Quantitative Assessment of the Heterogeneity and Reproducibility of Repacked Silica Sand Columns

Abstract

Core Ideas We quantified heterogeneity and reproducibility of repacked sand column microstructure. The averaged pore geometric properties were quantified using Minkowski functionals. Spatial heterogeneity was analyzed using a mathematical morphological operation. Column experiments are widely used for mechanism and application studies in different fields. A major challenge and an advantage of the repacked porous column are its uniformity and reproducibility. Bulk density is a commonly used parameter to evaluate the uniformity and consistency of random packing. The internal structure of pore space is usually ignored and lumped into the bulk density. However, flow and transport characteristics of the repacked porous media are not fully defined from the bulk density but also depend on the internal structure. In this paper, we quantitatively assessed the heterogeneity and reproducibility of repacked sand columns using integral geometry methodology. X‐ray computed tomography is applied to visualize the pore space of the column repacked with different silica sands. The acquired tomography images are processed and quantitatively analyzed using Minkowski measures. The Minkowski functionals combined with the granulometric density function were applied to describe the spatial heterogeneity of microstructures. The results have demonstrated that the Minkowski functionals proportional to the well‐known geometric quantities are able to characterize the average geometrical properties of complex pore space. The pore size distributions of sand column are obtained through morphological opening operation. The two‐parameter Weibull distribution has been found reasonably describe the granulometric density acquired from the morphology analysis. The Minkowski densities joint with the critical pore diameter as well as parameters of Weibull function at different locations of each column have demonstrated the heterogeneity of the sand column. The small variation in the finer sand column indicates the heterogeneity is relatively smaller than that of the coarser ones. The relatively small differences among the repetitions of finer sand columns suggest more reliable reproducibility in comparison to the coarser sand columns.