Investigation of Scale and Heterogeneity Effects on Flow and Transport in Multiphase Systems.

Abstract

Abstract : Contamination of the subsurface environment by fluids that are immiscible with water is recognized as a commonplace occurrence. Subsurface systems that include immiscible fluids are multiphase systems; the phases present may include a solid, an aqueous, an immiscible organic, and a vapor. Fundamental processes that govern the behavior of such systems are complex. Several crucial questions remain to be answered for multiphase subsurface systems before a mature level of understanding is achieved. Among the most important of these unresolved issues are the effects of measurement scale, system dimensionality, and media heterogeneity on fundamental fluid flow and interphase mass transfer processes. Work performed on this project was aimed at investigating scale effects in homogeneous and heterogeneous multiphase porous media systems. Important scale effects were shown in experimental and theoretical work, showing that continuum-based approaches have severe limitations for multiphase porous media systems. A powerful x-ray method was developed, which offers significant advancements in precision and accuracy for measuring fluid saturations in small to intermediate scale experiments when compared to conventional dual-gamma methods. Intermediate scale experiments have shown the profound influence of moderate heterogeneity on multiphase flow and transport processes, which has implications for the appropriate form of constitutive relations and application of continuum-based approaches. (AN)