System and method for forming an underground bore

摘要

A system for drilling a substantially horizontal borehole, comprises a rotating drill string extending from a surface system to a location in the horizontal borehole, the drill string having a drill bit at a bottom end. A rotary steerable system in the drill string proximate the drill bit is adapted to direct the rotating drill string toward a desired exit point. In another aspect, a method for drilling a substantially horizontal borehole from a surface location to an offshore exit location, comprises drilling a borehole using a rotary steerable system to direct the borehole along a predetermined trajectory toward the exit location. The borehole is reamed from the surface location toward the exit location while recovering a drilling fluid at the surface location.