During the thermal exploitation of enhanced geothermal system(EGS),reservoir permeability varies dynamically under the influence of stress.In order to reveal the coupling mechanism between the permeability of fractured rock matrix and stress field and its influence on the performance of heat mining,a thermo-hydro-mechanical(THM)coupling model of dual mediums including matrix and fracture was established based on the THM coupling theory,and the THM field of the reservoir is analyzed when the matrix and fracture permeability change with the stress.The results show that under the combined action of thermal stress and water pressure,the matrix permeability decreases gradually,and the fracture permeability increases exponentially.Hence,the rate of recovery heat is mainly determined by the dynamic changes of the fracture permeability.However,the predicted fracture permeability is 41.8％higher than the actual permeability if the dynamic changes of the matrix permeability is ignored during the simulation.As a result,the predicted heat breakthrough time is advanced,which would underestimate the system running life of nearly two years.Therefore,it is significant to evaluate the service life of EGS system to consider the coupling effect of fracture and matrix permeability and stress simultaneously.
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