Impacts of boundary conditions on reservoir numerical simulation and performance prediction of enhanced geothermal systems

Fractured reservoir boundary conditions are crucial to numerical study on reservoir simulation and performance prediction of an enhanced geothermal system (EGS) but have received little attention in previous studies. We established an integrated model involving fractured reservoir and Double-flash geothermal power plant to compare heat extraction and power generation of the EGS under recharge and no-flow boundary conditions based on geothermal characteristics of Gonghe Basin, China. The recharge boundary conditions allow fluxes of mass and heat to cross reservoir boundaries, whereas the no-flow disallow such fluxes. The results show that the heat extraction potential around the periphery of the reservoir is overlooked under no-flow boundary conditions. Moreover, the fluxes of mass and heat across the reservoir boundaries exert limited influence on heat extraction process in initial stage, but they affect the process significantly in later stage. Additionally, compared with the EGS under no-flow boundary conditions, that under the recharge has a longer lifespan of 20%, and produces 8% more electricity power. It is also found the EGS maintains high-level power generation performance in the initial period under both boundary conditions, while the electricity output and thermal efficiency decrease significantly in the following stage. (C) 2019 Elsevier Ltd. All rights reserved.