Which term describes the phenomenon where the relative permeability depends on saturation history?

Which term describes the phenomenon where the relative permeability depends on saturation history?

• A. Capillary Pressure
• B. Wettability
• C. Hysteresis
• D. Relative Permeability

Answer: (C)

Hysteresis is the dependence of relative permeability on the saturation history. In two-phase flow through a porous medium, the pathways and connectivity of the wetting and non-wetting phases change depending on whether you’re draining (removing one phase) or imbibing (adding it back). Even at the same water saturation, the network of connected pores for each phase can be different after drainage than after imbibition, so the effective permeabilities you measure are different. This creates a loop-like behavior in the relative permeability versus saturation curves rather than a single unique curve. Capillary pressure can also show history effects, and wettability influences the shapes of the curves, but the specific phenomenon described—relative permeability changing with the path to reach a given saturation—is hysteresis.

Hysteresis is the dependence of relative permeability on the saturation history. In two-phase flow through a porous medium, the pathways and connectivity of the wetting and non-wetting phases change depending on whether you’re draining (removing one phase) or imbibing (adding it back). Even at the same water saturation, the network of connected pores for each phase can be different after drainage than after imbibition, so the effective permeabilities you measure are different. This creates a loop-like behavior in the relative permeability versus saturation curves rather than a single unique curve.

Capillary pressure can also show history effects, and wettability influences the shapes of the curves, but the specific phenomenon described—relative permeability changing with the path to reach a given saturation—is hysteresis.