Investigation of the Carbonate Rock Permeability Based on X-Ray Tomography Images 3D Reconstruction and Homogenization of Composites

摘要

Digital rock physics (DRP) is a nondestructive method to study properties of rocks. Based on this approach, images of rocks are used for determining petrophysical properties such as porosity, permeability and thermal conductivity. In order to study permeability, the real rock microstructure is extracted from binarized rock images. The 3D imaging and segmentation software VCAT (released by V-CAD Program, RIKEN, Japan) has been used to transform medical computed tomography (CT) images to a meshed file that can be imported into commercial software ANSYS for simulating fluid flow and solving Navier-Stokes equations. The rock core samples contained of 10 carbonate pluges with the resolution of 187.5μm. The novelty of this work is to characterize fluid flow properties through rock samples by use of tomography technique and numerical simulations. The full-size plug samples in the medical X-ray CT can be used for imaging, and it is the main advantage of using this method in DRP. However, an important problem with the CT images is their resolution, which may fail to detect those pores which are smaller than the selected resolution. Although in this resolution some pores are not distinguishable, some responses of these pores are mapped on the images based on partial volume effect theory. Based on the descriptions mentioned above, the values of permeability gained from numerical simulations were compared with experimental results of plugs. The computed permeability values had good correlation with the experimental results.