Underbalanced marine drilling riser

摘要

A riser assembly for offshore drilling has an inner conduit suspended within an outer riser. A seal assembly seals an annular space between the inner conduit and the riser at the lower end of the inner conduit. The seal assembly has a pressure area that is independent of the inner conduit, so that any forces acting on the assembly due to pressure in the annulus below the seal assembly pass through the assembly to the riser and not to the inner conduit.