A total of 163 bacterial strains selectively isolated from hydrocarbon polluted sites, paraffin oils, and detergent samples, as well as some selected bacterial cultures in our Laboratory Collection were studied for their potential to use in microbial enhanced oil recovery (MEOR). After laboratory screening, 60 bacterial stains were selected for their biosurfactant activity. Their physiological and metabolic profiles and growth rates in some conditions usually found in oil fields and reservoirs revealed that 10 bacterial strains have potential for use in oil recovery. The bacteria identified were Pseudomonas aeruginosa (2), Bacillus licheniformis (2), Bacillus brevis (1), Bacillus polymyxa (1), Micrococcus varians (1), Micrococcus sp. (1) and two members of Vibrionaceae Family. Strains of B. licheniformis and B. polymyxa produced the most active surfactants which lowered the surface tension from 66 to 37 and 41 mN/m, respectively and proved to be the most anaerobic and thermotolerant selected bacteria. Micrococcus and B. brevis were the most salt-tolerant and polymer producing bacteria, respectively. Vibrionaceae family representatives and B. polymyxa strains were the most gas-producing bacteria. Oil recovery rates in laboratory column experiments using the three sets of bacteria varied from 11.2 to 18.3% (v/v) of total oil in static conditions. A mixture of B. brevis, B. licheniformis and B. polymyxa showed the best oil recovery rate.
These bacterial strains could be valuable for further application in oil recovery on producing and mature oil well sites as well as for the prevention and control of paraffin deposits in selected paraffin oil wells and reservoirs in Bahia.
Most crude oil is recovered using a pumping process. When the level of the oil drops, however, pumping becomes difficult and unproductive. In these cases secondary methods such as water flooding are used to obtain the oil. In some wells and oil fields with the use of conventional primary and secondary recovery techniques only about 8 to 30% of the total oil volume is extracted leaving vast quantities underground (Jenneman et al. 1984). Recovery also becomes more complex in oil fields producing paraffin oils because paraffin forms deposits in the pores of the reservoir and on the surfaces of the oil transport equipment, reducing yields drastically (Lazar et al. 1999). Analysis of the oil prod