N,S-Heterocycles biodegradation and biosurfactantproduction under CO2/ N2 conditions by Pseudomonas and its application on heavy oil recovery

Great challenge of the ultra-heavy oil recovery via cold approaches is attracting the increasing worldwide efforts. 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.