Simulation of Relative Permeability Hysteresis to the Nonwetting Phase

ABSTRACT In reservoir fluid flow, the situation described by an increase in nonwetting phase saturation followed by an increase in wetting phase saturation causes a relative permeability hysteresis effect that is well known. The imbibition relative permeability is a function of the historical maximum nonwetting phase saturation, hence there is no single imbibition curve applicable for use in reservoir modeling. This paper presents a method which allows the calculation of imbibition relative permeability starting at any saturation. The data required are the drainage curve, the historical maximum nonwetting phase saturation, and a minimum of one additional point on some corresponding experimental imbibition curve. In this development, all imbibition curves are shown to be parallel. Also significant is the fact that the residual nonwetting phase saturation can be calculated without a complete experimental specification of the imbibition curve.