High-Resolution X-Ray Computed Tomography of Liquid CO<SUB>2</SUB> Permeation in Water-Saturated Sandstone

Abstract

Geological sequestration of carbon dioxide (CO 2 ) is an effective method to achieve a substantial reduction in CO 2 emissions to the atmosphere at a relatively low cost; however, the migration process of CO 2 in deep saline aquifers has not been clarified. In order to evaluate the storage site and assess the CO 2 leakage risks and storage costs, fundamental visualization and study of immiscible two-phase flow in sandstone are required. This study observed the behavior of liquid CO 2 injected into water-saturated Berea sandstone by using microfocus X-ray computed tomography with high spatial resolution. The three-dimensional CO 2 distribution in the sample was clearly reconstructed. The bedding structure of the rock strongly determined the CO 2 permeation process, and a strong correlation was seen between the local porosity of the sample and the CO 2 saturation. The real time CO 2 permeation process was also observed in the transparent images that showed the CO 2 gradually permeating the rock in the axial direction with increased saturation in the higher porosity beddings. The effects of the sandstone micro-heterogeneity on the behavior of the injected liquid CO 2 are discussed.

Pore‐scale investigation of effects of heterogeneity on CO2 geological storage using stratified sand packs

“…The variations are mainly due to the effects of the capillary, with CO 2 tending to occupy the high-porosity areas and hardly entering the low-porosity areas. According to previous studies, there is an approximately linear correlation between CO 2 volume and slice-averaged porosity in homogeneous core samples; 45,46 however, the stratified structure weakened this linear correlation, which was therefore not observed in the BZ06+BZ02 pack. Therefore, the heterogeneity in pore size impacted the specific CO 2 distribution and a deviation from the linear correlation between the CO 2 volume and the slice-averaged porosity can potentially be used in assessing the heterogeneity of cores.…”

Experimental determination of wettability and heterogeneity effect on CO2 distribution in porous media

“…Six images were needed to obtain the porosity and CO 2 saturation profiles, which included brine and air, brine and CO 2 saturated porous media, dry sample, and experimental images. The distributions of the slice‐averaged porosity and the CO 2 saturation along the core were calculated by using the following equations, where CT is the brightness value of the CT image. The calculation errors may come from the fluctuation of the experiment condition, the unstable imaging process, and the incorrect image cropping.…”