Microbial Enhanced Oil Recovery, Wettability Alteration and Interfacial Tension Reduction by an Efficient Bacterial Consortium, ERCPPI-2

In the present study, the potential of a bacterial consortium of Enterobacter cloacae and Pseudomonas sp. (ERCPPI-2) for microbial enhanced oil recovery was investigated. Various mechanisms of enhanced oil recovery (EOR) as a result of using ERCPPI-2 and its metabolic products were studied in detail. The obtained results showed that under simulated reservoir conditions, interfacial tension reduction (IFT), gas production and wettability alteration were the main mechanisms for more oil recovery from the water-flooded cores. It was also found that biosurfactant production had a substantial effect on the reduction of oil/water interfacial tension and recovering the trapped oil.  The experimental data acquired from the designed core holder flooding system demonstrated that in situ bacterial growth altered the wettability of cores towards more water-wet conditions while the cell-free biosurfactant injection reversed it into more oil-wet conditions. Due to the effect of multiple microbial mechanisms exerted by ERCPPI-2, bacterial injection was able to reduce the residual oil saturation below 3%, in spite of its amount at the beginning of microbial process. In more severe conditions of a salinity of 5% (w/v) and temperature of 60 °C, the oil recovery efficiency reached 24.1 and 39.1%, respectively.