摘要
为研究高密度钻井液导致井壁坍塌的机理,分析了直井的井周应力分布规律,以及径向、周向和垂向应力随钻井液液柱压力的变化规律,得出当提高钻井液密度时,井壁沿水平最大地应力方位易发生剪切破坏;基于井周应力分布特点和Mohr-Coulumb强度准则获得了井壁最大、最小主应力分别是径向、周向应力和垂向、周向应力两种情况下的坍塌压力解析表达式,并通过一口高压井实例分析了井壁坍塌压力随井深的变化规律,证明钻井液密度过高时会导致井壁坍塌。研究结果可为钻井液密度安全窗口的设计提供理论依据。
In order to study the borehole wall collapse mechanism on the condition of high drilling fluid density,the variation law of borehole radial stress,circumferential stress and vertical stress with the drilling fluid hydraulic pressure are studied.It is found that when the drilling fluid density increases,shear failure is prone to happen on the borehole wall along the maximum horizontal in-situ stress direction.The stress state around the well and Mohr-Coulumb strength criterion are utilized to obtain the collapse pressure analytic expressions of the two cases.The two cases include that maximum and minimum principal stress of wellbore wall are the radial stress,circumferential stress and vertical stress,circumferential stress respectively.Then an engineering example analysis are taken,the well collapse pressure changing law with the well depth is obtained,the result proves that if the drilling fluid density is too high,well collapse could still happen.The research would provide a theoretical basis for the design of mud weight safety window.
作者
幸雪松
周长所
曹文科
XING Xuesong;ZHOU Changsuo;CAO Wenke(CNOOC Research Institute Co.Ltd.,Beijing 100028,China;School of Petroleum Engineering,Changzhou University,Changzhou Jiangsu 213164,China)
出处
《重庆科技学院学报（自然科学版）》
CAS
2021年第5期44-47,共4页
Journal of Chongqing University of Science and Technology：Natural Sciences Edition
基金
国家自然科学基金项目“基于水泥凝固行为的油井水泥环初始应力形成机制研究”(51904037)
江苏省高等学校自然科学研究面上项目“低温流体诱发干热岩储层井周围岩失稳机理研究”(19KJD440001)。
作者简介
幸雪松(1978-),男,硕士,高级工程师,研究方向为海上油气田钻完井技术;通信作者:曹文科(1984-),男,博士,讲师,研究方向为岩石力学。
