Patent ID: 7325616

Claim:
A system for use in a wellbore having a plurality of well zones, comprising: a casing deployed in the wellbore and suspended from a wellhead, the casing fixed to the wellbore by cement; and a plurality of valves connected to the casing, each valve adapted to isolate a selected well zone from at least one other well zone located downhole from the selected wellzone; the valve comprising: a housing having an axial bore therein; a flapper arranged within the housing, the flapper being moveable between an open position wherein communication via the axial bore of the housing is uninterrupted and a closed position wherein communication via the axial bore of the housing is interrupted; and an actuator for moving the flapper from the open position to the closed position, the actuator comprising an energy supplying device connected to the flapper to provide energy to move the flapper from the open position to the closed position, a sleeve arranged within the axial bore of the housing and adapted to engage the flapper and prevent the flapper from moving to the open position, a piston element formed on the sleeve and protruding radially outward, a sealed chamber arranged proximate the housing, the chamber having an internal pressure less than pressure of the wellbore, and a conduit connecting the chamber to the axial bore of the housing behind the piston element of the sleeve.