Uncertainties of geochemical modeling during CO2 sequestration applying batch equilibrium calculations

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The objective of this study is to analyze how different factors influence the geochemical modeling during CO2 sequestration. A geochemical batch equilibrium model was applied to simulate a virtual CO2 injection into a saline Keuper aquifer, and various scenario analyses were conducted. The amount of CO2 that could be trapped in the formation water and in carbonate form was calculated using the PHREEQC model code, utilizing four different thermodynamic datasets. The results indicated that the choice of thermodynamic database resulted in a 61% variation in the amount of trapped CO2, while the selection of secondary mineral assemblages caused a 74% variation. Additionally, recalculating equilibrium constants with respect to a pressure of 125 bars influenced the trapped CO2 amount by 11%. These findings highlight the significance of incorporating sensitivity analyses into reaction pathway modeling to better understand uncertainties in geochemical modeling related to CCS.