THE SUBSURFACE GEOLOGY AND RESERVOIR CHARACTERISTICS OF THE UPPER BAHARIYA RESERVOIR IN THE HAYAT/YASSER OIL FIELD, NORTHWESTERN DESERT, EGYPT

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.