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공극 규모에서의 초임계상 이산화탄소 거동 가시화를 위한 마이크로모델의 개발과 적용
박보경,이민희,왕수균,Park, Bogyeong,Lee, Minhee,Wang, Sookyun 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.4
Despite significant effects on macroscopic migration and distribution of CO<sub>2</sub> injected during geological sequestration, only limited information is available on wettability in microscopic scCO<sub>2</sub>-brine-mineral systems due to difficulties in pore-scale observation. In this study, a micromodel had been developed to improve our understanding of how scCO<sub>2</sub> flooding and residual characteristics of porewater are affected by the wettability in scCO<sub>2</sub>-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 scCO<sub>2</sub> spreading and porewater displacement. CO<sub>2</sub> 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 scCO<sub>2</sub>-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 scCO<sub>2</sub> migration and porewater residence during the process of CO<sub>2</sub> injection into a saline aquifer at high pressures.
초임계상 이산화탄소 주입으로 인한 공극수 대체에 관한 공극 규모의 마이크로모델 연구
박보경,이민희,왕수균,Park, Bogyeong,Lee, Minhee,Wang, Sookyun 한국지하수토양환경학회 2016 지하수토양환경 Vol.21 No.3
A micromodel was applied to estimate the effects of geological conditions and injection methods on displacement of resident porewater by injecting scCO<sub>2</sub> in the pore scale. Binary images from image analysis were used to distinguish scCO<sub>2</sub>-filled-pores from other pore structure. CO<sub>2</sub> flooding followed by porewater displacement, fingering migration, preferential flow and bypassing were observed during scCO<sub>2</sub> 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 CO<sub>2</sub> solubility in water and the hydrophilicity of silica surfaces, while the neighboring temperature has a significant effect on viscosity of scCO<sub>2</sub>. Increased flow rate could create more preferential flow paths and decrease the areal displacement efficiency. Compared to the continuous injection of scCO<sub>2</sub>, 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.