Safety System for Deep Water Drilling Units Using a Dual Blow Out Preventer System

Abstract

A dual-BOP or multi-BOP self-standing riser configuration is disclosed, including at least a riser or another similarly fixed tubular structure disposed in communication with an associated drilling vessel and a subsurface well. The system supplements the traditional mud-line level BOP with one or more additional near-surface BOPs, which are tensioned using an adjustable buoyancy chamber rather than by means of a vessel-born tensioning device.

1 . A self-standing riser system, said system comprising:
 a subsurface well disposed in communication with a first BOP;   a riser assembly disposed in communication with said subsurface well;   an adjustable buoyancy chamber disposed in communication with said riser assembly; and   a second BOP disposed in communication with said riser assembly located above said adjustable buoyancy chamber.   
     
     
         2 . The system of  claim 1 , wherein said second BOP is also disposed in communication with a surface vessel. 
     
     
         3 . The system of  claim 1 , wherein said first BOP further comprises a plurality of BOPs. 
     
     
         4 . The system of  claim 1 , wherein said second BOP further comprises a plurality of BOPs. 
     
     
         5 . The system of  claim 1 , wherein each of said first BOP and said second BOP further comprise a plurality of BOPs. 
     
     
         6 . The system of  claim 1 , further comprising a water-proof chamber disposed around said second BOP. 
     
     
         7 . The system of  claim 1 , wherein said adjustable buoyancy chamber is used to tension said riser assembly to a depth at which a human diver can service or replace said second BOP. 
     
     
         8 . The system of  claim 1 , wherein said adjustable buoyancy chamber is used to tension said riser assembly such that said second BOP is lifted to approximately the same height as the surface of a surrounding body of water. 
     
     
         9 . The system of  claim 1 , wherein said riser system is restrained in place using a fixed anchoring system. 
     
     
         10 . The system of  claim 1 , wherein said riser system is positioned relative to said wellhead using dynamic positioning.