How is the relative permeability of gas calculated?

How is the relative permeability of gas calculated?

• A. Krw=kw/k
• B. Krw=k/kw
• C. Krw=kg/k
• D. Krw=kw/kr

Answer: (A)

Relative permeability shows how easily a phase can move through a rock when multiple phases are present, normalized by the rock’s single-phase ability. It is defined as the phase’s permeability divided by the rock’s intrinsic (absolute) permeability. For water, that means Krw = kw / k, where kw is the permeability to water if the rock were fully water-saturated and k is the rock’s absolute permeability. This yields a dimensionless value between 0 and 1, reflecting how the presence of other phases reduces flow. The other expressions either invert the ratio, use the wrong permeability for the phase, or mix in a different symbol, so they don’t match the standard definition.

Relative permeability shows how easily a phase can move through a rock when multiple phases are present, normalized by the rock’s single-phase ability. It is defined as the phase’s permeability divided by the rock’s intrinsic (absolute) permeability. For water, that means Krw = kw / k, where kw is the permeability to water if the rock were fully water-saturated and k is the rock’s absolute permeability. This yields a dimensionless value between 0 and 1, reflecting how the presence of other phases reduces flow. The other expressions either invert the ratio, use the wrong permeability for the phase, or mix in a different symbol, so they don’t match the standard definition.