Determine Relative and Saturation-dependent (Effective) Permeability for different fluid 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 ().

The Effective Permeability can be calculated for the invading fluid or the displaced fluid. In both cases, the unconsidered fluid 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, while the other pores are ignored. Specifically, no movement of bubbles is simulated. To determine the whole effective permeability curve, it is necessary to select several different saturations and both invading and displaced fluid for the computation. After the computation, in a post-processing step, you can calculate an LET fit or a Corey fit for the effective permeability curves.

The permeability values are then determined as described in the Flow permeability section of the FlowDict chapter. Similar as in FlowDict, a volume field containing velocity and pressure values at each voxel is saved for each saturation step.

The Relative Permeability is a dimensionless measure, defined as the ratio of the Saturation-dependent Permeability () to the Absolute Permeability (). The relative permeability thus lies between zero and one: