Purge System
A well intervention system (10) which is adapted to be coupled to a subsea wellhead assembly (12) is described. The subsea wellhead assembly has a wellhead, a subsea tree (14) coupled to the wellhead and a well control package, having a plurality of well control valves, coupled to the subsea tree. The intervention system (10) comprises a vessel (44) for storing and deploying wireline tooling, first fluid communication means extending between the vessel and a purging fluid supply (57) and second fluid communication means extending between the vessel and the well control package at a location above at least one well control valve. In use, purging fluid applied to the vessel via the first fluid communication means displaces fluid from the vessel into the second fluid communication means and into the well control package. Embodiments of the invention are described.
The present invention relates to a purge system, and in particular to a purge system for use in, for example, subsea wireline intervention applications and apparatus. The present invention also relates to a subsea intervention system incorporating a purge system, and to a well intervention method.
BACKGROUND TO THE INVENTIONIn the oil and gas exploration and production industry many well operations require the use of tools which are deployed (and in some cases operated/controlled) into a well on wireline, such as electrically conducting wireline or non-conducting slickline or the like. Wireline operations may include well intervention procedures such as well logging to establish wellbore and formation conditions of a depleting well, or remedial operations, such as re-perforating and water shut-off, for instance. Numerous tools exist for use in various wireline procedures and it is conventionally the case that a number of these tools are stored on site to be used as required.
The past decade has seen the use of subsea production systems become the method of choice for exploiting offshore oil and gas fields. In the formative era of subsea production systems, it was envisaged that intervention operations would be conducted from a drilling rig or ship via a marine riser and Blow Out Preventer (BOP). Accordingly, with such an arrangement the required wireline intervention tools would be selected, made-up into a tooling string and subsequently deployed from the drilling rig or ship via the marine riser and into the well. However, the present Applicant has proposed the use of a self-contained well intervention system which can be deployed from a lightweight vessel and coupled directly to a wellhead located on the seabed, which offers significant advantages. Such a self-contained well intervention system is disclosed in Applicant's co-pending International Patent Application Publication No. WO 2004/065757 and UK Patent Application No. 0414765. The Applicant's intervention system includes a storage chamber within which a number of intervention and other wireline deployable tools may be located. Each tool may be individually selected and subsequently coupled to a wireline for deployment directly through the wellhead and into the well.
The preferred form of the Applicant's self-contained well intervention system is exposed to well fluid when in operation. Accordingly, consideration must be given as to how to contain and control this well fluid when the intervention system is to be detached from the wellhead and retrieved to the surface. If the well fluid is to be contained within the intervention system and retrieved to surface then suitable equipment must be provided at surface level to safely extract the well fluid from the intervention system, and subsequently store and/or dispose of this. This is particularly complex as the well bore fluid will conventionally contain a proportion of gas and as such the surface level equipment must be capable of safely accommodating the removal and safe disposal of multi-phase well fluids, which can be hazardous in atmospheric conditions. Furthermore, the required additional surface equipment will require a dedicated assignment of plant space which on an offshore rig or drilling/production vessel is at a premium.
Prior art reference WO 01/25593 A1 discloses a subsea lubricator device which may purge fluids from a tool housing and into a production flow line. The lubricator device of the WO 01/25593 A1, reference is required to contain well fluids during wireline operations as wireline extends from surface level and into the lubricator to engage a wireline tool to be deployed in the well. However, in Applicant's self contained well intervention system the wireline is provided entirely at a subsea location and is exposed to well conditions. Accordingly, the Applicant's intervention system does not require use of a lubricator. The device of the WO 01/25593 A1 reference includes a tool housing secured to a Blow Out Preventor (BOP) which in turn is secured to a Christmas tree. The BOP includes a number of valves for use in fluid control. A bypass line is provided between the tool housing and a connector means which is used to secure the BOP to the Christmas tree such that the valves in the BOP may be bypassed. Fluid is displaced from the tool housing though the bypass line and into the connector means. In this way the purged fluid bypasses the BOP. A separate system is provided to displace fluids from the BOP.
It is among the objects of the present invention to obviate or at least mitigate the above mentioned and other disadvantages by providing a system for use in purging a fluid from an apparatus adapted to be coupled to a subsea wellhead.
SUMMARY OF THE INVENTIONAccording to a first aspect of the present invention, there is provided a well intervention system adapted to be coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means; said system comprising:
a vessel for use in storing and deploying wireline tooling, said vessel adapted to be exposed to well fluids when in use;
first fluid communication means adapted to extend between a purging fluid supply and the vessel; and
second fluid communication means adapted to extend between the vessel and the well control package at a location above at least one of the well control valve means;
wherein, in use, purging fluid supplied to the vessel via the first fluid communication means displaces fluid from the vessel into the second fluid communication means and into the well control package.
The intervention system of the present invention is therefore adapted to simultaneously purge fluid from the vessel and at least a portion of the well control package. The present invention therefore eliminates the requirement to provide separate purging apparatus, or at least minimises the extent to which a separate purging apparatus is required, in order to purge fluid contained within the well control package. Advantageously, once the fluid within the vessel has been displaced, the intervention system and optionally the well control package may be detached from the wellhead assembly and returned to the surface.
Preferably, the system, in use, directs the displaced fluid from the vessel towards a production fluid outlet defined in the subsea tree. Accordingly, the purged fluids may be flowed to surface via a conventional production marine riser and thus handled using conventional production fluid handling equipment. This arrangement therefore eliminates the requirement to provide additional fluid handling equipment at surface level which is dedicated to handling purged fluids. Preferably, the displaced fluids are directed through a fluid passage within the wellhead assembly to which the vessel is coupled. The fluid passage within the wellhead assembly may be defined by a production fluid bore which communicates with the production fluid outlet of the subsea tree. The fluid passage within the wellhead assembly may be defined by a production fluid bore and a subsea tree crossover flow line, wherein the crossover flow line communicates with the production fluid outlet.
Alternatively, the displaced fluid may be directed into the well. Alternatively further, the displaced fluid may be flowed to surface via a dedicated flow path.
