Study On FPSO Polyester Mooring Rope Tensile Properties And System Dynamic Response Analysis

Floating Production Storage and Offloading system(FPSO)units play an important role in the development and utilization of offshore oil and gas resources due to their strong mobility and resistance to wind and waves.FPSO moorings in deep waters often use polyester ropes,and the mooring capacity of polyester ropes is related to the nonlinear tensile properties of the ropes themselves,which are easily affected by temperature and load.Therefore,it is necessary to conduct an in-depth study on the tensile properties of polyester rope and the influence of tensile properties on the dynamic response of FPSO mooring system.In this thesis,the following studies are conducted on the polyester mooring system of FPSO:Study on the non-linear tensile properties of FPSO polyester mooring ropes which are susceptible to temperature and dynamic loads.A temperature-controlled polyester rope tensile test rig was built,and three temperature environments were selected: 20℃,30℃ and 40℃ to test the minimum breaking load and tensile properties of the polyester rope,revealing the relationship between temperature,average load,load amplitude and load cycle on the stress and strain of the polyester rope and the influence of hysteresis return line.Based on the LevenbergMarquardt optimization algorithm,a model for calculating the dynamic stiffness of polyester rope,which integrates temperature,humidity,average load,load amplitude and number of cycles,is proposed,and the accuracy and usability of the model is verified by the tensile test of polyester rope at 25℃.The dynamic response of the spread point mooring system of the FPSO polyester mooring rope under different oceanic environment conditions is investigated.The hydrodynamic frequency analysis of the FPSO under the water depth of 1500 m was carried out by AQWA data simulation software to obtain the relationship between the RAO coefficient,radiation damping coefficient and additional mass and wave frequency in six degrees of freedom of the FPSO.The dynamic response of the spread point mooring system of the FPSO polyester mooring rope under different marine environment conditions is analyzed by introducing the dynamic stiffness calculation model of the polyester rope using the time domain analysis software Orca Flex software.The results show that the dynamic stiffness mainly affects the mooring rope tension in the FPSO mooring system,and the tension of the mooring rope becomes larger as the dynamic stiffness decreases,which has less effect on the displacement and rotation angle of the FPSO.This thesis provides a theoretical basis for the design of FPSO mooring systems and their engineering applications by analyzing the tensile properties of FPSO polyester mooring ropes and the dynamic response of their systems,which provides an important reference for the longterm stable and safe operation of FPSO mooring systems.