套管抗挤强度统计分析研究

针对美国石油协会的套管抗挤强度计算公式与实测套管挤毁压力差距较大的问题,利用统计学方法,详细分析了套管实物挤毁试验检测数据,得到了各因素影响套管抗挤强度的定量指标.研究表明,套管抗挤强度主要由径厚比决定;套管计算屈服外压和失稳外压等其他参数及其交互作用对套管的抗挤强度也有显著影响;套管外径和壁厚数据的变异系数比外径不圆度和壁厚不均度对套管抗挤强度的影响更显著.最后给出了套管抗挤强度统计计算公式,为生产厂和用户提供了预测套管抗挤强度的简单实用的计算方法.

Statistic analysis and calculation of casing collapse strength

There is the difference between the calculated data of the casing collapse strength by API formula and the factually measured data.In accordance with the problem,the data of the collapsing tests of actual casing are analyzed,and the parameters of influencing the casing collapse strength are determined by means of statistical method.The analysis of the test data shows that,the ratio of casing outer diameter to wall thickness is the decisive factor of the casing collapse strength;yielding external pressure and destabilizing external pressure and their interaction have remarkable influence on the casing collapse strength;outer diameter variation coefficient and wall thickness variation coefficient have more remarkable influences on it than outer diameter unroundness and wall thickness irregularity separately.Finally,a practical formula for calculating the casing collapse strength is presented,which provides a simple and practical method for predicting the casing collapse strength for casing manufacturers and users.