The analysis is carried out in an HP 5890 GC with a Flame Ionization detector. (GC-FID). Suitable capillary columns (length, stationary phase) are used, according to the scope of the analysis. Individual light hydrocarbons are determined based on retention times and Kovatz response indices. The composition of the whole oil is presented in terms of pseudo-compound groups based on n-alkanes. For heavy oil/extract samples internal standard is used to estimate the un-eluted fraction