Abstract
The Nubian Sandstone Aquifer (NSA) is the main freshwater resource in many parts of the Western Desert of Egypt including the Bahariya Oasis which attracted considerable attention during the recent decades. We determined several petrophysical parameters for the aquifer systems in the Bahariya Oasis using resistivity and gamma-ray logs. Geophysical logs recorded at 24 wells in the Bahariya Oasis are used to calculate the vertical thicknesses, total and effective porosities, permeability, shale volume, rock and formation water resistivities, and the total dissolved solids (TDS) in the different sandstone aquifers and shale beds. The logs of ten deep wells drilled in the northern part of the Bahariya Oasis enabled us to identify three aquifer zones separated by two shale beds. Only one aquifer and a shale bed are detected in the southern part of the oasis due to the limited number and the shallow penetration of wells. The shallow aquifer, referred here to as sand I, is detected in all wells with an average thickness of 184 m, moderate/high total and effective porosities, and low amount of total dissolved solids. The shale volume in the sand I aquifer increases towards the northeast but is low in the central and western parts of the Bahariya Oasis. The total dissolved solids are also low especially in the south; hence, this zone represents a suitable aquifer in the entire Bahariya Oasis. Being consistent with previous hydrogeological studies, our results indicate that the NSA in the southwestern part of the Bahariya Oasis contains potential lower-TDS shallow freshwater reserves compared to the aquifer of the northeastern part of Bahariya.