| 摘要 |
In a broad aspect, the invention may include a subsurface safety valve for controlling a fluid flow through a well conduit. The valve may include a housing that has a bore and is disposed within an annulus defined by the space between the well conduit and the housing. The valve may also have a valve closure member that is movable between an open position and a closed position, and adapted to restrict the fluid flow through the bore when in the closed position. The valve may also include a flow tube that is moveably disposed within the housing and adapted to shift the valve closure member between its open and closed positions. The valve may also include a piston that is moveably disposed within a cylinder in the housing and in mechanical communication with the flow tube. The piston may have a first seal disposed adjacent an upper end of the piston, a second seal disposed adjacent a lower end of the piston, and a third seal disposed between the first and second seals. The valve may also have a failsafe passageway in fluid communication with a balance pressure line and a portion of the piston between the first and third seals. The invention may also include a detachable piston arrangement that is balanced to the annulus or the surface.
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