In one embodiment of the present invention, the purging fluid supply may be a container or vessel located at surface level, and the first fluid communication means may extend from the container at the surface to the vessel. In an alternative embodiment of the present invention, the purging fluid supply may be a container or vessel located subsea, and preferably adjacent or in close proximity to the vessel and wellhead. In this embodiment the purging fluid supply may be mounted on a skid, and advantageously on a Remotely Operated Vehicle (ROV) skid which would permit dynamic positioning and control of the location of the purging fluid supply. Alternatively, the purging fluid supply may be directly or indirectly mounted on the vessel.
Preferably, the supply of purging fluid comprises a known volume of purging fluid, which may be selected to displace the required volume of fluid from the vessel. Advantageously, the purging fluid supply comprises sufficient fluid to achieve at least one, and preferably a plurality of purging operations.
The purging fluid may be glycol or a suitable water and glycol mixture. Advantageously, the glycol assists to prevent or substantially minimise the formation of hydrates. It should be noted that other hydrate inhibiting fluids such as methanol or MEG (Methyl Ethyl Glycol) may alternatively be used.
Preferably, the vessel defines a central bore which in use extends towards the wellhead assembly and which is coaxially aligned with a throughbore of the wellhead assembly when the intervention system is coupled thereto.
Preferably, the vessel of the intervention system comprises a tool storage chamber. Conveniently, the tool storage chamber comprises a plurality of tool storage clamping means capable of retaining a respective tool in a storage position and selectively moving said tool to a deployment position where the tool may be coupled and decoupled to a wireline connection tool from above. Advantageously, the tool storage chamber defines a portion of the central bore of the vessel. Conveniently, a tool when located in the deployment position by a tool storage clamping means may be substantially aligned with the central bore of the vessel such that said tool will also be substantially aligned with the throughbore of the wellhead assembly. In this way the tool may be readily deployed through the wellhead assembly and into the well bore.
In a preferred embodiment the vessel of the well intervention system further comprises a wireline winch assembly, such as that disclosed in Applicant's co-pending UK Application no. 0419781.0. Advantageously, the winch assembly comprises a which housing within which a wireline winch drum is located and mounted about the central bore of the vessel. Preferably, the winch assembly is located above the tool storage chamber. Beneficially, the winch housing defines a winch cavity within which the winch drum is located wherein, in use, wireline from the winch drum exits the winch cavity, extends upwardly through a first tube or riser, passes through an upper sheave, and extends downwardly through a second tube or riser and into the central bore of the vessel. Accordingly, the winch cavity, in use, is also exposed to well fluids via the central bore and first and second tubes.
Preferably, the first fluid communication means is adapted to be coupled to the vessel at a position below the tool storage chamber and the winch assembly. In this way, purging fluid may be passed through the vessel central bore, tool chamber and winch cavity to displace well fluid therefrom. Advantageously, a crossover fluid conduit is defined between the central bore of the vessel and the winch cavity such that the purging fluid may flow from the central bore and into the winch cavity to displace well fluids therefrom.
Preferably, the second fluid communication means is adapted to extend between an upper portion of the vessel, above the tool storage chamber and the winch assembly, and the well control package. In this way, the second fluid communication means, in use, directs fluid from an upper portion of the vessel and into the wellhead assembly at a location which is located below the vessel. More preferably, the second fluid communication means is adapted to extend between the upper sheave of the winch assembly and the wellhead assembly.
Preferably, the intervention system further comprises flow isolation means for controlling fluid flow.
Advantageously, the system comprises a primary isolation means for removing communication with the well bore. The primary isolation means may be a sub-surface safety valve (SSSV) located within the wellhead. The SSSV is well known in the art.
Preferably, the system comprises well fluid isolation means for selectively preventing the flow of well fluid towards the vessel and through the production fluid
outlet of the subsea tree. In one embodiment of the present invention, the well fluid isolation means may comprise a single valve means, such as a ball valve or a bore plug or the like. The single valve means may be a production master valve. In this embodiment, the single valve means, in use, selectively prevents the flow of well fluid both towards the vessel and through the production fluid outlet of the subsea tree. Conveniently, this particular arrangement is advantageously suitable for use in purging a vessel of an intervention system which is adapted to be coupled to a wellhead assembly incorporating a dual bore subsea tree configuration, which is well known in the art. Such a dual bore subsea tree is conventionally known as a vertical subsea tree.
In an alternative embodiment, the well fluid isolation means may comprise first isolation means for selectively preventing the flow of well fluids towards the vessel, and second isolation means for selectively preventing the flow of well fluids through the production fluid outlet of the subsea tree. Advantageously, the first and second isolation means each may comprise valve means such as a ball valve or the like, or may alternatively comprise a plug or the like. In a preferred embodiment the first isolation means is a production master valve and the second isolation means is a tubing hanger plug. Conveniently, this particular arrangement is advantageously suitable for use for purging a vessel of an intervention system which is adapted to be coupled to a wellhead assembly incorporating a single bore subsea tree configuration, which is well known in the art. Such a single bore subsea tree is conventionally known as a horizontal subsea tree.
In preferred embodiments of the present invention the well fluid isolation means is provided in the subsea tree of the wellhead assembly to which the intervention system is coupled. Advantageously, the well fluid isolation means of the present invention may comprise existing valve means within the subsea tree such that the present invention may advantageously utilise existing wellhead assembly configurations.
Preferably, the system comprises well annulus fluid isolation means adapted to selectively prevent fluid flow either into the annulus from the intervention system or wellhead assembly, or alternatively from the annulus and into the wellhead assembly and/or intervention system. Advantageously, the well annulus fluid isolation means may be provided in the wellhead, assembly, and preferably in the subsea tree. Beneficially, the annulus fluid isolation means may comprise existing valve means within the wellhead assembly.
Preferably, the system of the present invention comprises vessel isolation means adapted for use in selectively isolating the vessel of the intervention system from the wellhead assembly to which it is coupled. Advantageously, in use, the vessel isolation means may prevent purging fluid provided to the vessel via the first fluid communication means from bypassing the vessel and flowing towards the wellhead assembly. Additionally, the vessel isolation means, in use, advantageously prevents fluid purged from the vessel from re-entering the vessel via the second fluid communication means. The vessel isolation means may comprise valve means such as a ball valve or the like. Advantageously, the vessel isolation means may be positioned within the wellhead assembly. Preferably, the vessel isolation means is positioned within the well control package of the wellhead assembly. Preferably also, the vessel isolation means comprises existing valve means within the wellhead assembly to which the vessel to be purged is coupled. Alternatively, the vessel isolation means may be provided within the vessel to be purged.
