FORAMINIFERA AND PALEOENVIRONMENTAL RECONSTRUCTION OF WELL ‘OM’ IN THE NIGER DELTA, SOUTHERN NIGERIA

This study focuses on the biostratigraphic and paleoenvironmental reconstruction of Well 'OM', a key exploratory well located in the prolific onshore Western Niger Delta Basin, Southern Nigeria. The aim of carrying out this research is to use forams to reconstruct the paleoenvironment of well OM. Analysis was performed on a suite of ditch-cutting samples recovered from the well, which were processed and examined to identify, count, and document both planktonic and benthic foraminiferal species. The Planktonic-to-Benthic (P/B) ratio was calculated for key intervals to quantitatively determine the paleo-water depth. In order to achieve this, the results from the analysis using paleoenvironmental investigation shows that the penetrated sediment range in age from the Middle to Late Miocene. This age was confirmed by correlating the First Downhole Occurrences (FDOs) of characteristic planktonic species with the established global and local biozonation schemes. The lithologic column is characterized by alternating sandstones and shales, consistent with the paralic sequence of the Agbada Formation. The P/B ratio values, in conjunction with the identified benthic foraminiferal assemblages (e.g., Spiroplectammina, Ammonia), indicate a significant environmental shift. The environment of deposition is interpreted as a progradational sequence, transitioning from a deeper outer neritic (deep shelf) setting at the base of the studied interval to shallower inner neritic to coastal swamp conditions towards the top. The established biostratigraphic framework and paleoenvironmental model provide a precise chronology for the well and confirm the presence of high-quality reservoir sands interbedded with effective marine shale seals and source rocks. These findings reinforce the significant hydrocarbon potential of the 'OM' field and its immediate surroundings within the Niger Delta's Coastal Depobelt.