Seo, Seokju

Carbon capture and sequestration (CCS) has been considered a promising technology for mitigating heavy atmospheric carbon dioxide (CO2) concentration as an immediate response to global climate change and ocean acidification. Despite various previous studies on CCS, there has been a paucity of research to overcome many of the challenges. In geological carbon sequestration, there are two major issues in achieving a feasible means of storing CO2. The first is the slow reaction of carbonic acid (H2CO3) formation from the reaction between injected CO2 and brine. Another technical challenge to the realization of industrial-scale carbon sequestration is the drying-out of brine induced by CO2 advection. The resident brine near a wellbore area is rapidly evaporated while precipitating significant amounts of salt at pores when gaseous CO2 is continuously injected into these aquifers. On the other hand, in industrial post-carbon capture processes, monoethanolamine (MEA) has been dominantly used as an absorption solvent. However, it generates significant amounts of toxic wastewater containing chemicals difficult to treat. The objectives of this thesis are to address these challenges in CCS, making the CCS technology feasible and competitive. An innovative method for geologic carbon sequestration, namely nickel nanoparticles (Ni NPs) addition to the injection fluid was developed and evaluated, to address issues of the slow reaction in deep saline aquifers. The catalytic activity of Ni NPs was evaluated using the microfluidic technique to confirm their possibility of additive for enhancing CO2 hydration in deep saline aquifers. First of all, to achieve acceleration of CO2 dissolution under reservoir-specific conditions, the catalytic effect of Ni NPs was investigated by monitoring change in CO2 bubble size at various Ni NPs concentration, pH, and different levels of salinity. Then, steric stabilization of Ni NPs by adsorbing polymers has been studied to further enhance Ni NPs’ catalytic activity. Second, to overcome the brine drying-out challenge, a new strategy of sequential water injection with CO2 was proposed. This sequential injection strategy showed great potential for preventing aquifer formation damage by decreasing brine drying-out and enhancing CO2 dissolution significantly. Lastly, the CO2 capturing performance of Ni NPs as a possible additive in an MEA solvent was evaluated to meet CO2 reduction and environmental protection demands. The results were promising: the catalytic potential of Ni NPs accelerates the average CO2 absorption rate by 34% and 54% in the limited mixing and the high mixing conditions, respectively. The results presented in this dissertation could help alleviate global concerns raised by CCS technology and would offer strategies for stable CCS technology with improved efficiency.

Geologic storage of carbon dioxide (CO2) into deep
saline aquifers is a promising strategy for mitigation
of global atmospheric CO2 levels-a main cause of
climate change. These aquifers have the capacity
to safely store significant amounts of CO2 and are
available worldwide. As such, reaction dynamics and
multiphase transport accompanying CO2 injection in
deep aquifers are important to understanding CO2
sequestration processes and therefore they have
been extensively studied. Despite the comprehensive
findings, there are still urgent needs for understanding
of interactions between injected CO2 and
resident fluids since these interactions could determine
the total CO2 storage rate and capacity. The
objective of this study is to investigate fundamental
physics of water evaporation at different salinities under the CO2-rich environment. Microfluidic techniques
visualize and quantify evaporation behavior
of water in real-time in a simple 1D microchannel
geometry. The detailed CO2-water interactions and
underlying physics will be discussed.

More than 1 trillion barrels of oil deposited worldwide
is heavy oil and natural bitumen. Due to their
high viscosity and high density, extraction efficiency
of heavy oil and bitumen from natural reservoirs
is known to be less than 5% with the conventional
primary recovery methods. To increase their recovery
efficiency, a technique, known as enhanced oil
recovery, has been developed using nanoparticles,
surfactant, dispersant, and polymers. Among these
materials, surfactants and dispersants lower interfacial
tension between oil and the resident fluid; therefore
enhance mobilization of oil. The objective of this
project is to further improve the recovery efficiency
of heavy oil by a combined effect of surfactant and
dispersant. When the mixture of surfactant and dispersant
in an aqueous solution is injected to oil-rich
porous media, microfluidic visualization techniques
will be employed to investigate the overall recovery
rate. The possibility and effectiveness of the proposed idea will be discussed.