Plug assembly and method

Abstract

A plug assembly 10 comprises a plug member configured for location in an end portion of a pipe (P), a lock arrangement configured and / or operable to secure the plug assembly in the pipe, and a seal ar

Description

FIELD This relates to a plug assembly and method for sealing an end portion of a pipe. In particular, but not exclusively, this relates to a completion plug assembly and method for sealing an end portion of a pipe (e.g. a branch fitting or split tee fitting disposed around a section of a pipeline) in order that a valve (e.g. a hot tap valve) can be removed and replaced by a pipe closure (e.g. a blind flange or the like). BACKGROUND Transporting substances, in particular fluids, over distance is required in many industries, this typically being achieved via a system of pipes, tubes, pipe modules, pipelines, process pipework, and the like. In the energy industry, for example, pipelines are used in surface, subsurface and / or subsea environments to transport oil and / or gas, often over large distances. In some instances, it may be necessary or desirable to gain access to a “live” section of pipe via an opening formed through a wall of the pipe rather than from ends of the pipe, e.g. in order to isolate a section of the pipe for repair, replacement or to permit deployment of tooling into the pipe. This may be the case, e.g. where it is not possible or practical to access the ends of the pipe. However, access to a “live” section of pipeline containing substances, e.g. fluids, at pressure is technically challenging. One technique used for gaining access to a live section of pipe is known as hot tapping. Hot tapping involves the fitting of a branch connection, typically a split tee connection, around the section of the pipe in which the opening is to be formed. The branch connection may be welded or mechanically secured to the pipe. A valve, e.g. a slab valve, is then fitted to the branch connection. The valve is reconfigurable between a closed configuration in which a throughbore of the valve is closed and an open configuration in which the throughbore is open. When it is desired to form the opening in the wall of the pipe, the valve is configured in, or reconfigured to, its open configuration so as to permit a drilling tool, known as a hot tapping tool, to be deployed through the valve, the branch connection and the wall of the pipe so as to form the opening in the wall of the pipe. Once the opening has been formed, the drilling tool is removed and the valve arrangement reconfigured to its closed configuration, the valve subsequently controlling access to the pipe via the opening. Beneficially, hot tapping facilitates the creation of the opening in the wall of the pipe while maintaining pressure integrity. In some circumstances, it may be necessary or desirable to remove the valve and replace this with a permanent closure, such as a blind flange or the like. Conventionally, this involves locating a plug, known as a completion plug, in the pipe branch or flange connection below the valve. Once the completion plug, the valve can be removed and permanent closure installed. However, there are significant drawbacks with conventional completion plugs. For example, conventional completion plugs require external penetrations to the permanent flange, leaving long term integrity concerns. Moreover, conventional completion plugs employ a seal arrangement, typically a large section o-ring seal, sized to provide an interference fit during deployment. However, this seal arrangement has several limitations, including amongst other things: an increased risk of damage during deployment; a greater susceptibility to explosive decompression; and the requirement for a check valve, in some cases supplemented with a bypass in the completion plug, in order to prevent overload resulting from fluid pressure build-up during deployment. SUMMARY Aspects of the present disclosure relate to a plug assembly and method for sealing an end portion of a pipe. In particular embodiments, there is provided a completion plug assembly and method for sealing an end portion of a pipe (e.g. a branch fitting or split tee fitting disposed around a section of a pipeline) in order that a valve (e.g. a hot tap valve) can be removed and replaced by a pipe closure (e.g. a blind flange or the like). According to a first aspect, there is provided a plug assembly comprising: a plug member configured for location in an end portion of a pipe; a lock arrangement configured and / or operable to secure the plug assembly in said end portion of the pipe; a seal arrangement configured and / or operable to sealingly engage a wall of the end portion of the pipe, wherein the seal arrangement comprises one or more compression seal elements reconfigurable from a first configuration in which said one or compression seal elements are offset from the wall of the pipe to a second configuration in which said one or more compression seal elements sealingly engage the wall of the pipe, and wherein the plug assembly is configured and / or operable such that the lock arrangement is activated before the seal arrangement is actuated. In use, the plug assembly may be located in an end portion of a pipe, the lock arrangement being configured and / or operable to secure the plug assembly in the pipe, and the seal arrangement configured and / or operable to seal off the end portion of the pipe. The seal arrangement comprises one or more compression seal elements reconfigurable, in response to axial compression of said compression seal element, from a first configuration in which said compression seal element is offset from the wall of the pipe to a second configuration in which said compression seal element sealingly engages the wall of the pipe. The plug assembly provides a number of significant benefits over conventional techniques and equipment. For example, conventional completion plugs teach a seal which provides an interference fit with the pipe, since the seal provides the pressure integrity of the completion plug in operation. In contrast, the present plug assembly comprises a seal arrangement comprising one or more compression seal elements reconfigurable from a first configuration in which said one or more compression seal elements are offset from the wall of the pipe to a second configuration in which said one or more compression seal elements sealingly engages the wall of the pipe. Beneficially, the present plug assembly provides a plug which has a radial clearance between the seal arrangement and the pipe during deployment, such that fluid can bypass the plug assembly as it is deployed. The plug may be defined as a low profile plug. This obviates or at least mitigates damage to the plug assembly and / or the pipe that may otherwise occur due to a build-up of pressure ahead of the plug assembly as it is deployed. This in turn obviates the requirement to provide a check valve arrangement, external pressure equalisation port and / or bypass through the plug, such that the construction of the plug assembly is simplified. It will be recognised that, in the case of completion plugs, the plug seal forms a permanent, primary, pressure barrier that may be required for an extended time period, such that obviating the requirement for a check valve and / or bypass also obviates the associated failure modes with such components. Alternatively or additionally, the radial clearance also ensures that the plug assembly can be deployed in a wider range of pipes, since the seal arrangement may be adaptable to a range of pipe inner diameters. Alternatively or additionally, the radial clearance also means that the plug assembly can traverse bore irregularities and / or restrictions in the pipe which may otherwise inhibit or prevent deployment. The provision of compression seal elements provides a high integrity seal which can pass a reduced bore during deployment. The provision