Improved Characterization of Heptane Plus Fraction of Niger Delta Light Crudes

Accurate determination of molecular weight of heptane plus(C⁷⁺) fractions is essential in reliable phase behavior calculations and compositional EOS modeling studies. Empirical correlations provide cheaper alternatives in time and cost, to obtaining reliable molecular weight data than by experiments, though with compromised accuracies.

Several empirical correlations developed to predict molecular weight of C⁷⁺ fractions of petroleum were reviewed. A new correlation for calculating molecular weight of heptane plus fractions of light crudes was developed from a database compiled from Niger Delta fields for over 1,200 light crude oil assays, conventional PVT reports, and literature data. The correlation was developed using rational multiple regression analysis method.

The new correlation's performance was compared with five others which do not depend on boiling point temperatures. Results showed that the new correlation has superior performance with the lowest absolute average and relative mean square errors. The new correlation had an average relative error of 8.15%, root mean square error of 0.09% and correlation coefficient of 0.955.