Advantageously, the system may further comprise closure means for retaining purging fluid within the vessel once purging has taken place, such that the closure means may be activated when the intervention system is to be separated from the wellhead assembly and returned to surface.
Preferably, the system of the present invention comprises non-return valve means for preventing the return of purged fluid back into or towards the vessel. Advantageously, in one embodiment the non-return valve means is provided in the second fluid communication means.
Advantageously, the first fluid communication means comprises a fluid conduit or umbilical, such as coiled tubing or the, like, which extends between the purging fluid supply and the vessel to be purged.
Preferably, the second fluid communication means comprises a fluid conduit or umbilical or the like which extends, between the vessel to be purged and the well control package of the wellhead assembly.
According to a second aspect of the present invention, there is provided a system for use in purging fluid from a vessel adapted to be coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means, said system comprising:
first fluid communication means adapted to extend between a purging fluid supply and the vessel to be purged; and
second fluid communication means adapted to extend between the vessel to be purged and the well control package at a location above at least one of the well control valve means;
wherein, in use, purging fluid supplied to the vessel via the first fluid communication means displaces fluid from the vessel into the second fluid communication means and into the well control package.
The purging system of the present invention is therefore adapted to simultaneously purge fluid from the vessel and at least a portion of the well control package. The present invention therefore eliminates the requirement to provide separate purging apparatus, or at least minimises the extent to which a separate purging apparatus is required, in order to purge fluid contained within the well control package. Advantageously, once the fluid within the vessel has been displaced, the vessel and optionally the well control package may be detached from the wellhead assembly and returned to the surface.
Preferably, the system, in use, directs the displaced fluid from the vessel towards a production fluid outlet defined in the subsea tree. Accordingly, the purged fluids may be flowed to surface via a conventional production marine riser and thus handled using conventional production fluid handling equipment This arrangement therefore eliminates the requirement to provide additional fluid handling equipment at surface level which is dedicated to handling purged fluids. Preferably, the displaced fluids are directed through a fluid passage within the wellhead assembly to which the vessel is coupled. The fluid passage within the wellhead assembly may be defined by a production fluid bore which communicates with the production fluid outlet of the subsea tree. The fluid passage within the wellhead assembly may be defined by a production fluid bore and a subsea tree crossover flow line, wherein the crossover flow line communicates with the production fluid outlet.
Alternatively, the displaced fluid may be directed into the well. Alternatively further, the displaced fluid may be flowed to surface via a dedicated flow path.
In one embodiment of the present invention, the purging fluid supply may be a container or vessel located at surface level, and the first fluid communication means may extend from the container at the surface to the vessel. In an alternative embodiment of the present invention, the purging fluid supply may be a container or vessel located subsea, and preferably adjacent or in close proximity to the vessel and wellhead. In this embodiment the purging fluid supply may be mounted on a skid, and advantageously on a Remotely Operated Vehicle (ROV) skid which would permit dynamic positioning and control of the location of the purging fluid supply. Alternatively, the purging fluid supply may be directly or indirectly mounted on the vessel.
Preferably, the supply of purging fluid comprises a known volume of purging fluid, which may be selected to displace the required volume of fluid from the vessel. Advantageously, the purging fluid supply comprises sufficient fluid to achieve at least one, and preferably a plurality of purging operations.
The purging fluid may be glycol or a suitable water and glycol mixture. Advantageously, the glycol assists to prevent or substantially minimise the formation of hydrates. It should be noted that other hydrate inhibiting fluids such as methanol or MEG (Methyl Ethyl Glycol) may alternatively be used.
Preferably, the system comprises a stab-in plate arrangement mounted on the vessel and adapted to permit the first fluid communication means to be coupled to the vessel. Advantageously, the stab-in plate arrangement may be adapted to selectively permit fluid flow between the first fluid communication means and the vessel such that fluid flow through the stab-in plate may be prevented when purging is not required, and permitted when purging is required. Accordingly, by selectively permitting fluid flow between the first fluid communication means and the vessel, the inadvertent flow of fluid from the vessel towards the purging fluid supply will be prevented, or at least minimised.
In embodiments of the present invention the stab-in plate arrangement may comprise first and second stab-in plates adapted to be mounted on the vessel, wherein the first fluid communication means is adapted to be coupled to the first stab-in plate when purging is not required, and reconfigured to be coupled to the second stab-in plate when purging of the vessel is required. Advantageously, the first stab-in plate, in use, is adapted to at least prevent fluid flow between the vessel and the first fluid communication means, and the second stab-in plate, in use, is adapted to permit fluid flow between the first fluid communication means and the vessel when coupled thereto. Beneficially, the second stab-in plate is adapted to permit selective fluid communication between the first fluid communication means and the vessel when coupled thereto. Coupling the first fluid communication means to the first stab-in plate when purging is not required maintains the first fluid communication means readily accessible while preventing any fluid exchange between the vessel and the first fluid communication means.
When purging is required, the first fluid communication means may be detached from the first stab-in plate, a barrier to the flow of well fluid set, and the first fluid communication means subsequently coupled to the second stab-in plate. Advantageously, the first fluid communication means may be moved and reconfigured between the first and second stab-in plates by a Remotely Operated Vehicle (ROV) controlled from surface. Alternatively, the first fluid communication means may be reconfigured by an automated actuating and control system or mechanism which may form part of the apparatus of the present invention.
Preferably, the system of the present invention further comprises flow isolation means for controlling fluid flow.
Advantageously, the system comprises a primary isolation means for removing communication with the well bore. The primary isolation means may be a sub-surface safety valve (SSSV) located within the wellhead. The SSSV is well known in the art.
Preferably, the system comprises well fluid isolation means for selectively preventing the flow of well fluid towards the vessel and through the production fluid outlet of the subsea tree. In one embodiment of the present invention, the well fluid isolation means may comprise a single valve means, such as a ball valve or a bore plug or the like. The single valve means may be a production master valve. In this embodiment, the single valve means, in use, selectively prevents the flow of well fluid both towards the vessel and through the production fluid outlet of the subsea tree. Conveniently, this particular arrangement is advantageously suitable for use in purging a vessel which is adapted to be coupled to a wellhead assembly incorporating a dual bore subsea tree configuration, which is well known in the art. Such a dual bore subsea tree is conventionally known as a vertical subsea tree.
