The Mooring System Analysis Of Deepwater Semisubmersible

Ocean contains abundant rich resources, where oil & gas production has been explored for decades. For instance, Mexico of Gulf, West Bay, Brazil Sea, China's Bohai Sea, East China Sea and South China Sea are regarded as significant production fields in academic researches and practical operations. Nowadays, the exploration and production of oil & gas intend to deeper sea with 1000～3000 m depths in Mexico Gulf, Brazil, West Africa, North Atlantic and Norwegian Sea. Today, deep sea platforms for drilling and production are just getting started. We are facing the fierce competition to explore deep sea resources, which belongs to the human beings. It forces us to pay more attention to the technology and researches of deep sea platforms.Now, semisubmersible is an advanced operating platform which suits for the deeper water. It not only can overcome the instability of the drilling vessels, but also can operate in the deeper water. It is necessary to design the mooring system for this marine development and transport tool.In order to guarantee semi-submersible can be work under the normal operate in the majority of sea conditions and the safety in the adverse sea conditions. It is particularly important to analyse the hydrodynamic and motion performance of semi-submersible in the action of the wind, wave and current and reasonable design the mooring system of the semi-submersibleIn this thesis, SESAM software is used , which based on three-dimensional potential theory and Morison formula. The added mass coefficients and damping coefficients of semisubmersible induced by the regular wave are calculated by SESAM software. The forces and motions of the semi-submersible induced by wave are calculated in the regular wave, and analyse the mooring system, which have 8 and 12 cables to position also studied. The numerical analysis of environmental loads and motions in accordance with API rules, and the wave drift forces are calculated using spectral analysis method. And then, Mimosa software, which based on static analysis and dynamic analysis to analyse two plans of the mooring system. Finally, the results of the two plans are compared and give the reasonable conclusions.