Source rock potential, palynofacies depositional environment synthesis and structural traps of the Enugu Formation Southeastern Region, Nigeria

The incessant natural gas flare and oil seepages triggered the source rock potential palynofacies exposé, depositional environment and lateral facies changes as well as sedimentary structures trapping synthesis of the Enugu Formation to unravel the structural trap style, hydrocarbon production potential and pathway for reserves of the formation for hydrocarbon generation. Opaque particles, yellow and dark-brown amorphous organic matter, marine taxa with few dark-brown structured phytoclasts and terrestrial microflora denote the visual palynofacies attributes of the study. Kerogen essential shows thermally mature type II–III kerogen indicative of oil- and gas-prone materials. The natural gas flare are products of kerogen type III (gas prone) palynofacies elements while the pronounced oil seepages are the productive result of kerogen type II (oil prone) palynofacies groups. These palynofacies features are deposited in transitional marine settings in the inner neritic zone with outer neritic influences consistent with estuarine, nearshore and fresh water environment based on the normal diverse quality and quantity of palynofacies components and abundance of land-derived microflora over marine dinocysts. Structural hydrocarbon entrapment mechanisms of the Enugu Formation outcrop key structural traps consists of hanging wall closures, footwall closures and half graben along with infilled and open-joint structures within faulted and unfaulted sandstone lenses. Primary and secondary migration petroleum pathway in sandstones pores and fractures are the major principal means in the creation of petroleum accumulations of the formation. The natural gas flare and oil seepages denote these structural style elements as unequivocal petroleum systems architecture for hydrocarbons trap within the Anambra Basin. The highlighted structural complexity, lateral facies changes, alleviates the gas flare prognosis and subsequent oil drilling pathway as well as exploration campaign in the Formation.