In an alternative embodiment, the well fluid isolation means may comprise first isolation means for selectively preventing the flow of well fluids towards the vessel, and second isolation means for selectively preventing the flow of well fluids through the production fluid outlet of the subsea tree. Advantageously, the first and second isolation means each may comprise valve means such as a ball valve or the like, or may alternatively comprise a plug or the like. In a preferred embodiment the first isolation means is a production master valve and the second isolation means is a tubing hanger plug. Conveniently, this particular arrangement is advantageously suitable for use for purging a vessel which is adapted to be coupled to a wellhead assembly incorporating a single bore subsea tree configuration, which is well known in the art. Such a single bore subsea tree is conventionally known as a horizontal subsea tree.
In preferred embodiments of the present invention the well fluid isolation means is provided in the subsea tree of the wellhead assembly to which the vessel to be purged is coupled. Advantageously, the well fluid isolation means of the present invention may comprise existing valve means within the subsea tree such that the present invention may advantageously utilise existing wellhead assembly configurations.
Preferably, the system comprises well annulus fluid isolation means adapted to selectively prevent fluid flow either into the annulus from the vessel or wellhead assembly, or alternatively from the annulus and into the wellhead assembly and/or vessel. Advantageously, the well annulus fluid isolation means may be provided in the wellhead assembly, and preferably in the subsea tree. Beneficially, the annulus fluid isolation means may comprise existing valve means within the wellhead assembly.
Preferably, the system of the present invention comprises vessel isolation means adapted for use in selectively isolating the vessel from the wellhead assembly to which it is coupled. Advantageously, in use, the vessel isolation means may prevent purging fluid provided to the vessel via the first fluid communication means from, bypassing the vessel and flowing towards the wellhead assembly. Additionally, the vessel isolation means, in use, advantageously prevents fluid purged from the vessel from re-entering the vessel via the second fluid communication means. The vessel isolation means may comprise valve means such as a ball valve or the like. Advantageously, the vessel isolation means may be positioned within the wellhead assembly. Preferably, the vessel isolation means is positioned within the well control package of the wellhead assembly. Preferably also, the vessel isolation means comprises existing valve means within the wellhead assembly to which the vessel to be purged is coupled. Alternatively, the vessel isolation means may be provided within the vessel to be purged.
Advantageously, the system may further comprise closure means for retaining purging fluid within the vessel once purging has taken place, such that the closure means may be activated when the vessel is to be separated from the wellhead and returned to surface.
Preferably, the system of the present invention comprises non-return valve means for preventing the return of purged fluid back into or towards the vessel. Advantageously, in one embodiment the non-return valve means is provided in the second fluid communication means.
Advantageously, the first fluid communication means comprises a fluid conduit or umbilical, such as coiled tubing or the like, which extends between the purging fluid supply and the vessel to be purged.
Preferably, the second fluid communication means comprises a fluid conduit or umbilical or the like which extends between the vessel to be purged and the well control package of the wellhead assembly.
Advantageously, the purging system of the present invention may be adapted for use with a self-contained subsea well intervention package which is coupled to a wellhead assembly. Advantageously, the system of the present invention may be adapted for use in purging well fluids from a subsea well intervention package coupled to a wellhead assembly prior to retrieval of the intervention package to surface level. In this embodiment of the present invention the well intervention package preferably comprises a vessel to be purged, wherein the vessel is used for storing and deploying wireline tooling.
According to a third aspect of the present invention, there is provided a method of purging fluid from a vessel when coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means, said method comprising the steps of:
providing a first fluid communication means extending between a purging fluid supply and the vessel;
providing a second fluid communication means extending between the vessel and the well control package at a location above at least one of the well control valve means; and
passing purging fluid from the purging fluid supply to the vessel via the first fluid communication means to displace fluid within the vessel therefrom, wherein the displaced fluid flows from the vessel and into the well control package via the second fluid communication means.
Accordingly, the method of the present invention simultaneously displaces fluid from the vessel and the well control package.
Preferably, the method further involves the step of flowing the displaced fluids to a production fluid outlet of the subsea tree and subsequently to surface level via a production marine riser.
Alternatively, the displaced fluid may be directed into the well. Alternatively further, the displaced fluid may be flowed to surface via a dedicated flow path.
Advantageously, the method of the present invention comprises the step of isolating the vessel and the production fluid outlet of the subsea tree from the flow of well fluids through the wellhead assembly. This step may be achieved by closing a sub-surface safety valve (SSSV) and a production master valve within the wellhead and wellhead assembly. In one embodiment the vessel may be isolated from the well head assembly by setting in place a suitable plug such as a tubing hanger plug or the like. Advantageously, where a plug is utilised the method may comprise the further step of re-opening the sub-surface safety valve and exposing the plug to well fluid pressure to ensure adequate sealing integrity of the plug has been achieved. Once sealing integrity of the plug has been verified the SSSV is preferably once again closed.
In one embodiment, the method may further comprise the step of isolating the vessel from annulus fluids through the wellhead assembly. This may be achieved by closing one or more valves within the wellhead assembly.
Preferably, the purging fluid is flowed into the vessel at a rate selected to prevent or at least minimise any mixing between the purging fluid and well fluids within the vessel.
Advantageously, the volume of purging fluid is selected in accordance with the volume of the vessel to be purged to ensure that substantially all well fluids have been removed.
Preferably, the method further involves the step of setting a sealing plug within the wellhead assembly and isolating the purging fluid within the vessel such that the intervention system may be detached from the wellhead and returned to surface, and the wellhead can continue to produce well fluids to surface through the production fluid outlet and via a production marine riser.
According to a fourth aspect of the present invention there is provided a method of performing a well intervention, said method comprising the steps of:
providing a vessel for storing and deploying wireline tooling and coupling said vessel to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree;
selecting and running wireline tooling into the well from the vessel to perform an intervention operation;
retrieving all wireline tooling from the well and into a stored position within the vessel;
providing a first fluid communication means extending between a purging fluid supply and the vessel;
providing a second fluid communication means extending between the vessel and the well control package;
passing purging fluid from the purging fluid supply to the vessel via the first fluid communication means to displace fluid within the vessel therefrom, wherein the displaced fluid flows from the vessel and into the well control package via the second fluid communication means; and
detaching the vessel from the wellhead assembly and retrieving the vessel to surface.
