Partial dissolution of carbonate rock grains during reactive CO2-saturated brine injection under reservoir conditions

Kamaljit Singh , Benaiah U. Anabaraonye , Martin J. Blunt , John Crawshaw - Qatar Carbonates and Carbon Storage Research Centre, Department of Earth Science and Engineering, Imperial College London, U.K.

Our novel procedure of injecting oil after reactive transport has revealed previously unidentified (ghost) regions of partially-dissolved grains of carbonate rock. X-ray micro-tomography and FIB-SEM techniques were used to identify and resolve these ghost regions in three-dimensions at the nm- to µm-scale. Considering the solid part of the ghost regions as macro (bulk) pore space can result in the overestimation of porosity and permeability predicted from segmented X-ray tomographic images.

How Amira-Avizo Software is used

The tomograms were reconstructed using proprietary software provided by Zeiss and processed using Avizo 9 software unless otherwise specified. The tomograms were pre-processed to remove distorted outer regions. The stitched image (5 µm voxel size) of the dry rock sample was filtered using a non-local means edge preserving filter. This was then segmented into two phases (solid and pore space) using a seeded watershed algorithm based on the gray-scale gradient and gray-scale intensity of each voxel.