## 4 Simulations
### The Impact of Activation Energies  
Figure 13 shows the oil recovery results under different activation energies. As shown in Figure 13a-c, during the oxidation process, with an increase in the activation energy of light oil burning, the early daily oil production decreased and later gradually increased. As for heavy oil burning and heavy oil cracking, an increase in activation energy led to an initial increase in daily oil production, but it reached a point where no further increase was observed. The changes in the activation energy of these three reactions had a relatively small impact on the final oil recoveries. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Effective** & \multicolumn{3}{c}{**Grid Size (m)**} & \multicolumn{3}{c}{**Permeability (mD)**} & \multicolumn{1}{c}{**Depth**} & \multicolumn{1}{c}{**Temperature**} & \multicolumn{1}{c}{**Pressure**} & \multicolumn{1}{c}{**Porosity**} & \multicolumn{1}{c}{**Oil Saturation**} & \multicolumn{1}{c}{**Oil Viscosity**} \\ \cline{2-11}
**Grids** & **I** & **J** & **K** & **Transverse** & **Vertical** & **(m)** & **(\({}^{\circ}\)C)** & **(MPa)** & **(\%)** & **(\%)** & **(mPa-s)** \\ \hline \(21\times 21\times 5\) = 2205 & 10 & 10 & 2 & 1200 & 600 & 1000 & 50 & 10 & 20 & 40 & 4440 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Key parameters of the numerical simulation model. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Reaction Models** & \multicolumn{3}{c}{**Pre-Exponential**} & \multicolumn{3}{c}{**Activation Energy**} & \multicolumn{1}{c}{**Reaction Heat**} \\  & **Factor A (kPa-s)\({}^{-1}\)** & **E (kJ/mol)** & **Release (J/mol)** \\ \hline Heavy oil cracking & \(4.17\times 10^{9}\) & \(182\) & & & & \\ Heavy oil burning & \(3.02\times 10^{6}\) & \(64\) & \(1.53\times 10^{6}\) & \(1.59\times 10^{7}\) & \(6.59\times 10^{7}\) & \(6.16\times 10^{5}\) & \\ Light oil burning & \(1.20\times 10^{7}\) & \(74\) & \(6.59\times 10^{7}\) & \(6.16\times 10^{5}\) & \\ Coke oil burning & \(8.17\times 10^{5}\) & \(59\) & \(6.16\times 10^{5}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: The numerical simulation of reaction kinetic parameters. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Component** & **H\({}_{2}\)O** & **Heavy Oil** & **Light Oil** & **CO\({}_{2}\)** & **CO** & **N\({}_{2}\)** & **O\({}_{2}\)** & **Coke** \\ \hline Molecular weight (g\(\cdot\)mol\({}^{-1}\)) & 18 & 458 & 120 & 44 & 28 & 28 & 32 & 13 \\ Critical pressure (kPa) & 22048 & 827 & 2110 & 7376 & 3496 & 3394 & 5046 & \\ Critical temperature (\({}^{\circ}\)C) & 374 & 614 & 344 & 21 & \(-140\) & \(-147\) & \(-119\) & \\ Equilibrium constant KV1 (Pa) & 0 & 0 & \(3.5\times 10^{6}\) & \(8.6\times 10^{6}\) & & & & \\ Equilibrium constant KV4 (\({}^{\circ}\)C) & 0 & 0 & \(-3818\) & \(-3103\) & & & & \\ Equilibrium constant KV5 (\({}^{\circ}\)C) & 0 & 0 & \(-273\) & \(-273\) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: The parameters of each component in numerical simulation. According to the results in Figure 13d, the variation in the activation energy of coke oil burning significantly influenced ISC, and the oil recoveries differed. When the activation energy was greater than 59 kJ/mol, an increase in the activation energy of coke oil burning led to an initial increase in daily oil production and ultimately an increase in the recovery factor. However, when the activation energy increased to 179 kJ/mol, a downward trend was observed in the final oil recoveries. This is because this reaction mainly occurred in the HTO stage. An excessively small activation energy clearly did not occur. However, when the activation energy was too high, the combustion zone temperature increased rapidly, accelerating the reaction. This resulted in an insufficient oxygen supply and an incomplete reaction, leading to a decrease in the final oil recoveries. Therefore, in the numerical simulations of heavy oil ISC, the activation energy for coke oil burning had to be in the range of 60 to 150 kJ/mol.