GB2551827A

GB2551827A - Downhole coupling

Info

Publication number: GB2551827A
Application number: GB1611501.6A
Authority: GB
Inventors: Philip Churchill Andrew
Original assignee: Churchill Drilling Tools Ltd
Current assignee: Churchill Drilling Tools Ltd
Priority date: 2016-06-30
Filing date: 2016-06-30
Publication date: 2018-01-03
Also published as: GB201611501D0; WO2018002642A1

Abstract

Disclosed are coupling methods and systems. A method of fabricating a downhole assembly comprises translating an apparatus into a first tubular member or pipe through a female coupling portion (fig 1, 16) on an end of the first tubular member. A male thread provided on a male coupling portion (fig 1, 14) of a second tubular member is then made up to a female thread provided on the female coupling portion. The male and female coupling portions are retained in a coupled configuration with a first frictional force. A support member 284 within the coupling is then configured to engage at least one of the coupling portions such that the coupling portions are retained in the coupled configuration with a second frictional force higher than the first frictional force. Also claimed is a corresponding coupling. The support member may deform at least one of the coupling portions. Also disclosed is a coupling apparatus and method wherein the support member engages an end face of the male coupling portion (figures 11-13).

Description

(54) Title of the Invention: Downhole coupling

Abstract Title: frictional threaded downhole coupling having support portion (57) Disclosed are coupling methods and systems. A method of fabricating a downhole assembly comprises translating an apparatus into a first tubular member or pipe through a female coupling portion (fig 1, 16) on an end of the first tubular member. A male thread provided on a male coupling portion (fig 1, 14) of a second tubular member is then made up to a female thread provided on the female coupling portion. The male and female coupling portions are retained in a coupled configuration with a first frictional force. A support member 284 within the coupling is then configured to engage at least one of the coupling portions such that the coupling portions are retained in the coupled configuration with a second frictional force higher than the first frictional force. Also claimed is a corresponding coupling. The support member may deform at least one of the coupling portions. Also disclosed is a coupling apparatus and method wherein the support member engages an end face of the male coupling portion (figures 11-13).

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DOWNHOLE COUPLING

BACKGROUND

This disclosure relates to a coupling, to a coupling method, and to methods of fabricating downhole assemblies. The coupling comprises a threaded female coupling portion and a threaded male coupling portion. Examples of the disclosure relate to couplings for downhole tools.

BACKGROUND

Threaded couplings are widely used in many applications, for example in connecting tubular supports and tool elements used in the oil and gas exploration and production industry. In many drilling operations drill bits and other downhole tool are mounted towards the leading end of a drill string formed of sections of drill pipe and drill collars. The drill pipe and drill collar sections are provided with threaded male and female ends couplings, typically taking the form of shouldered pin and box coupling portions. The couplings may have one or two shoulders.

In a single-shouldered coupling, the coupling portions are made up to bring an end face of the box coupling into contact with a shoulder provided at the base of the threaded pin. Applying additional torque to the coupling further engages the threads, creating axial stress in the base of the threaded pin, and may extend the pin. This provides a sealing contact between the coupling portions at the shoulder and increases the friction between the thread flanks. The threads on drill string couplings tend to have a relatively loose fit to facilitate making up of the couplings and the increased friction retains the coupling portions together. The increased friction also prevents further relative rotation between the coupling portions, which could otherwise result in excess stress being applied to the pin; coupling failure tends to manifest as shearing off at the base of the pin as a result of application of a combination of elevated tension and torque.

In a double-shouldered coupling, in addition to the contact between the end face of the box and the shoulder at the base of the threaded pin, an end face of the pin contacts an internal shoulder within the box. Thus, applying additional torque to the made-up connection further engages the threads and generates stresses in the pin which tend to extend the base of the pin and compress the end of the pin. This results in increased friction between the thread flanks at the base of the pin and at the end of the pin and tends to provide a more secure connection. Further, the presence of two shoulders prevents over-extension of the pin on the coupling experiencing elevated torques.

Double-shouldered couplings are generally considered to be more secure and capable of handling greater tensions and torques. However, double-shouldered couplings must be manufactured to higher tolerances and are thus more expensive to produce.

While double-shouldered couplings tend to have a constant internal diameter through the coupling, the boxes of single-shouldered couplings often feature a larger diameter section beyond the threaded section of the box. This section, sometimes referred to as the throat or bore-back, may be used to mount or accommodate tools or devices. Thus, it may be difficult to accommodate such tools or devices in smaller diameter pipe or tubing which features double-shouldered couplings.

SUMMARY

According to the present disclosure there is provided a method of fabricating a downhole assembly, the method comprising:

translating an apparatus into a first tubular member through a female coupling portion on an end of the first tubular member;

making up a male thread provided on a male coupling portion of a second tubular member with a female thread provided on the female coupling portion whereby the male and female coupling portions are retained in a coupled configuration with a first frictional force therebetween; and configuring a support member within the coupling to engage at least one of the coupling portions such that the coupling portions are retained in the coupled configuration with a second frictional force higher than the first frictional force.

According to a further aspect of the present disclosure there is provided a downhole assembly comprising:

a first tubular member defining an internal volume for receiving downhole apparatus;

a second tubular member for connection to the first tubular member;

a coupling comprising a female coupling portion provided on an end of the first tubular member and a male coupling portion provided on an end of the second tubular member, the female coupling portion having an internal female thread and the male coupling portion having an external male thread for cooperating with the female thread; and a support member for location within the coupling and being configurable in a first configuration and in a second configuration, in the first configuration the support member permitting the male and female threads to be made up and the coupling portions retained in a coupled configuration with a first frictional force therebetween, and in the second configuration the support member engaging at least one of the coupling portions such that the coupling portions are retained in the coupled configuration by a second frictional force higher than the first frictional force.

In the second configuration the support member may deform at least one of the coupling portions.

