Effect of CT image size and resolution on the accuracy of rock property estimates

Abstract

In order to study the effect of the micro‐CT scan resolution and size on the accuracy of upscaled digital rock property estimation of core samples Bentheimer sandstone images with the resolution varying from 0.9 μm to 24 μm are used. We statistically show that the correlation length of the pore‐to‐matrix distribution can be reliably determined for the images with the resolution finer than 9 voxels per correlation length and the representative volume for this property is about 153 correlation length. Similar resolution values for the statistically representative volume are also valid for the estimation of the total porosity, specific surface area, mean curvature, and topology of the pore space. Only the total porosity and the number of isolated pores are stably recovered, whereas geometry and the topological measures of the pore space are strongly affected by the resolution change. We also simulate fluid flow in the pore space and estimate permeability and tortuosity of the sample. The results demonstrate that the representative volume for the transport property calculation should be greater than 50 correlation lengths of pore‐to‐matrix distribution. On the other hand, permeability estimation based on the statistical analysis of equivalent realizations shows some weak influence of the resolution on the transport properties. The reason for this might be that the characteristic scale of the particular physical processes may affect the result stronger than the model (image) scale.

Quantitative Analysis of Pore Space Structure in Dry and Wet Soil by Integral Geometry Methods

“…where Betti numbers can be interpreted in the context of soil pore space in the following way [31,41]: b 0 is the number of connected components (individual pores), b 1 is the number of "tunnels" (or redundant connections, loops, torus-all types of pores that cannot be compacted into a dot), and b 2 is the number of solid clusters that are completely surrounded by pores (supposed to be equivalent to 1). Only two phases (pores and solid skeleton) are rationalized in the investigated sample, so, according to [42,43], Minkowski functionals and Betti numbers were calculated for the pore space.…”

Numerical Simulation of the Reactive Transport at the Pore Scale

“…Note, that the interface defined as a constant level of function is approximated by a piecewise linear line. Note also that the model is a micro-CT scan of the real rock sample [ 2 – 4 ]; thus, it is extremely detailed for either description of the pore space structure or the physical processes. As a result the low-order finite difference schemes can be used in application to pore scale simulation.…”

Impact of mesh quality on the numerical estimation of saturated water conductivity of pore media

“…A similar study, based on different modelling approaches, was presented by Shah et al (2016) for sandstone permeability estimations; it used pore network modelling and the LBM. Variations in permeability have been demonstrated for four sandstone images of different sizes and resolutions (Bazaikin et al, 2017;Borujeni et al, 2013;Guan et al, 2019;Shah et al, 2016). Guan et al (2019) investigated the impact of a decrease in image resolution (simulated by pixel binning) on estimates of permeability.…”