Seismic Expression of Miocene and Pliocene Proximal Lowstand Composite Sequences, Offshore and Onshore West Nile Delta, Egypt

Gerhard J. Brink², Stiig Brink-Larsen², Bruce Finlayson², Hamsa El-Khawaga¹, Axel Kellner¹, and Hesham Maksoud^1
1Exploration, RWE Dea, Cairo, Egypt
²Consultant, Cairo, Egypt

To date Pliocene and Miocene gas discoveries and production in the Western Nile delta are largely restricted to distal slope depositional settings. Recent work suggests there may be unrealized potential in proximal composite lowstand sequences.
Our study included more than 3000 square kilometers of interpreted 3D seismic and a robust petrophysical and biostratigraphy database using 30 wellbores. Seismic reflection configurations and stratigraphic sequences were interpreted on a 200 by 200 meter grid.

The interpretations reveal a number of interesting features in proximal depositional settings. East-west strike oriented relict shelf breaks at type 1 unconformities contrast with the generally consistent northwest trending slope channels. Successive sequences repeditatively exhibit upper slope proximal canyons and incised channels that trend northeast to due north at the sequence boundary surface. Depositional slope channels are disassociated from the initial erosive unconformity and trend northwest for the remainder of lowstand and transgressive systems tract deposition.

High frequency sequences overprint fundamental (third-order) sequences during lowstand deposition. This is observed in the proximal setting where the transgressive surface at the top of the initial lowstand prograding wedge translates basinward into a basal bounding type 1 unconformity. Associated with this higher order sequence boundary is another lowstand prograding wedge and slope fan. This configuration may occur multiple times in a single third-order sequence and is common throughout the Miocene and Pliocene succession. In this proximal setting high sediment input rates appear to be a major control whereas tectonic instability adds complexity to the more distal slope settings.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery