Numerical prediction of phase equilibrium conditions of gas hydrates up to 200 MPa in the presence of sodium and calcium chloride solutions

Abstract

The occurrence of natural gas hydrates has both beneficial and negative practical implications. Nowadays, the most numerical studies in gas hydrates formation field were limited to a pressure of 74 MPa. However, these components are abundantly formed at permafrost and under the seafloor in which the pressure exceeds 100 MPa. In this study, the prediction of equilibrium conditions of gas hydrates was investigated numerically in pure gas and gas mixture up to 200 MPa. The inhibition of hydrates formation was examined by using NaCl and CaCl2 at different molar fractions. The Lee-Kesler-Plocker equation of state was selected as the most adequate, to predict gas hydrate stability limits, compared to other numerical approaches. The modeling results indicate that our model is in good agreement with experimental findings up to 200 MPa, but due to the lack of data in literature the maximum pressure compared was 163.25 MPa for gas mixture in pure water. The salt inhibition investigation also shows a good accuracy of our model at molar fractions less than 0.05 in both pure gas and gas mixture. It can be concluded that this model permits to study the stability limits of hydrates in wide range of gas composition and chloride salt solutions.