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Geochemical Modeling on Water–caprock–gas Interactions within a CO2 Injected in the Yeongil Group, Pohang Basin, Korea
포항분지 영일층군 내 이산화탄소 주입에 의한 물-덮개암-가스 반응에 대한 지화학적 모델링
Econ. Environ. Geol. 2021 Feb;54(1):69-76
Published online February 28, 2021;  https://doi.org/10.9719/EEG.2021.54.1.69
Copyright © 2021 the Korean society of economic and environmental gelology.

Seon-ok Kim1, Sookyun Wang1, Minhee Lee2,*
김선옥1 · 왕수균1 · 이민희2,*

1Department of Energy Resources Engineering, Pukyong National University
2Department of Earth & Environmental Sciences, Pukyong National University
1부경대학교 에너지자원공학과 2부경대학교 지구환경과학과
Received January 9, 2021; Accepted January 12, 2021.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
This study is to identify the mineralogical properties of caprock samples from drilling cores of the Pohang basin, which is the research area for the demonstration-scale CO2 storage project in Korea. The interaction of water-rock-gas that can occur due to CO2 injection was identified using geochemical modeling. Results of mineralogical studies, together with petrographic data of caprock and data on the physicochemical parameters of pore water were used for geochemical modeling. Modelling was carried out using the The Geochemist’s Workbench 14.0.1 geochemical simulator. Two steps of modeling enabled prediction of immediate changes in the caprocks impacted by the first stage of CO2 injection and the assessment of long-term effects of sequestration. Results of minerlaogical analysis showed that the caprock samples are mainly composed of quartz, K-feldspar, plagioclase and a small amount of pyrite, calcite, kaolinite and montmollonite. After the injection of carbon dioxide, the porosity of the caprock increased due to the dissolution of calcite, and dawsonite and chalcedony were precipitated as a result of the dissolution of albite and k-feldspar. In the second step after the injection was completed, the precipitation of dawsonite and chalcedony occurred as a result of dissolution of calcite and albite, and the pH was increased due to this reaction. Results of these studies are expected to be used as data to quantitatively evaluate the efficiency of mineral trapping capture in long-term storage of carbon dioxide.
Keywords : geological CO2 storage, Pohang basin, caprock, water–rock–gas interactions, geochemical modeling

 

February 2021, 54 (1)