In the second configuration the support member may radially deform the male coupling portion. Alternatively, or in addition, in the second configuration the support member may axially deform at least one of the male coupling portion and the female coupling portion.

The support member may be configured to deflect or deform the male coupling portion and urge the male thread radially outwards relative to the female thread and into tighter engagement with the female thread.

The second configuration may produce only elastic deformation of at least one of the coupling portions. This may facilitate provision of reversible or repeatable deformation. Alternatively, the second configuration may produce plastic deformation.

The support member may be a sleeve or collar.

The support member may have an external surface which is inclined relative to a main axis of the tubular members, or which external surface is inclined relative to an opposing internal surface of the male coupling portion. Alternatively, the support member may have an external surface which is parallel to the main axis and which may also be parallel to an opposing internal surface of the male coupling portion.

An internal surface of the male coupling portion may be inclined relative to the main axis of the tubular members.

The inclined surfaces may comprise a shallow taper, for example a taper of less than 15, 10 or 5 degrees. A shallower taper tends to facilitate deformation of the at least one coupling portions.

The support member may have an external surface which, at least in the first configuration, has an outer diameter larger than an internal diameter of an opposing internal surface of the male coupling portion.

The support member may be translatable relative to one or both of the coupling portions between the first and second configurations. For example, the support member may be movable axially relative to one or both of the coupling portions. The support member may be configured for sliding relative to the coupling body. A lubricant may be provided between contacting surfaces of the support member and a coupling portion. The lubricant may be selected to increase or decrease friction between the surfaces. The support member may have a thread configured to engage with a thread provided on the coupling body. The support member thread may be parallel or tapered.

The male and female threads may take any appropriate form, and may be parallel or tapered.

One or both of the male and female threads may have a thread angle of greater than zero, whereby radial deformation of at least one of the coupling portions increases the interference and the frictional force between opposing contacting thread flanks.

In the first configuration opposing first flanks of at least some of the turns of the threads may be in contact with opposing second flanks, and the thread roots and crests may be spaced apart.

In the second configuration both the first and second thread flanks of at least some of the turns of the threads are in contact.

The thread angle may be less than 40 degrees. The threads may be Acme threads, which typically have a thread angle of 29 degrees, or metric trapezoidal threads, which typically have a thread angle of 30 degrees.

The tubular members may form part of a bottom hole assembly (BHA) or drill string section.

The female coupling portion may be a box connection. The male coupling portion may be a pin connection. The box connection may have a throat or bore-back and an internal diameter of the throat may be larger than an internal diameter of the pin connection. The internal diameter of the throat may be slightly less than the smallest minor diameter of the female thread of the box connection.

The coupling may be a shouldered coupling.

The first frictional force may be minimal, for example the friction force resulting from hand tightening a loose (Class 1) thread. In other examples the first frictional force may be significant, for example as achieved by mechanically-assisted tightening of a Class 3 thread.

The method may further comprise further configuring the support member whereby the coupling portions engage with a third frictional force lower than the second frictional force, to facilitate separating the coupling portions. The third frictional force may be substantially the same as the first frictional force.

The tubular coupling may be made up and torqued up prior to configuring the support member to deform the coupling. Alternatively, the tubular coupling may be made up but not torqued up prior to configuring the support member to deform the coupling.

A setting tool may be utilised to configure the support member, for example to pull or push the support member into the pin.

The setting tool may be hydraulically or electrically actuated, or may be configured for manual operation.

The setting tool may comprise a retractable portion for engaging the support member.

The method may further comprise engaging the support member with a setting tool and operating the tool to configure the support member to engage at least one of the coupling portions such that the coupling portions are retained in the coupled configuration with the second frictional force. The tool may be operated to deform the coupling. The method may further comprise engaging the support member with a tool and operating the tool to further configure the support member to permit uncoupling of the coupling portions. The tool may be translated into the coupling and subsequently translated out of the coupling. The tool may transmit or generate at least one of torque and axial force. The tool may comprise a formation configured to engage the support member, which form may be configured to engage an inner surface of the support member; for example the tool may comprise flats in the form of a hex.

The setting tool may comprise an occlusion so that a pressure force may be applied across the tool, and thereby apply an axial force to the support member.

The support member may be configured for mounting to the female coupling portion and be translatable to engage an end face of the male coupling portion.

The support member may have an external male thread and the female coupling portion may have a cooperating internal second female thread. The second female thread may be a continuation of the female thread provided for coupling with the male thread of the male coupling portion, or may be a separate thread which may be of a different formation or form; for example, the second female thread may have a different thread form, a different pitch, for example a smaller pitch, or may be of the opposite hand. If the second female thread is a left-handed thread, any rotation and axial translation of the male coupling portion (with a right-handed thread) induced by over-torqueing of the coupling will be resisted as any corresponding rotation of the support member will translate the support member in the opposite direction, into tighter contact with the male coupling portion. However, it is likely that providing the second female thread of the opposite hand to the first female thread would require the second female thread to be of a smaller diameter, to facilitate clearance of the first female thread when inserting the support member into the female coupling portion.

The method may further comprise rotating a threaded support member to translate the support member.

The second tubular member may be a saver sub.

The second tubular member may have a further coupling portion on the other end of the member. The further coupling portion may be a pin or a box.

A third tubular member may be provided for coupling to the other end of the first tubular member. The third tubular member may be a saver sub.

The first tubular member may be provided with a coupling portion on the other end of the member. The coupling portions on the first tubular member may be different, or may be the same.

The coupling portions may include smooth parallel sealing surfaces. The sealing surfaces may be provided at the nose of the pin and the base of the box.

The support member may be cylindrical and have an outer surface that is parallel to the main 10 axis of the tubular members. The outer diameter of the support member may be larger than the inner diameter of the pin, such that the support member is a tight press fit in the pin.

At least one of the coupling portions may comprise a seal member, for example an elastomer seal member, for engaging an opposing surface of the other coupling portion.

