Abstract: Aiming at the problems of the low heat utilization rate and slow startup of high viscosity oil in conventional fire flooding, taking the heavy oil reservoirs in Xinjiang Hongqian 1 Well Area as an example, the numerical simulation model was used to compare the oil displacement characteristics and combustion characteristics of conventional fire flooding and steam-air compound flooding, and the synergistic effects of the steam-air compound flooding was investigated and the injection parameters of the steam-air compound flooding were optimized through the analysis of the temperatures, oil saturation, and other parameters of the compound flooding in each zone. The results show that the main mechanisms to increase production and enhance efficiency are that the moist steam absorbs the heat retained in the combustion zone, becomes superheated steam, and is carried by the high-rate air across the combustion fronts so that the viscosity of the crude oil in the cold oil zone is significantly reduced, which improves the oil displacement efficiency while increasing the width, swept volume of combustion, and burning rate of the steam condensate zone; the optimization of the slug injection parameter could improve the development effect of the compound flooding, and the higher water-air ratio could make the production capacity higher; the optimal water/gas ratio should be about 3.0, and the optimal intervals between the steam injection slugs should be 90-120 d to meet the economic benefits of development because the slug injection could decrease production capacity. The research results are of great significance to improving the development effect of the fire flooding oil reservoirs.

Key words: heavy oil reservoir, fire flooding, wet combustion, combustion characteristics, oil displacement mechanism