Petrology, lithofacies, and sedimentary environment of Upper Cretaceous Abu Roash 'G' in the AESW Block, Abu Gharadig Basin, Western Desert, Egypt

摘要

The Cretaceous clastic rocks are main targets for petroleum exploration and development in the Abu Gharadig Basin. In this paper, the petrology, lithofacies, and sedimentary environment are studied based on the core samples, thin sections (TS), and scanning electron microscopy (SEM) data of Upper Cretaceous Abu Roash "G" (AR "G") Member in the AESW Block, Abu Gharadig Basin, Western Desert, Egypt. Petrographic studies suggest that sandstones of the AR "G" are classified as sub-feldspathic arenites, quartz arenites, quartz wackes, and sub feldspathic wackes. Based on rock textures and fabrics, eight lithofacies are identified within sandstones as gravelly sandstone (Sg), massive sandstone (Sm), cross bedded sandstone (Scb), laminated sandstone (Sl), laminated silty sandstone (Slz), ripple laminated sandstone (Sri), deformed laminated sandstone (Sdl), and bio-turbated sandstone (Sb). Siltstone facies are classified as laminated siltstone (Zl), laminated sandy siltstone (Zls), laminated muddy siltstone (Zlm), lenticular siltstone (Zlt, and gravelly siltstone (Zg). Mudstone fades mainly consist of massive mudstone (Mm) and laminated mudstone (Ml). Petrographic study together with Lithofacies, typical sedimentary structures, palynomorphs, and biofacies suggest a tide-dominated coastal environment ranging from subtidal flat to intertidal flat in the study area. The tidal channels and tidal bars in the subtidal flat are the most favorable sedimentary microfacies for AR "G" sandstone reservoirs in the Abu Gharadig Basin, Western Desert, Egypt.