Reservoir heterogeneity analysis and flow unit characteristics of the Upper Cretaceous Bahariya Formation in Salam Field, north Western Desert, Egypt

The Bahariya Formation (Upper Cretaceous) hosts the most prospective hydrocarbon reservoirs in the Western Desert, Egypt. The reservoir intervals consist mainly of fluvial and coastal marine sandstones, respectively, in the lower and upper Bahariya Formation. The definition of the best reservoir facies and the extent of reservoir heterogeneity are not very well constrained. This study presents a high-resolution definition for the reservoir facies distribution and heterogeneity in Salam Oil Field, north Western Desert. Seismic, well logs, and core analyses have been integrated in order to identify and categorize the different reservoir intervals. Detailed petrophysical well log and core studies have been utilized to further enhance our understanding of the magnitude of heterogeneity within the Bahariya sediments and therefore aid in constructing predictive models, which describe the fluid flow efficiency and reservoir performance. Four petrophysical rock types (PRT) have been identified; PRTI and PRT2 host the optimum reservoir properties and comprises the braided fluvial quartzose sandstones of the lower Bahariya (Av. phi = 20.74%, Av. KH = 367.53 mD, KV = 176.73 mD) with abundant megapores and isotropic, well-connected pore system. The upper Bahariya sediments only constitute the clay-and carbonate-rich PRT3 and PRT4 sediments that are dominated by micropores with predominant mesopores and a heterogeneous, poorly connected pore system. Upper Bahariya sediments have anisotropic pore-system (Av. permeability anisotropy > 3), reflecting the dominant anisotropic pore system. Eight hydraulic flow units (HFU) were identified; the reservoir efficiency decreases from HFU1 to HFU8. At megascale, the main flow conduits (speed zones) are predominantly composed of braided fluvial channel sandstones that mostly contain HFU1 and HFU2. The barrier zones are often associated with HFU7 and HFU8 and are commonly correlated with the lower Bahariya floodplain sediments and tidal flat, mixed tidal flat sediments of upper Bahariya. Notably, the greatest thickness of the upper Bahariya is classified as fluid flow baffles containing HFU5 and HFU6 with abundant micropores with good storage but low flow capacity.