Measurements and modeling of high-pressure O₂ and CO₂ solubility in brine (H₂O + NaCl) between 303 and 373 K and pressures up to 36 MPa

Knowledge of the solubility of oxygen in natural water, which is generally saline, is important for several scientific and engineering fields. Applications such as geological storage of gas (containing O₂, e.g., flue gas) or energy (compressed air energy storage) operate at high pressure. However, to date, there is no high-pressure O₂ solubility data in brine, which has led researchers to develop models to predict this important property. To overcome the lack of data, solubility of O₂ in brine has been measured using two different techniques, at molalities between 0.5 and 4 mol/kg_w (NaCl), temperatures between 303 and 373 K, and pressures up to 36 MPa. In order to validate the experimental methods, measurements of the solubility of CO₂ in a highly concentrated brine (6 mol/kg_w of NaCl) at temperatures between 303 and 373 K and pressures up to 39.5 MPa were performed also in this work. These measurements allowed the evaluation of existing models such as the well-known Geng and Duan model and the model recently developed by Zheng and Mao (ZM). The e-PR-CPA, Søreide-Whitson, and geochemical models used in our previous work were also used to process the new data. These last three models have been parameterized on measured and reported literature O₂ solubility data, and new optimized parameters of the ZM model have been proposed. These models reproduce the effect of temperature, pressure, and NaCl concentration on solubility with an average absolute deviation less than 5% from the measured data.