Browsing by Author "Wang, Xiaoqing"

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    Effect of Residual Oxygen in Carbon Dioxide on Swan Hills Light Oil
    (2014-09-30) Wang, Xiaoqing; Moore, Robert Gordon; Mehta, Sudarshan
    Low Temperature Oxidation (LTO) reactions are known to modify the composition and properties of crude oils during air injection process such as In Situ Combustion/High Pressure Air Injection. What is less understood is the effect of these reactions when residual oxygen is present in a CO2 stream that is injected into a light oil reservoir during an EOR/CO2 sequestration process. The objective of this study is to examine the compositional changes of a sample of Swan Hills light oil due to low temperature oxidation reactions during CO2 flooding. The experimental data were generated by Jia (2007), in which CO2 was injected into Swan Hills light oil with oxygen as an impurity. The experiments were performed in batch reactors under different temperatures, initial pressures, oxygen concentrations in CO2, and times. Kinetic model development for light oil in this research is based on Jia’s Athabasca bitumen LTO model. The model proposed in this thesis involves phase behavior and mass transfer process during the mixing of the injected fluid and the light oil. Oxygen addition and oxygen induced cracking reactions were assumed to happen in the hydrocarbon rich phase with combustion reactions occurring in both the hydrocarbon rich and CO2 rich phases. This model describes detailed kinetic mechanisms and concentration changes of individual pseudo-components during the LTO reactions. To simplify the calculation process, the hydrocarbon is characterized in terms of maltenes, asphaltenes and coke. The model results show that for light oil LTO reactions, phase behavior plays an important role. The asphaltenes product may restrict oxygen from transferring from one phase to another at low temperatures. Five reactions were proposed and the kinetic parameters were optimized to meet satisfactory results.
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    Identification and Cultivation of Exopolysaccharide-Degrading Bacteria in Two Soils
    (2013-09-24) Wang, Xiaoqing; Dunfield, Peter
    In this study, we hypothesized that bacterial exopolysaccharides (EPS) may serve as energy substrates for K-selected bacteria in soils, and we would be able to identify and culture previously uncultured species using various EPS as growth substrates. The exopolysaccharides gellan, indican_2, and cellulose were produced by the bacteria Sphingomonas elodea (ATCC 31461), Beijerinckia indica (ATCC 9039) and Gluconacetobacter xylinus (ATCC 53524) respectively. Two experiments were performed using these exopolysaccharides (EPS) as growth substrates. The first experiment involved detecting EPS-degrading bacteria by using a stable isotope probing technique. 13C labeled EPS were used as growth substrates for Big Hill Spring (BHS) and Paint Pots mound (PP) soil samples. EPS-degrading bacteria were identified using DNA density ultracentrifugation coupled with 454-pyrosequencing of the 16S rRNA genes recovered from 13C-labelled DNA fractions. Several uncultured Xanthomonadaceae sp. were enriched on cellulose (produced by G. xylinus) during incubation from BHS soil and several previously uncultured Planctomycetes were highly enriched on indican_2 (produced by B. indica) incubation from PP soil. The second experiment was to isolate novel bacteria by using gellan or indican_2 as sole carbon sources. Based on cultivation results, we found several previously uncultured bacteria could be identified and isolated from our gellan (produced by S. elodea) and indican_2 plates. For instance, we successfully isolated previous uncultured Acidobacteria by using gellan and indican_2 as our carbon source. All in all, in this study, we found some previously uncultured bacteria belonging to the groups of Acidobacteria, Verrucomicrobia, Planctomycetes, Chloroflexi, Actinobacteria, Cyanobacteria, Proteobacteria, Bacteroidetes, Armatimonadetes and Candidate division OD1, which are readily enriched or cultured using these EPS substrates. These poorly understood groups, especially some members of Planctomycetes, showed preference for our EPS indican_2. The research results indicate that using novel EPS as carbon sources might be a new way to improve current cultivation techniques.