Resolution and Limitations of X-Ray Micro-CT with Applications to Sandstones and Limestones

X-ray microtomography (μCT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \hbox {CT}$$\end{document}) scanning provides high-resolution images in applications ranging from medical to material sciences and failure analysis. In general, CT scanning relies on X-ray absorption to produce a 3D computed image of the material. In Earth Sciences, μCT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \hbox {CT}$$\end{document} scans are used to characterize porosity and pore size, shape and topology of rock samples. For sufficiently large pore systems, the resulting segmented images may be used for quantitative transport calculations. In this note, we infer the limitations of μCT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \hbox {CT}$$\end{document} images of rock samples, caused by attainable resolution for a representative sample size. To this end, (1) we perform a systematic analysis with the aid of a resolution chart, (2) we present example scans of an Indiana limestone and a Berea sandstone mini-cores, and (3) we process and analyze the images to extract pore structures using different segmentation algorithms. Porosity estimates inferred from μCT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \hbox {CT}$$\end{document} images tend to be lower than bulk measurements.