The Ghadames basin is the second-largest oil-producing basin in Libya. One of the gas and oil producers in the Ghadames basin is Al Wafa Field. The purpose of this investigation is to assess the Aouinet Uennin Formation (F3) "B" sandstone in the Al Wafa field, Ghadames Basin, Libya, specifically in the A37-NC169a well. The well-logging analysis revealed that the water saturation of the upper-most F3B sandstone is less than 30% reflecting its superior reservoir potentiality. The findings showed that the relative permeability to water as well as the water cut value equal zero while the relative permeability to oil is 100%, which confirm that this interval is at irreducible state. The applied J function technique approved the high-quality reservoir performance of F3B Upper Unit 1 with low computed J values (< 3.48) reflecting the low capillary pressure and the presence of mega- pores. The calculated irreducible water saturation is 22%, which matches the obtained core data.