According to another example of the present disclosure there is provided a coupling 15 comprising:

a coupling body comprising a female coupling portion and a male coupling portion, the female coupling portion having an internal female thread and the male coupling portion comprising an external male thread for cooperating with the female thread ; and a support member for location within the coupling body and being configurable in a first 20 configuration and in a second configuration, in the first configuration the support member permitting the male and female threads to be made up and engage with a first frictional force and in the second configuration the support member deforming at least one of the coupling portions such that the male and female threads engage with a second frictional force higher than the first frictional force.

The coupling may be tubular. For example, the coupling may be a pipe or tubing coupling.

The support member may be hollow or tubular.

The male coupling portion may comprise a bolt or pin and the female coupling portion may comprises a nut.

The male coupling portion may have a hollow nose.

In the second configuration the support member may radially deform or extend the male coupling portion. Alternatively, or in addition, in the second configuration the support member may axially deform at least one of the male coupling portion and the female coupling portion.

The coupling may define a main axis.

The support member may have an external surface which is inclined relative to the main axis, or which is inclined relative to an opposing internal surface of the male coupling portion. Alternatively, the support member may have an external surface which is parallel to the main axis and which may also be parallel to an opposing internal surface of the male coupling portion.

An internal surface of the male coupling portion may be inclined relative to the main axis.

The support member may be translatable relative to one or both of the coupling portions between the first and second configurations. For example, the support member may be movable axially relative to one or both of the coupling portions. The support member may be configured for sliding relative to the coupling body. A lubricant may be provided between contacting surfaces of the support member and a coupling portion. The support member may have a thread configured to engage with a thread provided on the coupling body. The support member thread may be parallel or tapered. In other aspects of the disclosure the support member may be incorporated in or otherwise fixed relative to a coupling portion. The support member may comprise a material which changes in form or dimensions between the first and second configurations. For example, the support member may be in the first configuration when the support member is at a first temperature and may be in the second configuration when the support member is at a higher second temperature. The support member may transform from the first configuration to the second configuration and may transform from the second configuration to the first configuration. The support member may take any appropriate form and comprise any appropriate material. The support member may comprise a one way or a two way shape memory material.

The male and female threads may take any appropriate form, and may be parallel or tapered..

One or both of the male and female threads may have a thread angle of greater than zero, whereby radial deformation of at least one of the coupling portions increases the interference and the frictional force between opposing contacting thread flanks. The thread angle may be less than 40 degrees. The threads may be Acme threads, which typically have a thread angle of 29 degrees, or metric trapezoidal threads, which typically have a thread angle of 30 degrees.

The coupling may comprise a coupling for a downhole apparatus such as a tool or support, for example an element of a bottom hole assembly (BHA) or other drill string section.

The coupling may be a shouldered coupling.

According to another aspect of the disclosure there is provided a coupling method comprising:

making up a coupling by making up an external male thread provided on a male coupling portion with an internal female thread provided on a female coupling portion whereby the male and female threads engage with a first frictional force; and configuring a support member within the coupling to deform the coupling whereby the male and female threads engage with a second frictional force higher than the first frictional force.

The method may further comprise further configuring the support member whereby the male and female threads engage with a third frictional force lower than the second frictional force, to facilitate separating the coupling portions. The third frictional force may be substantially the same as the first frictional force.

The method may further comprise axially translating the support member relative to the coupling to deform the coupling. Axial translation of the support member relative to the coupling may radially extend the male coupling portion. Alternatively, or in addition, axial translation of the support member relative to the coupling may axially deform at least one of the male coupling portion and the female coupling portion.

The method may further comprise engaging the support member with a tool and operating the tool to configure the support member to deform the coupling. The method may further comprise engaging the support member with a tool and operating the tool to further configure the support member. The tool may be translated into the coupling and subsequently translated out of the coupling. The tool may transmit or generate at least one of torque and axial force. The tool may comprise a formation configured to engage the support member, which form may be configured to engage an inner surface of the support member; for example the tool may comprise flats in the form of a hex.

According to an alternative aspect of the present disclosure there is provided a coupling method comprising:

making up a male thread provided on a male coupling portion with a female thread provided on a female coupling portion whereby the male and female coupling portions are retained in a coupled configuration with a first frictional force; and configuring a support member within the coupling to engage at least one of the coupling portions such that the coupling portions are retained in the coupled configuration with a second frictional force higher than the first frictional force.

According to a further alternative aspect of the present disclosure there is provided a coupling comprising:

a coupling body comprising a female coupling portion and a male coupling portion, the female coupling portion having an internal female thread and the male coupling portion comprising an external male thread for cooperating with the female thread; and a support member for location within the coupling body and being configurable in a first configuration and in a second configuration, in the first configuration the support member permitting the male and female threads to be made up and the coupling portions retained in a coupled configuration by a first frictional force, and in the second configuration the support member engaging at least one of the coupling portions such that the coupling portions are retained in the coupled configuration by a second frictional force higher than the first frictional force.

According to another aspect of the present disclosure there is provided a tubular coupling comprising:

a female coupling portion having an internal female thread;

a male coupling portion having: an external male thread for cooperating with the female thread, and an end face; and a support member for mounting to the female coupling portion and being translatable to engage an end face of the male coupling portion.

The support member may have an external male thread and the female coupling portion may have a cooperating internal second female thread. The second female thread may be a continuation of the female thread provided for coupling with the male thread of the male coupling portion, or may be a separate thread which may be of a different formation or form; for example, the second female thread may have a different thread form, may have a different pitch, for example a smaller pitch, or may be of the opposite hand. If the second female thread is a left-handed thread, any rotation and axial translation of the male coupling portion (with a right-handed thread) induced by over-torqueing of the coupling will be resisted as any corresponding rotation of the support member will translate the support member in the opposite direction, into tighter contact with the male coupling portion. However, it is likely that providing the second female thread of the opposite hand to the first female thread would require the second female thread to be of a smaller diameter, to facilitate clearance of the first female thread when inserting the support member into the female couple portion.

