Analysis of a Mass-based Compositional Multiscale Formulation a Report Submitted to the Department of Energy Resources Engineering of Stanford University in Partial Fulfillment of the Requirements for the Degree of Master of Science

The convergence of a two-pseudocomponent sequential-implicit Compositional Multiscale Finite Volume (C-MSFV) method is studied and formulation improvements are suggested. Coupling of the pressure and transport equations is found to be a major factor in the convergence of the sequential-implicit solution strategy and is determined to be the source of convergence problems for cases with large solubility ratios and large differences in component densities. Improvements are implemented to reduce coupling and enhance convergence by allowing updates of coefficients in the transport equation and by increasing reliance on black-oil relations in the derivation of the pressure equation. The improved formulation is tested for single-grid fine-scale simulations for a variety of saturated and undersaturated cases in one and two dimensions. The improved formulation is shown to reduce the number of coupling iterations significantly and allow for solution convergence for a wider range of cases.