A Study of Reservoir Characteristics of Bahariya Formation, Aghar-4 Oil Field, Alamein Basin, Western Desert, Egypt.

Abstract

The Upper Cretaceous Bahariya Formation is one of the most significant hydrocarbon reservoirs in the Western Desert over the years. However, the thinly bedded sequence of sandstones and shales makes the reservoir characterization still a challenge. This study aims to clarify the sedimentological and petrophysical characteristics of the Early Cenomanian Bahariya Formation in Aghar-4 Oilfield Western Desert, Egypt. These characteristics will be used to overcome the petrophysical challenges in reservoir evaluation of the studied field. The used materials were Sedimentological logs and samples obtained from five cores of Aghar 4-1 well, in addition well log data of four wells penetrating Bahariya Formation in the studied oilfield. The petrographical analyses of the 38 selected samples from the various lithofacies at three reservoir levels of Bahariya Formation allowed their classification into 16 clastic rock types and 7 carbonate rock types. Based on the classification system of Dott (1964), the subfeldspathic wacke and glauconitic subfeldspathic arenites are the main recognized clastic rock types in the studied reservoir. The carbonate rock types were classified by Dunham (1962) into sandy wackstone rock types. The results of XRD analysis of the bulk samples indicated that quartz is the main mineral with subordinate amounts of plagioclase and K- feldspars. The clay fraction XRD analysis indicated that the recorded clay minerals are smectite, kaolinite, and illite. Smectite is the most abundant clay mineral with percentages reached up to 71 %. In addition, the petrographical analyses revealed that the studied sedimentary succession was affected by several diagenetic processes, which have influenced porosity and permeability and may have influenced the present day reservoir quality.