In this study, the petrophysical characterizations of the subsurface sandstone Plio-Pleistocene reservoir in the offshore Nile Delta Sienna field has been defined based on the well log data available in three wells. The detailed petrophysical analysis revealed the presence of a gas-bearing sandstone interval ranged from 1 to 12 m of net pay zone with good reservoir characteristics in terms of good porosity (26%), low shale volume (16%) and water saturation (66%). The clay mineral identification plots indicate that, the Sienna reservoir was deposited mostly in fluvial to shallow marine environments according to the presence of glauconite, mica, illite, chlorite and montmorillonite as dominant clay minerals. The analysis of pressure data is concerned mainly with locating the different fluid contacts and determining the pressure gradients of the gas-bearing zone. Very close pressure regimes are detected for the investigated gas anomaly throughout the study area. Pressure gradient of gas ranges from 0.078 to 0.084 psi/ft while, the water gradient is 0.46 psi/ft, also NMR reveals that the pay zones (Sand-1, Sand-2, and Sand-3) have good petrophysical parameters for production, free fluid with good effective porosity and good permeability.