Browsing by Author "Mahamed Hassen"

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    Provenance Controls on Porosity Evolution, Adigrat Sandstone, Ogaden Basin, South East Ethiopia
    (Addis Ababa University, 2023-06) Mahamed Hassen; Solomon Kassa (PhD)
    The Ogaden basin is the largest sedimentary basin in Ethiopia, with 350,000 km2 of areal coverage. Although it is the most studied region, so far 72 wells have been planned to be drilled in the area, i.e., the number of wells per area covered is 4861 km2. This thesis investigates provenance based on petrography, facies analysis of Adigrat Sandstone in Calub-wells and Hilala-wells in the Ogaden Basin, Ethiopia. A Detailed laboratory petrographic analysis was done on 25 sandstone samples (15 sample from the Calub field wells and 10 sample from the Hilala field wells). Changes in the mineral composition and lithofacies of these sediments over time relate to the tectonic development of the region. When the different grain mineralogies are associated with different source rock types, the signals of at least two distinct sediment source regions emerge. The relative amounts of sand-sized material from the study areas indicate a shift in provenance over time; with the advance of the Calub-wells, a mixed provenance of sedimentary and metamorphic source terrains gave way to a depositional record characterized by sedimentary source rocks. Petrographic and modal composition of the sandstone classification displayed mostly quartz arenite with few subarkosic and sublithic arenite. The modal composition of sandstone revealed that the provenances are craton interior, recycled orogeny, and continental block provenance. From the Qt-F-L tectonic setting plot, all samples fall outside of the tectonic setting field as a result of intense weathering. According to the analyzed data, the porosity of the Adigrat sandstone of the two gas fields is medium therefore the reservoir is good.