## 3 Results  
### Fluid Modeling  
Weyburn W3 fluid data [43; 44] is used as the experimental data for fluid modeling in the present study. Since the Weyburn Field in Saskatchewan, Canada, reached the economic limit of waterflooding and became a target for CO\({}_{2}\)-EOR, extensive experiments have been conducted to investigate the interactions between oil and CO\({}_{2}\) for CO\({}_{2}\)-EOR and CCS purposes [43; 45].  
The fluid composition of W3 experimental data and corresponding input EOS parameters used for fluid modeling are summarized in Table 1, while Table 2 presents the oil properties calculated via a regression method using the Peng-Robinson Equation of State (PR-EOS) and matched against the experimental data to increase the reliability of the compositional reservoir simulation [37; 38]. The MMP is then estimated using the multiple-mixing-cell method [28]. An examination of the bottom row of Table 2 indicates that the MMP datum associated with CO\({}_{2}\) in W3 fluid at a reservoir temperature of 63 \({}^{\circ}\)C is 14,196 kPa (second column, Table 2), while the calculated value is 13,872 kPa (third column, Table 2), thus indicating a 2.3% error against the W3 data.  
The MMPs calculated using the multiple-mixing-cell method with varying mole fraction ratios of CO\({}_{2}\) to CH\({}_{4}\) are presented in Table 3. Here, it can be seen that the MMP increases with increasing mole fraction of CH\({}_{4}\) in the CO\({}_{2}\) injection stream, thus indicating that CH\({}_{4}\) reduces the displacement efficiency compared to that of pure CO\({}_{2}\) injection, in agreement with previous experimental studies [13; 14].  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Component** & **Composition** & \begin{tabular}{c} **Critical Pressure** \\ \(p_{c}\) **(kPa)** \\ \end{tabular} & \begin{tabular}{c} **Critical Temperature** \\ \(T_{c}\) **(K)** \\ \end{tabular} & \
\begin{tabular}{c} **Accentric** \\ **Factor** \\ \end{tabular} &
\begin{tabular}{c} **Molecular** \\ **Weight** \\ \end{tabular} \\ \hline N\({}_{2}\) & 0.0207 & 3394.4 & 126.2 & 0.040 & 28.0 \\ CO\({}_{2}\) & 0.0074 & 7376.5 & 304.2 & 0.225 & 44.0 \\ H\({}_{2}\)S & 0.0012 & 8936.9 & 373.2 & 0.100 & 34.1 \\ Methane, C\({}_{1}\) & 0.0749 & 4600.2 & 190.6 & 0.008 & 16.0 \\ Ethane, C\({}_{2}\) & 0.0422 & 4883.9 & 305.4 & 0.098 & 30.1 \\ Propane, C\({}_{3}\) & 0.0785 & 4245.5 & 369.8 & 0.152 & 44.1 \\ Butane, C\({}_{4}\) & 0.0655 & 3722.7 & 416.5 & 0.185 & 58.1 \\ Pentane, C\({}_{5}\) & 0.0459 & 3379.4 & 464.9 & 0.239 & 72.1 \\ C\({}_{6-9}\) & 0.2156 & 3019.6 & 556.3 & 0.331 & 102.5 \\ C\({}_{10-17}\) & 0.2202 & 2017.5 & 692.2 & 0.584 & 184.0 \\ C\({}_{18-27}\) & 0.1027 & 1327.0 & 808.4 & 0.893 & 306.2 \\ C\({}_{28+}\) & 0.1252 & 1155.1 & 915.5 & 1.100 & 565.6 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Fluid composition of W3 experimental data and properties of each component used for the EOS calculation.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **W3** & **Fluid Model** & **Difference (\%)** \\ \hline Saturation pressure (kPa) & 4920 & 4780 & 2.85 \\ Oil density at saturation pressure (kg/m\({}^{3}\)) & 806.4 & 806.8 & \(-\)0.05 \\ Viscosity at saturation pressure (mPa\(\cdot\)s) & 1.76 & 1.75 & 0.57 \\ Formation volume factor (m\({}^{3}\)/m\({}^{3}\)) & 1.12 & 1.11 & 0.89 \\ API (\({}^{o}\)) & 31 & 34.8 & \(-\)12.26 \\ MMP with CO\({}_{2}\) (kPa) & 14,196 & 13,872 & 2.28 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of the W3 experimental data and fluid model properties.