FPSO Solutions for 10,000-ft GOM Field Development

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 17200, "DeepStar - FPSO Solutions for 10,000-ft GOM Field Development," by J.E. Chitwood, Chitwood Engineers, and S. Hanrahan and G. Adhia, Chevron, prepared for the 2005 Offshore Technology Conference, Houston, 2-5 May. Copyright 2005 Offshore Technology Conference. Reproduced by permission. DeepStar has evaluated new and emerging technologies for developing small standalone (marginal) fields in 10,000 ft of water in the U.S. Gulf of Mexico (GOM). These studies identified viable field-development scenarios that improve field economics. Further, the studies identified knowledge gaps requiring further investment before these development systems are ready for field application. This paper describes the evaluation process and uses floating production, storage, and offloading (FPSO) vessel development alternatives to illustrate the identification of specific knowledge gaps for FPSOs in 10,000-ft water depths. Introduction Deepwater fields like Thunderhorse are being developed in water depths approaching 6,000 ft in the GOM, and discoveries have been made in water depths to 10,000 ft, with many intermediate-water-depth discoveries. A life-cycle economic model was prepared for alternatives considered viable by the technical committee. Where technology was extended or new technology assumed available, an estimated commercial cost was used. The realistic input yielded a mature concept comparison in which the field-development alternatives were compared on an equivalent basis. The most promising development scenarios could then be identified. Evaluation criteria included the following. - Projected economic performance. - Schedule through project qualification. - Cost of the necessary technologies through project qualification. Four surface-facility scenarios were studied. - Semisubmersible—provides lowest motion solution. - Spar—features low motion and dry trees. - Tension-leg platform—requires new ten-don technologies for 10,000-ft water depths. - FPSOs—use a gas-export pipeline and an oil shuttle tanker. When extending these surface facilities to 10,000 ft, the following critical aspects must be understood fully. - Station-keeping method. - Riser system. - Surface facility. - How all these items interrelate and operate as an integrated unit through all phases of operation (i.e., design, construction, installation, normal production, storm conditions). This understanding must be further communicated to the regulatory and classification agencies to obtain approvals. FPSO arrangements included the following. - Permanently moored weathervaning FPSOs. - Dynamically positioned (DP) FPSOs.