摘要
在石油钻井过程中,深部裂隙地层岩体结构场环境复杂,加之钻井液更容易渗漏及应力场变化,常常容易造成井壁失稳。本文基于多场耦合理论,采用UDEC分析软件,在考虑天然裂缝和井壁周围围岩内摩擦角减小的情况下,研究了钻井液液体压力影响下的深部裂隙岩体在钻井过程中的井壁稳定性问题。研究发现:考虑天然裂缝情况下,欠平衡钻井更有利于减少钻井液的渗透范围,从而减少井壁失稳的风险;欠平衡钻井的井眼在最大水平主应力方向的位移变化最为明显,也最容易导致井壁在该方向上由于变形过大而失稳;而当钻井液压力大小与地层最小水平压力大小相当时,井壁相对越稳定。
The environment of rock structure field for deep fractured formation is complex,and the drilling fluid is more likely to leak to lead to the change of stress field,which often likely gives rise to wellbore instability during drilling.Based on the multi-filed coupling theory,UDEC is used to investigate wellbore stability problem of deep fractured rock mass during drilling under the effect of drilling fluid pressure.At the same time,the natural fractures and the reduction of friction angle of wellbore surrounding rock are also considered.The investigation shows that underbalanced drilling is more conducive to reduction of drilling fluid leakage when considering natural fractures,and this is helpful to lower the risks of wellbore instability.Also,there is the most obvious displacement changes for underbalance drilling in the direction of the maximum horizontal principal stress,so that it is most likely to result in wellbore instability because of excessive deformation in this direction.In addition,there is the better stability of wellbore while the pressure of drilling fluid is almost equal to the minimum horizontal pressure of formation.
作者
张士科
于锦彩
付德伟
ZHANG Shike;YU Jincai;FU Dewei(School of Civil Engineering and Architecture,Anyang Normal University,Anyang 455000,China)
出处
《安阳师范学院学报》
2019年第5期133-137,共5页
Journal of Anyang Normal University
基金
河南省自然科学基金项目(182300410160)
河南省科技攻关计划项目(182102310804)
河南省高等学校青年骨干教师培养计划(2018GGJS122)
河南省高等学校重点科研项目(20B560002)
安阳市科技攻关计划项目(安科[2018]66号)
安阳师范学院大学生创新基金项目(ASCX/2019-Z154)
关键词
井壁稳定
多场耦合
数值模拟
离散元
岩体破坏机理
Wellbore stability
Multi-filed coupling
Numerical simulation
Discrete element method
Failure mechanism of rock mass
