Geochemical Characteristics, Thermal Reservoir Environment, and Comprehensive Resource Utilization Evaluation of Deep Geothermal Water in Dongying City.

Dongying City has abundant geothermal resources. Understanding the hydrochemical characteristics and reservoir environment of geothermal water from a hydrogeochemical perspective is crucial for rational development and utilization. In this study, a total of 30 deep geothermal water samples were collected from the Guantao (GT), Dongying (DY), Shahejie (SHJ), and Ordovician (O) formations. Through hydrochemical analysis and isotopic tracing, the hydrochemical characteristics, thermal reservoir temperature, and circulation depth were systematically investigated. A conceptual model for the genesis of the geothermal resources was established, and a multidimensional evaluation of the geothermal water quality was conducted. The deep geothermal water is weakly alkaline, brackish to saline, with a hydrochemical type mainly of Cl-Na. Ionic ratios indicate that mineral dissolution and cation exchange primarily control its chemical composition. Isotopic analysis reveals ages from 28,180 to over 43,500 years, representing confined paleowater. Reservoir temperatures range from 69.49°C to 114.01°C (average 91.10°C), and circulation depths from 1696.49 to 3045.58 m (average 2351.33 m). Trace elements including F, Br, Li, I, and B reach therapeutic thresholds and pose no health risk. However, the water has high corrosion and scaling potential, requiring pipeline protection. The findings provide valuable insights for understanding the genetic mechanisms of similar geothermal systems and for the diversified, rational development and efficient utilization of geothermal resources.