Multi-stage pressure equalization valve assembly for subterranean valves

摘要

A downhole valve that operates on turning of a member having a passage through it with a control system also features a passage from above an uphole seat for the member which communicates to the isolated passage within the member when the valve is closed. The passage features a check valve assembly that preferably has redundant sealing features and filters to prevent debris entry. Pressure applied from above the closed member gets through the check valve assembly to equalize the higher pressure below the ball with the pressure raised in the ball from pressure application at the surface. Removal of the applied pressure reseats the check valve or valves to allow the hydraulic system to rotate the member while the member is no longer subject to a high differential pressure.