The impact of carbonate texture on the quantification of total porosity by image analysis

A comparison between image analysis, He-porosimetry and MICP total porosity indicates that the image analysis workflow used in this study can accurately quantify or underestimate total porosity depending on the lithofacies textures and pore systems. The porosity of wackestone lithofacies tends to be significantly underestimated (i.e. greater than 10%) by image analysis, whereas packstone, grainstone, rudstone and floatstone lithofacies tend to be accurately estimated or slightly underestimated (i.e. 5% or less) by image analysis. The underestimation of image analysis porosity in the wackestone lithofacies is correlated to the quantity of matrix pore types and is thought to be caused by incomplete imaging of microporosity and by unrepresentative fields of view. Image analysis porosity, which is calculated from 2D areas, is comparable with 3D porosity volumes in lithofacies that lack or are weakly microporous; in such lithofacies, image analysis is assumed to be accurately measuring other 2D parameters, including pore sizes and shapes.