The Western Desert versus Nile Delta: A comparative molecular biomarker study

• Two major oil families related by age and source rock depositional environment.
• Late Cretaceous/Tertiary oils are associated with abundant terrestrial organic matter.
• Jurassic or older oils are presumably generated from a mixed terrestrial/marine source.
• Oleanane, HBI, NDR and thermal maturity are the correlation keys.
• Non-routine analyses such as CSIA can distinguish Mesozoic from Tertiary oils.

The Western Desert and the Nile Delta are prolific petroleum-producing basins; the correlation and matching between their petroleum systems have been briefly studied.Overall, geochemical and biological marker analyses of twelve crude oil and condensate samples taken from seven oil-gasfields located in the Nile Delta and the Western Desert basins of Egypt, were effective in identifying and geographically defining two major oil families related by age and source rock depositional environment. These samples were classified, respectively, as Late Cretaceous/Tertiary and Jurassic–Early Cretaceous. The source rocks giving rise to the Late Cretaceous/Tertiary oils are associated with abundant terrestrial organic matter. The source rocks giving rise to Jurassic–Early Cretaceous oil are presumably generated from a mixed terrestrial/marine source. Meanwhile, the Western Desert oil samples show prominent C30 steranes, elevated C27 monoaromatic steroids, and a distinct homohopane distribution, suggesting this oil type is derived from a more marine-influenced source rock than terrigenous-sourced oil in the Nile Delta.The most crucial geochemical fingerprinting biomarkers that have been used to differentiate between Nile Delta and the Western Desert oil are oleananes, highly-branched isoprenoids (HBI), sterane isomerization, 24-norcholestanes, aromatic steroid hydrocarbons and C30 24-n-propylcholestanes.