Patent ID: 7134514
Filing Date: 2006-11-14
Classification: E21B

Abstract:
1. A dual wall drill string assembly which allows dual circulation for directional drilling, said assembly comprising: (A) a metallic outer tube having: (B) a flexible, substantially non-metallic inner tube that is substantially enclosed within and generally coaxially aligned with the outer tube, said inner tube having: wherein the inner tube and the outer tube define an annular channel there between, wherein the non-metallic inner tube is formed of a material which allows it to bend to an arcuate path of a borehole for drilling a deviated wellbore without limiting bending of the metallic outer tube; (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.