ARC Journal of Radiology and Medical Imaging Volume 3, Issue 2, 2018, PP 14-18 www.arcjournals.org ARC Journal of Radiology and Medical Imaging Page | 14 X-Ray Micro-Computed Tomography Observations of Local Particle Displacements in Porous Media Jafar Qajar 1* , Christoph H. Arns 2 1 Digital Rock Physics Research Group, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran 2 School of Petroleum Engineering, The University of New South Wales, Sydney, NSW 2052, Australia 1. INTRODUCTION Recent progress in the development of X-ray micro-computed tomography (μ-CT) makes it possible to directly visualize and quantify various features of the microstructure of complex porous media including sedimentary rocks, in particular [1-5]. In various porous media processes such as chemical dissolution and mechanical compaction, the conditions may be appropriate to allow local particle detachment and displacement within the porous medium. It is noted that for flow-through- porous-media experiments, a lack of observation of fines production does not preclude considerable local mobilization of particles within the porous medium at the pore-scale. Particle mobilization may be triggered by inertial forces of flow itself or releasing by chemical reactions or other forces and then displacing by flow. The local mobilization of fines is a largely unexplored phenomenon at the pore scale due to difficulty in direct access to local particle displacement. Only a few studies have addresses the issue of particle displacement and deposition in microtomographic images. Lebedeva, et al. [6] studied the low salinity brine flooding of sandstone and observed the local detachment of dolomite and anhydrite from μ-CT images at a voxel size of 2.4 μm. They only observed local particle displacement and no further quantitative analysis was presented. In the realm of chemical dissolution, Kumar, et al. [7] reported slices from two registered tomograms of an oolitic carbonate core exposed to carbonic acid for 96 hours at CO 2 partial pressure of 10 atm. They identified regions of particle displacement and reprecipitation in their images. In these studies, no quantitative calculations related to particle displacement were performed on the images. Noiriel, et al. [8] and Bernard, et al. [2] indicated particle mobilization in their images and proposed a method to quantify evolutions of image voxels including evolution scenario related to particle displacement. Their results are limited to small-size image data and based on single-threshold segmentation of the images which may accompany a large uncertainty especially for complex sedimentary rocks. The changes in pore structure of a special natural sediment subject to a simulated caustic tank leach ate was studied byCai, et al. [9]. They quantified the microstructure changes due to dissolution and secondary precipitation based on pore/throat analysis derived from microtomographic images. It should be noted that heir results are limited to a small sub- volume which the REV requirements to represents the reactive flow effects remain questionable. Among various methods, imaging techniques have been widely used to directly visualize and Abstract: The application of X-ray micro-computed tomography (μ-CT) for qualitatively visualizing dissolution-induced local particle detachment, displacement and deposition in carbonate rocks is investigated. In this work, the experiments have involved alternating steps of imaging and ex-situ core sample dissolution. Reactive flow experiments through two carbonate core samples with different rock types were considered. For the first rock, we found a quasi-uniform dissolution regime whereas a wormhole-like dissolution pattern was observed in the second sample. For both samples, we observed regions within the samples where they were initially in the pore space, but finally were occupied by solid particles. Keywords: Micro-CT imaging; Dissolution; Particle displacement *Corresponding Author: Jafar Qajar, Digital Rock Physics Research Group, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran, Email: jqajar@shirazu.ac.ir