Evaluation of Black Shale Sediments in Upper Cretaceous Dakhla Formation at the Kharga Depression, Western Desert, Egypt

Abstract

<title>Abstract</title> <bold>Background</bold> Black shales are globally recognized for their dual role as both conventional hydrocarbon source rocks and unconventional resources as oil-shale and shale-gas reservoir. <bold>Objectives</bold> This study evaluates the hydrocarbon potential of Upper Cretaceous black shale deposits of the Dakhla Formation in the Kharga Depression, Western Desert, Egypt. <bold>Methods</bold> Representative shale samples were collected from the Um Ghaneima outcrop section and from core samples at the Abu Tartur Mine and were analyzed using an integrated mineralogical and geochemical approach, including X-ray fluorescence (XRF), X-ray diffraction (XRD), total organic carbon (TOC), total sulfur (TS), and Rock-Eval pyrolysis. <bold>Results</bold> XRD data indicate that shales of the Dakhla Formation are dominated by clay minerals, particularly smectite and kaolinite, reflecting a dominantly detrital origin and deposition in a shallow-marine setting. TOC values show significant spatial variability, ranging from low concentrations in Um Ghaneima (maximum 0.27 wt.% TOC; up to 1.91 wt.% TS) to elevated levels in the Abu Tartur core (maximum 2.82 wt.% TOC), indicating pronounced heterogeneity in hydrocarbon potential. Rock-Eval pyrolysis results suggest deposition under suboxic to anoxic conditions with Type II and Type II/III kerogen. The organic matter is currently in an immature to early oil generation stage, with limited indigenous hydrocarbons preserved. <bold>Conclusion</bold> Collectively, the findings highlight the Dakhla Formation black shales in the Kharga Depression as an underexplored alternative resource with generally poor to fair, but locally enhanced, hydrocarbon potential. Their combined mineralogical composition and organic richness support consideration as a supplementary oil-shale and gas-shale resource, particularly where TOC and HI are highest in the Abu Tartur subsurface interval.