摘要
花岗岩节理被认为是提升增强型地热系统(EGS)储层渗透性能的研究对象。花岗岩节理长期处于高温环境中,研究实时高温环境下花岗岩节理剪切行为是解决EGS储层渗透性能提升问题的关键和基础。为此,本文借助岩石剪切伺服试验机及力-热-水耦合剪切试验盒开展了实时高温下花岗岩节理直剪试验。结果表明:花岗岩节理抗剪强度及剪切刚度均随温度升高呈连续劣化趋势,主要划分为两个阶段:缓慢降低阶段(30~200℃)和快速降低阶段(200~400℃)。高温加剧了花岗岩节理表面凸体的剪切破坏,导致节理面剪胀变形随温度的升高而逐渐减小,且减小幅度随法向应力的增加而增大。温度与法向应力间的耦合协同作用加剧了花岗岩节理面的损伤,随温度及法向应力的增加(10 MPa、30℃至30 MPa、400℃),花岗岩节理面剪切损伤面积占比增加了21.41%。高温加剧花岗岩节理表面凸体剪断是节理面粗糙度随温度升高而降低的主要原因。
In recent years,granite fractures have been considered an effective research object to improve the permeability of enhanced geothermal system(EGS).Granite fractures are always in a high-temperature environment,and their shear behavior treated by real-time high temperature is the key to promoting EGS permeability.Hence,the granite fractures shear tests under real-time high temperature were conducted with MTS 816 rock testing machine with a high-temperature sealed shear box.The results indicate that fracture peak shear strength and shear stiffness show a continuous deterioration trend as the temperature increases,which can be classified into a slowly declining stage(30−200℃)and a rapidly declining stage(200−400℃).High temperature deteriorates the asperity shear failure on granite fracture surface,which leads to the reduction of the dilatancy deformation of fracture surface with increasing temperature,and its decreasing amplitude becomes larger with increasing normal stress.Coupling synergy between temperature and normal stress can exacerbate shear damage on granite fracture surfaces,and the percentage of shear damage area increases by 21.41%on granite fracture surface as temperature and normal stress increases from 10 MPa and 30℃to 30 MPa and 400℃.High temperature aggravates the damage of asperities,which is the principal cause of the degradation of fracture surface roughness with increasing temperature.The research results can provide a theoretical guide for enhancing reservoir permeability and connectivity in geothermal energy development engineering.
作者
李杨杨
党金铭
张士川
沈宝堂
郑丹
张浩争
侯嘉琦
LI Yang-yang;DANG Jin-ming;ZHANG Shi-chuan;SHEN Bao-tang;ZHENG Dan;ZHANG Hao-zheng;HOU Jia-qi(State Key Laboratory of Mining Disaster Prevention and Control Co-founded(Shandong University of Science and Technology),Qingdao 266590,China;CSIRO Mineral Resources,Queensland Centre for Advanced Technologies,Queensland 4069,Australia)
基金
Project (51974173) supported by the National Natural Science Foundation of China。
关键词
岩石力学
花岗岩节理
实时温度
抗剪强度
损伤面积
rock mechanics
granite fractures
real-time temperature
shear strength
damage area