According to a further aspect of the present disclosure there is provided a coupling method comprising:

coupling an external male thread provided on a male coupling portion with an internal female thread provided on a female coupling portion; and translating a support member mounted on the female coupling portion to engage a leading end face of the male coupling portion .

In the interests of brevity the all of the various optional and alternative features of the various different aspects of the disclosure have not been repeated with particular reference to each aspect. However, the various optional and alternative features may be, and are intended to be, combined with the different aspects where appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a sectional view of a single-shouldered pin and box connection;

Figure 2 is a sectional view of a double-shouldered pin and box connection;

Figure 3 is shows a drill string segment incorporating a connection of the disclosure;

Figure 4 is a sectional view of a connection and setting tool of the disclosure;

Figure 5 is an enlarged view of area 5 of Figure 4;

Figure 6 is an enlarged view of area 6 of Figure 5;

Figures 7 to 12 are sectional views of different connections of the disclosure; and

Figure 13 is a sectional view of the connection of Figure 12 and a setting tool.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figures 1 and 2 of the drawings, which illustrate downhole connections or couplings 10, 12 as used in drill pipe strings. The illustrated connections 10, 12 are typically used to connect drill collars for location in 6 inch (152.40 mm) diameter bores.

Figure 1 shows a full strength NC38 connection 10 having a male coupling portion in the form of an externally threaded pin 14 and a female coupling portion in the form of an internally threaded box 16. The connection 10 features tapered threads 18, 20 which facilitate stabbing in and making up of the connection and reduce the risk of thread damage during make-up. The threads 18, 20 are loose fit (Class 1). The pin 14 includes a stress relief groove 22 at the base of the thread 18. The box 16 includes a standard throat or bore-back 24.

The connection 10 is single-shouldered; in the made-up connection 10 a pin shoulder 26 adjacent the stress relief groove 22 engages an end face 28 of the box 16. The end face of the pin 30 is unrestrained and extends into the bore-back 24.

The connection 10 has a 5 inch (127.00 mm) outer diameter. The pin 14 has an internal diameter of 2.19 inches (55.63 mm) and beyond the thread 20 in the bore-back 24 the box 16 has a maximum internal diameter of 3.47 inches (88.11 mm). In use, the connection 10 has a make-up torque of 10 - 12 kft-lbs (13.59 - 16.27 kNm).

When fully made-up, the connection 10 achieves a fluid-tight seal from the contact between the pin shoulder 26 and the box end face 28. Also, at the make-up torque, at least the base of the pin 14 is in tension and may be fractionally extended, increasing the friction between the first few thread turns of the pin 14 and box 16 at area 31. This increased friction maintains the connection 10 secure, and limits the effect of elevated torques being applied to the connection 10. However, an excess torque may overcome this frictional force and result in the male thread 18 advancing further along the female thread 20. As the engagement between the shoulder 26 and face 28 restrains further movement at the base of the pin 14, this advancement must be accommodated by extension of the pin 14, primarily in the region of the stress relief groove 22. Ultimately, particularly in the face of a combination of elevated torque and tension, the pin 14 may fail or “twist off’ in the region of the groove 22.

A similar thread arrangement (but without the stress relief groove 22) is often present on 3.5 inch (88.9 mm) diameter drill pipe as commonly used in 6 inch (152.40 mm) diameter bores.

Figure 2 shows a standard NC38 DSTJ connection 12 having a male coupling portion in the form of an externally threaded pin 34 and a female coupling portion in the form of an internally threaded box 36. The connection 12 features tapered threads 38, 40.

The connection 12 is double-shouldered; in the made-up connection 12 a pin shoulder 46 adjacent the base of the pin 34 engages an end face 48 of the box 36, and the end face of the pin 50 engages a shoulder 52 at the base of the box 36.

The connection 12 has a 4.875 inch (123.83 mm) outer diameter and the pin 34 and box 36 both have an internal diameter of 2.60 inches (66.09 mm). The connection 12 has a make-up torque of 19 kft-lbs (25.76 kNm). When the connection 12 is torqued up there is a fluid-tight seal between the pin shoulder 46 and the box end face 48, and also between the pin end face 50 and the pin shoulder 52. The tolerances between the shoulders 46, 52 and the end faces 48, 50 are relatively tight, to ensure that both contacts are achieved. Further, the make-up torque is intended to create tension in the base of the pin 34 and compression in the nose of the pin 64, increasing friction between the thread turns at the base of the pin 56 and end of box 58 at area 57, and towards the nose of the pin 64 and the base of the box 64, at area 59.

As with the single-shoulder connection 10, this increased friction maintains the doubleshouldered connection 12 secure, and limits the effects on the connection 12 when experiencing elevated torques. However, unlike the single-shouldered connection 10, an excess torque which would overcome this frictional force will not result in the male thread 38 advancing further along the female thread 40; the engagement between the box shoulder 52 and the pin end face 50 restrains further movement of the end of the pin 34. This results in the double-shouldered connection 12 being significantly stronger than the equivalent single-shouldered connection 10, despite the smaller outer diameter and larger outer diameter of the single-shouldered connection.

However, there are some disadvantages associated with double-shouldered connections. As noted above, to ensure that the connection 12 can be properly made-up the tolerances between the shoulders 46, 52 and the end faces 48, 50 must be relatively precise, thus adding to manufacturing costs. Also, if there is a wish to mount or locate tools or devices within the string, the standard boreback 24 of a single-shouldered connection 10 provides a convenient location to receive such tools. A double-shouldered connection does not provide such a space, such that a bespoke or more complex solution must be found, particularly in smaller diameter connections.

Reference is now made to Figure 3 of the drawings, which shows a drill string segment 61 incorporating connections 60 of the disclosure. The segment 61 includes a central portion 63 which accommodates downhole apparatus 65, such as a valve, motor, sensor or the like. The ends of the central portion 63 are coupled to respective saver subs 67, 69 via connections 60 as described below with reference to Figure 4 of the drawings. The saver subs 67, 69 feature a double shouldered box 75 and a pin 83 for coupling with adjacent drill string segments.

