基于蒙特卡洛方法的油气井管柱可靠性评估*

为提高油气井管柱服役的安全性，采用数据统计与可靠性理论评估油气井管柱可靠性。首先，识别影响管柱外载及其参数的变量，构建油气井管柱安全极限状态方程；然后，采集模型变量数据，确定变量分布与参数，形成油气井管柱可靠性数值模型；最后，通过蒙特卡洛方法计算影响管柱可靠性的关键变量和不同置信度水平下管柱剩余强度分布及安全系数取值。结果表明:目标区域油气井管柱剩余强度符合正态分布，得到不同置信度水平下管柱的可靠度，管柱的安全系数取值范围可满足管柱安全设计要求，所构建的方法可为实际生产中油气井井筒管柱安全评价提供技术支撑。

Reliability assessment of oil and gas well string based on Monte Carlo method

To improve the operational safety of oil and gas well string,the data statistics and reliability theory were used to assess the reliability of oil and gas well string.Firstly,the variables affecting the external applied load of string and its parameters were identified,and a limit state equation of oil and gas well string safety was built.Secondly,the variables data of model were collected,and the variables distribution and parameters were determined,and a numerical model for the reliability of oil and gas well string was established.Finally,the Monte Carlo method was adopted to calculate the key variables affecting the string reliability,as well as the residual strength distribution of string under different confidence levels and the values of safety factor.The results showed that the residual strength of oil and gas well string in the target area followed the normal distribution,and the string reliability under different confidence levels were obtained.The valuing range of safety factor of the string could meet the requirement of safety design.Overall,the constructed method can provide technical support for the safety evaluation of oil and gas well string in the actual production.