Occurrence of Biphenyl and Alkylbiphenyls in Source Rocks from Tertiary Niger Delta Basin, Nigeria.

Abstract

Source rocks from the offshore Niger Delta basin, Nigeria have been analyzed by gas chromatography-mass spectrometry (GC-MS) in terms of their thermal maturity, based on the distribution of biphenyl and its derivatives. The source rocks were characterized by the dominance of C₂-biphenyl over other alkylated homologues. 3-methylbiphenyl predominated over other methylbiphenyl isomers in rock samples. 3,3’- dimethylbiphenyl occurred as the most abundant compound among the C₂-biphenyl compounds in the rock samples while 3,5,4-trimethylbiphenyl dominated over other C₃-biphenyl compounds in the source rocks. 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 source rocks have wide variations in maturity status and that the rock samples are within immature to oil window maturity status 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 source rocks in the Niger Delta Basin.

Keywords: Biphenyls, alkylbiphenyls, source rocks, Niger Delta, maturity