Calculate saturation-dependent (relative) gas diffusivity using the pore morphology method or results of a previously simulated drainage or imbibition process. SatuDict calculates the saturation-dependent diffusivity as in DiffuDict. It is assumed that there is no diffusion from the gas phase into the liquid phase and no transport of the gas within the liquid phase (no-flux boundary conditions). It is also assumed that Knudsen diffusion can be neglected. The saturation-dependent gas diffusion can be calculated for successive saturations based on the gas/liquid phase distributions from the simulated drainage.