Shear and seal system for subsea applications

Abstract

A system and methodology facilitates utilization of a valve and a cutter both of which may be used in a subsea test tree. The valve comprises a ball element pivotably mounted in a housing and having an exterior surface and a passageway sized to receive a conveyance therethrough. The cutter also is located in the housing but at a position spaced from the ball element. The cutter is oriented for selective severing of the conveyance. Additionally, a seal system is positioned to act against a surface of the ball element.

What is claimed is: 
     
         1 . A system for use in a subsea test tree, comprising:
 a subsea test tree housing having a passageway sized to receive a conveyance therethrough;   a cutter mounted along the passageway, the cutter comprising a plurality of cutter blades selectively movable into the passageway by a plurality of pistons at a shear location;   a valve mounted along the passageway separate from the cutter, the valve being a ball valve having a ball with a ball passage sized to receive the conveyance therethrough; and   a seal member positioned to seal against an outer surface of the ball when the ball is pivoted to a position closing off flow along the passageway, the distance between the seal and the shear location being less than 10 inches (25.4 cm).   
     
     
         2 . The system as recited in  claim 1 , wherein the ball comprises a relief area positioned to allow the ball to start closing before the conveyance is pulled clear of the ball passage. 
     
     
         3 . The system as recited in  claim 2 , wherein the ball has a rounded leading edge at the ball passage and the ball is biased with a low biasing force against the conveyance, the low force of the bias, the relief area, and the rounded leading edge cooperating to enhance the strip through capability of the valve. 
     
     
         4 . The system as recited in  claim 1 , wherein the ball valve is actuated by rod pistons. 
     
     
         5 . The system as recited in  claim 1 , wherein the seal member is positioned in a floating seal retainer. 
     
     
         6 . The system as recited in  claim 1 , wherein the seal member comprises a plurality of seals located on opposite sides of the ball. 
     
     
         7 . The system as recited in  claim 1 , wherein the cutter and the valve are mounted in a common housing. 
     
     
         8 . The system as recited in  claim 1 , wherein the ball is biased into engagement with the seal member. 
     
     
         9 . The system as recited in  claim 1 , wherein the distance between the seal and the shear location is less than 5 inches (12.7 cm). 
     
     
         10 . The system as recited in  claim 1 , wherein the distance between the seal and the shear location is less than 4 inches (10.2 cm). 
     
     
         11 . A method of shutting in a well, comprising:
 positioning a valve along a flow path through a subsea test tree;   providing the valve with a ball pivotable between open and closed positions with respect to the flow path;   locating a cutter along the flow path to create a shear location for cutting of a conveyance positioned in the flow path and through the ball; and   arranging a seal member to seal off the flow path by sealingly engaging the ball at a location less than 10 inches (25.4 cm) from the shear location.   
     
     
         12 . The method as recited in  claim 11 , wherein arranging comprises arranging the seal member to engage the ball at a location less than 5 inches (12.7 cm) from the shear location. 
     
     
         13 . The method as recited in  claim 11 , wherein arranging comprises arranging the seal member to engage the ball at a location less than 4 inches (10.2 cm) from the shear location. 
     
     
         14 . The method as recited in  claim 11 , further comprising cutting a coiled tubing conveyance with the cutter and then pivoting the ball prior to withdrawal of the coiled tubing from an internal passage of the ball. 
     
     
         15 . The method as recited in  claim 11 , further comprising cutting a wireline conveyance with the cutter and then pivoting the ball prior to withdrawal of the coiled tubing from an internal passage of the ball. 
     
     
         16 . The method as recited in  claim 11 , wherein locating the cutter comprises providing piston mounted cutter blades oriented for selective movement into the flow path. 
     
     
         17 . The method as recited in  claim 11 , wherein arranging the seal member comprises utilizing seals on opposite sides of the ball. 
     
     
         18 . A system, comprising:
 a valve comprising:
 a ball valve element rotatably mounted in a housing, the ball valve element having an exterior surface and a passageway sized to receive a conveyance therethrough; 
 a cutter located in the housing at a position spaced from the ball valve element and oriented for selective severing of the conveyance; and 
 a seal system positioned to act against a surface of the ball valve element. 
   
     
     
         19 . The system as recited in  claim 18 , wherein the cutter comprises at least one blade mounted on at least one piston. 
     
     
         20 . The system as recited in  claim 18 , wherein the ball valve element is actuated by rod pistons.