The phase behavior of CO2-CH4-H2S-brine systems is of importance for geological storage of greenhouse gases (CCS) and enhanced oil recovery (EOR). In such projects, reservoir simulations play a major role in assisting decision makings, while modeling the phase behavior of the relevant CO2-CH4-H2S-brine system is a key part of the simulation. There is a need for an equation of state (EOS) for such system which is accurate, wide application range (pressure, temperature and aqueous salinity) computationally efficient and easy for implementation in a reservoir simulator. In this work, corresponding to the CO2-CH4-H2S-brine system, mutual solubility models are established by two different ways: (1) a cubic model based on the revision of the Søreide-Whitson EOS is used for fugacity calculation of both aqueous and non-aqueous phases (φ-φ model); (2) Peng-Robinson model is used for the fugacity calculation of non-aqueous phase and Pitzer activity model is used for the aqueous phase activity calculation (φ-γ?model). Both model can accurately reproduce the existing experimental data to high temperature (250 °C), high temperature (1000 bar for CO2and CH4solubility, and 200 bar for H2S), and high salinity (6 molal of NaCl in solutions). The φ-γ model has slightly better accuracy. Computation efficiency of the two models is investigated. The φ-γmodel has obvious better computation efficiency, and can be a good choice for the implementation in numerical simulators.
Li, J., Wei, L., & Li, X. (2014). Modeling of CO2-CH4-H2S-brine based on cubic EOS and fugacityactivity approach and their comparisons. In Energy Procedia (Vol. 63, pp. 3598–3607). Elsevier Ltd. https://doi.org/10.1016/j.egypro.2014.11.390