SYSTEM FOR STEERING A DRILL STRING

摘要

In one aspect of the present invention, a drill bit assembly has a body p ortion intermediate a shank portion and a working portion The working portio n has at least one cutting element and at least a portion of a shaft is disp osed within the body portion and protrudes from the working portion The shaf t has a distal end rotationally isolated from the body portion and is in com munication with a subterranean formation A motor is adapted to rotationally control the distal end.