Abstract: Aiming at the problem of equivocal correction coefficient formulas of casing strength quoted in the American Petroleum Institute(API),the regularities and distribution of parameters for casing properties of API were discussed.The regularities of casing strength distribution were obtained by means of Latin Hypercube stochastic simulation method based on Monte-Carlo method.The influences of the randomness of geometric dimensions and mechanical properties of casing on the randomness of casing strength were achieved.The reliability model of casing strength was established by the use of reliability theory.The casing strength values under different reliability and the reliability of casing strength value in API formula were calculated.The research results indicate that the greater the random of casing properties is,the lower the reliability of casing strength value in API formula will be.The correction coefficient of elastic collapse strength of casing in the API formula is reasonable in terms of reliability.However,the API internal yield pressure formula of casing appled the correction coefficient is much safer.

Key words: casing strength, calculation formula, Monte -Carlo method, reliability theory, correction coefficient

摘要： 针对美国石油学会(API)制定的套管强度计算公式中引用的若干个修正系数理论意义不明确的问题,讨论了API套管多个属性参量的分布规律和分布参数.采用基于Monte-Carlo方法的Latin Hypercube随机模拟方法,模拟得出了套管强度的分布规律以及套管几何尺寸和管材力学性能的随机性对套管强度随机性的影响规律.运用可靠性理论建立了套管强度的可靠度计算模型,分析并对比了不同可靠度下的套管强度值,计算得出了API套管强度值的可靠度.研究结果表明,套管属性的随机性越大,套管强度的可靠性越低,API套管弹性挤毁抗挤强度公式的修正系数能够合理地提高其强度可靠性,但应用修正系数后的抗内压强度公式是偏于安全的.

关键词: 套管强度, 计算公式, Monte-Carlo方法, 可靠性理论, 修正参数