Risk Assessment For Deepwater Platform Steel Catenary Riser Using Analytic Hierarchy Process

As the steel catenary riser has excellent submerged dynamic performance and low cost, it has become the preferred riser form in engineering of deepwater oil and gas energy. But owing to the highly complex environmental factors and shortage of experience of the riser design, construction and management, the steel catenary riser has been the most critical parts of deepwater infrastructure. As a result of the uncertainty of failure factors and the lack of accident data, the conflicts between deepwater energy development and SCR security have become increasingly prominent, so it is urgent to study the SCR risk assessment. Based on such background, the hierarchy structure of deepwater SCR risk factors has been constructed and the main risk factors of the SCR could be obtained; the improved fuzzy fault tree method has been used to calculate the failure probability of the deepwater SCR; the comprehensive failure consequences rating can be gained with the improved expert comprehensive evaluation analysis; the deepwater SCR risk has been quantificationally evaluated with the method of risk matrix. The main contents are shown as follow:First of all, based on improved analytic hierarchy process, identification model of deepwater SCR operating risk factor has been established. According to the data of riser prototype monitoring, site detection and periodic inspection, failure modes of SCR have been studied and the hierarchy structure of risk factors has been constructed. The weights of risk factors can be gained with the methods of particle swarm optimization algorithm. Then the main factors that influence the deepwater SCR operating safety could be obtained.Next, improved fuzzy fault tree method which is based on analytic hierarchy process has been applied to calculate the failure probability of the deepwater SCR due to the high lack of deepwater SCR data. Based on the fault tree of steel catenary riser operating risk factors, the failure probability of deepwater riser could be obtained with the method of fuzzy mathematics theory and analytic hierarchy process.Then, based on improved expert comprehensive evaluation analysis, the hierarchy structure of the deepwater SCR failure consequences has been constructed. The comprehensive failure consequences rating of the oil loss, pollution of the environment and casualties can be gained with the method of expert comprehensive evaluation analysis and analytic hierarchy process. Lastly, deepwater SCR risk has been quantificationally evaluated with the method of risk matrix. Based on the influence of risk probabilities and consequences, the quantitative risk assessment of deepwater SCR could be realized. The assessment result indicates that the failure of the deepwater steel catenary riser will lead to high risk and thus effective measures should be taken to decrease the probability of the risk occurrence.