Abstract: To further clarify the performance of reaction kinetic and the variety pattern of oil components in the process of in-situ combustion, the heavy oil of well Hongqian-1 (Xinjiang) was divided into pseudo-components with different boiling ranges by the method of true boiling point (TBP).The effect of system pressure on the oxidation performance of pseudo-components with boiling range higher than 350 ℃ was studied. The combustion pool was tested with linear temperature program to study the variety pattern of system pressure on the gas volume fraction, temperature and thermal intensity while the pseudo-components of heavy oil reacted with injected air.The results show that the system pressure has significant effects on the oxygenation reaction and decarboxylation during the low-temperature oxidation stage, and the effect on the pseudo-components of low boiling range is further pronounced.The CO and CO₂ production of the pseudo-components with a boiling range of 350 ℃ to 420 ℃ at a system pressure of 3.0 MPa is 10 times higher than its production at 1.0 MPa. Although the pseudo-components with high boiling range are less affected by the system pressure, the thermal intensity of the pseudo-components with a boiling range greater than 500 ℃ can be as high as 12.26 kJ/g;the upgrading of heavy oil in the process of in-situ combustion depends on the consumption of heavy components and pyrolysis reactions.The research results provide reference for the analysis of components loss and reasonable analysis and prediction of reservoir temperature in the process of in-situ combustion.

Key words: in-situ combustion, heavy oil, combustion pool, low temperature oxidation, pseudo-components, system pressure