The implication of sedimentary facies, petrography, and palynofacies of shales and carbonates of the Oti-Pendjari and Kwahu-Bombouaka Groups on the hydrocarbon potential of the Voltaian Basin of Ghana

With the exhaustion of the “easy to find” hydrocarbons, the search for hydrocarbons in Precambrian sedimentary basins has increased over the years. The Voltaian Basin of Ghana is part of the Neoproterozoic sedimentary basins of the West African Craton (WAC). Unlike the Voltaian Basin, other Neoproterozoic basins of the WAC are relatively explored. The study seeks to explore the hydrocarbon prospects of the Voltaian Basin using facies analysis, petrographic studies, and palynofacies. Shales and carbonate samples from the Oti-Pendjari and Kwahu-Bombouaka Group of the basin were sampled for studies. On the basis of sedimentary structures, the color of the shales and field associations were used in the facies classification. Ten facies were grouped, 1, 4, and 5 facies for the Kwahu-Bombouaka Group, the Kodjari Formation, and Pendjari Formation of the Oti-Pendjari Group, respectively. The sediments were deposited rapidly from sediment-laden currents into shallow marine and fluvial environments for the shales of the Pendjari Formation and Kwahu-Bombouaka Group. The sediments of the Kodjari Formation are of marine to deep marine settings. The petrographic compositions of the shales suggest euxinic conditions evolved into oxic conditions and the paleoenvironmental conditions were suitable for primary organic matter (OM) productivity. Pyrite framboid presence supports unaltered OM within the shales. The shales and carbonates contain phytoclasts and palynomorphs with no observable amorphous organic matter (AOM). Although generally in small quantity, the palynomorph content is relatively more than the phytoclast content. Although depositional conditions are dominantly shallow marine–marine, OM preservation was favored in the basin.