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Regional Geometry and Hydrocarbon Plays of Jurassic to Early Cretaceous Continental Rifts in Northeast Africa

Bosworth, William 1; Clare, Alan 1; Phinney, Eric 1; Thompson, Melissa 1; Towart, Jeffrey 1; Helgeson, Daniel 1; Artigas, Gabe 1; Maher, Tom 1
1 Exploration, Apache Egypt Companies, Cairo, Egypt.

There is good stratigraphic evidence that the opening of Neotethys commenced in northernmost Tunisia-Libya-Egypt in the Permian to Early Triassic. Subsequent to this initial rifting sequence, an extensive system of generally east-west trending rift basins and probable transcurrent fault systems developed in-board of the continental margin through what is now the southern Sirt basin complex in Libya and the Western Desert of Egypt. Similar to the rupture of Apulia from Africa, Cyrenaica and land to the east started to break away from Africa during the Middle Jurassic (Bajocian-Callovian) but failed. This resulted in the formation of large structures and deposition of shallow marine to deltaic source rocks in the Abu Gharadig, Shushan, and Faghur basins of Egypt. Lacustrine and estuarine source rocks were subsequently deposited during the Early Cretaceous (Aptian-Albian) in the Hameimat and Sarir troughs of Libya. The Jurassic reservoir/source pair has resulted in the largest hydrocarbon accumulations found to date in the Western Desert, and Jurassic to Early Cretaceous reservoirs continue to provide large discoveries in the southern Sirt basins. Complex stratigraphic-structural traps are generally encountered in both areas. These plays are also potentially important targets along the relatively unexplored, offshore continental margin and in the deep basin axes of the northern Sirt troughs. Heat flow varied dramatically between different basins and largely controlled where oil versus gas would be found. Fully exploring these hydrocarbon systems will require integration of both refined regional tectonostratigraphic models and detailed reservoir scale analysis of syn- and marginal-rift reservoir strata. Very large-scale 3D seismic datasets and the drilling of exploratory wells in excess of 5,000 m are providing new insights into these under-explored rock sequences.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009