Implication of the Heterogeneous Reservoir Rock Types on the Reservoir Quality of the Nullipore Reefal limestones of the Middle Miocene Belayim Formation in Al-Hamd Field, Gulf of Suez, Egypt

This study focuses on the important Nullipore reefal limestone of the Belayim Formation, which holds hydrocarbons, by identifying its main types of reservoir rocks and how their differences affect the quality of the reservoir in the Al-Hamd Field in the Gulf of Suez (GOS). The Dykstra-Parsons technique was applied to assess the degree of heterogeneity, indicating that the heterogeneity coefficient (V = 0.95, i.e., extremely heterogeneous reservoir). The range of permeability anisotropy (λk) is between 0.71 and 5.0 (slightly to highly secondary and primarily anisotropic). Vertically, the stratigraphic modified Lorenz plot (SML) was applied to categorize the reservoir sequence into some hydraulic flow units (HFUs). The reservoir sequence was divided into three RRTs/HFUs using the X-Y plots of the reservoir parameters, such as the porosity-permeability plot along with the discrete rock typing values (DRT), the RQINPI (reservoir quality index-normalized porosity index) plot, and the RQI-FZI (reservoir quality index-flow zone indicator) plot. The best reservoir properties are assigned to the RRT2 (av. ∅He = 28.2%, av. kH = 176.4 mD, and av. kV = 69.9 mD) with moderate permeability anisotropic reservoirs (λk = 1.82). Also, the av. RQI value of the RRT2 = 0.58 mm; referring to a fair reservoir quality, while the av. FZI = 1.33 mm referring to poor reservoir quality, where (1.0 < FZIpoor ≤ 2.5 mm), reflecting a somewhat promising poor to fair reservoir quality. In contrast, the RRT1 and RRT3 samples are classified as compacted reservoirs, which have the least ability to store and flow fluids in the nullipore sequence. Moreover, the average R35, as one of the reservoir quality indicators, of the RRT2 samples refers to mesopore sizes (1-10 mm), while for the other two types it refers to micropore sizes (0.1-1.0 mm). Therefore, this study presents a comprehensive petrophysical analysis using core data on the reefal limestone, which has not been previously studied in the Gulf of Suez. The proposed workflow can be applied to other analogues in the Gulf of Suez and beyond, particularly to similar types of coralline reefal reservoirs.