Lithofacies, stratigraphy, and provenance study of upper sandstone, Blue Nile (Abay) Basin, Ethiopia: insight to the distribution of reservoir facies

The Blue Nile Basin is one of the frontier basins in Ethiopia, where there is very limited sub-surface data to understand the petroleum system of the basin. In frontier basins, only comparative analogs can be used for reservoir studies. The main purpose of the study is to elucidate the importance of facies, stratigraphic, and provenance study to comprehend the nature of the reservoir rock in the Blue Nile Basin. The study reveals the presence of eight lithofacies in the study area. The textural, structural, and compositional data and the general fining-upward sequence of the upper sandstone attest fluvial deposition by braided river system. The presence of the dominant medium-grained quartz arenite with moderate cementation (diagenesis) effect in the upper sandstone is an indication for the existence of good reservoir rock in the basin. The upper sandstone is relatively thinner in the study area, average 75 m, compared to the central part of the basin, average 220 m, and this depicts the geometry of the upper sandstone which pinches out to the north of the basin. Comparison of provenance and cement types of the upper sandstone in the study area and central part of the basin revealed the existence of similar nature of reservoir rock in the basin.