| With the development of offshore oil and gas exploration and development being applied to ultra-deepwater,the quantity of the Christmas tree in subsea production systems has rapidly increased,and has become one of the mainstream modes of oil and gas exploitation.The Christmas tree in marine environment are experiencing complicated loads in term of environment and working,which leads to high failure probability.The repair or replacement of Christmas tree failure not only affects the normal delivery of oil and gas,but also leads to marine environment pollution or even ecological disaster.Therefore,the research on the reliability of the subsea Christmas tree system has become an important part of ensuring the safe operation of the whole oil and gas exploitation.In this paper,the risk reliability evaluation of the subsea Christmas tree system is studied.First,the structure unit and structure characteristics of the subsea X-mas tree system are described in detail,and the mechanism of failure mechanism of the system is analyzed,then the statistics of the subsea X-mas tree system in process components of failure data,according to the statistical results and the relevant reliability theory knowledge,the influencing factors of the reliability of the subsea X-mas tree system are clarified.Secondly,considering the lack of statistical data of the X-mas tree failure system,the fuzzy fault tree is applied to analyze the reliability of the X-mas tree system,and the fuzzy probability importance degree is analyzed for the X-mas tree production system.The calculation results show that failures such as leakage,corrosion,blockage,seal failure,and failure to work properly(such as failure to open/close properly and fail to lock/unlock)are weaknesses in the Christmas tree system;By studying the failure mechanism and establishing the Markov model of the Christmas tree system,and the reliability of the Christmas tree system is quantitatively analyzed.The calculation results show that the steady state availability of the Christmas tree system is 0.999671,and the influence of each state transition probability on the steady-state availability of the system is also studied.Furthermore,Based on Bayesian network modeling method,taking full account of the polymorphism,fuzziness and dynamics of faults between systems and components,the fuzzy set theory is introduced into Bayesian network analysis,reliability modeling and analysis of the reliability of the Christmas tree system.An example of a subsystem fault of the Christmas tree is calculated and compared with the fault tree analysis method,which proves the accuracy of the method.Finally,the parametric model of the tubing hanger is established using the APDL design language,The relevant parameters of the tubing hanger are regarded as random variables,and using Monte Carlo method to reliability analysis of tubing hanger,With a 95% confidence level,the tubing hanger suspension reliability is 96.23%.The most critical factors affecting the reliability of the tubing hanger by the parameter sensitivity analysis are the total length and the internal pressure.Based on the above analysis results,the feasibility of the method is verified,and the theoretical guidance for the structural design of key parts such as tubing hangers in the Christmas tree system is provided. |
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