This article presents coupled hydrogeological-thermal simulation of open borehole thermal energy storage system operating under continuous flow regime. A three-dimensional numerical model for ground waterflow and heat transport is used to analyze the thermal energy storage in the ground. The operation scenario consists of continuous injection and recovery and four periods per year to simulate the seasonal temperature conditions. For different parameters of the system, performances were compared in terms of extraction temperature to provide an optimized configuration and operation schedule for boreholes. The influence of injection/production rate and ground thickness is of more importance than other parameters.