Abstract: A jet assisted drill system which uses a high pressure intensifier, positioned in a down hole drill assembly. Drill fluid from a drill stem is directed into the drill assembly, and in one mode this drill fluid is passed through the pressure intensifier to cause a piston assembly of the intensifier to reciprocate, with high pressure pistons of the piston assembly delivering high pressure drill fluid to a discharge jet in the drill bit assembly. The lower pressure fluid which drives the low pressure pistons is discharged into a downstream annular passageway and to the drill bit assembly. In a by-pass mode, a selector valve directs drill fluid from an upstream main passageway portion directly to a downstream main passageway portion to pass out the drill bit assembly. This flushes out debris which is carried upwardly out of the drill hole. There is a control valve to operate the piston assembly and a trigger valve operated by the piston assembly to direct fluids selectively to the control valve.

Abstract: A drill bit assembly comprising a plurality of cutter units, with each cutter unit comprising a circumferentially forward, relatively blunt positioning cutter, followed by a fixed cutter having a relatively sharp cutting edge, with the cutting edge of the following cutter being positioned a predetermined distance below an operating position of the positioning cutter. Thus, the cutting depth of the following cutter is controlled by the positioning cutter locating the drill bit assembly against the hole end wall from which material is being cut. Also, additional fixed cutters can be provided in circumferential alignment in said cutting units, and liquid jet cutters can be used in combination with said cutting units.

Abstract: A dual conduit drill string used in drilling holes for geothermal, oil and gas wells, and the like, comprises a removable inner conduit to permit the use of salvage or repair equipment within the outer conduit. The outer conduit comprises standard API drill pipe sections which are each slightly modified to receive the removable inner conduit sections. Each inner conduit section is provided with flexible hangers for suspending the weight of the inner conduit from a support ledge formed on the interior surface of the drill pipe. The hangers permit upward removal motion and rotation of the inner conduit with respect to the drill pipe, but prevent downward motion. Individual inner conduit sections are joined together at lockable stab joints in which locking is accomplished by the rotatable engagement of a key and locking socket. Preferably, the inner conduit is manufactured in uniform lengths and mounted in drill pipe sections of non-uniform lengths by means of drill pipe adaptor subs.

Abstract: A method and apparatus for drilling combines the advantages of a high pressure fluid jet with a mechanical drill bit without the high horsepower requirements and associated equipment wear of prior jet drilling systems. A two fluid system is contemplated in which only a small portion of the drilling mud stream is clarified and pumped under high pressure to a number of jet nozzles located on the drill bit face. The high pressure fluid and concentrated drilling mud are conducted separately down the hole by a dual, concentric drill pipe. The power and equipment requirements of such a two fluid system are practical and economic because of the low flow rate and non-abrasiveness of the high pressure fluid when compared to conventional drilling fluids. The high pressure fluid combines with the concentrated drilling mud at the drill bit in order to accomplish the normal purposes of the drilling mud. The returned fluid is processed at the surface separating out solids, mud, and the mud to be clarified.