SEDIMENTOLOGICAL AND BIOSTRATIGRAPHICAL STUDY

This study examines the sedimentological and biostratigraphical characteristics of Well X-1 in the Greater Ughelli Depobelt of the Niger Delta Basin, Southern Nigeria, in order to determine the age, depositional environment, and hydrocarbon potential of the penetrated strata. Seventy two ditch cutting samples collected between 4500 ft and 11460 ft were analyzed using reflected light microscopy to document lithology, grain size, sorting, and other sedimentological attributes. Four main lithofacies were identified. These are sandstone, shale, sandy shale, and shaly sand. Forty nine lithozones were delineated and used to interpret the vertical depositional succession. The sandstone and sandy shale units form a continuous reservoir interval between 5340 ft and 7260 ft, while the thick shale units below 7860 ft represent the probable source rock. A shale dominated interval above 4740 ft was interpreted as the seal or cap rock. Biostratigraphical interpretation using foraminiferal biofacies, F zone data, P zone data, and the Niger Delta chronostratigraphic chart revealed five maximum flooding surfaces at 6265 ft, 6688 ft, 7247 ft, 7771 ft, and 10280 ft, together with eight sequence boundaries occurring between 5899 ft and 10602 ft. These surfaces correspond to ages ranging from the Aquitanian to the Chattian. Foraminiferal abundance patterns show a dominance of calcareous benthonic species, which indicates deposition in a shelf environment. The alignment of the Bolivina 27 shale marker at 28.1 Ma with the basal shale supports its interpretation as the source rock interval. The combination of sedimentological and biostratigraphical evidence confirms the presence of the essential elements of a petroleum system, with favourable timing for hydrocarbon generation, migration, and entrapment