井内液柱压力对井壁稳定性的影响  

Influence of liquid column pressure on well bore stability

作　　者：马赵飞 凌雪 柳洪杰 刘子晨 梁高 MA Zhaofei;LING Xue;LIU Hongjie;LIU Zichen;LIANG Gao(China University of Geosciences(Beijing),Beijing 100083,China;Coal Mine Grouting Technology Innovation Base,Beijing 100040,China;Hainan Haida Engineering Testing Technology Co.LTD,Haikou Hainan 570228,China)

机构地区：[1]中国地质大学(北京),北京100083 [2]煤矿开采注浆技术创新基地,北京100040 [3]海南海大工程检测科技有限公司,海南海口570228

出　　处：《钻探工程》2023年第S01期143-148,共6页Drilling Engineering

基　　金：国家自然科学基金面上项目“浅层水力裂纹扩展和闭合的非线性流-固耦合规律研究”(编号:12172339);科学技术部国际科技合作专项项目“井下闭环高精度导向钻进技术”(编号:2006DFB21300)。

摘　　要：为探究液柱压力对井壁稳定性的影响,研究井壁围岩在井内液柱压力及地应力作用下的受力特征及裂纹扩展模式,采用三轴围压水压试验的方法,改变围压以及井内水压的方式对细砂岩进行室内试验,并通过CT扫描的方法进行内部裂纹观察。研究表明:(1)围压一定时,细砂岩的偏应力-应变曲线的各阶段变化趋势受孔内水压的影响较大,且峰值强度、残余强度、轴向峰值应变与围压、孔内水压均呈正相关。孔内水压的作用延缓了细砂岩的压缩屈服阶段受力破坏的过程,增加了细砂岩的延性破裂程度。(2)CT扫描发现一定围压作用下,细砂岩的主剪切破裂面与轴向的夹角呈现出随着水压的增大而减小的规律,且剪切裂纹轨迹由岩样外侧逐渐向中心孔壁靠近偏转;(3)随着水压的增加,孔内岩块塌落方式由集中塌落转变为零散塌落;水压越大,孔内的岩块塌落面积和塌落度越小。提升水压到合适强度,可以提升井壁稳定性,减小井壁失稳发生的可能。In order to explore the influence of the liquid column pressure on the stability of borehole,study the stress characteristics and crack propagation mode of the surrounding rock under the action of the liquid column pressure in the borehole and the ground stress,the triaxial confining pressure hydraulic test method is adopted to carry out the laboratory test on the packsand by changing the confining pressure and the water pressure in the borehole,and the inner observation of the packsand is carried out by CT scanning method.The results show that:(1)when the confining pressure is constant,the variation trend of deviatorial‑strain curve of packsand at each stage is greatly affected by bore water pressure,and the peak strength,residual strength and axial peak strain are positively correlated with confining pressure and bore water pressure.The action of water pressure in the pore delays the process of mechanical failure in the compressive yield stage of packsand and increases the degree of ductile fracture of packsand.(2)CT scan shows that under certain confining pressure,the angle between the principal shear fracture plane and the axial direction of the packsand decreases with the increase of the water pressure in the pore,and the shear crack track gradually deflects from the outside of the rock sample to the central pore wall.With the increase of water pressure in the hole,the collapse mode of rock block in the hole wall changes from centralized collapse to scattered collapse.The larger the water pressure in the hole,the smaller the collapse area and collapse degree of the rock in the hole wall.(3)Increasing water pressure can improve the stability of borehole and reduce the possibility of borehole instability.

关 键 词：井壁稳定性 细砂岩 孔内水压 三轴实验 CT扫描 力学性能 裂纹扩展 

分 类 号：P634[天文地球—地质矿产勘探] TE24[天文地球—地质学]