of compression seal elements provides a plug assembly which is capable of resisting pressure from either direction. In addition to being reconfigurable from the first configuration to the second configuration, the seal arrangement may be configured and / or operable to be reconfigured from the second configuration to the first configuration. Beneficially, this may facilitate retrieval and / or reuse of the plug assembly. Moreover, this may obviate or at least mitigate the risk that the plug assembly becomes stuck in a pipe having a ledge or other change in bore diameter or shape which would otherwise prevent a conventional plug, e.g. one having a seal configured to provide an interference fit with the pipe, from being removed. Alternatively or additionally, the present plug assembly provides a reduced susceptibility to explosive decompression in comparison to conventional plugs, since pressure acting on the one or more compression seals of the seal arrangement acts to enhance the seal with the wall of the pipe and / or are transferred into the pipe wall. The plug assembly may comprise or may be coupled to an actuation arrangement. The actuation arrangement may be configured and / or operable to activate the lock arrangement and / or the seal arrangement. In particular embodiments, the actuation arrangement may be configured and / or operable to both activate the lock arrangement and actuate the seal arrangement. Beneficially, the provision of an actuation arrangement which both activates the lock arrangement and actuates the seal arrangement, amongst other things provides a plug assembly with reduced complexity, thereby obviating the failure modes associated with separate lock activation and seal actuation arrangements. As described above, the plug assembly is configured and / or operable such that the lock arrangement is activated before the seal arrangement is actuated. More particularly, the actuation arrangement may be configured and / or operable such that, in use, the lock arrangement must be activated before the seal arrangement can be actuated. In use, and as will be described further below, the plug assembly may be deployed into the pipe. The lock arrangement may be activated to secure the plug assembly to the wall of the pipe, in particular embodiments to a preformed groove formed e.g. in the wall of the pipe or in a sandwich plate coupled to the end of the pipe. The seal arrangement may then be actuated to seal the pipe, the seal arrangement only being permitted to be actuated after the lock arrangement. This beneficially provides that the position at which the seal arrangement engages the pipe can be closely controlled. Moreover, this may ensure that the seal arrangement either engages a part of the pipe which has been configured to receive the seal arrangement, e.g. to provide enhanced sealing integrity, or alternatively ensures that the seal arrangement does not engage a part of the pipe which may otherwise provide reduced sealing integrity. Alternatively or additionally, this beneficially provides for failsafe operation since the lock arrangement must move fully into position before the seal arrangement can energise. As described above, the plug assembly comprises a plug member configured for location in the pipe. The plug member may define a mandrel or core of the plug assembly. The plug member may be configured and / or operable to support and / or carry the lock arrangement. The plug member may be configured and / or operable to support and / or carry the seal arrangement. The plug member may comprise a first part. The first part may be annular. For example, the first part may comprise or take the form of a plate or flange. The first part may comprise or define a pressure head. The plug member may comprise a second part. The second part may be annular. For example, the second part may comprise or take the form of a plate or flange. In particular embodiments, the second part may define a compression flange. The actuation arrangement may be formed in and / or by the plug member. For example, the plug member may be reconfigurable from a first configuration to a second, axially retracted, configuration. Reconfiguration of the plug member from its first configuration, which may be defined as an axially extended configuration, to its second, axially retracted, configuration may apply an axial compression force to the seal arrangement so as to reconfigure the seal arrangement from its first configuration (which in use is offset from the wall of the pipe) to its second configuration (which, in use, is engaged with the wall of the pipe). Reconfiguration of the plug member from its first configuration to its second, axially retracted, configuration may comprise the first part, e.g. pressure head, moving towards the second part, e.g. compression flange. The actuation arrangement may take any suitable means for inducing reconfiguration of the plug member from its first configuration to its second configuration. The actuation arrangement may for example but not exclusively comprise one or more of: a mechanical actuation arrangement; an electrical actuation arrangement; a fluid-powered actuation arrangement, e.g. a hydraulic or pneumatic actuation arrangement. In particular embodiments, the actuation arrangement may take the form of a fluid-powered actuation arrangement, more particularly a hydraulic actuation arrangement. In particular embodiments, the actuation arrangement may comprise a piston and cylinder arrangement, more particularly a hydraulic piston and cylinder arrangement. The piston may be formed in or coupled to, e.g. screwed to, the first part of the plug member. The cylinder may be formed in or coupled to, e.g. screwed to, the second part of the plug member. As described above, the plug assembly comprises a lock arrangement configured and / or operable to engage a wall of the pipe so as to secure the plug assembly in the pipe. The lock arrangement may be configured and / or operable to be reconfigured from a first configuration in which the lock arrangement is offset from the wall of the pipe to a second configuration in which the lock arrangement is engaged with the wall of the pipe, in particular embodiments the preformed groove in the wall of the pipe or in a sandwich plate coupled to the end of the pipe. In use, reconfiguration of the plug member from its first configuration to its second, axially retracted, configuration may apply an axial compression force to the lock arrangement so as to reconfigure the lock arrangement from its first configuration (which in use may be offset from the wall of the pipe) to its second configuration (which, in use, may be engaged with the wall of the pipe). Beneficially, the lock arrangement provides a radial clearance between the plug assembly and the pipe during deployment, advantages of which are described above. Moreover, where the plug assembly takes the form of a completion plug, the lock arrangement obviates the need for the external penetrations through the pipe wall required in conventional completion plugs, and so obviates or mitigates the integrity issues associated with conventional equipment. The lock arrangement may be self-energised. That is, the lock arrangement may be energised by the differential pressure acting over the lock arrangement. The lock arrangement may comprise or take the form of a taper lock. The lock arrangement may comprise a first lock member. The first lock member may comprise an inclined outer surface. The first lock member may comprise or take the form of a lock bowl. The first lock member may be configured for mounting on the plug member. In particular embodiments, the first lock member may be configured for mounting on the first part, e.g. pressure head, of the plug member. The first lock member may be configured and / or operable to move axially relative to the first part, e.g. pressure head, of the plug member. The lock arrangement