Reservoir quality and rock type zonation for the Sidri and Feiran members of the Belayim Formation, in Belayim Land Oil Field, Gulf of Suez, Egypt

This paper aims to evaluate the reservoir quality and determine the rock type zonation in the subsurface Sidri and Feiran members of the Belayim Formation, in Belayim Land Oil Field (well 112-136), Gulf of Suez, Egypt. To achieve this aim, an integrated petrographical analysis (thin sections, scanning electron microscope SEM and X-ray diffraction XRD) and petrophysical estimation have been carried out on units of the Sidri and Feiran members using core samples and well logs data. Reservoir evaluation of the studied members revealed an occurrence of four reservoir rock types (RRT1, RRT2, RRT3, and RRT4) and four hydraulic flow units (HFU1, HFU2, HFU3, and HFU4). Diagenetic processes are summarised into two groups depending on their effect on the reservoir potentiality. They show dissolution processes as a porosity improvement factor and porosity diminishing aspects including compaction, mechanical infiltration, authigenic mineral, and cementation. The RRT1 rock samples are quartz arenite quartz, whereas the RRT2, RRT3, and RRT4 are dolomitic quartz arenite, dolomitic quartz wacke, and argillaceous sandy dolostone, respectively. The final findings showed that RRT1 and RRT2 provided the best reservoir zones in both Sidri and Feiran members, whereas RRT3 and RRT4 which predominate in HFU4 had the lowest potential zones of reservoir. The capillary pressure by using mercury injection test (MICP) shows that, samples of RRT1 are predominantly macro-pore sizes with some occurrences of meso- and micro-pore spaces, whereas RRT2 are dominated by meso-pores throat radius with some samples characterised by both macro and micro-pore spaces. The RRT3 reservoir rock samples are characterised by micro-pore throat radius with few meso-pore samples, whereas RRT4 samples are mainly characterised by micro-pore throat radius. Therefore, there is a similarity between the zonation obtained from the MICP method, statistical differentiation of the hydraulic flow unit, and other zonation methods in terms of: porosity-permeability and reservoir quality index (RQI) - normalised porosity index (NPI) relationships.

Automated summary

This study evaluates the reservoir quality and rock type zonation in the Belayim Land Oil Field, Gulf of Suez, Egypt, using integrated petrographical analysis and petrophysical estimation. Four reservoir rock types and hydraulic flow units were identified, with RRT1 and RRT2 showing the best reservoir zones. Capillary pressure tests confirmed the pore structure characteristics of different reservoir rock types. The study's findings aligned with other zonation methods in terms of porosity-permeability relationships and reservoir quality index.