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

Abstract

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.