Model the Properties

Porosity Within Each Facies

With the facies in place, model the porosity separately inside each one, high in the clean sand and low in the shale. Pooling them into one field would put the mean in the empty valley between two populations, a porosity no real rock has.

Permeability From Porosity

Permeability matters most for flow yet is measured at the fewest points, so it is derived from the modeled porosity through the poro-perm transform. The transform is log-linear because permeability ranges over orders of magnitude where porosity ranges over only a few percent. Color by permeability and the contrast is stark: the sand flows, the shale barely does.

The Static Model Is Done

Facies, porosity, and permeability on a faithful grid: that is the static model, the rock as it sits today. Coarsen the grid and watch the property detail average away, a preview of the upscaling to come. The remaining stages take this static model, sum its volumes, ready it for flow, and run it.