With the saver subs 67, 69 removed, the central portion 63 may receive the apparatus 65. If desired, parts of the apparatus 65 may be inserted from an appropriate end of the portion 63, which may facilitate assembly. The ability to access the interior of the portion 63 from both ends may also facilitate manufacture of the portion 63, as cutting tools and the like may access the interior from both ends. Once the apparatus 65 has been positioned within the central portion 63 the saver subs 67, 69 are coupled to the ends of the central portion 63. These operations will likely be carried out in a workshop environment; only the end connections 75, 83 will be made up to other drill string components on the rig. In an alternative arrangement, only one end of a drill string segment is provided with a connection 60 in accordance with the disclosure. A conventional saver sub with a conventional connection could be provided at the other end, or the lower saver sub 69 could be omitted and a conventional pin 83a provided on the lower end of the portion 63. In such a situation the apparatus 65 would be inserted into the portion 63 from the upper end.

Figure 4 is a sectional view of the connection 60 at the upper end of the segment 61, between the central portion 63 and the upper saver sub 67. Also shown is a hydraulically actuated setting tool

62. The connection 60 includes a male coupling portion in the form of an externally threaded pin 64 and a female coupling portion in the form of an internally threaded box 66. The connection 60 features stub Acme threads 68, 70. The pin 64 includes a stress relief groove 72 at the base of the thread 68. The box 66 includes a stress relief groove 73 which leads into a bore-back 74 with an internal diameter larger than the internal diameter of the pin 64.

The lower end of the segment 61 has a box portion which is similar to the box portion 66 illustrated in Figure 4, but in other examples may include another form of connection.

The connection 60 is single-shouldered; in the made-up connection 60 a pin shoulder 76 adjacent the stress relief groove 72 engages an end face 77 of the box 66. The end face of the pin 79 is unrestrained.

As with the connection 10 described above, when made-up the connection 60 achieves a fluid-tight seal by the contact between the pin shoulder 76 and the box end face 77. Also, at the make-up torque, at least the base of the pin 64 is in tension, and may be fractionally extended, increasing the friction between the first few thread turns of the pin 64 and box 66 at area 81. As will now be described, the friction between the pin 64 and the box 66 may be further increased by pulling a support member 84 into the pin 64.

The leading end of the pin 64 features a flared internal diameter with a frusto-conical surface 86 inclined 3-4 degrees to the primary connection axis 88. The support member 84 comprises a wedge-shaped sleeve and is located within the tapered portion of the pin 64. The support member 84 has a complementary inclined outer surface 90 and an internal surface 92 which is parallel the main connection axis 88. A lubricant is provided between the surfaces 86, 90 to control the friction factor between the surfaces.

As will be described, the setting tool 62 is configured to pull the support member 84 into the pin 64 and increase the frictional forces between the threads 68, 70. This pull is applied to the support member 84 by a collet 96 comprising spring fingers 98 which, in an extended configuration, as illustrated in Figure 4, engage a lower edge of the support member 84. The fingers 98 are maintained in the extended position by a shoulder 102 mounted on a threaded end portion of a rod 104 which extends through the coupling 60 to a setting tool actuation section 106. The collet 96 is axially movable along the lower end of the rod 104, with axial movement being limited by pins 108 which extend radially from the rod 104, and by the shoulder 102. The pins 108 may be aligned with slots 109 in a collet mounting collar 111 to allow the rod 104 and shoulder 102 to be moved downwards relative the collet 96 and the pins 108 to pass through the slots 109; if the rod 104 is then rotated to misalign the pins 108 and the slots 109, the pins 108 are trapped below the collar 111 and the collet 96 is held clear of the shoulder 102, allowing the collet fingers 98 to be deflected inwardly such that the collet 96 may pass through the support member 84.

The rod 104 is in two parts 104a, 104b joined by a threaded connection 110. The collet 96 is mounted on the lower part 104b and the upper part 104a extends through the saver sub box 75 and into the actuation section 106. The rod 104 is coupled to a piston 112 mounted in a cylinder 114 defined within an actuation section body 116. The body 116 is configured to sit on the saver sub box 75, receives a threaded end plug 118 and defines two hydraulic fluid ports 120, 122 which allow fluid to be passed into and from chambers 114a, 114b on opposite sides of the piston 112.

The illustrated connection 60 is useful in providing a volume, in this example within the boreback section 74, to accommodate the apparatus, downhole tool or device 65. With the apparatus 65 located in the volume 74, the connection 60 may be made up and secured, leaving double-shouldered connections 75 available for an operator to couple the resulting tool assembly into a drill string or bottom hole assembly (BHA).

To make-up the connection 60, the support member 84 is located in the end of the pin 64 and may be lightly tapped into place. The pin 64 and box 66 are then made up, for example by holding the box 66 stationary and rotating the pin 64 while permitting the pin 64 to axially advance into the box 66. The connection 60 will be torqued up to engage the pin shoulder 76 and the box end face 77 and put the base of the pin 64 under tension to increase the friction between the first few thread turns of the pin 64 and box 66, at area 81.

In this configuration the teeth of the threads 68, 70 will engage as illustrated in Figures 5 and 6 of the drawings. It will be noted that opposing upper flanks 120a, 120b of the threads are in contact, while the opposing lower flanks 122a, 122b and the thread roots 124 and crests 126 are spaced apart. The thread roots 124 are slightly narrower than the thread crest 126 (with reference to Figure 6, A > B). As noted above, the contact between the thread flanks on the connection being torqued up may only occur in the area adjacent the base of the pin 64.

The setting tool 62 is then mounted on the connection 60 and the rod 104 inserted through the box 75, the collet fingers 98 deflecting inwardly to pass through and beyond the support member 84. The rod 104 is then rotated to align the pins 108 and the slots 109, such that upward movement of the rod 104 will then bring the collet 96, supported on the collar 102, into contact with the lower edge of the support member 84.

