STEERABLE EARTH BORING ASSEMBLY HAVING FLOW TUBE WITH STATIC SEAL

摘要

A steerable earth boring assembly which includes an annular collar and a drive shaft with a drill bit, where the shaft pivots with respect to the collar. An upstream portion of the shaft inserts into an orientation sleeve which resides in the collar. An axial bore is obliquely formed through the sleeve, and in which the upstream portion inserts. Rotating the sleeve causes precession of the upstream portion, thereby pivoting the drill bit obliquely to the collar. Selective rotation of the sleeve orients the drill bit into a designated orientation for forming a deviated wellbore. Included in the assembly is a flow tube with an end in sealing contact with the drive shaft.