Petroleum Geochemistry and Potential Source Rock Correlation in the Shushan Basin, North Western Desert, Egypt

Abstract

Shushan Basin is one of the coastal basins in the northern part of the Western Desert of Egypt that is characterized by its high oil and gas potential. Rock-Eval pyrolysis, biomarker properties, and stable carbon isotopes of crude oils and related source rocks revealed two types of extracts, A (Alam El-Bueib and Abu Roash-G) and B (Khatatba Formation), and two families of crude oils, I and II of similar δ13C carbon isotope composition. Fair correlation can be made between type A extracts abd Bahariya crude oils, where the similar biomarker properties among them, as C30 moretane ratio < 10% and [20S/(20S+20R)] C29ααα sterane < 0.5, suggest that these crude oils were generated from terrestrial land plants influenced at a low thermal maturity level. Meanwhile, type B extracts and Alam El-Bueib crude oils are genetically related and bear the same terrestrial source input generated at a higher thermal maturity level than those of Alam El-Bueib and Abu Roash–-G source rocks as evidenced from higher C 30 moretane ratio > 10% and [20S/(20S+20R)] C 29ααα sterane > 0.5. Organic rich rocks with excellent potential to generate mainly oil are present in the Middle Jurassic Khatatba Formation that entered the late mature stage of oil and gas generation window at vitrinite reflectance measurements between 1.0 and 1.3 Ro% during the Late Cretaceous. Meanwhile, a good to fair source of rocks of Alam El-Bueib and Abu Roash-G Member are located within the early to mid-mature stages of the oil generation window between vitrinite reflectance 0.5 to 1.0 Ro%, at time varying from Late Cretaceous to Late Eocene. The similarities in biomarker characteristics of crude oils and source rock extracts, in addition to the geologic occurences, are related to the stratigraphic as well as structural entrapment elements, which play an important role during the hydrocarbon accumulations in Shushan Basin.