Three-Phase Capillary Pressure Correlation for Mixed-Wet Reservoirs

摘要

We present new three-phase capillary pressure correlations thatrncould be employed to model the dynamics of three-phase transitionrnzones in mixed-wet reservoirs. The capillary pressuresrnare expressed as a sum of two terms. One term is a functionrnof a decreasing saturation and the other term a function of anrnincreasing saturation. Thus the correlations depend on the typernof displacement process, i.e., the direction of saturation change.rnThe two-saturation dependency, together with the inclusion ofrnadjustable parameters, ensures that the correlations account forrndifferent wettability conditions, saturation histories, and differentrnrelationships between the three capillary pressures.rnThe correlations are compatible with a smooth transitionrnbetween two- and three-phase flow if one of the phases appearsrnor disappears. In particular, if the gas saturation becomes zero,rnit is shown that the correlations are reduced to a previously publishedrntwo-phase correlation validated for oil/water systems inrnmixed-wet rock.rnCapillary pressure curves for various conditions, computedrnusing a previously developed bundle-of-triangular-tubesmodel,rnare compared with the correlations, and the match is excellentrnin all cases. Finally, the correlations are validated experimentallyrnby centrifuge measurements performed on water-wetrncores.