Miller, Sean B.¹, George Pemberton¹, Fred Wehr² 
(1) University of Alberta, Edmonton, AB 
(2) Apache Egypt, Cairo, Egypt

ABSTRACT: Sedimentology and Ichnology of the Upper Cretaceous (Cenomanian) Upper Bahariya Formation in the Khalda Concession, Western Desert, Egypt

Since the first discovery of onshore oil in Egypt, reserves exceeding 15.7 billion barrels of oil equivalent have been found. A significant portion of the production originates from the Upper Cretaceous (Cenomanian) Bahariya Formation, particularly in the Khalda Concession of the Western Desert of Egypt. Detailed core studies applying both ichnology and sedimentology suggest that these strata were deposited in an estuarine setting. 
The Upper Bahariya Formation was deposited on a broad tidally-influenced ramp on the southern margin of the Tethys. It is primarily comprised of thin, sand-poor parasequences that correlate regionally. The system is dominated by glauconite rich, clastic lithologies interbedded with some carbonate facies. Sedimentary structures such as tidal mud doublets, flaser and wavy bedding, convolute bedding, slump structures, small scale ripples and planar laminations, along with Glossifungites surfaces and a mixture of trace fossils from the Skolithos and Cruziana ichnofacies, suggest deposition in a tidally influenced, relatively low energy, restricted marine setting. Very fine-grained sandstones in the upper portion of the Upper Bahariya are interpreted as thin bayhead delta, distributary mouth bars and rare, localized, channel fill sandstones. Modern day analogues of several tidally influenced estuaries such as the Gironde Estuary, Willapa Bay, and Cobequid Bay provide many useful insights into the processes operating during deposition of the Bahariya Formation. 
By incorporating different aspects of geology such as sedimentology and ichnology, higher-resolution interpretation of this depositional system may significantly increase recoverability and extend production of the Bahariya reservoir. 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.