Patent ID: 8739881

Claim:
A flapper valve assembly, comprising: a tubular housing having a storage cavity defined therein and including a valve seat, the tubular housing configured to connect to a wellbore casing; a sleeve moveable between a first position and a second position, wherein the sleeve in the first position covers the storage cavity and the sleeve in the second position at least partially uncovers the storage cavity; a flapper valve disposed in the tubular housing, wherein the flapper valve is contained in the storage cavity when the sleeve is in the first position, and wherein the flapper valve is pivotable between an open position and a closed position when the sleeve is in the second position; a first biasing member engaging the tubular housing and the flapper valve; a second biasing member coupling the flapper valve to the tubular housing, wherein the first biasing member and the second biasing member are configured to bias the flapper valve toward the valve seat; wherein the first biasing member is coupled to a periphery of the flapper valve at a first location and the second biasing member is coupled to the periphery of the flapper valve at a second location, wherein the first and second locations are between about 90 and about 180 degrees apart; and a pressurized chamber in fluid communication with the sleeve and adapted to apply a hydrostatic force on the sleeve such that the sleeve moves longitudinally from the first position to the second position.