Effect of secondary water body on the in-situ combustion behaviors

In-situ combustion (ISC) is an effective alternative method for the development of heavy oil reservoirs, especially in the later stage of steam injection and a large majority of high water-saturated channels have been formed during this phase. The water-saturated channels, also known as secondary water body (SWB), is regarded as a sensitive factor to the ISC performance. The effect of the SWB with different scales and locations was investigated by using combustion tube experiments. Results show that the existence of SWB is conducive to improving the propagation speed of combustion front combined with the reduction of combustion stability during the ISC process. As combustion front propagates to the SWB, the temperature is quickly decreased accompanied by an unstable propagation process, which inevitably induces the significant reduction of the O-2 availability and COx emission concentration. Additionally, oversized SWB would lead to a worse combustion process with much lower COx concentration and O-2 availability or even fall into an extinguishment process. Better combustion performance and oil recovery factor are obtained when SWB has large spacing to the gas injection well or exists in the lower layer. Whereas the premature O-2 breakthrough and unstable fire front propagation are generated if the SWB is close to the gas injection well or forms in the upper layer. The findings of this study are significant for better understanding the ISC performance with the consideration of SWB in heavy oil reservoirs.