Gas compressibility factor explicit correlations for range of pseudo reduced temperature and pressure

Abstract

The most essential properties of a natural gas are the thermodynamic property such as Gas compressibility factor (Z), and it is used to quantify the level of deviation of a real gas from an ideal gas at a certain temperature and pressure. Based on the importance of this property, many means have been proposed to derive the Z factor parameter such as through Experimental analysis, Equation of state and Empirical correlations. For correlations, both implicit correlations and explicit correlations have been modelled in order to best measure this deviation. However, the explicit correlation has not considered pseudo reduced temperature of less than 1. This study analyzed previous correlations in order to gain knowledge on their working conditions, limitations, and methods of derivations. A quick and dependable approach in modeling Z factor correlation from the pseudo reduced temperature and pressure was adopted. The study proposed a new and accurate correlation that can be employed in daily calculations that is an extension of Beggs-Brill Correlation (BBC), Azizi-Behbahani-Isazadeh Correlation (ABIC) and Sanjari-Lay Correlation (SLC). The composite correlation technique led to the derivation of 3 new equations for gas compressibility factor. A regression analysis was run to see how far the new correlations deviated from the previous ones and two of the correlations proved to be conforming to the Standing and Katz model as well as the other base correlations used. The result obtained from the 3 new correlations were then validated with field data. The type of natural gas worked with was a binary mixture of methane and decane components. After the evaluation, it was seen that the new correlations worked accurately and should be included in future important calculations.