Floating well intervention arrangement comprising a heave compensated work deck and method for well intervention

Abstract

A floating arrangement is provided for overhauling hydrocarbon wells at sea by means of coiled tubing, where the floating arrangement comprises a drill floor and a work deck which is arranged in an opening in the drill floor. The floating arrangement comprises a first set of heave-compensating devices which are arranged for connection to a slip joint connected to a riser in such a manner that an approximately constant tension in the riser can be maintained when the floating arrangement moves in the water. The floating arrangement further comprises a second set of heave-compensating devices which are arranged for connection to the work deck in such a manner that the work deck is at an approximately constant distance from the seabed when the work deck can move relative to the drill floor and the floating arrangement moves in the water. The invention also comprises a method for overhauling hydrocarbon wells at sea from a floating arrangement by means of a coiled tubing frame.

1 . A floating arrangement for overhauling hydrocarbon wells at sea by means of coiled tubing, which floating arrangement comprises a drill floor and a work deck which is arranged in an opening in the drill floor, wherein the floating arrangement comprises a first set of heave-compensating devices which are arranged for connection to a slip joint connected to a riser such that an approximately constant tension in the riser can be maintained when the floating arrangement moves in the water, and that the floating arrangement further comprises a second set of heave-compensating devices which are arranged for connection to the work deck such that the work deck is at an approximately constant distance from the seabed when the work deck can move relative to the drill floor and the floating arrangement moves in the water. 
     
     
         2 . A floating arrangement according to  claim 1 , wherein the drill floor and the work deck are provided with rail devices, thereby enabling a coiled tubing frame to be moved from the drill floor on to the work deck. 
     
     
         3 . A floating arrangement according to  claim 1 , wherein the first set of heave compensators comprises two or more separate heave compensators which are mounted on the drill floor, where the heave compensators comprise wires or telescopic connections which can be connected to the slip joint connected to the riser. 
     
     
         4 . A floating arrangement according to  claim 1 , wherein the heave-compensated work deck is connected via the wires or hydraulic cylinders to two or more heave-compensating devices. 
     
     
         5 . A floating arrangement according to  claim 1 , wherein the work deck is arranged so that it can be locked in a fixed position relative to the drill floor by means of one or more securing devices provided in the work deck and/or the drill floor. 
     
     
         6 . A floating arrangement according to  claim 1 , wherein the floating arrangement comprises control devices which control the work deck's substantially vertical movement relative to the drill floor. 
     
     
         7 . A floating arrangement according to  claim 1 , wherein the first set of heave-compensating devices and the second set of heave-compensating devices are arranged to be able to heave-compensate the slip joint device/riser and the work deck respectively independently of each other. 
     
     
         8 . A floating arrangement according to  claim 1 , wherein the first set of heave-compensating devices and the second set of heave-compensating devices are arranged for synchronous heave compensation of the slip joint/the riser and the work deck respectively. 
     
     
         9 . A method employed in overhauling hydrocarbon wells at sea from a floating arrangement by means of a coiled tubing frame, where the floating arrangement comprises a drill floor and a work deck, which work deck is arranged in an opening in the drill floor, and where the floating arrangement further comprises a first set of heave-compensating devices which can be connected to a slip joint, and a second set of heave-compensating devices which can be connected to the work deck, and where a riser is prepared for receiving coiled tubing, whereby at least
 a surface blow-out preventer is mounted on the riser,   the slip joint is mounted on the upper end of an upper riser, which upper riser is mounted at its lower end to the top of the surface blow-out preventer,   the work deck is secured in a fixed position relative to the drill floor such that the work deck is located on substantially the same level as the drill floor, and   the first set of heave-compensating devices is connected to the slip joint such that a constant tension in the riser is maintained when the floating device moves in the water, wherein the method comprises the following steps:   lowering one or more lengths of a high-pressure riser from the work deck through the slip joint and the upper riser down towards, but not all the way down to the surface blow-out preventer,   moving the coiled tubing frame from the drill floor on to the work deck,   releasing the work deck so that it is located in heave-compensated mode, and   lowering the work deck and the high-pressure riser down towards the surface blow-out preventer until the high-pressure riser engages with and is locked to the surface blow-out preventer.   
     
     
         10 . A method according to  claim 9 , wherein the high-pressure riser is suspended in the work deck before the coiled tubing frame is moved from the drill floor on to the work deck. 
     
     
         11 . A method according to  claim 9 , wherein a surface Christmas tree is moved from the drill floor on to the work deck before or together with the coiled tubing frame, and that the high-pressure riser is mounted to the surface Christmas tree. 
     
     
         12 . A method according to  claim 9 , wherein a block is attached to the coiled tubing frame before the work deck is released and lowered, with the result that at least a part of the weight of the work deck and the riser is supported by the block. 
     
     
         13 . A method according to  claim 9 , wherein the work deck is released and lowered so that at least a part of the weight of the work deck and the riser is supported by the second set of heave-compensating devices connected to the work deck. 
     
     
         14 . A method according to  claim 9 , wherein the first set of heave-compensating devices for the slip joint/the riser and the second set of heave-compensating devices for the work deck compensate synchronously when the high-pressure riser and the surface blow-out preventer are interconnected. 
     
     
         15 . A method of using the floating arrangement according to  claim 1 , comprising the step of using the floating arrangement during intervention of a hydrocarbon well at sea. 
     
     
         16 . The method according to  claim 9 , further comprising the step of performing the method during intervention of a hydrocarbon well at sea.