<b>Contrast in clay mineralogy and their effect on reservoir properties in sandstone formations</b>

• Main Author: Wolela Ahmed
• Format: Article
• Language: English
• Published: Chemical Society of Ethiopia 2008-04-01
• Series: Bulletin of the Chemical Society of Ethiopia
• Subjects: Adigrat sandstone; Authigenic mineralization; Clay minerals; Diagenesis; Permo-Triassic
• Online Access: http://www.ajol.info/index.php/bcse/article/view/61333

Adigrat sandstone formation in the Blue Nile Basin is dominated by quartz arenite and subarkosicarenite, and cemented by carbonate, clay minerals and quartz overgrowths. Clay minerals in the Adigratsandstone formation are dominated by kaolinite, illite and chlorite. Illite is the common grain-coating claymineral. The common pore-filling minerals are kaolinite, illite and chlorite. The formation reaches a depth of 3km, which facilitated the change of kaolinite to illite. Clay minerals are the major reducer of porosity andpermeability in the Adigrat sandstone formation.The Permo-Triassic sandstones in the Ulster Basin were deposited in NE-SW trending fault-boundedasymmetrical graben. The Permo-Triassic sandstones reaches a burial depth of 1/2 km in the marginal areas and4.5 km in the basin center. The basin underwent multiple episodes of uplift and erosion in the Upper Jurassic, andMid-Cretaceous, and uplift and inversion in the Upper Tertiary. The difference of the clay mineralogy in thePermo-Triassic in the Ulster Basin depends upon the depositional environments, source area geology and burialhistory of the basin. Illite-smectite is grain coating, whereas smectite, illite-smectite, smectite-chlorite, chlorite,illite and kaolinite are the common pore-filling clay minerals in the Permo-Triassic sandstones in the Ulster Basin.Clay minerals reduced the porosity and permeability of the Permo-Triassic sandstones.