3D Hydrogeophysical Modeling and Groundwater Potentiality Assessment of the Nubian Sandstone Aquifer, El Farafra Oasis, Egypt

The Nubian Sandstone Aquifer System (NSAS) represents the principal groundwater resource in Egypt’s Western Desert, sustaining agricultural and socio-economic development in arid environments. Increasing groundwater abstraction in the El Farafra Oasis requires a robust understanding of aquifer heterogeneity and hydraulic behavior to support sustainable management. This study integrates borehole geophysical logs, lithological data, and hydrogeological measurements from 37 groundwater wells to characterize the petrophysical and hydraulic properties of the NSAS. The effective porosity, shale volume, formation factor, permeability, hydraulic conductivity, transmissivity, and storativity were estimated using physics-based petrophysical models calibrated against available pumping-test data. A high-resolution 3D geostatistical workflow was applied to map the spatial variability of aquifer properties while respecting well control and stratigraphic boundaries. The results reveal pronounced lateral and vertical heterogeneity within the NSAS controlled by depositional facies architecture, shale intercalations, and structural features. Formation factor values inversely correlated with shale volume, indicating high-quality reservoir zones in the northeast. Effective porosity values (~ 0.17–0.34) indicate good to excellent aquifer quality, particularly in the northeast, while the permeability (k > 1000 mD) and hydraulic conductivity (K > 9 m/d) typify highly productive sandstone aquifers. Transmissivity commonly exceeds 2,000 m²/d and storativity ranges from 10⁻⁴ to 10⁻³, consistent with confined to semi-confined NSAS conditions reported in previous studies, indicating that El Farafra Oasis provides a representative analog for regional groundwater behavior. The proposed workflow represents a transferable methodology for upscaling well-based petrophysical information into regional groundwater flow models, supporting sustainable groundwater management and long-term planning across the broader NSAS.