One of the critical issues in the design of FPSOs for ultra deep waters is the design of the most costefficient station keeping system for the specified operational requirements. The capital cost of the stationkeeping system including its installation can increase dramatically with an increase in water depth. In addition, seafloor congestion, poor geotechnical conditions, or short field life may result in the traditional mooring system not being an optimum solution. Thus beyond certain water depths and for certain other conditions and applications, the technical and economical constraints associated with mooring systems may favor other concepts more attractive and cost-efficient, such as a fully dynamically positioned FPSO (DP FPSO). This concept combines state-of-the-art FPSO technology and latest generation drill ship technology for dynamic positioning and operation in ultra deep waters. This system can either be utilized as an early production system or as a full-fledged field development solution. The areas most suited for this application are the Gulf of Mexico, Brazil, West Africa and Eastern Canada.
An early comprehensive study of dynamic positioning of large ships in ultra deepwater was conducted for a large ocean mining vessel in 6,000 meters of water (Brink and Chung, 1981). The development of the DP FPSO builds from this and the experience obtained with the BP Seillian FPSO, and the latest generation of dynamically positioned drillships specifically designed for water depths up to 3,000 meters.
The BP Seillian operated in the North Sea for 8 years as a dynamically positioned production platform and was recently re-deployed in deep water offshore Brazil as an early production system for the Roncador field in 1,853 meter water depth. In Brazil the Seillian has remained on station while offloading to standard and DP shuttle tankers without incident (Henriques, 2000; and Gardner, 1999). The latest generation deepwater drillships have been in operation almost 5 years in many deepwater regions worldwide and are designed to remain on station in seastates up to the 10-Year hurricane environment in the Gulf of Mexico. In addition many thruster-assisted turret-moored FPSOs are in operation in the North Sea and have been studied for the Gulf of Mexico (Wichers and van Dijk, 1999).
发表于 2009-2-21 20:19
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