Pore-scale Information Research Articles

Pore-Scale Study of Nonaqueous Phase Liquid Dissolution in Porous Media Using Laser-Induced Fluorescence

Little quantitative, experimental pore-scale information exists regarding nonaqueous phase liquid (NAPL) ganglia undergoing dissolution in porous media. By using refractive index matched fluids and porous media, we have been able to nonintrusively visualize NAPL dissolution (at constant capillary numbers) in three dimensions using laser-induced fluorescence. The results provide dynamic, quantitative information regarding ganglia surface area, volume, position, and shape. It appears that ganglia smaller than a few pore volumes are spheroid, whereas larger ganglia exhibit a fractal area to volume scaling. Evidence of ganglia breakup is found for all capillary numbers studied. Mobilization, however, is only important at higher capillary numbers.

Probing Ganglia Dissolution and Mobilization in a Water-Saturated Porous Medium using MRI

Magnetic resonance imaging (MRI) is used to probe the evolution of geometric characteristics such as the volume, shape, surface area, and cluster size of octanol ganglia trapped in a model porous medium, in this case a packing of spheres, as they dissolve into a mobile aqueous phase. The resulting pore-scale information is used to assess various assumptions used in existing models of the dissolution process. Dissolution of the ganglia was characterized by a reduction in the overall number of ganglia with little effect on the shape and mean of the volume distribution of the ganglia. This apparently anomalous result is explained by dissolution of the ganglia until they reach a critical size, which is dependent on the structure of the pore space, at which point they are mobilized and subsequently removed from the porous medium. The shape of the entrapped ganglia is characterized by a fractal dimension in the range 2.2–2.3, suggesting that models which assume a Euclidean geometry for the entrapped ganglia are appropriate. No significant change in the shape of entrapped ganglia is observed during dissolution. In agreement with the results of earlier workers, most hydrocarbon ganglia exist as singlets within the pore structure.

Pore-Scale Heterogeneity From Mercury Porosimetry Data

SummaryThis paper describes a quantitative method of determining pore-scale heterogeneity with constant-rate mercury porosimetry data from the apparatus for pore examination (APEX). Besides being used as a measure of heterogeneity, APEX pore-scale information can be used to assess quantitatively the effect of rock texture or pore geometry on the efficiency of any process, such as EOR, aimed at recovering waterflood residual oil. The paper shows a method for calculating EOR displacement efficiency from APEX poroshmetry data. Berea sandstones and San Andres dolomites are used as examples.