Preferably, the well control package comprises a plurality of well control valve means and the second fluid communication means is provided to extend between the vessel and the well control package at a position above at least one of the well control valve means.
Advantageously, the vessel is a subsea well intervention system.
These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Reference is first made to
As conventionally known in the art, the subsea tree 14 comprises a production fluid valve arrangement including a production master valve 28 and a production wing valve 30. Additionally, the subsea tree 14 comprises an annulus valve arrangement including an annulus master valve 32, an annulus wing valve 34 and an annulus access valve 36.
The subsea tree 14 further comprises a fluid crossover conduit 38 extending between the annulus access bore 27 and the production fluid outlet bore 26. More specifically, the crossover conduit 38 extends between the annulus access bore 27 at a location between the annulus master valve 32 and the annulus wing valve 34, and the production fluid outlet 26 at a location between the production master valve 28 and the production wing valve 30. The crossover conduit 38 is conventionally utilised for controlling excessive pressures which may occur in the annulus.
In accordance with conventional arrangements, the wellhead assembly additionally comprises a sub-surface safety valve (SSSV) 40 located within the wellhead below the subsea tree. In use the SSSV is adapted to selectively prevent fluid communication between the well bore and the subsea tree 14.
The intervention system 10 defines a central bore 42 which extends along the entire length of the system 10 towards the well head assembly 12, wherein the central bore 42 is coaxially aligned with throughbore 17 of the well control package 16 and throughbore 24 of the subsea tree 14. The intervention system 10 is therefore exposed to well bore fluid.
Intervention system 10 includes a tool storage chamber 44 which comprises a plurality of tool storage clamping means (not shown for clarity) capable of retaining a respective tool (also not shown for clarity) in a storage position and selectively moving said tool to a deployment position where the tool may be coupled and decoupled to a wireline connection tool (not shown) from above. When located in the deployment position a tool is aligned with the central bore 42 of the system 10 such that the tool may be deployed through the throughbores 17, 24 and into the well bore.
Intervention system 10 also includes a wireline winch assembly 46, such as that disclosed in Applicant's co-pending UK application no. 0419781.0, located above the tool storage chamber. The winch assembly 46 comprises a winch housing 47 which defines a winch cavity 50, within which cavity 50 is located a wireline winch drum 48 mounted about the central bore 42. In use, wireline from the winch drum 48 exits the winch cavity 50 of the housing 47, extends upwardly through a first tube 52, passes through an upper sheave 54, and extends downwardly through a second tube 56 and into the central bore 42. Accordingly, the winch cavity 50, in use, is also exposed to well fluids via the central bore 42 and the first and second tubes 52, 56.
As noted above, the intervention system 10 is exposed to well fluid when in operation. Accordingly, any well fluid located within the intervention system 10 must be suitably handled when the intervention system 10 is to be detached from the well head 12 and retrieved to surface. The intervention system 10 thus incorporates a system for purging well fluid therefrom, as discussed in detail below.
The purging system includes a purging fluid supply 57 and first fluid communication means in the form of a conduit 58 extending between the purging fluid supply 57 and a lower portion of the intervention system 10, below the tool storage chamber 44. The purging fluid supply 57 may be located at surface level or alternatively may be located subsea, adjacent the intervention system 10. The purging system further comprises second fluid communication means in the form of a conduit 60 extending between an upper portion of the intervention system 10, above the winch assembly 46, and the well control package 16 of the wellhead 12. The purging fluid may be glycol or a water/glycol mixture. As shown, conduit 60 extends between the upper sheave 54 of the winch assembly and the well control package 16, below the upper isolation valve 18. It should be noted that the fluid conduit 58 is adapted to be reconfigured between a purging position, as shown in
In use, purging fluid is flowed from the first fluid conduit 58, through the intervention system 10 to displace well fluids therein into the second fluid conduit 60 and towards the wellhead assembly 12, as discussed in more detail below. It should be noted that a crossover conduit 62 and crossover valve 64 is provided between the central bore 42 and the winch cavity 50 such that the purging fluid may flow from the central bore 42 and into the winch cavity 50 to upwardly displace well fluids therefrom. In this way well fluids will be displaced from the winch assembly 46 via both the first and second tubes 52, 56 and the upper sheave 54.
When well fluids are to be purged from the intervention system 10 and the system 10 subsequently returned to surface, the following steps will be followed. Initially, all wireline tools are removed from the well bore and returned to a storage position within the tool storage chamber 44. Following this the sub-surface safety valve (SSSV) 40 is closed to remove communication with the well bore, and using the Intervention system 10 a tubing hanger plug 66 is set in place to prevent fluid communication along the throughbore 24. As shown, the tubing hanger plug 66 is set in place above the branch of the production fluid outlet bore 26. The annulus wing valve 27, annulus master valve 32 and production master valve 28 are then closed. The annulus access valve 36 and the production wing valve 30 are configured to be open. A spool valve 68 in the crossover conduit 38 is then opened to vent down the intervention system 10 into the production fluid outlet bore 26. Subsequent to this the SSSV 40 is opened to re-establish communication with the well bore in order to verify sealing integrity of the tubing hanger plug, after which the SSSV 40 is again closed to remove communication with the well bore. The upper intervention valve 18 in the well control package 16 is then closed. At this stage a number of barriers are provided between the wellhead 12 and the intervention system 10 and the various valves 28,30,32,34,37,68 in the wellhead are appropriately configured such that purging of the system 10 may now be achieved, as discussed below.
The first fluid conduit 58 is moved from the non-purging position to the purging position, as shown in
Once the required quantity of purging fluid is introduced through the intervention system 10 a tree cap plug (not shown) is set in place and the resultant cavity below the tree cap plug and above the tubing hanger plug 66 is tested for sealing integrity, following which the valves of the subsea tree 14 are returned to their original configurations. An intervention system isolation valve 74 may then be closed and the intervention system 10 detached from the wellhead assembly 12 and subsequently retrieved to surface. The well control package 16 may also be isolated from the subsea tree 14 and subsequently detached therefrom and returned to surface.
