Purge System

Abstract

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.

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.