In Situ Quantification of Colloidal Kaolinite Transport and Attachment in Porous Media Using Positron Emission Tomography

Migration of variably sized fines or geogenic colloids is a significant concern for the long-term efficiency of aquifer management and reservoir injection and extraction operations. Characterizing the migration of colloids in porous media has been widely studied; however, few studies have quantified sub-core colloidal transport behavior and related this to bulk sample observations under transient conditions. In this study, the transport of colloidal kaolinite through sand packs is analyzed using UV–Vis spectrophotometry and positron emission tomography (PET). PET imaging was completed by imaging an aqueous pulse of suspended radiolabeled kaolinite under single-phase flow conditions. The experimental PET imaging approach allows for the accurate 4-D quantification of changes in colloidal kaolinite transport, attachment, and detachment properties at the sub-centimeter scale. This study provides a novel approach for the quantification of inorganic colloid transport in geologic porous media, providing a foundation for future work to be done on more complex and heterogeneous systems under transient flow and fluid chemistry conditions.