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针对水泥环缺陷导致套管承受非均匀载荷并引起套管失效的问题,建立了套管、含缺陷水泥环和地层耦合系统有限元计算模型。将温度场与应力场耦合,考虑套管强度降低,计算了水泥环缺陷形状、缺陷环向开度、缺陷深度及缺陷数量对套管安全的影响。应用塑性变形、剩余强度和安全系数来评价水泥环含缺陷井筒中套管的安全性,并分析了套管的失效模式。计算结果表明:完整井筒和水泥环含缺陷井筒中套管的屈服温度相差较大,水泥环缺陷环向开度和深度对套管安全的影响比较大。此研究为揭示套管失效机理提供了依据,对预防套损具有指导意义。
Aiming at the problem that the casing defects are caused by the non-uniform load of the casing caused by casing defects, and the failure of the casing is caused, the finite element model of the casing, the cement-free casing and the formation coupling system are established. Coupling the temperature field with the stress field, considering the decrease of the casing strength, the influence of the shape of the cement ring defect, the annular opening of the defect, the depth of the defect and the number of defects on the casing safety were calculated. The plastic deformation, residual strength and safety factor are used to evaluate the safety of the casing in the casing with the defect of the cement sheath, and the failure modes of the casing are analyzed. The calculation results show that the yield temperature of the casing in the wellbore with imperfect inclusion in the cement casing differs greatly, and the influence of the annular opening and depth of the cement sheath on casing safety is relatively large. This study provides a basis for revealing the mechanism of casing failure and is of guiding significance in preventing casing damage.