Effect of Flue-Gas Impurities on the Process of Injection and Storage of $CO2$ in Depleted Gas Reservoirs

Our previous coreflood experiments—injecting pure $CO2$ into carbonate cores—showed that the process is a win-win technology, sequestrating $CO2$ while recovering a significant amount of hitherto unrecoverable natural gas that could help defray the cost of $CO2$ sequestration. In this paper, we report our findings on the effect of “impurities” in flue gas—$N2$⁠, $O2$⁠, $H2O$⁠, $SO2$⁠, $NO2$⁠, and CO—on the displacement of natural gas during $CO2$ sequestration. Results show that injection of $CO2$ with approximately less than $1mole%$ impurities would result in practically the same volume of $CO2$ being sequestered as injecting pure $CO2$⁠. This gas would have the advantage of being a cheaper separation process compared to pure $CO2$ as not all the impurities are removed. Although separation of $CO2$ out of flue gas is a costly process, it appears that this is necessary to maximize $CO2$ sequestration volume, reduce compression costs of $N2$ (approximately 80% of the stream), and improve sweep efficiency and gas recovery in the reservoir.