Geothermal water chemical characteristics and scaling analysis of Xianshuihe fault zone

Geothermal resources have great potential as clean energy, and can be used to achieve the goal of carbon peaking and carbon neutrality. The Xianshuihe fault zone in western Sichuan is rich in geothermal resources, but geothermal scaling has become one of the main problems in the development and utilization of geothermal resources. In order to further identify the occurrence state and scaling trend characteristics of geothermal resources, this paper takes the six areas of Moxi, Yulingong, Erdaoqiao, Zhonggu, Bamei and Daofu on the Xianshuihe fault zone as the research area, and uses water chemistry analysis, hydrogen and oxygen isotopes, heat storage temperature estimation and scaling trend characteristics analysis to carry out the geothermal water hydrochemistry and scaling trend characteristics of the Xianshuihe fault zone. The results show that the hydrochemical types of geothermal water are mainly Na-HCO₃, Ca-HCO₃, Ca·Na-HCO₃ and Na-Cl·HCO₃; Geothermal water mainly comes from the supply of atmospheric precipitation and oxygen drift occurs in most areas; The geothermal water has not reached the complete water-rock equilibrium state, and the shallow geothermal reservoir temperature is 61℃～172℃. The average temperature of deep thermal reservoir is 183℃ to 283℃, and the average cold water mixing ratio is 77% to 86%; The exponential analysis method and the saturation index discrimination method show that carbonate scaling may occur in the all above geothermal areas. Silicate scaling may only occur in several areas with abnormally high SiO₂ content, while sulfate scaling almost does not occur. According to the cold water mixing ratio estimated by the silicon-enthalpy model, the fluid composition of the deep reservoir is reconstructed. Combined with the formula, it is calculated that the carbonate scaling degree in the Erdaoqiao area is the most serious, mainly because the reservoir lithology in the area is carbonate salt, and the reservoir temperature can promote the precipitation of CaCO₃. For descaling and prevention, mechanical removal, control of CO₂ partial pressure, control of solution pH, and use of chemical additives (scale inhibitors) can be used. The research results can provide a theoretical basis for the sustainable development and utilization of geothermal resources in the Xianshuihe fault zone and western Sichuan.