• Journal of Soil and Groundwater Environment
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• v.22 no.3
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• pp.42-49
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• 2017

TOUGH2 was used to simulate the migration of $CO_2$ injected into a sandy aquifer. A series of numerical simulations was performed to investigate the effects of a low-permeability layer (LPL) embedded in the aquifer on the injection rate and the pressure distribution of $CO_2$. The results show that the size and location of the LPL greatly affected the spread of $CO_2$. The pressure difference between two points in the aquifer, one each below and above the LPL, increased as the size of the LPL increased, showing a critical value at 200 m, above which the size effect was diminished. The location of the LPL with respect to the injection well also affected the migration of $CO_2$. When the injection well was at the center of the LPL, the injection rate of $CO_2$ decreased by 5.0% compared to the case with no LPL. However, when the injection well was at the edge of the LPL, the injection rate was decreased by only 1.6%. The vertical distance between the injection point and the LPL also affected the injection rate. The closer the LPL was to the injection point, the lower the injection rate was, by up to 8.3%. Conclusively, in planning geologic storage of $CO_2$, the optimal location of the injection well should be determined considering the distribution of the LPL in the aquifer.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.547-557
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• 2013

The mode II fracture toughness and strength due to shear stress are important parameters in the stability of caprock and injection zone with application to geological sequestration of carbon dioxide. In this research, a short beam compression test has been used to determine the shear strength and the mode II fracture toughness for Coconino sandstone. The average value of the shear strength and mode II fracture toughness are estimated to be 23.53 MPa and 1.58 MPa${\surd}$m respectively. The stress intensity factor is suggested by finite element analysis using the displacement extrapolation method. The effect of biaxial stress and water saturation on the fracture toughness has also been investigated. The fracture toughness increases with confining stresses, but decreases by 11.4% in fully saturated condition.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.291-294
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• 2010

$CO_2$ is known as the major source of the green house effect and the volume produced from electricity generation and transportation sector in Korea constitutes the large portion. In order to reduce the green house effect, several treatment methods can be the major research topics such as the scheme to fundamentally restrict the production of $CO_2$ creation, to perfectly sequestrate the produced $CO_2$, to reuse the separated $CO_2$, or to permanently dispose $CO_2$ in an appropriate storage site. Among of them, R&D strategy and geotechnical research issues are explored in this paper in an effort to realize geological storage for the sequestrated $CO_2$ in local storage sites. $CO_2$ is known as the major source of the green house effect and the volume produced from electricity generation and transportation sector in Korea constitutes the large portion. In order to reduce the green house effect, several treatment methods can be the major research topics such as the scheme to fundamentally restrict the production of $CO_2$ creation, to perfectly sequestrate the produced $CO_2$, to reuse the separated $CO_2$, or to permanently dispose $CO_2$ in an appropriate storage site. Among of them, R&D strategy and geotechnical research issues are explored in this paper in an effort to realize geological storage for the sequestrated $CO_2$ in local storage sites.

• Journal of Soil and Groundwater Environment
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• v.20 no.1
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• pp.19-27
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• 2015

If $CO_2$ stored for geological sequestration escapes from deep formations and is introduced to shallow aquifers, it dissolves into groundwater, creates acidic environments, and enhance mineral dissolution from rocks and soils. Among these minerals, dissolution and spread of hazardous trace metals can cause environmental problems with detrimental impacts on groundwater quality. This study aims to investigate geochemical effects of $CO_2$ in groundwater on dissolution of galena, the main mineral controlling the mobility of lead. A series of batch experiments are performed with granulated galena in $CO_2$ solutions under various experimental conditions for $CO_2$ concentration and reaction temperature. Results show that dissolution of galena is significantly enhanced under acidic environments so that both of equilibrium concentrations and dissolution rates of lead increase. For thermodynamic analysis on galena dissolution, the apparent rate constants and the activation energy for galena dissolution are calculated by applying rate law to experimental results. The apparent rate constants are $6.71{\times}10^{-8}mol/l{\cdot}sec$ at $15^{\circ}C$, $1.77{\times}10^{-7}mol/l{\cdot}sec$ at $25^{\circ}C$, $3.97{\times}10^{-7}mol/l{\cdot}sec$ at $35^{\circ}C$ and the activation energy is 63.68 kJ/mol. The galena dissolution is suggested to be a chemically controlled surface reaction, and the rate determining step is the dissociation of Pb-S bond of surface complex.

