高温热采井水泥环缺陷对套管安全性的影响分析

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。

Casing safety analysis with defective cement ring in thermal recovery well

Defective cement ring often leads to non-uniform load of casing in thermal recovery well.Therefore,the defect of cement ring is one of the key causes in casing failure.A numerical model was developed with using Finite Element Method(FEM) to analyze casing safety with a defective cement ring.Temperature field and stress field were fully coupled to calculate casing strength,which the strength degradation of casing,the defective parameters of the cement ring including defective shape,circumferential spread,defective depth and quantity,were all considered.In addition,plastic deformation,residual strength and safety factor were applied to assess the casing safety.Casing failure model was also analyzed in this paper.The result shows that the temperature is different for casing yielded in integrity wellbore and wellbore with defective cement ring.The effect of circumferential spread and defective depth on casing safety is severe.This study not only can reveal the failure mechanism of casing but also can prevent from the casing failure.