| With the marine oil and gas exploration and development gradually diverting to deepwater,the subsea Christmas tree,whose installation difficulty and risk are greatly improved,is taken as the critical equipment of subsea production system.As a relatively independent operation process of the subsea Christmas tree installation,tubing hanger installation is subject to hostile ocean environment,limitation of equipment and technique,and other factors.The risk assessment research of tubing hanger installation can not only ensure the continuity and safety of tubing hanger installation and reduce the installation cost,but also provide decision support for the safety operations and measures of tubing hanger installation.This thesis has carried out the risk assessment research of tubing hanger installation,and the main research work is as follows.(1)Based on the investigation and summarization of domestic and foreign relevant information of tubing hanger installation,a set of the tubing hanger installation process,which is suitable for the horizontal subsea Christmas tree(working depth 1500m),is established.An overall and systematic identification of risk is carried out,and the list of risk factors associated with tubing hanger installation is established with the combination of casual analysis and failure mode and effect analysis.(2)Contraposing the problem of polymorphism,uncertainty and difficulty of obtaining the probability of occurrence accurately existing in the risk factors of tubing hanger installation,the T-S fuzzy fault tree model is set up and the importance analysis is conducted with the combination of fuzzy set theory and expert judgement,and then the criticality importance of each risk-inducing event is determined.(3)Contraposing the problem of no backward inference and difficulty of updating evidences existing in the T-S fuzzy FTA,the T-S fuzzy fault tree model is mapped into the Bayesian network model of tubing hanger installation,and the forward and backward inference and sensitivity analysis are performed,and then the maximum possible cause chain and the sensitivity level of each risk-inducing event are determined.(4)Contraposing the problem of inability to obtain an overall risk assessment decision through the single dimensional risk measurement,the D-S evidential multidimensional risk assessment decision model is established based on the severity,critical importance and sensitivity of each basic event.An improved method of D-S evidence theory is proposed to deal with the highly conflict evidences,and the risk assessment decision analysis is conducted according to the belief function obtained by evidence fusion.Then the main risk factors of tubing hanger installation are determined,and the targeted risk control measures are put forward. |
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