Patent ID: 7836975

Claim:
A bottom hole assembly for drilling a cavity, wherein the bottom hole assembly comprises: a chassis configured to rotate, wherein the chassis comprises: a conduit configured to accept a first flow of a primary fluid; a substantially closed loop circuit having a second flow of a secondary fluid; a pressure transfer device configured to transfer pressure between the first flow of the primary fluid and the second flow of the secondary fluid; a plurality of pistons operably coupled with the substantially closed loop circuit, wherein the plurality of pistons comprises a first piston, and the first piston is configured to move based at least in part on a pressure of the circuit at the first piston; a plurality of valves operably coupled with the substantially closed loop circuit, wherein the plurality of valves is configured to control a pressure of the substantially closed loop circuit at each of the plurality of pistons and wherein each piston has an inlet and outlet valve of the plurality of valves; a plurality of cutters in proximity to an outer surface of the chassis, wherein each of the plurality of cutters is coupled with one of the plurality of pistons; and wherein the second flow of the secondary fluid comprises a smart fluid.