Halotolerant Bacillus velezensis sustainably enhanced oil recovery of low permeability oil reservoirs by producing biosurfactant and modulating the oil microbiome

[Display omitted] •The oil recovery was increased by 21 times using B. velezensis BSA1.•B. velezensis BSA1 sustainably enhanced oil recovery of a low permeability oil reservoir.•The biosurfactant produced by B. velezensis BSA1 could maintain stable activities in harsh environments.•B. velezensis BSA1 modulated the oil microbial community structure and functions to enhance oil recovery. Low permeability oil reservoirs are widely distributed in China and rich in oil resources. Microbial enhanced oil recovery (MEOR) is a promising technology for low permeability oil reservoirs, but its application is limited by the harsh reservoir conditions. In this study, we demonstrated that halotolerant strain Bacillus velezensis BSA1 could produce biosurfactant and modulate oil microbiome for enhancing oil recovery in low permeability oil reservoirs. B. velezensis BSA1 could produce biosurfactant which comprised of surfactin and was stable in harsh environments. The MEOR column experiments showed that the oil recovered by B. velezensis BSA1 was 21.6 ± 1.87 %. We conducted successful field application in a low permeability reservoir and the cumulative oil production was more than 500 m3 with the effective period of 12 months. After monitoring of microbial community in the reservoir for a year, it showed that B. velezensis BSA1 promoted the abundance of surfactant-producing bacteria and hydrocarbon-degrading bacteria increasing. The enrichment of the functions of surfactant synthesis, hydrocarbon degradation, and methane gas production contributed to the enhancement of oil recovery. Overall, results of this study showed that using biosurfactant-producing and halotolerant B. velezensis BSA1 was a promising microbial strategy for sustainable MEOR of low permeability oil reservoir.