摘要
地震活动是断层非稳定滑动引发的弹性能在短时间内的释放过程,近年来为实现非常规储层开发而实施的储层压裂过程中,高压流体注入地层会诱发断层活化而产生非稳定滑动。断层非稳定滑动过程中的“黏-滑”行为导致了地震的发生,本次研究关注流体注入诱发断裂面失稳的摩擦行为,并且与无流体注入条件下的断裂面失稳摩擦过程进行了对比分析。为了探究储层中流体注入在断层活化中的作用,针对页岩样品分别开展了应力驱动与恒定增压速率流体注入两种条件下的断裂面摩擦滑移失稳试验。通过实时监测应力与位移的变化并计算求解剪应力和摩擦系数,深入分析并总结高压流体注入对断裂面失稳后的摩擦演化过程。研究表明,在无流体注入条件下,“黏-滑”行为产生后断裂面摩擦呈现弱化和恢复的反复循环,摩擦系数相对稳定在数值~0.6附近循环变化;而在流体注入条件下,断裂面失稳瞬间产生应力降,并快速演化为较长时间段内高频重复的“黏-滑”行为且滑移速度很慢;之后由于出现连续的摩阻弱化“黏-滑”行为而产生显著滑移段,最终由于流体压力逐渐接近断裂面所处位置的最小主应力,出现连续的摩阻强化“黏-滑”行为,此过程中滑移速度逐渐减小并最终停止滑移。试验证实流体注入可使断裂面摩擦系数从~0.6显著衰减甚至接近于0,这也揭示了孔隙压力对断裂面稳定性的控制性作用,在储层改造过程中通过孔隙压力的调控可以有效预防由于断裂面非稳定性滑动导致的地震事件。
Seismicity results from the rapid release of elastic energy during unstable fault slip.Recent studies have demonstrated that high-pressure fluid injection during hydraulic fracturing for reservoir stimulation can induce fault activation and seismic events.The stick-slip behavior associated with unstable fault slip plays a key role in triggering such seismicity.This study investigates the frictional behavior of fault instability induced by fluid injection,with comparative analysis of dry(non-fluid-injection)conditions.Through triaxial compression experiments on shale specimens,we examine fault slip instability under two loading conditions:(1)axial stress-driven slip and(2)constant-rate fluid injection.By monitoring stress and displacement evolution while calculating shear stress and friction coefficients,we systematically analyze how fluid injection affects post-instability frictional behavior.Key findings reveal:(1)Under dry conditions,the friction coefficient exhibits cyclic weakening and recovery around~0.6 following stick-slip events.(2)With fluid injection,immediate stress drop triggers instability,evolving into prolonged slow slip with high-frequency stick-slip recurrence.(3)Subsequent frictional weakening leads to significant slip displacement until fluid pressure approaches the minimum principal stress,when strengthening behavior dominates-ultimately ceasing slip as sliding velocity asymptotically approaches zero.The experiments demonstrate that fluid injection can reduce the friction coefficient from~0.6 to near-zero values,unequivocally establishing pore pressure’s controlling influence on fault stability.These results provide critical insights for preventing induced seismicity during reservoir stimulation through optimized pore pressure management.
作者
王泽华
赫建明
郑博
毛天桥
李守定
李晓
WANG Zehua;HE Jianming;ZHENG Bo;MAO Tianqiao;LI Shouding;LI Xiao(Key Laboratory of Deep Petroleum Intelligent Exploration and Development,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《工程地质学报》
北大核心
2025年第3期858-865,共8页
Journal of Engineering Geology
基金
国家自然科学基金项目(资助号:42090023)
国家重点研发计划项目(资助号:2023***3106500).
关键词
页岩
断层滑移
流体注入
摩擦行为
Shale
Fault slip
Fluid injection
Frictional behavior
作者简介
第一作者:王泽华(2000-),女,硕士生,主要从事工程地质力学方面的学习与科研工作.E-mail:17389239939@163.com;通讯作者:赫建明(1974-),男,博士,研究员,博士生导师,主要从事工程地质力学方面的科研与教学工作.E-mail:hjm@mail.iggcas.ac.cn。
