Facies analysis-constrained geophysical 3D-static reservoir modeling of Cenomanian units in the Aghar Oilfield (Western Desert, Egypt): Insights into paleoenvironment and petroleum geology of fluviomarine systems

Abstract

The Cenomanian fluvio-estuarine Bahariya Formation was investigated as an example for estuarine complexes at Aghar oilfield. A facies-constrained 3D-static reservoir geocellular modeling and 1D basin modeling were performed in this study for the purpose of adequately identifying the architectural elements, and charge timing, of such an important reservoir. We utilized a range of datasets, from basin to microscopic scales, such as seismic lines, well log data, conventional and special core data, thin sections and SEM images. The results show that Bahariya Formation is stratigraphically subdivided into a lowstand systems tract (LST) represented by the Lower Bahariya fluvial system and a transgressive one which is represented by the Upper Bahariya estuarine system. Five sedimentary facies assemblages were assigned for Bahariya Formation. Based on the petrographical description, SEM and XRD data, the studied samples are summed up into four microfacies associations. The available core data includes bulk density, helium porosity, vertical and horizontal permeability, and capillary pressure data. Applying the porosity-permeability plot, Dykstra-Parsons, discrete rock type, the reservoir quality index (RQI)-flow zone indicator (FZI) plot, effective pore radius of Winland (R35), and the stratigraphic modified Lorenz technique, it is indicated that the studied Bahariya samples can be grouped into eight reservoir rock types (RRTs). Among them, four RRTs are considered prospective, whereas the others are non-prospective. Besides, the Bahariya Formation is subdivided into two compartments with very high heterogeneity, due to the alternation between conductive and non-conductive hydraulic flow units (HFUs), which is attributed to the differential impact of the digenetic features including cementation, compaction and presence of authigenic minerals. The present tidal sandstone inlets case study deserves a special concern, for running the future oilfield development plans, and consideration in similar geologic settings.