瞬态力-热耦合作用下水泥环形态对套管应力的影响

基于页岩气水平井压裂工程实际,采用解析法与数值法结合的方式,建立了压裂过程中井筒温度场计算模型和套管偏心、水泥环缺失有限元模型,据此研究瞬态力-热耦合作用下的水泥环形态对套管应力的影响。结果显示:1)页岩气井压裂过程中瞬态力-热耦合作用显著提高了套管应力;套管应力呈先升高后降低的动态变化,最大应力值出现在压裂初期。2)水泥环完整或套管偏心时,瞬态力-热耦合作用降低了套管应力周向分布不均匀差异;水泥环缺失时,套管应力随着缺失角、偏心距的增大而提高。研究结果对于精确计算页岩气井压裂过程中的套管应力具有重要意义。

Impact analysis of cement sheath shape on casing stress under transient mechanical-thermal coupling effect

On the basis of fracturing engineering practice of shale gas wells,wellbore temperature field model and casing eccentricity and cement sheath deficiency finite element models were established by analytical and numerical methods,and the influence of transient mechanical-thermal coupling effect on casing stress was analyzed.The results show that:(1) the coupled mechanical-thermal effect on casing stress is significant,casing stress first increases and then decreases,the maximum casing stress appears at the beginning of fracturing.(2) when the cement sheath shape is integrity or casing is eccentric,the coupled mechanicalthermal effect reduces the difference of the stress along circumference,and when there is deficiency in cement sheath,with the increase of the eccentric distance or deficiency angle,the maximum stress of casing increases.The research results provide a reference for the accurate calculation of casing stress during fracturing in shale gas well.