Reference is now made to
The subsea tree 80 comprises a production master valve 90 located below the branch of the production fluid outlet bore 86, a production swab valve 92 located above the branch of bore 86, and a production wing valve 94 located in bore 86. Purging of an intervention system may be achieved in a similar fashion to that shown in
The present invention provides a unique system for purging well fluids contained in a subsea intervention system prior to retrieval of the intervention system to surface. Displacing the well fluids subsea from both the intervention system and the well control package of the wellhead assembly eliminates the requirement to utilise separate purging systems or apparatus. Additionally, directing the purged fluids towards the production outlet of the wellhead eliminates the requirement to maintain additional specialised well fluid handling equipment at surface level which would otherwise be required if the intervention system is retrieved to surface while containing well fluid.
It should be understood that the embodiments described above are merely representative of the present invention and that various modifications may be made thereto without departing from the scope of the present invention. For example, purged fluid may be directed to surface via a dedicated flow path or conduit. Alternatively, purged fluid may be directed into the well.
Claims
1. A well intervention system adapted to be coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means, said system comprising:
- a vessel for use in storing and deploying wireline tooling, said vessel adapted to be exposed to well fluids when in use;
- first fluid communication means adapted to extend between a purging fluid supply and the vessel; and
- second fluid communication means adapted to extend between the vessel and the well control package at a location above at least one of the well control valve means;
- wherein, in use, purging fluid supplied to the vessel via the first fluid communication means displaces fluid from the vessel into the second fluid communication means and into the well control package.
2. A system as claimed in claim 1 wherein the system, in use, directs the displaced fluid from the vessel towards a production fluid outlet defined in the subsea tree.
3. A system as claimed in claim 1 wherein the displaced fluids are directed through a fluid passage within the wellhead assembly to which the vessel is coupled.
4. A system as claimed in claim 3 wherein the fluid passage within the wellhead assembly is defined by a production fluid bore which communicates with the production fluid outlet of the subsea tree.
5. A system as claimed in claim 3 wherein the fluid passage within the wellhead assembly is defined by a production fluid bore and a subsea tree crossover flow line, wherein the crossover flow line communications with the product fluid outlet.
6. A system as claimed in claim 1 where the displaced fluid may be directed into the well.
7. A system as claimed in claim 6 wherein the displaced fluid is flowed to surface via a dedicated flow path.
8. A system as claimed in claim 1 wherein the purging fluid supply is a container or vessel located at surface level, and the first fluid communication means extends from the container at the surface to the vessel.
9. A system as claimed in claim 1 wherein the purging fluid supply is a container or vessel located subsea, and preferably adjacent or in close proximity to the vessel and wellhead.
10. A system as claimed in claim 1 wherein the purging fluid supply is directly or indirectly mounted on the vessel.
11. A system as claimed in claim 1 wherein the supply of purging fluid comprises a known volume of purging fluid which is selected to displace the require volume of fluid from the vessel.
12. A system as claimed in claim 1 wherein the purging fluid supply comprises sufficient fluid to achieve at least one, and preferably a plurality of purging operations.
13. A system as claimed in claim 1 wherein the purging fluid is glycol or a suitable water glycol mixture.
14. A system as claimed in claim 1 wherein the purging fluid is a hydrate inhibiting fluids such as methanol or MEG (Methyl Ethyl Glycol).
15. A system as claimed in claim 1 wherein the vessel defines a central bore which in use extends towards the wellhead assembly and which is coaxially aligned with a throughbore of the wellhead assembly when the intervention system is coupled thereto.
16. A system as claimed in claim 1 wherein the vessel of the intervention system comprises a tool storage chamber.
17. A system as claimed in claim 16 wherein the tool storage chamber comprises a plurality of tool storage clamping means capable of retaining a respective tool in a storage position and selectively moving said tool to a deployment position where the tool is coupled and decoupled to a wireline connection tool from above.
18. A system as claimed in claim 16 wherein the tool storage chamber defines a portion of the central bore of the vessel.
19. A system as claimed in claim 16 wherein a tool when located in the deployment position by a tool storage clamping means is substantially aligned with the central bore of the vessel such that said tool will also be substantially aligned with the throughbore of the wellhead assembly.
20. A system as claimed in claim 1 wherein the vessel of the well intervention system further includes a wireline winch assembly.
21. A system as claimed in claim 20 wherein the winch assembly comprises a winch housing within which a wireline winch drum is located and mounted about the central bore of the vessel.
22. A system as claimed in claim 20 wherein the winch assembly is located above the tool storage chamber.
23. A system as claimed in wherein the winch housing defines a winch cavity within which the winch drum is located wherein, in use, wireline from the winch drum exits the winch cavity, extends upwardly through a first tube or riser, passes through an upper sheave, and extends downwardly through a second tube or riser and into the central bore of the vessel.
24. A system as claimed in claim 20 wherein the first fluid communication means is adapted to be coupled to the vessel at a position below the tool storage chamber and the winch assembly.
25. A system as claimed in claim 20 wherein a crossover fluid conduit is defined between the central bore of the vessel and the winch cavity such that the purging fluid may flow from the central bore and into the winch cavity to displace well fluids therefrom.
26. A system as claimed in claim 20 wherein the second fluid communication means is adapted to extend between an upper portion of the vessel, above the tool storage chamber and the winch assembly, and the well control package.
27. A system as claimed in claim 20 wherein the second fluid communication means is adapted to extend between the upper sheave of the winch assembly and the wellhead assembly.
28. A system as claimed in claim 1 wherein the intervention system further comprises flow isolation means for controlling fluid flow.
29. A system as claimed in claim 1 wherein the system comprises a primary isolation means for removing communication with the well bore.
30. A system as claimed in claim 29 wherein the primary isolation means is a sub-surface safety valve (SSSV) located within the wellhead.
31. A system as claimed in claim 1 wherein the system comprises well fluid isolation means for selectively preventing the flow of well fluid towards the vessel and through the production fluid outlet of the subsea tree.
32. A system as claimed in claim 31 wherein the well fluid isolation means comprises a single valve means, such as a ball valve or a bore plug or the like.
