Accurate prediction of H2S and CO2 containing sour gas hydrates formation conditions considering hydrolytic and hydrogen bonding association effects

An elegant thermodynamic model, considering the hydrogen bonding association effects in fluid phases by using cubic-plus-association equation of state (CPA EOS), electrostatic effects of hydrolytic dissociation of H2S and CO2 acidic gases according to the modified Pitzer–Debye–Hückle (PDH) model and an improved two step gas hydrate formation mechanism using Chen–Guo model is presented for accurate prediction of the pure and mixed sour gas hydrate formation conditions. The proposed CPA/Electrolyte/Chen–Guo model is quite reliable over wide ranges of temperatures, H2S and CO2 concentrations. The overall average absolute deviation between the predicted and measured sour gas hydrate equilibrium dissociation pressures regarding 149 data points comprising pure and multi-component sour gas mixtures, is about 3.32% which is considerably lower than the other thermodynamic models. The proposed model outperforms the other alternatives both in accuracy and generality and can be employed for accurate design of sour natural gas management and flow assurance systems and gas hydrate energy storage processes in oil and gas industries