The Lower Miocene Nukhul Formation (Gulf of Suez, Egypt): microfacies and reservoir characteristics

Mostafa Temraz,Henning Dypvik

doi:10.1007/s13202-017-0386-3

Mostafa Temraz, Henning Dypvik

Open Access

https://doi.org/10.1007/s13202-017-0386-3

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Abstract

The Lower Miocene Nukhul Formation was deposited during early stages of Gulf of Suez rifting. Outcrop of this formation at Gebel el Zeit, Egypt is up to 100 m (328 ft) in thickness and consists of lower sandstone-dominated and upper carbonate-dominated units. Samples were collected from the Nukhul Formation outcrop in order to describe the lithofacies, mineralogy, and petrographic characteristics to better understand the hydrocarbon reservoir potential of 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 original textures; primary limestone depositional textures include 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. Reservoir characteristics 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.

Highlights

The major heavy oil accumulations in the Issaran field, Gulf of Suez, are trapped in Miocene fractured carbonate and siliciclastic reservoirs with average API between 10 and 12 (Joshi et al 2010)
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 studied Lower Miocene Nukhul Formation is characterized by a consistent upward succession from basal quartz sandstone to shale, grading into sandy dolomite and later highstand marine carbonates (Fig. 4)

Summary

Introduction

The major heavy oil accumulations in the Issaran field, Gulf of Suez, are trapped in Miocene fractured carbonate and siliciclastic reservoirs with average API between 10 and 12 (Joshi et al 2010). The early and middle Miocene syn-rift sedimentary sequences are dominated by terrigenous clastics from unroofing of the uplifted rift flanks or shoulders. These successions are among the most prolific petroleum reservoirs in the Suez province. A thorough understanding of their depositional history and controlling factors such as rift shoulders relief, the timing of unroofing, local paleogeography, and sedimentary deposystems is required for establishing an accurate development of known reservoirs and prediction in ongoing exploration

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