Research Team of Nankai University Makes Progress in the Field of Microbial EOR of Heavy oil

New research progress on heavy oil recovery and heterocycles biodegradation, made by the team of Prof. Wenjie Xia and Prof. Ting Ma of Nankai University, was well-documented in paper titled “N,S-Heterocycles biodegradation and biosurfactant production under CO2/N2 conditions by Pseudomonas and its application on heavy oil recovery”, has been published on Chemical Engineering Journal on February 10, 2021.

Link to the paper: https://doi.org/10.1016/j.cej.2021.128771

Heavy oil resources accounts for two thirds of all world oil reserves, however until now only one percent is being efficiently exploited with using thermal techniques. Generally, ultra-heavy oil, as one of unconventional fossil resources, cannot be developed by the conventional EOR techniques due to its well-known properties of the high viscosity and density, poor fluidity, and easy absorption. The extra-high viscosity is the significant obstacle for the recovery of this resource. Polar components, like asphaltene and resin that generally account for more than 45%, play the critical roles in the viscosity of the ultraheavy oil. Impressively, the richness of the heterogenous elements (such as nitrogen and sulfur) in these polar components is significantly characterized beyond the saturated and aromatic hydrocarbons. Therefore, the cleavage of HPAs via microorganisms could be significant strategy of viscosity reduction.

Here, we reported a microbial strategy with using the heterocycles-degrading and biosurfactant-producing Pseudomonas strain for heavy oil recovery without thermal energy input. To validate it, we initiated the bacterial evaluation of anaerobically heterocycles degradation and biosurfactant production under CO₂ and N₂ conditions. Results demonstrated that the CO₂ can significantly facilitate the anerobic degradation and influence the yield and diversity of biosurfactant. Structural identification of the biosurfactants by HPLC-MS showed that the di-rhamnolipids and lipopeptides (iturin and fengycin) were respectively accounted for more than 80% and 60% under CO2 condition when fed with carbazole and dibenzothiophene. Degradation of heavy oil under CO2 condition made the better performance on the oil viscosity reducing, the surface tension reducing, emulsification, and oil degrading rate than that under N2 condition. Huff-puff field trials in Jilin oilfield successfully demonstrated that the cumulative oil production was increased from 48 tons to 566 tons with the effective period of more than 9 months, and the viscosity of the produced oil was significantly decreased by 50–65%. These results suggested that this green strategy was promising and economical to the oil recovery for the ultra-heavy reservoir where is easily accessible to CO₂.