Numerical modelling of flow and heat transport in closed mines. Case study Walsum drainage province in the Ruhr coal-mining area

High geothermal potential and multiple mine-water-based geothermal installations in Germany and other countries improve the relevance of detailed studies and modeling of promising sites. In this context, we developed a numerical model of water flow and heat transport in the Walsum mine drainage province in the west of the Ruhr coalmining area using the available data on geology, mining, water levels, pumping, and the temperatures of deep rocks and mine water. The model was validated by varying the parameters of groundwater recharge and hydraulic conductivity to achieve sufficient consistency with measured inflows and pumping rates from the central pumping facility located in the Walsum 2 shaft. The calculated mine water temperature of 30.3 ºC is close to the average of the measured temperature varied within the range of 29 – 33 ºC during the last years of mine maintenance. Using the numerical model, we evaluated the expected thermal capacity of a hypothetical open-loop circulation system and two closed-loop geothermal systems within the study area. The installation and operation of these systems would enable the generation of a thermal capacity from a few dozen kW to 1 MW sufficient for small-size to mid-size heat consumers with insignificant impact on the high thermal energy potential of the Walsum mine drainage province