Multi-hole synchronous linkage control fracturing in low permeability coal seams based on three-dimensional lattice method

The multi-hole synchronous hydraulic fracturing in low permeability coal seams exhibits considerable variability under varying geological and technical conditions, leading to an anti-reflection effect of fracturing that is significantly lower than anticipated. To explore the mechanism of stress interference between fractures in multi-hole synchronous fracturing and the distribution mechanism of multi-hole flow competition under linkage control, the multi-hole linkage controlled synchronous hydraulic fracturing model is developed by using the three-dimensional discrete lattice method, and the process of competitive fracture growth is examined under single-hole, double-control, and four-hole fracturing conditions. The findings indicate that the observation hole exacerbates the reservoir's heterogeneity and causes the uneven expansion of hydraulic fractures. The distribution of in situ stress and the viscosity of fracturing fluid significantly influence the fracture propagation mode and fluid velocity during two-hole fracturing. Under elevated stress differentials, the fracture tends to coalesce, but under diminished stress differentials, the fracture remains comparatively autonomous. The application of high-viscosity fracturing fluid can efficiently facilitate the uniform expansion of fractures. While fractures may converge at varying injection rates, excessive injection rates will exacerbate fracture disequilibrium. The four-hole linkage control synchronous hydraulic fracturing enhances the connectedness of four-hole fractures and significantly increases the gas permeability of the coal seam through the regulation of the linkage approach. The research findings establish a theoretical foundation for synchronous hydraulic fracturing governed by multi-hole interconnection.