Introducing a New Depositional Model as an Aid to Hydrocarbon Exploration On & Offshore North Sinai - Egypt

By

 Maher H. Ayyad¹, Mohammed Darwish², Adel Sehim²

(1) BG - Egypt, Cairo, Egypt (2) Cairo University, Cairo, Egypt

 Sinai Peninsula has long been classified as a passive shelf margin, progressively subsiding northward, with a sedimentary wedge on-lapping the basement rocks to the south. The study area has undergone a multi-phase tectonic history, resulting in multi-depositional schemes: a) An Early Mesozoic extensional phase, b) Late Cretaceous- Oligocene inversion and c) Neogene regional subsidence. During Triassic- Early Cretaceous, NW-SE transtensional stresses initiated regional NE-SW fracturing systems that evolved into segmented faults. Asymmetric half grabens subsequently developed with depocenters along the bounding faults. Fault polarities played a significant role in the sedimentation processes. NW-dipping faults generated sub-basins with escarpment margins, while SE-dipping faults formed sub-basins with hinged margins, with accommodation zones in between. Sediment distribution and stacking patterns within each half graben are controlled by :1) Sub-basin geometry and orientation, 2) Rate of subsidence and sediment supplies and 3) Sea level fluctuation. Specific depositional styles have been recognised to be analogous to known models. During the inversion phase, the sub-basins reversed rotation around the hinge margins, followed by erosion of crestal parts. Sea level rise brought the entire region under shallow marine conditions in Late Cretaceous-Eocene, allowing carbonates and clastics to cover the truncated Syn-rift sequence. Facies such as sand-prone fan deltas, slope and sea floor fans and reef deposits were developed. Full understanding of detailed geologic analysis is highly important to minimize exploration risks, especially in such severely deformed and complex areas.