A model for predicting permeability evolution of organic-contaminated clays capturing corrosion effect

Abstract

The effect of organic corrosion on the permeability of clay has been recognized, however, a quantitative characterization and the underlying micro-scale mechanisms remain inadequately understood. Drawing on damage theory, this study introduces a corrosion variable to quantify the corrosion degree of organic contaminants on the meso-scale fabric of clays (e.g., macro pores and aggregates). The corrosion variable is calculated through a novel corrosion evolution law, which incorporates van der Waals force, double layer force and contaminant volume fraction. On these basis, permeability evolution model for organic-contaminated clays is then derived by introducing connected pore ratio and effective specific surface area. Model performance is assessed with experimental data sets encompassing 18 clays and 21 organic fluids. Pore structure tests including scanning electron microscopy (SEM) and Mercury intrusion porosimetry (MIP) tests also indicate that meso-scale transformation is consistent with the observed increase in permeability tests. The superiority of the proposed model can also be found from the comparison with existing models. Finally, the model is further applied successfully to a laboratory-scale one-dimensional flow simulation, tracking the evolution of the saturated hydraulic conductivity under sequential permeated with water, ethanol, and benzene in clays.