Abstract: In order to improve the biochemical treating effect of oilfield produced water, three bacteria strains, JQ-1, JQ-2, JQ-3, are isolated from produced fluids in Shengli oilfield, Which oil degrading rate are up to 48%, 55% and 46% respectively. Strains JQ-1, JQ-2 are identified as Bacillus sp, JQ-3 as Acinetobacter sp. Comparing with single bacterium, mixed three bacteria strains have better degradation ability, whose degrading rate of crude oil is up to 70%, the best degradation conditions of mixed bacteria are: temperature 45~55℃, pH6.5~7.0, mineralized rate 12000~18000mg/L. The bench scale laboratory biochemical test simulating field conditions show that after 8 hours, the oil content of oilfield produced water is reduced from 40mg/L average to less than 2mg/L, at the same time, sulfate reducing bacteria (SRB) is restrained effectively. Continuous biochemical treatment with hydrocarbon degradation bacteria is improved.

Key words: hydrocarbon degradation bacteria, hightemperature, screening, reinjected produced water, biochemical treatment, ShengLi oilfield