With the actuation body 116 engaging the end of the box 75, hydraulic fluid is introduced into the cylinder volume 114b to pull on the rod 104 and translate the support member 84 further into the pin 64. The interaction of the pin surface 86 with the opposing support member surface 90 results in the end of the pin 64 being circumferentially extended and deformed radially outwards. This pushes the male thread 78 radially outwards relative to the female thread 80, causing both the upper and lower thread flanks 120a, 120b, 122a, 122b to engage and significantly increasing the contact area between the threads 78, 80. Of course this also increases the frictional contact between the threads 78, 80. This contact and friction will be in addition to the thread contact and friction adjacent the base of the pin 64 achieved when initially making up the threads 78, 80.

Any deformation of the male thread 78 is likely to increase the contact area and friction between the threads 78, 80. However, a more secure coupling will be achieved when both the upper and lower flanks engage. The degree of deformation necessary to achieve this will depend on the original thread clearance; a loose thread will require a greater degree of deformation than a tight thread. Also, for repeatability it is preferred that the deformation required is solely elastic, such that the thread 78 may recover its original form on removal of the support member 84.

The setting tool 62 may then be reconfigured to permit the collet 96 to collapse and pass through the support member 84, and the setting tool 62 removed from the end of the saver sub.

The resulting connection 60 is robust and secure, with the increased friction between the threads 78, 80 making inadvertent screwing off of the connection 60 unlikely. Further, on experiencing an elevated torque tending to advance the male thread 78 further into the female thread 80, the increased friction between the threads 78, 80 resists relative movement and protects the pin 64.

In this example the force applied to the support member 84 by the setting tool 62 is selected to create only recoverable elastic deformation in the pin 54 and support member 84, such that the connection 60 may subsequently be uncoupled and recoupled on multiple occasions. The setting force applied to the support member 84 may be selected based on a number of considerations, including connection configuration, connection dimensions, and material properties. In other circumstances, it may be desired to produce permanent plastic deformation.

To uncouple the connection 60, a tool (not shown) is inserted through the box 75 to push the support member 84 out of the pin 64. Alternatively, a tool similar to the setting tool 62 may be inserted from the other end of the segment 61 to pull the support member 84 out of the pin 64. The connection 60 may then be unscrewed.

Reference is now made to Figures 7 to 12 of the drawings, which are sectional views of different connections of the disclosure. Figure 7 shows a connection 160 which is similar in many respects to the connection 60 described above. However, the end of the pin 164 has been drilled to form eight equally-spaced bores 171 to increase the flexibility of the pin 164 and allow the pin 164 to be deformed radially outwards more easily when the support member 184 is pulled into the pin 164.

Figure 8 shows a connection 260 including conical or tapered pin and box coupling portions. In this example the coupling portions feature standard API threads. A support member 284 has been pulled or pushed into the pin 264 and the resulting deformation has increased the frictional contact between the threads 278, 280.

Figure 9 illustrates an alternative connection 360. Like the connection 60, Acme threads 378, 380 are provided on the pin 364 and box 366. However, there are a number of notable differences, for example the absence of a shoulder between the pin 364 and box 366; in this connection the sealing is achieved between smooth parallel surfaces 390 at the nose of the pin and the base of the box. The absence of a shoulder at the base of the pin 364 also facilitates provision of a smaller outer diameter and wall thickness in the saver sub 367 adjacent the base of the pin 364.

The support member 384 has a chamfered nose but otherwise is cylindrical and has an outer surface 388 that is parallel to the connection axis 392, as is the cooperating inner pin surface 389. However, the outer diameter of the support member 384 is slightly larger than the inner diameter of the pin 364, such that the support 384 is a tight press fit in the pin 364.

The connection 360 is made up by first rotating the coupling portions relative to one another to fully engage the threads 378, 380. However, the connection 360 is not torqued up. The support member 384 is then pulled into the pin 364 to the position as illustrated in Figure 9. This deforms a major portion of the pin 364, moving the male thread 378 radially outwards and into tighter contact with the female thread 380, such that the flanks of the threads engage. The deformation of the pin 364 also creates a fluid-tight seal between the surfaces 390.

Figure 10 illustrates a connection 460 which shares many features with the connection 360 described above, but which further includes an elastomer seal 490 in the pin nose for engaging an opposing surface of the box, to ensure a sealing contact between the coupling portions.

Reference is now made to Figure 11, which illustrates a single-shoulder connection 560 in which the support member 584 takes a different form. In particular, rather than creating radial deformation of the pin 564, the support member 584 engages an end face on the pin and creates a double-shouldered connection.

The connection includes Acme threads 578, 580 and stress relief grooves 572, 573 adjacent the pin shoulder and at the base of the female thread. The female thread 580 is longer than the pin male thread 578 and accommodates the externally threaded support member 584, which features an internal hex profile 585.

The connection 560 is initially made up by relative rotation of the pin 564 and box 566 to bring the pin shoulder 576 and box end face 577 into sealing contact and provide frictional engagement between the threads 578, 580 at the base of the pin. Next, a suitable tool is inserted into the connection 560 and the support member 584 is rotated to translate the member 584 along the thread 580 and into contact with the pin nose. The member 584 is torqued up to ensure a secure frictional contact between the threads of the member 584 and the box 566. The applied torque may also extend the base of the box 566 and compress the nose of the pin 564 sufficiently to increase the frictional contact between the pin and box threads at the pin nose.

The increased friction between the member 584 and the pin end face, and also between the threads adjacent the pin nose, provides a more secure connection which is resistant to both unscrewing and over rotation. In some respects the connection 560 may offer some of the advantages of a double-shouldered connection, but without the requirement for high manufacturing tolerances, and while providing a large throat 574 which may receive other tools or devices.

