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Thermal Maturity Assessment and Characterization of Crude Oils in the Eastern Niger Delta

Abstract

Seventeen crude oil samples from producing wells in the eastern, western and central parts of the Joint Venture (EMJV) area, operated by an international oil company in the Eastern Niger Delta were analyzed for their thermal maturity status. The study is aimed at establishing maturity trends across the JV and identifying the maturity parameters that can reliably be used for maturity assessment of the JV area. The study involved gas chromatography (GC), open column liquid chromatography and gas chromatography mass spectrophotometry (GC/MS) for biomarker analysis. Pristane/Ph ytane ratio obtained from the oils ranges between 2.3 and 5.1, which indicates that the oils are derived from organic matter of mixed terrestrial/marine input. Sterane and hopane based maturity parameters could not be used reliably to assess the maturity of crude oils as some have been affected by source lithology and others have already reached their respective equilibrium values before the oil window. Maturity parameters from aromatic hydrocarbons worked better for the oils. Maturity increased from east to west area. 3MP/4DMBT, Tm/Ts, MPR, MAC21/TAC21+MAC28 and MPDF worked better for the thermal maturity assessment of crude oils from the study area.