Reservoir Characteristics of Bajawan and Baba Formations in Selected wells of Bai Hassan Oil Field, North Iraq

Abstract

The study aims to analyze the petrophysical properties of the Bajawan and Baba formations in wells BH-80, BH-193, and BH-194 in the Bai Hassan field (Oligocene, northwest Kirkuk) using available well logs. The results indicate that BH-193 has the lowest shale content, suggesting a cleaner depositional environment, whereas BH-194 has the highest shale content, potentially impacting reservoir quality in the Bajawan Formation. The transitional (Bajawan/Baba) formation appears relatively balanced, while the Baba Formation is more argillaceous, particularly in BH-193 and BH-194. Neutron, density, and sonic logs indicate that the Baba Formation exhibits the highest total porosity compared to Bajawan and the transitional formation, reflecting better storage capacity, with BH-194 recording the highest values and BH-193 the lowest, indicating weaker reservoir quality. Secondary porosity (SPI) is generally low, suggesting limited influence from dissolution or fracturing, except in the Baba Formation of BH-194, where higher values indicate greater secondary porosity development. Effective porosity (PHIE) is lower in the Bajawan Formation (%0.02 - %0.08) compared to the Baba Formation (%0.10 - %0.16), indicating better reservoir quality in the latter. Water saturation analysis from LLD, ILD, and MSFL resistivity logs shows that the Baba Formation has low water saturation (0.048-0.94), enhancing its hydrocarbon retention, whereas the Bajawan Formation has higher water saturation (0.155-0.804), which may reduce production efficiency