Ultra-Deepwater Production System: Model Test Study of Cylindrical FPSO in GoM Hurricane Conditions

摘要

To address the challenges of Gulf of Mexico (GoM) Lower Tertiary exploitation, alternative FPSO conceptsrnare studied by the industry. This paper documents Phase 2 of a UDW RPSEA study which had as itsrnmain objective the validation of a production concept based on a permanently moored cylindrical FPSOrndesigned by Sevan Marine with steel catenary risers (SCR). The present work focuses on model testingrnof the cylindrical FPSO hull design, performed at the Offshore Technology Research Center (OTRC) atrnTexas A&M University in College Station, in May 2016. The experiments were performed at a scalernof 1:64. The model was subjected to the Central GoM Hurricane environmental conditions. The processrnof analysis includes extreme hurricane waves, wind, and currents, combined with ultra deep water, torndemonstrate the feasibility of the concept in the GoM. This combination implicates complex hydrodynamicrnbehavior of the hull, mooring and riser system. Thus, the model test provides better understanding ofrnthe new concept performance. Model test results, including motions and mooring loads, are comparedrnwith numerical predictions for a series of test cases. The importance of viscous effects on motions of therncylindrical unit and of the green water effect is discussed. Finally, to assess the feasibility of the hull andrnriser system, the numerical results of a hybrid approach, full scale, coupled riser analysis are presented, asrnbased on measured hull motions and environmental conditions. This is finally followed by a discussion ofrnthe implications of technical and regulatory aspects of the FPSO concept. Following the project criteria,rnthe present system based on SCR configuration seems feasible; however optimization of hull and mooringrnsystem is necessary to improve green water and viscous effects on hull motions in extreme current.