Since its closure, the abandoned and flooded Con Mine has been considered as a geothermal resource. This interest prompted this new research project. The objective of this research is to provide a revised estimate of the geothermal potential of the abandoned Con Mine. An improved analytical approach based on an energy balance calculation for estimating the geothermal energy contained in a flooded mine is presented. The analytical method is based on the Finite Line Source equation which considers cooled or heated mine tunnels as heat sources or sinks with a constant heat exchange rate. For the calculations, the underground mine geometry is simplified to a linear heat source of equivalent length and fixed radius. The preliminary results obtained with this approach are a geothermal potential of 0.32 MW for heating and 1.1 MW for cooling, with a heat loss of 36% over 25 years. The results of this approach are to be compared to those obtained with a numerical model for the estimation of geothermal resources. The analytical approach will be further improved to reproduce more representative numerical results.