Geochemical appraisal of crude oils from Niger Delta Basin, Nigeria: insights from β-carotane, rearranged hopanes, tricyclic terpanes, tetracyclic terpanes, and phenyldibenzofurans

β-carotane, rearranged hopanes, tricyclic and tetracyclic terpanes, and phenyldibenzofurans are important constituents of petroleum. To date, however, there has been only limited data on tricyclic and tetracyclic terpanes from the Niger Delta crude oils while β-carotane, rearranged hopanes, and phenyldibezofurans have not been reported. This study explored the geochemical significance of β-carotane, rearranged hopanes, tricyclic and tetracyclic terpanes, and phenyldibenzofurans in the Niger Delta crude oils within the context of their origins, depositional environments, and thermal maturities. These data indicate that the crude oils were derived from source rocks with significant terrestrial organic matter and a low contribution of marine organic matter. These rocks were deposited under oxic to suboxic conditions in a lacustrine to fluvial/deltaic environments within the early oil window to the peak of oil generations based on the abundance of the biomarkers. However, the phenyldibenzofuran-based and rearranged hopane-based maturity ratios showed no correlations with the already established maturity ratios, implying that thermal maturity is not the significant factor influencing the relative abundance of these compounds in the Niger Delta crude oils. This study showed that β-carotane, rearranged hopanes, and tricyclic and tetracyclic terpanes can be used to determine the origin and depositional conditions of the crude oils from the Niger Delta Basin, Nigeria.