Assessment of geothermal water environment using multi-influencing factor analysis method: A case study of Reshuiwei geothermal field

Abstract

Geothermal water environment assessment is crucial to the utilization. Reshuiwei geothermal field has more resources than others in Hunan province. However, existing methods has some problems such as complicated analysis, need much data and/or rely more on geographic information system (GIS). Due to research limitations, data is insufficient. Thus, using existing methods in this study is challenging. Therefore, we develop ‘multi-influencing factor analysis’ method to assess this geothermal water environment. The ‘multi-influencing factor’ including gas composition, physiochemical characteristics, variations of essential ions and indicators, corrosion and scaling possibilities of geothermal water. The methodology is: First, the original data are gathered by shallow drilling and gas sampling equipment. Second, data is initially analyzed by cooperative departments. Finally, using proposed method, we empirically evaluate the geothermal water environment by considering outcomes of 4 elements. Results show that gas of geothermal water is mainly composed of O₂ and N₂. Small contents of H₂S are spotted. Geothermal water is depleted in Mg²⁺, Cl⁻, enriched in Na⁺, ${\text{HCO}}_3^{-}$, SiO₂. Special substances such as ${\text{SiO}}_3^{2-}$ and F⁻ are also spotted. Due to potential negative impacts of O₂, H₂S, SiO₂, ${\text{SiO}}_3^{2-}$ and F⁻ on geothermal water environment, they must be considered in future. The main ions and indicators of geothermal water show stable variations. Geothermal water exhibits low corrosion, reduced scale formation and is less likely to develop calcium carbonate scale. The geothermal water environment is stable and less erosive, which is beneficial for utilization. Geothermal resource exploitation would benefit from the proposed approach and results.