Biomarker-Based Classification of Crude Oils from Niger Delta Depobelts: Implications for Source Rock Discrimination (Akata vs. Agbada).

This study investigates the molecular geochemistry of crude oils from different depobelts within the Niger Delta Basin using biomarker parameters derived from gas chromatography–mass spectrometry (GC–MS). The aim is to classify oil families and discriminate between source rocks, particularly the Akata and Agbada Formations. Key biomarker indices, including pristane/phytane (Pr/Ph) ratios, hopane distributions, Ts/Tm ratios, and sterane compositions, were analyzed to evaluate depositional environments, organic matter input, and thermal maturity. Results indicate that the oils are predominantly of marine origin, with a minor terrigenous component, as evidenced by low Pr/Ph ratios and the dominance of C₃₀ hopanes and extended homohopanes (C₃₁–C₃₅). Thermal maturity parameters suggest that the oils fall within the peak to late oil generation window. Variations in biomarker distributions across depobelts reflect differences in source input and depositional settings. The study successfully distinguishes oils derived from the Akata Formation, characterized by strong marine signatures and high maturity, from those of the Agbada Formation, which show variable terrestrial–marine input and variable maturity levels. These findings demonstrate the effectiveness of biomarker geochemistry in oil–source correlation and provide valuable insights for hydrocarbon exploration in the Niger Delta Basin.