表面缺陷深度对套管强度影响规律数值模拟研究

利用有限元软件ANSYS建立深井套管内磨损时的三维有限元模型，模拟计算深井状态下套管受力，分别获得了均匀磨损和非均匀磨损情况下，不同磨损长度和磨损深度时套管在外挤压力作用下的Mises应力值。研究结果表明：当套管磨损深度和外挤压力不变时，套管Mises应力随着磨损长度增加而呈指数关系增加，当磨损长度超过临界值时，套管Mises应力将会保持不变；当磨损长度一定时，均匀磨损时套管最大Mises应力也随着磨损深度增加而呈指数增加；非均匀磨损时套管最大Mises应力与磨损长度呈线性关系增长。并利用数值模拟计算结果回归出Mises破坏失效准则条件下的套管有效应力与磨损长度和磨损深度之间的计算公式，为磨损后套管应力计算提供参考。

Study on Strength Reduction of Casing with Surface Defects

The three-dimensional finite element model is built up by ANSYS according the J55 casing actual dimensions calculating the wearing casing maximum Mises stress imitating the original crustal--stress in the deep stratum conditions. The maximum Mises stress of uniform and non-uniform abrasion are obtained in different wearing lengths and depths. The calculating results show the wearing casings maximum Mises stress has an exponential increased relationship with the wearing length under the fixed wearing depth. For uniform wearing, the maximum Mises stress of casing exponentially increases as the wearing depth decreases; the maximum Mises stress of non-uniform abrasion has a direct linear ratio relationship with the wearing depth. The function of calculating the wearing casing maximum Mises stress is obtained from the numeral resuits under Mises failure criterions. Our methods and results can serve as a reference in calculating the strength of wearing casing.