The Occurrence and Distribution of Oleanane Biomarkers in Crude Oils as an Index

Oleanane biomarkers are age diagnostic indicators and source of organic matter input in fossil fuels which can unravels the stage of development of a petroleum system in the petroleum generating rock. Representative samples of crude oil obtained from two separate fields in the southern Nigeria province were evaluated geochemically using Gas Chromatography–Mass Spectrometry. The data obtained from the analysis of the crude oil samples revealed the presence of the 18α (H)-oleanane biomarker. The occurrence of 18α (H)-oleanane biomarker in the Niger Delta oils provides diagnostic evidence on age and organic matter source in all samples. The results of the Oleanane indices for all samples ranged from 0.32 to 1.03 (> 0.30), which suggests that the oils are from Tertiary age source rocks with resilient terrestrial organic matter input. Only crude oil sample KD03 had an Oleanane index of 0.03 (< 0.30), which shows crude oils derived from a late cretaceous or younger age with some marine input. The presence of 18α (H)-Oleanane in Niger Delta crude oils is a confirmation of an earlier postulation that most crude oils from the region had a greater terrestrial organic matter input.