Xinghui Wu, Peng Li, Shengjun Miao, Meifeng Cai, Yan Liu, Min Wang, Wensai Xiong
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Multi-field Coupling Mechanism and Optimization of Heat Transfer in Deep Carbonate Geothermal Reservoirs Based on Acid Fracturing Modification
Efficient development of deep carbonate thermal reservoirs is crucial for geothermal resource utilization, but their low permeability and long-term thermal decay problems seriously limit their capacity. Taking the D22 well in Xiongan New Area as an example, we constructed a multi-field coupled Thermo-Hydro-Mechanical-Chemical (THMC) numerical model. We revealed the heat exchange mechanism and heat attenuation law of the reservoir after acid fracturing and reforming. The study shows that increasing the acid fracture opening from 0.08 m to 0.12 m increases permeability by 35% and heat exchange efficiency by 20%, but the increase in opening accelerates the cold front advance and leads to fracture closure. The main control parameters of fracture opening, well distance, and injection flow rate were identified, and the "stepped dynamic flow rate control method" was proposed to adjust the flow rate in steps (200→160→120 m3/h), which reduced the temperature decay rate by 42% and increased the cumulative heat extraction by 18%. Further design of a 10-12 mm nano-aerogel wellbore thermal barrier coating reduces heat loss by 15% and extends system life by 2-3 years after synergistic optimization. For large-scale reservoir development, "medium reservoir size (3-4 km2) periodic acid recharge" is proposed to suppress the diminishing marginal benefits.
期刊介绍:
Case Studies in Thermal Engineering provides a forum for the rapid publication of short, structured Case Studies in Thermal Engineering and related Short Communications. It provides an essential compendium of case studies for researchers and practitioners in the field of thermal engineering and others who are interested in aspects of thermal engineering cases that could affect other engineering processes. The journal not only publishes new and novel case studies, but also provides a forum for the publication of high quality descriptions of classic thermal engineering problems. The scope of the journal includes case studies of thermal engineering problems in components, devices and systems using existing experimental and numerical techniques in the areas of mechanical, aerospace, chemical, medical, thermal management for electronics, heat exchangers, regeneration, solar thermal energy, thermal storage, building energy conservation, and power generation. Case studies of thermal problems in other areas will also be considered.