Reference is now made to Figures 12 and 13 of the drawings, which illustrate a connection 660 sharing a number of feature with the connection 560 described above. However, this connection 660 features an extended support member 684 which, in addition to an externally threaded portion 693, features a stabiliser portion 695 which is a close fit in the pin bore back 674. A relief port 697 extends through the support member 684 to allow venting of the stress relief groove 673.

Figure 13 also illustrates the setting tool 662 which is used to torque up the support member 684. The setting tool 662 includes a shaft 704 having a leading end profiled with a hex which may cooperate with the internal profile of the member 684. The shaft 704 extends through a removable stabiliser and thread protector 699 which is located in the end box connection 675 in the saver sub 671. A head 718 on the end of the shaft 704 includes blind bores 720 for receiving torqueing bars.

It will be apparent that the methods and apparatus described above are merely examples of the disclosure and that various modifications and improvements may be made thereto. It will further be apparent that the various individual features of the different examples have individual utility and may be employed in other examples without importing all of the features of the illustrated example.

The disclosure refers primarily to downhole connections and couplings; however the disclosure has utility in other applications. For example, the disclosure teaches an arrangement which provides the ability to lock two threaded parts together, which parts need not necessarily have been torqued up and may be locked at any convenient relative position. Thus, aspects of the disclosure may be useful as a spacer or locator and may facilitate accurate relative location or fitting of parts without requiring the parts to be machined to accurate tolerances. In other applications a bolt or stud provided with a bore could be locked to a nut or other coupling portion having a female thread by driving a slightly larger pin into the bore to lock the threads on the bolt and nut together. The bore could be restricted to an end portion of the bolt and a locking nut could be dimensioned or positioned using washers or shims to engage with the bolt end portion.

Claims

1. A method of fabricating a downhole assembly, the method comprising:

2. The method of claim 1, wherein configuring the support member deforms at least one of the coupling portions.

3. The method of claim 1 or 2, wherein configuring the support member radially deforms the male coupling portion.

4. The method of any preceding claim, wherein configuring the support member axially deforms at least one of the male coupling portion and the female coupling portion.

5. The method of any preceding claim, wherein configuring the support member deforms the male coupling portion and urges the male thread radially outwards relative to the female thread and into tighter engagement with the female thread.

6. The method of any preceding claim, wherein configuring the support member produces only elastic deformation of at least one of the coupling portions.

7. The method of any preceding claim, wherein configuring the support member produces plastic deformation of at least one of the coupling portions.

8. The method of any preceding claim, wherein configuring the support member comprises translating the support member relative to at least one of the coupling portions.

9. The method of any preceding claim, wherein configuring the support member comprises moving the support member axially relative to at least one of the coupling portions.

10. The method of any preceding claim, wherein configuring the support member comprises sliding the support member relative to at least one of the coupling portions.

11. The method of any preceding claim, further comprising providing a lubricant between contacting surfaces of the support member and a coupling portion.

12. The method of any preceding claim, wherein configuring the support member radially deforms at least one of the coupling portions and increases the interference and the frictional force between opposing contacting thread flanks.

13. The method of claim 12, wherein configuring the support member radially deforms at least one of the coupling portions whereby both the first and second thread flanks of at least some turns of the threads are in contact.

14. The method of any preceding claim, comprising locating the apparatus in a bore-back of the female coupling portion.

15. The method of any preceding claim, further comprising further configuring the support member whereby the coupling portions engage with a third frictional force lower than the second frictional force, to facilitate separating the coupling portions.

16. The method of any preceding claim, comprising making up and torqueing up the coupling portions before configuring the support member.

17. The method of any of claims 1 to 15, comprising making up but not torqueing up the coupling portions before configuring the support member.

18. The method of any preceding claim, comprising configuring the support member by at least one of pulling and pushing the support member into the male coupling portion.

19. The method of any preceding claims, comprising utilising a setting tool to configure the support member.

20. The method of claim 19, comprising translating the setting tool into the coupling and subsequently translating the setting tool out of the coupling.

21. The method of claim 19 or 20, wherein the setting tool transmits torque to the support member.

22. The method of claim 19, 20 or 21, wherein the setting tool transmits axial force to the support member.

23. The method of any preceding claim, comprising mounting the support member on the female coupling portion and translating the support member to engage an end face of the male coupling portion.

24. The method of any preceding claim, wherein the support member is thread and the method further comprises rotating the support member to translate the support member.

25. A downhole assembly comprising:

a first tubular member defining an internal volume for receiving downhole apparatus; a second tubular member for connection to the first tubular member;

26. The assembly of claim 25, wherein in the second configuration the support member deforms at least one of the coupling portions.

27. The assembly of claim 25 or 26, wherein in the second configuration the support member radially deforms the male coupling portion.

28. The assembly of any of claims 25 to 27, wherein in the second configuration the support member axially deforms at least one of the male coupling portion and the female coupling portion

29. The assembly of any of claims 25 to 28, wherein in the second configuration the support member deforms the male coupling portion and urges the male thread radially outwards relative to the female thread and into tighter engagement with the female thread.

30. The assembly of any of claims 25 to 29, wherein in the second configuration the support member produces only elastic deformation of at least one of the coupling portions.

31. The assembly of any of claims 25 to 29, wherein in the second configuration the support member produces plastic deformation of at least one of the coupling portions.

32. The assembly of any of claims 25 to 31, wherein the support member comprises a collar.

33. The assembly of any of claims 25 to 32, wherein the support member has an external surface which is inclined relative to a main axis of the tubular members.

34. The assembly of any of claims 25 to 32, wherein the support member has an external surface which is parallel to a main axis of the tubular member and is parallel to an opposing internal surface of the male coupling portion.

35. The assembly of any of claims 25 to 34, wherein an internal surface of the male coupling portion is inclined relative to a main axis of the tubular members.

36. The assembly of any of claims 25 to 35, wherein opposing surfaces of the support member and the male coupling portion comprise a shallow taper.

