The litho-stratigraphic cross sections, thickness variations and lithofacies of the Upper Bahariya
reservoir (Upper Bahariya Member) are discussed to distinguish the shape, the extent of sedimentary
basins and the environment of deposition. The studied Upper Bahariya reservoir shows that the Upper
Bahariya Member top is coming higher at Yasser-06 well than the other three wells, which lies in the
northeastern part of the study area. Furthermore, the maximum thickness of the Bahariya Formation
occurs at Hayat-12, while the minimum thickness occurs at Hayat-17 well. The facies triangle lithologic
model of the Upper Bahariya Member shows, the predominance of calcareous shale facies in most of the
studied wells which change to shaley sand in the central part at Hayat-12 and Hayat-14 wells. These facies
reflect a shallow marine environment grading from tidal-dominated estuarine channels to wave-dominated
shoreline associating with lagoons or bays. The petrographic analysis shows that, there is a variation in the
reservoir quality based on the detrital clay components and diagenetic processes.