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According to published geological studies, there are two theories regarding the origin of petroleum in the Gulf of Suez area. One theory advocates that the majority of the oil accumulations in this region originate from two different source rocks: Eocene limestones and Miocene marls. The other theory states that only Miocene marls and shales of the Gharandal and Ras Mallah groups are the source rocks. The present study is a geochemical evaluation of Eocene limestones as potential source rocks. The geological samples studied comprised eight oils from six major accumulations in Miocene, Eocene, and Cretaceous formations, and 15 core samples from Eocene limestones in the region. Samples were analyzed for their petroporphyrin types and distributions using established analytic l techniques that included uv/vis, mass spectrometry, and high pressure liquid chromatography (HPLC). These techniques permitted the determination of several petroporphyrin parameters such as yield, distribution, and the ratios of nickel to vanadyl complexes and of DPEP to etio types. These geochemical parameters were then employed for oil-oil and oil-source rock correlations of the samples analyzed.
In general, the oils had higher porphyrin contents, higher vanadyl to nickel porphyrins ratios, and lower DPEP to etio ratios compared to the shales. Most importantly, however, the porphyrin distribution (HPLC fingerprints) for the oils were significantly different from those of the shales. The shale samples showed three different fingerprints, one of which is uncommon of petroporphyrins found in petroleum and related bitumens. Among the oils, two different fingerprints were observed, regardless of their geological age. Although these observations suggest more than one source for the oils, they could not corroborate the the assumption that the Eocene formation is a potential source rock. Other geochemical implications of the findings will also be discussed.
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