A novel equation for the air injection and oil production during fire-flooding process based on experimental study in developing heavy oil reservoir

Fire flooding (FF) has been one of the important thermal enhanced-oil-recovery technologies in developing heavy oil reservoir. Many scholars have carried out laboratory studies on the complex oil-displacement mechanism due to the complex physical and chemical reactions for fire flooding. However, almost no one had given an equation expression of gas injection and production during fire-flooding process. Therefore, the FF and flue gas flooding (FGF) experiments of one-dimensional combustion tubes were conducted. The oil-recovery differences of FF and FGF experiments under the same conditions were calculated, and a high linear correlation was found. The results showed that the FF effects were mainly affected by the flue-gas when the gas injection was low, and the combustion-front expansion (CFE) effects made the main contribution when the gas injection was high. The gas injection, water and liquid production were logarithmically treated and compared with the oil production. It was found a strong linear relationship between the two sets of experiments, and the linear relationship was stronger in the FGF experiment. Among all the linear relationships, the logarithm of water production and oil production had the strongest linear relationship. Based on this understanding, the water and oil production were connected from flue gas in FF process, and a novel FF equation was derived and obtained. Finally, the production curves on site of the two typical FF cases and the fitting curves of the FF equation were descripted and compared. The results showed that the novel equation can reflect and forecast the field performance by FF process in developing heavy oil reservoir.