Hydrochemical characteristics and circulation depth of geothermal water in coastal area of Tangshan City

The southern coastal area of Tangshan City has abundant and complete geothermal resources, but the development and utilization efficiency of geothermal resources is low. The conventional application of geothermal resources is winter seafood breeding, which is too single and has caused serious resource waste. The geothermal system in the southern coastal area of Tangshan City was set as the research goal, and the water samples were selected to analyze the hydrochemical characteristics of geothermal water and estimate the thermal storage temperature and circulation depth in the study area. The results show that ①The exposed temperature of geothermal water in Binhai area of Tangshan City is 26~86 ℃, belonging to the medium and low temperature. The total dissolved solid (TDS) of the geothermal water is between 482 and 1 644 mg/L, with pH of 8.25~9.15, belonging to the high-salinity and weak-alkaline thermal water, and the chemical type is HCO₃-Na. ② The thermal storage temperature in the study area can be divided into two ranges, about 60~70 ℃ and about 90~100 ℃, respectively, representing two geothermal water circulation systems. The calculated circulation depths are about 1 500~1 800 m and 2 400~2 700 m. The geothermal field in the Binhai area of Tangshan City is geothermal system of medium-low temperature conduction, forming a geothermal system with the Guantao Formation as the main thermal reservoir. And the deep Yanshanian high-temperature granite (HDR) provides a continuous heat source. ③ The hydrothermal geothermal system in the study area has a continuous and stable high temperature heat source, however, it still has characteristics of large circulation depth, far away from the recharge area, making the water alternately circulates slowly. It is suggested that complete specification of geothermal exploration should be established to avoid effects of geothermal tail water on the environment, resource depletion and land subsidence during exploiting clean geothermal resources. This research would deepen the understanding of the thermal geothermal system in the southern coastal area of Tangshan City, and provide certain scientific basis for the development and utilization of regional geothermal resources.