Abstract: The geothermal development level of Xian County's geothermal field is relatively high, providing data support for the fine construction of geothermal field models and evaluation of geothermal resources. The geothermal field in Xian County belongs to the Xian County Uplift in the Bohai Bay Basin, with the Fucheng Depression to the east and the Raoyang Depression to the west. The main thermal reservoirs developed in the research area are porous sandstone thermal reservoirs and karst limestone thermal reservoirs. This article takes the Wumishan Formation limestone thermal reservoir of the Jixian system as the research object, and uses a multi-scale discrete fracture three-dimensional fine geological modeling method to evaluate the geothermal resources of the Xian County geothermal field. The geological structure model of the geothermal field in Xian County was constructed using deterministic and stochastic modeling methods. The model grid was set with a step size of 25 m × 25 m, and 300 simulation layers were used vertically, with a single layer thickness of 1 m. The total number of grids was determined to be 23.3306 million. Under the constraints of the secondary interpretation results of well logging, a geological model of the Wumishan Formation lithology, physical properties, and temperature field was established. Through the analysis of the above model, the distribution trend of thermal storage resources in the Xianxian geothermal field showed a certain positive correlation with the structural morphology of the Xianxian uplift, that is the shallower the burial depth, the better the geothermal resource conditions. The model was compared and verified with existing well completion parameter data, and it was found that the model had good adaptability. And the volume method based on the fine thermal storage geological model was selected to evaluate the geothermal resources in the region. The results showed that the total thermal storage of the Wumishan Formation in the Jixian geothermal field of Xian County was 2.881 × 10¹⁶ kJ, equivalent to 9.841 × 10⁸ tons of standard coal, and the total recoverable heat was 0.432 × 10¹⁶ kJ. The hot water volume is 35.75 × 10⁸m³, and the heat content in the hot water is 0.105 × 10¹⁶ kJ, equivalent to 0.359 × 10⁸t of standard coal, which proves the huge potential of geothermal resources in the Xian County geothermal field. This model provides technical support and basis for the next development of the Xian County geothermal field.

Key words: multi scale discrete fracture, geological modeling, Xian County geothermal Field geothermal resources assessment