The effect of X‐ray micro computed tomography image resolution on flow properties of porous rocks

Summary The study of digital rock physics has seen significant advances due to the development of X‐ray micro computed tomography scanning devices. One of the advantages of using such a device is that the pore structure of rock can be mapped down to the micrometre level in three dimensions. However, in providing such high‐resolution images (low voxel size), the resulting file sizes are necessarily large (of the order of gigabytes). Lower image resolution (high voxel size) produces smaller file sizes (of the order of hundreds of megabytes), but risks losing significant details. This study describes the effect of the image resolution obtained by means of hardware‐based and software‐based approach. Four samples of porous rock were scanned using a SkyScan 1173 High Energy Micro‐CT. We found that acquisition using increased pixel binning of the camera (hardware‐based resizing) significantly affects the calculated physical properties of the samples. By contrast, voxel resizing by means of a software‐based approach during the reconstruction process yielded less effect on the porosity and specific surface area of the samples. However, the decreasing resolution of the image obtained by both the hardware‐based and the software‐based approaches affects the permeability significantly. We conclude that simulating fluid flow through the pore space using the Lattice Boltzmann method to calculate the permeability has a significant dependency on the image resolution. Lay Description Digital rock physics is a field of study that has made significant progress due to the development of digital image acquisition devices such as the X‐ray Micro Computed Tomography (Micro‐CT/μ‐CT) scanner. By using such devices, the microstructure of rock can be visualized and analyzed in three dimensions (3D). To produce a detailed 3D microstructure image of porous rock, high resolution (low pixel size) scanning is required. However, the resulting file sizes are necessarily large (of the order of Gigabytes), compared to lower image resolution (high pixel size) which produces smaller file sizes (of the order of hundreds of Megabytes). The use of lower image resolution has disadvantages such as the risk of losing significant details. This study describes the effect of the spatial image resolution on estimation of physical properties of porous rock. Four samples were scanned using a SkyScan 1173 High Energy Micro‐CT. The quality of the acquired images is significantly affected if the pixel size is