US Patent 7677334 Anti-surge/reverse thruster

An anti-surge/reverse thrusting tool for reducing the forces on a drill bit used in subterranean well drilling operations along with methods for drilling wells using a drill string employing the tool. The tool utilizes the pressure differential between drilling fluid flowing through the tool and the fluid located in the well bore annulus proximate the tool to reduce the likelihood of drill bit stall. The tool generally comprises an outer housing and a piston assembly that is axially shiftable relative to the housing.