多级压裂套管偏心条件下微环隙发展规律研究  

Development Law of Micro-Annulus Under Eccentric Conditions of Casing in Multistage Fracturing

作　　者：丁建新 席岩 姚宇 王海涛 温欣 李辉 Ding Jianxin;Xi Yan;Yao Yu;Wang Haitao;Wen Xin;Li Hui(Kunlun Digital Technology Co.,Ltd.;Beijing University of Technology)

机构地区：[1]昆仑数智科技有限责任公司,北京市100043 [2]北京工业大学

出　　处：《石油机械》2023年第12期85-92,共8页China Petroleum Machinery

基　　金：国家自然科学基金青年基金项目“基于压裂过程中四维地质力学的套管变形机理及控制方法研究”(52004013);中国石油天然气集团有限公司科学研究与技术开发项目“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)。

摘　　要：页岩储层开发过程中主要采用水平井和多级压裂技术,其水平段较长易导致套管偏心,进而影响到井筒水泥环密封完整性。为此,基于多级压裂过程中套管内压多次升高和降低的实际情况,建立了套管偏心条件下、循环加卸载作用下微环隙产生和发展的数值模型,基于Mohr-Coulomb准则和损伤理论,计算了多级压裂过程中循环载荷作用下水泥环内边界处累积塑性应变以及微环隙宽度,分析了偏心距、偏心角对于微环隙发展的影响。研究结果表明:相比于套管居中条件,套管偏心后同等循环次数下微环隙宽度更大,增大了水泥环密封完整性失效的风险;随着偏心距的不断增加,最大塑性累积应变区域发生变化,且微环隙宽度不断增加;当水平最小主应力低于垂向地应力时,且循环加卸载次数高于一定值时,随着偏心角的不断增加,微环隙宽度不断降低,且降幅不断增加。研究结果可为多级压裂过程中井筒密封完整性的预防和控制提供参考。Horizontal well and multistage fracturing technologies are mainly used in the development of shale reservoir,however,the long horizontal section may lead to casing eccentricity,and then affect the sealing integrity of cement sheath in the wellbore.Based on the actual situation of multiple increases and decreases in internal pressure of casing in the process of multistage fracturing,a numerical model for the generation and development of micro annulus under cyclic loading and unloading actions under eccentric casing conditions was built.Based on the Mohr-Coulomb criteria and damage theory,the cumulative plastic deformation strain and micro annulus width at the inner boundary of the cement sheath under cyclic loading during multistage fracturing were calculated,and the influence of eccentricity and eccentric angle on the development of micro annulus was analyzed.The results show that compared with the casing centering condition,after eccentricity of casing,the micro annulus width is larger under the same number of cycles,which increases the risk of failure of cement sheath sealing integrity.As the eccentricity continuously increases,the maximum plastic cumulative deformation area changes,and the micro annulus width continuously increases.When the horizontal minimum principal stress is lower than the vertical ground stress,and when the number of cyclic loading and unloading times is higher than a certain value,as the eccentric angle continuously increases,the micro annulus width continuously decreases,and the decrease amplitude continuously increases.The research findings provide reference for the prevention and control of wellbore sealing integrity in the process of multistage fracturing.

关 键 词：多级水力压裂 套管偏心 密封完整性 微环隙 数值模拟 累积塑性 

分 类 号：TE21[石油与天然气工程—油气井工程]