Organic Geochemical Characterization of Crude Oils from Western Sirt Basin, Libya
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Biomarker, Crude Oil, Organic Matter, Sirt Basin, Thermal Maturity
Abstract
The Sirt Basin contains most of Libya's producing oil fields. It is located in northern Libya, south of the Gulf of Sirt in the Mediterranean Sea. The main aim of this study is to determine the type of organic matter, depositional conditions of the source rocks, and thermal maturity of the crude oil based on organic geochemical parameters. The organic geochemical analyses were determined by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Six crude oil samples were collected from the Ghani and En Naga oil fields in the western Sirt Basin. The results suggest that all of the oils are derived from source rocks rich in marine organic matter deposited under oxic to suboxic saline conditions. Based on biomarker ratios such as pristane/phytane, isoprenoids/n-alkanes, carbon preference index (CPI), 22S/22S+22R homohopane ratio, diasteranes/steranes, gammacerane index, C29 20S/20S+20R, C29/C30 hopanes, and Ts/Ts+Tm, which are used as source and correlation parameters, it proposed that these oils are in an early mature stage and could be sourced from similar marine shale except for one sample which may indicate more salinity of source rocks.
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