Hydrostatic flapper stimulation valve and method

A completion for a wellbore, comprising:

• a casing string having one or more segments;
• one or more isolation devices coupled to one or more of the casing string segments;
• and
• one or more flapper valve assemblies coupled to one or more of the casing string segments, wherein each flapper valve assembly comprises:
• a tubular housing having an inner bore and a valve seat;
• a sleeve disposed in the inner bore and configured to move between a first position and a second position within the tubular housing;
• a flapper valve coupled to the tubular housing, wherein the flapper valve is stationary when the sleeve is in the first position, and 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 pivotally 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 around the periphery of the flapper valve;
• and
• a pressurized chamber disposed within the inner bore of the tubular housing in fluid communication with the sleeve, wherein the pressurized chamber is adapted to apply a hydrostatic force on the sleeve upon activation of the downhole tool to move the sleeve from the first position to the second position.

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;
• and
• wherein the first biasing member is coupled to a distal end of the flapper valve and the second biasing member is coupled to a proximal end of the flapper valve, wherein the proximal and distal ends are substantially opposing, and wherein the second biasing member is a pivot pin-and-spring assembly.