Depositional History of the West Nile Delta- Upper Oligocene to Upper Pliocene*

Abstract

Several Nile Delta publications in recent years have used very good quality data to illustrate and discuss depositional systems in great detail. The data presented in this study adds regional context to the common understanding. Recently acquired 3D seismic surveys in the onshore, offshore and transition zone were interpreted as part of a Nile Delta Prospectivity Study. Well data from more than 40 years of hydrocarbon exploration were intergrated. These data provided the basis for a regional understanding of the sedimentary and structural evolution during the past 30 million years. A robust biostratigraphic zonation scheme was adopted and consistently implemented to more than 60 wells throughout the study area. Integration of seismic surfaces and facies analysis using a variety of seismic attribute extractions and sedimentary facies, calibrated by well data and stacking pattern analysis, were done on a sequence by sequence level. A seismic facies catalogue was generated for different depositional environments. Paleo-depositional systems maps were constructed and serve as snapshots, mostly of lowstand systems, for each timeframe. These maps illustrate the regional depositional history for the West Nile Delta. They reflect, for instance, the relation between lowstand prograding deltas and relict shelf breaks at type one unconformities to the generally more distal and productive offshore slope settings. The different positions of the mapped relict shelfbreak and facies distribution in different sequences reflects the evolution of th