Reservoir Characterization of the Early Jurassic Butmah Formation Using Well Log Data in Selected Wells from Iraqi Kurdistan Region

The reservoir characterization of Butmah Formation (Early Jurassic) was studied in two wells: (AT-1) and (SH-1B) from Atrush and Shaikhan Oilfields respectively, in Iraqi Kurdistan Region. Well logs including; sonic, density, neutron, gamma ray, and resistivity, were employed to investigate the formation. The petrophysical properties, such as lithology, shale volume, porosity, water saturation, hydrocarbon saturation, and bulk water volume, were estimated using Interactive Petrophysics Software (IP). Water saturation, bulk volume of water, residual hydrocarbon, and movable hydrocarbon were plotted as Computer Processed Interpretation (CPI) for Butmah Formation in the studied wells. In order to check reliability of log data, lithology of the formation was detected using neutron-density cross plot and M-N cross plot. The results of log interpretation display that Butmah Formation is composed of dolomite, limestone with anhydrite and shale in the studied wells. The calculated shale volume shows low clay content. Therefore, Butmah Formation is considered as a clean formation in both wells. Porosity was estimated using porosity logs (sonic, density, and neutron) and had the average total porosity of (7% - 8%) in the two wells. Based on the determined petrophysical properties, particularly porosity and hydrocarbon saturation, it can be concluded that Butmah Formation seems potentially good in reserving oil.