Patent ID: 7152700

Claim:
A dual wall coil tubing drill string assembly for subsurface drilling which allows dual circulation, said assembly comprising (A) a metallic outer tube formed as a continuously-milled tubular product manufactured in lengths which require spooling onto a take-up reel during the primary milling or manufacturing process, the outer tube having: (1) an outer tube first end; (2) an outer tube second end opposite the outer tube first end; (B) a flexible, substantially non-metallic inner tube that is formed of an elastomeric material which differs from the material of the metallic outer tube and that is substantially enclosed within and generally coaxially aligned with the outer tube, said inner tube having: (1) an inner tube first end, (2) an inner tube second end opposite the inner tube first end which defines a tube length therebetween, (3) an inner tube inner diameter which is generally constant along the tube length from the inner tube first end to the inner tube second end, wherein the inner tube and the outer tube define an annular channel therebetween, (C) a means for conveying fluid through the annular channel toward the inner tube first end, wherein the annular channel is adapted to convey drilling fluid under pressure toward the inner tube first end, and the inner tube is adapted to convey cuttings toward the inner tube second end; and wherein the inner tube includes at least one conductive element for conveying a signal and/or electricity, the conductive element being substantially embedded and enclosed within the flexible, non-metallic elastomer material of the inner tube.