In this study, the accurate values of compressibility factor for several Iran natural gases are predicted according to AGA-8 equation of state (EOS). First, the reliability of this equation of state was evaluated. For this purpose, the predicted results were compared to the experimental values of Z-factors for methane. It is shown that, this EOS has an excellent agreement with experimental data, especially at severe conditions. Furthermore, the superiority of this EOS compared to the other frequent EOSs in gas industries such as Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) was disclosed. The linear correlation coefficients between the calculated results and experimental data have been determined for each equation of state. The AGA-8 equation of state has the most correlated linear coefficient (r>0.9999) with the experimental data for all conditions. So, this equation of state could be considered as a very accurate equation of state to predict the natural gas Z-factor and other thermodynamic properties.
