Burial History and Hydrocarbon Generation Modeling of the Jurassic-Cretaceous Formations in the Alamein-Shushan Basins, Northern Western Desert of Egypt

Maturity and petroleum generation modeling of the Jurassic-Cretaceous succession in the Alamein-Shushan basins shows that the dark shale of Khatatba Formation (Middle Jurassic) and the shale of Alam El-Bueib Formation (L. Cretaceous) are the most potential source rocks for oil and gas generation. Detailed biological marker and stable carbon analyses of crude oils representing Alamein, Yidma, North Ras Qattara and Shushan fields revealed two oil families of different geochemical characteristics. Family-I representing crude oil produced from Bahariya Formation (Upper Cretaceous) and Family-II is the crude oil produced from of the Lower Cretaceous formations (Aptian Dolomite, Razzak Sand and Alam El-Bueib) strength the idea of presence of two different source rock intervals for oil generation and entrapments with two levels of thermal maturations. Two different marine shale source rocks were considered in the 2-D modeling of source rock maturation and hydrocarbon generation and each source rock was assigned specific generation potential. Organic rich source rock with excellent potential to generate oil is present in the Middle Jurassic Khatatba Formation entered the overmature to late mature stage of oil and gas generation window at vitrinite reflectance between 1.0 and 1.3 Ro% during the Late Cretaceous. Meanwhile, a good to fair source rock of Alam El-Bueib Formation located within the early to mid mature stage of oil generation window at vitrinite reflectance 0.6 to 1.0 Ro% during the Late Eocene. These source rocks could have charged stratigraphic as well as structrural traps that play an important role during the hydrocarbon accumulation. The biomarker variability among the two oil families presumably reinforced the hypothesis that the presence of two independent petroleum systems for oil generation, maturation and entrapment in the Alamein-Shushan basins.  

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California