Analytical Solutions for Multicomponent, Two-Phase Flow in Porous Media with Double Contact Discontinuities

This paper presents the first instance of a double contact discontinuity in analytical solutions for multicomponent, two-phase flow in porous media. We use a three-component system with constant equilibrium ratios and fixed injection and initial conditions, to demonstrate this structure. This wave structure occurs for two-phase injection compositions. Such conditions were not considered previously in the development of analytical solutions for compositional flows. We demonstrate the stability of the double contact discontinuity in terms of the Liu entropy condition and also show that the resulting solution is continuously dependent on initial data. Extensions to four-component and systems with adsorption are presented, demonstrating the more widespread occurrence of this wave structure in multicomponent, two-phase flow systems. The developments in this paper provide the building blocks for the development of a complete Riemann solver for general initial and injection conditions