The influence of spatial resolution and noise on fracture network properties calculated from X-ray microtomography data

Abstract

Rock deformation experiments performed at X-ray synchrotrons provide unique insights into the nature of fracture network development. However, these insights depend on the limitations of the X-ray tomography data. Here, we examine how spatial resolution and noise influence the calculated fracture network properties. To assess the influence of spatial resolution, we acquire two overlapping X-ray tomograms with spatial resolution that differ by an order of magnitude. To assess the influence of noise, we produce sets of synthetic tomograms with varying degrees of noise, including point-source noise and blurring noise. In the absence of noise, the differing spatial resolutions produce calculated porosities that differ by 0.05%, or 30% of the porosity measured in the high-resolution data. The fracture property that changes the most in the datasets of varying resolution is the fracture surface area, rather than the volume, length, or aperture. The two types of noise influence the porosity and fracture characteristics in opposite ways. In the synthetic tomograms in which higher values indicate fractures, added point noise increases the porosity while blurring noise decreases the porosity. In volumes with a mapping of gray values in which fractures have lower values, this trend would be reversed. This study is the first to quantify differences in fracture network properties extracted from X-ray tomograms due to spatial resolution and noise.