The Hydrodynamic And Mooring System Analysis Of Semisubmersible Platform

Offshore oil exploitation and drilling is inseparable from the ocean platform. Ocean platform with high performance could provide security and stability work environment for offshore oil exploitation and drilling. Semi-submersible offshore platform is much used for offshore production. It is very necessity to research on hydrodynamic performance and the mooring design of Semi-submersible offshore platform.In this paper, the main work is as follows:Based on the three dimensional potential flow theory, the paper solve the hydrodynamic coefficients and motion response of the semi-submersible platform. On the one hand, It could evaluate its hydrodynamic performance; On the other hand, it could provide database for the design of mooring system. The paper also consideration the effect of hydrodynamic interaction between the platform and a barge.The paper choose the material parameters of mooring cable according to the steady force in a given environment and choose mooring cable’s length and pretension according to the catenary equation and slackness equation. The paper come up with a flow chart to correct those parameters. After these, we decide the arrangement of mooring cable with a sensitivity analysis.The paper does a research on the couping analysis of the platform and mooring cables. It calculate the maximal displacement of the platform and maximum tension of mooring cable under the depth of 270 m and 1500 m with three coupling method. When the water depth is larger, we much use the dynamic coupling method; When the water depth is small but the displacement of the platform is large, we choose quasi-static method; When the water depth and the displacement of the platform are small, we could use the static stiffness method.The paper uses the dynamic coupling method to calculate analyze the mooring system which have been designed. It finds that the platform’s sway, surge and yaw have low frequency effect and platform’s roll, pitch, heave have wave frequency effect. The paper also cheeks the mooring cables under the condition of intact and damaged status and finds that the strength of the mooring cables meets API code.