Chromatographic partitioning of impurities (H2S) contained in a CO2 stream injected into a deep saline aquifer: Part 2. Effects of flow conditions

Laboratory experiments reported in a companion paper were carried out to examine the chromatographic partitioning of impurities contained in a stream of CO2 injected into a deep saline aquifer. The solubility of the impurity gas in the CO2 stream compared to that of CO2, the in situ conditions of pressure, temperature and water salinity, and the concentration of the impurity gas affect the partitioning of the two gases. For CO2 streams containing H2S, numerical simulations reported here have successfully replicated the laboratory results including the breakthrough of CO2 ahead of H2S. Sensitivity analysis performed with the numerical model has shown that flow conditions, controlled by such parameters as medium permeability, pressure gradient, dispersion, gas mobility and flow direction, affect the breakthrough time and separation of the two gases, leading to delayed or earlier breakthrough, and increasing or decreasing the time lag between the breakthrough of the two gases. Vertical bottom-up flow leads to earlier breakthrough, while top-down flow leads to delayed breakthrough. These results are important in establishing monitoring strategies at CO2 storage sites and in evaluating the risks associated with the possible leakage of injected CO2 that contains impurities.