Internal drilling riser centralizer

Abstract

The method of centralizing a rotating string within the bore of a subsea blowout preventer stack and a drilling riser comprising providing a multiplicity of rollers having a first position and a second position, when the rollers are in the first position the rollers defining a first circle which is proximately the size of the bore of the drilling riser, when the rollers are in the second position the rollers defining a second circle which is smaller than the first circle, and when the rollers are in the second position the rollers prevent the rotating string from contacting the bore of the subsea blowout preventer stack or the drilling riser proximate the rollers.

1 . The method of centralizing a rotating string within the bore of a subsea blowout preventer stack and a drilling riser comprising:
 providing a multiplicity of guides having a first position and a second position,   when said guides are in said first position said guides defining a first boundary which is proximately the size of the bore of the drilling riser,   when said guides are in said second position said guides defining a second boundary which is smaller than said first boundary, and   when said guides are in said second position said guides prevent said rotating string from contacting the bore of said subsea blowout preventer stack or said drilling riser proximate said guides.   
     
     
         2 . The method of  claim 1  further comprising said guides are moved between said first position and said second position by hydraulic cylinders. 
     
     
         3 . The method of  claim 2  further comprising said guides are rollers. 
     
     
         4 . The method of  claim 1  further comprising said guides are rollers. 
     
     
         5 . The method of  claim 1  further comprising said second boundary is proximately a circle. 
     
     
         6 . The method of  claim 5  further comprising said guides are rollers. 
     
     
         7 . The method of  claim 6  further comprising said guides are moved between said first position and said second position by hydraulic cylinders. 
     
     
         8 . The method of  claim 1  further comprising said guides are rollers. 
     
     
         9 . In a subsea drilling system comprising a rotating or translating drilling string of pipe, a subsea blowout preventer stack, and a drilling riser extending to a floating vessel on the surface of the sea, and a flexible joint between said subsea blowout preventer stack and said drilling riser, said subsea blowout preventer stack having a minimum bore size and said drilling riser having a minimum bore size, and said flexible joint allowing said drilling riser bore to not be angularly aligned with said blowout preventer bore such that said rotating or translating drilling string of pipe can wear or “keyseat” the internal area of said subsea blowout preventer stack, said flexible joint, or said drilling riser, the method of preventing said wear or “keyseating” comprising providing a multiplicity of guides having a first position and a second position,
 when said guides are in said first position said guides defining a first boundary which is proximately the size of the bore of the drilling riser, 
 when said guides are in said second position said guides defining a second boundary which is smaller than said first boundary, and 
 when said guides are in said second position said guides prevent said rotating string from contacting the bore of said subsea blowout preventer stack or said drilling riser proximate said guides. 
 
     
     
         10 . The method of  claim 9  further comprising said guides are moved between said first position and said second position by hydraulic cylinders. 
     
     
         11 . The method of  claim 10  further comprising said guides are rollers. 
     
     
         12 . The method of  claim 9  further comprising said guides are rollers. 
     
     
         13 . The method of  claim 9  further comprising said second boundary is proximately a circle. 
     
     
         14 . The method of  claim 13  further comprising said guides are rollers. 
     
     
         15 . The method of  claim 14  further comprising said guides are moved between said first position and said second position by hydraulic cylinders. 
     
     
         16 . The method of  claim 9  further comprising said guides are rollers.