Hi Samad, Thanks for a good question. I can understand your dilemma. But the solution is simple. First of all we do not use air permeability in a simulation model. We use Klinkenberg permeability which is the air permeability in when the mean pressure is mathematically infinite. At infinite pressure air or any gas would behave like liquid, hence this Klinkenberg permeability is equal to liquid permeability i.e. oil or water at 100% saturation. In other words Koil(100% oil saturation) is equal to Kwater(100% water saturation). This is also equal to Klinkenberg air permeability. Hence in the simulation model if the above concept is used there is nothing like model is inconsistent. Now the question may arise in your mind then why the hell laboratory carry out the air permeability measurement not the oil or water absolute perm measurement? The reason is air permeability measurement is cheaper and faster than if we use oil or water.
As a guideline you must convert the air permeability into Klinkenberg permeability at envisaged stress.