Abstract
Salt precipitation near injection wells can reduce permeability, drive excess pressure buildup, and impair injectivity within days to weeks of CO2 injection; yet, the pore-scale mechanisms coupling multiphase flow, evaporation, and crystallization remain poorly quantified across different phase states and flow regimes. To address this gap, we present high-resolution microfluidic experiments that systematically quantify halite crystallization dynamics during CO2-driven brine evaporation in liquid, gaseous, and supercritical phases (50–80 bar, 20–60 °C, Pe = 50–1440). Crystallization kinetics are transport-controlled: the Avrami rate constant (K) increases by 2 orders of magnitude with the Péclet number and follows Arrhenius temperature dependence (Ea = 62.6 kJ/mol). Supercritical CO2 achieves superior displacement efficiency (residual saturation 0.22–0.36; fractal dimension D = 1.79–1.82) and the fastest evaporation rates (Sherwood numbers 2–3× higher than the liquid phase), compressing crystallite formation times from 57 min at 20 °C (liquid phase) to under 1 min at 40–60 °C (gas and supercritical phases). Final crystal area fractions increase 10-fold from liquid (∼0.008) to gas-phase conditions (0.08–0.12), confirming that convective transport and phase state dominate over diffusion-limited mechanisms under our experimental conditions. Despite inherently probabilistic nucleation, final crystal distributions within the microfluidic chip are spatially deterministic, with no systematic inlet-to-outlet bias observed across all tested conditions. Together, the quantitative relationships among dimensionless parameters (Pe, Sh), kinetic constants (K, Ea), and phase-dependent displacement patterns provide critical benchmarks for validating pore-scale models and predicting near-wellbore permeability impairment during geological CO2 storage in saline and hypersaline aquifers.