Low-Temperature Oxidation Characteristics and Its Effect on the Critical Coking Temperature of Heavy Oils

Air-assisted steam stimulation (huff and puff) is an innovative process for enhanced heavy oil recovery. In this paper, the low-temperature oxidation (LTO) and coking experiments were conducted to reveal the LTO characteristics of heavy oils and its effect on the oil critical coking temperature. The O2 consuming ability and oxidation activity of different oils, in a temperature range of 80–170 °C, were analyzed, including typical light and heavy oil samples. The experimental results show that heavy oils have a higher oxidation activity at low temperature than that of light oils. Heavy oils can effectively consume O2 in the injected air and produce a certain amount of CO2 under reservoir conditions. In terms of the difference in LTO characteristics of different oils, a more general LTO reaction kinetics model of crude oils in a reservoir was established. A parameter, Rdec (ratio of hydrocarbon oxides participating in decarbonylation to total hydrocarbon oxides produced from oxidation), is introduced to ind...