Method and a system for controlling movements of a free-hanging tubular

Abstract

An apparatus for controlling movements of a free-hanging tubular suspended via at least a connector element by at least one compensator member connected to a buoyant vessel, the tubular extending into a body of water below the vessel. The apparatus includes a motion sensing device configured to sense movements of the compensator member and thus that of the vessel, and a position indicator device configured to sense the position of the connector element, and thus that of an upper region of the tubular, with respect to the compensator member. The apparatus further includes a data processor configured to determine one or more parameters regarding the movement between the vessel and the upper region of the tubular; and an adjusting device configured to control at least the stiffness and dampening of the compensator member; whereby the axial loads which are transferred between the compensator and the tubular may be controlled.

1 . An apparatus for controlling movements of a free-hanging tubular in a soft hang-off mode suspended via at least a connector element by at least one compensator member which is connected to a buoyant vessel, said tubular extending into a body of water below the vessel, comprising:
 first sensing means for sensing dynamic and/or spatial parameters of the compensator member and thus that of the vessel;   second sensing means for sensing dynamic and/or spatial parameters of the connector element, and thus that of an upper region of the tubular;   data processing means for processing data supplied by said first and second sensing means and determining one or more parameters regarding the movement between the vessel and the upper region of the tubular; and   adjusting means for controlling at least the stiffness and dampening of the compensator member,   whereby the axial loads which are transferred between the compensator and the tubular may be controlled.   
     
     
         2 . The apparatus of  claim 1 , wherein the first sensing means comprises motion sensing means for sensing movements of the compensator member and thus that of the vessel. 
     
     
         3 . The apparatus of  claim 1 , wherein the second sensing means comprises position indicator means for sensing the position of the connector element, and thus that of an upper region of the tubular, with respect to the compensator member. 
     
     
         4 . The apparatus of  claim 1 , wherein said one or more parameters regarding the movement between the vessel and the upper region of the tubular comprises acceleration. 
     
     
         5 . The apparatus of  claim 1 , wherein the compensator member comprises a hydraulic cylinder connected via a first fluid line to an accumulator, and a first valve means for controlling the flow in said first fluid line, and a first pressure sensing means for sensing the pressure of said hydraulic fluid. 
     
     
         6 . The apparatus of  claim 5 , further comprising at least one pressure vessel fluidly connected to the accumulator via a second fluid line and regulator means, and further comprising a second pressure sensing means, whereby the pressure exerted on the hydraulic fluid in the accumulator by a pressurised gas in the pressure vessel may be controlled. 
     
     
         7 . The apparatus of  claim 1 , further comprising a heat exchanger, with a cooling circuit, thermally connected to the first fluid line, whereby hydraulic fluid in the first fluid line may be cooled in heat exchange with a cooling fluid. 
     
     
         8 . A system for controlling movements of a free-hanging tubular in a soft hang-off mode, wherein a plurality of apparatuses according to  claim 1  are connected to the tubular via respective compensator members arranged in a symmetrical pattern around the tubular, and further comprising a common data processing means and a common user interface, whereby the movements of the free-hanging tubular may be controlled by a selective manipulation of the individual apparatuses. 
     
     
         9 . A method of controlling movements of a free-hanging tubular in a soft hang-off mode suspended via a connector element by at least one compensator member which is connected to a buoyant vessel, said tubular extending into a body of water below the vessel, said method comprising the steps of:
 collecting motion data for the vessel;   collecting motion data for the upper region of the tubular with respect to the compensator member; and   processing said motion data for the vessel and said motion data for the upper region of the tubular and determining one or more parameters regarding the movement between the vessel and the upper region of the tubular and, based on such data, controlling at least the stiffness and dampening of the compensator member,   whereby the axial loads which are transferred between the compensator and the tubular may be controlled.   
     
     
         10 . The method of  claim 9 , wherein the colleting of motion data for the vessel comprises sensing movements of the vessel. 
     
     
         11 . The method of  claim 9 , wherein the colleting motion data for the upper region of the tubular comprises sensing the position of an upper part of the tubular with respect to the compensator member. 
     
     
         12 . The method of  claim 11 , further comprising the sensing of a first pressure in a hydraulic cylinder connected between the tubular and the vessel, said hydraulic cylinder being connected via a first fluid line to an accumulator, and the sensing of a second pressure in the accumulator exerted by at least one pressure vessel fluidly connected to the accumulator via a second fluid line and regulator means. 
     
     
         13 . The apparatus of  claim 2 , wherein the second sensing means comprises position indicator means for sensing the position of the connector element, and thus that of an upper region of the tubular, with respect to the compensator member. 
     
     
         14 . The apparatus of  claim 2 , wherein said one or more parameters regarding the movement between the vessel and the upper region of the tubular comprises acceleration. 
     
     
         15 . The apparatus of  claim 3 , wherein said one or more parameters regarding the movement between the vessel and the upper region of the tubular comprises acceleration. 
     
     
         16 . The apparatus of  claim 2 , wherein the compensator member comprises a hydraulic cylinder connected via a first fluid line to an accumulator, and a first valve means for controlling the flow in said first fluid line, and a first pressure sensing means for sensing the pressure of said hydraulic fluid. 
     
     
         17 . The apparatus of  claim 3 , wherein the compensator member comprises a hydraulic cylinder connected via a first fluid line to an accumulator, and a first valve means for controlling the flow in said first fluid line, and a first pressure sensing means for sensing the pressure of said hydraulic fluid. 
     
     
         18 . The apparatus of  claim 4 , wherein the compensator member comprises a hydraulic cylinder connected via a first fluid line to an accumulator, and a first valve means for controlling the flow in said first fluid line, and a first pressure sensing means for sensing the pressure of said hydraulic fluid. 
     
     
         19 . The apparatus of  claim 2 , further comprising a heat exchanger, with a cooling circuit, thermally connected to the first fluid line, whereby hydraulic fluid in the first fluid line may be cooled in heat exchange with a cooling fluid. 
     
     
         20 . The apparatus of  claim 3 , further comprising a heat exchanger, with a cooling circuit, thermally connected to the first fluid line, whereby hydraulic fluid in the first fluid line may be cooled in heat exchange with a cooling fluid.