Advancement Perspectives in Enhancing Heavy Oil Recovery Using N₂- and CO₂-Assisted Steam Injection: Exploring Molecular Interactions to Field Applications

There has been some success with nitrogen (N2), carbon dioxide (CO2), and steam used in enhancing heavy oil recovery, particularly in their synergistic application. However, the synergistic applying N2-assisted CO2, N2-assisted steam or CO2-assisted steam injections remains compromised under the extreme conditions of deep reservoirs, such as overly high temperature and pressure environments, fluctuating salinity levels, sediment interactions, and formation heterogeneity. Incorporating N2 and CO2 into steam yields a transformative potential, revealing enhanced rheological behaviors, improved viscosity reduction, enhanced mobility, optimized sweep efficiency, enhanced interfacial tension (IFT) reduction, reduced heat loss, increased displacement efficiency, and boosted thermal efficiency, ultimately leading to significantly improved heavy oil recovery efficiency, all attributable to the synergistic effects of their components. In this work, the performance of N2 and CO2-assisted steam injection and the factors that impair their effectiveness were highlighted. Numerous N2 and CO2-assisted steam mechanisms, such as viscosity reduction, wettability alteration, IFT reduction, and improved thermal insulation on oil mobility and recovery, were illustrated. The synergistic interaction of N2/CO2-assisted steam injection to enhanced IFT reduction, viscosity alteration, pressure maintenance, wettability improvement, and permeability enhancement for optimizing recovery were also presented. In addition, the review highlighted the existing challenges, research gaps, and proposed potential interventions to bridge the gap between laboratory findings and scalable field applications. The study systematically examines (1) the rheological properties of N2/CO2-assisted steam injection, (2) synergistic gas-steam injection mechanisms, (3) the influence of formation water salinity, and (4) technical and economic feasibility analysis, providing a holistic perspective from molecular interactions to field-scale applications.