Pressure actuated pack-off and method

Abstract

Mechanism for achieving the radial expansion of an annular elastomeric pack-off unit between the bore of a casing and the exterior of a liner, comprises a tubular sealing assembly threadably connected between the liner and the hanger and defining two inwardly projecting annular seals, an annular fluid pressure chamber, and radially disposed fluid inlet ports for the fluid pressure chamber located between the two inwardly projecting annular seals. An annular piston mounted in the annular pressure chamber effects the compressible expansion of an annular elastomeric seal element. A tubing extension of the work string is provided which may be selectively moved into sealing relationship with either or both of the internally projecting annular seals. During the cementing operation, the tubing extension engages both annular seals. After cementing, the tubing extension may be elevated by the work string to disengage from the lowermost one of the internally projecting annular seals and permit fluid pressure to be applied through the radial ports to the actuating piston. A backup or alternate method of operation is provided through the incorporation of radial ports in the work string pipe extension which are normally covered by a valve sleeve shearably secured to the pipe extension.