Patent ID: 7252150
Filing Date: 2007-08-07
Classification: E21B

Abstract:
1. A downhole tool for use in a downhole tool assembly, the tool comprising: a first body and a second body, the bodies being mounted for relative rotation; a joint part adapted to form a selectively releasable joint between the second body and a part of the assembly couplable to the second body; and locking means for locking the first and second bodies relative to one another against relative rotation; whereby, in use, locking said bodies relative to one another facilitates application of a release force through the first body to the releasable joint to release said joint so as to thereby separate the tool from said part of the assembly, wherein the joint comprises a threaded male pin and a co-operating threaded female box, and wherein the threads on the pin and box of the joint are configured such that: where the tangent of the helix angle (α) is determined by: where r m is the thread mean radius.