High-Resolution X-Ray Computed Tomography of Liquid CO2 Permeation in Water-Saturated Sandstone

概要

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Geological sequestration of carbon dioxide (CO2) is an effective method to achieve a substantial reduction in CO2 emissions to the atmosphere at a relatively low cost; however, the migration process of CO2 in deep saline aquifers has not been clarified. In order to evaluate the storage site and assess the CO2 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 CO2 injected into water-saturated Berea sandstone by using microfocus X-ray computed tomography with high spatial resolution. The three-dimensional CO2 distribution in the sample was clearly reconstructed. The bedding structure of the rock strongly determined the CO2 permeation process, and a strong correlation was seen between the local porosity of the sample and the CO2 saturation. The real time CO2 permeation process was also observed in the transparent images that showed the CO2 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 CO2 are discussed.