Compositional gradient known as a potential of vertically variations in composition (and sometimes areal changes) has a remarkable effect on reservoir management steps such as estimation of initial hydrocarbon in place, design of downstream equipments and prediction of gas–oil contact. One of the main steps in development of compositional
grading is to characterize fluid sample. In this study, compositional grading is studied in a volatile oil sample from an oil field in south of Iran. Implemented models are based on isothermal and non-isothermal, i.e., zero diffusion, Hasse and Kempers models. Results illustrated
that isothermal and zero diffusion models are in appropriate consistency with field data. Then, effect of C10? splitting on compositional grading was studied. It was shown that splitting of C10? to more pseudo-components does not have significant effect on variation in composition
of hydrocarbon and non-hydrocarbon components.