Centers for Ethio Mines Development
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Browsing Centers for Ethio Mines Development by Subject "Adigrat sandstone"
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Item Identifying the Effects of Diagenesis on Reservoir Quality, Adigrat Sandstone, Ogaden Basin, South East Ethiopia(Addis Ababa University, 2023-06) Gemeda Ayansa; Solomon Kassa (PhD)The Ogaden basin is a vast sedimentary basin having 350,000 km2 areal coverage. Although it is the most studied region in Ethiopia, so far 72 wells have been drilled in the area, i.e. the number of wells per area coverage is 4861 km2. Due to large area coverage of Adigrat Sandstone reservoirs there, the Ogaden Basin in SE Ethiopia is of great importance for hydrocarbon exploration and development. However, diagenetic processes, which modify the rock's physical properties, affect its ability to store and flow hydrocarbons, and can have a significant impact on reservoir quality. Despite its significance as a reservoir, it is practically impossible to predict how diagenesis may affect the sandstones' reservoir quality. This study was conducted to find out the types of digenesis and its effect on the quality of Adigrat sandstone reservoir. To this end, 15 (fifteen) thin sections of Adigrat sandstones from YH-4 well were prepared and, ImageJ, JMicroVision, and petrographic analyses were employed to characterize the reservoir's diagenetic effect. The cementation of authigenic clay, silica, growth of authigenic glauconite, mineral dissolution, and load compaction are the key diagenetic processes that have impacted the reservoir quality of Adigrat sandstones. According to the framework grain-cement interactions, Clay cements, particularly illite, that partially line and fill pore spaces, developed alongside or after the early calcite cement's precipitation. Thus, it is inevitable that the reservoir rock’s porosity and permeability will decrease by this clay, which acts as a pore-choking cement.