Study On The Mooring System Of FPSO In Deepwater

South China Sea is the largest,deepest sea in China,whose oil and gas resource is very rich.The oil resource of whole South China Sea basin group is approximately between 230and300 million tons,the gas resources is approximately 16 trillion cubic meters.These oil and gas resources account fora third of the total amount,of which seventy percent lie in the deep sea area of 1537000 square kilometers.Compared with other floating platform,FPSO is deemed to have more competitive advantages.China currently has nearly 20 ships of FPSO served in every big shallow water oil field,each of which had accumulated a wealth of experience in the operation and management,.And all of this laid a solid foundation for deep-water development of our country.Most of FPSOs in our country are served in water depth less than 300 meters.Compared with shallow water FPSO,the design of deep water FPSO has more challenges,especially for the key technology of single point mooring system in deep water.Assumed for security reason.In order to break the long-term foreign company’s technology monopoly about the single point mooring system,it is urgent to research the relevant technology to design the mooring system with independent intellectual property rights applied to the South China Sea.In this paper,it summarized the common mooring of FPSOs through researching the domestic and international FPSOs.What’s more,it has completed the following works,such as type selection,strength analysis and the fatigue assessment based on the related theory.According to the design basis and design conditions,considering the limiting conditions in different parts of the mooring line,it determined the composition and arrangement of mooring lines based on the economic and technical feasibility and other aspects.Ultimately the mooring lines arranged as 3*3,each mooring lines are used in the composition of the "steel chain,wire rope,steel chain",the mooring radiuses of system was 1452 meters.Based on the environment conditions once in hundred years and reference to the relevant norms,it analyzed the maximum tensions of mooring lines 、 the maximum drift distance of FPSOs in different conditions And checked the strength of the mooring lines.The results show that the design meets the requirements of the specification.According to the calculation results obtained the following conclusions: firstly,the performance of mooring system in full loaded is the important indicator of design,what’s more,the most influential factors are wave height and wave velocity.Secondly,the influence is by the coupling of wave and flow,the flow velocity has a great effect on the system.Thirdly,collinear environmental conditions need be focused on in the design process.Fourthly,3 * 3 mooring arrangement can effectively guarantee the floating body’s safety in the condition of a cable breaking.Finally,it calibrated the fatigue strength of mooring lines using rain flow method.The results show that the design meets the fatigue life requirements.