目前的套管弯曲力计算模型仅考虑了温度变化引起的弯曲力放大因子, 忽略了弯曲段管体自重沿轴线上分量产生的轴向力. 针对这种情况, 综合考虑温度和自重的影响, 推导出温度和自重双重作用下管体的弯曲力计算公式, 并对套管弯曲力进行校正, 根据双轴应力公式计算出套管抗击强度显著降低. 分析结果表明, 轴向力增大会对套管强度产生严重影响, 压裂时其内压传递到管外, 管内突然泄压会导致管内压力瞬间降到0, 此时是套管抗外挤失效最危险工况; 拉伸载荷计算不精确可直接影响套管抗外挤和抗内压强度校核, 运用提出的计算模型可以较为精确地计算出压裂后套管轴向力. 所得结论对页岩气井套管的强度优化设计具有参考意义.%The current bending force calculation model only considers the bending force amplification factor caused by temperature and neglects the axial force along the axis caused by the casing body weight. Considering the combined influence of temperature and casing body weight, the bending force formula for the casing is de-duced. The casing bending force is then corrected. Significantly reduced anti-collapse strength of casing based on the biaxial stress formula is observed. The results show that the increase of axial force would have a serious impact on casing strength. The inner pressure would be delivered to the outside casing during fracturing. The sudden release of inner pressure could cause a instant drop of inner pressure to zero, presenting the most dangerous condition for cas-ing anti-collapse failure. Tensile load calculation inaccuracies could directly affect the casing anti-collapse and burst strength check. The proposed calculation model allows to a more accurate casing axial force after fracturing. The conclusion could provide references for shale gas well casing strength design optimization.
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