Universality of Riemann solutions in porous media

Abstract Universality, a desirable feature in any system. For decades, elusive measurements of three-phase flows have yielded countless permeability models that describe them. However, the equations governing solution water and gas co-injection has robust structure. This universal structure stands for Riemann problems green oil reservoirs. In past we established large class three phase flow including convex Corey permeability, Stone I Brooks–Corey models. These share property characteristic speeds become equal at state somewhere interior saturation triangle. Here construct model with unequal triangle, equality occurring only point boundary Yet this still displays same structure, which favors two possible embedded two-phase water-oil or gas-oil. We focus on showing under minimum conditions must meet. finding is guide to seeking purely maximizing recovery.