MODELING FLOW IN HETEROGENEOUS MEDIA USING STREAMTUBES .2. COMPOSITIONAL DISPLACEMENTS

In this paper, we extend the streamtube approach described in Part I t o compositional displacements. One-dimensional compositional solutions to three- and four-component problems are mapped along periodically u pdated streamtubes to yield two-dimensional compositional solutions fo r heterogeneous systems. In our technique, the complex physics describ ing multiphase, compositional flow is completely decoupled from the un derlying grid used to describe reservoir heterogeneity, allowing the c onstruction of approximate solutions using three to five orders of mag nitude less computation time than traditional finite-difference/finite -element approaches. In addition, by mapping one-dimensional, diffusio n-free solutions along streamtubes, the impact of numerical diffusion on displacement performance in standard numerical approaches can be es timated. We show, by example, that numerical diffusion may mitigate su bstantially, or even completely eliminate, any mobility contrast in a two-dimensional finite-difference compositional solution, resulting in optimistic recoveries.