Life cycle dynamic formation temperature response and thermal energy extraction of mine geothermal system considering groundwater flow

Abstract

As mining activities expand deeper, deep high-temperature formations seriously threaten the future safe exploitation, while deep geothermal energy has great potential for development. Combining the formation cooling and geothermal mining in mines to establish a thermos-hydraulic coupling numerical model for fractured formation. The study investigates the formation heat transfer behaviour, heat recovery performance and thermal economic benefits influenced during the life cycle. The results show that the accumulation of cold energy during the cold storage phase induces a decline in formation temperature. The heat recovery phase is determined by the extent of the initial cold domain, which contracts inward from the edge and decelerates the heat recovery rate gradually. With groundwater velocity increases, the thermal regulation efficiency gradually increases, the production temperature decreases, while the effective radius and thermal power increase first and then decrease. The injected volume and temperature significantly affect, with higher injection temperatures slowing thermal recovery, and the thermal regulation efficiency is more sensitive to changes in formation permeability and thermal conductivity. The heat extraction performance is positively correlated with all factors. The levelized cost of electricity is estimated at 0.1203 $/(kW·h) during the cold storage. During the heat recovery, annual profit is primarily driven by cooling benefits.