The biomarker and aromatic compounds, including polycyclic aromatic hydrocarbons (PAHs), in three oil families composed of 29 crude oils from the Gippsland Basin, SE Australia were studied using gas chromatography-mass spectrometry. Environment-related parameters, such as the Pr/Ph ratio and the gammacerane index, indicate that all the oils originated from a lacustrine/fluvial-deltaic environment with fresh water. Thermal maturity-related parameters, including aliphatic and aromatic maturity indicators (e.g. C29 sterane isomerisation parameters, alkylnaphthalene indices, and methylphenanthrene index), show that all the oils from the GA1 oil family have a similar thermal maturity in the peak-late oil window. However, oils from the GA2 and GB families vary in thermal maturity and are interpreted to be mixtures of less mature and more mature crude oils. Source-related biomarkers (e.g. isopimarane, labdane and phyllocladane) and PAHs (e.g. retene and oleanane-/ursane-/lupane-derived aromatic triterpenoids) suggest that the GA1 oils were mainly derived from source rocks rich in conifer-derived organic matter. The organic matter source of the GA2 and GB oil families included both angiosperms and gymnosperms, with a relatively stronger angiosperm contribution to the organic matter in the source rock(s) of the GB oils, based on the PAH analysis. Moreover, higher plant-derived triterpenoids can be effectively used to correlate oil families across the study area, supplementing the n-alkane carbon isotope and biomarker data of the three oil families reported previously.
- Polycyclic aromatic hydrocarbon
- Aromatic triterpenoids
- Oil-oil correlation