Alternative stable microbiome state triggered by the introduction of functional microbes in oil reservoirs drives sustainable microbial enhanced oil recovery

•The oil production increment is closely related to the reservoir microbiota status.•The oil production increases by more than 50% in alternative stable state.•Interactions among Dietzia, Bacillus and Halomonas play an important role in the shift of microbiota status.•Sufficient introduction of functional microbes can improve microbiota status to achieve sustainable oil increment.