Quantitative evaluation of pore-scale heterogeneity based on statistical analysis of a pore network model of unconsolidated porous media

Abstract

Heterogeneity is a common feature of aquifers and plays an important role in the efficiency of remediation of groundwater contamination. Pore-scale heterogeneity is an important control on governing mass transport and chemical/biological reactions in reactive transport processes, but quantitative characterization and systematic assessment of this property has been limited. In this study, a pore-scale-heterogeneity-synthetic index was developed to quantitatively characterize pore-scale heterogeneity of unconsolidated porous media. It was an attempt to systematically assess pore-scale heterogeneity based on statistical analysis of pore-structure characterization parameters. Pore network extraction was conducted to assist in quantifying the pore structure based on X-ray μ-CT imaging data. The quantitative characterization of pore structure provided input data for a comprehensive evaluation model. Two alternative weighting approaches—principle component analysis and the entropy method—were utilized to calculate the weight of each evaluation indicator. Based on the comprehensive evaluation results, a guideline for classification of pore-scale heterogeneity was proposed by cluster analysis. Further analysis indicated that particle size, shape, and distribution had a potential influence on pore-scale heterogeneity. The bigger, more irregular particles, as well as a wider particle-size distribution, were conducive to forming high heterogeneity at pore scale. The obtained results will provide useful information and theoretical support for pore-scale heterogeneity characterization and understanding of the pore-scale mechanisms of reactive transport processes.