Analysis on the heat extraction performance of multi-well injection enhanced geothermal system based on leaf-like bifurcated fracture networks

Based on the fractal and bifurcation theory, a leaf-like bifurcated fracture network is introduced in the multi-well injection enhanced geothermal system (EGS) which could depict the heterogeneity of fractures. A thermal-hydraulic model is established to investigate the space-temporal evolution of temperature and pressure field, effects of leaf-like bifurcated fracture networks characteristic on heat extraction performance. The results show that fractures are the key channel for heat extraction of working fluid, investigating the fracture properties on heat extraction performance is necessary. For the leaf-like bifurcated fracture network EGS, a higher fracture bifurcation level and bifurcation length ratio is beneficial to obtain a better heat extraction performance because of the higher fracture uniformity. The fracture angle also has a positive effect on heat extraction, while its effect is weaker than bifurcation level and length ratio. The fracture aperture ratio has little effect on the heat extraction performance. Key findings of this study provide some reasonable suggestions on fracturing operation and production parameters selection of multi-well injection EGS. (C) 2020 Elsevier Ltd. All rights reserved.