Empirical correlation for porosity deduction from X-ray computed tomography (CT)

For obtaining reservoir petrophysical properties, for example porosity, non-destructive methods such as X-ray computed tomography, CT, seems to be precise and accurate. Porosity is deducted from the CT image with a single scan via different techniques, such as pore space detection by image segmentation techniques then correlation with porosity. More than one hundred samples with carbonate lithology have been scanned and analyzed in this study which leads to empirical correlation used for porosity calculation from CT data. The samples mainly grouped as dolostone, limestone and carbonate with respect to their mineral contents, having porosity ranges between 4.56 to 30.5 % and permeability from 0.25 to 3350.8 md. The results showed that the effect of atomic number is higher than the density on CT image. It is because density and atomic number in carbonate mineral (calcite and dolomite) show diverse relations. Thus, the assumption of known lithology would be a large source of error. A good linear relationship exists between the porosity and CT no. according to the developed correlations.