Optimizing Oil Recovery: A Sector Model Study of CO₂-Water-Alternating-Gas and Continuous Injection Technologies

Optimizing oil recovery from mature reservoirs remains a key challenge in the petroleum industry. This study evaluates the efficiency of CO2-WAG injection compared to continuous CO2 and water flooding using a sector model of the X Oil Field. A compositional reservoir simulator was employed to analyze oil recovery under water-wet and mixed-wet conditions, incorporating three-phase relative permeability and wettability effects. The results show that continuous CO2 flooding yields the highest oil recovery, with water-wet systems outperforming mixed-wet reservoirs. CO2-WAG injection provides a balanced approach, enhancing recovery while enabling CO2 sequestration, but remains less effective than continuous CO2 flooding. Water flooding, though the least efficient in terms of oil recovery, demonstrates long-term production stability. The gas–oil ratio (GOR) is notably higher in CO2-WAG, indicating gas breakthrough challenges. These findings emphasize the significant role of wettability in enhanced oil recovery (EOR) and suggest that continuous CO2 flooding is the most effective technique for maximizing production in heterogeneous reservoirs. This study contributes valuable insights for optimizing injection strategies, improving hydrocarbon recovery, and supporting sustainable reservoir management.