Research on heat distribution and heat efficiency improvement in the middle and late stages of SAGD

Abstract Challenges faced in heavy oil development include low efficiency in heat utilization and high energy consumption. Numerical simulation methods were employed to study the thermal distribution and clarify the thermal evolution law during the middle and later stages of SAGD, aiming to enhance heat utilization efficiency. Furthermore, the impacts of reservoir conditions and nitrogen injection on thermal distribution in the intermediate-to-late stages of SAGD were investigated. The research results indicate that in the intermediate-to-late stages of SAGD development, the proportion of heat loss gradually increases, while the proportion of heat absorbed by the reservoir decreases. By the later stage of SAGD, the thermal distribution is basically stable, with the reservoir absorbing only 35%-40% of the heat, the cap rock heat loss accounting for about 30%, and the heat carried by the output fluid comprising approximately 30%. Besides, an increase in permeability and reservoir thickness in reservoir conditions leads to an increase in the proportion of heat absorbed by the reservoir. Additionally, injecting nitrogen during the middle stage of SAGD can reduce heat loss in the later stage and increase the proportion of heat absorbed by the reservoir.