Geochemical modeling of CO2 storage in saline aquifers: examples from Ketzin, In Salah and Snohvit storage sites
Geochemical modeling is an interesting tool to assess the geochemical behavior of CO2 in the saline aquifer, including its dissolution in the brine and its interactions with minerals. The Pitzer interaction model is rarely used for simulating CO2 geochemical behavior in saline aquifers despite the fact that more conventionally used activity models are not valid for such salinities. A comparison between calculated mineral solubility evolution with salinity versus experimental data is performed here using both B-dot and Pitzer activity models as well as six different databases. This comparison exercise shows that chemical interactions within saline solutions can only be reproduced using the Pitzer model, even though Pitzer databases are still incomplete or are not coherent for a wide range of chemical species and temperatures. The geochemical simulations of CO2 injection in Ketzin, In Salah and Snøhvit saline aquifers give divergent results using different activity models and databases. A high uncertainty on the simulation results is then linked to the database choice and this study clearly stresses the need for a Pitzer database that can be confidently used in all physical/chemical conditions found in deep sedimentary aquifers.