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Solvent Assisted-Steam Assisted Gravity Drainage (SA-SAGD) process is an enhancement to SAGD recovery technology. In this process a hydrocarbon solvent is injected simultaneously with steam to accelerate the oil production rate and reduce steam-to-oil ratio (SOR) compared to classical SAGD. SA-SAGD is a complex process; its physics and mechanisms are not fully understood. ExxonMobil and its affiliate Imperial Oil have been investigating SA-SAGD through an integrated research program that includes fundamental laboratory work, advanced numerical simulation studies, laboratory scaled physical modeling, and field piloting. This research program aims at in-depth understanding of process physics and mechanisms, evaluating process performance and behavior, and improving SA-SAGD recovery technology. This paper focuses on SA-SAGD optimization and assessing the effects of operating conditions and solvent choice on the process performance. The complex solvent-steam phase behavior and their interaction under reservoir operating conditions are investigated in the current work. Phase behavior analysis shows that the solvent boiling range affects solvent-steam condensation temperature at the condensation and mixing front and consequently it affects the solvent effectiveness in terms of performance enhancement. The effect of phase behavior on SA-SAGD performance has been evaluated by analyzing experimental and simulation performance data. It is shown that the composition of injected fluid significantly affects the process performance. It is also shown that the solvent composition can be customized to improve SA-SAGD process performance under different operating conditions. |
