Using transparent microfluidic cells to study the two-phase properties of a synthetic porous medium, we establish that the interfacial area per volume between nonwetting and wetting fluids lifts the ambiguity associated with the hysteretic relationship between capillary pressure and saturation in porous media. The interface between the nonwetting and wetting phases is composed of two subsets: one with a unique curvature determined by the capillary pressure, and the other with a distribution of curvatures dominated by disjoining pressure. This work provides experimental support for recent theoretical predictions that the capillary-dominated subset plays a role analogous to a state variable. Any comprehensive description of multiphase flow properties must include this interfacial area with the traditional variables of pressure and fluid saturation. Also provides the supplementary data for Joekar Niasar, V., S. M. Hassanizadeh, L. J. Pyrak-Nolte, and C. Berentsen (2009), Simulating drainage and imbibition experiments in a high-porosity micromodel using an unstructured pore network model, Water Resour. Res., 45, W02430, doi:[http://dx.doi.org.ezproxy.lib.purdue.edu/10.1029/2007WR006641 10.1029/2007WR006641]. Development of pore network models based on detailed topological data of the pore space is essential for predicting multiphase flow in porous media. In this work, an unstructured pore network model has been developed to simulate a set of drainage and imbibition laboratory experiments performed on a two-dimensional micromodel. We used a pixel-based distance transform to determine medial pixels of the void domain of micromodel. This process provides an assembly of medial pixels with assigned local widths that simulates the topology of the porous medium. Using this pore network model, the capillary pressure-saturation and capillary pressure-interfacial area curves measured in the laboratory under static conditions were simulated. On the basis of several imbibition cycles, a surface of capillary pressure, saturation and interfacial area was produced. The pore network model was able to reproduce the distribution of the fluids as observed in the micromodel experiments. We have shown the utility of this simple pore network approach for capturing the topology and geometry of the micromodel pore structure.
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Researchers should cite this work as follows:
- V. Niasar, S. Hassanizadeh, Pyrak-Nolte, L. J., C. Berentsen (2013). Linking Pressure and Saturation through Interfacial Areas in Porous Media. (Version 2.0). Purdue University Research Repository. doi:10.4231/D39K45S8J