In-situ conversion of carbon dioxide into value-added products is an essential process in terms of heavy oil upgrading and utilization of the main anthropogenic greenhouse gas. In this paper, we discuss a synthesis of sodium-coated magnetite (Fe₃O₄) particles for in-reservoir hydrogenation of CO₂. The performance of the obtained catalyst was tested in upgrading of heavy oil in a High Pressure/High Temperature (HPHT) reactor imitating the reservoir conditions during steam injection techniques. The experiments were conducted for 48 h in a CO₂ environment under the steam temperature and pressure of 250 °C and 90 bar, respectively. The results showed irreversible viscosity reduction of oil from 3931 mPa^.s to 2432 mPa^.s after the degassing of unreacted carbon dioxide. The content of resins in the composition of upgraded oil was significantly altered from 32.1 wt% to 19.01 wt%, while the content of aromatics rose from 32.5 wt% to 48.85 wt%. The GC-MS results show the presence of alkyl benzenes and phenanthrenes, which were initially concentrated in resins and asphaltenes, in the aromatics fraction of upgraded crude oil. Thus, Na-Fe₃O₄ exhibits promising results for in-situ heavy oil upgrading through the hydrogenation of carbon dioxide, which contributes not only to the reduction of greenhouse gas emissions, but also enhances heavy oil recovery.

The concentration of carbon dioxide in the atmosphere has been increasing since immediately after the boom of industrialization. Novel technologies are required for carbon dioxide (CO₂) capture, storage, and its chemical conversion into value-added products. In this study, we present a novel in situ CO₂ utilization method via a hydrogenation process in the presence of nickel tallates during steam-based enhanced oil recovery. The light n-alkanes are the preferred products of in situ catalytic hydrogenation of CO₂ due to their effective solubility, viscosity-reducing capacity, and hydrogen-donating capacity. A nickel tallate was evaluated for its carbon dioxide hydrogenation and oil-upgrading performance at 300 °C. The results showed that the content of saturated and aromatic fractions increased, while the content of heavier fragments decreased. Moreover, the relative content of normal C10–C20 alkanes doubled after the catalytic hydrogenation of CO₂. Despite the noncatalytic hydrogenation of CO₂, the viscosity was altered from 3309 mPa^.s to 1775 mPa^.s at a shear rate of 0.66 s⁻¹. The addition of the catalyst further contributed to the reduction of the viscosity, down to 1167 mPa^.s at the same shear rate. Thus, in situ catalytic hydrogenation of CO₂ not only significantly reduces the concentration of anthropogenic carbon dioxide gas in the atmosphere, but it also enhances the oil-recovery factor by improving the quality of the upgraded crude oil and its mobility.

The purpose of this study is to enhance the quality of heavy oil through refinement using aquathermolysis with the simultaneous injection of steam and thermally stable nonionic surfactants (NS). To achieve this, the NS R-PPG of the nonionic type was synthesized, and the optimal product structures were characterized using infrared (IR) methods. Furthermore, the thermal stability of the synthesized NS R-PPG was investigated in line with the requirements for surfactants used in heavy oil applications. Subsequently, the study delved into investigating the hydrothermal upgrading of heavy oil with a catalyst, involving the joint participation of steam and surfactants at a temperature of 250 °C. Additionally, we assessed the improved oil characteristics resulting from the experimental process through SARA analysis, elemental analysis, GC, and viscosity reduction evaluations. The experimental results demonstrated distinct effects concerning the presence and absence of surfactants on heavy oil. Based on these findings, we conclude that surfactants play a crucial role in dispersing asphaltene clusters, thereby facilitating the decomposition process under mild thermobaric conditions, leading to a noticeable increase in the content of light fractions. Furthermore, as per the results of the elemental analysis, surfactants contribute significantly to the desulfurization of heavy oil. Overall, the incorporation of surfactants during hydrothermal upgrading resulted in an irreversible reduction in the viscosity of heavy oil, thereby enhancing its overall quality.

The most widely applied methods to unlock heavy oil and natural bitumen resources in the world are still based on steam injection techniques. Improving the efficiency of hydrothermal processes poses a great challenge. The co-injection of various additives is practiced to lower the steam-to-oil ratio (SOR), viscosity alteration and to improve heavy oil properties. Organic solvents, non-condensable gases, air and surfactants are the preferred chemicals to be combined with steam. This study provides an investigation of the surfactant-assisted hydrothermal upgrading of heavy oil at 200 °C. The thermal stability and salt resistivity of two non-ionic surfactants (SA–3 and Biolub Green) were investigated. Moreover, the improved performance of the surfactants was established by performing an SARA analysis, elemental analysis, FT-IR spectroscopy, and EPR analysis, and by studying the viscosity reduction degree. The experimental results showed that surfactants lead to the in-depth destructive hydrogenation of the high-molecular components of heavy oil such as resins and asphaltenes. However, the content of light fractions increased. According to the results of the elemental analysis, the surfactants assist in the hydrodesulphurization of heavy oil. Overall, the physical and chemical consequences of hydrothermal upgrading in the presence of surfactants led to the irreversible viscosity reduction of heavy oil.