Carbon Dioxide Emissions and Utilization in Enhanced Oil Recovery

Carbon dioxide (CO2) emission substantially contributes to the global warming. Its anthropogenic effects account for about two-third of the overall environmental pollutions. In this thesis, we present and compare, in several new and unique ways, the CO2 emission in selected populated countries in all continents, which are known as highly active in fossil and/or renewable energy production/use. The emitted gas has been utilized in many industrial fields. One of the most useful ways to mitigate CO2 emissions is the employment in enhanced oil recovery (EOR) to increase the production of depleted oil reservoirs. One of the main mechanisms contributing to EOR processes using supercritical carbon dioxide (sc-CO2) is alterations in the oil-water interfacial properties. However, it has been a challenge to experimentally investigate such effects. We performed molecular dynamics (MD) simulation to explore these alterations. We studied the role of sc-CO2 in changing the interfacial and transport properties of the water-decane system. It was observed that sc-CO2 accumulates at the interface which leads to a reduction in the interfacial tension (IFT) of the water-decane system. Our further analysis of such accumulation showed that the relative density, ratio of sc-CO2 density at the interface to sc-CO2 bulk density, decreases as the overall sc-CO2 mole fraction increases. Moreover, our investigation indicated that sc-CO2 forms a film between the two phases which displaces decane molecules away from the interface. Furthermore, we found that as sc-CO2 mole fraction increase, the decane diffusion coefficient increase. In addition to the interfacial properties alterations, a problem could be arising from sc-CO2 injection process which is the heaviest oil end (asphaltene) aggregation. In this thesis, MD simulation was also employed to investigate the effect of CO2 injection for EOR on various oils-containing asphaltenes at reservoir conditions. Three different asphaltene models were considered representing the diversity of asphaltene structures. The oil phase was assumed to be ortho-xylene, which is the best hydrocarbon solvent for asphaltenes. Simulation results showed that the asphaltene structure had a significant effect on its aggregation onset. Asphaltenes with a single aromatic core and short aliphatic chains have high affinity to aggregate when the CO2 concentration is high enough. The driving force of the aggregation is the core-core as well as hydrogen bonds (H-bonds) interactions between asphaltene molecules. On the other hand, the asphaltene with long aliphatic chains has low affinity to start aggregate due to steric repulsions. The third asphaltene model, which is a flexible molecule with two aromatic cores, was slightly affected by the increase of CO2 concentration. This was because of the molecules flexibility which enabled it to interact through H-bonds and core-core interactions in the same molecule.