Device in Connection with Heave Compensation

Abstract

The present invention relates to a heave compensator for a riser, particularly a working riser ( 9 ), comprising a telescopic connection ( 10 ) with a first chamber ( 60 ) which is in fluid connection with the interior of the riser and a second chamber ( 62 ) which is connected with a source of pressure fluid. By varying the pressure in the second chamber in response to the movements of the platform, the telescopic connection can be arranged to move in correspondence with the platform's movements, thereby permitting access to the riser during working operations.

1 : In combination with a heave compensation device for a pressurized riser which extends between a subsea installation and a floating unit, the riser comprising at least two tubular parts which are connected by a telescopic connection that includes a first tubular member which is connected to the first part, a second tubular member which is connected to the second part and a first chamber which is formed between the first and second members and is connected with the interior of the riser and, the improvement comprising a control system which includes:
 a second chamber which is formed between the first and second members and is connected with a source of pressure fluid;   wherein the source of pressure fluid includes means for adjusting at least one of the pressure and the volume of the fluid in the second chamber to thereby control the movement of the first member relative to the second member.   
   
   
       2 : The combination of  claim 1 , wherein one of the parts of the riser is an upper part which is connected to at least one of a dry Christmas tree, an adaptor connection and a surface BOP. 
   
   
       3 : The combination of  claim 1 , wherein one of the parts of the riser is a lower part which comprises a second heave compensation device that maintains the lower part of the riser under substantially constant tension. 
   
   
       4 : The combination of  claim 1 , wherein the adjusting means comprises a pressure-regulating device. 
   
   
       5 : The combination of  claim 1 , wherein the adjusting means comprises a pump. 
   
   
       6 : The combination of  claim 4 , wherein the adjusting means comprises an intelligent control unit for controlling the pressure-regulating device. 
   
   
       7 : The combination of  claim 1 , wherein the first and second members of the telescopic connection overlap at least partially to thereby form an annulus between them within which the first and second chambers are located. 
   
   
       8 : A method for controlling the movement of an upper part of a pressurized riser which is connected to a floating unit and which comprises at least a lower part that is heave compensated by means of tension relative to the floating unit, the lower part and the upper part being connected by a telescopic connection which includes a first chamber in connection with the interior of the riser, the method comprising:
 providing the telescopic connection with a second chamber in connection with a pressure fluid source; and   regulating the supply of pressure fluid to the second chamber in response to at least one of the heave motion of the floating unit and the desired positioning of the upper part relative to the floating unit.   
   
   
       9 : The method according to  claim 8 , wherein the step of regulating the supply of pressure fluid to the second chamber includes regulating the pressure in the second chamber with a pressure regulation device. 
   
   
       10 : The method according to  claim 9 , wherein the pressure regulation device is controlled on the basis of signals received by a data processing unit. 
   
   
       11 : The method according to  claim 10 , wherein the signals comprise data from sensors which measure at least one of the movement of the floating unit and the pressure in the riser.