Palaeoenvironmental and hydrocarbon exploration assessment of DAJ field sediment in Niger Delta basin, Nigeria

Abstract

The Niger Delta Basin ranks among the most prolific hydrocarbon provinces in the world, and its complex sedimentary architecture, shaped by fluvio deltaic and shallow marine processes, continues to reward integrated subsurface study. Accurate palaeoenvironmental reconstruction remains central to understanding hydrocarbon generation, migration, and accumulation, particularly in data limited settings where conventional cores are unavailable. This study investigated the palaeoenvironment and hydrocarbon prospectivity of sediments from the DAJ Field through integrated lithologic, lithofacies, palynofacies, and palynostratigraphic analyses. Sixty six ditch cuttings samples recovered from ER-51 Well between 2360 and 4340 feet were composited into thirty three representative samples for detailed laboratory investigation. Lithologic and lithofacies analyses revealed a predominance of fine grained sedimentary units, with two lithofacies, namely shale and argillaceous shale, indicating deposition within a low energy setting favourable for the preservation of organic matter. Palynofacies analysis identified four palynomaceral groups, PM-1, PM-2, PM-3, and PM-4, together with structureless organic matter, and the assemblage was dominated by PM-1 and PM-2 with moderate PM-4 and minor PM-3. The consistently high abundance of phytoclasts indicates a strong terrestrial organic matter input and a proximal depositional position, and the sediments are interpreted to record a terrestrial rainforest to brackish water swamp palaeoenvironment reflecting alternating continental and marginal marine influence. Biostratigraphic evaluation, based on diagnostic palynomorph events, assigns the studied interval a Middle to Late Miocene age spanning the Langhian to the Tortonian. The integrated dataset provides useful insight into the depositional history, stratigraphic framework, and hydrocarbon significance of the DAJ Field, and the abundance of terrestrially derived organic matter, together with favourable preservation conditions, points to appreciable potential of the succession for hydrocarbon generation and accumulation.