Low permeability reservoir, with small pore radius, narrow throat and low permeability, accounts for a high proportion in the recent years. It is hard to develop by water flooding because of the high injection pressure. And thus gas injection is an attractive process owing to its high injection ability. However, gas channeling and poor flooding efficiency frequently occur during immiscible displacement, and thus the ultimate recovery is not as high as we expected.
To find a more effective method to resolve the problems above, we initially inject high temperature mixture gas of flue gas and steam to enhance oil recovery of low permeability reservoir, which combines the advantages of nitrogen gas injection, carbon dioxide injection and steam injection. In this paper, the experiments of different injection fluids, such as water, flue gas flooding, steam and high temperature mixture gas were conducted on low permeability natural cores under reservoir conditions. And the influence factors of mixture gas injection were investigated in detail by numerical simulation method.
The results show that, comparing with water flooding and flue gas flooding, the high temperature mixture gas flooding can enhance oil recovery dramatically. It can prevent gas breakthrough early and supplement formation energy quickly. It also can reduce heat loss and increase the heat areas. The steam distillation effect is enhanced during high temperature mixture gas injection, which can reduce residual oil saturation. The more proportion of carbon dioxide in mixture gas and the higher steam dryness are, the higher oil recovery enhanced is. There are different optimal injection rates and ratios of flue gas to steam under different reservoir conditions.
The result can be used to gas injection design and has great instruction meaning for the low permeability reservoir development.