Introducing a novel method for prediction of imbibition relative permeability in mixed wet systems

Accurate determination of the fluid relative permeabilities in porous media is important in simulation of enhanced oil recovery (EOR) processes since it directly affects the estimation of total oil production. The imbibition relative permeability is a strong function of initial saturation form which the imbibition process starts. So it is nearly impossible to conduct many experiments to measure all possible imbibition relative permeability data. There are many predictive models in literature, such as Land's and Carlson's, however, these models are developed for water-wet samples and cannot be used for mixed-wet samples. In mixed-wet samples, the nonwetting phase relative permeability during imbibition stage is more than its value during drainage process because of the presence of oil layers and reduced snap off. In this study, a new theoretical method was suggested to predict the increased oil relative permeability during the imbibition stage in mixed-wet samples. It was shown that the suggested method was able to predict the increase in oil relative permeability during the imbibition stage with reasonable accuracy for a mixed-wet reservoir rock. Moreover, by application of this study the errors in estimation of total oil production and residual oil saturation during imbibition stage in mixed-wet reservoirs decreased by 13-30%.