A simulation study of the effect of trapping model, geological heterogeneity and injection strategies on CO2 trapping

Industrial CO2 emissions to the atmosphere can be reduced through geological storage, where the gas is injected into the subsurface and trapped by several mechanisms. Residual and solubility trapping are two important processes providing trapping, and their effectiveness ultimately determines the feasibility of geological storage. By means of numerical modeling, a systematic analysis was made concerning the factors potentially affecting trapping, to guide the planned injection experiments at the Heletz test injection site. The effect of enhanced-trapping injection strategies along with the role of geological heterogeneity and the choice of trapping model (TM) were evaluated. The results showed that adding chase-fluid stages to a conventional CO2 injection enhanced the trapping. Taking into account the geological heterogeneity decreased trapping, as this retarded the buoyant migration, resulting in less imbibition and residual trapping. The choice of TM was significant, with the simplified Land TM producing the highest trapping, and the Aissaoui TM the lowest. The results stress the importance of using an appropriate TM as well as heterogeneity model for the site in question for any predictive modeling of CO2 sequestration, as different assumptions may lead to significant discrepancies in the predicted trapping.