Isolation and Characterization of Viscosity-Reducing and Biosurfactant-Producing Bacteria in Low-Permeability Reservoir

Abstract

Microbialenhanced oil recovery has gained more attention in recent years due to its low cost and eco-friendliness. However, studies on the application of this technique in the low-permeability reservoirs are few. In this study, eight strains from the Ordos Basin low-permeability reservoir that produce biosurfactant and reduce viscosity were identified. Strains could produce biosurfactants (lipopeptide and glycolipids) to emulsify the oil and had good tolerance on temperature (25°C-50°C), salinity (1 g/L-50g/L), and pH (5-10). After the actions of A-3, SC4534(2), SC4561, and JSC4535, the content of long-chain n-alkanes were decreased by 51.2%, 28.3%, 35.2%, and 28.9%, respectively. The naphthalene in aromatic hydrocarbons was also effectively degraded by the strains that were screened, and the degradation rate was higher than 84%. Additionally, all strains were able to reduce oil viscosity, which was reduced by 27-51% (in seven days). 16S rRNA gene sequencing analysis indicated that seven strains belong to the genus Bacillus and one belongs to the genus Rhodospirillaceae. The results revealed that the existence of high-efficiency strains that can significantly improve the properties of crude oil in low-permeability oil fields though biodegradation and use of biosurfactants, which is of great significance for the application of MEOR in low-permeability oil fields.