高温后花岗岩渗透性及其演变规律试验研究

Experimental study on permeability characteristics and its evolution of granite after high temperature

高温处理对于花岗岩渗透性影响显著,高温后花岗岩的渗透性与其经历的温度、所处的应力状态密切相关。采用压力脉冲衰减法,对高温(100℃~600℃)后花岗岩不同应力状态下的渗透率进行试验研究,在此基础上分析花岗岩宏细观物理力学性质随温度的变化规律,以及高温后花岗岩渗透性随体积应力、孔隙压、有效应力的演变规律。研究结果表明:(1)高温处理后花岗岩渗透率随经历温度呈逐渐增大趋势,500℃以内渗透率增加幅度较小,500℃~600℃花岗岩渗透率会发生一个阶跃性变化;(2)相同高温处理后花岗岩的渗透率随体积应力增大呈现减小趋势,且减小幅度在逐渐变小,相同体积应力下,花岗岩的渗透率随着孔隙压增大而增大;(3)高温后花岗岩渗透率与有效应力呈负指数关系,且渗透率随着有效应力的增大而减小;(4)拟合获得了600℃内高温处理后花岗岩渗透率与温度、有效应力的关系式。研究结果可为干热岩地热人工热储建造提供理论依据和技术支持,丰富和发展了高温岩石力学内涵。

High temperature treatment has a significant effect on the permeability of granite.The permeability of granite after high temperature is closely related to the temperature experienced and the stress state.Using Pressure pulse attenuation method,we studied the permeability of granite after the high temperature(100℃-600℃)under different stress state.On this basis,we analyzed the macro-mesoscopic physical and mechanical properties of granite with temperature,and the evolution law of granite permeability after high temperature with volume stress,pore pressure and effective stress.The results show that:(1)After high temperature treatment,the permeability of granite increases gradually with the temperature experienced.The permeability of granite increases slightly under 500℃,and a step change occurs in the permeability of granite at 500℃-600℃.(2)After the same high temperature treatment,the permeability of granite shows a decreasing trend with the increase of volume stress,and the decreasing range gradually decreases.Under the same volume stress,the permeability of granite increases with the increase of pore pressure.(3)There is a negative exponential relationship between granite permeability and effective stress after high temperature,and the permeability decreases with the increase of effective stress.(4)The relationship between permeability and temperature and effective stress of granite after high temperature treatment under 600℃was obtained by fitting.The research results can provide theoretical basis and technical support for the construction of hot dry rock geothermal artificial heat storage,and enrich and develop the connotation of high temperature rock mechanics.