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

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• 作者：Liang Zhang ; Junyu Deng ; Lei Wang ; Zhenya Chen ; Shaoran Ren ; Changhao Hu ; Shoujun Zhang
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：February 19, 2015
• 年：2015
• 卷：29
• 期：2
• 页码：538-545
• 全文大小：393K
• ISSN：1520-5029

文摘

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鈥?70 掳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, R_dec (ratio of hydrocarbon oxides participating in decarbonylation to total hydrocarbon oxides produced from oxidation), is introduced to indicate the O₂鈥揅O₂ conversion features of different oils during the LTO process. The R_dec, E_a, and k_o of heavy oils are usually lower than those of light oils, which can well reflect the LTO characteristics of heavy oils and demonstrate that heavy oils are more easily oxidized at a low temperature. However, because of more heavy oil components generated during the LTO process, the critical coking temperature of heavy oils exposed to an air environment will decrease (by 120 掳C from 400 to 280 掳C for super heavy oil). It should be noted that the effect of the LTO process on the critical coking temperature is different for different heavy oils, and the induced coking risks are also different in different heavy oil reservoirs, which need further studies in the laboratory and field.