Statistical thermodynamics of thermal diffusion factors in binary hydrocarbon mixtures – an application^*

^*This paper is submitted to the Special Issue of Molecular Physics to honour the lifetime achievement of Professor Johann Fischer.

ABSTRACT

Thermal diffusion factors play key roles in the analysis of composition variation of the mixture components in hydrocarbon reservoirs and to ensure reliable formation fluid evaluation. This paper presents the statistical thermodynamics of thermal diffusion factors of binary hydrocarbon systems using the modified theory of linear transport. The theory is revised to include the effect of pressure and unlike interaction parameters in calculating the unlike collision integrals and account for the explicit effects of the intermolecular interactions, molecular mass, energy and size parameters. The dependence of the diffusion factors on temperature, pressure and composition of the mixtures is investigated in a systematic way. Comparisons of calculated results with experimental data show that the revised theory could predict the thermal diffusion factors of binary nonhydrocarbon gas mixtures and liquid hydrocarbon mixtures very well over a range of temperature and pressure including the reservoir conditions.

KEYWORDS:

• Thermal diffusion factor
• statistical thermodynamics
• intermolecular interactions
• hydrocarbon mixtures

Acknowledgments

The author would like to thank Dr.-Ing.Habil.Rolf Lustig for contacting him to contribute this article to the special issue of Molecular Physics in honour of Professor Johann Fischer for his lifetime achievements in statistical mechanics.

Disclosure statement

No potential conflict of interest was reported by the authors.