The Lower Miocene Nukhul Formation was deposited early during early stages of Gulf of Suez rifting. Outcrop of this Formation at Gebel el Zeit, Egypt is up to 100 m (328 ft) thick and consist of lower sandstone-dominated and upper carbonate-dominated units. Samples were collected from the Nukhul Formation outcrop to describe the lithofacies, mineralogy, and petrographic characteristics to better understand the hydrocarbon reservoir potential for the unit. The investigations showed that the lower part of Nukhul Formation at North Gebel el Zeit consists of poorly sorted, dolomitic sandstone and sandy dolomite which were deposited in a shallow-marine setting. The presence of polycrystalline and crushed quartz grains in Nukhul strata indicates that these strata were sourced by recycled sediments associated with local uplift tied to rifting. The upper Nukhul consists of dolomitized carbonates with preservation of primary textures; primary limestone depositional textures include the following: intraclast packstone, rudstone, and coral-algal boundstone, wackestone, and grainstone with minor floatstone. Carbonate rock strata were deposited in shallow marine, peritidal to subtidal environments that developed on fault-block highs. The presence of zoned saddle dolomite suggests some component of fault-controlled fluid flow. The reservoir characteristic of the Lower Miocene Nukhul Formation at the Gebel el Zeit indicates favorable properties for reservoir development in both the lower siliciclastic-dominated dolomite and the upper dolomitized carbonate portions of the formation.
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