温压耦合作用下的套管磨损和应力分布

Casing wear and stress distribution under coupling effects of temperature and pressure

页岩气井压裂过程中,套管变形问题显著。测井成像数据表明,套管磨损是影响套管变形的重要因素。基于页岩气井压裂过程中连续油管对套管磨损的工程实际情况,分析了连续油管行程和磨损深度之间的关系,并且在考虑压裂过程中瞬态温压耦合的基础上,建立了套管磨损三维数值模型,分析了磨损深度、套管压力对套管应力分布的影响。结果表明:随连续油管行程增加,套管磨损深度非线性增大,随注入头载荷增加,套管磨损深度近似线性增大;压裂过程中,完整套管的最大等效应力先增大后减小,呈现显著的动态变化,套管磨损后的应力变化规律与完整套管条件下的变化规律基本一致;套管磨损处存在显著应力集中,随磨损深度、套管压力的增加,最大等效应力近似线性增大。该研究结果对于准确评估页岩气压裂过程中的套管完整性具有重要意义。

During the fracturing of shale gas wells,the problem of casing deformation is serious.Logging imaging data shows that casing wear is an important factor causing casing deformation.Based on the engineering practice of casing wear caused by coiled tubing in shale gas well fracturing process,the relationship between the coiled tubing stroke and wear depth was analyzed.Considering the transient coupling effects of temperature and pressure during the fracturing process,a three-dimensional numerical model for casing wear model was established and was used to analyze the effects of wear depth and casing internal pressure on the stress distribution of the casing.The results show that:with the increase of coiled tubing stroke,the wear depth of casing increases nonlinearly,while the wear depth of casing increases approximately linearly with the increase of injector load;in the fracturing process,the stress of the complete casing increases and then decreases,showing significant dynamics,and the variation law of the stress after casing wear is basically the same as that under complete conditions;there is significant stress concentration at casing wear position,and the maximum stress increases approximately linearly with the increase of wear depth and casing internal pressure.The results of the study are of great significance for the accurate evaluation of casing integrity during shale gas fracturing.