Structural and facies modeling of the Lower Cretaceous Alam El Bueib reservoirs in the Shushan Basin, Western Desert, Egypt

Abstract

The Qasr oil and gas field is located in the eastern part of the Shushan Basin in the northern Western Desert of Egypt. Sandstones of the Lower Cretaceous Alam El Bueib Formation are the main oil-bearing reservoirs in the field, and these reservoirs cannot be seismically detected. Consequently, modeling is important to predict the extension of the reservoirs. The present study adopts two types of modeling: structural and facies. Structural modeling is the incorporation of interpreted faults, horizons, and zones into a three-dimensional (3D) grid, while facies modeling distributes lithologic facies within the previously constructed 3D structural grid. All available geological information is utilized in facies modeling, including lithological interpretations from well logs, and sedimentary core and ditch cutting descriptions from mud logs. The structural analysis of the Alam El Bueib Formation in the Qasr Field showed several E-W to WNW-ESE fault systems. The geologic structure, combined with stratigraphy and facies architecture, establishes the framework for traps in this field. Lithology interpretation using electric well logs and mud logs showed four main facies: (1) channel sand, (2) flood plain siltstone, (3) lagoonal shale and mud, and (4) marine carbonates. Facies modeling of the six major units that comprise the Alam El Bueib Formation show variable sand channels deposited in fluvial to mixed deltaic and tidal environments. These channels are oriented N-S to NE-SW and form 20 to 100-ft-thick sandstone reservoirs.