Petrophysical Assessment of the Reservoir Intervals Within the Gombe and Gongila Formations, KY Field Chad Basin, Northeastern Nigeria

Abstract

This study presents a comprehensive petrophysical evaluation of reservoir pay zones within the Gombe and Gongila formations across three wells in the Chad Basin, focusing on key reservoir parameters, including porosity, permeability, water saturation, and lithology (volume of shale), to assess reservoir quality and hydrocarbon potential. The analysis used triple-combo well logs (gamma-ray, neutron, density, and resistivity) from three wells: XY-1, XY-2, and XY-3. Petrophysical evaluation was conducted using Schlumberger Techlog software to define zones, establish correlations, and assess reservoir properties. The results show distinct variations in reservoir properties across both formations, with water saturation in the Gombe and Gongila formations averaging 0.34 m³/m³ and 0.25 m³/m³ (XY-1), 0.30 m³/m³ and 0.32 m³/m³ (XY-2), and 0.51 m³/m³ and 0.31 m³/m³ (XY-3), respectively. Average porosity values were 0.30 m³/m³ and 0.23 m³/m³ (XY-1), 0.29 m³/m³ and 0.26 m³/m³ (XY-2), and 0.31 m³/m³ and 0.10 m³/m³ (XY-3), while shale-volume measurements averaged 0.21 and 0.25 (XY-1), 0.23 and 0.23 (XY-2), and 0.22 and 0.25 (XY-3). Pay-zone thickness varied substantially, measuring 117.3 m and 20.4 m (XY-1), 42.3 m and 22 m (XY-2), and 337 m and 129.4 m (XY-3) for the Gombe and Gongila formations, respectively. Overall, the Gombe Formation demonstrated superior reservoir properties and greater pay-zone thickness, with thickness generally increasing towards well XY-3. These findings provide insight into the reservoir potential of both formations within the Chad Basin and support ongoing exploration in this underexplored frontier basin.