Relationship between macro-fracture density, P-wave velocity, and permeability of coal

• P-wave velocities, fracture densities, porosity, and permeability of four coal samples from North China were analysed.
• A relationship exists between P-wave velocity and permeability of the samples.
• Overall, P-wave velocities decrease with increasing fracture density.
• Different coal ranks show differences in the relationship between P-wave velocity and permeability.

This study was undertaken to determine the quantitative relationship between macro-fracture density, P-wave velocity, porosity and permeability of different coal rank samples from mining areas in North China. The coal sample permeability shows an exponential growth with increasing fracture density. The relation between P-wave velocity and porosity is power function and P-wave velocity decreases with the increasing porosity. P-wave velocity linearly or nonlinearly decreases with the increase of fracture density in the selected coal samples (0.73–3.59% Ro). However, the overall trend is that P-wave velocity decreases with an increase in macro-fracture density. The permeability of coal samples linearly decreases with the increase of P-wave velocity. The quantitative relationship between P-wave velocity and permeability could provide reference for the further study of permeability predicting.