Enhanced Oil Recovery in a Co-Culture System of Pseudomonas aeruginosa and Bacillus subtilis

Microbial enhanced oil recovery (MEOR) is a promising technology for oil field extraction. This study investigated a co-culture system of and to increase MEOR efficacy. We analyzed bacterial growth, biosurfactant production, and crude oil emulsified performance under different inoculation ratios. Compared to single cultures, the co-culture system showed superior growth and functional expression, with an optimal inoculation ratio of 1:1. Quantitative assessments of the cell numbers and biosurfactant production during the co-culture revealed that rapid proliferation in early stages significantly stimulated growth. This interaction increased cell density and rhamnolipid production by 208.05% and 216.25%, respectively. The microscopic etching model displacement results demonstrated enhanced emulsification and mobilization of crude oil by the co-culture system, resulting in 94.48% recovery. A successful field application in a block-scale reservoir increased cumulative oil production by 3.25 × 10 t. An analysis of microbial community structure and function in different phases revealed that after co-culture system injection, became the dominant genus in the reservoir community, with an average abundance of 24.80%. Additionally, the abundance of biosurfactant-producing and hydrocarbon-degrading bacteria increased significantly. This research and the application of the and co-culture system provide novel insights and strategies for MEOR.