Influence of low temperature oxidation on heavy oil coking by thermal pyrolysis during in situ combustion process

Coke is the primary fuel for in situ combustion(ISC), so the coking characteristics of heavy oil play a vital role in this process. There is an apparent low temperature oxidation zone in the ISC process. After low temperature oxidation, the pyrolysis coking characteristic of heavy oil will change significantly. In this paper, the low temperature oxidation for heavy oil was carried out, and then the pyrolysis coking experiments of crude oil and oxidized heavy oil were studied under different field temperature conditions. Then the coke yield, composition, and surface microstructure of pyrolyzed coke were investigated. The coke's oxidation activity and heat value were measured, and the kinetic parameters were calculated. The results showed that the oxygen proportion and the asphaltene content of heavy oil increased after low temperature oxidation. The pyrolysis coking characteristics of oxidized heavy oil were different from that of crude oil. The oxidized heavy oil showed a higher coke yield than crude oil. The oxygen proportion of the coke from oxidized heavy oil was similar to that of the coke from crude oil, but it had a lower hydrogen/carbon ratio. The prominent infrared absorption peaks of both cokes were from aromatic hydrocarbon. The oxidation activity and heat value of the coke from oxidized heavy oil were lower than that from crude oil. Kinetic analysis showed that both cokes had similar activation energies. The loose and porous structure of coke from crude oil resulted in higher oxidation activity.

Automated summary

The coking characteristics of heavy oil play a crucial role in the in situ combustion process. After low temperature oxidation, the pyrolysis coking characteristics of heavy oil change significantly, resulting in a higher coke yield but lower oxidation activity and heat value.