Study On The Coupled Thermal-Hydrologic-Mechanical Model In Fractured Rock Mass And Its Application

During the extraction process of geothermal resources, there are complex coupling behaviors of temperature, seepage and stress fields in the internal heat reservoir, so the study about the distribution of various physics fields within the heat reservoir is becoming one of the important issues to be solved in the geothermal reservoir engineering. In this paper, theoretical analysis and numerical simulation are used for the study of multi physics coupling in geothermal reservoir. A new THM model containing solid deformation, fluid flow and heat conduction is established and this model is applied to the extraction of geothermal. The following conclusions are obtained:(1)Evolution model of porosity and permeability during the extraction process of geothermal resources and THM coupling model are established. Coupling mechanism and effect of coupling term on THM coupling field are studied. The result shows that: The convective term cannot be omitted due to lager influence on temperature field.(2)Having geothermal extraction as the background, in accordance with the actual situation of geothermal projects and the previous work, two-dimensional well model is established, and then the effect on reservoir permeability and geothermal capacity are simulated and analyzed. The research shows that: eeduce of injection temperature and increase of producing pressure differential can improve the production greatly. The geothermal extraction ability of Supercritical CO2 is 4.55~6.33 of H2 O.(3)Based on statistical regularities of fracture distribution within the reservoir, the fractures are randomly generated. A mathematical model containing seepage control equation and temperature control equation of fracture are established to study the influence of fracture aperture on geothermal extraction. The result indicates that: the increase of both fracturing and natural fracture can lead to the increase of geothermal extraction, and the influence of natural fracture is more obvious.(4)Considering the diversity of well pattern, simulations of two production wells on the same side of injection well or on the both sides are analyzed. The result shows that: when the production wells are in the same side, the interference between the production wells can restrain the output of geothermal extraction.