Occurrence and Distribution of Pyrene and its Derivatives in Crude Oils and Source Rock Extracts from Niger Delta, Nigeria

Crude oils and source rocks from the Northern and offshore depobelts of the Niger Delta basin, Nigeria have been characterized based on the distribution of pyrene and its derivatives by gas chromatography-mass spectrometry. Moreover, the crude oils have been characterized by the dominance of pyrene over fluoranthene while fluoranthene generally predominated over pyrene in the rock samples. Also, 4-methylpyrene has been the dominant compound among the methylpyrene isomers in the crude oils and source rocks while benzo[a]fluorene (BaF) predominated over benzo[b]fluorene (BbF). The pyrene distribution shows that the crude oils and source rocks have been formed from mixed sources (terrestrial and marine) but with higher inputs from terrestrial organic matter. The maturity dependent parameters which have been computed from pyrene distributions indicate that the oils have been thermally matured while the rock samples have been within immature to early oil window maturity status. Finally, the crude oils and the sources of source rocks, and thermal maturities have been further confirmed by other well-established parameters computed from saturate and aromatic parameters and vitrinite reflectance.
At the end, it has been found out that the abundance and distribution of pyrene, and its derivatives have been found to be effective in determining the origin and thermal maturity of crude oils and source rocks in the Niger Delta Basin.