Interfacial Controls on Dynamics and Equilibration in Porous Media

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Interfacial Controls on Dynamics and Equilibration in Porous MediaMost current macroscopic theories of multi-phase flow are based on the combined equations of Darcy's Law and an empirical relationship between capillary pressure and saturation. In recent years, a number of studies have shown that this state of affairs is not necessarily optimal. However, in a given porous medium, saturation and interfacial areas are independent variables, i.e., many different configurations resulting in a range of interfacial areas are possible for a single saturation. Awareness of this effect of interfacial forces on multi-phase flow has led to the development of alternative theories based on fundamental thermodynamic considerations in which interfacial areas are introduced as separate thermodynamic entities. Thus capillary pressure becomes a function of both saturation and specific fluid-fluid interfacial area and it has been suggested that the system will be uniquely described by this functional dependence. Recent work has indicated that a single unique surface cannot indisputably describe two-phase flow under nonequilibrium conditions, suggesting that there may be something else missing from the theory. The goal of the proposed work is to improve on a paucity of delicate measurements and generate highly unique data sets from which strategic advances can be made on a number of fronts with respect to the fundamental dynamics of multi-phase flow in porous media. The data generated will consist of dynamic drainage and imbibition experiments during which x-ray tomographic images will be captured such that the fluid phases can be tracked in unprecedented detail in three dimensions. This will allow for measurement of developing interfacial areas, curvatures, and trapping behavior of the fluid phases. This novel data set can be used in a combined effort to validate findings based on multi-phase theories and for a broader exploration of interfacial dynamics, in particular the formation of interfacial area and curvature evolution. Improved understanding of the physics of multi-phase flow in porous media has societal impacts through applications in various fields such as groundwater management and remediation, soil and agricultural science, petroleum engineering, and geologic sequestration of CO2. This project aims to generate new data set that will not only first and foremost support progress in understanding the role of interfaces, and their dynamic behavior, on porous media flow and transport, but also improve on existing theories describing these processes. The generated high-resolution imagery will be made available to the broader scientific community through digital archiving. Ultimately, this will allow for improved management of natural resources and ability to reliably engineer porous systems leading to improvements in water usage and energy development.