may comprise one or more second lock members. Each of the one or more second lock members may comprise an inclined inner surface. The second lock members may comprise or take the form of lock dogs or segments. The lock arrangement may be configured and / or operable so that axial movement of the first lock member may urge the one or more second lock members radially outwards. The lock arrangement may be configured such that an ejection load on the plug assembly serves to increase the grip of the lock arrangement to the wall of the pipe, such that the lock arrangement may be self-energised. The second lock members may comprise a radially extending portion. The radially extending portion may be configured and / or operable to engage the preformed groove. The second lock members, e.g. the radially extending portions, may comprise or define a shear ring. The shear ring may be configured and / or operable to engage the preformed groove. In use, the plug member may be configured so that the second lock member(s) are urged radially outwards. The radially extending portion, e.g. shear ring, is urged into engagement with the preformed groove while portions of the second lock member either side of the radially extending portion, e.g. above and below the radially extending portion, are urged into engagement with the pipe bore. Beneficially, the ability to reconfigure the lock arrangement from its first configuration (which in use may be offset from the wall of the pipe) to its second configuration (which, in use, may be engaged with the wall of the pipe) means that plug assembly can be deployed passed a bore restriction and then activated to engage the radially extending portion, e.g. shear ring, with the groove; without requiring external penetrations in the pipe. Moreover, the shear ring is supported inside the preformed groove such that, in terms of forces, the shear ring is subject to shear forces only with no or substantially no bending forces, thereby removing bending failure modes. The second lock members, when activated, may have a gap between them. A block may be provided to the flange groove to provide anti-rotation, e.g. where a coupon pigging guide is installed. The plug assembly may comprise a stroke limiter. The stroke limiter may be configured and / or operable to limit the axial contraction of the plug member. The stroke limiter may comprise or take the form of a shoulder on the outer circumferential surface of the plug member, e.g. the first part and which may be configured and / or operable to engage a corresponding step in, e.g. formed in, the inner surface of the first lock member, e.g. lock bowl. Beneficially, the stroke limiter provides a controlled position of the pressure head so pigging guides can be mounted. As described above, the plug assembly comprises a seal arrangement comprising one or more seal elements configured and / or operable to sealingly engage the wall of the pipe, wherein the one or more seal element comprise or take the form of compression seal elements configured and / or operable to expand radially outwards when subject to axial compression. Beneficially, the provision of one or more compression seal elements means that the plug assembly is highly compliant to the pipe, facilitating leak tight sealing even in poor pipe bore conditions. The seal arrangement may be self-energised. That is, the seal arrangement may be energised by the differential pressure acting over the seal arrangement. The seal arrangement may comprise two or more of the compression seal elements. In particular embodiments, the seal arrangement may comprise two of the compression seal elements. The provision of two or more seal elements facilitates double block and bleed operation. The seal arrangement may comprise a first seal element. The first seal element may be disposed on and / or carried by the plug member, e.g. the first part of the plug member. The first seal element may be annular. The first seal element may comprise or take the form of an elastomeric seal element. The first seal element may provide a bi-directional seal with the wall of the pipe, i.e. the first seal element may provide a seal capable of withstanding a pressure differential acting in either a first direction or a second direction. The first seal element may be moveable relative to the plug member, e.g. the first part of the plug member. This permits the first seal element to be axially compressed and thus facilitates radial expansion of the first seal element into engagement with the wall of the pipe. The first seal element may be defined as an outboard and / or primary seal element, since in use it will be disposed closer to the pressure in the pipe. The seal arrangement may comprise a second seal element. The second seal element may be axially spaced from the first seal element. The second seal element may be disposed on and / or carried by the plug member. The second seal element may be annular. The second seal element may comprise or take the form of an elastomeric seal element. The second seal element may provide a bi-directional seal with the wall of the pipe, i.e. the second seal element may provide a seal capable of withstanding a pressure differential acting in either the first or second direction. At least one of the first seal element and the second seal element may be configured to be self-energising, e.g. on the plug member experiencing a pressure differential exceeding a selected threshold. The second seal element may be defined as an inboard and / or secondary seal element, since in use it will be disposed further from the pressure in the pipe than the first seal element. The second seal element may be moveable relative to the plug member, e.g. the first part of the plug member. This permits the second seal element to be axially compressed and thus facilitates radial expansion of the second seal element into engagement with the wall of the pipe. A seal ring may be provided. The seal ring may maintain axial separation of the first seal element and the second seal element. The seal ring may be disposed on and / or carried by the plug member, e.g. the first part of the plug member. The seal ring may be moveable relative to the plug member, e.g. the first part of the plug member. The plug assembly may comprise a fluid communication arrangement. The fluid communication arrangement may be configured and / or operable to communicate a fluid, e.g. a test fluid, to an annulus defined between the first and second seal elements when the first and second seal elements are engaged with the pipe. The annulus may be defined as a test annulus, since it may facilitate integrity testing of either or both of the first and second seal elements. The fluid communication arrangement may comprise a fluid communication passage in, e.g. formed in, the plug member, e.g. the first part of the plug member. The fluid communication passage may be configured and / or operable to communicate the fluid, e.g. the test fluid, to the annulus. Beneficially, the fluid communication arrangement permits either or both of the first and second seal elements to be independantly tested to, e.g. determine that a satisfactory seal exists prior to venting the set pressure and applying differential pressure over the plug member, i.e. the pressure differential cannot be created until the lock and seal are fully set. Alternatively or additionally, where the plug assembly provides a permanent or semi-permanent connection, such as when the plug assembly takes the form of a completion plug, the annulus could be used to provide a bleed port between the first and second seal elements. The plug assembly may comprise a retainer arrangement. The retainer arrangement may be configured and / or operable to lock the plug member in its second, axially, retracted configuration. The retainer arrangement may comprise a mechanical retainer arrangement. For example, the retainer arrangement may comprise