In this paper, a compositional Model is proposed to calculate the phase behavior and the physical properties of condensate gases. Such a model is based on a very classical and easy to handle cubic equation of state coupled with correlations devoted to the estimation of the hydrocarbon physical properties. Moreover, to completely define the composition of the C-20+ distillation residue, three distribution functions associated with the families n-alkanes, n-alkylbenzenes, and polyaromatics are introduced. The method developed in this work shows clearly enhanced results in comparison to previously published papers in the same area.