COLLABORATIVE RESEARCH: Closure of Thermodynamically Constrained Models for Multiphase Systems

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9901432GrayTraditional models of multiphase flow in porous media are based in empiricism and correlation of experimental data. Over the past two decades significant effort has been expended in developing a theoretical basis for multiphase flow models grounded in conservation principles. These approaches both reveal assumptions implicit in the current models and paths to more rigorous and robust models. One of the most elegant and conceptually satisfying approaches is the thermodynamically constrained averaging theory approach (TCATA). Recent work with the TCATA has led to the formulation of a set of models for two-phase flow in porous media. Additional steps, however, are required to develop the TCATA fully. The goals of the current proposal are to move beyond pure theory and idealized porous media to the description of real systems to demonstrate the viability, importance, and necessity of the TCATA for describing the physics of multiphase flow in porous media.To meet the goals of this project, we will use a combination of theoretical, pore scale morphology and modeling, continuum scale modeling, and laboratory experimental approaches. This work will be accomplished by building upon and continuing an existing collaboration between Professor Cass T. Miller's group at the University of North Carolina and Professor William G. Gray's group at the University of Notre Dame. This proposal describes the joint work of both groups, with each institution submitting directly to NSF requesting the resources needed to accomplish their share of the work.This work will have additional applicability to any array of multiphase porous media systems in both natural and engineered systems. We expect several significant accomplishments from this work: (1) the development of a theoretical framework that includes film flow and disjoining pressures; (2) the formulation of capillary pressure as a function of both saturation and interfacial area, thereby reducing or eliminating the hysteresis found when capillary pressure is represented as a function of saturation only; (3) the development of constitutive relations that include dynamic geometric parameters in expressing the functional dependence of relative permeability; (4) formulation and implementation of a numerical algorithm to solve the extended set of model equations; and (5) comparison of experimental data with model results to reveal the strengths and weaknesses of our approaches and the needs for further advancement of methods that account for the physics of multiphase flow.