one or more fasteners. In particular embodiments, the retainer arrangement may comprise one or more lock screws. However, it will be understood that other forms of retainer may be utilised. Beneficially, the retainer arrangement may permit future re-entry into the pipe. The plug assembly may comprise or may be coupled to a deployment system. The actuation arrangement may form or may form part of a deployment system for the plug assembly. The deployment system may be coupled to the plug member. In particular embodiments, the deployment system may be detachably coupled to the plug member. Beneficially, the ability to detach the deployment system may for example permit a blind flange to be fitted immediately behind the plug assembly. Moreover, the ability to detach the deployment system may permit the deployment system to be used with multiple plug members, reducing the equipment forming the permanent installation. The plug assembly may be configured and / or operable so that the deployment system may be detached while the seal arrangement and / or lock arrangement are maintained in their activated / actuated state. In particular embodiments, the deployment system may comprise or take the form of a fluid powered deployment system, and more particularly a hydraulic deployment system such as a hydraulic hot stab or the like. The deployment system may comprise a probe. The probe may be configured and / or operable to provide fluid communication to the plug member to at least one of: reconfigure the plug member from its first configuration to its second configuration so as to activate the lock arrangement and / or actuate the seal arrangement; apply a test pressure to the seal arrangement; and / or reconfigure the plug member from its second configuration to its first configuration so as to release the plug member. The probe may be configured to provide communication of pressurised fluid, e.g. hydraulic fluid, to the plug member. A fluid conduit arrangement may be formed or provided in the probe to facilitate fluid communication to the plug member. A fluid conduit (“set conduit”) may provide fluid communication to the plug member to facilitate reconfiguration of the plug member from its first configuration to its second configuration. A fluid conduit (“unset conduit”) may provide fluid communication to the plug member to facilitate reconfiguration of the plug member from its second configuration to its first configuration. A fluid conduit (“test conduit”) may provide fluid communication to the plug member to facilitate fluid communication to the annulus. A connection arrangement may be provided for connecting the deployment system, e.g. probe, to at least one flow line, such as a hydraulic flow line. The connection arrangement may, for example, comprise at least one port or fitting formed in, or disposed in, the deployment system, e.g. probe. The plug assembly may comprise, or may be provided in combination with, the at least one flow line. A probe housing may be configured for locating the probe into the plug member. For example, the probe may comprise or define a male portion for location in a corresponding female portion of the plug member. The probe may alternatively or additionally comprise or define a female portion for location on a corresponding male portion of the plug member. While it is envisaged that the probe and the plug member may be coupled when deployed into the pipe section, the provision of a male and / or female portion assists in locating the probe in the plug member where it is desired to reconnect the probe to the plug member where required. The configuration, shape or form of the male and / or female portion may also assist in ensuring the flow conduit or conduits of the probe are correctly aligned with the plug member. A coupling arrangement may be provided for coupling the deployment system e.g. probe, to the plug member. The coupling arrangement may be configured to detachably couple the deployment system, e.g. probe, to the plug member. The coupling arrangement may be of any suitable form and construction. The coupling arrangement may comprise a mechanical arrangement, e.g. a ball connection, finger connection, screw connection, bayonet connection or the like. In particular embodiments, the coupling arrangement is fluid actuated. For example, the coupling arrangement may comprise a fluid piston. In use, pressurised fluid may be directed via the fluid conduit arrangement to a piston chamber so as to urge the piston from a first position to a second position, in said second position the deployment arrangement being released or releasable from the plug member. According to a second aspect, there is provided a method of sealing an end portion of a pipe using the plug assembly of the first aspect. While in particular embodiments the plug assembly comprises or takes the form of a completion plug assembly, it will be understood that the plug assembly and / or method according to the present disclosure may be utilised in other applications, including amongst other things the sealing of an end portion (e.g. a flanged end portion) of a pipe forming part of a pipeline, process pipework, a pressure vessel or the like. The invention is defined by the appended claims. However, for the purposes of 5 the present disclosure it will be understood that any of the features defined above or described below may be utilised in isolation or in combination. For example, features described above in relation to one of the above aspects or below in relation to the detailed description below may be utilised in any other aspect, or together form a new aspect. 10 BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects will now be described with reference to the accompanying drawings, in which: Figure 1 shows a plug assembly for sealing an end portion of a pipe P; Figure 2 shows the plug assembly shown in Figure 1, with the second lock member set, before setting of the seal elements; Figure 2A shows an enlarged view of part of the plug assembly shown in Figure 2; Figure 3 shows the plug assembly shown in Figure 1, with the plug assembly set and still connected to the deployment system 58; Figure 3A shows an enlarged view of part of the plug assembly shown in Figure 2; and Figures 4 and 5 show removal of the deployment system. DETAILED DESCRIPTION OF THE DRAWINGS Referring first to Figure 1 of the accompanying drawings, there is shown a diagrammatic view of a plug assembly, generally denoted 10, for sealing an end portion of a pipe P. As shown in Figure 1, the illustrated plug assembly 10 takes the form of a completion plug assembly for sealing an end portion of a pipe (e.g. a branch fitting or split tee fitting disposed around a section of a pipeline) in order that a valve (e.g. a hot tap valve) can be removed and replaced by a pipe closure (e.g. a blind flange or the like). However, it will be understood that the plug assembly 10 may be utilised in other applications, including amongst other things the sealing of an end portion (e.g. a flanged end portion) of a pipe forming part of a pipeline, process pipework, a pressure vessel or the like. As shown in Figure 1, the plug assembly 10 comprises a plug member, generally denoted 12, configured for location in an end portion of the pipe P, a lock arrangement, generally denoted 14, configured and / or operable to secure the plug assembly 10 in the pipe P, and a seal arrangement, generally denoted 16, comprising seal elements 18, 20 configured and / or operable to sealingly engage a wall W of the pipe P. The seal elements 18, 20 take the form of compression seal elements reconfigurable, in response to axial compression of said compression seal element 18, 20, from a first configuration in which said compression seal elements 18, 20 are offset from the wall W of the pipe P to a second configuration in which said compression seal elements 18, 20 sealingly engage the wall W of the pipe P. In use, the