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October 13 | Science and Technology Ivan Okhapkin

Russian scientists are one step closer to deciphering the structure of oil

Kazan scientists have proved the link between free radicals and vanadyl porphyrin complexes in asphaltenes.

It’s not a secret that the main structure-forming units of heavy oil and bitumen are high molecular weight components such as asphaltenes, resins and polycyclic aromatic hydrocarbons. One can say the same on presence of unpaired electrons, which are concentrated mainly in the vanadyl porphyrin complexes (VPC), and "free" hydrocarbon radicals. By studying the behavior of these electrons, it’s possible to make conclusions on the structure and properties of oil and observe its changes in the course of production or processing.

КФУ

There are several technologies, including those based on the method of electron paramagnetic resonance (EPR), opened in 1944 at the Kazan Federal University (KFU) by E.K. Zavoiskii. EPR is widely known in material science and even biomedical research, but rather unconventional for petrophysics. However, this area of research received a boost, thanks to the efforts of the research group of the Department of quantum electronics and radiospectroscopy of the Institute of Physics KFU.

"Study of vanadyls and porphyrins is an inexhaustible field of research that began back in the 30s of the last century. It would seem that everything has already been known and calculated. However, our main feature is that we do not work with model systems, especially not with the extracted fractions (although with them too, for comparison of experimental results), but with real samples of oil, without any additional processing. According to it, we pursue several goals.

Firstly, we approach to the use of the EPR method for rapid analysis of hydrocarbons. Unfortunately, despite the proven capabilities of the method of EPR and a huge number of patents in this field, we almost do not see the use of EPR in exploration, oil and gas production.

In my opinion, this is due to the lack of compact equipment, standardized procedures, low-skilled personnel. And secondly, we demonstrate completely new possibilities of modern EPR techniques for the characterization of hydrocarbon materials,"- Sergei Orlinskii, the assistant professor of the Department of quantum electronics and radiospectroscopy of the Institute of Physics KFU, said.

КФУ

The glorious traditions of the founders of paramagnetic resonance and the influx of innovations played significant role. Today the EPR laboratory of KFU is one of the best in the world, both in equipment and qualification of scientists working in it. For instance, Sergei Orlinskii (his personal h-index is 17) is a leading reviewer of physical, chemical and physical journals such as the Physical Review and the Journal of Physical Chemistry for many years. Since 2014, EPR laboratory staff, consisting of only physicists, almost every month gets articles for review from specialized international magazines, devoted to oil production, petrochemical technology, study of the properties of polymers and hydrocarbon fractions, oily rocks etc.

We should also note that in September this year, the EPR group has published a third article in the Journal of the American Chemical Society – The Energy and Fuels. It’s the world's leading edition in the field of oil and fuel energy. In this article scientists of KFU published the results of the latest research on solving one of the main hypotheses about the form of existence of vanadyl porphyrin complexes in asphaltene aggregates.

In particular, if the VPC are part of asphaltenes molecules or common aggregates formed by intermolecular interaction? This question with its purely fundamental character has paramount importance to practitioners, revealing the way of control processes of reduction of viscosity and the development of new schemes of removing the metal complexes from a hydrocarbon feedstock.

"Today EPR tomography of living organisms is developing rapidly. We want to do the same, only for full-size cores. The idea is that eventually we will get a comparatively small device (EPR tomograph), in which we will be able to load the core and find water and oil saturated area in it, as well as the availability, distribution and concentration of metal complexes, salts, etc.

Specially trained employee of the company will be able to do it. Being a scientist isn’t necessary, because the whole algorithm will be ready-to-use. But it’s in the long run. Now we want to understand what is high viscosity oil, what it does consist of and how it differs from other oil kinds.

After all, the term "oil" hides completely different systems. For instance, high-viscosity oil in terms of EPR spectra and EPR characteristics of the deposit of Tatarstan is not like the other extracted from the same mine, but from a different depth, and the neighboring Bashkir oil has nothing in common with it, except the name. We are looking for this difference. Because, knowing the composition and the structure of the oil, we will know how to optimize the production and mining. In a way, our research is the future of oil production", - Marat Gafurov, senior researcher of SRL of magnetic radiospectroscopy and quantum electronics named after S.A. Altshuler, shared plans of his scientific group.

In the article, published in September issue of the Energy and Fuels journal, physicists of KFU kicked the traditional idea of the structure of asphaltenes. The presented results have caused the reviewers (and there were a lot of them- 5) a great number of questions, to each of them our scientists gave a detailed answer. Thus, the article, submitted to the journal in April, eventually was published only  5 months later.

"First it was thought that free radicals and vanadyl ions were living "separate lives". Nothing like this! We have shown that they are very closely related. When heating oil or fractionation it comes to the fact that the structure of "free" radicals is even changing, but their relationship with vanadyl remains. Just because this relationship does not break, "- Marat Gafurov explained.

In EPR spectroscopy laboratory people honestly say - their current openings, with high probability, will not reach the practitioners, because these are basic studies. What they are doing now in the heavy oil is a small revolution. But after the accumulation of a critical mass of new knowledge all this will be certainly of use.

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