Palynology and palynofacies studies of the subsurface Aptian-Cenomanian sedimentsfrom the central North Western Desert, Egypt

摘要

The lower Cretaceous sediments succession is composed of four formations in Northern Western Desert of Egypt. These formations are Alamein, Dahab, Kharita and Bahariya formations. They are considered as the main target of the oil and gas exploration in the Egyptian Western Desert. The present study investigated their thermal maturity and potentiality to generate the hydrocarbons. These were conducted by the study palynostratigraphy, palynofacies and spore coloration of samples from these formations in WD 19-2 borehole. The identified palynozones are Afropollis jardinus Acme Zone (late Albian – early Cenomanian), Araucariacites australis Acme Zone (middle Albian) and Murospora florida Acme zone (Aptian). The first zone is differentiated into two subzones, which are Elaterosporites klaszii Interval Subzone and Cretacaeiporites densimurus Interval Subzone. The palynofacies analysis revealed that the Alamein and Dahab formations are deposited in deltaic shallow marine dysoxic to anoxic environment. Kharita Formation was deposited in more proximal near shore marine environment under suboxic to oxic conditions. The Bahariya Formation was deposited in proximal near shore dysoxic to oxic marine conditions. The investigated kerogens from the Alamein and Dahab formations were gas prone type II and III, while in Kharita and Bahariya formations they were gas prone type II, III and IV. The spore color or thermal alteration index (TAI) observations indicated that the samples from Alamein and Dahab formations contain mature kerogens and can be a potential source yield hydrocarbons. The Kerogens of Kharita and Bahariya formations are immature to yield gas and are not effective hydrocarbon source.