Experimental Study of Oxygen-Rich in Situ Combustion for Heavy Oil Recovery

Abstract

The in-situ combustion method is the commonly used method for heavy oil production with high recovery rate and low cost. However, the characteristics of the oil oxidation reaction during in-situ combustion are still not clearly understood so far. In this study, the thermal oxidation experiment was carried out for the in-situ combustion process based on the heavy oil from Du 66 block. The results show that: the fired oil zone can be divided into the combustion zone, the coking zone, the condensation zone, the movable oil zone, etc. When the combustion front is formed, the CO2 and CO contents rise to 10% and 20%, respectively. In the expansion phase of the combustion front, the oxygen utilization rate is 83.93%, and the H/C atomic ratio is 1.413, indicating that the high temperature oxidation reaction plays the leading role. Sustained gas injection with enough intensity can ensure that the combustion front moves forward continuously, and the combustion front can drive the crude oil forward in the form of snowballing due to the extremely high oil displacement efficiency. The pressure increases as the combustion front and the movable oil zone advance, but the movable oil zone begins to decrease as it advances to the production well. Through this study, it is concluded that effective combustion front and movement of combustion front are the foundation for the formation of movable oil zone. And the movable oil zone pressurization is an important mechanism for in-situ combustion. The findings of this study can help for better understanding of the in-situ combustion oxidation mechanism and can improve the production design for heavy oil reservoirs.