THE MIOCENE KAREEM FORMATION IN THE SOUTHERN GULF OF SUEZ, EGYPT - A REVIEW OF STRATIGRAPHY AND PETROLEUM GEOLOGY

The middle Miocene Kareem Formation in the Gulf of Suez is lip to 500- m thick, and is composed of interbedded sandstones, shales and carbona tes; minor anhydrites are present in the lower part of the formation. The siliciclastics were deposited in alluvial and submarine fans build ing out from the rift shoulders, while the carbonates and anhydrites w ere precipitated in local lagoons as a result of sea-level fluctuation s. The formation is divided into the Rahmi and overlying Shagar Member s, and is Langhian to Serravallian in age. Three main sandstone lithol ogies have been identified (quartz arenites, arkoses and quartz wackes ) each of which differ in their content of secondary minerals, cements and matrix types, reflecting their differing depositional settings an d diagenetic histories. The sandstones of the Kareem Formation form on e of the most prolific reservoir lithologies in the Gulf of Suez oil p rovince, and produce oil and/or gas in almost 30 fields. These sandsto nes have a good reservoir quality throughout the basin with gross-and net-pay thicknesses of up to 235 m and 195 m, respectively. The sandst ones' porosity varies from 9% to 33%, and permeabilities range from 20 md to 730 md Reservoir quality depends on the sandstones' shaliness, diagenetic history and degree of compaction. The sandstones still have high exploration potential particularly in the southernmost portion o f the Gulf of Suez where they are extensive and thick but where there has been little drilling. Organic-rich shales within the Kareem Format ion constitute potential source rocks for oil and gas, especially in t he southernmost part of the Gulf of Suez where the geothermal gradient is high and where, according to previous studies these sediments are located within the oil-generation ''window''.