A parametric study of the thermal recharge of low enthalpy geothermal reservoirs

•We present a model-based study of thermal recharge of low enthalpy geothermal reservoirs.•Thermal conductivity of the confining beds affects thermal recharge significantly.•Thermal recharge is proportional to production rates.•Thermal recharge increases dramatically in thin reservoirs.•Impermeable sections in the reservoir are rapidly depleted of thermal energy.

This study finds that the production profile (temperature and longevity) of low enthalpy geothermal reservoirs depends significantly on the thermal conductivity of the confining beds, which recharge the reservoir by conduction. The thermal recharge furthermore is proportional to the production rate and increases dramatically in thin reservoirs, while impermeable reservoir sections have little effect on the production profile. For the Margretheholm geothermal plant, Copenhagen, Denmark, production temperatures are modelled to decrease by only 7 °C–14 °C after 300 years of production due to thermal recharge. The study emphasizes the huge potential of geothermal energy in the development of environmentally sustainable cities.