期刊文献+

断裂带破碎地层井壁稳定机理的离散元法分析 被引量:8

Analyzing well instability mechanisms in broken formations of faulted zones based on discrete element method
下载PDF
导出
摘要 受挤压构造运动影响,顺北5号断裂带奥陶系地层破碎,钻井过程中井壁坍塌掉块严重。由于破碎地层岩石的变形及应力是不连续的,破碎岩块间不存在黏聚力,导致常规的基于连续介质的岩石力学分析方法不适用于此类破碎地层。而离散单元法将含结构面的岩体假定为若干刚体组合,可以刻画变形及应力的非连续性,适用于破碎性地层建模。首先针对地层破碎特性提出能更加合理地表征钻井液封堵性能的新指标--压力传递系数,该系数可通过简单的实验获取;之后建立了适用于顺北破碎带的离散元模型;利用标定的模型分析了不同井斜角、钻井液密度、钻井液压力传递系数对井壁坍塌的影响程度。研究发现:破碎地层失稳是岩块受力平衡的打破造成的(而非岩块本身的强度破坏造成),钻井液压力传递造成井壁周围孔隙压力增加,降低岩石间的挤压力同时降低摩擦因数,导致摩擦力大幅度下降引发岩块失稳;破碎带岩石的尺寸影响井壁稳定性,岩块越破碎越容易发生失稳;随着井斜角增加,井壁失稳风险急剧增加;不同压力传递系数的模拟结果显示,钻井液安全密度窗口随封堵性提高得到不同程度的提高,各影响因素的容错率提高。该研究可为破碎地层安全高效钻井工程措施制定提供指导。 Due to the effect of compressive tectonic movement,the Ordovician formation in Shunbei 5 faulted zone is broken,leading to serious well collapse and fallout in the process of drilling.The deformation and stress of broken formation rocks are discontinuous and there is no cohesion between broken rocks,so the conventional rock mechanical analysis method based on continuous medium is not applicable to this type of broken formation.The discrete element method assumes the rock mass with structural surface as the combination of several rigid bodies to depict the discontinuity of deformation and stress,so it is applicable to the modeling of broken formation.In this paper,a new indicator which can characterize the plugging capacity of drilling fluid more rationally by considering formation breaking features was proposed,namely pressure transfer coefficient,which can be obtained by means of simple experiment.Then,the discrete element model applicable to Shunbei faulted zone was established.Finally,the calibrated model was adopted to analyze the influence degree of hole deviation angle,drilling fluid density and pressure transfer coefficient on well collapse.And the following research results were obtained.First,the instability of broken formation is the result of the unbalanced stress on rock mass instead of the strength failure of the rock mass itself.The pressure transfer of drilling fluid leads to the increase of the pore pressure around the well and the decrease of inter-rock compressive force and friction coefficient,and thus the great decrease of friction force results in the instability of rock mass.Second,the rock size in the faulted zone has an influence on well stability.The more broken the rock mass is,the more easily the instability happens.Third,the risk of well instability increases sharply with the increase of hole deviation angle.Fourth,the simulation results of different pressure transfer coefficients indicate that the safety density window of drilling fluid is increased in different degrees with the incre
作者 翟科军 寇春松 陈修平 赵海峰 ZHAI Kejun;KOU Chunsong;CHEN Xiuping;ZHAO Haifeng(Research Institute of Petroleum Engineering,SINOPEC Northwest Oilfield Company,Urumqi 830001,Xinjiang,China;SINOPEC Key Laboratory of Enhanced Recovery of Fractured-Cave Reservoir,Urumqi 830001,Xinjiang,China;College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing 102249,China)
出处 《石油钻采工艺》 CAS 北大核心 2021年第5期559-565,共7页 Oil Drilling & Production Technology
基金 国家自然科学基金面上项目“一种复杂缝网的能量断裂准则及其在致密砂岩压裂模拟中的应用”(编号:11672333) 中国石油化工股份有限公司重大科技项目群“顺北油气田一区优快钻井技术研究”(编号:P18021-1)部分研究成果。
关键词 破碎地层 井壁稳定 钻井液封堵性 离散元模型 压力传递系数 broken formation well stability plugging capacity of drilling fluid discrete element model pressure transfer coefficient
  • 相关文献

参考文献7

二级参考文献45

共引文献61

同被引文献132

引证文献8

二级引证文献10

相关作者

内容加载中请稍等...

相关机构

内容加载中请稍等...

相关主题

内容加载中请稍等...

浏览历史

内容加载中请稍等...
;
使用帮助 返回顶部