基于马尔可夫方法的水下防喷器可靠性研究

水下防喷器是保障海上钻井安全的关键设备,对其可靠性进行定量评价对井控作业有重要的指导意义.为了弥补现有水下防喷器可靠性评价方法的不足,将水下防喷器的工作状态分为四种,包括无故障可用、关井、井控关键失效及关井时失效.利用Markov方法建立了水下防喷器的Markov模型.通过水下防喷器系统的状态转换图找出了各工作状态的转换关系.通过分析墨西哥湾83口深水井水下防喷器的失效数据,定义了影响水下防喷器可靠性的井控关键失效,并对深水钻井水下防喷器防喷功能的可靠性进行了定量计算.将计算结果与不考虑关井期间的井控关键失效相比较发现,防喷器的防喷失效概率增加了65％.因此传统的定量评价方法可能会得出相对乐观的结论,应在实际生产中给予重视.

Research on reliability of subsea blowout preventer based on Markov method

Subsea blowout preventer（BOP） is the crucial equipment to ensure offshore drilling safety.Quantitative assessment for its reliability is very meaningful to instruct field well control practice.To cover the limitations of existing reliability assessment methods for subsea BOP system,working states of subsea BOP system were divided into four,which included available with no failure,closed with no failure,failed with no demand,and failed when demanded.Markov model of subsea BOP was built based on Markov method.Markov transition program was presented to find out the transition relationships of the four working states.After analyzing failure statistics of subsea drilling BOP systems installed on 83 deepwater wells in Gulf of Mexico,the definition of well control critical failure for subsea BOP system was defined.Based on the statistics of well control critical failures,reliability of deepwater drilling BOP to prevent blowout was assessed quantitatively.Compared to the result which ignores failures after BOP closed,blowout prevention failure occurrence of subsea BOP system increased by 65 percent.Therefore,traditional quantitative reliability assessment methods may get relatively optimistic conclusions in subsea BOP reliability assessment.Well control critical failure happened during shut-in should not be ignored in field well control practice.