37. The assembly of any of claims 25 to 36, wherein the support member has an external surface which, at least in the first configuration, has an outer diameter larger than an internal diameter of an opposing internal surface of the male coupling portion.

38. The assembly of any of claims 25 to 37, wherein the support member is configured to be translatable relative to at least one of the coupling portions between the first and second configurations.

39. The assembly of claim 38, wherein the support member is configured to be movable axially relative to at least one of the coupling portions.

40. The assembly of any of claims 25 to 39, wherein the support member is configured for sliding relative to the coupling body.

41. The assembly of any of claims 25 to 40, wherein a lubricant is provided between contacting surfaces of the support member and a coupling portion.

42. The assembly of any of claims 25 to 41, wherein the support member has a thread configured to engage with a thread provided on the coupling body.

43. The assembly of any of claims 25 to 42, wherein at least one of the male and female threads has a thread angle of greater than zero, whereby radial deformation of at least one of the coupling portions increases the interference and the frictional force between opposing contacting thread flanks.

44. The assembly of claim 43, wherein thread angle is less than 40 degrees.

45. The assembly of any of claims 25 to 44, wherein in the first configuration opposing first flanks of at least some of the turns of the threads are in contact with opposing second flanks.

46. The assembly of any of claims 25 to 45, wherein in the second configuration both the first and second thread flanks of at least some of the turns of the threads are in contact.

47. The assembly of any of claims 25 to 46, wherein the threads are Acme threads.

48. The assembly of any of claims 25 to 47, wherein tubular members form part of a bottom hole assembly (BHA).

49. The assembly of any of claims 25 to 48, wherein tubular members form part of a drill string section.

50. The assembly of any of claims 25 to 49, wherein the female coupling portion is a box connection and the male coupling portion is a pin connection.

51. The assembly of claim 50, wherein the box connection has a throat for receiving the downhole apparatus and an internal diameter of the throat is larger than an internal diameter of the pin connection.

52. The assembly of claim 51, wherein the internal diameter of the throat is less than the smallest minor diameter of the female thread of the box connection.

53. The assembly of any of claims 25 to 52, wherein the coupling is a shouldered coupling.

54. The assembly of any of claims 25 to 53, further comprising a setting tool for configuring the support member.

55. The assembly of claim 54, wherein the setting tool is configured to pull or push the support member into the male coupling portion.

56. The assembly of claim 54 or 55, wherein the setting tool is configured to push the support member into the male coupling portion.

57. The assembly of claims 54, 55 or 56, wherein the setting tool comprises a retractable portion for engaging the support member.

58. The assembly of any of claims 54 to 57, wherein the setting tool is configured to apply torque to the support member.

59. The assembly of any of claims 54 to 58, wherein the setting tool comprises a formation configured to engage the support member.

60. The assembly of any of claims 25 to 59, wherein the support member is configured for mounting to the female coupling portion and to be translatable to engage an end face of the male coupling portion.

61. The assembly of claim 60, wherein the support member has an external male thread and the female coupling portion has a cooperating internal second female thread.

62. The assembly of claim 61, wherein the second female thread is a continuation of the female thread provided for coupling with the male thread of the male coupling portion.

63. The assembly of claim 61, wherein the second female thread is a different thread from the female thread provided for coupling with the male thread of the male coupling portion.

64. The assembly of claim 63, wherein the second female thread is at least one of a different thread form, a different pitch, and the opposite hand to the female thread provided for coupling with the male thread of the male coupling portion.

65. The assembly of any of claims 25 to 64, wherein the second tubular member is a saver sub.

66. The assembly of any of claims 25 to 65, wherein the second tubular member has a further coupling portion on the other end of the member.

67. The assembly of claim 66, wherein the further coupling portion on the other end of the second tubular member is one of a pin and a box.

68. The assembly of any of claims 25 to 67, further comprising a third tubular member for coupling to the other end of the first tubular member.

69. The assembly of claim 68, wherein the third tubular member is a saver sub.

70. The assembly of any of claims 25 to 69, wherein the first tubular member comprises a coupling portion on the other end of the member.

71. The assembly of any of claims 25 to 70, wherein the coupling portions include smooth parallel sealing surfaces.

72. The assembly of claim 71, wherein the sealing surfaces are provided at a nose of the male coupling portion and at a base of the female coupling portion.

73. The assembly of any of claims 25 to 72, wherein the support member is cylindrical and has an outer surface that is parallel to a main axis of the tubular members.

74. The assembly of any of claims 25 to 73, wherein an outer diameter of the support member is larger than an inner diameter of the male coupling portion, such that the support member is a tight press fit in the male coupling portion.

75. The assembly of any of claims 25 to 74, wherein at least one of the coupling portions comprises a seal member for engaging an opposing surface of the other coupling portion.

76. The assembly of claim 75, wherein the seal member comprises an elastomer seal member.

77. A coupling comprising:

a coupling body comprising a female coupling portion and a male coupling portion, the female coupling portion having an internal female thread and the male coupling portion comprising an external male thread for cooperating with the female thread ; and a support member for location within the coupling body and being configurable in a first configuration and in a second configuration, in the first configuration the support member permitting the male and female threads to be made up and engage with a first frictional force and in the second configuration the support member deforming at least one of the coupling portions such that the male and female threads engage with a second frictional force higher than the first frictional force.

78. A coupling method comprising:

79. A coupling method comprising:

80. A coupling comprising:

81. A tubular coupling comprising:

a female coupling portion having an internal female thread;

a male coupling portion having: an external male thread for cooperating with the female thread, and an end face; and a support member for mounting to the female coupling portion and being translatable 5 to engage an end face of the male coupling portion.

82. A coupling method comprising:

coupling an external male thread provided on a male coupling portion with an internal female thread provided on a female coupling portion; and translating a support member mounted on the female coupling portion to engage a 10 leading end face of the male coupling portion.

Intellectual

Property

Office

Application No: GB1611501.6 Examiner: Mr Kevin Gartland