Effect of well pair distance of ground water heat pump on the changes of geo-temperature field due to aquifer energy extraction

The distance between production and injection wells is a key parameter for the design of energy abstraction system. According to the heat exchange process in the aquifer of ground water heat pump, a mathematical model of groundwater heat transfer has been established. Based on the model, numerical simulation in typical fine sand confined aquifer with constant groundwater flow is presented for the changes of geo-temperature filed due to energy extraction with 6 various well distance. Quantitative relationship between the pumping temperature changes in the last phase of operation and the well pair distances is presented, and simulation result of evolvement of geo-temperature field with different operation modes is got. The simulation results show that in order to avoid thermal breakthrough, the well pair distance should be no less than 80m; seasonal alternating use will take advantage of the storage of aquifer and improve the efficiency of GWHP air-conditioning system.