The impact of developing a regional multiwell groundwater heat pump system on the geological environment: a case study in Haimen, China

Groundwater heat pump (GWHP) systems are extensively utilized for heating and cooling. However, despite being a well-established technology, their impact on the geological environment is still not thoroughly understood, particularly the potential impacts of regional multiwell GWHP systems. This study analyses the hydrogeological characteristics and geothermal conditions in Haimen, China, to assess the impacts of a regional multiwell GWHP system. A three-dimensional coupled numerical model of groundwater flow and heat transport is established. The numerical model was used to evaluate the geological environment under the maximum energy load. The results indicate that the hydrogeological and geothermal conditions of the study area are suitable for the large-scale development of multiwell GWHP systems. However, the numerical simulations indicate that during system operation, multiwell GWHP systems can cause regional thermal accumulation in aquifers. The simulations showed that thermal accumulation was most significant in the area with the smallest distance between injection and extraction wells, suggesting that small spacing between injection and extraction wells for GWHP systems is not advisable. Therefore, numerical simulations were conducted for different well distances to determine the optimal scheme for the multiwell GWHP systems. The optimization of regional multiwell GWHPs will reduce their impact on the groundwater environment, whilst extracting the maximum geothermal resources available.