深层地热储层水力剪切增透机制研究进展

A review of the research on the mechanism of hydro-shearing in geothermal reservoir

在增强型地热系统(EGS)中,低压注水触发裂隙网络剪切滑移是热储增透的主要技术手段之一,对提升储层取热效率具有重要作用。然而,多场耦合作用下水力剪切发生的机制异常复杂,已成为储层热提取效率提升的关键问题,也是地下工程诱发地震防控的热点和难点问题。多场耦合作用下水力剪切增透机制涉及许多新问题,很多现有理论在高温高压下不再完全适用,迫切需要基础理论的创新、试验装备的研发和工程技术的突破。在阐述储层水力剪切技术原理和回顾研究现状的基础上,紧扣多场耦合作用下裂隙岩体水力剪切滑移机制这一主题,阐明了该机制研究的关键科学与技术问题,主要包括:①深部高应力岩体黏聚力和内摩擦角的温度效应;②多场耦合作用下水力剪切滑动判别准则研究;③多场耦合作用下有效应力理论的适用性及参数优化;④多场耦合作用下裂隙岩体的剪切破坏动力学响应特征;⑤热冲击效应对干热岩水力剪切机制的影响与评价;⑥水力触发剪切与诱发地震的关系及地震人工解危思路。系统介绍地热储层水力剪切增透机制,全面评述水力剪切增透技术的发展过程,总结并讨论水力剪切机制的关键科学与技术问题,以便国内同行对其有全面的了解和认识,助力这项技术在国内的推广和应用。

In the enhanced geothermal system(EGS),a low-pressure water injection trigged rock fracture shear is a key technique to enhance the fluid conductivity and improve the heat extraction efficiency of geo-thermal reservoir.However,the mechanism of hydro-shearing under hydro-thermo-mechanical-chemical(HTMC)coupled conditions is extremely complex which has become a key issue for heat extraction and a hot topic for earthquake prevention and control in EGS.Furthermore,lots of new problems arise and many existing theories are no longer fully applicable under high temperature and high pressure(HTHP).This in turn requires that the theoretical innovation,experimental equipment development and engineering technique breakthroughs should be made to promote the progress of geothermal energy development.By reviewing the current research status of hydro-shearing mechanism,the authors focused on the topic of hydro-shearing mechanism of fractured rock mass under HTMC coupling and clarified some key scientific and technical problems including:①evolutions of the cohesive strength and internal friction under high temperatures;②HTMC coupled effect on hydro-shearing criteria;③applicability and parameter optimization of effective stress theory;④dynamic failure response of hot-dry-rock fractures under hydro-shearing;⑤effect of thermal shock on hydro-shearing;and⑥the relationship between water injecting induced shearing and the possibility of induced earthquake,and potentials about releasing earthquake using hydro-shearing technique.By re-viewing the mechanism of hydro-shearing of the EGS reservoir,the authors would like to summarize and discuss the key scientific and technical problems,thus it may be helpful to have a comprehensive understanding of hydro-shearing and promote the application of the technique.