Petrophysical Evaluation of Hydrocarbon Reservoirs Using Wireline Log Data in the Southern Anambra Basin, Ebonyi Flank

The southern Anambra Basin along the Ebonyi State flank contains sedimentary sequences with documented hydrocarbon shows, yet quantitative petrophysical characterization of reservoir intervals in this sector is sparse. This study conducts a petrophysical evaluation of hydrocarbon reservoirs using wireline log data from two wells penetrating Cretaceous sandstone sequences on the Ebonyi flank of the Anambra Basin. Gamma-ray, resistivity, density, neutron porosity, and sonic logs were loaded and evaluated in Schlumberger Techlog software. Lithofacies interpretation from gamma-ray logs identified five discrete sandstone units bounded by shale intervals within the Nkporo and Mamu Formations. Shale volume was estimated using the linear gamma-ray index method, and effective porosity was computed from the density-neutron crossplot approach. Water saturation was calculated using the Archie equation and modified Simandoux model for shaly sand intervals. Porosity values in the primary reservoir sandstones range from 16 to 28 percent, while water saturation values between 30 and 60 percent indicate residual and moveable hydrocarbon columns in two reservoir units. Net pay thickness reaches 18 m in the most prolific interval identified in Well-2. Permeability transforms derived from the Timur equation suggest moderate reservoir deliverability (30 to 190 millidarcies). These results define two prospective reservoir intervals suitable for further testing. The study provides a quantitative petrophysical database for the Ebonyi flank of the Anambra Basin and contributes to the assessment of hydrocarbon potential in this underexplored basin sector.

Keywords: wireline logs, petrophysical evaluation, Anambra Basin, hydrocarbon reservoir, Nkporo Formation