It is challenging to identify appropriate large-scale CCS sites in Japan because of its geology and because it is an Island. Despite these challenges, there are a few areas along the coast of Japan that have porous rock formations such as sandstone that are potentially suitable for CCS on a small scale. However, they are not continuous and exist as distinct pockets near the coast of Japan. The aim of this study was to analyze the storage and migration characteristic of CO2 in Ainoura sandstone, a sandstone with relatively high porosity and low permeability. CO2 migration tests were conducted by injecting it into rock samples saturated with potassium iodide solution. The flow process and storage states were analyzed using a μ-focus X-ray CT scanner. In this study, we used an image subtraction method to evaluate the replacement ratio of potassium iodide solution by CO2 following injection. The results showed that the amount of CO2 that could be potentially stored was dependent on the proximity of the pores to the injection surface, and that the flow of CO2 was not uniform. The mean replacement ratio was approximately 20% of the pore volume and was comparable to results from previous studies using different rocks.

1. Introduction

Carbon dioxide capture and storage (CCS) is one of the promising methods which can be used to capture and reduce the amount of CO2 in the atmosphere. CCS entails the capturing of CO2 emitted and its storage deep underground, and currently some large scale CCS sites are operational in some European countries (Chardwick et al., 2009; Ghanderi et al., 2009) and Canada (Rinding, 2009). In order for large scale CCS to be realized large uniform rock formations must be identified. In Japan, a large scale CCS project was started in 2016, and approximately one hundred thousand tons of CO2 have been stored in the geological reservoir. However, the amount of CO2 stored in this project is less that than the cases of Europian countries and Canada. This is because of the complex geology of Japan. Moreover, it is difficult to find appropriate large scale aquifers near Japanese islands. In his study, it is aimed at the establishment of small scale and regional CCS which is located near an industrial site.

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