Roles of Flue Gas in Promoting Steam Flow and Heat Transfer in Multithermal Fluid Flooding

Multithermal fluid technology is becoming an important method in the field of heavy oil development. However, because of insufficient investigation on the heat transfer for the multithermal fluid, some development phenomena and characteristics still cannot be well explained. In order to determine the effect of flue gas on the thermal swept scope, multithermal fluid flooding experiments were carried out through 1D sandpack. The temperatures along the sandpack were measured. On this basis, steam heat transfer simulation experiments were conducted and the heat transfer coefficients were calculated. The mechanism of flue gas on steam heat transfer was analyzed. The results show that at the same heat injection conditions, the thermal swept scope for the multithermal fluid flooding was larger than that for the steam flooding. With the increase of flue gas proportion in the multithermal fluid, the heat transfer coefficient decreased and the condensation pattern was transformed from drop condensation to film condensation gradually. The flue gas can form gas film on the surface of the cold body and inhibit the heat transfer between steam and the cold body. Because of the inhibiting effect of flue gas on steam heat transfer, flue gas can reduce the heat transferred to the rock matrix in flooding and thus promote steam to carry more heat further. Meanwhile, flue gas can accelerate the flow of steam in porous media, which also leads to the expansion of the thermal swept scope for the multithermal fluid flooding.