Assessment of Hydrocarbon Saturation Distribution Using Resistivity Log Integration in the Gongola Basin, Adamawa State, North East Nigeria

The Gongola Basin in North East Nigeria encompasses several sedimentary sub-basins with demonstrated petroleum system elements, and understanding hydrocarbon saturation distribution through wireline log analysis is an important step in evaluating exploration and appraisal targets in this frontier area. This study assesses hydrocarbon saturation distribution in reservoir intervals encountered by boreholes in the Gongola Basin, Adamawa State, using resistivity log integration. Resistivity, gamma ray, density, and neutron porosity logs from three exploration wells were used to develop a petrophysical evaluation workflow. The Archie equation was applied for water saturation calculation in clean sand intervals, with appropriate values of cementation exponent (m) and saturation exponent (n) calibrated from core resistivity measurements. In shaly sands, the Waxman-Smits model was applied to account for the effect of clay-bound water on resistivity response. Net reservoir pay determination was made using porosity, water saturation, and volume of shale cutoffs derived from core-log correlation. Results indicate hydrocarbon saturations averaging 58 to 71 percent in identified pay sands across the three wells, with net pay ranging from 8 to 24 metres in the most prospective well. The study identifies two previously unappreciated reservoir intervals with low-resistivity pay characteristics attributable to conductive clay minerals and recommends resistivity anisotropy analysis as a follow-up study. Keywords: hydrocarbon saturation, resistivity log, Gongola Basin, Adamawa State, petrophysical evaluation.