Print this pageRift Basin Sequence Stratigraphy Models: Parts A and B, Gulf of Suez Miocene Syn-Rift Deposits
DOLSON, JOHN C., OSAMA EL GENDI, MOHAMMED RAMZY, BRAD STEER, MIKE ZINGER, IHAB GMFAR, HAMDI CHARMY, FARID-ABU-SHADI, MIKE SCHLORHOLTZl, JIM MIKA; and MAGDI FATHALLA
Miocene syn-rift outcrop exposures in the Gulf of Suez, Egypt, reveal reservoir-scale seismic changes which, when coupled with subsurface data, provide a basis for developing predictive sequence modeling within a rift setting. 3D seismic and biostratigraphic details provide a chronostratigraphic framework for reservoir prediction. Rift initiation phase sequences are characterized by incised valley fill, estuarine and offshore deposition in an overall transgressive environment. The geometries are wedge shaped and dendritic. They can be characterized as "transgressive systems tracts" within the context of Vail-type models or as "genetic sequences" within the context of Galloway models. Capping time breaks are generally transgressive in nature. During rift climax, water deepening events create highstand systems tracts which trap reservoirs along the basin flanks. Seals form in basin centers. The capping time break (T20, or "mid-clysmic" unconformity) is a true Vail-type sequence boundary. The overlying S30 sequence represents a lowstand wedge associated with basinward translation of facies. However, unidirectional downlap associated with termination of the lowstand wedge occurs synchronously with onlap around intrabasinal highs and thick wedges of continuously deposited shale in intrabasinal lows.
In general, "passive margin" sequence models can be applied within a rift only on gently dipping basin flanks. Elsewhere, pattems of downlap, onlap and continuous deposition are contiguous features which form fundamental geometries characteristic of rift sequences. Tectonic and sediment supply controls overwhelm those of eustasy in this basinal setting. Examples of delineation of new plays and proven new field reserves found by application of new concepts using these rift basin sequence models will be illustrated.