Simulation of bench-scale CO2 injection using a coupled continuum-discrete approach

• Published in: The Science of the total environment 2024-12, Vol.954, p.176639, Article 176639
• Main Authors: Ashmore, Nicholas A., Krol, Magdalena M., Gilfillan, Stuart M.V., Van De Ven, Cole J.C., Mumford, Kevin G., Molnar, Ian L.
• Format: Article
• Language: English
• Subjects: Carbon capture and storage; Environmental monitoring; Gas migration; Groundwater; Mass transfer; Numerical modeling
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.176639

Unintended releases of CO2 from carbon capture and storage operations presents the risk of atmospheric emissions and groundwater or surface water quality impacts. Given the potential impacts, it is valuable to have tools capable of predicting groundwater concentrations and likely pathways of CO2 migration in the subsurface. Traditional multiphase flow models struggle to simulate the discontinuous flow expected at leakage sites. This work applied a coupled continuum-discrete model, ET-MIP, to simulate a bench-scale injection of CO2. Results demonstrate the capability of ET-MIP to accurately capture gas fingering behaviour, and the complexity of multicomponent mass transfer observed in the experiment. Simulations were computationally efficient, allowing for the use of multiple displacement pressure realizations. CO2 migration in the subsurface was shown to be sensitive to mass transfer, as i) increased groundwater velocity can dissolve leaked CO2 prior to reaching the surface and ii) background dissolved gases in the subsurface can impact the rate of upwards gas movement, gas distribution, and the composition and persistence of the gas phase. The sensitivity to mass transfer suggests it may be preferable to monitor for low-solubility gases in the source mixture rather than CO2. These findings are applicable to other gases in the subsurface, such as hydrogen or methane migrating from geoenergy wells. [Display omitted] •Unintended CO2 releases from CCS present risk of atmospheric and water impacts.•Coupled continuum-discrete model (ET-MIP) simulated bench-scale CO2 injection.•ET-MIP was able to accurately model gaseous and aqueous CO2 migration.•Monitoring low-solubility gases is preferable to CO2, due to mass transfer dynamics.•Appearance of gas in subsurface may not indicate CO2 presence due to mass transfer.