Permeability and the Poro-Perm Transform

From Porosity to Permeability

Permeability matters most for flow yet is measured at the fewest points, so it is usually derived from the modeled porosity through a poro-perm transform. The transform is log-linear: the logarithm of permeability rises in proportion to porosity, because permeability ranges over orders of magnitude where porosity ranges over only a few percent.

A Cloud, Not a Line

The poro-perm relationship measured on core is a scatter cloud, not a clean line: at one porosity, permeability can vary tenfold, because pore geometry and not just pore volume sets flow. A good model carries that scatter, often by cosimulating permeability with porosity rather than applying a single deterministic curve.

Why the Scatter Matters

The scatter is not a nuisance to average away. The high-permeability tail, the streaks and thief zones, dominates flow and recovery, and those highs are exactly where the poro-perm scatter is largest. Carrying the scatter, and its uncertainty, is what lets the model capture the connected high-permeability pathways that decide how the reservoir produces.