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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.

In this study, for the first time we investigated the in situ upgrading performance of Na metal nanoparticles, which were obtained by dispersing small pieces of sodium in liquid paraffin up to certain dispersity. In situ aquathermolytic reactions were modeled in a high pressure–high temperature reactor coupled with a Gas Chromatography (GC) system at a temperature of 250 °C for 24 h using a heavy oil sample, produced from the Ashal’cha reservoir, Republic of Tatarstan (Russia). The mean particle size of Na nanoparticles was 6.5 nm determined by the Dynamic Light Scattering (DLS) method. The nanoparticles were introduced to the reaction medium with a concentration of 2 wt.% The upgrading performance of Na nanoparticles was evaluated by several analytical methods such as Gas Chromatography (GC), elemental analysis (CHNS), SARA, Gas Chromatography–Mass Spectroscopy (GC-MS), FT-IR spectroscopy and viscosity measurements. It was revealed that Na nanoparticles interact with water to yield hydrogen gas, the concentration of which increases from 0.015 to 0.805 wt.% Moreover, the viscosity of upgraded heavy oil was reduced by more than 50% and the content of low-molecular-weight hydrocarbons in saturated and aromatics fractions was increased. The Na nanoparticles contributed to the utilization of hydrogen sulfide and carbon dioxide by 99 and 94 wt.%, respectively.

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Catalytic thermolysis is considered to be an effective process for viscosity reduction, the conversion of high-molecular components of oil (resins and asphaltenes) into light hydrocarbons, and the desulfurization of hydrocarbons. In this paper, we conducted non-catalytic and catalytic thermolysis of a heavy oil sample isolated from the Ashalcha oil field (Tatarstan, Russia) at a temperature of 250 °C. Fullerene C60 nanoparticles were applied to promote selective low-temperature thermolytic reactions in the heavy oil, which increase the depth of heavy oil upgrading and enhance the flow behavior of viscous crude oil. In addition, the influence of water content on the performance of heavy oil thermolysis was evaluated. It was found that water contributes to the cracking of high-molecular components such as resins and asphaltenes. The destruction products lead to the improvement of group and fractional components of crude oil. The results of the experiments showed that the content of asphaltenes after the aquatic thermolysis of the heavy oil sample in the presence of fullerene C60 was reduced by 35% in contrast to the initial crude oil sample. The destructive hydrogenation processes resulted in the irreversible viscosity reduction of the heavy oil sample from 3110 mPa.s to 2081 mPa.s measured at a temperature of 20 °C. Thus, the feasibility of using fullerene C60 as an additive in order to increase the yield of light fractions and reduce viscosity is confirmed.