Petrophysical Characterization of Indiana Limestone Using Medical Dual-Energy Computed Tomography Technique: Insights into Porosity, Bulk Density, and Effective Atomic Number

Abstract

Computed Tomography (CT) enables non-destructive 3D reconstruction of pore structures and rock properties mapping. Typically, such images are obtained from micro-CT (μm-scale) or synchrotron imaging (nm-scale). Despite their accuracy, these high-resolution imaging methods are expensive, time-consuming, and limited in sample size, affecting representative volume analysis. This work investigates an alternative approach using medical-CT (100 μm resolution) applying dual-energy CT technique (DECT) to characterize petrophysical properties (total porosity, bulk density, and effective atomic number) of six Indiana limestone samples (3.81 cm diameter, 4.88 cm length). Samples with porosities between 17.5% and 19.1% were scanned using paired high-energy (130 kV) and low-energy (80 kV) protocols, allowing DECT analysis to generate detailed 2D and 3D property maps. Additionally, the single-energy CT (SECT) technique, enhanced by subtracting images of the rock sample in saturated and dry conditions, improved the estimation of effective porosity. DECT and SECT results, processed with Python scripts and Avizo 3D, demonstrated average differences of 3.34% for bulk density, 5.30% for effective porosity, and 4.65% for effective atomic number compared to basic petrophysics measurements. Although artifacts from low-energy scans presented limitations, their impact can be reduced by optimizing acquisition parameters, improving the experimental setup, and applying reconstruction filtering techniques. Overall, this study highlights medical-CT as a fast, cost-effective method for analyzing larger samples, providing a practical alternative to traditional high-resolution imaging to estimate key petrophysical properties for the identification and visualization of heterogeneity on carbonates rocks.