Biomarker characteristics of the Turonian–Eocene succession, Belayim oilfields, central Gulf of Suez, Egypt

Abstract

This study assesses the hydrocarbon source rocks of the Belayim oilfields, central Gulf of Suez, Egypt. Detailed geochemical methods, including liquid chromatography, gas chromatography and gas chromatography–mass spectrometry, are used to characterize organic-rich facies of the Turonian–Eocene deposits. Crude oil samples are analyzed using C7 and stable carbon isotopes, in addition to analysis of the extracts, in order to throw light on the organic matter source, composition, and thermal maturity. The source rocks are mainly derived from algae and bacteria deposited under normal saline and reducing palaeoenvironmental conditions, with a minimal contribution from terrestrial organic and mainly clay-poor source rocks. This is evidenced by the n-alkane distribution, the pristane/phytane, homohopane, gammacerane index, the high concentration of cholestane, the presence of the C30 n-propylcholestanes and low diasteranes ratios. The source rock extracts range from immature to marginally mature, based on biomarker maturity related parameters. A similar scenario is envisaged from the crude oil samples which showed a partial positive correlation with the source rocks of the Eocene Thebes Formation, and the Upper Cretaceous Brown Limestone. Our data suggest that Turonian–Santonian Matulla Formation samples may signify the presence of some oil in the study area