Patent ID: 6237693
Filing Date: 2001-05-29
Classification: E21B,Y10T

Abstract:
A subsurface well safety valve for controlling the fluid flow through a well conduit,ocomprising:a housing defining a bore and a cylinder offset from the bore;a valve closure member selectively movable between an open position and a closed position adapted to control the fluid flow through the bore;a flow tube telescopically, moveably mounted in the housing, the flow tube adapted to control the movement of the valve closure member;a piston assembly positioned in the cylinder, the piston assembly connected to the flow tube;the piston assembly having a first end communicating with a fluid control passageway to the well surface;a reference chamber in the housing, the reference chamber communicating with a second end of the piston assembly and acting on the piston assembly in a direction to close the valve;a first seal and a second seal of the piston assembly adapted to isolate the pressure in the cylinder above and below the respective first and second seals from the pressure in the bore; andthe piston assembly further comprising:a first piston having a piston bore therethrough;a second piston at least a portion of which is moveably mounted within the piston bore;a piston valve attached to the first piston, the piston valve adapted to provide selective control of fluid flow through the piston bore;a release mechanism adapted to releasably attach the first piston to the second piston; anda spring biasing the first piston and the second piston to a first position and selectively biasing the piston valve to an open position.