Quantification of low‐temperature oxidation of light oil and its SAR fractions with TG‐DSC and TG‐FTIR analysis

Abstract

Abstract The oxidation reaction is the key to determining the success of air flooding. In this paper, experimental and theoretical techniques have been developed to identify the low‐temperature oxidation (LTO) mechanisms for light oil during air flooding by comprehensively analyzing thermal stability and oxidation process of the crude oil and its SAR (ie, saturates, aromatics, and resins) fractions. Experimentally, both a thermogravimetric analyzer coupled with differential scanning calorimetry (TG‐DSC) and a thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG‐FTIR) are employed to quantify the LTO process of crude oil and each SAR fraction as well as the corresponding oxidation properties. Theoretically, reaction models have been developed to reproduce the experimentally identified reactions. The results show that the oxygen addition reaction and the bond scission reaction occur simultaneously. The former can be initiated when temperature is higher than 50°C, and it is gradually shifted to the latter with the continuous increase in reservoir temperature. The LTO products of light oil include H2O, CO2, carboxylic acids, alcohols, phenols, and ethers. Saturates, aromatics, and resins are all the sources of H2O, CO2, alcohols, and carboxylic acids, whereas ethers are mainly derived from aromatics and resins. At the beginning of an air flooding process, heat is mainly generated from the oxidation of aromatics and resins. Subsequently, oxidizing saturates gradually dominates the air flooding process with an increase in the reservoir temperature.

Keywords

• crude oil
• LTO mechanism
• oxidation process
• SAR fraction
• thermal stability