ABSTRACT
The majority of PVT calculations carried out for oil and gas mixtures are based on a cubic equation of state. This type of equations dates back more than 100 years to the famous van der Waals equation (van der Waals, 1873). The cubic equations of state most commonly used in the petroleum industry today are very similar to the van der Waals equation, but it took almost a century for the petroleum industry to accept this type of equation as a valuable engineering tool. The first cubic equation of state to obtain widespread use was the one presented by Redlich and Kwong in 1949. Soave (1972) and Peng and Robinson (1976 and 1978) further developed this equation in the 1970s. In 1982 Peneloux et al. presented a volume-shift concept with the purpose of improving liquid density predictions of the two former equations. The increased use of cubic equations of state seen over the past 30 years is greatly due to the availability of affordable computer power that has made it possible, within seconds, to perform millions of multicomponent phase equilibrium and physical property calculations using an equation of state as the thermodynamic basis. This chapter presents some of the most popular cubic equations of state. Chapter 6 describes the application of cubic equations of state in phase-equilibrium (flash) calculations, Chapter 8, the derivation of physical properties from cubic equations of state, and Chapter 16, the application of cubic equations of state to mixtures with water and other aqueous components.
