Source Rock Characterization-Dependent Biomarker Distributions of Crude Oils in the Southern Giant Oilfields of the Gulf of Suez Province, Egypt

Mohamed Abdel-Aziz Younes¹ and Paul Philp^2
1 Geology Department, Faculty of Science, Alexandria University, Egypt
² University of Oklahoma, Norman, OK

Depositional environments and maturation assessments of source rocks from the southern Gulf of Suez have been evaluated dependent the biomarker and carbon isotopic characteristics of crude oils derived from a variety of source rock types and geological ages. Two oils families were identified and referred to as types A and B. Type A oils were characterized by a predominance of oleanane and relatively low gammacerane concentration suggesting that this group of oils was derived from a terrigenous organofacies source rock with a significant angiosperm land plant input deposited within the marginally mature syn-rift Lower Miocene Rudeis Shale. On the contrary, type B oils were distinguished by a predominance of gammacerane and relatively low oleanane concentrations suggesting they were generated from the mature marine carbonate source rocks within the Upper Cretaceous Brown Limestone and Middle Eocene Thebes Formation. Maturity parameters based on various sterane isomerisation distributions and aromatic sulfur compounds such as 4-MDBT/1-MDBT, 4,6-/1,4-DMDBT, 2,4-/1,4-DMDBT and the DBT/Phenanthrenes further support the higher thermal maturation level for type B oils compared to the type A oils. The biomarker variability among the two oil groups presumably reflects the hypothesis that there exist's two source rock types, which in turn the presence of two independent petroleum systems for oil generation, maturation and entrapment consistent with the pre-rift and syn-rift megasequences of the Gulf of Suez.