The fugacity calculation results will directly affect the prediction accuracy of the phase equilibria of gas hydrates. Based on the Chen-Guo model

four equations of state (RK

SRK

PR and PT EOS) are used to calculate the fugacity

then to predict the phase equilibria of methane

ethane and carbon dioxide gas hydrates in different temperature ranges

respectively. Results show that for pure water system the model with RK EOS is most suitable for predicting the phase equilibria of methane hydrate

while PR EOS is more suitable for the prediction of ethane and carbon dioxide hydrates. For ice system

SRK EOS is the most suitable for methane hydrate but the prediction below 218.2 K is the main reason for the low prediction accuracy. PR EOS suits the prediction of ethane hydrate and the prediction accuracy for the case below 230.2 K still needs to be improved. And RK EOS is suitable for predicting carbon dioxide hydrate

the prediction accuracy will be improved further if the prediction results below 270.7 K can be much closer to the experimental data.