Fluid Phase Behavior for Conventional and Unconventional Oil and Gas Reservoirs

2.2. Cubic Equation of State (EOS)

The EOS that is cubic with respect to volume, like the Van der Waals EOS, is usually called a cubic EOS. These EOSs generally are modifications of the Van der Waals EOS. The repulsive term of most of these equations is identical with the repulsive term in the Van der Waals EOS and the attractive term is modified. The most commonly used cubic EOS is reviewed in this section.

The simplest cubic EOS is the Van der Waals EOS that originated in 1873. Van der Waals EOS is composed of contributions of repulsive and attractive terms. The Van der Waals EOS is given by:

(P+aV2)(V−b)=RT

(2.1)

in which a and b are the constants ...