Thermodynamic Models for the Prediction of Petroleum-Fluid Phase Behaviour

Ecole Nationale Superieure des Industries Chimiques, Universite de Lorraine 

Not only do oil and gas engineering systems handle very complex mixtures, but they also operate within exceptionally wide ranges of pressure and temperature conditions. Extremely low temperatures are required in liquefied natural gas (LNG) applications, while very high temperatures are needed for thermal cracking of heavy hydrocarbon molecules. Between these two extremes, hydrocarbon fluids are found underground at temperatures that can reach 90 °C or more, while surface conditions can hover around 20 °C. Pressure can vary from its atmospheric value (or lower in the case of vacuum distillation) to a number in the hundreds of MPa. Due to their complexity, multi-family nature and ample range of conditions, petroleum fluids undergo severe transformations and various phase transitions which include, but not limited to, liquid-vapour, liquid-liquid and liquid-liquid-vapour. 

The goal of this chapter is to present and analyse the development of Van der Waals-type cubic equations of state (EoS) and their application to the correlation and prediction of phase equilibrium and volumetric properties. A chronological critical walk through the most 

Some words about cubic equations of state History 

It appears that the pressure results from the addition of a repulsive term P = RT / (v — h) and an attractive term =-afv. Writing the critical constraints (i.e. that the critical isotherm has a horizontal inflection pwint at the critical p oint in the P-v plane), it becomes possible to express the a and h parameters with iesp)ect to the experimental values of Tc and Pc, resp. the critical temperature and paessure  

---

Thermodynamic Models for the Prediction of Petroleum-Fluid Phase Behaviour... 

---