Sequence stratigraphy and reservoir quality of the Gulf of Suez syn-rift deposits of the Nukhul formation: Implications of rift initiation and the impact of eustacy and tectonic on deposition

Abstract

The Nukhul Formation represents the sediments deposited during the earliest phase of the syn-rift period in the Gulf of Suez rift. It is the primary hydrocarbon reservoir for fifteen fields in the region. However, the timing of rifting needs to be better constrained, and the influence of local tectonics and global eustatic sea-level fluctuations on reservoir quality and deposition is still being determined. This research aims to establish a stratigraphic sequence framework, determine the age of the Suez Rift commencement, use changes in paleobathymetry, and assess reservoir quality. The methods employed involve the analysis of four boreholes in the Abu Rudeis-Sidri field, incorporating biostratigraphy, well-logs, and 3D seismic data. The integrated paleo-structure and biostratigraphic analyses indicate that the beginning of rifting in the Gulf of Suez occurred at 23.53 Ma at the first common occurrence (FCO) of Trilobatus primordius. The paleobathymetric analysis of the Nukhul Formation reveals deeper paleo-water depths during certain intervals, indicating deposition during a phase of high subsidence and rift-climax. The Nukhul stratigraphic sequence reflects sea-level changes leading to shifts in accommodation, and facies changes, erosion, and sequence formation during the late Chattian and early Burdigalian stages. However, the reservoir characterization of the Nukhul Formation is significantly affected by various factors, including cementation, pore system properties, sediment sorting, rift system geometry, and relative sea-level fluctuations. These factors must be carefully considered in any regional exploration or development efforts. The study also reveals that tectonic activity played a role in forming fault-bounded basins, and eustatic sea-level changes influenced the rate and timing of sediment accumulation. These findings can aid in predicting the distribution of the Nukhul sedimentary deposits and improve the ability to explore and develop their resources.