plug assembly 10 is located in the end portion of the pipe P, the lock arrangement 14 being configured and / or operable to secure the plug assembly 10 in the pipe P, and the seal arrangement 16 configured and / or operable to seal off the end portion of the pipe P. The plug assembly 10 provides a number of significant benefits over conventional techniques and equipment. For example, conventional completion plugs teach a seal which provides an interference fit with the pipe, since the seal provides the pressure integrity of the completion plug in operation. In contrast, the plug assembly 10 comprises a seal arrangement 16 comprising compression seal elements 18, 20 reconfigurable from a first configuration in which said compression seal elements 18, 20 are offset from the wall W of the pipe P to a second configuration in which said compression seal elements 18, 20 sealingly engage the wall W of the pipe P. Beneficially, the plug assembly 10 permits a radial clearance between the seal arrangement 16 and the pipe P during deployment, such that fluid can bypass the plug assembly 10 as it is deployed. This obviates or at least mitigates damage to the plug assembly 10 and / or the pipe P that may otherwise occur due to a build-up of pressure ahead of the plug assembly 10 as it is deployed. This in turn obviates the requirement to provide a check valve arrangement and / or bypass through the plug, such that the construction of the plug assembly is simplified. It will be recognised that, in the case of completion plugs, the plug seal forms a permanent, primary, pressure barrier that may be required for an extended time period, such that obviating the requirement for a check valve and / or bypass also obviates the associated failure modes with such components. Alternatively or additionally, the radial clearance also ensures that the plug assembly 10 can be deployed in a wider range of pipes, since the seal arrangement 16 may be adaptable to a range of pipe inner diameters. Alternatively or additionally, the radial clearance also means that the plug assembly 10 can traverse bore irregularities in the pipe P which may otherwise inhibit or prevent deployment. In addition to being reconfigurable from the first configuration to the second configuration, the seal arrangement 16 is configured and / or operable to be reconfigured from the second configuration to the first configuration. Beneficially, this may facilitate retrieval and / or reuse of the plug assembly 10. Moreover, this may obviate or at least mitigate the risk that the plug assembly 10 becomes stuck in a pipe having a ledge or other change in bore diameter or shape which would otherwise prevent a conventional plug, e.g. one having a seal configured to provide an interference fit with the pipe, from being removed. Alternatively or additionally, the plug assembly 10 provides a reduced susceptibility to explosive decompression in comparison to conventional plugs, since pressure acting on the one or more compression seals 18, 20 of the seal arrangement 16 acts to enhance the seal with the wall W of the pipe P and / or are transferred into the pipe wall W. As shown in Figure 1, the plug assembly 10 comprises an actuation arrangement, generally denoted 22, configured and / or operable to activate the lock arrangement 14 and the seal arrangement 16. Beneficially, the provision of an actuation arrangement 22 which both activates the lock arrangement 14 and actuates the seal arrangement 16, amongst other things provides a plug assembly 10 with reduced complexity, thereby obviating the failure modes associated with separate lock activation and seal actuation arrangements. As will be described further below, the actuation arrangement 22 is configured and / or operable such that, in use, the lock arrangement 14 is activated before the seal arrangement 16 is actuated. In the illustrated plug assembly 10, the actuation arrangement 22 is configured and / or operable such that, in use, the lock arrangement 14 must be activated before the seal arrangement 16 can be actuated. In use, and as will be described further below, the plug assembly 10 is deployed into the pipe P. The lock arrangement 14 is activated to secure the plug assembly 10 to the wall W of the pipe P, in particular embodiments to a preformed groove G formed in the wall W of the pipe P or in a sandwich plate (not shown) coupled to the end of the pipe P. The seal arrangement 16 is then actuated to seal the pipe P, the seal arrangement 16 only being permitted to be actuated after the lock arrangement 14 has securely engaged the pipe P (in this case the groove G). This beneficially provides that the position at which the seal arrangement 16 engages the pipe P can be closely controlled. Moreover, this may ensure that the seal arrangement 16 either engages a part of the pipe P which has been configured to receive the seal arrangement 16, e.g. to provide enhanced sealing integrity, or alternatively ensures that the seal arrangement 16 does not engage a part of the pipe P which may otherwise provide reduced sealing integrity. As described above, the plug assembly 10 comprises a plug member 12 configured for location in the pipe P, the plug member 12 defining a mandrel or core of the plug assembly 10 configured and / or operable to support and / or carry the lock arrangement 14 and the seal arrangement 16. As shown in Figure 1, the plug member 12 comprises a first part 24, which in the illustrated plug assembly 10 comprises or takes the form of a pressure head, and a second part 26, which in the illustrated plug assembly 10 comprises or takes the form of a compression flange. As described above, the plug assembly 10 comprises an actuation arrangement 22 configured and / or operable to activate the lock arrangement 14 and the seal arrangement 16 and in the illustrated plug assembly 10 the actuation arrangement 22 is formed in and / or by the plug member 12. The plug member 12 is reconfigurable from a first configuration to a second, axially retracted, configuration. In use, reconfiguration of the plug member 12 from its first configuration, which may be defined as an axially extended configuration, to its second, axially retracted, configuration may apply an axial compression force to the lock arrangement 14 so as to reconfigure the lock arrangement 14 from its first configuration (which in use is offset from the wall W of the pipe P) to its second configuration (which, in use, is engaged with the wall W of the pipe P, (in this case the groove G). In the illustrated plug assembly 10, reconfiguration of the plug member 12 from its first configuration to its second, axially contracted, configuration also applies an axial compression force to the seal arrangement 16 so as to reconfigure the seal arrangement 16 from its first configuration (which in use is offset from the wall W of the pipe P) to its second configuration (which, in use, is engaged with the wall W of the pipe P). More specifically, reconfiguration of the plug member 12 from its first configuration to its second, axially retracted, configuration comprises moving the first part 24, i.e. pressure head, moving towards the second part 26, i.e. compression flange. The actuation arrangement 22 may comprise any suitable means for inducing reconfiguration of the plug member 12 from its first configuration to its second configuration. In the illustrated plug assembly 10, the actuation arrangement 22 takes the form of a fluid-powered actuation arrangement. More particularly, the actuation arrangement 22 comprises a piston 28 and cylinder 30. The piston 28 is coupled to, e.g. screwed to, the first part 24 of the plug member 12. The cylinder 30 is coupled to, e.g. screwed to, the second part 26 of the plug member 12. In use, pressurised fluid supplied to a piston chamber 32 (shown e.g. in Figures 2 and 2A) reconfigures the plug member 12 from its first configuration to its second configuration. As