Importance

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Abstract

A locking mandrel is provided for use in downhole assembly and comprises a cylindrical body (12) having an annular series of openings (20) in which locking keys (21) are movably positioned, the keys (21) being biased radially inwardly, and an inner mandrel (13, 14) for moving the keys (21) from a withdrawn primed condition to an extended set position. Additionally the body (12) includes a series of movable no-go members (22) below the keys (21) which are extended in the primed condition so as to be engageable with a no-go ring (R2) on a downhole tubing string to axially arrest the body. The outer surface of the inner mandrel (13, 14) is suitably profiled, and the arrangement is such that with the no-go members (22) engaging the no-go ring, the inner mandrel (13, 14) is movable relative to the body (12) preferably after a shear member (15) between the body and the mandrel has ruptured, to shift the keys (21) radially to the set position where the keys (21) engage on a receiving formation (R1) of the tubing string, and after this setting to cause the no-go member (22) to move radially inwardly and free from the no-go ring (R2). Any axial load is then taken substantially fully through the keys (21). The no-go members comprise flexible fingers formed in the cylindrical body so as to be integral with the body.

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First Claim