Research on the complex wettability characteristics and precise saturation evaluation method for the P formation reservoir in the Bongor Basin, Chad

The Bongor Basin in Chad is located in the western extension zone of the Central African Rift System. Its Cretaceous P reservoir, as the main production layer, has complex lithology and significant heterogeneity, and the oil reservoir resistivity values vary greatly, making saturation evaluation difficult. Based on data from lithology, physical properties, rock electrical experiments, and nuclear magnetic experiments, this study focuses on the Baobab and Daniela blocks in the Bongor Basin of Chad. The study analyzes the complex wettability characteristics of the P reservoir in the Bongor Basin and proposes a saturation calculation model that combines rock wettability with electrical resistivity. Research has shown that the P group sand bodies can be divided into four sets from top to bottom. The first set is composed of thin sandstone layers containing mud, witharesistivity of less than 20 Ω·m, using a mud sandstone saturation model; The second set is partially thick sandstone with a resistivity of less than 100 Ω·m, suitable for hydrophilic models; The third set has an abnormally high resistivity reservoir with a resistivity of 300~1000 Ω·m, which is explained by an oil affinity model; The resistivity of the second set of partial sand bodies and the fourth set of sand bodies is between 100 and 300 Ω·m, suitable for the mixed wetting model. This method achieves accurate calculation of saturation of complex wettability reservoirs in the Bongor Basin of Chad, providing key technical support for efficient exploration and development in the basin in the future.