Abstract: A valve and valve assembly are provided to allow opening of flow channels through the wall of a tubular by increasing and then decreasing pressure in the tubular. Slidable seals having different areas are used to apply an axial force to a shuttle in the valve in response to differential pressure across the valve when in the closed position. The axial force shears a pin, releasing the shuttle. A decrease of pressure in the tubular can allow the valve to open in response to a spring force. Multiple valves may be placed along a tubular string and the valves may be opened all at substantially the same time or at time intervals determined by pressures applied inside the tubular.

Abstract: An integral multistage safety valve is designed to provide a second level of protection should a first stage fail. The valve may be used in oil and/or gas wells. The interior portion of the multiphase safety valve is designed so as to reduce turbulence and pressure loss through the valve when the valve is in an open position. The valves may be independently operable, or operable with a single control line. The multi-stage valve reduces the number of body joints required to construct two identical valves thereby reducing cost and potential leak paths and increasing reliability of the system.

Abstract: A subsurface safety valve is operable to close a fluid flow path by virtue of an axially movable flow sleeve. The valve includes a recockable linear actuator and a latch mechanism so that the valve can be moved from an open to a closed position as a result of axial movement of the flow sleeve without overcoming the pressure head and frictional forces currently encountered in conventional safety valves.

Abstract: Apparatus and method are provided for placing a dual pressure barrier in a vertical or horizontal well and verifying by pressure sensors in the well that the pressure barriers are operable. Communication of data from the well may be by electromagnetic or acoustic signals, and the data may be acquired on a ship near the well.