The pore-scale physics of salt clogging during CO2 storage in saline aquifers

Deep saline aquifers are prime candidates for the geological storage of carbon dioxide (CO 2 ). However, gas injection can cause brine dry-out and salt precipitation, impairing injectivity. While the role of multiphase flow is recognized, the specific impact of CO 2 reactivity compared to hydrodynamic effects alone remains unclear. This study presents a pore-scale investigation using micromodels saturated with NaCl brines (5, 10, and 20 wt%) to delineate these mechanisms. We compare CO 2 injection to nitrogen (N 2 ), which serves as a non-reactive control. At 20 wt% salinity, CO 2 triggered early salt nucleation, leading to localized deposition near the inlet and dendritic crystal morphologies. In contrast, N 2 delayed nucleation, resulting in a broader deposition footprint towards the outlet and favoring cubic crystals. Despite these divergent dynamics, total salt saturation was comparable (38.99% for CO 2 vs. 42.09% for N 2 ), yielding similar final permeability impairment (∼84–82% of initial). At lower salinities (5–10 wt%), both gases produced less salt and damage, yet preserved the same kinetic and spatial contrast. We conclusively demonstrated that gas-specific chemistry—not hydrodynamics alone—governs the precipitation pathway, dictating the kinetics, spatial distribution, and morphology of salt clogging, with critical implications for predicting and managing formation damage in CO 2 storage projects.