In-reservoir treatment of high-sulfur heavy oil during steam–thermal stimulation: role of terrigenous minerals

The influence of a sodium-based nanosuspension in the presence of steam on oil transformation within a terrigenous mineral environment was examined. The results show that the sodium nanosuspension promotes hydrogenation of alkyl radicals generated during the cracking of asphaltenes and resins. A comparable reduction was observed for hydrogen sulfide, whose amount decreased from 7.0 × 10−3 g to 1.51 × 10−3 g at 15 wt.% Na. In addition, an increase in hydrogen and methane-series hydrocarbons (methane, ethane, and propane) was detected, with their concentrations rising proportionally to sodium content. It was determined that, in terrigenous reservoirs, the introduction of a 15 wt.% sodium suspension leads to an 85-fold reduction in oil viscosity. Furthermore, after steam–thermal treatment using a 15 wt.% sodium suspension, the fraction of saturated hydrocarbons increased by 32%, while the asphaltene content decreased by 40% relative to the initial oil. Compared with the control experiment, the resin content was reduced by 11%, and the asphaltene fraction decreased by 41%. Overall, the results of SARA analysis combined with viscosity measurements indicate that a sodium suspension with a concentration of 15 wt.% provides the highest efficiency for terrigenous formations.