Key Takeaways & Executive Findings
- •• Mining-induced stress creates interlaced high-aperture and low-aperture fracture zones below the goaf. • The combined effect of high- and low-aperture fractures restricts the effective flow channel length/density of the fracture network. • Contraction of the flow field leads to a significant decline in production flow rate and power as mining distance increases. • The study provides a theoretical foundation for the co-development of coal and geothermal resources.
Abstract
Developing hydrothermal resources in highly conductive karst aquifers at deep mine floors is regarded as a potential approach to achieving the co-development of coal and geothermal resources. However, the heat transfer potential of the fracture system in the target reservoir under mining activities remains in suspense. Hence, a coupled thermal–hydraulic-mechanical model was developed for the karst reservoir of Anju coal mine in China, considering non-isothermal convective heat transfer in fractures. This model examined the influence of stress redistribution due to different mining distances (MD) on the effective flow channel length/density and the high/low-aperture fracture distribution. The dynamic heat generation characteristics of the geothermal reservoir were evaluated. Key findings include: Mining-induced stress creates interlaced high-aperture and low-aperture fracture zones below the goaf. Within these interlaced zones, the combined effect of high- and low-aperture fractures restricts the effective flow channel length/density of the fracture network. This contraction of the flow field leads to a significant decline in production flow rate, which consequently reduces both the production flow rate and power as MD increases. This work represents the study of mining disturbances on geothermal production, providing a theoretical foundation for the co-development of coal and geothermal resources.
1. Introduction
Hydrothermal resources have gained global attention due to their widespread availability and direct usability [1–3]. The karst limestone reservoir, typically buried at depths larger than 1000 m, is an important source of hydrothermal resources [4,5]. Characterized by a natural fracture network due to faults and fractures of varying scale, this reservoir also serves as a key aquifer near coal-bearing strata [6,7]. Consequently, karst limestone reservoirs hold significant potential for renewable energy development owing to their high temperature and high permeability [8,9]. However, the prohibitive drilling costs of directly harnessing these deep geothermal resources from the surface remain a major barrier.
Developing geothermal energy from the karst limestone reservoir at mine levels represents one of the most promising methods for utilizing the aquifer’s source [10]. As shown in Fig. 1, constructing geothermal wells based on existing mine levels can significantly reduce development costs. Additionally, utilizing the thermal energy within the reservoir helps regulate the temperature of the surrounding rock, thereby improving miners’ working conditions [11]. However, during the co-development of coal and geothermal energy, mining activities can adversely affect the flow and heat transfer efficiency (FHTE) of karst reservoirs and the geothermal production performance. Currently, research on FHTE within this reservoir under mining-induced stress is lacking. Further studies are essential to advance the co-development of coal and geothermal resources.
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Jinghong Yan, Dan Ma, Xuefeng Gao, Hongyu Duan, Qiang Li, Wentao Hou (2025). Geothermal energy production potential of karst geothermal reservoir considering mining-induced stress. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.06.003
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Frequently Asked Questions
What is the main objective of the study?
The study aims to evaluate the geothermal energy production potential of a karst geothermal reservoir under mining-induced stress, focusing on the influence of stress redistribution on fracture networks and heat transfer efficiency.
How does mining-induced stress affect the geothermal reservoir?
Mining-induced stress creates interlaced high-aperture and low-aperture fracture zones below the goaf, which restricts the effective flow channel length/density, leading to a decline in production flow rate and power as mining distance increases.
What model was developed in this research?
A coupled thermal-hydraulic-mechanical (THM) model was developed for the karst reservoir of Anju coal mine in China, considering non-isothermal convective heat transfer in fractures.
What are the key findings of the study?
Key findings include that mining-induced stress creates interlaced fracture zones, which restrict flow channels and reduce production flow rate and power with increasing mining distance, providing a theoretical basis for co-development of coal and geothermal resources.
Why is the co-development of coal and geothermal resources important?
Co-development reduces drilling costs by utilizing existing mine infrastructure and helps regulate surrounding rock temperature, improving working conditions, while also contributing to renewable energy development.
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