Seal for concentric tubular member

摘要

A seal assembly employing a thermoplastic sealing element, such as polytetrafluoroethylene, for maintaining sealing integrity between inner and outer concentric tubular members is disclosed. Axial extrusion of the sealing element through a constricted passage into a cavity adjacent the surface of one of the tubular members is allowed when the sealing element expands due to increased heat or pressure. Axial contraction through this same passage serves to maintain sealing integrity in the vicinity of this passage. The performance of the contracting sealant is improved during a cooling cycle by utilizing a cylindrical seal ring member having a thermal expansion coefficient less than that of the outer tubular member so that the constricted passage formed between the seal ring and the outer tubular member narrows during cooling. This seal assembly is adapted for use in an expansion joint employed in an oil or gas subterranean well.