Technogenic impact on reservoir oil, which consists in the use of enhanced oil recovery (EOR) methods could result in an interaction between reservoir fluids and injected liquids. The effect of oil-displacing and sol-forming EOR systems on the composition, properties, and stability of extracted oil is investigated in the case of heavy bituminous oil from the Usinskoye oil field. The results of investigation of the group chemical composition of oil samples are presented. It has been found out that the systems have different effects on the chemical composition of the oil. A change in the composition during the extraction with time has been established, which becomes the most noticeable after 1.5-2 months after the injection of oil-displacing systems. In this case, an increase in the content of oil components by 3-5%, a decrease in resin-asphaltene substances, and changes in the ratio of resins to asphaltenes are observed. The oil stability largely depends on changes in its composition, pressure and temperature. The oil stability was estimated via spectrophotometry. The results of the determination of various spectral characteristics of oil in the visible region via electron spectroscopy are presented. It has been found out that the aggregate stability of oil is significantly affected by aromatic and saturated hydrocarbons, and heavy high-molecular components (asphaltenes and resins). The relationship between the content of resin-asphaltene substances and oil stability is shown. The effect of oil-displacing and sol-forming compositions on the stability of oil to asphaltene precipitation is studied. The most effect on the stability of oil has been provided by oil-displacing systems containing surfactants. Control of changes in the composition and properties of the extracted oil allowed us to explain the mechanism of action of new technologies in a heterogeneous carbonate reservoir.
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