Occurrence and Distributions of Biphenyls and Alkylbiphenyls as Indicators of Maturity in Crude Oils from the Tertiary Niger Delta Basin, Nigeria

Abstract

Crude oils from the Northern and offshore Niger Delta basin, Nigeria have been characterized by gas chromatography-mass spectrometry (GC-MS) in terms of their thermal maturity, based on the distribution of biphenyl and its derivatives. The crude oils were characterized by the dominance of C2-biphenyl over other alkylated homologues. 3-methylbiphenyl predominated over other methylbiphenyl isomers in the oils samples. 3,3’-dimethylbiphenyl occurred as the most abundant compound among the C2-biphenyl compounds in the oils samples while 3,5,4-trimethylbiphenyl dominated over other C3-biphenyl compounds in the oils. The distributions and abundance of the biphenyl and alkylbiphenyls were found not to be influenced by source facies and thermal maturity. The maturity dependent parameter computed from alkylbiphenyl distributions (MBpR, DMBpR-x and DMBpR-y ratios) indicated that the oils have wide variations in maturity status and that the oil samples are within oil window and this is further supported by other maturity parameters computed from the saturate and aromatic biomarkers. This study showed that the abundance and distribution of biphenyl and its derivatives can be used for thermal maturity of crude oil in the Niger Delta Basin.