Relative Permeability

Definition - What does Relative Permeability mean?

Relative Permeability is the reduction in the flow capability of a fluid because of the presence of multiple fluids (water, natural gas condensates and natural gas) in a reservoir. It can be understood in phases such as single-phase, two phase or three phase system. For example, in the two phase system the fluids might contain oil and gas or oil and water. The presence of capillary forces reduces the rate of flow in a non-linear manner.

Petropedia explains Relative Permeability

Relative Permeability value generally varies from 0 to 1 and in the case of three phase permeability, the sum is always less than 1, which means that:

Kro + Krw + Krg < 1

The implication of relative permeability is useful for the flow of reservoir fluids. The following are the factors on which Relative Permeability depends on:

  • Wettability
  • Fluid saturation history
  • Pore Geometry
  • Fluid distribution

The samples on which the Relative Permeability measurements are done are costly to produce and they consume a lot of time. Mathematically, this can be interpreted as:

Kro = Ko/K , Krw = Kw/K , Krg = Kg/K Where r is rock, w is water, o is for oil and g is for gas.

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