Steam-Assisted Gravity Drainage (SAGD) has emerged as one of the most reliable an‎d efficient thermal enhanced oil recovery (EOR) techniques for producing highly viscous heavy oil an‎d bitumen from unconventional reservoirs. With global dependence shifting increasingly toward unconventional petroleum resources, optimizing SAGD performance has become a strategic priority for operators, particularly in geologically complex reservoirs where fluid–rock interactions, heat transfer behavior, an‎d multiphase flow mechanisms strongly influence recovery outcomes. The success of SAGD depends not only on well architecture an‎d operational controls but also—critically—on fluid properties such as oil composition, viscosity-temperature behavior, initial oil saturation, an‎d the thermophysical characteristics of injected steam. This study provides an integrated an‎d systematic assessment of these fluid properties by combining numerical simulation using CMG-STARS, experimental rheological eva‎luation, an‎d an extensive literature review. The research further explores steam quality, subcool management, an‎d dynamic steam chamber growth behavior under varying reservoir heterogeneities. Additional emphasis is placed on asphaltene precipitation tendencies, temperature-dependent viscosity gradients, steam conformance challenges, an‎d the impact of reservoir layering on heat distribution an‎d oil mobilization. Ultimately, the findings of this work aim to enhance design strategies an‎d operational decision-making by offering a detailed understan‎ding of how each fluid parameter interacts within the thermal recovery environment, thereby enabling more efficient, economical, an‎d sustainable SAGD development in heavy oil reservoirs.

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حميدرضا شاه وردي , محسن محمدي