长水平段水泥环应力动态变化及失效评价  

Dynamic Changes in Stress and Failure Evaluation of Cement Sheath in Long Horizontal Sections

作　　者：孙小强 曾杰 王建华 王海涛 李辉 席岩 Sun Xiaoqiang;Zeng Jie;Wang Jianhua;Wang Haitao;Li Hui;Xi Yan(Kunlun Digital Technology Co.,Ltd.;College of Architecture and civil Engineering,Beijing University of Technology)

机构地区：[1]昆仑数智科技有限责任公司,北京市石景山区100043 [2]北京工业大学建筑工程学院

出　　处：《石油机械》2024年第11期82-90,139,共10页China Petroleum Machinery

基　　金：国家自然科学基金面上项目“CCUS工程多场耦合及跨时空尺度条件下井筒密封完整性失效机理及控制方法研究”(52374001);中国石油天然气集团有限公司项目“钻完井及井下作业智能优化系统研发-基于智能计算理论的多场耦合作用下井筒完整性评价与控制参数优化技术研究”(2021DJ7401);北京市教委一般科技项目“基于LSTM网络的油气井复杂工况识别研究”(KM202211232013)。

摘　　要：页岩油气水平井压裂过程中井筒密封完整性失效问题频发,但当前较少研究可对于温度压力耦合条件下长水平段水泥环密封完整性进行评价。针对此,建立了压裂过程中全井筒瞬态温度场计算模型,以及长水平段瞬态温度-压力耦合作用下水泥环径向应力和周向应力计算有限元分析模型,基于Mohr-Coulomb准则对于水平段不同位置处水泥环完整性的失效进行了分析,评价了水泥环弹性模量、套管内压以及压裂排量对于长水平段不同位置处水泥环密封完整失效的影响规律。研究结果表明:压裂过程中温度场模型计算结果与Landwark软件误差率低于10%,确保了模型的正确性;同等条件下水平段从井筒趾端向跟端,水泥环承受的径向应力和切向应力增加,井筒跟段是水泥环密封完整性失效的“风险段”;水泥环弹性模量从趾端到跟段呈降序排列,有利于井筒密封完整性的保持;水力压裂过程中降低井口压力或者在井口压力不变的条件下增大压裂排量,可以有效降低水泥环的径向应力和切向应力。研究结果可为固井工艺的优化以及页岩油气井屏障的建立提供参考。The wellbore sealing integrity fails frequently in the fracturing process of shale oil and gas horizontal wells.However,there is less research on the evaluation of the sealing integrity of cement sheath in long horizontal sections under temperature-pressure coupling conditions.In this paper,a model for calculating the transient temperature field of the whole wellbore in the fracturing process,and a finite element model for calculating the radial and circumferential stresses of the cement sheath under the transient temperature-pressure coupling effect in long horizontal section were built.Then,based on the Mohr-Coulomb criteria,the failure of the sealing integrity of cement sheath at different positions in the horizontal section was analyzed,and the influences of the elastic modulus of cement sheath,the internal pressure of casing and the fracturing displacement on the failure of the sealing integrity of cement sheath at different positions in the long horizontal section were evaluated.The results show that the error rate between the temperature field model and Landmark software is less than 10%,verifying the reliability of the model.Under the same conditions,the radial and tangential stresses on the cement sheath increase from the toe end to the heel end of the wellbore,and the heel section of the wellbore is risky for failure of the sealing integrity of cement sheath.The elastic modulus of cement sheath is arranged in a descending order from toe end to heel section,which is favorable for maintaining the sealing integrity of wellbore.Reducing the wellhead pressure or increasing the fracturing displacement while keeping the wellhead pressure constant during the hydraulic fracturing can effectively reduce the radial and tangential stresses of the cement sheath.The research results provide reference for the optimization of cementing technology and the establishment of shale oil and gas well barriers.

关 键 词：水平井压裂 水泥环应力 多级压裂 温度-压力耦合 长水平段 密封完整性 

分 类 号：TE934[石油与天然气工程—石油机械设备]