Apparatus and method for subsea well drilling and control

Abstract

A subsea assembly suitable for subsea drilling and intervention operations includes a dual blowout preventer system having an upper blowout preventer located between a drill floor and a high pressure riser string, and a lower blowout preventer located below the riser string and above a wellhead. The dual blowout preventer system is adapted to enable advanced drilling and intervention operations such as managed pressure drilling, underbalanced drilling, dual gradient drilling, or through tubing rotary drilling, and slim hole drilling in an offshore deepwater environment.

What is claimed is: 
     
         1 . A subsea assembly for use in the recovery of hydrocarbons located beneath the surface of a body of water, said subsea assembly connecting a floating support structure to a deepwater subsea wellhead, said subsea assembly comprising:
 (a) a rotating control head assembly functionally connected to said floating support structure;   (b) an upper blow out preventer located beneath and functionally connected to said rotating control head assembly;   (c) a high pressure riser string located beneath and functionally connected to said upper blowout preventer said high speed riser string providing pressure integrity to said subsea assembly;   (d) a lower riser package located beneath and functionally connected to said high pressure riser string; and   (e) a lower blowout preventer located beneath said lower riser package, said lower blowout preventer being functionally coupled to a wellhead.   
     
     
         2 . An assembly as defined in  claim 1 , wherein the high pressure riser string has a pressure rating that is the same as a pressure rating of the upper blowout protector and the lower blowout preventer. 
     
     
         3 . An assembly as defined in  claim 2  wherein a pressure rating of the upper blowout preventer, the high pressure riser string, and the lower blowout preventer is at least 10,000 psi. 
     
     
         4 . An assembly as defined in  claim 1 , wherein the subsea assembly is adapted to perform at least one of a managed pressure drilling, underbalanced drilling, dual gradient drilling or through tubing rotary drilling using said rotating control head assembly 
     
     
         5 . An assembly as defined in  claim 1 , wherein the high pressure riser string is sized for running casing having an API size less than or equal to 13⅜″. 
     
     
         6 . An assembly as defined in  claim 1 , wherein said floating support structure is adapted to drill wells in water depths of at least 7,500 ft. 
     
     
         7 . A subsea assembly for use in the recovery of hydrocarbons located beneath the surface of a body of water, said subsea assembly connecting a floating support structure to a deep water subsea wellhead, said subsea assembly comprising:
 (a) a slip joint assembly located beneath and functionally connected to said floating support structure;   (b) a rotating head assembly being functionally connected to said slip joint assembly;   (c) an upper blowout preventer located beneath said rotating control head assembly;   (d) a high pressure riser string located beneath and functionally connected to said upper stress joint;   (e) a lower riser package located beneath and functionally connected to said high pressure riser string;   (f) a lower blowout preventer located beneath and functionally connected to said lower riser package joint; and   (g) a wellhead located beneath the lower blowout preventer;   wherein the pressure rating of said upper blowout preventer, said high pressure riser string, and said lower blowout preventer provide a uniform pressure containment ability from the top to the bottom of said subsea assembly.   
     
     
         8 . An assembly as defined in  claim 7 , wherein said high pressure riser string has a pressure rating that is the same as a pressure rating of said upper blowout preventer and said lower blowout preventer. 
     
     
         9 . An assembly as defined in  claim 7 , wherein the assembly is adapted to perform at least one of a managed pressure drilling, underbalanced drilling, dual gradient drilling or through tubing rotary drilling operation using said rotating control head assembly. 
     
     
         10 . An assembly as defined in  claim 7 , wherein the riser string is sized for running casing having an API size less than or equal to 13⅜″. 
     
     
         11 . An assembly as defined in  claim 7 , wherein the vessel is adapted to drill wells in water depths of at least 7,500 ft. 
     
     
         12 . A subsea assembly for use in the exploration for and recovery of hydrocarbons located beneath the surface of a body of water, said subsea assembly connecting a floating support structure to a deepwater subsea wellhead, said assembly being specifically configured to support dual gradient drilling and underbalanced drilling and related completion and production operations, said subsea assembly comprising:
 (a) an upper assembly located adjacent to and functionally connected to said floating structure, said upper assembly including:
 (i) a slip joint assembly; 
 (ii) a rotating control head assembly; and 
 (iii) an upper blowout preventer, said upper blowout preventer including a plurality of rams; 
   (b) a high pressure riser assembly connecting said upper blowout preventer to a lower riser package, said high pressure riser assembly being configured to permit dual gradient drilling and underbalanced drilling operations and wherein the pressure rating of said high pressure riser assembly is substantially the same as the pressure rating of said upper blowout preventer;   (c) a lower riser package functionally connecting to said high pressure riser assembly to a lower blowout preventer, said lower riser package comprising apparatus for disconnecting said high pressure riser assembly from said lower blowout preventer when an emergency disconnect is required; and   (d) a lower blowout preventer functionally connected to said lower riser package;   wherein said upper blowout preventer, said lower blowout preventer, and said high pressure riser assembly provide uniform pressure rating characteristics of at least 10,000 psi to said subsea assembly from the upper assembly through and including said lower assembly.   
     
     
         13 . The subsea assembly of  claim 12  wherein said rotating control head assembly includes:
 (a) a rotating control head; 
 (b) a high pressure spacer joint; 
 (c) a load ring, and 
 (d) a flange assembly. 
 
     
     
         14 . The subsea assembly of  claim 12  wherein said upper assembly includes:
 (a) a diverter assembly, 
 (b) a flex joint, and 
 (c) a slip joint assembly. 
 
     
     
         15 . A method for use in a subsea operation, the method comprising the steps of:
 (a) providing a slip joint assembly located beneath a vessel floor;   (b) providing a rotating control head located beneath the slip joint assembly;   (c) providing an upper blowout preventer located beneath the rotating control head;   (d) providing an upper stress joint located beneath the upper blowout preventer;   (e) providing a high pressure riser string located beneath the upper stress joint;   (f) providing a lower stress joint located beneath the riser string;   (g) a lower blowout preventer located beneath the lower stress joint; and   (h) providing a wellhead located beneath the lower blowout preventer; wherein the pressure rating of said upper blowout preventer, said high pressure riser string, and said lower blowout preventer provide a uniform pressure containment ability from the top to the bottom of said subsea assembly.   
     
     
         16 . A method as defined in  claim 15 , wherein step (e) further comprises the step of providing the high pressure riser string with a pressure rating that is the same as a pressure rating of said upper blowout preventer and said lower blowout preventer. 
     
     
         17 . A method as defined in  claim 15 , further comprising the step of performing at least one of a managed pressure drilling, underbalanced drilling, dual gradient drilling or through tubing rotary drilling using said rotating control head assembly. 
     
     
         18 . A method as defined in  claim 15 , further comprising the step of tripping a liner having an API size less than or equal to 13⅜″ through the riser string.