METHOD AND APPARATUS FOR DRILLING A BOREHOLE INTO A SUBSEA ABNORMAL PORE PRESSURE ENVIRONMENT

摘要

An apparatus for controlling a subsea borehole fluid pressure is proposed for use with a conductor casing (110) positioned below the mudline (57) and within a normal pore pressure environment. The apparatus includes a pump (53) for moving a fluid through a tubular into a borehole. The fluid, before being pumped, exerts a pressure less than the pore pressure of an abnormal pore pressure environment (10). The fluid in the borehole is then pressurized by the pump (53) to at least a borehole pressure equal to or greater than the pore pressure of an abnormal pore pressure environment (10). A pressure housing assembly (15) allows for the drilling of a borehole below the conductor casing (110) into an abnormal pore pressure environment (53) while maintaining the pressurized fluid between a borehole pressure equal to or greater than the pore pressure of the abnormal pore pressure environment (10), and below the fracture pressure of the abnormal pore pressure environment (10).