Hydraulic fracturing: Prioritizing matrix pore–fracture contact area over aperture—A pore scale perspective

Hydraulic fracturing is commonly employed to create a fracture network and enhance hydrocarbon recovery in subsurface reservoirs. Traditional understanding suggests that the stress-induced reduction in fracture aperture results in a decline in production rate, as predicted by Darcy's law. However, Darcy's law is based on open-boundary conditions, whereas post-fracturing hydrocarbon production typically occurs in a semi-sealed system. Our previous research demonstrates that gas flow in such a system follows the damped wave equation. This raises the question of whether a large fracture aperture is truly critical for hydraulic fracturing design and production forecasting. To investigate this, we develop a matrix–fracture network model and simulate matrix–fracture gas flow using the damped wave equation. Sensitivity analyses at varying fracture apertures and matrix pore–fracture contact areas reveal that fracture aperture does not affect the matrix mass depletion rate. In contrast, a reduction in the matrix pore–fracture contact area significantly lowers the matrix mass depletion rate. We conclude that the primary factor controlling production rate decline is the decrease in matrix pore–fracture contact area during the production process, which can result from fracture surface roughness and cementation as the fracture aperture decreases. Therefore, the conventional view that “decreasing fracture permeability lowers productivity” is incorrect.