CO2 plume migration and dissolution in layered reservoirs

Abstract

In carbon capture and storage (CCS) projects, the presence of layered permeability heterogeneity can strongly affect the migration of the supercritical CO₂ plume and CO₂ dissolution. By conducting a systematic study of plume migration in layered reservoirs with a wide range of permeability contrast between the layers, we show that the relationship between CO₂ plume footprint and permeability contrast has three distinct regimes. For moderate permeability contrasts from 1 to 5, the presence of different layers has little impact on plume migration. As the contrast increases from 5 to 50, the plume footprint decreases progressively. In the event of extreme contrast (>50), the footprint is smallest and independent of the heterogeneity. Overall, the footprint of the plume can vary by more than 2-fold, with large implications for monitoring, access to sites, and regulatory issues. The mass fraction of CO₂ dissolution can vary up to 2-fold depending on the degree of heterogeneity. We also show that the common practice of using permeability anisotropy to simulate multiphase flows in layered reservoirs works quite well in terms of plume footprint for permeability anisotropy ratios of up to 25, but large errors occur at more extreme contrast.