Imbibition Relative Permeability

Definition - What does Imbibition Relative Permeability mean?

Imbibition Relative Permeability is a situation in fluid flow process whereby the saturation of wetting phase increases thereby increasing the wetting fluid phase mobility. This situation causes the capillary pressure to decrease. The relative permeability is the reduction in the flow capability of a fluid because of the presence of multiple fluids 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 Imbibition Relative Permeability

Imbibition relative permeability is related to the capillary pressure curves. Capillary Pressure Curves play an important role in understanding the saturation distribution of fluids in hydrocarbon reservoirs and affect the multiphase flow of fluids as well as imbibitions through porous rocks. Every rock has a pore throat size distribution by which more pressure can be applied on the non-wetted phase. All the openings of small pores are invaded because of pressure distribution.

Capillary Pressure Curve depends on the Drainage and Imbibition processes.

  • Drainage process (Drainage Relative Permeability) - In this fluid flow process, the saturation of non wetting phase increases, which in turn increases the mobility of non wetting fluid phase.
  • Imbibition process (Imbibition Relative Permeability) - In this fluid flow process, the saturation of wetting phase increases which increases wetting fluid phase mobility.

A Capillary Pressure Curve is shown in the figure below:

Where,

Si = Saturation of irreducible wetting phase

Sm = 1 - Residual saturation of non-wetting phase

Pd = Displacement pressure i.e., the pressure required to force non-wetting fluid into large pores of the rock.

= Pore size distribution index which determines shape of the Capillary Pressure Curve.

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