Optimization design of geothermal field development schemes based on hydraulic, thermal and chemical coupled numerical simulation: a case study of karst thermal reservoir in Xiong'an New Area, Hebei Province

For the optimization design of geothermal resource development schemes in karst thermal reservoirs of the Xiong'an New Area, Hebei Province, a hydraulic, thermal and chemical multi-field coupled numerical simulation was conducted on the geothermal field's extraction status based on a three-dimensional geological model. The influence of key parameters such as extraction duration, extraction and recharge flow rates, well spacing, recharge temperature, and recharge rate on the effectiveness of geothermal field development was discussed using sensitivity analysis. The results showed that the extension of the extraction time of geothermal wells led to temperature decline and thermal breakthrough. In the current development scenario, the temperature of some geothermal wells in Xiongxian and Rongcheng areas could decrease by up to 4 ℃ over a 100-year extraction cycle. Reducing extraction flow rates and increasing well spacing could effectively delay thermal breakthrough and ensure the longevity of geothermal fields. In Xiongxian area, it was recommended that the well spacing should be kept from 500 to 600 m. The recharge temperature had little effect on the overall temperature field of the geothermal field, but reducing the recharge temperature could improve thermal utilization. The recharge rate had a significant impact on groundwater levels. A 100% recharge rate could maintain water level stability, while a 90% recharge rate could lead to a continuous decline in groundwater levels. In general, reasonable adjustment of the extraction cycle, extraction and recharge flow rates, well spacing, and recharge strategy can effectively extend the service life of geothermal fields and improve resource utilization efficiency.