Crude Oil Oxidation in an Air Injection Based Enhanced Oil Recovery Process: Chemical Reaction Mechanism and Catalysis

Air injection as a thermal method for heavy oil recovery has a long history of about a century. However, it has not been widely applied in oilfields to date because of many challenges caused by its technical complexity. In the last two decades, more and more attention has been paid to the air injection technique because of the increasing demand for the effective development of hard-to-recover resources, including heavy oil, bitumen, oil shale, water-flooded mature reservoirs, etc. in a more energy-saving, cost-effective, environmentally friendly way. Consequently, many considerable improvements in both theory and technology have been made recently. This work first reviews the recent advances in the reaction mechanism of crude oil oxidation with highlights on the difference and connection between the oxidation of different oil components as well as their interaction during cocombustion; then, it discusses the catalytic methods for intensifying crude oil combustion with different types of catalysts, including nanometal-based particles, water-soluble metallic salts, and oil-dispersed metal-based catalysts. On the basis of the detailed review and discussion, we shed light on the challenges facing the air injection process and put forward possible methods to solve them. Simultaneously, we point out the neglected aspects of the air injection process and open the way toward fresh thinking for its technical application. And finally, we propose promising perspectives for future work for improving the performance of air injection and its wide application.