contains many specific implementation details, these should not be construed as limitations on the subject matter or on what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this disclosure in the context of separate implementations can also be implemented, in combination, or in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0056] Particular implementations of the subject matter have been described. Nevertheless, it will be understood that various modifications, substitutions, and alterations may be made. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. Accordingly, the previously described example implementations do not define or constrain this disclosure.

Claims

1. A tool assembly configured to connect to a downhole end of a wellbore tubing string, the tool assembly comprising:an upper sleeve; anda lower sleeve contacting the upper sleeve at an interface between a surface of the upper sleeve and a surface of the lower sleeve, the tool assembly defining a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly, the interface dimensioned for an interference fit that:at least partially fastens the lower sleeve to the upper sleeve; andis unseated, to thereby unfasten the lower sleeve from the upper sleeve, by loosening the interference fit by passing fluid from a fluid volume into the interface in response to application of a specified hydraulic pressure in the tool assembly bore or an annular volume exterior of the tool.

2. The tool assembly of claim 1, wherein the interference fit is configured:to be unseated by the application of both a specified tensile force along a central axis of the tool and the specified hydraulic pressure; andto, prior to the application of the specified hydraulic pressure, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

3. The tool assembly of claim 2, wherein the interference fit is configured to, prior to application of a torsional force about the central axis of the tool, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

4. The tool assembly of claim 1, the tool assembly comprising a fluid passageway fluidically connecting the fluid volume to the interface, the fluid passageway and the interface configured to, when the tool assembly is connected to the downhole end of the tubing string and the tubing string is disposed within the wellbore, permit, in response to the application of the specified hydraulic pressure, the passing of fluid through the fluid passageway into the interface.

5. The tool assembly of claim 1, wherein:the tool assembly bore at least partially defines the fluid volume.

6. The tool assembly of claim 4, wherein:the fluid volume is within the tool assembly and is at least partially defined by a piston; andthe application of the specified hydraulic pressure is by application of a force applied to the piston thereby increasing a fluid pressure of the fluid volume.

7. The tool assembly of claim 1, wherein the fluid volume is the annular volume exterior of the tool.

8. The tool assembly of claim 2, wherein the central axis of the tool assembly is parallel with an axis of the tubing string center bore.

9. The tool assembly of claim 2, wherein the central axis of the tool assembly is parallel with an axis of the tool assembly bore.

10. A system for well operations, the system comprising:a tubing string disposed in a wellbore; andtool assembly configured connected to a downhole end of the tubing string, the tool assembly comprising:an upper sleeve; anda lower sleeve contacting the upper sleeve at an interface between a surface of the upper sleeve and a surface of the lower sleeve, the tool assembly defining a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly, the interface dimensioned for an interference fit that:at least partially fastens the lower sleeve to the upper sleeve; andis unseated, to thereby unfasten the lower sleeve from the upper sleeve, by loosening the interference fit by passing fluid from a fluid volume into the interface in response to application of a specified specified hydraulic pressure in the tool assembly bore or an annular volume exterior of the tool.

11. The system of claim 10, wherein the interference fit is configured:to be unseated by the application of both a specified tensile force along a central axis of the tool and the specified hydraulic pressure; andto, prior to the application of the specified hydraulic pressure, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

12. The system of claim 11, wherein the interference fit is configured to, prior to application of a torsional force about the central axis of the tool, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

13. The system of claim 10, the tool assembly comprising a fluid passageway fluidically connecting the fluid volume to the interface, the fluid passageway and the interface configured to, when the tool assembly is connected to the downhole end of the tubing string and the tubing string is disposed within the wellbore, permit, in response to the application of the specified hydraulic pressure, the passing of fluid through the fluid passageway into the interface.

14. The system of claim 13, wherein:the tool assembly bore at least partially defines the fluid volume.

15. The system of claim 10, wherein:the fluid volume is within the tool assembly and is at least partially defined by a piston; andthe application of the specified hydraulic pressure is by application of a force applied to the piston thereby increasing a fluid pressure of the fluid volume.

16. The system of claim 10, wherein the fluid volume is the annular volume exterior of the tool.

17. The system of claim 11, wherein the central axis of the tool assembly is parallel with an axis of the tubing string center bore.

18. The tool assembly of claim 11, wherein the central axis of the tool assembly is parallel with an axis of the tool assembly bore.

19. A method for well operations, the method comprising:supporting a lower sleeve of a tool assembly from an upper sleeve of the tool assembly while the tool assembly is subject to a tensile force less than a specified tensile force, the supporting at least in part by a fastening of the lower sleeve to the upper sleeve by an interference fit at an interface between a surface of the upper sleeve contacting a surface or the lower sleeve, the tool assembly defining a tool assembly bore configured to permit flow of fluid from a tubing string center bore through the tool assembly to a downhole end of the tool assembly;unfastening the lower sleeve from the upper sleeve by an unseating of the interference fit by loosening the interference fit by passing fluid from a fluid volume into the interface in response to application of a specified hydraulic pressure in the tool assembly bore or an annular volume exterior of the tool.

20. The method of claim 19, wherein the interference fit is configured to be unseated by the application of a specified tensile force along a central axis of the tool and the specified hydraulic pressure, and wherein the interference fit is configured to, prior to the application of the specified hydraulic pressure, remain seated when subjected to up to a maximum tensile force that is greater than the specified tensile force.

21. The tool assembly of claim 1, wherein the lower sleeve is connected to a bottomhole assembly and wherein unfastening the lower sleeve from the upper sleeve disconnects the bottomhole assembly from the tubing string uphole of the tool assembly.

22. The system of claim 10, wherein the lower sleeve is connected to a bottomhole assembly and wherein unfastening the lower sleeve from the upper sleeve disconnects the bottomhole assembly from the tubing string uphole of the tool assembly.

23. The method of claim 19, wherein the lower sleeve is connected to a bottomhole assembly and wherein unfastening the lower sleeve from the upper sleeve disconnects the bottomhole assembly from the tubing string uphole of the tool assembly.

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