Corresponding Author

Hussein S. Hussein

Document Type

Original Article


The distribution of petrophysical parameters is governed by lithology, hence understanding the spatial variation in lithology is essential for reservoir characterisation. This study points out the use of well logs to estimate the lithology of carbonate rocks (limestone, marly limestone, dolomite, and dolomitic limestone) found in Upper Cretaceous to Miocene formations at the Khabbaz Oil Field in Northern Iraq. Applying the multivariate regression technique to neutron, and density data enabled accurate lithology prediction. By using independent values (well log data) to predict a dependent value (lithology), this technique is a progression of regression analysis. The formations under study comprised a large amount of marly limestone, dolomite, and dolomitic limestone, according to the well log data results. It is possible to calculate the shale content using gamma-ray logs. R2 = 0.72 showed a statistically significant association between the described and anticipated lithologies. For subsequent prediction for other formations in the same well, the model with a higher coefficient of determination (0.72) might be evaluated. In the absence of cores, this work is helpful for lithological and petrophysical characterization of carbonate reservoirs and facies analysis.


Multivariate regression, Carbonate lithology, Gamma-ray log, Density log, Neutron log