Comparison of calculated a) k from Equations (1–4), b) F from Equations (2, 5) and c) k from Equations (3, 6) to the observed values of permeability and formation factor in the Fontainebleau sandstone. The meaning of the different symbols is explained in the inset, where k(z) refers to Bernabé et al. Equation (4), F(z) to Equation (5) and k(F) to Equation (6) and where the digits 1 and 2 indicate the Fontainebleau 1 and 2 datasets. The difference between the two datasets is particularly visible in the diagrams b) and c). The vertical error bars (dark purple) represent minimal estimates of the δk/k and δF/F model tolerances (i.e., δk/k ≈ ±40% and δF/F ≈ ±10% for the PWB model; δk/k ≈ ±60% and δF/F ≈ ±20% for the Bernabé et al. model in high porosity samples and δk/k ≈ ±90% and δF/F ≈ ±30% in low porosity samples).