Reservoir characterization of the Oligocene units and Jeribe formation in Khabaz oilfield

The study investigates the petrophysical properties and reservoir characteristics of the Oligocene units and Jeribe formation of the Khabaz Oilfield, northern Iraq, focusing on well A1, for the depths between 2234.97 and 2460 meters. The Jeribe formation is of Early Miocene, has been identified as a significant hydrocarbon reservoir. The interplay between dolomite and limestone influence permeability and porosity. Unlike limestone reservoirs, whose relationships are linear, dolomite reservoirs exhibit complex relationships between porosity and permeability due to the change of rock volume and porosity shape. The study employs gamma-ray, neutron, density, sonic, and resistivity logs, along with other well log data from A1 and A2 wells, for analyzing shale volume, porosity, and fluid saturation. The findings divide the Jeribe formation and Oligocene formation into subzones (A, B, BE, E Units) based on calculated porosity. That indicates the reservoir quality ranges from fair to very good, with effective porosity being an important factor affecting permeability. Neutron-density and M-N cross plots are utilized to delineate various lithological features, supporting the idea that limestone and dolomite are the main components of the reservoir. The results reveal that the dolomitic composition of the Jeribe formation has moderate permeability, while micro-fractures in Unit B enhance permeability significantly. The study highlights the critical role of effective porosity in enhancing fluid flow potential. This will provide valuable insights for planning hydrocarbon development and investment strategies of Khabaz Oilfield. Overall, this research emphasizes the importance of the comprehensive petrophysical analysis in understanding reservoir static and dynamic properties supporting and optimizing resource management. Keywords: petrophysical properties; reservoir characterization; Oligocene units and Jeribe formation.