Method of forming a subsea borehole from a drilling vessel in a body of water of known depth

摘要

Apparatus and a method are described for drilling with casing in a borehole in a typically unconsolidated formation, wherein the method involves isolating the annulus between the casing and the borehole section from fluid circulation and creating a hydrostatic pressure in the annulus which is adapted to balance any over-pressurized water in the formation.