Visualization and Analysis of CO2 Permeation Process in a Porous Media by Microfocus X-Ray Computed Tomography

Abstract

Carbon capture and sequestration (CCS) is part of the global challenge of mitigating global warming and climate change. Geological sequestration of carbon dioxide (CO 2 ) is an immediately available and technologically feasible method for achieving a substantial reduction in carbon dioxide emissions into the atmosphere. Because the density of CO 2 is lower than that of water, injected CO 2 migrates upward in an aquifer owing to the buoyancy force. Therefore, a highly impermeable layer is generally employed to prevent CO 2 leakage from the storage reservoirs. For these reasons, assessment of the storage site, leakage risks, and storage costs are one of the main issues in CO 2 geological sequestration. The intent of the present study was to clarify the fundamental mechanism of CO 2 migration in a reservoir.The behaviour of liquid CO 2 in water-saturated silica packed bed was observed using high spatial resolution X-ray computed tomography. As the result, CO 2 behavior in the water saturated porous structure was visualized with 20 μm resolution, and it was found that the permeation and distribution of liquid CO 2 were strongly dominated by the local pore size and its structure.

Power generation characteristics of a SOFC with a Ni/YSZ anode incorporating a SrZr_0.95Y_0.05O_3-α proton conductor

“…1(d) and (e), the porosity of both anodes was obtained. The pore size distribution was obtained by an approximation that circles are inscribed to pores in the binarized images (Uemura et al, 2012), which is shown as Fig. 1(f).…”

Optimizing contrast agents with respect to reducing beam hardening in nonmedical X-ray computed tomography experiments

“…Iodine, with its large atomic number (Z), is one of the most commonly used contrast agents in nonmedical science and engineering. For example, it is used in laboratory experiments by means of medical and microfocus X-ray computed tomography (CT) systems to help visualize the flow or diffusion of fluids in complex, porous geological media [2][3][4][5]. Humans and animals have a low density (≈1-2 g/cm 3 ); however, porous geological media generally have a much higher density (≈2-4 g/cm 3 ), which means that a pore fluid with an iodine concentration much larger than that needed for the CT measurements of humans and animals must be used (e.g., a KI solution of 0.6 mol/L [2]).…”

“…In most cases, however, the artifact is undesirable because the spatial distribution of the voxel values in a homogeneous sample is distorted to be heterogeneous. Example includes CT image-based calculations of the relative permeability curve and residual oil saturation [12] by means of the partial-volume effect [13][14][15] in two-phase Darcy flow experiments [3,4,15].…”

“…To examine the feasibility of this method, we performed a series of CT simulations. The simulations mimic the cupping artifact which often occurs in the CT images of homogeneous porous geological samples saturated with heavy element-bearing fluids [4,27]. Assuming the use of a polychromatic medical CT scanner, synthetic CT images were reconstructed for porous sand-pack samples saturated with aqueous suspensions of various concentrations of different heavy elements.…”

The use of sodium polytungstate as an X-ray contrast agent to reduce the beam hardening artifact in hydrological laboratory experiments

“…However, undesirable beam hardening artifacts (e.g., Ketcham and Carlson, 2001) occur in the obtained CT images when iodine is used with a medical or micro-focus CT scanner having a polychromatic X-ray source. The beam hardening reduces the accuracy of any post-CT outcomes such as image-based porosity calculations (e.g., Uemura et al, 2012). Thus, a better contrast agent is needed.…”