described above, the plug assembly 10 comprises lock arrangement 14 configured and / or operable to engage wall W of the pipe P so as to secure the plug assembly 10 in the pipe P. Beneficially, the lock arrangement 14 provides a radial clearance between the plug assembly 10 and the pipe P during deployment, advantages of which are described above. Moreover, in the plug assembly 10 obviates the need for the external penetrations through the pipe wall W required in conventional completion plugs, and so obviates or mitigates the integrity issues associated with conventional equipment. As shown in Figure 1, the lock arrangement 14 comprises a taper lock, the lock arrangement 14 comprising a first lock member 34, which in the illustrated plug assembly 10 takes the form of a lock bowl, and a plurality of second lock members 36, which in the illustrated plug assembly 10 take the form of lock dogs or segments. The first lock member 34 comprises an inclined outer surface 38 while the second lock members 36 each comprise an inclined inner surface 40. The lock arrangement 14 is configured and / or operable so that axial movement of the first lock member 34 urges the second lock members 36 radially outwards. As shown, the first lock member 34 is configured for mounting on the plug member 12, in particular first part 24, i.e. pressure head, of the plug member 12 and the first lock member 34 is configured and / or operable to move axially relative to the first part 24, i.e. pressure head, of the plug member 12. The lock arrangement 14 is configured such that an ejection load on the plug assembly 10 serves to increase the grip of the lock arrangement 14 with the wall W of the pipe P, such that the lock arrangement 14 is self-energised. The plug assembly 10 comprises a stroke limiter, generally denoted 42, configured and / or operable to limit the axial contraction of the plug member 12. In the illustrated plug assembly 10, the stroke limiter 42 takes the form of a shoulder 44 on the outer circumferential surface of the plug member 12, in particular the first part 24, and which is configured and / or operable to engage a corresponding step 46 in, e.g. formed in, the inner surface of the first lock member 34, i.e. lock bowl. As described above, the plug assembly 10 comprises a seal arrangement 16 comprising seal elements 18, 20 configured and / or operable to sealingly engage the wall W of the pipe P, wherein the seal elements 18, 20 take the form of compression seal elements configured and / or operable to expand radially outwards when subject to axial compression. Beneficially, the provision of compression seal elements 18, 20 means that the plug assembly 10 is highly compliant to the pipe P, facilitating leak tight sealing even in poor pipe bore conditions. The illustrated seal arrangement 16 comprises two compression seal elements in the form of first seal element 18 and second seal element 20. As shown, the first seal element 18 is annular and is disposed on and / or carried by the plug member 12, in particular the first part 24 of the plug member 12. The first seal element 18 provides a bi-directional seal with the wall W of the pipe P, i.e. the first seal element 18 provides a seal capable of withstanding a pressure differential acting in either a first direction or a second direction. The first seal element 18 is moveable relative to the plug member 12, i.e. the first part 24 of the plug member 12. This permits the first seal element 18 to be axially compressed and thus facilitates radial expansion of the first seal element 18 into engagement with the wall W of the pipe P. The first seal element may be defined as an outboard and / or primary seal element, since in use it will be disposed closer to the pressure in the pipe P. The second seal element 20 is similarly constructed, being annular and disposed on and / or carried by the plug member 12, in particular the first part 24 of the plug member 12, at an axially spaced location from the first seal element 18. The second seal element 20 also provides a bi-directional seal with the wall W of the pipe P. The first seal element 20 is also moveable relative to the plug member 12, i.e. the first part 24 of the plug member 12. This permits the first seal element 20 to be axially compressed and thus facilitates radial expansion of the second seal element 20 into engagement with the wall W of the pipe P. The second seal element 20 may be defined as an inboard and / or secondary seal element, since in use it will be disposed further from the pressure in the pipe P than the first seal element 18. As shown in Figure 1, a seal ring 48 may be provided between the first and second seal elements 18, 20, the seal ring 48 configured and / or operable to maintain axial separation of the first and second seal elements 18, 20. The seal ring 48 is disposed on and / or carried by the plug member 12, i.e. the first part 24 of the plug member 12 and is moveable relative to the plug member 12. The plug assembly 10 further comprises a fluid communication arrangement, generally denoted 50, configured and / or operable to communicate a fluid, e.g. a test fluid, to an annulus A defined between the first and second seal elements 18, 20 when the first and second seal elements 18, 20 are engaged with the pipe P. The annulus A may be defined as a test annulus, since it may facilitate integrity testing of either or both of the first and second seal elements 18, 20. The fluid communication arrangement 50 comprises a fluid communication passage 52 in, e.g. formed in, the plug member 12, i.e. the first part 24 of the plug member 12. The fluid communication passage 52 is configured and / or operable to communicate the fluid, e.g. the test fluid, to the annulus A. Beneficially, the fluid communication arrangement 50 permits either or both of the first and second seal elements 18, 20 to be independantly tested. Alternatively or additionally, since the plug assembly 10 takes the form of a completion plug and so provides a permanent or semi-permanent connection, the annulus A can be used to provide a bleed port between the first and second seal elements 18, 20. The plug assembly 10 further comprises a retainer arrangement, generally denoted 54, configured and / or operable to lock the plug member 12 in its second, axially, contracted, configuration. In the illustrated plug assembly 10, the retainer arrangement 54 comprises lock screws 56. However, it will be understood that other forms of retainer may be utilised. Beneficially, the retainer arrangement 54 permits future re-entry into the pipe P. As shown in Figure 1, the plug assembly 10 comprises a deployment system, generally denoted 58. In the illustrated plug assembly 10, the deployment system 58 is detachably coupled to the plug member 12. Beneficially, this permits the deployment system 58 to be used with multiple plug members, reducing the equipment forming the permanent or semi-permanent installation. In the illustrated plug assembly 10, the deployment system 58 takes the form of a fluid powered deployment system, more particularly a hydraulic hot stab or the like. As shown, the deployment system 58 comprises a probe 60 configured and / or operable to provide fluid communication to the plug member 12 to at least one of: reconfigure the plug member 12 from its first configuration to its second configuration so as to activate the lock arrangement 14 and / or actuate the seal arrangement 16; apply a test pressure to the seal arrangement 16; and / or reconfigure the plug member 12 from its second configuration to its first configuration so as to release the plug member 12. The probe 60 is configured to provide communication of pressurised fluid, e.g. hydraulic fluid, to the plug member 12. As shown, a fluid conduit (“set conduit”) 62 provides fluid communication to the plug member 12 to facilitate reconfiguration of the plug member 12 from its first configuration to its