The feasibility of combined extraction injection one-well systems for geothermal groundwater utilization was evaluated by means of a numerical parameter study. One-well systems require little space, but it is critically important to avoid circulation flow resulting in a thermal short circuit. Numerical models of groundwater flow and heat transport were performed to check the influence of various hydrogeological and technical parameters. Results show that circulation flow can be avoided in most cases, mainly when hydraulic gradients and conductivities are high and when the distance between the two well screens is sufficient. One-well systems are thus favourable options in urban sand-and-gravel aquifers. (C) 2015 Elsevier Ltd. All rights reserved.