Integrated petrophysical and mineral composition of Miocene reservoirs (Kareem and Belayim Formations), Belayim onshore oil field, Gulf of Suez, Egypt: a case study

This study aims to shed light on the fundamentals of flow-through reservoir porous media, also the effect of mineral composition on reservoir properties that affect oil recovery, especially by water flooding process. Sandstone reservoirs were studied in terms of petrophysical and mineral composition of Miocene reservoirs in Belayim oil field, Gulf of Suez. X-ray diffraction (XRD) was utilized to scan eight representative samples, also fifteen representative samples were examined through their thin sections (TS), and similarly scanning electron microscope (SEM) was utilized to examine ten representative samples indicating that quartz, dolomite, and feldspars were found in variable amounts in both Belayim and Kareem Sandstone Formations. The clay minerals were mainly kaolinite, with trace amount of illite in Kareem Sandstone Formation, while considerable amounts of smectite, illite, and chlorite were found in Belayim Sandstone Formation. Porosity and permeability for the selected samples for relative permeability, capillary pressure, and wettability were measured for twenty-one representative samples from Kareem Formation (A1 Well) and fifteen representative samples from Belayim Formation (A2 Well). The pore throat size was not constant in Kareem Formation, while the majority of the samples had moderate to high permeability, maybe due to low amount of clay minerals. Belayim Sandstone samples also had variable pore throat sizes with low to moderate permeability, maybe due to high amount of clay minerals. Relative permeability curves of Kareem Formation showed that it is mainly water wet. While Amott wettability results indicated that Kareem Sandstone is neutral—water wet due to the presence of clay minerals (kaolinite with trace amount of illite). Relative permeability curves of Belayim Formation showed that it is moderately oil wet, while Amott wettability results indicated that Belayim Sandstone is mainly oil wet, possibly because of the abundance of dolomite and kaolinite with some illite, smectite, and chlorite in considerable amounts. The previous results showed that Kareem Sandstone is a good candidate for water flooding process, while Belayim Sandstone is not a good candidate because of the negative effects of the clay minerals. The study shows that clay minerals have major impact on wettability and water flood sweep efficiency and hence on the distribution of remaining oil saturation. A proper understanding of the distribution of clay minerals and remaining oil saturation may lead to effective reservoir management and improved oil recovery (IOR) and/or enhanced oil recovery (EOR) decisions.