Search

The Rudeis Formation represents one of the most important oil-producing reservoirs in the Gulf of Suez. This formation exhibits conspicuous lateral facies changes and therefore presents a complex exploration target due to tectonic activity. In the study area, it is composed largely of shale with a few limestone interbeds, but so far composed of fine-grained marl and sandstone. Here, we interpret the sequence stratigraphy of the Rudeis Formation at two onshore wells (Ras El-Ush-7 and Ras El-Ush 8) in the southernmost western shore of the Gulf of Suez via the integration of gamma-ray log and biostratigraphic data, in order to develop a high-resolution sequence stratigraphic model of these syn-rift rocks and determine their viability for hydrocarbon exploration. Using new biostratigraphic analysis of calcareous nannoplankton and planktic foraminifera, we verified the ages of the Rudeis successions. Our results suggest the occurrence of three Burdigalian depositional sequences (SQ1, SQ2 and SQ3), along with six stratigraphic surfaces delineating sedimentation cycles and were mainly deposited in inner shelf to upper slope settings. Each of the sequences typically contains a transgressive systems tract bounded above by a maximum flooding surface and a highstand systems tract bounded above by a sequence boundary. We further demonstrate that the variable timing in deposition and erosion of these depositional sequences were controlled by either local tectonism associated with Gulf of Suez rifting or eustatic sea-level changes. • This study offers a biostratigraphic description of the Rudeis Formation in the Ras El-Ush oilfield in Egypt. • It presents a stratigraphic record for two boreholes in the region alongside paleoenvironmental interpretations • t also presents a local reconstruction of relative sea level fluctuations for the Gulf of Suez. • It aims to obtain a more detailed geological description of the area in order to aid hydrocarbon resource exploration. [ABSTRACT FROM AUTHOR]

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. • The initiation of the Suez rift occurred 23.53 Ma based on the FO of T. primordius. • The Study revealed deeper paleodepths during intervals of high subsidence and rift climax. • Local tectonics and global sea level changes were found to control sediment deposition. • The results contribute to understanding processes shaping sedimentary basins which can guide future exploration efforts. • Findings provide insights into evolution of rift basins and factors controlling sedimentation applicable to other basins. [ABSTRACT FROM AUTHOR]