Low temperature oxidation process of heavy oil in Fengcheng Oilfield, Karamay

The resin content of heavy oil in Fengcheng Oilfield is high. And as the exploitation of heavy oil in this area goes further, some oil wells present the problems of poor stimulation effect and high water cut. In order to improve the safety of air injection for oil recovery in heavy oil reservoirs in Fengcheng Oilfield Karamay, low temperature oxidation experiment was carried out. In the experiment, the low temperature oxidation situations of oil samples in different temperatures (80-250 ℃) were investigated under the simulated pressure (8 MPa) of heavy oil reservoirs in Fengcheng Block of Karamay. The physical property change, compositional change and gas change of oil samples in the initial low temperature oxidation stage of in-situ combustion were studied. It is indicated that due to the low temperature oxidation reaction, the density of heavy oil is increased by 2% and its viscosity is increased by 0.72 times. IR analysis results show that the low temperature oxidation reaction between heavy oil and air increases the absorption intensity of oxygenated functional group (—C=O and aliphatic ether) significantly. The activity of SARA compositions is ranked as aromatic>saturate>resin. After reaction at 250 ℃, the asphaltene content increases more. N₂ content of the air is basically unchanged, O₂ content decreases from 21% to 5%, and the content of CO, CH₄ and CO₂ increases. The calculation results by bond energy method shows that the average thermal discharge corresponding to the O₂ consumption of 1 moL is 391.54-420.58 kJ. The research results provide the basic data for field experiment design and field application.