Production capacity and mining plan optimization of fault/fracture‐controlled EGS model in Gonghe Basin

Abstract

AbstractTaking full advantage of geological conditions is beneficial to reduce the development cost and enhance the exploit of geothermal energy in the Gonghe Basin. In this paper, a thermal‐hydraulic coupled model is put forward to study the heat extraction for Gonghe Basin based on local thermal nonequilibrium theory considering the natural fault. An excellent heat recovery system and reasonable combination of parameters are the premise of sustainable geothermal development. Two doublet systems are introduced to investigate the efficiency of the fault/fracture‐controlled EGS model. A comparative analysis is performed from the aspect of production temperature, heat extraction ratio, flow impedance, injection pressure, thermal power, and electric power. Key parameters (injection rate, injection temperature, production pressure, number of fractures, vertical interval between the two storages, and the storage permeability) are discussed. The results show that the fault‐fracture–controlled doublet model is more suitable for EGS to heat transfer than the common doublet model. The doublet model at a depth of 3300‐3800 m has a temperature gradient of 0.04°C/m. For fault‐fracture–controlled EGS model, the optimal values are 50 kg/s, 15 MPa, 60°C, 310 m, 4 × 10−14 m2, and two for injection rate, production pressure and injection temperature, vertical interval, storage permeability, and fracture number, respectively. The best well pattern layout method for the Gonghe Basin is one injection well and two production wells. The production temperature varies from 196.8°C to 192.7°C when the heat extraction ratio is 0.13 at the end of the operation. Thus, the fault‐fracture–controlled EGS model can provide a mining method and advance the development of geothermal energy for the Gonghe Basin in the future.