US Patent 9464507 Casing valves system for selective well stimulation and control

A valve for use in a tubular string in a subterranean well includes a sleeve having first and second opposite ends, the sleeve being displaceable between open and closed positions to thereby selectively permit and prevent flow through a sidewall of a housing assembly, and a first and second pistons at the respective first and second ends of the sleeve. Pressure differentials applied to the first and second pistons are operative to displace the sleeve between its open and closed positions.