Aquifer heterogeneity and temperature-dependent fluid properties are key controls on heat transport in aquifer thermal energy storage systems, yet their combined influence on performance reliability in low-temperature doublets remains insufficiently quantified. We evaluate a three-dimensional confined-aquifer model using 50 stochastic hydraulic-conductivity realizations, four density–viscosity coupling schemes, and warm-well injection temperatures ranging from 14 to 30 °C, while the cold-well injection temperature is fixed at 6 °C. Performance is assessed using thermal-recovery percentiles, uncertainty range, and a robustness index that integrates mean performance, variability, and a minimum acceptable recovery threshold. Simulations reveal a pronounced asymmetry between the two wells. Warm-well recovery remains relatively stable across the investigated temperature range, whereas cold-well recovery deteriorates strongly with increasing warm-well injection temperature. The 10th-percentile cold-well thermal recovery decreases from approximately 61
The medium-deep U-tube borehole heat exchanger (MDUBHE) extracts geothermal heat via a closed loop without groundwater withdrawal, thereby preserving geothermal resources, with its performance jointly governed by horizontal-section length and operational, geological, and structural parameters. A field test was conducted on an MDUBHE with a 1100 m horizontal section in the Weihe Basin. Circulation test results gave an average outlet water temperature of 21.2 ℃ and an average inlet–outlet temperature difference of 10.8 ℃; the heat extraction rate ranged from 760.4 to 1034.7 kW, governed primarily by circulation flow rate and inlet water temperature. A three-dimensional heat transfer model was developed and validated, with predicted outlet temperature deviation below 6
This study focuses on a building in Xining, Qinghai Province, China. Based on TRNSYS, two heating systems were modeled: a medium-deep borehole heat exchanger (DBHE) heating system and a solar thermal–medium-deep borehole heat exchanger coupled heating system (ST-DBHE). Their heating performance, energy-consumption characteristics, and environmental benefits were comparatively evaluated. The results showed that: (1) For the DBHE system, the average supply and return water temperatures at the geothermal well were 37.62 °C and 36.49 °C, the cumulative heat extraction from the geothermal well was 141,133.48 kWh, the average system COP was 2.30, and the annual energy consumption was 70,299.82 kWh; (2) For the ST-DBHE system, the average supply and return water temperatures at the geothermal well were 38.68 °C and 37.76 °C, the cumulative heat extraction from the geothermal well was 110,756.04 kWh, the cumulative solar thermal recharge was 47,410.96 kWh, the average system COP was 2.26, and the annual energy consumption was 75,992.99 kWh. (3) Compared with the DBHE system, the solar preheating subsystem in the ST-DBHE system increased the COP of the heat pump unit from 3.77 to 3.79, reduced geothermal heat extraction by 21.52
Reinjection is critical for the sustainable utilization of geothermal resources. However, in high-temperature reservoirs, it triggers water–rock interactions that cause formation damage and a severe decline in productivity. This study integrates laboratory experiments and numerical simulations to investigate water–rock interactions during geothermal reinjection and proposes optimized reinjection strategies to mitigate reservoir clogging. A site-specific numerical model of the Yangbajing geothermal field was developed to simulate the evolution of water–rock interactions in the geothermal reservoir under reinjection conditions, supported by high-temperature and high-pressure water–rock reaction experiments. The thermodynamic parameters in the TOUGHREACT simulator were calibrated using the experimental data to improve the accuracy and reliability of the model. The results demonstrated that quartz and feldspar were the dominant minerals undergoing dissolution in the production wells, whereas illite and mica were the primary precipitated phases. Conversely, in the injection wells, mica is the main mineral undergoing dissolution, and quartz, feldspar, and illite constitute the major precipitated phases. These mineral dissolution–precipitation dynamics near geothermal wells induce a 10
