Pseudocritical properties based

The volume of the gas in the reservoir may be calculated using the compressibility equation of state. This calculation is based on 1 lb mole of gas using Equation 3-39. The composition of the gas in the reservoir calculated by the recombination method can be used to compute the pseudocritical properties so that the compressibility factor may be obtained in the same manner as illustrated in Examples 3-10 and 3-12. 

Sutton derived equations for pseudocritical properties of natural gases based on measured z-factors for 264 natural gas samples.2 He used the Dranchuk Abou-Kassem equation for z-factors and the Wichert Aziz adjustment for nonhydrocarbon components.4,7,8 Sutton s equations are... 

Reduced properties are then calculated for the mixture based on the pseudocritical properties. 

Once this function is determined, it could be applied to any substance, provided its critical constants Pc, T, and V are known. One way of applying this principle is to choose a reference substance for which accurate PVT data are available. The properties of other substances are then related to it, based on the assumption of comparable reduced properties. This straightforward application of the principle is valid for components having similar chemical structure. In order to broaden its applicability to disparate substances, additional characterizing parameters have been introduced, such as shape factors, the acentric factor, and the critical compressibility factor. Another difficulty that must be overcome before the principle of corresponding states can successfully be applied to real fluids is the handling of mixtures. The problem concerns the definitions of Pq P(> and Vc for a mixture. It is evident that mixing rules of some sort need to be formulated. One method that is commonly used follows the Kay s rules (Kay, 1936), which define mixture pseudocritical constants in terms of constituent component critical constants ... 

The Lucas rules are based on corresponding states methods. This approach estimates pseudocritical and other mixture properties fiom pure component properties, the composition of tte mixture, and mixing and combining rules defined by Lucas. The Lucas approach is the first of the correlations considered that is not interpolative, it will not result in the pnre component viscosity if the mole fraction of one component is 1 and the mole fraction of the other component is 0. The methods utilizing corresponding states are not as accurate as those based on the kinetic theory, but provide an advantage in the lack of necessity of having pure component data. 

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