33. A system as claimed in claim 32 wherein the single valve means is a production master valve.
34. A system as claimed in claim 1 wherein the well fluid isolation comprises first isolation means for selectively preventing the flow of well fluid towards the vessel, and the second isolation means for selectively preventing the flow of well fluids through the production fluid outlet of the subsea tree.
35. A system as claimed in claim 34 wherein the first and second isolation means each comprise valve means such as a ball valve, a plug or the like.
36. A system as claimed in claim 34 wherein the first isolation means is a production master valve and the second isolation means is a tubing hanger plug.
37. A system as claimed in claim 1 wherein the well fluid isolation means is provided in the subsea tree of the wellhead assembly to which the intervention system is coupled.
38. A system as claimed in claim 37 wherein the well fluid isolation means of the present invention comprises existing valve means within the subsea tree such that the existing wellhead assembly configurations are utilized.
39. A system as claimed in claim 1 wherein the system comprises well annulus fluid isolation means adapted to selectively prevent fluid flow either into the annulus from the intervention system or wellhead assembly, or from the annulus and into the wellhead assembly and/or intervention system.
40. A system as claimed in claim 39 wherein the well annulus fluid isolation means is provided in the wellhead assembly, and preferably in the subsea tree.
41. A system as claimed in claim 39 wherein the annulus fluid isolation means comprises existing valve means within the wellhead assembly.
42. A system as claimed in claim 1 wherein the system of the present invention comprises vessel isolation means adapted for use in selectively isolating the vessel of the intervention system from the wellhead assembly to which it is coupled.
43. A system as claimed in claim 42 wherein the vessel isolation means is arranged to prevent purging fluid provided to the vessel via the first fluid communication means from bypassing the vessel and flow towards the wellhead assembly.
44. A system as claimed in claim 42 wherein the vessel isolation means comprises valve means such as a ball valve or the like.
45. A system as claimed in claim 42 wherein the vessel isolation means is positioned within the well control package of the wellhead assembly.
46. A system as claimed in claim 42 wherein the vessel isolation means comprises existing valve means within the wellhead assembly to which the vessel to be purged is coupled.
47. A system as claimed in claim 42 wherein the vessel isolation means is provided within the vessel to be purged.
48. A system as claimed in claim 1 wherein the system further comprises closure means for retaining purging fluid within the vessel once purging has taken place, whereby the closure means is activated when the intervention system is to be separated from the wellhead assembly and returned to surface.
49. A system as claimed in claim 1 wherein the system comprises non-return valve means for preventing the return of purged fluid back into or towards the vessel.
50. A system as claimed in claim 49 wherein in one embodiment the non-return valve means is provided in the second fluid communication means.
51. A system as claimed in claim 1 wherein the first fluid communication means comprises a fluid conduit or umbilical, such as coiled tubing or the like, which extends between the purging fluid supply and the vessel to be purged.
52. A system as claimed in claim 1 wherein the second fluid communication means comprises a fluid conduit or umbilical or the like which extends between the vessel to be purged and the well control package of the wellhead assembly.
53. A system for use in purging fluid from a vessel adapted to be coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means, said system comprising:
- first fluid communication means adapted to extend between a purging fluid supply and the vessel to be purged;
- second fluid communication means adapted to extend between the vessel to be purged and the well control package at a location above at least one of the well control valve means;
- wherein, in use, purging fluid supplied to the vessel via the first fluid communication means displaced fluid from the vessel into the second fluid communication means and into the well control package.
54. A system as claimed in claim 53 wherein the system, in use, directs the displaced fluid from the vessel towards a production fluid outlet defined in the subsea tree and is flowed to surface via a conventional production marine riser and thus handled using conventional production fluid handling equipment.
55. A system as claimed in claim 53 wherein the displaced fluids are directed through a fluid passage within the wellhead assembly to which the vessel is coupled.
56. A system as claimed in claim 55 wherein the fluid passage within the wellhead assembly is defined by a production fluid bore which communicates with the production fluid outlet of the subsea tree.
57. A system as claimed in claimed 55 wherein the fluid passage within the wellhead assembly is defined by a production fluid bore and a subsea tree crossover flow line, wherein the crossover flow line communication with the production fluid outlet.
58. A system as claimed in claim 53 wherein the displaced fluid is directed into the well.
59. A system as claimed in claim 53 wherein the displaced fluid is flowed to surface via a dedicated flow path.
60. A system as claimed in claim 53 wherein the purging fluid supply is a container or vessel located at surface level, and the first fluid communication means extends from the container at the surface to the vessel.
61. A system as claimed in claim 53 wherein the purging fluid supply is a container or vessel located subsea adjacent to or in close proximity to the vessel and wellhead.
62. A system as claimed in claim 60 wherein the purging fluid supply is mounted on a Remotely Operated Vehicle (ROV) skid.
63. A system as claimed in claim 60 wherein the purging fluid supply is directly or indirectly mounted on the vessel.
64. A system as claimed in claim 53 where in the supply of purging fluid comprises a known volume of purging fluid which is selected to displace the required volume of fluid from the vessel.
65. A system as claimed in claim 53 wherein the purging fluid is glycol or a suitable water or glycol mixture.
66. A system as claimed in claim 53 wherein other hydrate inhibiting fluids such as methanol or MEG (Methyl Ethyl Glycol) are used as a purging fluid.
67. A system as claimed in claim 53 wherein the system includes a stab-in plate arrangement mounted on the vessel and adapted to permit the first fluid communication means to be coupled to the vessel.
68. A system as claimed in claim 67 wherein the stab-in plate arrangement is adapted to selectively permit fluid flow between the first fluid communication means and the vessel such that fluid flow through the stab-in plate is prevented when purging is not required, and permitted when purging is required.
69. A system as claimed in claim 67 wherein the stab-in plate arrangement may comprise first and second stab-in plates adapted to be mounted on the vessel, wherein the first fluid communication means is adapted to be coupled to the first stab-in plate when purging of the vessel is required.
70. A system as claimed in 69 wherein the first stab-in plate, in use, is adapted to at least prevent fluid flow between the vessel and the first fluid communication means, and the second stab-in plate, in use, is adapted to permit fluid flow between the first fluid communication means and the vessel when coupled thereto.
71. A system as claimed in claim 69 wherein the second stab-in plate is adapted to permit selective fluid communication between the first fluid communication means and the vessel when coupled thereto.
