| 摘要 |
An annular packoff assemblage is provided for selective engagement with any one of a plurality of casing seal bore receptacles spaced along a casing string. The packoff assemblage includes an upper latching assemblage for cooperation with an upwardly facing no-go shoulder providing in the selected seal bore receptacle, an intermediate annular sealing assemblage for establishing sealing integrity between an inner mandrel and the polished internal bore of the selected seal bore receptacle, and a lower latching assemblage movable into latching engagement with the downwardly facing surface provided at the end of the seal bore of the casing receptacle. In two embodiments of the invention, upward movement of the tubing string, followed by a turning movement and a downward movement will effect the releasing of both the upper and lower latching elements to move outwardly into latching engagement with the respective surfaces in the selected casing receptacle. In another modification of the invention, the upper latching assembly includes a collet whose ring portion functions as a piston in a fluid pressure chamber so that it may be moved to a latching position through the application of fluid pressure within the bore of the mandrel.
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