套管抗挤强度分析及计算

为提高套管挤毁压力预测精度，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，研究了外径不圆度、壁厚不均度、残余应力等因素对套管抗挤强度的影响。分析结果表明，径厚比、屈服强度是套管抗挤强度的主要因素，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位置组合进行了模拟分析。结果表明，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。最后提出了一个套管抗挤强度计算公式，计算简单，精度可满足工程要求。

CASING COLLAPSE RESISTANCE ANALYSIS AND CALCULATION

To improve the precision of casing collapse pressure calculation,the variance analysis of the full scale collapse test data of 213 casings is conducted with statistical method.The effects of outer diameter/wall thickness,material yield strength,ovality,eccentricity and residual stress on the casing collapse resistance are analyzed in this paper.The results show the ratio of diameter and thickness and yield strength are the main parameters of influencing the collapse pressure of casing,and the decreasing of the casing collapse resistance is 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 is performed.From the simulation results,it is concluded that the casing collapse pressures differs greatly between different combinations.In the end,a new casing collapse calculating formula is put forward which gives the more accurate prediction of casing collapse,the accuracy can meet the requirement of application.