PORE- AND CORE-SCALE RECOVERY PERFORMANCE OF CONSORTIUM BACTERIA FROM LOW-PERMEABILITY RESERVOIR

Microbial Enhanced Oil Recovery (MEOR) is a promising tertiary oil recovery technology based on the survival and metabolism of petroleum microorganisms in the reservoir to modify the reservoir and crude oil to enhance oil recovery. The ultimate goal of MEOR is field application. Evaluation experiments in the laboratory are not sufficient to fully simulate the actual conditions, and field tests are difficult to conduct at any time due to economic and other constraints. Therefore, conducting simulated flooding of real cores is an important way to verify the indoor results and a precursor before field experiments. In this study, a micro-visualization model (glass etching model) and the real tight cores (The average permeability of the core is 0.01mD) were chosen to investigate the actual recovery efficiency and the mechanism of the consortium bacteria B-ALL. The bacterial consortium was constructed by three single strains, SC4534 (2) (Bacillus sp.), SC4542 (Bacillus licheniformis), and A-3 (Bacillus licheniformis), isolated from low-permeability reservoir in the Ordos Basin, China, in a 1:1:1 ratio. B-ALL has the best emulsification and degradation ability, with a further 23.81% reduction in degradation rate compared to the single bacteria. It was found that the recovery efficiency was positively correlated with the microbial injection volume as well as the incubation time. For the microscopic model with high pores and high permeability, the efficiency of secondary water flooding can be increased by 44.77% after six days of incubation with two pore-volume microbes. While for the real tight cores, the maximum secondary water flooding efficiency after six days of incubation with one pore-volume microbes was 6.98%. The visualization experimental results indicated that the microorganisms mainly increase oil washing efficiency through emulsification and changing the wettability. In addition, the generated oil droplets will play a role in plugging and improve the wave efficiency. However, for tight reservoirs, due to the poor connectivity, the microbial recovery efficiency was lower under shorter cultivation times (3 days). The extension of incubation time could lead to a rapid increase in recovery efficiency (from 2.69% to 6.98%). This study validates the role of consortium bacteria in enhancing recovery and provides a basis for the application of MEOR in real oil fields.