Abstract:

The geothermal energy exploitation in enhanced geothermal system involves the coupled processes of temperature and pressure, the spatial and temporal variation of which is the key issue. Based on the deep geological condition of Xujiaweizi in Songliao basin, using the TOUGH2 software, we simulate the variation of temperature and pressure in fracture-matrix media system, analyze the difference of geothermal development in different depth levels, and study the effects of important factors including the permeability and porosity of porous and fractured media, rock thermal conductivity, well radius, injection pressure and temperature, and surrounding matrix. The results show the pressure distribution is dominated by production well with large pressure gradient at the injection well and the impact of injection well increases with time. Temperature increases from injection well to production well and the area of decrease of temperature increases as the development of geothermal. Mass and heat extraction rate reduce and stabilize with time. The simulation results of different depth levels indicate the great mass and heat extraction rate and large change of pressure and temperature exist in the big depth level because of large water mobility. The effects of factors including fractured media permeability, injection/production well pressure and temperature, and well radius on pressure and temperature of the system are great, and ultimately it affects heat extraction efficiency. While the effects of another factors are not obvious.

Key words: enhanced geothermal system, coupled thermal-hydrodynamic processes, numerical simulation, Songliao basin