Study On Dynamic Damage And Anchor Failure Of Semi-submersible Platform Mooring System In South China Sea

The oil and gas resource in South China Sea is rich,and oil and gas exploitation depth increases gradually in recent years,with the development of mining technology.The nation’s ocean strategy stimulates the demand for deepwater equipment such as deepwater semisubmersible platforms and so on.Relative to the dynamic positioning system,within a certain depth range of water,the anchor positioning system has obvious advantages,Especially in conditions of a longer drill(finished)period,bad weather and sea conditions,The use of mooring system positioning will significantly reduce costs.Therefore,mooring positioning plays an irreplaceable role in the deep water oil and gas development.So,the study on dynamic damage and anchor failure of semi-submersible platform mooring system is particularly important.This thesis takes a deepwater semi-submersible platform in South China Sea for example,uses the environment data in Liuhua field,based on this,have a study to dynamic damage of the mooring system under extreme condition.The dynamic response analysis is based on the three-dimensional potential flow theory and Morrison equation.Creating coupling analysis model of mooring system of semi-submersible platform by finite element software ANSYS,then computing platform mooring system response through the AQWA module of the dynamic,frequency analysis using AQWA-LINE module.Getting the dynamic response of the transfer function of each degree of freedom platform and the dynamic characteristics of the foundation parameters of semi-submersible platform.On the basis of this,the drift of the platform under the limit condition and the maximum dynamic tension of the anchor cable are obtained.Carry out further research on the the overall and local strength analysis of the platform mooring system,to find weak points of chain,getting the mooring system of semi-submersible platform strength failure criterion.Study on anchor walking mechanism of semi-submersible platform mooring system.Calculating holding capacity of anchor by using the empirical method of US Naval Civil Engineering Laboratory to research the ultimate holding capacity of anchor in sand,so as to obtain the anchor mechanism of the mooring system of semi submersible platform.In order to improve the time effectiveness of mooring system,a new method is proposed to optimize the distribution ratio of semi submersible drilling platform.Researching the accident types of platform and ship mooring system due to the failure of the mooring system at home and abroad.Identifying the mooring system comprehensive risk according to the types of accidents that may occur from the environment,personnel,equipment,management,design,accident and mooring system operation process.According to the different risk factors identified above,the risk control strategy analysis is carried out,and the emergency procedures of the anchor system are given to form the risk control technology of the deepwater semi-submersible platform mooring system.Finally,a model of semi-submersible platform mooring automatic control system is proposed,which reduces the risk of platform anchoring.