Hydraulic erosion-heat transfer coupling model for coal and geothermal energy co-exploitation

Co-exploitation of coal and geothermal energy provides a solution for the efficient utilization of hydrothermal resources. To analyze the feasibility of this approach, a hydraulic erosion and heat transfer coupling model is established and validated through laboratory experiments. Then, the evolution of hydraulic and thermal characteristics within the reservoir is analyzed. Finally, the sensitivity of geothermal extraction efficiency is investigated, and the effect of hydraulic erosion on geothermal energy extraction is discussed. The simulation results indicate significant increases in porosity, fluidized particle volume fraction, permeability, and flow velocity near the production well. The hydraulic pressure within the fractured rock zone gradually decreases, and the reservoir temperature decreases non-linearly over time. At the end of extraction, the porosity near the production wall approaches 0.9, and the temperature is reduced to 304 K. Besides, the increase in extraction pressures, production well radii, initial reservoir temperatures, and decrease of cementing strengths of fractured rocks could cause earlier thermal power peaks, while they may also result in rapid depletion of geothermal resources. In addition, the proposed model exhibits significantly higher thermal power compared to the model disregarding hydraulic erosion effects, with the peak thermal power being 38 times greater than the latter.