Sequence stratigraphy and petrophysical evaluation controls on fluvial to fluvio-marine reservoirs in the syn- and post-rift sediments: Insights into in the Kharita and Bahariya Formations, West Beni Suef basin

Abstract

Hydrocarbon occurrence in rift basins is largely governed by tectonic styles and basin-fill stratigraphy, with abundant potential reservoirs found throughout the syn-rift and post-rift successions. This study conducts a sequence stratigraphic analysis and petrophysical evaluation of the Albian-Cenomanian syn- and post-rift successions in the Beni Suef (BS) rift basin. The Albian Fluviatile Kharita Formation is deposited in the syn-rift phase, while the fluvio-marine Bahariya Formation is deposited in the post-rift phase of the BS basin. The studied succession is divided into three depositional sequences: SQLKH-1 & SQUKH-2 in the Kharita Formation and SQBAH-3 in the Bahariya Formation. SQLKH-1 and SQUKH-2 are siliciclastic-dominated units developed in a long-lasting fluviatile setting with some shallow marine shale deposits in the lower levels of SQLKH-1, while the SQBAH-3 is a siliciclastic unit with carbonate interbeds developed initially in fluvio-deltaic setting and become shallow marine upwards. Petrophysical analysis has been conducted to evaluate hydrocarbon potential and reservoir characteristics of the Kharita and Bahariya formations across several wells. With effective porosity values between 0.09 and 0.14 and average shale volumes of about 0.10, the Kharita Formation exhibits good reservoir quality but limited hydrocarbon saturation, indicating potential suitability for CO₂ sequestration rather than hydrocarbon production. The Bahariya Formation demonstrates superior reservoir potential, with low shale volumes (<10%) and effective porosity ranging from 10% to 20%, highlighting its suitability for hydrocarbon exploration. The considerable variation in water saturation between wells from 25% to 75% highlights localized heterogeneity. Potential hydrocarbon accumulation zones are identified in wells with lower water saturation, like Azhar A2 and Azhar E−2X. These results highlight the importance of site-specific reservoir management to maximize production and the Bahariya Formation's superior suitability for hydrocarbon exploration when compared to the Kharita Formation.