Patent ID: 6892829

Claim:
A method for drilling a well bore in a hydrocarbon formation, comprising: providing a concentric drill string having an inner pipe, said inner pipe having an inside wall and an outside wall and situated within an outer pipe having an inside wall and an outside wall, said outside wall of said inner pipe and said inside wall of said outer pipe defining an annulus between the pipes; forming a borehole in said hydrocarbon formation with a drilling means connected at the lower end of the concentric drill string; delivering drilling medium through one of said annulus or inner pipe to the drilling means for entraining drill cuttings in said borehole; extracting said drilling medium and entrained drill cuttings through said other of said annulus or inner pipe; and providing a downhole flow control means positioned at or near the drilling means for preventing flow of hydrocarbons from the inner pipe or the annulus or both to the surface of the well bore.