HYDROCARBON CHARACTERIZATION OF ANUWA FIELD, OFFSHORE DEPOBELT, NIGER DELTA BASIN

Abstract

The study titled “Characterization of Reservoirs of the Anuwa Field in the Offshore Depobelt of the Niger Delta Basin” focuses on the evaluation and characterization of hydrocarbon-bearing formations using geophysical well logs. Data from gamma ray were analyzed alongside those from spontaneous potential, density, caliper, resistivity as well as neutron logs to determine the lithology, petrophysical parameters, and overall quality of the reservoirs. Six distinct reservoirs D5000, D5200, D7000, D8000, D2000, and C3000 were identified and evaluated based on their log responses. In Well 35, reservoirs D5200, D7000, and D8000 were encountered at depths between 7193.43 to 7607.44 ft, while Well 36 penetrated C1500, D5200, D7000, and D8000, between 5805.61 to 7634.36 ft. The computed petrophysical parameters showed gross thicknesses of 82.48–137.84 ft, net and thicknesses of 24.5–65.25 ft, net-to-gross ratios of 0.249–0.789, and shale volumes between 0.258–0.394. Porosity values ranged from 24–27%, water saturation from 22–34%, hydrocarbon saturation from 66–78%, and permeability from 95–151.5 millidarcies (md). These results indicate that the Anuwa Field reservoirs are composed mainly of good-quality, hydrocarbon-saturated sandstones with favorable storage and flow characteristics. The study emphasizes the critical role of geophysical well logging in subsurface formation evaluation. Unlike drill cuttings or core samples, which provide limited or discontinuous data. Well logs offer continuous, in-situ measurements that enable accurate delineation of lithologies and estimation of formation fluids. Advances in computer-based logging and interpretation have significantly enhanced hydrocarbon exploration and reservoir assessment. Overall, the findings demonstrate that Anuwa Field possesses economically viable reservoirs with promising production potential. The integration of modern well-logging techniques has proven essential in determining accurately the key petrophysical properties, most importantly porosity, permeability, saturation, and capillarity, which collectively define reservoir quality and productivity within the Niger Delta Basin (NDB).