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.37-44
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• 2015

We proposed the improved Langmuir adsorption relations considering volume change effect of coal matrix during primary production of CBM and Enhanced-CBM with injection of carbon dioxide or CCS in coalseam but also volumetric strain. To verify this model, experimental data of pure gas adsorption such as $CO_2$, $CH_4$, and $N_2$ on coals were used to compare conventional Langmuir model with this model. From the results, we obtained that the larger adsorption capacity of coal and the higher adsorption affinity of gas, the larger error occur with Langmuir model. Using this model, however, we found not only substantially better fit in all condition but also reasonable volumetric strain of the coal matrix. We also applied this volume modified pure gas adsorption model to the IAS model to describe gas adsorption and volumetric strain for mixed gas. This modified-IAS model fitting experimental data by Hall et al(1994) improved accuracy of mixed gas adsorption calculation compared with conventional model.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.351-356
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• 2016

The carbon capture and storage (CCS), which collects and stores carbon dioxide in a geological site, is a promising option to mitigate climate change. However, there is the possibility of carbon dioxide leakage from the soil in the steps of collecting, transporting, and storing. To ensure the feasibility of this technology, it is important to monitor the leakage of carbon dioxide and to assess the potential impacts. As plants are sensitive to the changes in carbon dioxide in the soil environment, we can utilize plant parameter to detect the carbon dioxide leakage. Currently, chlorophyll a content is a conventional index indicating the changes in plants, however, this method is labor intensive and it only utilizes a small portion of leaves. To overcome its limitations, a simple spectroscopic parameter, DGCI (dark green color index), was suggested as an easy and quick indicator. In this study, we compared the values of chlorophyll a contents with DGCI from the experiment investigating the impacts of high underground $CO_2$ on grape plants. Results suggest that DGCI had high correlation with chlorophyll a contents and it has high potential to be utilized as an easy indicator to monitor plants' responses to $CO_2$ treatment.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.558-567
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• 2022

The evolution of temperature and thermal stress in a granite specimen is studied via heating experiment in the context of a high-level radioactive waste repository. A heating condition based on the decay-induced heat is applied to a cubic granite specimen to measure the temperature and stress distributions and their evolution over time. The temperature increases quickly due to heat conduction along the heated surfaces, but a significant amount of thermal energy is also lost through other surfaces due to air convection and conduction into the loading machine. A three-dimensional finite element-based model is used to numerically reproduce the experiment, and the thermo-mechanical coupling behavior and modeling conditions are validated with the comparison to the experimental results. The most crucial factors influencing the heating experiment are analyzed and summarized in this paper for future works.

• Tunnel and Underground Space
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• v.34 no.2
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• pp.127-142
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• 2024

The robustness of a numerical method means that its computational performance is maintained under various modeling conditions. New numerical methods or codes need to be assessed for robustness through benchmark testing. The TOUGH-FLAC modeling approach has been applied to various fields such as subsurface carbon dioxide storage, geological disposal of spent nuclear fuel, and geothermal development both domestically and internationally, and the modeling validity has been examined by comparing the results with experimental measurements and other numerical codes. In the present study, a benchmark test of the TOUGH-FLAC approach was performed based on a coupled thermal-hydro-mechanical behavior problem with an analytical solution. The analytical solution is related to the temperature, pore water pressure, and mechanical behavior of a fully saturated porous medium that is subjected to a point heat source. The robustness of the TOUGH-FLAC approach was evaluated by comparing the analytical solution with the results of numerical simulation. Additionally, the effects of thermal-hydro-mechanical coupling terms, fluid phase change, and timestep on the computation of coupled behavior were investigated.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.21-27
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• 2022

For carbon neutrality, interest in R&D and infrastructure construction for hydrogen energy, an eco-friendly energy source, is growing worldwide. In particular, for hydrogen stations installed in downtown areas, underground hydrogen infrastructure are being considered to increase a safety distance from hydrogen tank explosions to adjacent structures. In order to design an appropriate location and depth of the underground hydrogen infrastructure, it is necessary to evaluate the impact of the explosion of the underground hydrogen infrastructure on adjacent structures. In this paper, a numerical model was developed to analyze the effect of the underground hydrogen infrastructure explosion on adjacent structures, and the over pressure of the hydrogen tank was evaluated using the equivalent TNT (Trinitrotoluene) model. In addition, parametric analysis was performed to estimate the stability of adjacent structures according to the construction conditions of the underground hydrogen infrastructure.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.329-340
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• 2013

A geologic survey of the Bukpyeong and Pohang basins, as candidate basins for the geological storage of $CO_2$, was performed to evaluate storage capacity and security. To analyze the mechanical stability of the storage reservoir and cap rocks, we measured the porosity, seismic velocity, uniaxial strength, internal frictional angle, and Young's modulus of core samples recovered from the two basins. It is costly and sometimes impossible to conduct tests over the entire range of drill holes, and continuous logging data do not yield the mechanical parameters directly. In this study, to derive the mechanical properties of geologic formations from the geophysical logging data, we determined the empirical relations between the physical properties (seismic velocity, porosity, and dynamic modulus) and the mechanical properties (uniaxial strength, internal friction angle) of the core samples. From the comparison with our core test data, the best fits to the two basins were selected from the relations suggested in previous studies. The relations between uniaxial strength, Young's modulus, and porosity of samples from the Bukpyeong and Pohang basins are more consistent with certain rock types than with the locality of the basins. The relations between the physical and mechanical properties were used to estimate the mechanical rock properties of geologic formations from seismic logging data. We expect that the mechanical properties could also be used as input data for a modeling study to understand the mechanical instability of rock formations prior to $CO_2$ injection.