Patent ID: 7331392
Filing Date: 2008-02-19
Classification: E21B

Abstract:
1. A method for controlling flow through a valve comprising: providing a valve body having an inlet and an outlet and a main piston axially movable in a valve bore in the valve body between an open position wherein the inlet is in fluid communication with the outlet and a closed position wherein the main piston blocks the outlet from the inlet, a first high pressure (HP) trigger piston movable within the main piston and in fluid communication with the inlet and providing a first locking element movable to alternately straddle to engage between a first release recess in the HP trigger piston and a first port in the main piston and straddle to engage between the first port and at least one annular locking groove in the valve body, and a second low pressure (LP) trigger piston movable within the main piston and in fluid communication with the inlet and providing a second locking element movable to alternately straddle between an annular second release recess in the LP trigger piston and a second port in the main piston and between the second port and the at least one annular locking groove in the valve body; mechanically biasing the main piston to overcome fluid pressure at the inlet when the fluid pressure is below about a preset high fluid pressure for urging the main piston to the closed position; mechanically biasing the HP trigger piston to overcome fluid pressure at the inlet at fluid pressures lower than about the preset high fluid pressure for urging the HP trigger piston to misalign the first release recess from the first port; mechanically biasing the LP trigger piston to overcome fluid pressure at the inlet at about a preset low fluid pressure for urging the LP trigger piston to align the annular second release recess with the second port, the preset low fluid pressure being at a differential and lower fluid pressure than the preset high fluid pressure; aligning the first port with the at least one annular locking groove in the closed position; mechanically biasing the HP trigger piston to overcome the fluid pressure at the inlet for shifting the HP trigger piston to temporarily misalign the first release recess from the first port wherein the first locking element engages between the at least one locking groove and the first port for releasably locking the main piston to the valve body in the closed position and wherein the HP trigger piston is moveable in the main piston; overcoming the mechanical biasing of the HP trigger piston at about the preset high fluid pressure for shifting the HP trigger piston to shift and temporarily align the first release recess with the first port wherein the first locking element engages between the first release recess and the first port and disengages the at least one locking groove for releasing the main piston from the valve body; and overcoming the mechanical biasing of the main piston at about the preset high fluid pressure for shifting the main piston to the open position and misaligning the at least one locking groove and the first port for locking the HP trigger piston in the main piston; aligning the second port with the at least one annular locking groove when the main piston is in the open position for wherein the second locking element is trapped in the second port and engaged with the at least one annular locking groove for releasably locking the main piston to the valve body in the open position and wherein the LP trigger piston is moveable in the main piston; overcoming the mechanical biasing of the LP trigger piston at fluid pressures above about the second preset fluid pressure for shifting the LP trigger piston for misaligning the second release recess and the second port; mechanically baising the LP trigger piston to overcome the second preset fluid pressure at about the second preset fluid pressure for shifting the LP trigger piston to temporarily align the second release recess with the second port wherein the second locking element engages between the second release recess and the second port and disengages the at least one annular locking groove for releasing the main piston from the valve body and locking the LP trigger piston to the main piston; and mechanically biasing the main piston for shifting the main piston to the closed position and misaligning the at least one annular locking groove and the second port for locking the LP trigger piston in the main piston.