US Patent 9745830 Failsafe subsurface controlled safety valve

Embodiments of the invention generally relate to a failsafe subsurface controlled safety valve. In one embodiment, a failsafe subsurface controlled safety valve assembly includes: a tubular housing; a closure member disposed in the tubular housing, wherein the closure member is movable between a closed position and an open position; an operating piston operable to move the closure member between the closed position and the open position; and a trigger piston operable to move the closure member from the open position to the closed position.