Quantitative reservoir characterization and exploration significance of the lower Miocene Asl Sandstone, north-central Gulf of Suez, Egypt

The Lower Miocene Asl Sandstone of the Upper Rudeis Formation is evaluated in four wells (ET-A3, ET-A4, NO159-6ST1, and GS160-5A) in the north-central Gulf of Suez using integrated wireline-log analysis, petrographic observations from ET-A3, and structural and depositional interpretation. The study addresses the poorly constrained distinction between reservoir-quality rock and effective hydrocarbon pay within this heterogeneous syn-rift sandstone succession. Thin sections show quartz-rich sandstone with lithic fragments, variable grain size and sorting, compactional grain contacts, silica overgrowths, preserved intergranular pores, and local microfractures. These characteristics support deposition across proximal, middle, and distal parts of a submarine-fan system, followed by heterogeneous diagenetic modification. Petrophysical evaluation indicates average effective porosity of 0.125–0.157 v/v and water saturation of 0.107–0.597 v/v within net-reservoir intervals. NO159-6ST1 contains the most favorable interval, with 61 ft of net reservoir, 60 ft of net pay, a pay-to-gross ratio of 0.817, effective porosity of 0.158 v/v, and water saturation of 0.101 v/v within pay. Conversely, ET-A4 contains 34 ft of net reservoir but only 3 ft of interpreted net pay because of substantially higher water saturation. Thus, fluid saturation, rather than porosity alone, primarily controls effective-pay development. The sandstone occurs within NW–SE-trending fault blocks and locally grades laterally into finer-grained deposits, creating combined structural and stratigraphic trapping potential. By explicitly separating net reservoir from net pay, this study provides an integrated petrographic–petrophysical framework for evaluating the Asl Sandstone. The results highlight thick, relatively clean sandstone intervals with preserved pore space and favorable saturation as priority exploration targets and offer transferable screening criteria for comparable Miocene syn-rift plays.