US Patent 7810570 Shock-release fluid fracturing method and apparatus

A shock tool is adapted to a bottom hole tool assembly for isolating a zone in a subterranean formation accessed by a wellbore. Fracturing fluid such as nitrogen is accumulated at fracturing pressures uphole of the shock tool for subsequent and rapid release to the formation. The tool assembly can be suspended from a conveyance string in which fluid is accumulated for shock release through a valve of the shock tool and through an injection tool to the zone isolated by the injection tool. After a first zone is shocked, the tool assembly can be moved to a new zone, or multiple shocks can be applied cyclically at the selected zone.