Comparison between experimental data and aqueous-phase fugacity model for hydrate prediction

Accurate prediction of gas hydrate-phase equilibria has been difficult for systems containing electrolyte and non-electrolyte inhibitors, especially at high-pressures. For the last few years, new hydrate equilibria data have been published for such systems together with a new model for predicting gas hydrate equilibria. aper compares gas hydrate-phase equilibria predictions with published data for systems containing methanol and sodium chloride. Predictions are made from a simplified version of the model recently published by Ballard and Sloan, which uses separate equations of state for the hydrocarbon, hydrate and aqueous phase. predictions have been compared with data measured between 1 and 70 MPa and up to a combined inhibitor concentration of 29 mol%. The model predicts the data from three different experimental groups on average within 11% error in pressure. Both the data and model predictions show that hydrate equilibrium curve slope dP/dT increases with increasing inhibitor concentration. This effect is more pronounced in the model predictions than the data. concluded that the simplified model discussed here predicts current data for hydrate equilibria with mixed inhibitors with reasonable accuracy, but more high-pressure hydrate data are needed to resolve differences between model and data for high concentrations of inhibitor. Use of the full model by Ballard and Sloan is still recommended though, especially for predictions of sII hydrates.