Dual Drilling Activity Drilling Ship

Abstract

A single drilling ship may be equipped with two drilling centers, each capable of running risers. Each drilling center has a set of tubulars stored for use in association with that drilling center, those tubulars including risers. However, the risers for one drilling center are of a smaller diameter than the risers for the other drilling center. In the event that a main drilling center drilled well fails, a relief well can then be drilled from the same ship using a secondary drilling center.

1 . A method comprising:
 outfitting a drilling ship with two separate and distinct drilling centers, each capable of drilling a well; and   providing marine risers for each of said drilling centers, the marine risers for one of the drilling centers being of a smaller diameter than the marine risers for the other of said drilling centers.   
     
     
         2 . The method of  claim 1  including providing storage for marine risers in association with each of said drilling centers. 
     
     
         3 . The method of  claim 1  including providing equipment to enable a relief well to be drilled from the same ship that drilled a failed well. 
     
     
         4 . The method of  claim 1  including, in association with a secondary drilling center having smaller diameter risers, providing two blowout preventers. 
     
     
         5 . The method of  claim 4  including permanently installing riser tensioners on said secondary drilling center. 
     
     
         6 . The method of  claim 1  including connecting risers to a lower blowout preventer using a lower marine riser package. 
     
     
         7 . The method of  claim 6  including providing an upper blowout preventer between said tensioner and said risers. 
     
     
         8 . The method of  claim 4  including providing a lower marine riser package between a blowout preventer on said secondary drilling center and said risers. 
     
     
         9 . The method of  claim 1  including providing a mechanical override emergency riser disconnector on the drilling center with larger diameter risers. 
     
     
         10 . The method of  claim 9  including connecting the disconnector to a lower marine riser package. 
     
     
         11 . The method of  claim 1  including providing a subsea shutoff assembly for the drilling center with the larger diameter risers. 
     
     
         12 . A drilling ship comprising:
 a first drilling center including storage to store first marine risers;   a second drilling center to drill a second well from the same ship, the second drilling center including storage to store second marine risers, said second marine risers having a smaller diameter than said first marine risers.   
     
     
         13 . The ship of  claim 12  to enable a relief well to be drilled from said second drilling center when a well drilled from said first drilling center has failed. 
     
     
         14 . The ship of  claim 12  including two blowout preventers for said second drilling center. 
     
     
         15 . The ship of  claim 14  including a riser tensioner permanently installed on said second drilling center. 
     
     
         16 . The ship of  claim 14  including a lower blowout preventer connected to the marine risers via a lower marine riser package. 
     
     
         17 . The ship of  claim 16  including an upper blowout preventer between said tensioner and said risers. 
     
     
         18 . The ship of  claim 14  including a lower marine riser package between a blowout preventer on said second drilling center and said risers. 
     
     
         19 . The ship of  claim 12  including a mechanical override emergency riser disconnector on the second drilling center. 
     
     
         20 . The ship of  claim 19  including said disconnector connected to a lower marine riser package. 
     
     
         21 . The ship of  claim 12  wherein said second drilling center includes two blowout preventers and said first drilling center includes only one blowout preventer.