Application of the gamma distribution model to molecular weight and boiling point data for petroleum fractions

This paper applies the gamma distribution model for describing both the molar and boiling point distributions of heptanes-plus (C7+) fractions. The three-parameter distribution model has been fit to TBP (true boiling point) data from forty-four samples of stabilized petroleum liquid (stock tank oil and condensate), obtained from separation of reservoir fluids. An excellent fit was achieved for both molar and boiling point distributions, though molar distribution seems to be more accurately described by the distribution model. Two of the parameters, α and η, were correlated and fit to empirical equations for both molar and boiling point distributions. Since the third parameter, β, is defined in terms of α,η, and either average molecular weight or boiling point, it appears that a generalized correlation for molar and boiling point distributions may exist. We have not developed such correlations in this work, but our results provide the necessary groundwork for further research.