Construction and Performance Evaluation of Dual-Metabolite Oil-Producing Engineering Bacteria Suitable for Low-Permeability Reservoir

AbstractMicrobial oil recovery (MEOR) technology has a wide application prospect in the field of enhanced oil recovery in low-permeability reservoirs, and genetic engineering plays an important role. At present, oil-production engineering bacteria constructed by genetic engineering are mainly used to obtain high metabolites and strong environmental adaptability; there are few reports on genetically engineered bacteria with different functional metabolites. However, the bacteria which could efficiently produce one metabolite have a poor ability to produce other metabolites. Therefore, in order to reduce the cost of nutrients and improve the effect of microbial oil recovery, dual-metabolite bacteria have been constructed for low-permeability reservoir. In this paper, four rhamnolipid expression plasmids are extracted from E. coli-produced biosurfactant. Then, the rhamnolipid expression plasmids are transferred into the bacteria-produced biopolymer by electrotransformation, and the metabolite performance of the constructed bacteria is evaluated. Finally, the profile control and displacement performance of the constructed bacteria are studied through low-permeability core experiments. The experimental results show that three bacteria, WS1, WS2, and WS3, are successfully constructed that have preferable ability, among which the bacteria WS2 has the best capacity for producing biopolymer and biosurfactant at the same time. After culturing 96 h, the viscosity of the bacteria WS2 fermentation broth could increase to 42.1 mPa·s, and the surface tension and interfacial tension of the fermentation broth could decrease to 24.3 mN/m and 0.035 mN/m, respectively. This time-varying biological viscosity ensures that the microbial system can enter the low-permeability reservoir at a low injection pressure, and the oil recovery of the low-permeability core could be increased by 10.18% after injecting 0.5 PV WS2 microbial system. The findings of this study can help for better understanding of gene construction and technical support for further popularization and application of MEOR in low-permeability reservoirs.