Introducing an Innovative Method for Assessing Reservoir Heterogeneity Using Zenga Index in the Permian Basin of the Central Persian Gulf

Summary A quantitative analysis of heterogeneity is crucial for assessing and comparing the factors that influence carbonate formations. In reservoir studies, heterogeneity is defined as the variation in one or a combination of properties within a spatial distribution and at a specific scale. In this study, reservoir heterogeneity was evaluated for the first time using a semi-quantitative approach based on the Zenga index. The method was applied to wireline log data from the Late Permian Dalan Formation in the central Persian Gulf. Heterogeneity logs were calculated and compared with geological and petrophysical characteristics. Normalization using statistical techniques was applied to minimize instrument-induced noise and facilitate a more accurate identification of the true formation heterogeneity. Gamma ray (SGR), bulk density (RHOB), neutron porosity (NPHI), and acoustic (DT) data were analyzed, with NPHI showing the highest heterogeneity. Results demonstrate that the Zenga index is more sensitive to small data variations compared with the Lorenz coefficient. High heterogeneity values were observed at the boundaries of reservoir units, reflecting significant changes in lithology, pore types, porosity, and permeability. In contrast, SGR heterogeneity logs exhibited inconsistencies, primarily due to the influence of shale on carbonate heterogeneity. The results demonstrated that the Zenga method allows for a numerical comparison across different reservoir sections, providing a semi-quantitative assessment of heterogeneity. This approach enhances geological analysis and aids in effective reservoir characterization.