Extreme Offshore Environment Jinzhou JZ20-2 Platform Risk Assessment

The in-service reliability analysis and safety evaluation (risk assessment) of offshore platform structures are very important to ensuring the safety in exploitation of ocean resources, for the structures have severe environment field and serious failure consequence. In this dissertation, as an example of Jinzhou JZ20-2 offshore platform, the system reliability analysis and safety evaluation (risk assessment) are monographic studied.Fistly, the research condition of reliability analysis of offshore structures was introduced briefly, and then the reliability analysis and safety assessment (risk assessment) of offshore platform structural components and system are provid based on it.Secondly, the extreme joint probabilistic distribution of wind speed and wave height in Bohai bay Jinzhou JZ20-2 oil field is obtained by employing the multivariable extreme value analysis theory method and uncertainty and sensitivity analysis techniques. And then the probabilistic distribution of structural response to wind and wave is obtained for analysis of structural reliability.Thirdly, calculational method of reliability analysis of offshore platform structural components was developed by adopting the calculational model of wind, wave, current and ice in the API specification (API RP 2A-LRFD), and by uncertainty and sensitivity analysis techniques. Considering of the deviation distribution of the offshore environment, equivalent normal method was introduced into the reliability analysis of offshore platform structural components, moreover the reliability analysis of Jinzhou JZ20-2 offshore platform structural components was calculated, therefore, the result of risk assessment of the platform structural components was obtainted.Fourthly, based on the ready-made special structural analysis program for offshore platforms, premised using the structural base shear force (BSF) or base Overturn Moment (OTM) to express the function of structural system function, three structural system reliability analysis methods, Sampling Statistic Method, Equivalent Load Method and Total Probability Method, are put forward according to the characteristics of offshore platform structures and their environmental action. And then, the system reliabilities of Jinzhou JZ20-2 platform structure are analyzed. The effects of resistance randomness and load dependence on the system reliability were compared.Finally, according to the results of the analysis and calculation, the methods of reliabilities analysis and evaluation (risk assessment) of offshore platform structural components and system were developed, and some relevant problems and suggestions in this field need to be further studied were put forward.