Shape Memory Alloy Closure Spring for Subsurface Safety Valves Triggered by Well Fluids

摘要

A shape memory material is used for a power spring in a subsurface safety valve. The spring is sized for the force it will deliver when it goes past its transition temperature and reverts to an original shape. The force released by having the spring pass its transition temperature holds the valve closed against hydrostatic pressure. Since the force exerted by the spring does not increase as the valve opens less force is required to hold the valve in the open position, thus lowering opening pressure. The trigger to cross the transition temperature comes from the expected temperature of well fluids at the mounting position of the subsurface safety valve. Other downhole applications are anticipated.