著者

藤井 孝志 菅井 裕一 佐々木 久郎 橋田 俊之 當舎 利行 中尾 信典

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.129, no.12, pp.701-706, 2013-12-01 (Released:2014-12-01)

参考文献数

17

被引用文献数

1 1

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Understanding of interfacial interactions among supercritical CO2 (scCO2), water, and mineral phase is necessary for a precisely prediction of CO2 migration into aquifers. The purpose of this study is to assess the impact of scCO2 on flow property of Kimachi sandstone and Iidate granite in a CO2 rich dense phase i.e., the condition of which scCO2 is expected to displace formation water in the course of CO2 injection. In this experiment, the permeability test for CO2 gas was conducted before and after a CO2 saturation procedure that is filled with scCO2 in pores of rocks. To investigate a mechanical property of rock specimen in the presence of scCO2, the axial strain was also measured using a laser displacement sensor during scCO2 saturation processes. Our results showed that both Kimachi sandstone and Iidate granite samples tested have a more or less decreasing trend of gas permeability with increasing exposure time to scCO2. It was further shown that the axial strain of Kimachi sandstone and Iidate granite increased as scCO2-exposure time increased. Additionally, increases in masses and dimensions of test samples before and after scCO2 saturation processes were clearly observed under atmospheric pressure conditions. It can, therefore be said that Kimachi sandstone and Iidate granite could be capable of swelling and permeability change accompanied by CO2 sorption into their internal structures in the presence of scCO2. Furthermore, the observed significant reduction in permeability cannot fully be explained by two model predictions based on Kozeney-Carman equation and Hagen-Poiseuille law, considering CO2 sorption onto mineral phases. The present results pointed out that CO2 sorption on rocks under geological CO2 storage conditions could have a significantly impact on flow property of rocks during CO2 injection and storage processes.

著者

竹原 孝 及川 寧己 藤井 孝志 宮崎 晋行

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.136, no.11, pp.134-139, 2020-11-30 (Released:2020-11-28)

参考文献数

28

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A project of CO2 injection in the Ishikari coal basin (Yubari-shi, Hokkaido, Japan) since 2002 has shown that injection of CO2 into coal seams affected their permeability. Adsorption of CO2 caused swelling of the coal matrix and lowered the permeability of coal seams, probably because of closure of cleats and pores in the coal seams. However, a temporary recovery of permeability was observed after subsequent injection of N2, suggesting that some amount of adsorbed CO2 was replaced by N2 and the closure of cleats and pores were mitigated. However, the changes of mechanical properties of coal in the process are not yet fully understood. In this study, we injected CO2 and N2 into coal specimens recovered from the Ishikari coal basin and observed the changes of coal strength under hydrostatic pressure and temperatures typical of a coal basin. We conducted triaxial compressive strength tests on the coal specimens to clarify the effects of CO2 and N2 on the mechanical properties. Our results are summarized below.1) We verified that swelling and shrinkage of the coal were associated with adsorption and desorption, respectively, of CO2.2) The triaxial compressive strength tests showed that injection of CO2 caused decreases of peak strength and Young's modulus.3) Both coal strength and Young's modulus recovered when previously injected CO2 was replaced by N2.