Sensitivity analysis of segmentation techniques and voxel resolution on rock physical properties by X-ray imaging

Pore and grain phases separation significantly affect the rock physical properties extracted by digital rock measurement techniques (DRMTs). Previous studies mainly focus on approaches to predict the physical properties of rocks, and less attention is paid on the effects of segmentation techniques and voxel resolution on rock physical properties. Physical properties of rocks are not still well understood using DRMTs with less experiment effort. In this work, 6 segmentation algorithms and 4 voxel resolutions combined with X-ray CT imaging are applied to the Stainton and Clashach sandstone, Indiana limestone and Estaillades carbonate samples to understand their effects on rock physical properties. Moreover, threshold-porosity relations are proposed to accurately segment the pores and grains in rocks. Results show that voxel resolution has little to no impact on the rock physical properties. However, the segmentation algorithms significantly affect these properties, in which the Ostu's method, Iterative self-organizing data (IsoData) method and Fuzzy c-mean clustering (FMC) method should be alternative methods to separate the pore and grain phases in sandstones. For carbonates, under-segmentation is still inevitable with these techniques. Rock physical properties calculated by the proposed threshold-porosity relations are closer to the experiment results than those calculated by the classical segmentation methods.