Multi purpose bottom supported mobile offshore service platform and method

Abstract

A method for abandonment of a production platform includes moving a mobile offshore service platform (MOSP) to a position proximate the production platform. A hull of the MOSP is raised to a selected elevation above a top of the production platform. A cantilever structure having thereon a drilling unit and a crane is extended from a retracted position over the hull until the drilling unit is positioned over at least one well on the production platform. The well is plugged. The cantilever structure is then moved so that the crane is positioned to lift components from the production platform during disassembly of the production platform.

What is claimed is: 
     
         1 . A method for abandonment of a production platform, comprising:
 moving a mobile offshore service platform (MOSP) to a position proximate the production platform;   raising a hull of the MOSP to a selected elevation above a top of the production platform;   extending a cantilever structure having thereon a drilling unit and a crane from a position over the hull until the drilling unit is positioned over at least one well on the production platform;   plugging the at least one well; and   moving the cantilever structure so that the crane is positioned to lift components from the production platform during disassembly of the production platform.   
     
     
         2 . The method of  claim 1  wherein the raising the hull comprises extending a plurality of jacking legs to a bottom of a body of water and continuing the extending until the hull is raised to the selected elevation above a surface of the body of water. 
     
     
         3 . The method of  claim 1  further comprising, after plugging the at least one well, retracting the cantilever structure onto the hull and lowering a mast of the drilling unit prior to moving the cantilever to position the crane. 
     
     
         4 . The method of  claim 1  wherein the cantilever structure further comprises at least one of a wireline well intervention unit, a coiled tubing unit and personnel accommodation devices. 
     
     
         5 . The method of  claim 1  wherein the cantilever structure initially comprises the drilling unit and excludes a crane, and wherein the crane is affixed to the cantilever structure prior to commencement of lifting components. 
     
     
         6 . The method of  claim 5  wherein the cantilever structure initially excluding the crane is removed from the MOSP as a unit. 
     
     
         7 . The method of  claim 5  wherein the cantilever structure having thereon a drilling unit and a crane is attached to the MOSP as a unit. 
     
     
         8 . The method of  claim 5  wherein the cantilever structure excluding the crane and the cantilever structure having the crane each have the same type of attachment components to connect the respective cantilever structures to the MOSP.