Abstract
Kareem Formation is one of the most important hydrocarbon reservoirs in the Gulf of Suez. It contributes significantly to the total Egyptian oil production; therefore, the current work is to emphasise the influence of siliclastic facies types and their diagenetic processes on the reservoir quality of the Kareem Formation. A comprehensive log and core analyses were used to determine both the petrophysical and petrographical characteristics. Three classic facies have been identified: two sandstone facies with reservoir potential and one shale facies. Facies I is coarse-grained sandstone with high-angle cross-bedding, distributary/braided channel deposits on the active part of a mid-submarine fan lobe and is represented by beds of (Shagar Member). Facies II is fine-grained sandy beds represented by low-angle crudely, cross-bedded sandstone encountered in the Rahmi Member. Facies III is mainly shale and recorded in the Rahmi clastic zone. Petrographically, the quartz arenite microfacies are dominant in the Shagar sand zone and show the highest potential zones in the Kareem Formation. On the other hand, quartz lithic arenite and calcareous lithic arenite constitute the major microfacies in the Rahmi clastic zone and show the lowest reservoir quality. The main diagenetic processes that enhance the sandstone reservoir intervals of the Kareem Formation are the microfracturing of mineral grains and the dissolution of both feldspar and carbonate cement. In contrast, the amount of cementing materials, particularly authigenic carbonate and clay cements, led to diminishing of the reservoir quality of the studied Kareem Formation.