Reservoir heterogeneity and quality of wajh formation: Outcrop analog study, Red Sea region, Saudi Arabia

The early Miocene Wajh Formation represents an early rifting event alluvial fan deposits that triggered by early rifting phase in Midyan area, Red Sea region. Stratigraphically equivalent formations occur throughout the Red Sea region and the Wajh Formation represents important reservoir target in the Midyan Region, NW part of Saudi Arabia. The work is based on outcrop analog study aimed to characterize facies and depositional environment and to establish a facies depositional model. The facies are dominated by sandstones and conglomerates while the mudstones and shale represents minor percentages. On outcrop the Wajh Formation shows an overall stacked progradational succession that controlled by tectonics and sediment supply. The stratigraphic architecture and heterogeneity is influenced by shale and mudstone depositional barriers that affected sandstone vertical continuity and connectivity. However, laterally, the sandstone bodies showed good connectivity which interrupted locally by vertical faulting and fracturing at outcrop scale. At meso-scale and micro-scales reservoir heterogeneity and characteristics are affected by both depositional texture, composition and post depositional diagenetic changes. The outcrop analog study of Wajh Formation might provide guides to understand and predict controls and reservoir properties of equivalent lithofacies in the subsurface.