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 positioned below the mudline and within a normal pore pressure environment. The apparatus includes a pump 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. The fluid in the borehole is then pressurized by the pump to at least a borehole pressure equal to or greater than the pore pressure of an abnormal pore pressure environment. A pressure housing assembly allows for the drilling of a borehole below the conductor casing into an abnormal pore pressure environment while maintaining the pressurized fluid between a borehole pressure equal to or greater than the pore pressure of the abnormal pore pressure environment, and below the fracture pressure of the borehole in the abnormal pore pressure environment. Advantageously, a method is provided for drilling a borehole into the subsea abnormal pore pressure environment.