Quantifying Salt Precipitation During CO2 Injection: How Flow Rate, Temperature, and Phase State Control Near-Wellbore Crystallization

TL;DR

This study uses microfluidic experiments to quantify how flow rate, temperature, and phase state influence salt crystallization during CO2 injection, providing insights into near-wellbore permeability issues in geological storage.

Contribution

It offers detailed quantification of salt crystallization dynamics across different phase states and flow regimes, linking transport parameters to crystallization kinetics and displacement efficiency.

Findings

Supercritical CO2 enhances displacement efficiency and evaporation rate.

Crystallization time decreases significantly with increasing temperature and phase change.

Final crystal fractions are much higher in gas-phase conditions, indicating phase-dependent transport effects.

Abstract

Salt precipitation near injection wells can reduce permeability, induce excess pressure buildup, and reduce injectivity within days to weeks of CO2 injection, yet the pore-scale mechanisms coupling multiphase flow, evaporation, and crystallization warrant further detailed quantification across variable phase states and flow regimes. We present high-resolution microfluidic experiments that systematically quantify the dynamics of halite crystallization during CO2-driven brine evaporation across liquid, gaseous, and supercritical phases (50-80 bar, 20--60 C, Pe = 50--1440). Crystallization kinetics are controlled by transport, with the Avrami rate constant (K) increasing by two orders of magnitude with the Peclet number and exhibiting the dependence of the temperature of Arrhenius (Ea = 58.6 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 (Sherwood numbers 2-3x higher than the liquid phase), reducing the nucleation time from 57 min (20C, liquid) to <1 min (40-60 C, gas/supercritical). The final fractions of crystal 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. Despite probabilistic nucleation, final crystal distributions are spatially rather uniform with no systematic inlet-outlet bias. These quantitative relationships between 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 in geological storage of saline and hypersaline CO2.