Full-scale measurement investigation of the hydrodynamics of a turret-moored FPSO in a typhoon and deduction of its mooring loads

Abstract

As a type of offshore structure, an FPSO unit is typically permanently moored to a designated position. These structures experience very complex sea states during which the motion response of the FPSO is enhanced, resulting in extreme loads on the mooring system. Full-scale measurement of the motion characteristics of an FPSO unit was carried out by the Shanghai Jiaotong University and the China National Offshore Oil Corporation from 2007 to 2009, lasting 25 months (Hu Z. 2010. Report for the full-scale measurement on the motion response of FENJIN FPSO in South China Sea and investigations on the deduction of the mooring line loads. Shanghai: State Key Lab of Ocean Engineering, Shanghai Jiao Tong University). We analysed the FPSO unit's motion responses during the passage of the typhoon ‘Koppu’ and its hydrodynamic performance. The loads acting on the mooring system were deduced through a decoupled analysis with the measurement data as input. The ability of the mooring system to hold station and the performance of the vessel in actual sea states are also presented to contribute important input to the future designs of FPSO systems.