Offshore top tensioned riser buoyancy can system and methods of field development

Abstract

A method for developing an offshore field comprises (a) coupling a plurality of top-tensioned risers to a first vessel at a first location. In addition, the method comprises (b) decoupling the first vessel from the plurality of top-tensioned risers after (a). Further, the method comprises (c) coupling a second vessel to the plurality of top-tensioned risers after (b) at the first location.

1 . A method for developing an offshore field, comprising:
 (a) coupling a plurality of top-tensioned risers to a first vessel at a first location;   (b) decoupling the first vessel from the plurality of top-tensioned risers after (a);   (c) coupling a second vessel to the plurality of top-tensioned risers after (b) at the first location.   
     
     
         2 . The method of  claim 1 , wherein (b) further comprises moving the first vessel away from the first location;
 wherein (c) comprises moving the second vessel towards the first location.   
     
     
         3 . The method of  claim 1 , further comprises:
 drilling a subsea well through one of the top-tensioned risers with the first vessel after (a) and before (b); and   producing the subsea well through one of the top-tensioned risers with the second vessel after (c).   
     
     
         4 . The method of  claim 3 , further comprising:
 initiating production from the subsea well through one of the top-tensioned risers with the first vessel after drilling the subsea well with the first vessel.   
     
     
         5 . The method of  claim 4 , further comprising:
 evaluating production from the at least one well after initiating production;   selecting the second vessel based upon the evaluated production from the subsea well; and   deploying the second vessel to the first location so as to replace the first vessel.   
     
     
         6 . The method of  claim 1 , further comprising:
 supporting the top-tensioned risers is a buoyancy can system during (a), (b), and (c).   
     
     
         7 . The method of  claim 6 , wherein (a) comprises:
 (a1) coupling a first cable extending from the first vessel to the buoyancy can system; and   (a2) applying tension to the first cable to move the buoyancy can system into a bay disposed on the outer perimeter of the first vessel.   
     
     
         8 . The method of  claim 7 , wherein (b) comprises:
 (10) reducing the tension on the first cable;   (b2) pulling the first vessel away from the buoyancy can system to remove the buoyancy can system from the bay; and   (b3) decoupling the first cable from the buoyancy can system.   
     
     
         9 . The method of  claim 7 , wherein (c) comprises:
 (18) coupling a second cable extending from the second vessel to the buoyancy can system; and   (c2) applying tension to the second cable to move the buoyancy can system into a bay disposed on the outer perimeter of the second vessel.   
     
     
         10 . A system comprising:
 a relocatable offshore vessel including a hull, a topsides supported by the hull, and a bay disposed along the outer perimeter of the offshore vessel;   a buoyancy can system disposed in the bay, wherein the buoyancy can system supports a plurality of top-tensioned risers; and   a coupling system releasably coupling the vessel to the buoyancy can system.   
     
     
         11 . The system of  claim 10 , wherein the vessel is an adjustably buoyant tower, an adjustably buoyant spar platform, or an adjustably buoyant semi-submersible platform. 
     
     
         12 . The system of  claim 10 , wherein the bay is defined by a pair of support members extending outward from the vessel, wherein each support member comprises a fender for slidably engaging the buoyancy can system. 
     
     
         13 . The system of  claim 12 , wherein each fender includes a plurality of flexible, resilient bumpers configured to engage the buoyancy can system. 
     
     
         14 . The system of  claim 13 , wherein each bumper is made of an elastomeric material with an inner surface comprising an ultra-high-molecular-weight polyethylene. 
     
     
         15 . The system of  claim 10 , wherein the coupling system comprises:
 a winch mounted to the vessel; and   a cable extending from the winch to the buoyancy can system;   wherein the winch is configured to adjust the tension and slack in the cable.   
     
     
         16 . The system of  claim 10 , wherein the buoyancy can system comprises a frame and a plurality of adjustably buoyant buoyancy cans coupled to the frame;
 wherein the top-tensioned risers are coupled to the frame and are positioned between the buoyancy cans.   
     
     
         17 . The system of  claim 16 , wherein a production manifold is disposed on the buoyancy can system. 
     
     
         18 . A method for passing a plurality of top-tensioned risers between a first offshore vessel and a second offshore vessel, the method comprising:
 (a) supporting a plurality of top-tensioned risers with a buoyancy can system;   (b) receiving the buoyancy can system and the top-tensioned risers into a bay disposed along the outer perimeter of the first offshore vessel;   (c) withdrawing the buoyancy can system and the top-tensioned risers from the bay; and   (d) receiving the buoyancy can system and the top-tensioned risers into a bay disposed along the outer perimeter of the second offshore vessel after (c).   
     
     
         19 . The method of  claim 18 , wheren (b) comprises
 (10) coupling a first cable extending from the first vessel to the buoyancy can system; and   (b2) applying tension to the first cable to move the buoyancy can system into a bay disposed on the outer perimeter of the first vessel.   
     
     
         20 . The method of  claim 19 , wherein (c) comprises:
 (18) reducing the tension on the first cable;   (c2) pulling the first vessel away from the buoyancy can system to remove the buoyancy can system from the bay; and   (c3) decoupling the first cable from the buoyancy can system.   
     
     
         21 . The method of  claim 20 , wherein (d) comprises:
 (18) coupling a second cable extending from the second vessel to the buoyancy can system; and   (c2) applying tension to the second cable to move the buoyancy can system into a bay disposed on the outer perimeter of the second vessel.   
     
     
         22 . The method of  claim 21 , wherein the tension in the first cable is controlled by a first winch mounted to the first vessel and tension in the second cable is controlled by a second winch mounted to the second vessel. 
     
     
         23 . The method of  claim 18 , wherein each bay is defined by a pair of support members extending outward from the vessel, wherein each support member comprises a fender for slidably engaging the buoyancy can system. 
     
     
         24 . The system of  claim 23 , wherein each fender includes a plurality of flexible, resilient bumpers configured to engage the buoyancy can system.