Prediction of equilibrium conditions for gas hydrates in the organic inhibitor aqueous solutions using a thermodynamic consistency-based model

Abstract

Considering organic inhibitor plays a great role in preventing hydrate formation in oil and gas industry by shifting the hydrate phase equilibrium conditions, it is necessary to study the effects of organic inhibitors on the phase behavior of gas hydrates. In this study, a thermodynamic consistency-based model was developed to predict the phase equilibria of gas hydrates in methanol (MeOH), ethanol (EtOH), monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG) and glycerol (GLY) solutions with concentrations of 5.44 wt%~ 65 wt%, respectively. The Chen-Guo model was applied to hydrate system. Compared with the original Hu-Lee-Sum correlation, a modified HLS type correlation that additionally considers the slight effect of temperature on calculating the activity of water was proposed. The prediction accuracy was characterized by the average absolute deviation in temperature (AADT). Results show that for CH4 hydrate the Chen-Guo model coupled with HLS correlation performs as good as the original HLS correlation and PVTSim. The corresponding AADT for each organic inhibitor can be further decreased by at least 20.95% when using the Chen-Guo model coupled with the modified HLS type correlation. Besides, this modified model also shows a better performance in predicting the phase equilibria of C2H6 and CO2 hydrates in the presence of these organic inhibitors than the Chen-Guo model coupled with HLS correlation do.