Patent ID: 9260919
Filing Date: 2016-02-16
CPC Classification: E21B,Y10T

Claim Text:
1. An apparatus for aligning a mast assembly, comprising: a rig carrier; a blow out preventer (BOP) stack comprising a bore, wherein said BOP stack is positioned above a wellhead and below said mast assembly; said mast assembly pivotally mounted to said rig carrier, wherein said mast assembly is moveable between a lowered position and an upright position with respect to said rig carrier, and wherein said mast assembly extends over a back end of said rig carrier when raised to said upright position; a top drive mounted on said mast assembly, wherein said top drive is constrained to move along a fixed axial path; and at least one sensor for aligning said fixed axial path of said top drive with an axis of said bore of said BOP stack for drilling operations, wherein said at least one sensor comprises a sender and a receiver respective of which are mounted to different elements selected from a group consisting of said mast assembly, said wellhead, a snubbing stack, a pressure control equipment, said BOP stack, and said top drive.