弯曲井眼中套管抗挤强度计算

目前弯曲井眼中套管抗挤强度计算时没有考虑井眼弯曲的影响,无法确保固完井作业及生产过程中套管的安全。为此,根据弹性力学理论建立了井眼曲率和不均匀外挤力综合影响下的套管抗外挤强度公式。直接建立三维的套管模型,模型长度取10倍的套管外径,在套管的一端施加约束,另一端加弯矩来模拟井眼的弯曲。计算结果表明,在井眼曲率较大时,弯曲井眼中大尺寸厚壁套管抗外挤强度下降较为明显;理论计算的抗外挤强度通常小于模拟值,按照理论设计的套管是偏安全的,但不均匀度较大时需考虑模型计算的误差是否满足要求。

The calculation of the casing collapse strength in bending hole

In the current calculation of the casing collapse strength in bending hole,the effect of hole flexure is not considered so that the casing safety cannot be ensured in the process of the well completion and production.Therefore,the effect of hole curvature was considered in calculating casing strength.The formula for casing collapse strength under the comprehensive effect of hole curvature and uneven extrusion force was established according to the theory of elasticity.The three-dimension model of casing was established directly.The model length adopted ten times' external diameter of casing.The constraint was added to one end of casing and the bending moment to the other end to simulate the hole flexure.The result showed that,when the hole curvature was large,the collapse strength of large-size heavy casing in bending hole decreased remarkably.The collapse strength obtained by theoretical calculation was usually less than the simulation value.The casing designed according to the theory was relatively safe,but the error of model calculation should be considered when the degree of unevenness was high.