不均匀磨损深度对套管应力的影响研究

Study on the Effect of Uneven Wear Depth on Casing Stress

为研究套管内壁不均匀磨损深度对套管抗挤强度和套管应力的影响,建立了磨损套管-水泥环-围岩组合体力学模型,应用有限元分析软件和ISO 10400推荐的套管抗挤强度计算模型对不同磨损深度下的套管应力和抗挤强度进行计算。计算结果表明:套管最大外挤力和套管抗挤强度与不均匀磨损深度之间均呈线性关系,随着不均匀磨损深度的增加,套管最大外挤力缓慢增大,而套管抗挤强度显著降低;随着不均匀磨损深度的增加,最大磨损深度处套管内壁应力显著增加,而未磨损处套管内壁应力几乎不受影响;随着不均匀磨损深度的增加,最大磨损深度处套管外挤力逐渐减小,而磨损边缘处套管外挤力显著增大;当套管内壁不均匀磨损深度达2.4 mm时,套管抗挤强度降幅达26%,此时套管存在挤毁风险。研究结果可为页岩气藏开发中磨损套管应力分析提供参考。

In order to study the influence of uneven wear depth on casing collapse strength and casing stress,a mechanical model of wear casing-cement sheath-surrounding rock combination body was established. Finite element analysis software and ISO 10400 recommended casing collapsing strength calculation model have been used to calculate the casing stress and collapsing strength under different wear depths. The calculation results show that the maximum casing external pressure and the casing collapsing strength have a linear relationship with the depth of uneven wear. As the depth of uneven wear increases,the maximum casing external pressure increases slowly,but the casing collapsing strength decreases significantly. With the increase of the uneven wear depth,the stress on the inner wall of the casing increases significantly at the maximum depth of wear. The stress on the inner wall of the casing is almost unaffected at the unworn casing. As the increase of the uneven wear depth,the casing external pressure decreases gradually at the maximum wear depth but increases significantly at the wear edge. When the uneven wear depth of casing wall is 2. 4 mm,the casing collapsing strength is decreased by 26%,presenting a risk of casing collapse. The study results can provide references for the stress analysis of wear casing in the development of shale gas reservoirs.