## 3 Results  
### Physical Properties of Impure Gas  
MMP, Density, and Viscosity  
A change in the physical properties of the gas will impact the displacement and sweep efficiencies. The slim-tube simulation method was conducted to determine CO\({}_{2}\) MMP for the reservoir fluid, which was matched against the experimental data. It has been recognized that MMP between the oil and injected solvents depends on the purity of CO\({}_{2}\). In general, the component of H\({}_{2}\)S or intermediate hydrocarbons such as C\({}_{3}\), C\({}_{4}\) reduce the MMP, whereas the presence of N\({}_{2}\) and CH\({}_{4}\) in the CO\({}_{2}\) stream increase the MMP [38]. The MMP between CO\({}_{2}\) mixtures containing 10% of each representative impurity in the CO\({}_{2}\) such as CH\({}_{4}\), H\({}_{2}\), N\({}_{2}\), and O\({}_{2}\), and W3 fluid was calculated. The results from simulated MMPs using the slim-tube method with different mole fractions of CO\({}_{2}\) and impurities are shown in Table 8. Impurities of CH\({}_{4}\), H\({}_{2}\), N\({}_{2}\), and O\({}_{2}\) effected an increase in the MMP, while H\({}_{2}\)S decreased the MMP. Therefore, CO\({}_{2}\) containing either components that increase (CH\({}_{4}\), H\({}_{2}\), N\({}_{2}\), O\({}_{2}\)) or decrease (H\({}_{2}\)S) MMP changes the miscibility.  
Table 9 presents the impact of impure gas in the CO\({}_{2}\) on the gas properties. The MMP of pure CO\({}_{2}\) for this reservoir fluid was determined to be 13,900 kPa. Presence of the impure gas content increased the MMP to 19,927 kPa, while decreasing the density and viscosity, and had a negative impact on the miscibility of the gas and oil. The density of the injection gas impacted both injection rate and pressure. Density changes due to the addition of impurities reduced the gas compressibility and caused differences in bottomhole pressure at given injection wellhead pressure.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Depth (ft) & 4050 \\ Initial reservoir pressure (psi) & 4000 \\ Reservoir temperature (\({}^{\circ}\)F) & 145 \\ Permeability in I, J, K-direction (md) & 50, 50, 5 \\ Porosity (\%) & 0.3 \\ Initial oil saturation (\%) & 0.7 \\ Initial water saturation (\%) & 0.3 \\ Producing bottom hole pressure (psi) & 2000 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Reservoir initial and operating conditions.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Components** & **MMP (kPa)** \\ \hline CO\({}_{2}\) 100\% & 13,900 \\ CO\({}_{2}\) 90\% + CH\({}_{4}\) 10\% & 18,616 \\ CO\({}_{2}\) 90\% + H\({}_{2}\) 10\% & 16,079 \\ CO\({}_{2}\) 90\% + N\({}_{2}\) 10\% & 18,933 \\ CO\({}_{2}\) 90\% + O\({}_{2}\) 10\% & 14,555 \\ CO\({}_{2}\) 90\% + Ar\({}\) 10\% & 18,650 \\ CO\({}_{2}\) 90\% + H\({}_{2}\)S 10\% & 12,714 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Minimum miscibility pressures (MMPs) calculation using the slim-tube method with various CO\({}_{2}\) mixtures.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Case 1** & **Case 2** \\ \hline Minimum Miscibility Pressure (kPa) & 13,900 & 19,927 \\ Density (kg/m\({}^{3}\)) & 689 & 552 \\ Viscosity (mPa*s) & 0.0702 & 0.0493 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Minimum miscibility pressures (MMPs) calculated using the slim-tube method with pure and impure CO\({}_{2}\) mixtures.