Evaluation of Equations of State at High Pressure for Light Hydrocarbons

Equations of state are used for predicting reservoir fluid properties in a large range of pressures and temperatures. The choice of an equation depends on the type of component, the pressure and temperature ranges and the property to be computed. In this work, four equations are tested (Peng-Robinson, Simonet-Behar Rauzy, Lee and Kesler, Chain of Rotators) for three different thermodynamic properties (molar volumes, isobaric and isochoric residual heat capacities). The accuracy of the calculations for alkanes from methane up to n-butane are expressed as deviation maps in (P,T) coordinates. The analysis is mainly focused on the behavior in the high pressure and high temperature regions. The modified version of the Lee & Kesler method provides good density results for hydrocarbons up to n-butane, but is not to be used for heavier components