--> ABSTRACT: Source Rock-Dependent Biomarker Properties and Stable Carbon Isotope Composition of Crude Oils from West Bakr Fields, Onshore Gulf of Suez, Egypt: A Case Study, by M. A. Younes; #90906(2001)

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M. A. Younes

Geology Department, Faculty of Science, Moharrem Bek, Alexandria University, Alexandria, Egypt. E-mail: [email protected].

ABSTRACT: Source Rock-Dependent Biomarker Properties and Stable Carbon Isotope Composition of Crude Oils from West Bakr Fields, Onshore Gulf of Suez, Egypt: A Case Study

Four representative crude oil samples from three different pay zones (Ayun, Yusr and Bakr members) of Lower Miocene age from West Bakr Fields K, H and M, Gulf of Suez, Egypt were analyzed to evaluate the source rocks and their depositional environments. The saturate and aromatic fractions were subjected to a variety of organic geochemical analyses including Gas Chromatography (GC), Gas Chromatography-Mass Spectrometry (GC-MS), trace element analyses (V, Ni, Co, Cr, Fe, Mg, Mn, Ca and Zn) and stable carbon isotopic composition δ13C. The geochemical characteristics and biomarker properties of the studied crude oils show no obvious variations. All the studied crude oil samples are of naphthenic base and possess similar values of V/Ni ratio, suggest that the studied crude oils might be derived from the same source rocks. Moreover the ratios of Ts/Tm (<1), Oleanane index (>30%) and gammacerane index (>20%) reflect a marine environment with minor terrestrial higher plants input from Tertiary source rocks deposited in high salinity waters with less reducing conditions. The enrichment of stable carbon isotopic composition δ13C to the saturate fraction ranges from (-29.1 to -29.35 0/00 PDB); and to the aromatic fraction ranges from (-28.35 to -28.60 0/00 PDB) is observed. The isotopic values together with the calculated canonical variable (CV) of the studied crude oil samples <0.47, which further support that the crude oils of West Bakr Fields were generated from marine source environment. The achieved results obtained from the geochemical characteristics of the studied crude oils suggest marine environment with minor terrestrial higher plants input from source rocks of Tertiary age. These are likely to be interval within the Lower Miocene Rudeis shale and Eocene Thebes Formation carbonate rocks where the vertical and horizontal migration caused the oil to be entrapped within the sandstone of Lower Miocene age.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado