Abstract: A stabilizer for use with a string of single tube or dual concentric drill pipe above a bit having analogous tubular members adapted for fluid tight interconnection with the pipes of said string to provide a conduit for drilling fluid. A stabilizer means encircles the stabilizer body and is adapted to contact the hole wall. The stabilizer means includes a sleeve bearing mounted to rotate with respect to the stabilizer body and a stabilizer sleeve mounted stationary on the sleeve bearing. A port means in the stabilizer body provides fluid communication between the drilling fluid conduit and the stabilizer sleeve and/or thrust bearing. An exit port means in the lower end of the stabilizer means provides fluid communication between the stabilizer sleeve bearing and the outside of the stabilizer.

Abstract: A bit packer for use with a string of dual concentric drill pipe, having inner and outer tubular members concentrically arranged to mate with the inner and outer pipes of the drill string to provide an annular conduit for fluid from surface to bit and a central conduit for fluid and cuttings from bit to surface, is particularly characterized by flexible packing means mounted slidably and rotatably on the outer tubular member. The packing means deform against the hole wall to seal the annular space between the outer member and the hole wall. Upper and lower ports provide fluid communication between the annular conduit and the annular space; when the packer is moved downwardly in the hole the packing means slides upwardly to close the upper port and open the lower port; when the packer is moved upwardly in the hole, the converse occurs. A milling collar is provided above the packing means.

Abstract: A system for developing or cleaning a screened well using dual concentric drill pipe. A blind annulus injection sub and a development head are interconnected with the drill pipe and so constructed that compressed air passing down the inner pipe is directed through nozzles in the head to agitate formation water and clear the screen. When air is passed down the pipe annulus it is injected into the inner pipe and causes formation water and sand to be drawn into the head and airlifted to the surface through the inner pipe.

Abstract: An injection sub for use with a string of dual concentric drill pipe, having inner and outer tubular members concentrically arranged to mate with the inner and outer pipes of the drill string to provide continuous isolated annular and central passageways, is particularly characterized by an annular chamber in the inner member. Ports permit the flow of fluid from the annular passageway to the chamber, and apertures permit fluid flow from the chamber to the central passageway. An annular check valve in the chamber cooperates with the ports to prevent flow from the chamber to the annular passageway.