An empirical model for three-phase relative permeability

We present an empirical model for three-phase relative permeability. We all ow for changes in hydrocarbon composition, different saturation paths, and the trapping of oil, water, and gas. The model is based on saturation-weigh ted interpolation between the two-phase relative permeabilities. By writing the relative permeabilities as unique functions of a flowing saturation, t he model predicts the behavior for any sequence of saturation changes and a ccounts for trapping. Layer drainage allows the oil relative permeability t o be extrapolated to low saturation. The formulation for water-wet media, i ncluding layer drainage and trapping, is tested against experimental three- phase data.