Well Log Analysis and Reservoir Characterization in a Shallow Hydrocarbon Field Within the Anambra Basin, Enugu State

The Anambra Basin in southeastern Nigeria hosts a series of shallow hydrocarbon accumulations that remain insufficiently characterized due to limited application of quantitative petrophysical analysis. This study performs a comprehensive well log analysis and reservoir characterization in a shallow hydrocarbon field within the Anambra Basin, focusing on the interval within Enugu State. Gamma-ray, resistivity, neutron porosity, and density logs from three wells were processed and interpreted using Interactive Petrophysics software. Lithological units were identified from gamma-ray and caliper logs, revealing interbedded sandstone and shale sequences with three distinct reservoir intervals. Shale volume, effective porosity, water saturation, and permeability were estimated using industry-standard equations. Effective porosity values in the reservoir sandstones range from 18 to 32 percent, while water saturation values between 25 and 55 percent indicate commercially viable hydrocarbon pay zones in two of the three reservoir units. Net-to-gross ratios exceeding 0.60 in the primary reservoir interval suggest favorable reservoir quality. Petrophysical crossplots, including neutron-density and M-N plots, confirm the dominance of quartz-rich sandstone with minimal clay contamination in the pay sections. Estimated permeability values derived from porosity-permeability transforms range from 45 to 280 millidarcies, suggesting moderate to good reservoir deliverability. These results provide a quantitative petrophysical framework for the field and represent a significant contribution to understanding hydrocarbon systems within the Anambra Basin.

Keywords: well log analysis, reservoir characterization, Anambra Basin, petrophysics, water saturation