Hydrochemical Processes, Mineral Scaling and Water Quality of Geothermal Waters in Sichuan Basin, Southwestern China

Geothermal resources are significant natural resources for achieving carbon neutrality. In this study, we collected eight groups of geothermal water samples from a Sichuan sedimentary basin. Major and trace elements were measured for hydrochemical analysis. SO42- and Ca2+ are the major anion and cation, respectively, in geothermal waters with the hydrochemical type Ca-SO4. The dissolution of calcite and gypsum, silicate weathering and positive cation exchange were responsible for hydrochemical processes. Saturation indices showed the unsaturated affinity of geothermal waters. Carbonate scaling would be the main problem during geothermal exploitation. The water quality index indicated that most of the geothermal water samples, except G3 and G8, were suitable for drinking purposes. The poor water quality of the G3 and G8 samples was attributed to elevated Na+ and K+ concentrations. The weights of affecting factors followed the order of NH4+ (3.803) > Cl- (2.823) > Na+ (2.677) > pH (2.224) > Ca2+ (1.506) > SO42- (1.169) > F- (1.127) > Mg2+ (0.850) > TDS (0.808). The results of this study provide an important insight for geothermal exploitation in sedimentary basins worldwide.