second configuration. A fluid conduit (“unset conduit”) 64 provides fluid communication to the plug member 12 to facilitate reconfiguration of the plug member 12 from its second configuration to its first configuration. A fluid conduit (“test conduit”) 66 provides fluid communication to the plug member 12 to facilitate fluid communication to the annulus A. As shown in Figure 1, the probe 60 comprises a male portion 68 configured for location in a female portion 70 in the plug member 12. Operation of the plug assembly 10 will now be described with reference in particular to Figures 1 and also now Figures 2, 2A, 3, 3A, 4 and 5 of the accompanying drawings. Figure 1 shows the plug assembly 10 in the process of being deployed and in an unset condition. As shown in Figure 1, when deployed the “unset” fluid conduit 58 is pressurised to prevent inadvertent activation. The probe 60 is rigidly connected to hydraulic cylinder 30 which is screwed onto the second part 26 (compression flange) of the plug member 12. The hydraulic piston 28 is fitted inside the hydraulic cylinder 30 and screwed onto the first part 24 (pressure head) of the plug member 12. Compression seal elements 18, 20 are mounted on the outside of the first part 24 of the plug member 12, separated by seal ring 48. The first lock member (lock bowl) 34 sits on top of the second seal element 20. The second lock members (dogs or segments) 36. In the illustrated plug assembly 10, the second lock members 36 together define a radially extending portion 72 in the form of a shear ringon their outer diameter which will be deployed into the groove G. Portions of the second lock members 36 either side of the radially extending portion 72, e.g. above and below the radially extending portion 72, are urged into engagement with the pipe P when the second lock members 36 are urged radially outwards. Beneficially, the ability to reconfigure the lock arrangement 14 from its first configuration (which in use may be offset from the wall W of the pipe P) to its second configuration (which, in use, may be engaged with the wall W of the pipe P) means that plug assembly 10 can be deployed passed a bore restriction and then activated to engage the radially extending portion 72, e.g. shear ring, with the groove G; without requiring external penetrations in the pipe P. Moreover, the radially extending portion 72 is supported inside the preformed groove G such that, in terms of forces, the radially extending portion 72 is subject to shear forces only with no or substantially no bending forces, thereby removing bending failure modes. The second lock members 36 are retained on the second part 26 with screws in slots (not shown). One or more springs 74 (in the illustrated plug assembly 10 in the form of garter springs 74) hold the second lock members (dogs or segments) 36 radially retracted when deployed. The radial clearance is defined to provide an area equivalent or larger than a traditional TOR pressure equalisation port to prevent any risk of differential pressure during deployment. Larger seals can be utilised if required to increase the radial clearance to pass a smaller bore valve. Figures 2 and 2A of the accompanying drawings shows the completion plug with the second lock member (dogs or segments) 36 set, before setting of the seal elements 18, 20. Hydraulic pressure in the “set” fluid conduit 62 pulls the first part (pressure head) 24 of the plug member 12 towards the second part (compression flange) 26. The plug assembly 10 is therefore positioned with the radially extending portion, e.g. shear ring 72 axially in line with the flange groove G prior to setting. The deployment system 58 is rigidly connected to the second part (compression flange) 26 for accurate measurement. As the pressure head rises, the first lock member (lock bowl) 34 pushes the second lock members (dogs or segments) 36 radially out to push the radially extending portion, e.g. shear ring, 72 into the groove G. This continues until the main body of the second lock members (dogs or segments) 36 engage with the wall W of the pipe P. The pressure head will be restricted from further movement if the main body of the second lock members (dogs or segments) 36 are not fully expanded to the wall W of the pipe P. The first part 24 of the plug member 12 must pass under the second lock members (dogs or segments) 36 to set the seal elements 18, 20 and the tight fit tolerance will prevent further compression if the second lock members (dogs or segments) 36 are not fully deployed. This ensures the radially extending portion, e.g. shear ring 72 is fully engaged with the groove G prior to a potential differential pressure. Once fully engaged, further differential pressure will compress the seal elements 18, 20. Figures 3 and 3A of the accompanying drawings show the plug assembly 10 set, and still connected to the deployment system 58. As shown, the first and second seal elements 18, 20 are compressed out to the wall of the pipe P by axial compression with the movement of the first part (pressure head) 24 of the plug member 12. Shoulder 44 and step 46 limit the stroke and load on the seal elements 18, 20. The annulus A can be pressurised or vented from outside the pressure boundary. Venting this void will allow a test of the first seal element 18 to full differential pressure and the second seal element to a reverse differential pressure, thereby verifying seal integrity. As the seal arrangement 16 can only be compressed with the lock arrangement 14 engaged, this pressure test also verifies the engagement and grip of the lock arrangement 14. At this time, the deployment system 58 can be vented to ambient pressure. The pipeline pressure acting on the first part (pressure head) 24 pushes it towards the engaged second lock members (dogs or segments) 36. This load passes through the seal elements 18,20, further compressing until the stroke limiter 42 is reached. The load then passes through the taper interface between the first lock member (lock bowl) 34 and the second lock members (dogs or segments) 36 to drive the second lock members (dogs or segments) 36 radially against the wall W of the pipe P. The result is than the plug assembly 10 will be self-energised in the case of loss of hydraulic set pressure. The loading on the second lock members (dogs or segments) 36 maintains contact with the pipe P to ensure the radially extending portion, e.g. shear ring, 72 is seeing purely shear load. Once the pressure in the deployment system 58 is vented, the annulus pressure can be raised to 1.1 times the pipeline pressure to formally test the second seal element 20 in the correct direction. If for any reason a seal test fails, the plug assembly 10 can be unset by balancing the pressure and applying pressure to the “unset” fluid conduit 64. The plug assembly 10 can then be recovered and redressed. Figures 4 and 5 of the accompanying drawings show the step of removing the deployment system 58. Once the plug assembly 10 is set, pressure vented and seals verified the deployment system 58 can be removed. First, the hydraulic “set” conduit 62 is vented. Then the probe 60 is disconnected and retracted through the valve V. The valve V and deployment system can be removed, leaving access to the back of the plug assembly 10 and end portion of the pipe P, which as shown takes the form a weld neck flange. Locking bolts 76 can then be torqued to allow the removal of the probe 60. The plug assembly 10 will remain actuated by self-energisation. The annulus A can be protected by a POCV or valve if required. The POCV could use the hydraulic set feed as a pilot as this will be vented at disconnect. It will be recognised that various modifications may be made without departing from the scope of the invention as defined in the claims. 5 For example, additional actuation options include: a lock hydraulic set with a pilot operated check valve; or a ratchet on the hydraulic piston.

