the lower annulus 150 b to the outer annulus 155 during a drilling operation the annulus control valve 145 is in the open position drilling fluid is pumped into the drill string 190 and exits through nozzles in the drill bit 165 the return fluid consisting of drilling fluid and hydrocarbons produced into the wellbore is urged up the liner 105 into the lower annulus 150 b formed between the drill string 190 and the inner casing 185 by formation pressure the rch 115 stops the upward flow of return fluid in the lower annulus 150 b forcing it toward the annulus return valve 145 the return fluid is selectively communicated between the lower annulus 150 b and the outer annulus 155 through the ports in the annulus return valve 145 upon entering the outer annulus 155 the fluid is urged upward exiting out a return port 125 at the surface of the wellhead the preferred embodiment has several safety features for example during a drilling operation the annulus return valve 145 can be closed using a surface control device thereby causing the well to be shut in downhole therefore no return fluid is communicated to the outer annulus 155 from the inner annulus 150 and the seal formed between the rch 115 and the drill string 190 prevents return fluid from continuing up the inner annulus 150 another example the surface rch 110 situated below the rig floor is completely isolated from the return fluid fluid pressure below the surface rch 110 increases only if the downhole rch 115 develops a leak causing.