Characterization of Lower Cretaceous organic-rich shales from the Kom Ombo Basin, Egypt: Implications for conventional oil generation

Abstract

• The shales of the Kom Ombo Formation are organic-rich sediments, with TOC value of up to 6.61 wt.%. • The organic facies are predominantly of Types II and II/III kerogen. • Kom Ombo shales were deposited in a marine under anoxic environmental conditions. • The shales reached peak oil-window and generated commercial amounts of oil. This study uses organic geochemical and petrographic analyses to characterise the organic-rich shales from the Lower Cretaceous Kom Ombo Formation in the Kom Ombo Basin. The overall results show that the Kom Ombo shales are considered to have good petroleum source rock potential with total organic carbon (TOC) content > 1 wt % and hydrocarbon yields of up to 27.62 mg hydrocarbons/g rock. Based on lipid biomarker ratios and carbon isotopes, the Kom Ombo shale contains a blend of organic matter derived primarily from algal marine and other aquatic organic matter, with some terrigenous land plants, deposited under anoxic conditions. These findings of organic matter (OM) input and depositional conditions are consistent with the high TOC content of up to 6.61 wt. % and mainly Types II and II/III kerogen, with small amounts of Type III kerogen, thus yielding both oil and gas, with oils of high to low wax contents. The geochemically determined dominance of oil generation potential is in agreement with the findings of considerable concentration of fluorescent liptinite macerals. The chemical and optical maturity results show that the majority of the examined Kom Ombo shale samples have entered the main stage of oil generation, exhibiting a range of early-mature to late-mature. Therefore, as highlighted in this study, the oil generation potential of the Kom Ombo shales may represent future conventional petroleum exploration opportunities.