• Journal of Soil and Groundwater Environment
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• v.20 no.4
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• pp.73-82
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• 2015

Despite significant effects on macroscopic migration and distribution of CO₂ injected during geological sequestration, only limited information is available on wettability in microscopic scCO₂-brine-mineral systems due to difficulties in pore-scale observation. In this study, a micromodel had been developed to improve our understanding of how scCO₂ flooding and residual characteristics of porewater are affected by the wettability in scCO₂-water-glass bead systems. The micromodel (a transparent pore structure made of glass beads and glass plates) in a pressurized chamber provided the opportunity to visualize scCO₂ spreading and porewater displacement. CO₂ flooding followed by fingering migration and dewatering followed by formation of residual water were observed through an imaging system. Measurement of contact angles of residual porewater in micromodels were conducted to estimate wettability in a scCO₂-water-glass bead system. The measurement revealed that the brine-3M NaCl solution-is a wetting fluid and the surface of glass beads is water-wet. It is also found that the contact angle at equilibrium decreases as the pressure decreases, whereas it increases as the salinity increases. Such changes in wettability may significantly affect the patterns of scCO₂ migration and porewater residence during the process of CO₂ injection into a saline aquifer at high pressures.

• Journal of Soil and Groundwater Environment
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• v.21 no.3
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• pp.35-48
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• 2016

A micromodel was applied to estimate the effects of geological conditions and injection methods on displacement of resident porewater by injecting scCO₂ in the pore scale. Binary images from image analysis were used to distinguish scCO₂-filled-pores from other pore structure. CO₂ flooding followed by porewater displacement, fingering migration, preferential flow and bypassing were observed during scCO₂ injection experiments. Effects of pressure, temperature, salinity, flow rate, and injection methods on storage efficiency in micromodels were represented and examined in terms of areal displacement efficiency. The measurements revealed that the areal displacement efficiency at equilibrium decreases as the salinity increases, whereas it increases as the pressure and temperature increases. It may result from that the overburden pressure and porewater salinity can affect the CO₂ solubility in water and the hydrophilicity of silica surfaces, while the neighboring temperature has a significant effect on viscosity of scCO₂. Increased flow rate could create more preferential flow paths and decrease the areal displacement efficiency. Compared to the continuous injection of scCO₂, the pulse-type injection reduced the probability for occurrence of fingering, subsequently preferential flow paths, and recorded higher areal displacement efficiency. More detailed explanation may need further studies based on closer experimental observations.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.55-61
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• 2022

Carbon dioxide is one of the greenhouse gases in the atmosphere and much research is underperforming in reducing carbon dioxide. Geological carbon dioxide storage is considered the primary technique for global warming prevention. So, technic development for storing carbon dioxide is required. Using surfactant is considered an effective material for geological carbon dioxide storage. However, research on using surfactants for carbon dioxide sequestration is not enough. In this study, a 2D micromodel experiment depends on the surfactant type (sodium dodecyl sulfate and sodium dodecylbenzene sulfonate), concentration and carbon dioxide injection rate. As result, geological carbon dioxide sequestration efficiency is increased according to surfactant concentration and carbon dioxide injection rate increase. However, efficiency no more increases after critical concentration and rate.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.37-48
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• 2019

In geological $CO_2$ sequestration, the behavior of $CO_2$ within a reservoir can be characterized as two-phase flow in a porous media. For two phase flow, these processes include drainage, when a wetting fluid is displaced by a non-wetting fluid and imbibition, when a non-wetting fluid is displaced by a wetting fluid. In $CO_2$ sequestration, an understanding of drainage and imbibition processes and the resulting NW phase residual trapping are of critical importance to evaluate the impacts and efficiencies of these displacement process. This study aimed to observe migration and residual trapping of immiscible fluids in porous media via cyclic injection of drainage-imbibition. For this purpose, cyclic injection experiments by applying n-hexane and deionized water used as proxy fluid of $scCO_2$ and pore water were conducted in the two dimensional micromodel. The images from experiment were used to estimate the saturation and observed distribution of n-hexane and deionized water over the course drainage-imbibition cycles. Experimental results showed that n-hexane and deionized water are trapped by wettability, capillarity, dead end zone, entrapment and bypassing during $1^{st}$ drainage-imbibition cycle. Also, as cyclic injection proceeds, the flow path is simplified around the main flow path in the micromodel, and the saturation of injection fluid converges to remain constant. Experimental observation results can be used to predict the migration and distribution of $CO_2$ and pore water by reservoir environmental conditions and drainage-imbibition cycles.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.259-267
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• 2022

The rheological and penetration characteristics of sodium alginate and xanthan gum aqueous solutions were analyzed for the development of biopolymer-based injection materials. The results of viscosity measurements for the rheological characteristics analysis show that all aqueous biopolymer solutions exhibit a tendency for shear-thinning, i.e., the apparent viscosity decreases as the shear rate increases. In addition, a regression analysis using several models (Power-law, Casson, Sisko, and Cross) was applied to the shear-thinning fluid analysis results, the highest accuracy was determined by applying the power-law model. The micromodel experiment for the penetration characteristics analysis determined that all biopolymer aqueous solutions show higher pore saturation than water, and that pore saturation tends to increase as the flow rate and concentration increases. When comparing the rheological and penetration characteristics of the biopolymer aqueous solution used in this study, the xanthan gum aqueous solution showed a fully developed shear-thinning tendency, unlike the sodium alginate aqueous solution. This tendency is considered to have the advantage of enhancement injectability and pore saturation.

