Numerical analysis of heat mining and geological carbon sequestration in supercritical CO2 circulating enhanced geothermal systems inlayed with complex discrete fracture networks

Enhanced geothermal systems using supercritical CO2 (scCO(2)-EGS) as working fluid in place of water provides better heat extraction rate and sequestrates CO2 in the formations for reducing atmospheric CO2 content and the greenhouse effect. This paper proposed a numerical three-dimensional fully coupled thermo-hydro-mechanical (THM) model to simulate and evaluate the performances of heat mining and geological carbon sequestration in scCO(2)-EGS embedded in complex discrete fracture networks. The variable thermophysical properties of supercritical CO2 in response to pressure and temperature are taken into account during the reservoir development. Verification, sensitivity analysis, and convergence for the model are accomplished. The three-spot layout of the practical EGS project at Soultz-sous-Forets is then simulated using a stochastic DNF model under different operation pressures. The efficiencies and quantities of heat mining, carbon sequestration, and production of electric power for a period of 30 years have been studied and discussed. By verification against analytical solutions, the results demonstrate that the current nuermical model is effective to investigate the details of the multi-physical interactions in scCO(2)-EGS. (C) 2019 Published by Elsevier Ltd.