Determine relative and saturation-dependent (effective) permeability for different saturations. The pore morphology method can be used to determine the distribution of the phases (then it is assumed to be stationary) or saturation results of a previously simulated wetting process can be used.

The saturation-dependent or effective permeability is the permeability at given saturation levels (), whereas the absolute permeability is given as the permeability of the completely saturated medium ( ). The permeability is 0 at saturation 0 ().

To calculate the permeability of the wetting phase, the non-wetting phase is treated as an unmovable obstacle and the flow calculation treats it as a solid.

To calculate the permeability of the non-wetting phase, the wetting phase is treated as an unmovable obstacle and the flow calculation treats it as a solid.

Thus, flow only takes place in the pores filled with the corresponding fluid, whereas the other pores are ignored. Specifically, no movement of bubbles is simulated. The permeability values are then determined as described in the Flow permeability section of the FlowDict handbook. To determine the whole curve or , it is necessary to calculate the permeability for several different saturations.

The Relative permeability is a dimensionless measure, defined as the ratio of the saturation-dependent permeability to the absolute permeability. The relative permeability must lie between zero and one:

where is the saturation-dependent permeability and is the absolute permeability.