oa An Efficient Multicomponent Gas-Brine Equilibrium Model for CO2 Storage Simulation

We developed a lightweight yet accurate multicomponent gas-brine model that does not require updates of fugacity and activity coefficients in flash calculations. The model is applicable over a temperature range of 273–373 K, pressures up to 71 MPa, and salinities up to 6 m NaCl. It includes 12 gases: H2, N2, O2, CO, NO, CO2, H2S, SO2 and CH4 - nC4H10. By employing composition-independent K-factors, the model can be solved by a Rachford-Rice solver, significantly reducing flash calculation costs and offering a considerable speed advantage for CO2 storage simulation in the presence of impurities. Model predictions are benchmarked against experimental data, demonstrating sufficient accuracy. We present example calculations for mutual solubility of various binary gas-water mixtures, solubility in ternary mixtures, and CO2 solubility in brine. This model is readily applicable to CO2 storage and other subsurface gas storage applications, including H2 storage.