Hydrocarbon Generation and Basin Modeling of the 'Jurassic-Cretaceous Succession in the Abu Gharadig-Shushan Basins, Northern Western Desert, Egypt .

摘要

Thermal maturity and hydrocarbon generation modeling of the Jurassic-Cretaceous succession in the Abu Gharadig-Shushan basins showed that the dark shale of the Khatatba Formation (Middle Jurassic) and the shale of the Alam El-Bueib Member (L. Cretaceous) are considered the most potential source rocks for hydrocarbon generation. Biomarker distributions and stable carbon isotope composition of crude oils recovered from Abu Gharadig-Shushan oilfields revealed two oil families of different geochemi-cal characteristics. Family-I represents crude oil produced from the Bahariya Formation (Upper Cretaceous) and Family-II is the crude oil produced from the Cretaceous formations (Alam El-Bueib and Abu Roash-F members), supporting the idea of the presence of two different source rock intervals for oil generation and entrapments with two levels of thermal maturation. Two different shale source rock types were considered in the 2-D modeling of source rock maturation and hydrocarbon generation and each of them was assigned a specific generation potential. Organic-rich shale source rock with excellent potential to generate and expel oil and gas is present in the Middle Jurassic Khatatba Formation that entered the late mature stage of oil and gas generation window at a vitrinite reflectance of more than 1.35 Ro% during the Late Cretaceous. Meanwhile, a good to fair source rock of the Alam El-Bueib Member is located within the early to mid mature stage of oil generation window at a vitrinite reflectance of 1.0 to less than 1.35 Ro% during the Late Eocene. These source rocks could have charged stratigraphic as well as structural traps that play an important role during the hydrocarbon accumulation. The biomarker variability among the two oil families presumably reinforced the hypothesis regarding the presence of two independent petroleum systems for oil generation, maturation and entrapment in the Abu Gharadig-Shushan basins.