Full-scale Measurement And Analysis Of FPSO Soft Yoke Single Point Mooring System

As one of important ocean engineering equipments, FPSO is the core unit to develop whole offshore model and has been widely applied in offshore oil and gas development all over the world. Mooring system is the key facility to determine mooring position of FPSO. In China’s Bohai Bay, soft yoke single point mooring system is widely used to moor FPSO. Soft yoke single point mooring system is mainly designed by the combination of theoretical numerical analysis and pool model experiment. However, due to the immaturity of the design theory, the complexity of environmental load and structure motion, soft yoke single point mooring system accidents happened many times in recent years. With the increasing energy demand and raising awareness of ocean engineering structure safety, it is in urgent need to find a new way to study soft yoke mooring structure motion so as to guarantee the safety of mooring structure.With regard to the problems in soft yoke single point system design and analysis and the soft yoke mooring structure failure accidents in recent years, this study takes a full-scale measurement of soft yoke mooring system and makes an analysis and assessment. By taking prototype measurements of soft yoke single point mooring system of FPSO in shallow water oil field in Bohai Bay, long-term real-time attitude angles and stress information of mooring legs and yoke are obtained. This approach develops the soft yoke mooring force computing analysis method based multi-body dynamics. The result is in consistent with the mooring force measured by strain responses computing method, and shows a higher accuracy than traditional static method. The combination of dynamic method with measured results improves and enriches monitoring information evaluation technology and early-warning technology of soft yoke single-point mooring system in shallow water and further guarantees the safety of the FPSO. Additionally, this paper analyzes and studies special structure motion in full-scale measurement such as resonance. It is the first time that full-scale measurement of FPSO in shallow water soft yoke mooring structure has been conducted at home. This has great significance in practical engineering.