Assembly and method for subsea well drilling and intervention

Abstract

An assembly suitable for subsea drilling and intervention operations includes a dual blow out preventer system having an upper blow out preventer located between a drill floor and a riser string, and a lower blow out preventer located below the riser string and above a wellhead. The dual BOP system is adapted to enable advanced drilling and intervention operations such as Managed Pressure Drilling (“MPD”), Underbalanced Drilling (“UBD”), or Through Tubing Rotary Drilling (“TTRD”) in an offshore deepwater environment.

1 . A subsea assembly for use in subsea operations, the assembly comprising:
 a slip joint assembly located beneath a vessel floor;   a rotating control head located beneath the slip joint assembly;   an upper blow out preventer (“UBOP”) located beneath the rotating control head;   an upper stress joint located beneath the UBOP;   a riser string located beneath the upper stress joint;   a lower stress joint located beneath the riser string;   a lower blow out preventer (“LBOP”) located beneath the lower stress joint; and   a wellhead located beneath the LBOP.   
     
     
         2 . An assembly as defined in  claim 1 , wherein the riser string has a pressure rating that is the same as a pressure rating of the UBOP and LBOP. 
     
     
         3 . An assembly as defined in  claim 1 , wherein the assembly is used in an offshore deepwater environment. 
     
     
         4 . An assembly as defined in  claim 1 , wherein the assembly is adapted to perform at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation. 
     
     
         5 . An assembly as defined in  claim 1 , wherein the 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 the vessel has a length of no more than 148 meters and a width of no more than 28 meters. 
     
     
         7 . An assembly as defined in  claim 1 , wherein the vessel is adapted to drill wells in water depths of at least 7,500 ft. 
     
     
         8 . 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 blow out preventer (“UBOP”) located beneath the rotating control head;   (d) providing an upper stress joint located beneath the UBOP;   (e) providing a riser string located beneath the upper stress joint;   (f) providing a lower stress joint located beneath the riser string;   (g) a lower blow out preventer (“LBOP”) located beneath the lower stress joint; and   (f) providing a wellhead located beneath the LBOP.   
     
     
         9 . A method as defined in  claim 8 , wherein step (e) further comprises the step of providing the riser string with a pressure rating that is the same as a pressure rating of the UBOP and LBOP. 
     
     
         10 . A method as defined in  claim 8 , further comprising the step of performing the subsea operation in an offshore deepwater environment. 
     
     
         11 . A method as defined in  claim 8 , further comprising the step of performing at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation. 
     
     
         12 . A method as defined in  claim 8 , further comprising the step of tripping a liner having an API size less than or equal to 13⅜″ through the riser string. 
     
     
         13 . A method as defined in  claim 8 , further comprising the step of providing the vessel with a length of no more than 148 meters and a width of no more than 28 meters. 
     
     
         14 . A subsea assembly for use in subsea operations, the assembly comprising:
 an upper blow out preventer (“UBOP”) located beneath a vessel floor;   a riser string located beneath the UBOP; and   a lower blow out preventer (“LBOP”) located beneath the riser string and operatively coupled to a wellhead.   
     
     
         15 . An assembly as defined in  claim 14 , wherein the riser string has a pressure rating that is the same as a pressure rating of the UBOP and LBOP. 
     
     
         16 . An assembly as defined in  claim 14 , wherein a pressure rating of the UBOP, riser string, and LBOP is at least 10,000 psi. 
     
     
         17 . An assembly as defined in  claim 14 , wherein the assembly is used in an offshore deepwater environment. 
     
     
         18 . An assembly as defined in  claim 14 , wherein the assembly is adapted to perform at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation. 
     
     
         19 . An assembly as defined in  claim 14 , wherein the riser string is sized for running casing having an API size less than or equal to 13⅜″. 
     
     
         20 . An assembly as defined in  claim 14 , further comprising a rotating control head. 
     
     
         21 . An assembly as defined in  claim 14 , wherein the vessel has a length of no more than 148 meters and a width of no more than 28 meters. 
     
     
         22 . An assembly as defined in  claim 14 , wherein the vessel is adapted to drill wells in water depths of at least 7,500 ft. 
     
     
         23 . A method for use in subsea operations, the method comprising the steps of:
 (a) providing a vessel having a floor;   (b) providing an upper blow out preventer (“UBOP”) located beneath the floor;   (c) providing a riser string located beneath the UBOP;   (d) providing a lower blow out preventer (“LBOP”) located beneath the riser assembly; and   (e) connecting the LBOP to a wellhead beneath the LBOP.   
     
     
         24 . A method as defined in  claim 23 , further comprising the step of providing the riser string with a pressure rating that is the same as a pressure rating of the UBOP and LBOP. 
     
     
         25 . A method as defined in  claim 23 , further comprising the step of providing the UBOP, riser string, and LBOP with a pressure rating of at least 10,000 psi. 
     
     
         26 . A method as defined in  claim 23 , further comprising the step of performing the subsea operations in an offshore deepwater environment. 
     
     
         27 . A method as defined in  claim 23 , further comprising the step of performing at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation. 
     
     
         28 . A method as defined in  claim 23 , further comprising the step of tripping liner down the riser string, the liner having an API size less than or equal to 13⅜″. 
     
     
         29 . A method as defined in  claim 23 , further comprising the step of locating a rotating control head beneath the UBOP. 
     
     
         30 . A method as defined in  claim 23 , wherein step (a) further comprises the step of providing the vessel with dimensions of no more than 148 meters in length and no more than 28 meters in width. 
     
     
         31 . A method as defined in  claim 23 , further comprising the step of drilling a well at a water depth of at least 7,500 ft. 
     
     
         32 . A subsea assembly for use in subsea operations, the assembly comprising:
 a vessel having a floor; and   a riser string located beneath the floor, wherein the assembly is adapted to perform at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation.   
     
     
         33 . An assembly as defined in  claim 32 , wherein the assembly further comprises:
 an upper blow out preventer (“UBOP”) located above the riser string;   a lower blow out preventer (“LBOP”) located below the riser string; and   a wellhead located beneath the LBOP.   
     
     
         34 . An assembly as defined in  claim 32 , wherein the riser string is adapted to withstand at least 10,000 psi. 
     
     
         35 . A method for use in subsea operations, the method comprising the steps of:
 (a) providing a vessel having a floor;   (b) providing a riser string located beneath the floor; and   (c) performing at least one of a Managed Pressure Drilling, Underbalanced Drilling, or Through Tubing Rotary Drilling operation.   
     
     
         36 . A method as defined in  claim 35 , further comprising the steps of:
 providing an upper blow out preventer (“UBOP”) located above the riser string;   providing a lower blow out preventer (“LBOP”) located beneath the riser string; and   providing a wellhead located beneath the LBOP.   
     
     
         37 . A method as defined in  claim 35 , further comprising the step of adapting the riser string to withstand at least 10,000 psi.