Influence of deep geothermal water exploitation in northern Beijing, China on shallow groundwater behaviors

In northern Beijing, there are the Xiaotangshan and Shahe geothermal fields, which are triangular in plan. They are bounded by the Huangzhuang-Gaoliying fault on the east, by the Nankou-Sunhe fault on the west and by the Asuwei-Xiaotangshan fault on the north. The thermal reservoirs are karst fissure aquifers in the Wumishan and Tieling formations of the Jixian System and Cambrian-Ordovician carbonate rocks. The cover rocks of these thermal reservoirs are impermeable layers consisting of Qingbaikouan shale, Carboniferous-Permian sandstone-shale and Jurassic volcanic rocks. The H and O isotopic compositions of meteoric water, shallow cold groundwater and deep geothermal water in the main fall on the Craig precipitation line in the area, indicating that shallow cold groundwater and deep geothermal water were derived from meteoric water. The 3H values in geothermal water are higher in the north and lower in the south, indicating that both the geothermal water and shallow cold groundwater flow from north to south. The study focuses on the influence of deep geothermal water production on shallow groundwater behaviors in shallow earthquake observation wells and the differences of such influence in respect to hydrogeological conditions, distances from exploited geothermal wells and different observation items. Results show that the distance of influence of deep geothermal water exploitation on shallow cold groundwater behaviors is about 5 km in the northern Beijing geothermal system, and that the influence on the observation wells located near water-transmitting faults is most pronounced.