Numerical simulation of compositional phenomena in petroleum reservoirs

Abstract

The only fundamental difference between compositional reservoir simulators and simulators of the black-oil type lies in their treatment of fluid properties and phase behavior. Since compositional simulation is necessarily a more expensive proposition than black-oil simulation, the only justification for a compositional study is the increased accuracy that can be obtained by a more realistic description of the fluid. This paper focuses on the consistent and accurate treatment of fluid properties in describing a three dimenisional compositional simulator. It describes the methods used to calculate densities, viscosities, and equilibrium K-values, presenting comparisons between calculated values and experimental data. Another subject of discussion in the paper is the problem of numerical dispersion. An example simulation illustrates the magnitude of the problem and demonstrates that the methodof-characteristics provides a practical means of eliminating numerical dispersion in multicomponent miscible displacement problems.