Geophysical Constraints on Petroleum Prospectivity in the Anambra Basin

This study examines the geophysical constraints on petroleum prospectivity in the Anambra Basin, South East Nigeria, using available potential field and seismic data to evaluate the basin's remaining hydrocarbon potential. The Anambra Basin contains Campanian to Eocene sedimentary sequences hosting coal, bitumen, and reported hydrocarbon shows, but its petroleum potential has been incompletely assessed relative to the prolific Niger Delta. This study reprocesses and reinterprets public-domain gravity and aeromagnetic data for the basin using modern potential field enhancement techniques, and reviews available 2D seismic data from NIPEX for basin architecture assessment. Bouguer gravity modelling defines basin geometry and estimates sediment thickness across the basin. Aeromagnetic depth estimates using Euler deconvolution and spectral analysis delineate basement relief. Seismic interpretation identifies key reservoir and seal units and structural closure types. Petroleum system elements including kitchen areas, migration pathways, trap types, and seal adequacy are assessed from the integrated geophysical interpretation. Findings reveal a depocentre with estimated sediment thickness of 4.5 to 5.5 kilometres in the southern Anambra Basin, providing sufficient burial for hydrocarbon generation from Campanian coals and carbonaceous shales. Gravity modelling identifies two sub-basins separated by a basement high that may compartmentalise separate petroleum systems. Seismic interpretation shows that most closures are fault-controlled structural traps of limited size, with two seismic amplitude anomalies that may represent stratigraphic traps. The study concludes that the Anambra Basin has meaningful petroleum prospectivity warranting renewed exploration investment.

Keywords: petroleum prospectivity, Anambra Basin, potential field, seismic interpretation, hydrocarbon system.