瞬态力-热耦合作用下水泥环完整性分析

发布时间：2019-04-18 14:03

【摘要】：页岩气井工程实践表明,套管压裂易导致水泥环完整性发生破坏出现环空带压。基于套管压裂工程实际,建立井筒温度场模型和套管-水泥环-地层组合体有限元模型,采用解析法和数值法结合方式,计算页岩气井压裂过程中瞬态力-热耦合对水泥环应力大小、分布影响规律。结果表明:压裂过程中水泥环内外壁温差先增大后减小,压裂初近内壁处存在陡峭温度梯度,易导致内壁应力显著提高;瞬态力-热耦合作用导致水泥环内壁应力大幅提升,加剧了水泥环完整性失效的风险,压裂初期为水泥环易发生损坏的"风险段";水泥环内壁最大应力随着时间变化,易产生"多裂纹"形态,加剧环空带压。研究结果可为页岩气井压裂过程中水泥环完整性设计控制提供参考。
[Abstract]:The engineering practice of shale gas well shows that casing fracturing is easy to cause the integrity of cement sheath to be destroyed and annulus belt pressure occurs. Based on the practice of casing fracturing engineering, the wellbore temperature field model and the finite element model of casing-cement ring-formation combination are established, and the combination of analytical and numerical methods is adopted. The influence of transient force-thermal coupling on the stress and distribution of cement ring in shale gas well fracturing process is calculated. The results show that in the process of fracturing, the temperature difference between the inner and outer walls of cement sheath increases first and then decreases, and there is a steep temperature gradient near the inner wall at the beginning of fracturing, which may lead to a significant increase in the stress of the inner wall. The transient force-thermal coupling action causes the stress in the inner wall of the cement sheath to be greatly increased, which aggravates the risk of the integrity failure of the cement sheath, and at the beginning of fracturing, it is the "risk section" where the cement sheath is liable to be damaged. The maximum stress in the inner wall of cement annulus changes with time, and it is easy to produce "multi-crack" form, which aggravates annulus belt pressure. The results can be used as a reference for the design and control of cement sheath integrity during fracturing of shale gas wells.
【作者单位】：中国石油大学(北京);北京工业大学;
【基金】：国家自然科学基金“长水平段非均质页岩储层非均匀分簇射孔优化研究”(编号:51674272) 中石油西南油气田分公司项目“威远长宁页岩气水平井固井质量对井筒完整性的影响”(编号:XNS21JS2014-04)
【分类号】：TE256;TE377

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