Characteristics analysis of the geothermal water in Heshan Coalfield based on hydrogeochemistry

In order to develop geothermal water resources in Heshan Coalfield, Guangxi Provence, the temperature of geothermal reservoir was estimated by quartz temperature scale method based on hydrogeochemistry, and the circulation depth of geothermal water was speculated to study the occurrence law of geothermal water. The results show that the recharge, runoff and discharge of underground hot water in Heshan Coalfield are controlled by karst structure, which is mainly along and across the stratum. It receives infiltration recharge from atmospheric precipitation and the water quality is HCO₃-Ca·Mg type. By quartz geothermometers without steam loss, the thermal reservoir temperature is estimated to be about 80℃ and three types of water, namely, shallow groundwater, mixed water of shallow groundwater and deep groundwater circulating water and deep groundwater circulating water. Taking No.6 borehole data in the mine field as an example, the temperature of the thermal reservoir is 63.44℃ to 79.41℃, and the circulation depth is 2 541-2 704 m. The difference between the thermal reservoir temperature and the actual buried depth is small and the estimation result is highly reliable. The difference from the actual burial depth is small, indicating the high reliability of the estimation results. At the depth of 1 400 m and around, it is expected to explore geothermal water about 50℃. The metasilicic acid and temperature of underground hot water in Heshan coal field meet the medical requirements. No.3 and No.4 coal seams have low thermal conductivity and small porosity, which are good caprock for thermal reservoir. The lower member of Heshan Formation and Maokou Formation in the floor of No.4 coal seam are developed with solution fissures, which are good hot water reservoirs. The research results have certain exploration significance for the development and utilization prospect prediction of geothermal resources in coalfields.