Isolation Of Thermophilic Nitrate-reducing Bacterium And Research On Its Inhibition To Sulfate-reducing Bacteria

Sulfate-reducing bacteria (SRB) exist in most of the reservoirs in China. Their metabolism makes the formation water acidic and accelerates the corrosion rate of the pipline equipments. SRB also have a severe impact on oil production in oil field. So controlling corrosion induced by SRB attracts extensive attention in oil field nowadays.Chemical treatments to SRB are limited because of environmental stress and drug resistance of SRB. Using nitrate-reducing bacteria (NRB) to control SRB attracts extensive attention. Screening thermophilic nitrate-reducing bacterium is the key to inhibit the growth of SRB in the reservoir because the temperature of most oil reservoirs is high.This paper reports two thermophilic nitrate-reducing bacteria Njiang2 and N411 which were isolated from production water of high-tempreture oil reservoirs. These two strains have high capacity of nitrate reduction and grow very fast between 60℃ to 65℃. Njiang2 is identified to be Anoxybacillus and N411 was identified to be Geobacillus thermodenitrificons. It is believed that strain Njiang2 represents a new species of genus Anoxybacillus on the basis of phenotypic characteristics, genotypic and cellular fatty acid analysis.Focusing on the dominant SRB in high-temperature oil reservoir, Njiang2’s control effects on SRB and the change of consortia in interaction experiments were studied. Results showed that 20 mM nitrate had no inhibition on SRB. However, when Njiang2 was added to the culture system, activities of SRB disappeared completely and the inhibitory rate of H2S was 99%.Njiang2 is a thermophlic nitrate-reducing bacteria which grows under 60～65℃. It had good control effect on SRB. This paper provided technical reference for microbial inhibition that can be applied to control microbial induced corrosion in high temperature oil field.