Impact of aquifer properties on the extent and timeline of CO2 trapping

Geologic CO₂ sequestration in porous saline aquifers is a promising approach to reducing atmospheric concentrations of CO₂. Reactive transport simulations provide the opportunity to analyze which factors influence geochemical reactivity in the reservoir, understand those most important for promoting CO₂ trapping, and assess individual sites. Field-scale aquifer characterization is time and resource intensive such that here, reactive transport simulations are leveraged to enhance understanding of selected aquifer properties including porosity, permeability, depth of storage, and carbonate mineralogy on the overall CO₂ trapping potential to better select sites promoting geochemical reactivity for CO₂ trapping. There are different mechanisms for sequestrating CO₂. Once injected, CO₂ will dissolve into the brine to create an acidic environment, resulting in the dissolution of pre-injection formation minerals. Released ions can reprecipitate as secondary minerals. The dissolved CO₂ and mineralized CO₂ are considered as a more secure form of CO₂ trapping in this study compared to the free supercritical CO₂. Here, a framework leveraging a controlled set of field scale simulations is developed to facilitate rapid, optimized site selection. Simulations vary aquifer properties to understand the impact of each unique property on CO₂ trapping, tracking, and comparing the amount of supercritical, aqueous, and mineralized CO₂. The rate at which the CO₂ injected into the aquifer is converted to aqueous or mineralized CO₂ is newly defined here as the sequestration efficiency and used to compare simulation results. The reservoir depth and fraction of carbonate minerals in the formation are shown to be more important factors than reservoir porosity and permeability in affecting CO₂ trapping. However, the impact of aquifer properties on the evolution of injected CO₂ depends on the stage of the sequestration project. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.