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This article presents an effective method for improving the structure and performance of coal rock masses, thereby facilitating coalbed methane extraction—the grouting solidification technique. A systematic review is conducted on grouting solidification materials, process methods, evaluation techniques, and other related aspects. In conclusion, it is emphasized that the grouting solidification technique requires further refinement in its system, and its continued significance in the dynamically evolving energy and coal industry is underscored. This is crucial for ensuring the efficient development and sustainable utilization of coal and coalbed methane resources.

To enhance the surface insulation properties of SiO2/epoxy resin composites, the SiO2 filler is co-modified with a chemical method and dielectric barrier discharge plasma in this work. The effects on the micro-structures, electrical parameters and surface insulation properties of the materials are studied. The results show that chemical modification using the silane coupling agent (KH550) can effectively introduce organo-functional groups into SiO2 filler. On the other hand, plasma modification shows little effect on the organo-functional group but significantly increases the dispersity of the nanoparticles, therefore reducing filler conglobation in epoxy resin composite. The composite samples with SiO2 doping concentration of 1 wt.%, 2 wt.%, 3 wt.%, 5 wt.% and 7 wt.% are prepared and characterized. It is found that the synergy of chemical and plasma methods could significantly improve the surface insulation of composite samples. Through doping 2 wt.% of the co-modified SiO2 filler, the direct current flashover voltage of the composites in dry air at atmospheric pressure can be increased to 1.53 times of the pure epoxy. The enhanced surface insulation properties are explained by the trap effect and the change of electrical parameters through the co-modification process. [ABSTRACT FROM AUTHOR]

In order to improve the proppant displacement in the fracture and enhance the fracturing stimulation effect, the experiment on proppant carrying capacity of fracturing fluid was conducted with experimental simulation method and visual-panel fracture device, the formation of in-fracture sand bank was characterized in combination with the microscopic movement trajectory of the proppant particles and the macroscopic shape of sand bank, the difference in sand carrying modes was analyzed between of viscous and non - viscous fracturing fluids, and the effects on the displacement pattern of sand dike was studies in terms of fracture inter-perforation disturbance, fracturing fluid displacement, fracturing fluid viscosity and construction sand ratio. The results indicated that the prop-pant in fractures migrated under the joint action of fluidization and sedimentation, mainly dragged and transported under the action of fluidization; an immobile thin layer of fluid was formed between the fluidized layer and sand bank in viscous fracturing fluid to support the particles, reducing the friction and collision between the fluid and the particles; the formation of the sand bank includes four stages, that is, sand bank formation, development, balancing and piston-like forwarding, the formed sand bank could be characterized by accumulating angle, balancing height and advancing angle under the joint effect of perforation disturbance and fluid erosion, and there were no sand zones in the fractures near the wellbore and in the direction of fracture height; the balancing height of the sand bank mainly depended on the movement speed of proppant particles, inversely proportional to the construction displacement and the fracturing fluid viscosity and directly proportional to the sand ratio. This study provides a reference for the optimization of fracturing operation parameters. [ABSTRACT FROM AUTHOR]