Mechanistic Study on CO2-N2 Chromatographic Partitioning in Saline Aquifers

Summary Underground sequestration of carbon dioxide is an effective way to deal with climate change. CO2-N2 chromatographic partitioning in saline aquifers can help separate CO2 and N2, leaving CO2 storage and N2 enrichment in the formation. This paper is focused on the effect of phase behavior, transport properties, chemical reactions and adsorption on CO2-N2 chromatographic partitioning. Solubility experiments were performed with flue gas with 15 mol% CO2 and 85 mol% N2 in formation brine solutions with different salinity and ion compositions. Based on solubility experiments, fractional flow analysis was performed to investigate the effect of solubility and transport properties on CO2-N2 chromatographic partitioning. Numerical simulation models were constructed to investigate the effect of mineral composition and adsorption on chromatographic partitioning. Experimental results show that the solubility difference between CO2 and N2 decreases with salinity increase. Fractional flow analysis shows that the partitioning distance between CO2 front and N2 front increases as CO2-N2 solubility difference and two-phase flow region increase. Numerical simulation results indicate that quartz and calcite have little effect on chromatographic partitioning, however, the presence of olivine can increase partitioning distance. Adsorption difference between CO2 and N2 can also potentially increase partitioning distance.