Non-Condensable Gas Injection in Late-Stage SAGD: A Critical Review

Steam-assisted gravity drainage (SAGD) makes a significant contribution to Canada’s heavy oil production. Yet, it faces notable efficiency challenges during late-life stages, characterized by increased Steam–Oil Ratios and environmental concerns. Non-condensable gas (NCG) injection has emerged as a promising strategy to address these issues, particularly in late-life and post-steam SAGD phases. This review systematically examines the mechanisms, phase behavior, thermochemical interactions, field applications, and operational impacts of injecting NCGs such as methane, nitrogen, and carbon dioxide. This work exclusively synthesizes the application of NCG injections in mature SAGD reservoirs while outlining existing challenges. It delivers a unified perspective on this domain, introducing practical insights to improve NCG injection efficiency. Critical analysis of the existing literature reveals key benefits, including reservoir pressure maintenance, steam chamber stabilization, and viscosity reduction. However, literature gaps persist regarding long-term field-scale validation, complex drive mechanisms at the steam chamber flanks, thermochemical reactions, interactions with geological heterogeneity, and detailed thermodynamic modeling under non-equilibrium conditions. Emphasizing these gaps underscores the importance of further research and integrated modeling to optimize NCG utilization, thus enhancing recovery efficiency, reducing environmental footprints, and extending reservoir life.