Revealing Transport, Dissolution, and Precipitation Behaviors in Electrokinetic-Geochemical Reaction System at Pore-to-Core Scales

Abstract

Net-zero carbon targets drive the development of new underground activities such as hydrogen storage and in situ critical mineral recovery, all of which involve geochemical reactions between minerals and fluid/ion transport. Understanding these processes is key to optimizing efficiency and minimizing environmental impacts. However, the fundamental mechanisms of ion transport, mineral dissolution, and secondary precipitation remain poorly understood, particularly at the pore scale. This gap partly arises from the challenges of characterizing samples at such a fine scale, where fluid/ion transport and reactions occur simultaneously. Herein, a core-to-pore-scale experimental approach, combined with time-lapse three-dimensional (3D) imaging, is designed to characterize fluid/ion transport, dissolution, and precipitation processes. We implemented this workflow in an electrokinetic in situ recovery (EK-ISR) system. Time-lapse 3D micro-computed tomography (micro-CT) images were acquired during the experiment to observe dissolution and precipitation dynamics and to measure pore-scale physical parameters. Findings indicate uniform reactive ion transport and mineral dissolution under EK conditions, with over 78% of the target mineral dissolved. Time-lapse images reveal multiple dissolution and precipitation patterns that influence reactive transport processes. Geochemical modeling based on pore-scale parameters demonstrates over 90% correlation with core-scale experimental data. Our workflow demonstrates a promising capability for characterizing reactive transport processes across pore-to-core scales.