Apparatus and method for maintaining relatively uniform fluid pressure within an expandable well tool subjected to thermal variants

An thermal compensating apparatus for maintaining a relatively constant fluid pressure within a subterranean well tool of the type that includes a bladder that is selectively expandable upon the introduction of pressurized actuation fluid, for activating said tool at a location in a well, said apparatus comprising:

• (a) a body with a longitudinal axis, said body being adapted for connection to the well tool;
• (b) a mandrel in the body, said mandrel being movable along the longitudinal axis relative to the body;
• and
• (c) a compression spring, one portion of which is fixed relative to the mandrel;
• (d) a fluid chamber located between the body and mandrel, said fluid chamber being in communication with actuation fluid used for activating the tool;
• and
• (e) a piston located between the fluid chamber and compression spring movable in response to pressure changes in the actuation fluid, the piston being adjusted so that increases in fluid pressure will tend to move the piston and store energy in the spring, and decreases in fluid pressure will tend to cause the spring to release energy and move the piston, for effecting changes in the size of the fluid chamber and maintaining a relatively constant pressure in the actuating fluid when the fluid is subjected to pressure variants.

A thermal compensating apparatus for maintaining a relatively constant fluid pressure within a subterranean well tool of the type that is responsive to a source of actuation fluid for manipulating said tool at a location in a well to at least one of sealing and anchoring positions, said apparatus comprising:

• (a) a body;
• (b) a fluid chamber within said body for housing a substantially incompressible fluid for manipulating said tool to at least one of said positions;
• (c) the fluid chamber being expandable and contractible in response to manipulation of said tool and thereafter in response to thermal variations of said fluid in said fluid chamber;
• and
• (d) an energy storage and release mechanism responsive to pressure changes in the fluid chamber and adapted to allow for expansion or contraction of the fluid chamber in response to thermal variations in the fluid so as to maintain the fluid at a relatively constant pressure, the mechanism including a compressible element positioned relative to said fluid chamber such that said compressible element compresses to store energy transferred thereto from the fluid or expands to release energy transferred thereto from the fluid.