Jurassic Rift Architecture in the Northeastern Western Desert, Egypt

Wescott, William A.¹; Atta, Mahmoud ²; Blanchard, David C.²; Cole, Roger M.¹; Georgeson, Steven T.¹; Miller, David A.¹; O'Hayer, Walter W.¹; Wilson, Amanda D.¹; Dolson, John C.³; Sehim, Adel ⁴
(1) El Paso Exploration and Production Company, Houston, TX. (2) El Paso Egypt Production Company, Cairo, Egypt. (3) DSP Geosciences and Associates, LLC, Coconut Grove, FL. (4) Cairo University, Cairo, Egypt.

During the last decade the Egyptian Western Desert has emerged as major hydrocarbon province in North Africa. Much of the exploration success has resulted from the recognition and exploitation of the Jurassic hydrocarbon system and associated reservoirs. The Western Desert has a complex, poly-phase tectonic history starting in the Mesozoic with Jurassic rifting. The Early Jurassic extensional event occurred during the separation of the North African and European plates and resulted in a broad zone of rift basins cross cutting the Precambrian basement and, in some areas, pre-existing Paleozoic basins on the Neotethyan continental margin of North Africa. Conventional wisdom based upon interpretations of gravity and magnetic data suggested that the overall orientation of the Jurassic rift-bounding faults trend in a NE-SW direction. However, recent studies based upon regional 3-D and 2-D seismic interpretation and well data suggest that the Jurassic rifts have more of an East-West orientation in the western portion of the Western Desert. Regional interpretations of merged 2-D/3-D seismic data in the northeastern portion of the Western Desert (South Alamein, South Mariut, and Tanta concessions and adjacent areas) indicate that this east-west rift trend continues into these areas. It is only along the coastal areas, where the structure fabric is dominated by the Rosetta fault that the NE-SW trend is dominant. Furthermore, these data indicate that in this region asymmetrical half-grabens are separated by stable basement blocks. Apatite fission track data from recent wells that were drilled to basement indicate that the Sheiba High and Shaltut-Mekdam basement blocks formed during the Early Jurassic and were not significantly affected by subsequent tectonic events. Basinal areas of various depths and sizes are separated and isolated by these high blocks by a complex set of rift transform zones and breached relay ramps. Accurately mapping and understanding the geometries and distribution of these rifts and associated high blocks is crucial for modeling hydrocarbon systems and predicting hydrocarbon occurrences in this region of the Western Desert as the Jurassic exploration play extends to the east.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.