Pore Scale Analysis of Diffusion Phenomena in Rocks by Means of μ-Focus X-Ray CT

In this study mu -focus X-ray CT was applied to analyze a material flow due to diffusion in porous rocks. Here, one-dimensional diffusion tests were performed using solution of potassium iodate (KI) as a tracer. As representatives of porous rocks, Berea sandstone and Kimachi sandstone were applied, and the diffusion phenomena including pore structures in the pore scale were visualized. In order to extract the density information due to the diffusion, image subtraction method was applied to the CT images. By applying the method, the density increment due to the diffusion and its location was easily extracted. It was found that the KI solute mainly diffuses in the pore networks in the case of Berea sandstone. On the other hand, it was found that the KI migrates not only through pores but also micro pores/fractures in grains in the case of Kimachi sandstone. The difference of diffusion velocity in both samples was also discussed.