Investigation of EOR mechanism for flue gas assisted SAGD

Abstract

As a promising technique, flue gas assisted SAGD can not only reduce greenhouse gas emission but also increase economic benefits. However, the role that flue gas plays in flue gas assisted SAGD is still not very clear. Here, 2D visualization SAGD and condensation heat transfer (CHT) experiment were conducted, where temperature profiles can be measured and steam chamber can be observed simultaneously, to study systematically the effect of flue gas on SAGD performance and the EOR mechanisms of flue gas assisted SAGD. The experimental results showed the steam chamber development of flue gas assisted SAGD went through three stages: early fast growth stage, secondary upward growth stage, and slow lateral expansion stage. The injection of flue gas prolonged the high production period and increased the oil recovery by 23%. Flue gas can decrease the CHT coefficient and transform the condensation pattern from “drop condensation” to “film condensation”, which was the dominant mechanism to improve SAGD performance and the reason of the formation for secondary upward growth stage of steam chamber. Moreover, CHT coefficient decreased as flue gas water ratio increased. Besides, gas cap assisted residual oil downward and lateral expansion, as well as steam flow resistance reduction owing to gas fingering were two other crucial aspects improving SAGD performance.