## 3 Results and Discussion  
### Experiment 1: The Thermal Reaction Process  
Figure 5 shows the RTO results of air composition variation. As shown in Figure 5, the main components of the oxidation reaction off-gas for both heavy oils were CO\({}_{2}\) and CO. Figure 5 shows that when the reaction temperature reaches 200-300 \({}^{\circ}\)C, the curve exhibits the first peaks of O\({}_{2}\) consumption and the production of CO and CO\({}_{2}\). This indicates that, at this temperature range, low-temperature oxidation reactions were most intense. As the reaction temperature increases to 400-500 \({}^{\circ}\)C, the curve shows the second peaks of the reaction. However, compared to the first set of peaks, the changes in the components in the air were relatively small. This indicates that, under high-temperature conditions, another round of oxidation reactions occurred but with lower intensity. As shown in Figure 5(a1-c1), with increasing pressure, the partial pressure of oxygen increased, resulting in a larger contact area between oxygen and crude oil. Intense oxidation reactions occurred at the gas-liquid and gas-solid interfaces, accelerating the rate of crude oil oxidation. This led to a more thorough oxidation of crude oil. Oxygen consumption during the oxidation stage increased, and the reaction time decreased. As shown in Figure 5(a1,a2,c1,c2), under the same experimental conditions, the low-temperature oxygen consumption peak for the oil sample G was in the range of 1.2% to 2.2%. Oil sample M had an oxygen consumption rate close to 8% under 5.0 MPa conditions. It had a stronger low-temperature oxygen consumption capacity, and the higher the pressure, the greater the difference in oxygen consumption. According to the variation curve of air injection components under different pressures, the experimental data for the G Block crude oil at 3.0 MPa were extracted, and the integration of these data across the entire reaction range yielded an atomic ratio of H/C at 1.802. The atomic ratio of H/C for low-temperature oxidation was determined as 3.125, while for  
Figure 5: The RTO results of air composition variation: (**a1**) oil sample G with 1.0 MPa; (**b1**) oil sample G with 3.0 MPa; (**c1**) oil sample G with 5.0 MPa; (**a2**) oil sample M with 1.0 MPa; (**b2**) oil sample M with 3.0 MPa; (**c2**) oil sample M with 5.0 MPa. high-temperature oxidation, it was 0.733. Using these values, the key reaction equations characterizing the combustion process were determined as follows:  
Figure 6 shows the oxidation stages division of air composition variation at 3.0 MPa with different oil samples. The oxidation stages are delineated at the inflection points of the curves, and based on the results shown in Figure 6, the oxidation process of crude oil can be summarized in three stages as follows:  
1. **Low-temperature oxidation (LTO) stage:** In this stage, the dominant reaction in the oxidation process is light oil burning. The light components in crude oil undergo intense oxidation reactions, and hydrocarbons undergo oxygenation reactions, leading to the formation of alcohols, aldehydes, ketones, esters, etc. This is typically accompanied by the formation and breaking of carbon-oxygen and carbon-hydrogen bonds. Due to the higher content of light components in the M oil sample, the reaction intensity of the M oil sample was higher than that of the G oil sample in this stage. As the temperature increased, the oxidation reaction rate gradually decreased, laying the foundation for the subsequent stages. 2. **Fuel deposition (FD) stage:** In this stage, the dominant reaction is heavy oil burning, accompanied by heavy oil cracking. The consumption of O\({}_{2}\) slows down. This stage is characterized by the oxidative cracking of heavy oil, leading to the formation of coke and light hydrocarbons as fuels for the HTO phase. Typically, carbon-carbon and carbon-hydrogen bonds break, resulting in the formation of radicals and carbon-carbon double bonds. This stage provides the basis for high-temperature oxidation. 3.