Geometry & Dynamics of Interfaces in Porous Media

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Geometry and Dynamics of Interfaces in Porous MediaL. J. Pyrak-Nolte & N. J. GiordanoPurdue UniversityThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The problem of multiphase fluid flow in porous media is important in many areas, including ground water remediation, the extraction of oil & gas from subsurface reservoirs and carbon sequestration in geologic formations. The development of experimental and theoretical understandings of the behavior of multiple fluids in porous systems is an active area of research with many open questions. It is known that measurements of capillary pressure (Pc) and saturation (Sw) are not sufficient to fully describe the behavior of fluid distributions. Recent work has suggested that the interfacial area per volume between the fluid phases (awn) is an essential third "state variable" needed for a description of these systems. While studies of 2-D micro-models under equilibrium conditions has provided important quantitative insight into the role of interfacial geometry in multiphase systems, key issues remain to be resolved. Scientific objectives of the proposed research include: (1) Determine if and how the Pc-Sw-awn relationship observed in 2-D systems translates to 3-D systems. We will fabricate 3-D transparent micro-models for direct imaging of fluid distributions in 3-D using confocal laser scanning microscopy. A significant effort will be made to develop 3-D transparent micro-models from which information can be extracted on fluid-fluid and fluid-solid interfaces to determine the effect of micro-model dimensionality on the Pc-Sw-awn relationship. (2) Determine the role of thin films on Pc and on the interfacial geometry. We will 1) use laser confocal microscopy to image films, film pockets and three dimensional fluid interfaces-especially the presence and movement of entrained wetting phase and associated films; and (2) fabricate micro-capacitor sensors inside the 2-D micro-models to measure film thickness directly. A significant effort will be made to demonstrate the use, resolution and repeatability of micro-capacitors for measuring local pressures in the micro-model. (3) Determine if relaxation behavior under dynamic conditions depends on the evolution of the interfacial geometry with time, or if it is only a property of the pore geometry of the medium. While understanding fluid distributions under equilibrium conditions is important, many industrial and natural systems experience pressure transients. We will use high frame rate imaging to study the dynamic behavior of fluid interfaces in 2-D micro-models as they approach equilibrium after a pressure transient.