Downhole activation circuit valving

Abstract

A downhole valve for use within a string of tools in a well for controlling a hydraulic activation circuit. The valve has a housing with an inlet and an outlet, defining a portion of the circuit extending between the inlet and the outlet. A moveable piston within the housing in a first position provides communication between uphole and downhole parts of the circuit, and in a second position isolates the uphole and downhole parts of the circuit. A frangible member is constructed to support, in an intact condition, the piston in one of these two positions against a biasing force, and in a shattered condition enables the piston to move in response to the biasing force to the other position. A detonating member extending through the frangible member propagates a detonation wave to shatter the frangible member when desired, closing the valve. The valve is capable of closing very rapidly, and is particularly useful for isolating an uphole part of a hydraulic activation circuit when used with detonatable tools that can damage hydraulic control lines upon detonation, such as perforating guns. In other embodiments the valve is used to enable hydraulic activation of a tool when opened by a detonation. Methods of altering a hydraulic activation circuit within a string of tools in a well are also disclosed.