Abstract
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.
