Mechanical stratigraphy of sedimentary section - implications for petroleum exploration, Gulf of Suez, Egypt
Mechanical response of sedimentary units to extension varies, depending on their rheology. In the Gulf of Suez, knowledge of the mechanical stratigraphy assures better control for seismic interpretation, structural analysis, and delineation of possible hydrocarbon traps. Recent field studies and seismic analysis allow delineation of the structural response of a range of prerift and synrift lithologies. The prerift section is divided into three major mechanical/stratigraphic units: Precambrian basement, Nubian sandstone, and Cenomanian through Eocene shallow marine platform rocks. Single fault planes in the basement are expressed in the overlying Nubian sandstone as closely spaced parallel faults and fractures. In contrast, the inhomogeneous Late Cretaceous-Paleogene section of alternating brittle and ductile beds drapes over the underlying normal faults. The synrift section may comprise three mechanical/stratigraphic units: (1) early Miocene carbonates and clastics; (2) middle-late Miocene evaporites; and (3) Pliocene-Recent clastics. The lower synrift rocks respond to faulting much like the Cenomanian-Eocene units. The evaporite section acts as a major detachment zone, with underlying faults dying out upward. Onshore, faults in the more brittle passive cover rocks sole into the underlying evaporites. Thus, faults at the surface may be entirely decoupled from master faults in the early synrift and prerift strata. Mechanicalmore » response in the synrift section is complicated by syntectonic processes such as growth faulting, compaction, and lateral facies changes.« less