Sensitivity Analysis of Reservoir Characteristics and Flue Gas Composition for Enhanced Oil Recovery in Heterogeneous Reservoir

The success of enhanced oil recovery depends on optimizing various reservoir factors. While CO₂ and flue gas injections are common methods, they encounter challenges that require a deep understanding of reservoir characteristics and thorough analysis of pertinent parameters for effective mitigation. This study aimed to explore the synergistic relationship between flue gas compositions, reservoir characteristics, and injection rates for optimal oil recovery. Unlike prior studies that primarily examined the isolated effects of CO₂ or flue gas, this research uniquely investigates the combined impact of real-world flue gas compositions from industrial sources under heterogeneous reservoir conditions. Through extensive sensitivity analysis and simulated optimization, the study analyzed the effects of different flue gas compositions on oil recovery. The results showed that flue gases with higher concentrations of CO₂ and O₂ exhibited higher recovery factor, while the presence of water vapor had a negative impact. CO₂ injection yielded the highest recovery factor overall. The behavior of flue gases closely resembled the actual field reservoir pressure. The analysis highlighted the significant influence of reservoir temperature, porosity, permeability, and homogeneity on oil recovery and reservoir pressure. Higher temperatures showed a positive correlation with increased oil recovery for CO₂ injection, while flue gas injection demonstrated a more pronounced improvement. Additionally, decreasing porosity had a significant positive effect on oil recovery, with CO₂ injection achieving the highest recovery factor under conditions of half the initial porosity. Permeability variations had minimal impact on oil recovery and reservoir pressure, particularly in heterogeneous reservoirs with high porosity and permeability. Furthermore, improving reservoir homogeneity by reducing deviation in permeability range and porosity positively impacted oil recovery and reservoir pressure, with flue gases benefiting more from this improvement. In terms of injection rates, CO₂ injection proved more effective in maintaining reservoir pressure compared to flue gas injection, but flue gas injections demonstrated greater sensitivity to increased injection rates. Notably, flue gas 1 exhibited superior efficiency in improving oil recovery with increasing injection rates compared to other flue gases.