Deuterium tracing used for hydrothermal conversion of high-sulfur crude

Researchers at the Institute of Geology and Petroleum Technologies conducted a comprehensive study and identified the mechanisms of chemical processes that occur when steam and a catalyst precursor are injected during the development of high-sulfur heavy-oil fields.

An urgent problem associated with developing unconventional reserves of heavy hydrocarbons with high sulfur content requires the introduction of innovative technologies that account for the specific properties of the produced raw material. In addition, its high viscosity creates numerous challenges at the stages of production, storage, and transportation. Another major challenge is the impact of sulfur-containing molecules on catalyst deactivation or poisoning, which significantly reduces the efficiency of refining processes aimed at producing marketable petroleum products.

In industry, these difficulties are mitigated by technologies based on reducing viscosity and the fraction of sulfur-containing compounds. Among them is catalytic in-reservoir hydrothermal upgrading, which is implemented directly at the production stage during thermal stimulation operations of the reservoir using steam injection.

For many years, Kazan Federal University has actively conducted research aimed at developing and studying this technology. In one of their most recent studies, supported by the Russian Science Foundation, the scientists examined the role of water in the upgrading and desulfurization of heavy oil using isotopic labels (D22O) .

Water is an environmentally friendly solvent. At the same time, it can participate in aquathermolysis reactions and reduce viscosity and sulfur content, aligning with the principles of green chemistry. The details of the study were published in the International Journal of Hydrogen Energy.

"Over the past five years, we have consistently developed a research direction focused on studying the role of water as a 'green' and environmentally safe heat carrier during steam-thermal stimulation and as a hydrogen donor during hydrothermal upgrading of high-sulfur oils, including sulfur-containing model compounds and isolated group fractions (SARA—saturates, aromatics, resins, and asphaltenes). This study became a key step forward: for the first time, using D22O, we showed that water participates in hydrogen-transfer reactions not only in liquid products but also in gaseous ones. This was confirmed by isotopic analysis of methane and hydrogen sulfide," reports the first author and researcher at the In-situ Combustion Laboratory, Ameen A. Al-Muntaser.

Experimentally, the KFU scientists once again confirmed that under hydrothermal conditions, water serves not only as a reaction medium but also as a potential hydrogen donor.

"Previously, in earlier studies together with Zarubezhneft, we already showed that under aquathermolysis conditions water has a dual function (solvent and participant in a chemical reaction). This makes it an essential agent in developing environmentally friendly and effective technologies for production and in-reservoir upgrading of heavy oils. However, the earlier work lacked molecular-level data that would make it possible to trace the entire reaction pathway, which is very important for further modeling and for assessing the applicability and effectiveness of the technology for developing specific heavy-oil reservoirs with particular compositions and properties," shares the project's scientific supervisor, Mikhail Varfolomeev.

To fill this gap, the scientists carried out studies using deuterated water, commonly known as heavy water (D22O), in combination with a selected oil-soluble organometallic precursor of an aquathermolysis catalyst: nickel(II) stearate.

"The unique combination of 22H NMR and GC–MS made it possible to directly trace the pathways of chemical reactions involving water and quantitatively evaluate the effect of temperature (200, 250, and 300 degrees). These results provide direct evidence of water's active donor function," explains researcher Muneer A. Suwaid.

The experimental work was carried out using a whole set of physicochemical methods, including FTIR spectroscopy, high-resolution deuterium (22H) NMR, and gas chromatography–mass spectrometry. Isotopic analysis of both liquid and gaseous products revealed temperature-dependent behavior (200, 250, and 300 degrees), providing a fundamental basis for understanding the role of water as a hydrogen donor and its interaction with catalytic systems.

The results not only enrich the theoretical foundation of hydrothermal upgrading and clarify hydrogen-transfer pathways, but also serve as a strong argument for optimizing upgrading and desulfurization technologies. In addition, the study opens new opportunities for assessing the role of water as an environmentally friendly agent for thermal and thermocatalytic treatment of high-sulfur crude.

More information:
Hydrothermal system for high-sulfur real fuel conversion and desulfurization: Deuterium -traced evaluation of temperature-driven hydrogen transfer
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Provided by Kazan Federal University