• Economic and Environmental Geology
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• v.51 no.3
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• pp.223-232
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• 2018

The viscous force of fluids and the capillary force acting on the pore network of the porous media are important factors determining the immiscible displacement during geological $CO_2$ sequestration, these were directly affected by geological formation conditions and injection conditions. This study aimed to observe the migration and distribution of injected fluid and pore water, and quantitatively investigate displacement efficiency on various injection temperatures. This study aimed to perform micromodel experiments by applying n-hexane used as a proxy fluid for supercritical $CO_2$. In this study, immiscible displacement process from beginning of n-hexane injection to equilibrium of the distribution of the n-hexane and pore water was observed. The images from experiment were used to observe the displacement pattern and estimate the areal displacment efficiency of the n-hexane. For investigate the affects of the injection temperatures on the migration in macroscopic, migration of n-hexane in single pore was analyzed. The measurement revealed that the displacement efficiency at equilibrium state decreases as the temperature increases. The result from experiments indicate that the temperatures can affect the displacement pattern by changing the viscous forces and the capillary forces. The experimental results could provide important fundamental information on reservoir conditions and fluid injection conditions during geological $CO_2$ sequestration.

• Journal of Soil and Groundwater Environment
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• v.23 no.1
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• pp.1-13
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• 2018

A series of experiments using transparent micromodels with an artificial pore network etched on glass plates was performed to investigate the effects of flow rate on the migration and distribution of resident wetting porewater (deionized water) and injecting non-wetting fluid (n-hexane). Multicolored images transformed from real RGB images were used to distinguish n-hexane from porewater and pore structure. Hexane flooding followed by immiscible displacement with porewater, migration through capillary fingering, preferential flow and bypassing were observed during injection experiments. The areal displacement efficiency increases as the injection of n-hexane continues until the equilibrium reaches. Experimental results showed that the areal displacement efficiency at equilibrium increases as the flow rate increases. Close observation reveals that preferential flowpaths through larger pore bodies and throats and clusters of entrapped porewater were frequently created at lower flow rate. At higher flow rate, randomly oriented forward and lateral flowpaths of n-hexane displaces more porewater at an efficiency close to stable displacement. It may resulted from that the pore pressure of n-hexane, at higher flow rate, increases fast enough to overcome capillary pressure acting on smaller pore throats as well larger ones. Experimental results in this study may provide fundamental information on migration and distribution of immiscible fluids in subsurface porous media.

• Journal of the Korean Geotechnical Society
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• v.35 no.4
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• pp.37-42
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• 2019

Hydrate dissociation is required to produce methane, which generates both water and methane. Thus, multiphase fluid flow and desalination are expected during methane production, which causes the fine migration and clogging in pores. The goal of this study is to explore the effects of both multiphase fluid flow and desalination on the migration and clogging of kaolin particles as typical fines. The results are as follows : (1) the larger the pore size is, the more mounting the critical clogging concentration is, (2) kaolin particles are more easily clustering and clogging in deionized water than salty water, and (3) the critical clogging concentration of kaolin in multiphase fluid flow is lower than in singlephase fluid flow. Therefore, clustering and clogging of kaolin within pore occur easily due to desalination and multiphase fluid flow when methane is produced from hydrates, and the efficiency of methane production is expected to decrease due to the degradation of permeability coefficient.

• Journal of the Korean GEO-environmental Society
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• v.24 no.6
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• pp.5-11
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• 2023

The engineering industry heavily relies on fossil fuels such as coal and petroleum to generate energy through combustion. However, this process emits carbon dioxide into the atmosphere, leading to global warming. To mitigate this issue, researchers have explored various methods to reduce carbon dioxide emissions, one of which is carbon dioxide underground storage technology. This innovative technology involves capturing carbon dioxide from industrial plants and injecting it into the saturated ground layer beneath the earth's surface, storing it securely underground. Despite its potential benefits, carbon dioxide underground storage efficiency needs improvement to optimize storage in a limited space. To address this challenge, our research team has focused on improving storage efficiency by utilizing surfactants. Furthermore, we evaluated how different carbon dioxide states, including gaseous, liquid, and supercritical, impact storage efficiency based on their respective pressures and temperatures within the underground reservoir. Our findings indicate that using surfactants and optimizing the injection rate can effectively enhance storage efficiency across all carbon dioxide states. This research will pave the way for more efficient carbon dioxide underground storage, contributing to mitigating the environmental impact of fossil fuels on the planet.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.63-70
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• 2023

Underground carbon dioxide (CO₂) storage emerges as a pivotal strategy for mitigating atmospheric CO₂ emissions and addressing global warming concerns. This study investigates techniques to optimize storage efficiency in aquifers, which stand out for their superior capacity compared to other geological layers. The focus is on the application of nonionic and anionic surfactants to enhance CO₂ storage efficiency within confined spaces. A specialized micromodel facilitating fluid flow observation was employed for the evaluation. Experimental results revealed a noteworthy minimum 40% increase in storage efficiency at the lowest injection rate when utilizing nonionic and anionic surfactants, in comparison to pure water injection. Interestingly, no significant variations in storage efficiency were observed based on the ionicity and concentration of the surfactants under investigation. These findings have implications for guiding the selection and concentration determination of surfactants in future underground CO₂ storage endeavors.