Subsidence and Sedimentation Rates of the Beni Suef Basin, Egypt: Insights From the Burial and Thermal History Modeling

The Beni Suef Basin, a rift basin in north-central Egypt, was formed in response to the NeoTethys and Atlantic oceans opening and the associated tectonic motion between Africa and Eurasia during the Early Cretaceous. It is bisected by the Nile Valley into the East and West of the Nile Provinces (EON and WON) and comprises a mixed siliciclastic-carbonate succession ranging from the Albian to the Oligocene.

Burial and thermal history modeling was performed to investigate the subsidence and sedimentation rates in the context of the tectonic evolution of the basin. Tareef-1x well from the EON and Fayoum-1x well from the WON were selected for this study, where the input data and the boundary conditions were incorporated based on the available well reports and literature.

The results show that during the Albian syn-rift phase, sedimentation was initiated slightly later with low burial rates of about 33 m/My in the EON compared with high sedimentation rates of about 210 m/My in the WON. The post-rift phase was characterized by rapid thermal subsidence accompanied by relatively moderate sedimentation rates of around 117 m/My in the EON and 97 m/My in the WON. By the Late Cretaceous, an erosional uplift occurred and culminated through the entire Paleocene resulting in the removal of some parts of the Late Cretaceous Khoman Formation from both sides of the basin. Subsidence had resumed during the Eocene due to extensional tectonics with elevated average sedimentation rates of approximately 145 m/My in the EON compared with relatively low sedimentation rates of approximately 74 m/My in the WON. These phases are interrupted by a hiatus period during the Late Eocene-Oligocene in the EON, while the WON has continued subsiding and resulted in the deposition of the Oligocene Dabaa Formation. The Miocene thermal uplift represents the last tectonic phase, which led to significant erosion from the Eocene Apollonia Formation in the EON and the Oligocene Dabaa Formation in the WON.

The implications on the hydrocarbons potentiality were also investigated through the thermal history modeling, where we found that the Turonian Abu Roash “F” source rock exists in the early oil window with a transformation ratio of about 20 % across the entire basin. While the Lower Kharita shale source rock, which is only deposited in the WON, has reached the late oil window with a transformation ratio of approximately 70 %.

In summary, sedimentation began slightly later in the EON (Middle to Late Albian) compared with the WON (Early Albian), where the paleo basement high has hindered the deposition of the Early Albian Lower Kharita shale in the EON compared with the WON, thus caused a delay at the beginning of the deposition. The different sedimentation rates across the basin could be attributed to various factors such as the amount of sediment supply, climate conditions, different slopes across the basin, and /or lithology, which need to be addressed in further research.