Integrated well log and sequence stratigraphic analysis for reservoir quality interpretation of the Raha Formation in the Ras Budran Field, Gulf of Suez Basin, Egypt

Abstract

Abstract The Raha Formation is a key reservoir rock in the Ras Budran Field (Gulf of Suez Basin, Egypt), but its lithofacies heterogeneity poses significant challenges for petroleum exploration and production. This study employs an integrated approach, synthesizing lithological, biostratigraphic, and petrophysical data from four key wells (RB-A2, RB-A7, RB-B2, RB-C4) within a sequence stratigraphic framework to deconvolve this heterogeneity and build predictive reservoir models. The formation is subdivided into a tripartite vertical succession: a lower sandstone, a middle limestone, and an upper sandstone unit. Pronounced thickness variations (from ~ 291 ft to ~ 475 ft) across the field are interpreted as a result of differential subsidence along fault blocks, which controlled spatial and temporal variations in accommodation. Sequence stratigraphic analysis defines a composite sequence comprising lowstand (LST), transgressive (TST), and highstand (HST) Systems Tracts. Petrophysical evaluation identifies the most promising reservoir zones within the coarse-grained LST and HST sandstones, characterized by high hydrocarbon saturation (0.50–0.85), effective porosity (0.12–0.21), and low shale volume (0.02–0.05). Crucially, this integrated model reveals that reservoir quality and distribution are systematically controlled by the sequence stratigraphic architecture. The thickest and highest-quality reservoirs are preferentially preserved in topographically confined depocenters, such as the southern graben (RB-C4 well), while the central structural highs (RB-B2 well) exhibit a different reservoir profile. This workflow demonstrates that reconciling sequence stratigraphy with petrophysical data provides a powerful predictive tool for characterizing reservoir heterogeneity, ultimately reducing exploration risk and optimizing development strategies in the Raha Formation and analogous rift basin reservoirs.