Shell International Exploration and Production B.V. Research & Development has developed an automated choke manifold capable of maintaining a relatively constant bottomhole pressure while drilling. The Dynamic Annular Pressure Control System prototype was successfully tested in 2003, followed by a long-term trial on a deep geothermal well in 2004, proving the robust nature of the design. Two new systems have now been prepared for offshore use. One choke system has been deployed for use in the UK sector of the North Sea and a hybrid system deployed in the Gulf of Mexico. Both applications require the bottomhole pressure to be maintained at a relatively constant value in order to maintain borehole stability. Both applications are in mature offshore oilfields where narrow pressure margins would result in borehole collapse if conventional drilling methods were employed. The development of the choke manifold systems, application and results will be discussed.

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