Patent ID: 7347270
Filing Date: 2008-03-25
Classification: E21B

Abstract:
1. A subsurface safety valve for controlling a fluid flow through a well conduit comprising: a housing having a bore and disposed within an annulus defined by the space between the well conduit and the housing; a valve closure member movable between an open position and a closed position, and adapted to restrict the fluid flow through the bore when in the closed position; a flow tube moveably disposed within the housing and adapted to shift the valve closure member between its open and closed positions; a primary piston assembly including a primary piston member in sliding relationship with a primary cylinder, the primary piston member in operative communication with the flow tube; a secondary piston assembly including a secondary piston member in sliding relationship with a secondary cylinder, the second piston member in operative communication with the flow tube; and a mechanism to selectively translate the secondary piston member between a first position at which the secondary piston member is not responsive to a control stimulus and a second position at which the secondary piston is responsive to the command stimulus.