Diagenetic evolution and reservoir potential of the Barremian–Cenomanian Debre Libanose Sandstone, Blue Nile (Abay) Basin, Ethiopia

The Blue Nile Basin is located in the Central Plateau of Ethiopia. The basin consists of Precambrian basement, Palaeozoic and Mesozoic sedimentary rocks and Tertiary volcanic rocks. The sedimentary successions and Debre Libanose Sandstone reach a maximum thickness of 3000 and 310 m, respectively. The Debre Libanose Sandstone is composed of mudstone, finely laminated siltstone, fine-to medium-grained sandstone, massive to crudely cross-bedded gravely sandstone and massive to crudely bedded conglomerate. In the Blue Nile Basin it was deposited in a fluviatile environment, predominantly in braided and meandering rivers. The sandstone has a complex diagenetic history and is cemented by silica, calcite, kaolinite, hematite with minor amounts of illite and chlorite. Depositional environment, burial and thermal history, pore water composition and circulation, and diagenetic processes are the major factors that control the porosity and permeability of the sandstone. Minor amounts of primary porosity are preserved owing to framework grain stability. Dissolution of feldspar grains and calcite cement created a certain amount of secondary porosity in the sandstones. The fine-to medium-grained sandstones are porous and have good reservoir potential.