外压作用下套管抗挤强度研究

Casing Collapse Analysis under External Pressure

为提高套管挤毁压力的计算精度,应用统计方法对213根套管全尺寸挤毁试验数据进行了方差分析。结果表明,径厚比、屈服强度是套管抗挤强度的主要影响因素,不圆度、壁厚不均度、残余应力等因素对套管抗挤强度的影响呈随机性分布。利用有限元方法对外径不圆度、壁厚不均度和残余应力的不同组合进行模拟分析得出,数值相同的外径不圆度、壁厚不均度及平均残余应力组合不同时,套管的挤毁压力相差很大。提出了新的套管挤毁压力计算公式,计算表明精度可满足工程要求。

To improve the precision of casing collapse pressure calculation, the analysis of variance of the full scale collapse test data of 213 pieces of casings was conducted with statistical method. The effects of the ratio of outer diameter/wall thickness, material yield strength, ovality, eccen- tricity and residual stress to the casing collapse resistant were analyzed in this paper. The results showed the ratio and yield strength were the main parameters of predicting the collapse pressure of casing and the decreasing of the casing collapse resistant was a random process with the increasing of ovality, eccentricity and residual stress. And the casing simulation analysis of various combinations of the location of ovality, eccentricity and residual stress under external pressure was performed. From the simulation results, it was concluded that the casing collapse pressures differ much between different combinations. In the end a new casing collapse predicting formula was put forward which give the more accurately prediction of casing collapse.