There are many variations in methods for measuring relative permeabilities. Usually, a cylindrical porous sample is mounted in a holder. The cylindrical surfaces of the sample are sealed to prevent flow. Fluids are injected and produced from the sample through ports at each end. By accurate measuring of Inject and collect fluids and also input and output pressures and by using related methods, relative permeability can be determined.
- Steady-state methods: In steady-state methods, both phases (oil and water, gas and oil, or gas and water) are injected simultaneously at constant rates. Injection continues until a steady state is reached, as indicated by constant pressure drop and constant saturations.
- Unsteady-state methods: In unsteady-state methods, just one phase is injected at either a constant flow rate or a constant pressure drop. Throughout the injection, the pressure drop and production of phases are measured.