A PARAMETRIC MODEL FOR PREDICTING RELATIVE PERMEABILITY-SATURATION-CAPILLARY PRESSURE RELATIONSHIPS OF OIL-WATER SYSTEMS IN POROUS-MEDIA WITH MIXED WETTABILITY

A parametric two-phase, oil-water relative permeability/capillary pres sure model for petroleum engineering and environmental applications is developed for porous media in which the smaller pores are strongly wa ter-wet and the larger pores tend to be intermediate- or oil-wet. A sa turation index, which can vary from 0 to 1, is used to distinguish tho se pores that are strongly water-wet from those that have intermediate - or oil-wet characteristics. The capillary pressure submodel is capab le of describing main-drainage and hysteretic saturation-path saturati ons for positive and negative oil-water capillary pressures. At high o il-water capillary pressures, an asymptote is approached as the water saturation approaches the residual water saturation. At low oil-water capillary pressures (i.e. negative), another asymptote is approached a s the oil saturation approaches the residual oil saturation. Hysteresi s in capillary pressure relations, including water entrapment, is mode led. Relative permeabilities are predicted using parameters that descr ibe main-drainage capillary pressure relations and accounting for how water and oil are distributed throughout the pore spaces of a porous m edium with mixed wettability. The capillary pressure submodel is teste d against published experimental data, and an example of how to use th e relative permeability/capillary pressure model for a hypothetical sa turation-path scenario involving several imbibition and drainage paths is given. Features of the model are also explained. Results suggest t hat the proposed model is capable of predicting relative permeability/ capillary pressure characteristics of porous media mixed wettability.