The objective of this study was to examine the pore-scale distribution and morphology of organic immiscible liquid in natural porous media containing three immiscible fluids. High-resolution, three-dimensional images of an organic liquid (tetrachloroethene) in both three-phase (water–air–organic liquid) and two-phase (water–organic liquid) systems were obtained using synchrotron X-ray microtomography. These data were used to quantitatively characterize the morphology of the organic liquid residing within columns packed with one of three natural, sandy porous media. Organic-liquid blobs varied greatly in both size and shape, ranging from small, single spheres (≥0.03 mm in diameter) to large, amorphous ganglia with mean lengths of 4 to 5 mm. Singlets comprised the greatest number of blobs, whereas the large ganglia, while much fewer in number, comprised the majority of the organic-liquid surface area and volume. A significant portion of the organic liquid in the three-phase systems was observed to exist as lenses and films in contact with air. These features were not observed in the two-phase water–organic liquid systems. The median of the blob-frequency distributions was smaller and the variance larger for the three-phase systems. In addition, the global specific surface areas of the organic liquid were greater for the three-phase systems. These differences are attributed to the presence of the organic-liquid lenses and films for the three-phase systems.

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