Oxidation behavior and kinetics of shale oil under different oxygen concentrations

Abstract

The oxidation behavior and kinetics of crude oil within tight shale differ from those of traditional light and heavy oils. In this study, the static oxidation tests on tight shale samples were conducted under different oxygen concentrations (11%, 16%, 21%, and 26%), followed by analysis of effluent gas and oxidized oil. Specifically, the compositional changes in shale oil at the molecular level were studied. Additionally, the self-ignition potential of shale oil under different oxygen concentrations was evaluated using accelerating rate calorimetry, and the corresponding kinetic parameters were determined. The results indicated that as the oxygen concentration increased from 16% to 26%, the relative abundance of O1 species decreased from 10.96% to 8.66%, whereas that of O3 species increased from 6.16% to 8.46%. Also, the relative abundance of chain saturated aliphatic acids and tricyclic naphthenic acids was observed to decrease and increase, respectively, in the shale oil oxidized at 26% oxygen concentration compared to the other shale oils oxidized at oxygen concentration lower than 26%. The shale oil displayed significant oxidation activity under different oxygen concentrations (16%, 21%, and 26%), and an increased oxygen partial pressure resulted in a shorter induction period of oxidation and higher combustion intensity. The kinetics results showed that the combustion activity of coke was enhanced while increasing oxygen concentration from 16% to 26%. The shale oil encountered fewer concentration-dependent oxidation reactions under higher oxygen concentration. Overall, this study provides valuable insights into the oxidation behavior of crude oil within tight shale.