Patent ID: 7810570

Claim:
A method for fracturing subterranean formations penetrated by a wellbore comprising: accessing the formation with a conveyance string having a bore and extending downhole through the wellbore for conveying a tool to the formation; isolating a zone with the tool, the tool having an uphole seal and a downhole seal spaced uphole and downhole of the isolated zone; closing the bore of the conveyance string at a valve at the tool, the valve having a main piston which is biased to close the valve and is pressure-actuated to open the valve, the closing of the bore accumulating a gaseous fracturing fluid along an entirety of the conveyance string or wellbore uphole of the valve, the gaseous fracturing fluid being accumulated to a threshold pressure; opening the bore of the conveyance string at the valve at the threshold pressure, the opening of the bore further comprising pressure-actuating a poppet piston at the threshold pressure for triggering unlocking of the main piston, pressure-actuating the unlocked main piston to overcome the main piston biasing for opening the valve so as to communicate with the isolated zone for releasing the accumulated gaseous fracturing fluid, from along substantially the entirety of the conveyance string or the wellbore uphole of the valve, to the isolated zone to shock fracture the formation; and closing the valve comprising biasing the main piston closed at the resetting pressure; and resetting the poppet piston with the main piston closed for locking the main piston closed.