ABSTRACT

This study focuses on evaluating the impact of varying continuous CO₂ injection rates and CO₂ impurity contents, such as N₂ and CH₄, on the Recovery Factor (RF) in the DF Field. Simulations were conducted using reservoir simulation with CO₂ injection rates of 1.3 MMSCFD, 2 MMSCFD, 3 MMSCFD, and 4 MMSCFD, as well as variations in CO₂ impurity mixtures, namely CO₂ 90% + N₂ 10%, CO₂ 90.1% + CH₄ 9.9%, and CO₂ 89.8% + N₂ 5.1% + CH₄ 5.1%. The results show that increasing the CO₂ injection rate is directly proportional to an increase in the recovery factor, with the highest recovery factor of 22.00% achieved in the 4 MMSCFD injection scenario. The effect of CO₂ impurities is clearly reflected in the recovery factor. The presence of N₂ increases the Minimum Miscibility Pressure (MMP), making miscible displacement more difficult to achieve and reducing microscopic displacement efficiency, which directly leads to a lower recovery factor compared to pure CO₂ injection. In contrast, CH₄ has a more moderate impact on the recovery factor, as it does not significantly disrupt miscibility and therefore maintains relatively stable sweep efficiency. The combination of CO₂ + N₂ yields the highest recovery factor at a 4 MMSCFD injection rate, reaching 17.00%, although this value remains lower than that of pure CO₂ injection.These results indicate that selecting the appropriate injection rate and controlling CO₂ impurities play a crucial role in enhancing oil production in heterogeneous reservoirs. The conclusion of this study is that choosing the optimal injection scenario can significantly improve oil recovery while minimizing operational risks related to sweep efficiency and fluid mobility in the reservoir.