Integrated petrophysical evaluation of conventional and unconventional reservoirs: The Matulla sandstones and Thebes carbonates in the Geisum Field, Gulf of Suez, Egypt

This study provides an integrated petrophysical evaluation of conventional (Matulla sandstones) and unconventional (Thebes carbonates) reservoirs in the Geisum Field, Gulf of Suez, Egypt. Wireline log data from four wells (G-9, GA-5, GA-2, and GA-1), supported by seismic interpretation, were analyzed to determine shale volume, porosity, water and hydrocarbon saturation, and net-to-gross ratios. The Matulla Formation represents a thick, laterally continuous siliciclastic reservoir characterized by effective porosity of 0.20–0.26, hydrocarbon saturation exceeding 0.70, and net-to-gross ratios up to 0.59 (GA-5). Correlation among wells reveals lateral continuity of sand bodies but with fault-controlled thickness and depth variations, indicating strong structural influence on reservoir quality. In contrast, the Thebes Formation behaves as an unconventional carbonate reservoir with moderate effective porosity (0.14–0.19), heterogeneous pay zones (25–55 ft), and net-to-gross ratios of 0.23–0.49. Correlation between GA-2 and G-9 shows marked reservoir compartmentalization governed by fracture intensity and structural position rather than depositional facies. The comparison demonstrates that while the Matulla acts as a high-quality, laterally extensive conventional reservoir, the Thebes is a fracture-enhanced, compartmentalized unconventional play. Integrating petrophysical and structural analyses therefore provides a strong framework for optimizing hydrocarbon exploration and development in fault-controlled rift basins.