DOWNHOLE CLUTCH WITH FLOW PORTS

摘要

A drill string tool (1) for use in a wellbore formed in an earth formation i s provided. The tool comprises a first element (1A) connectable to an upper drill string part (3) a second element (5) connectable to a lower drill string part (7) bearing means (11) allowing rotation of the first element relative to the second element about the longitudinal axis (9) of the drill string, and rotation transfer means (15) for transferring rotation of the first element about the longitudinal axis to the second element. Furthermore there is provided contr ol means (28) for selectively disengaging said rotation transfer means so as to selectively allow the first element to rotate relative to the second element by virtue of said bearing means.