A multi-field coupled fractal model for shale gas extraction considering water reflux and microstructure evolution

This study aims to optimize gas production in shale reservoirs by investigating the impact of hydraulic fracturing and two-phase gas-water flow within fracture-induced zones. A multi-domain, multi-phase fractal model was developed, incorporating fractal dimensions to represent the microstructure of shale reservoirs, which consist primarily of kerogen, inorganic matrix, and fractures. Key parameters, including fracture-induced zone width, maximum water relative permeability, and hydraulic fracture aperture, were analyzed for their effects on gas output and microstructure evolution. Results indicate that moderate hydraulic fracturing improves gas production, while excessive water reflux outside the optimal range diminishes output. Additionally, increased water relative permeability and hydraulic fracture aperture promote fracture and pore development, while lowering the entry pressure of the non-wetting phase facilitates matrix pore growth.