Design of embedded chain inverse catenary of deepwater FPSO mooring suction pile

FPSO is the main development model of deepwater oil field in South China Sea, and it has high requirements for the reliability of single-point mooring system. Therefore, the design investigation of inverse catenary of deepwater FPSO mooring suction pile was conducted. Meanwhile, a complete mathematical model for inverse catenary of suction pile was established based on the characteristics and mechanics of seabed soil, and a calculation method for the slack of inverse catenary was proposed. Besides, taking a deepwater FPSO project in the South China Sea as the research object, analysis on mooring under the designed survival condition (1 000-yr-RP) and the designed extreme condition (100-yr-RP) was performed based on the mooring load conditions required by classification societies to obtain the seabed mooring load. As shown by the evaluation results on design of embedded chain inverse catenary and its slack, the tension range of the embedded chain inverse catenary for suction pile of this FPSO mooring is 10 254 kN to14 075 kN, the load angle range is 16.2° to 30.1°, and the horizontal projection distance of the embedded chain is 47.33 m to 80.30 m. Further, the results based on different rules are close to each other for mutual verification. The final results of analysis and design could provide experience for similar FPSO projects.