A void space network is presented for the simulation of mercury intrusion and the calculation of the absolute permeability of porous media. Mercury intrusion is simulated by the Laplace/Washburn equation within a percolation algorithm. A ’Dinic’ operational research network analysis algorithm gives the maximal flow capacity of the unit cell. A combination of the Darcy and Poiseuille equations of flow is then used to derive the absolute gas permeability of the simulated structure. Mercury intrusion curves and permeabilities are calculated for networks with banding, clustering of small pores and throats, or clustering of large pores and throats. The modelling method is then applied to banded sandstone samples with edge corrections, and it is shown that the constraint of fitting to experimental mercury intrusion data suppresses the permeability differences induced by structural changes alone. The same networks can model mercury hysteresis, porosity, connectivity, pore/throat size correlation, tortuosity and other properties, and can be applied to any consolidated porous medium.