The effect of low-temperature oxidation in air-assisted steam flooding process for enhancing oil recovery

Air-assisted steam flooding is a new promoting technique for enhanced oil recovery compared to the other traditional thermal recovery methods. In this study, five experiments, including one steam flooding experiment, three combined steam–air flooding experiments, and one combined steam–N₂ flooding experiment were studied, under the conditions of 180 °C and back-pressure valve of 8 MPa, with sand-packed model. The volume fraction of mixed gas in these four combined steam–air (or N₂) flooding experiments were 80% steam+20% air, 60% steam+40% air, 40% steam+60% air, and 60% steam+40% N₂, respectively. The experimental results showed that air-assisted steam flooding could enhance the oil displacement efficiency when the volume fraction of air and steam was in a certain number, and the optimal condition is 60% steam+40% air. Furthermore, water cut curves and saturate, aromatic, resin, and asphaltene (SARA) analysis results also demonstrate that the low-temperature oxidation reaction in air-assisted steam flooding process advantageous to profile control of generating high viscosity “PLUG” to seal high-permeability channel in reservoir.