Thermodynamic Modeling of CO2-N2-O2-Brine-Carbonates in Conditions from Surface to High Temperature and Pressure

Abstract

Nitrogen (N2) and oxygen (O2) are important impurities obtained from carbon dioxide (CO2) capture procedures. Thermodynamic modeling of CO2-N2-O2-brine-minerals is important work for understanding the geochemical change of CO2 geologic storage with impurities. In this work, a thermodynamic model of the CO2-N2-O2-brine-carbonate system is established using the “fugacity-activity” method, i.e., gas fugacity coefficients are calculated using a cubic model and activity coefficients are calculated using the Pitzer model. The model can calculate the properties at an equilibrium state of the CO2-N2-O2-brine-carbonate system in terms of gas solubilities, mineral solubilities, H2O solubility in gas-rich phase, species concentrations in each phase, pH and alkalinity. The experimental data of this system can be well reproduced by the presented model, as validated by careful comparisons in conditions from surface to high temperature and pressure. The model established in this work is suitable for CO2 geologic storage simulation with N2 or O2 present as impurities.