Modeling of fate and transport of coinjection of H2S with CO2 in deep saline formations

The geological storage of CO2 in deep saline formations is increasingly seen as a viable strategy to reduce the release of greenhouse gases into the atmosphere. However, costs of capture and compression of CO2 from industrial waste streams containing small quantities of sulfur and nitrogen compounds such as SO2, H2S, and N-2 are very expensive. Therefore, studies on the coinjection of CO2 containing other acid gases from industrial emissions are very important. In this paper, numerical simulations were performed to study the coinjection of H2S with CO2 in sandstone and carbonate formations. Results indicate that the preferential dissolution of H2S gas (compared with CO2 gas) into formation water results in the delayed breakthrough of H2S gas. Coinjection of H2S results in the precipitation of pyrite through interactions between the dissolved H2S and Fe2+ from the dissolution of Fe-bearing minerals. Additional injection of H2S reduces the capabilities for solubility and mineral trappings of CO2 compared to the CO2-only case. In comparison to the sandstone (siliciclastic) formation, the carbonate formation is less favorable to the mineral sequestration of CO2. In sandstone and carbonate formations, the presence of Fe-bearing siliciclastic and/or carbonate is more favorable to the H2S mineral trapping.