72. A system as claimed in claim 53 wherein the system of the present invention further comprises flow isolation means for controlling fluid flow.
73. A system as claimed in claim 72 wherein the system comprises a primary isolation means for removing communication with the well bore.
74. A system as claimed in claim 73 wherein the primary isolation means is a sub-surface safety valve (SSSV) located within the wellhead.
75. A system as claimed in claim 53 wherein the system comprises a well fluid isolation means for selectively preventing the flow of well fluid towards the vessel and through the production fluid outlet of the subsea tree.
76. A system as claimed in claim 75 wherein the well fluid isolation comprises a single valve means, such as a ball valve or a bore plug or the like.
77. A system as claimed in claim 76 wherein the single valve means may be a production master valve.
78. A system as claimed in claim 75 wherein the well fluid isolation means comprises first isolation means for selectively preventing the flow of well fluids towards the vessel, and second isolation means for selectively preventing the flow of well fluids through the production fluid outlet of the subsea tree.
79. A system as claimed in claim 78 wherein the first and second isolation means each comprise valve means such as a ball valve or the like, a plug or the like.
80. A system as claimed in claim 75 wherein the first isolation means is a production master valve and the second isolation means is a tubing hanger plug.
81. A system as claimed in claim 75 wherein the well fluid isolation means is provided in the subsea tree of the wellhead assembly to which the vessel to be purged is coupled.
82. A system as claimed in claim 53 wherein the system comprises well annulus fluid isolation means adapted to selectively prevent fluid flow either into the annulus from the vessel or wellhead assembly, or alternatively from the annulus and into the wellhead assembly and/or vessel.
83. A system as claimed in claim 82 wherein the well annulus fluid isolation means is provided in the wellhead assembly and preferably in the subsea tree.
84. A system as claimed in claim 53 wherein the system of the present invention includes vessel isolation means adapted for use in selectively isolating the vessel from the wellhead assembly to which it is coupled.
85. A system as claimed in claim 84 wherein the vessel isolation means comprises valve means such as a ball valve positioned within the wellhead assembly.
86. A system as claimed in claim 85 wherein the vessel isolation means is positioned within the well control package of the wellhead assembly.
87. A system as claimed in claim 53 further including closure means for retaining purging fluid within the vessel once purging has taken place, such that the closure means is activated when the vessel is to be separated from the wellhead and returned to surface.
88. A system as claimed in claim 53 further including the system of the present invention comprising non-return valve means for preventing the return of purged fluid back into or towards the vessel.
89. A system as claimed in claim 88 wherein the non-return valve means is provided in the second fluid communication means.
90. A system as claimed in claim 53 wherein the first fluid communication means comprises a fluid conduit or umbilical, such as coiled tubing or the like, which extends between the purging fluid supply and the vessel to be purged.
91. A system as claimed in claim 53 wherein the second fluid communications means comprises a fluid conduit or umbilical or the like which extends between the vessel to be purged and the well control package of the wellhead assembly.
92. A method of purging fluid from a vessel when coupled to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree, wherein the well control package includes a plurality of well control valve means, said method comprising the steps of:
- providing a first fluid communication means extending between a purging fluid supply and the vessel;
- providing a second fluid communication means extending between the vessel and the well control package at a location above at least one of the well control valve means; and
- passing purging fluid from the purging fluid supply to the vessel via the first fluid communication means to displace fluid within the vessel therefrom, wherein the displaced fluid flows from the vessel and into the well control package via the second fluid communication means.
93. A method as claimed in claim 92 wherein the method involves the step of flowing the displaced fluids to a production fluid outlet of the subsea tree and subsequently to surface level via a production riser.
94. A method as claimed in claim 92 wherein the displaced fluid is directed into the well or flowed to surface via a dedicated flow path.
95. A method as claimed in claim 92 wherein the method of the present invention includes the step of isolating the vessel and the production fluid outlet of the subsea tree from the flow of well fluids through the wellhead assembly by closing a sub-surface safety valve (SSV) and a production master valve within the wellhead and wellhead assembly.
96. A method as claimed in claim 92 including the steps of isolating the vessel from the well head assembly by setting in place a suitable plug such as a tubing hanger plug, and
- re-opening the sub-surface safety valve and exposing the plug to well fluid pressure to ensure adequate sealing integrity of the plug has been achieved.
97. A method as claimed in claim 92 including the steps of isolating the vessel from annulus fluids through the wellhead assembly by closing one or more valve within the wellhead assembly.
98. A method as claimed in claim 92 including the steps of flowing the purging fluid into the vessel at a rate selected to prevent or at least minimize any mixing between the purging fluid and the well fluids within the vessel.
99. A method as claimed in claim 92 including the step of setting a sealing plug within the wellhead assembly and isolating the purging fluid within the vessel such that the intervention system is detached from the wellhead and returned to surface, and the wellhead continues to produce well fluids to surface through the production fluid outlet and via a production marine riser.
100. A method of performing method of performing a well intervention, said method comprising the steps of:
- providing a vessel for storing and deploying wireline tooling and coupling said vessel to a subsea wellhead assembly including a subsea tree coupled to a wellhead and a well control package coupled to the subsea tree;
- selecting and running wireline tooling into the well from the vessel to perform an intervention operation;
- retrieving all wireline tooling from the well and into a stored position within the vessel;
- providing a first fluid communication means extending between a purging fluid supply and the vessel;
- providing a second fluid communication means extending between the vessel and the well control package;
- passing purging fluid from the purging fluid supply to the vessel via the first fluid communication means to displace fluid within the vessel therefrom, wherein the displaced fluid flows from the vessel and into the well control package via the second fluid communication means; and
- detaching the vessel from the wellhead assembly and retrieving the vessel to surface.
101. A method as claimed in claim 100 wherein the method includes the steps of:
- providing a plurality of well control valve means in the well control package;
- disposing second fluid communication means between the vessel and the well control package at a position above at least one of the well control valve means.
Type: Application
Filed: Jan 16, 2006
Publication Date: Apr 28, 2011
Inventors: Andrew Richards (Aberdeenshire), Mark Davies (Aberdeenshire)
Application Number: 11/795,352
International Classification: E21B 41/04 (20060101); E21B 34/04 (20060101);
