Oxidation Behavior of Crude Oil and SARA Fractions



Rheological and Thermochemical Research Lab is currently engaged in air injection experiments. One of the types of experiments tackles mechanisms of oxidation reactions of aliphatic and aromatic hydrocarbons. During the last several months, the Lab has managed to conduct tests of oxidation of SARA fractions (saturates, aromatics, resins, and asphaltenes). Differential scanning calorimetry, adiabatic calorimetry, and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy have been among the used methods. SAU EcoOil's research is funded by the Russian Science Foundation.

Project leader, Leading Research Associate Yuan Chengdong comments, “The comparison has shown that the oxidation behavior of crude oil and its SARA fractions is very different. We deeply analyzed the difference in oxidation behavior and tried to establish some connections between them.  For example, saturated hydrocarbons oxidize well under low temperatures. And asphaltenes, conversely, emit more heat under higher temperatures. It tells us that the oxidation behavior is directly linked to the ratio of SARA fractions in oil. Knowing this ratio, we can choose optimal ways of oil extraction.”

The results were partly covered in Oxidation Behavior of Light Crude Oil and Its SARA Fractions Characterized by TG and DSC Techniques: Differences and Connections. The next part of the research is to test light, medium and heavy oils through thermogravimetry. Here, apart from oxidation behavior, main stages and products of in-situ combustion reactions have been studied. As it appeared, light and heavy oils greatly differ during early stages of oxidation, but their kinetics become much closer during high-temperature oxidation. The findings have been submitted for publication.

“During the research, we also have a lot of problems, because it is not an easy job. You know that the composition of crude oil is very complex, and the reaction it more complicated. But we are trying to solve all the problems. We are scientists. We are born to solve problems. I hope our research will make some contributions to the successful application of air injection techniques (including high pressure air injection and in-situ combustion) in different types of reservoirs,” continues Yuan.

Another promising direction is study of oxidation of pure hydrocarbons. First takeaways are expected later this year.