2-D reactive transport modeling of the fate of CO2 injected into a saline aquifer in the Wabamun Lake Area, Alberta, Canada

• 2D modeling was performed to investigate CO2 injection into a saline aquifer.
• CO2 injection caused dolomite dissolution and calcite precipitation in the aquifer.
• The injected CO2 was trapped via mainly hydrodynamic trapping.
• Increase in the formation porosity and permeability was observed.
• The pressure build-up due to a high injection rate did not exceed the fracturing pressure.

Carbon capture and storage (CCS) is a viable option to reduce emissions of anthropogenic CO2 into the atmosphere. One important component during the storage site selection process is the prediction of the movement and the fate of the injected CO2 in the chosen reservoir. The fate of CO2 injected into a saline aquifer of the Devonian Nisku Formation in Alberta (Canada) was simulated using the reactive transport code TOUGHREACT. A 2D radially symmetric model was developed for a 50-year CO2 injection phase followed by a 1000-year storage period. CO2 was injected into the bottom 10 m of the Nisku Formation at a rate of 1 Mton/year for 50 years. The injected supercritical CO2 spread out radially up to 3.5 km after 50 years of injection and 6.0 km after 1000 years of post-injection. After 1000 years, the injected CO2 was trapped in the Nisku Formation underneath the excellent seal of the Calmar shale predominantly as free CO2 via hydrodynamic trapping (76%) and to a lesser extent by solubility trapping (23%) in aqueous phase (HCO3-(aq)). Mineral trapping of injected CO2 in the Nisku aquifer was negligible. This study predicted the interactions of the fluids and rock minerals with injected CO2 in the storage Nisku aquifer, the Calmar caprock and the bottom rock Ireton shale. This information will be highly beneficial for potential future CO2 injection projects targeting the saline aquifer of the Nisku Formation in Western Canada.