Claims

1. A plug assembly comprising:a plug member configured for location in an end portion of a pipe;a lock arrangement configured and / or operable to secure the plug assembly in said end portion of the pipe;a seal arrangement configured and / or operable to sealingly engage a wall of the end portion of the pipe,wherein the seal arrangement comprises one or more of compression seal elements reconfigurable from a first configuration in which said one or more compression seal elements are offset from the wall of the pipe to a second configuration in which said one or more compression seal elements sealingly engage the wall of the pipe,and wherein the plug assembly is configured and / or operable such that the lock arrangement is activated before the seal arrangement is actuated.

2. The plug assembly of claim 1, wherein the plug assembly comprises or takes the form of a completion plug.

3. The plug assembly of claim 1 or 2, wherein the plug assembly comprises or is coupled to an actuation arrangement configured and / or operable to activate the lock arrangement and / or actuate the seal arrangement, wherein the actuation arrangement is configured and / or operable such that, in use, the lock arrangement is activated before the seal arrangement is actuated.

4. The plug assembly of claim 1, 2 or 3, wherein the plug member is reconfigurable from a first configuration to a second, axially retracted, configuration.

5. The plug assembly of claim 4, wherein the plug member comprises:a first part; anda second part, andwherein reconfiguration of the plug member from its first configuration to its second, axially retracted, configuration moves the first part towards the second part.

6. The plug assembly of claim 4 or 5, wherein at least one of:said reconfiguration of the plug member from its first configuration to its second configuration applies an axial compression force to the lock arrangement so as to activate the lock arrangement; andsaid reconfiguration of the plug member from its first configuration to its second configuration applies an axial compression force to the seal arrangement so as to actuate the lock arrangement.

7. The plug assembly of any preceding claim, wherein the lock arrangement is configured and / or operable to be reconfigured from a first configuration in which the lock arrangement is offset from the wall of the pipe to a second configuration in which the lock arrangement is engaged with the wall of the pipe.

8. The plug assembly of any preceding claim, wherein the lock arrangement comprises or takes the form of a taper lock, the lock arrangement comprising:a first lock member, e.g. a lock bowl, comprising an inclined outer surface; and one or more second lock members, e.g. lock dogs or segments, comprising an inclined inner surface for engaging the inclined outer surface of the first lock member, such that axial movement of the first lock member urges the one or more second lock members radially outwards.

9. The plug assembly of claim 8, wherein one or more of the second lock members comprises a radially extending portion, wherein the radially extending portion is configured and / or operable to engage a preformed groove in the pipe when the second lock member is urged radially outwards.

10. The plug assembly of claim 8 or 9, wherein the radially extending portions comprise or define a shear ring.

11. The plug assembly of claim 9 or 10, wherein portions of the second lock member either side of the radially extending portion, e.g. above and below the radially extending portion, are urged into engagement with the pipe bore when the second lock member is urged radially outwards.

12. The plug assembly of any preceding claim, wherein one or more of the seal elements comprises or takes the form of a bi-directional seal element.

13. The plug assembly of any preceding claim, wherein the seal arrangement and / or the lock arrangement are adapted to be self-energising.

14. The plug assembly of any preceding claim, wherein the one or more seal elements of the seal arrangement comprise a first seal element and a second seal element.

15. The plug assembly of claim 14, comprising a fluid communication arrangement configured and / or operable to communicate a fluid, e.g. a test fluid, to an annulus defined between the first and second seal elements when the first and second seal elements are engaged with the pipe.

16. The plug assembly of claim 4, or claims 5 to 15 when dependent on claim 4, wherein the plug assembly comprises a retainer arrangement configured and / or operable to lock the plug member in its second, axially, retracted configuration.

17. The plug assembly of any preceding claim, wherein the plug assembly comprises or is coupled to a deployment system.

18. The plug assembly of claim 17, wherein the deployment system is coupled, e.g. detachably coupled, to the plug member.

19. The plug assembly of claim 17 or 18, wherein the deployment system comprises or takes the form of a fluid powered deployment system.

20. The plug assembly of claim 17, 18 or 19, wherein the deployment system comprises a probe.

21. The plug assembly of claim 22, wherein the probe is configured and / or operable to provide fluid communication to the plug member.

22. The plug assembly of claim 21, wherein the probe is configured and / or operable to provide fluid communication to the plug member to at least one of:reconfigure the plug member from its first configuration to its second configuration so as to activate the lock arrangement and / or actuate the seal arrangement; and / orreconfigure the plug member from its second configuration to its first configuration so as to release the plug member.

23. The plug assembly of claim 21 or 22, wherein the probe is configured and / or operable to provide fluid communication to the plug member so as to apply a test pressure to the seal arrangement.

24. The plug assembly of any one of claims 20 to 23, wherein at least one of:the probe comprises or defines a male portion for location in a corresponding female portion of the plug member;the probe comprises or defines a female portion for receiving a corresponding male portion of the plug member.

25. A method of sealing an end portion of a pipe using the plug assembly of any preceding claim.

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