High-strength electric detonation (HEED) is a new type of permeability enhancement technology for physical coal seams. This study elaborates the technical principles and scientific connotation of HEED: "the precise control and directional release" of physical energy. We compared HEED with major permeability enhancement technologies of coal seams to highlight its technological advantages: precise energy control, ultra-low water consumption, and environmental friendliness. We then reviewed its development history and summarized the three-stage propagation of shock waves generated by the electro-hydraulic effect and their fracturing patterns on coal and rock. The performance and applicability of HEED under complex geological conditions were verified through representative engineering cases. This study also identified limitations in the engineering applications of HEED and its future research directions in fundamental theory, equipment series, technical processes, engineering applications and technological synergy, offering theoretical references for its standardization, engineering application and promotion.

As a natural porous medium, coal has strong heterogeneity in its microstructure. To further study the differences in microstructure and mechanical properties of different coal bodies, four coal samples with different geological conditions in different mining areas were selected. Atomic force microscopy (AFM) with built-in PF-QNM mode was used to scan the micro surfaces of different coal samples. The results showed that there were significant differences in the micro morphology and mechanical properties between different coal samples. As the degree of metamorphism increased, the number of peaks on the micro surface of coal increased, providing more adsorption sites for gas adsorption. The average modulus of coal increases linearly with the degree of metamorphism. The surface adhesion force of coal shows an inverted U-shaped distribution with the degree of metamorphism, and the average surface adhesion force of medium rank coal is relatively high. The increase in micro surface roughness will increase the actual contact area between coal samples and substances, leading to an increase in adhesion force, while the generation of cracks will increase roughness but reduce micro surface adhesion force.

CO₂ sequestration in coal seams represents an effective strategy for mitigating CO₂ emissions. However, the complicated interaction of CO₂-water-coal at the micro-scale may compromise the structural integrity and mechanical strength of coal, thereby adversely impacting the efficacy and safety of CO₂ sequestration in coal seams. This study introduces a novel indentation testing method that reveals the scale-dependent evolution mechanisms of coal microstructures, enabling the accurate and reliable quantification level of degradation in the micromechanical properties caused by supercritical CO₂-water-coal interactions. Using this method, the extent of mechanical degradation in three types of coal microstructures could be accurately evaluated under supercritical CO₂-water-coal interaction. The pure organic matrix exhibited remarkable stability under all fluid treatments, with minor changes in microstructure feature and a mechanical property reduction of less than 25%. In contrast, the mineral structures were significantly altered by treatment with fluid mixed with supercritical CO₂ and brine, with erosion depths and mechanical property reductions reaching 1.6 µm and 80% in granular structures, and 6.4 µm and 90% in banded structures. However, in the absence of brine or supercritical CO₂, the erosion depths and mechanical property reductions of fusinite were limited.