A SAFT Equation of State for the H2S-CO2-H2O-NaCl system and applications for CO2 - H2S transportation and geological storage

When H2S is co-injected with CO2, we need to know thermodynamic properties and phase equilibria for the CO2-H2S-H2O-NaCl system in order to evaluate the storage capacity, optimal transportation and injection conditions, potential for pipeline corrosion, and increased risk of storage and leakage. Here, we summarize the results of the phase equilibrium and densities for CO2-sequestration related systems from a thermodynamic model that is based on statistical associating fluid theory equation of state. The proposed thermodynamic model can be used to represent equilibrium compositions in both phases (H2O-rich/aqueous phase and gas-rich/non-aqueous phase) and the density at equilibrium or in the one phase region. The effect of H2S impurities on the properties of CO2 streams and on the CO2 solubility and the corresponding aqueous solution density can be predicted to provide a knowledge base for both transportation and geological storage. In addition, as other ions such as Ca, Mg, K and SO4 have been taken into account in our model, the properties for brine in geological reservoirs in addition to simplified aqueous NaCl solutions can also be predicted. The equation of state from this study can be incorporated into reservoir simulators to model the separation of phases in multi-phase flow and fluid reactions with reservoir rocks. (C) 2013 The Authors. Published by Elsevier Ltd.