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In the oil industry, a great deal of water is used to the process of oil exploitation in oil fields. Currently, most of Chinese oil-fields apply back-injection to the oil extraction, so not only satisfy the needs of the oil field development, but also eliminate oily wastewater efflux to environmental pollution caused by oil, but there are many hazardous microorganisms in oil-field back-injection water, mainly for sulfate-reducing bacteria, iron bacteria, saprophytic bacteria, they are easy to result in instability treated water quality, corrosion, scale and barricade to the water injection system. Therefore, work over the growth characteristics and preventive measures of the microorganisms in oil-field back-injection water are extremely important.In this paper, by making analysis on the problems existing in original treatment process, we carry on water quality analysis, corrosion and scaling products analysis judge the reasons for the instability caused water quality, and study the growth characteristics of sulfate-reducing bacteria and iron bacteria which are common and have great influence in oil-field back-injection water, destroy their growing conditions; compare with chlorine dioxide disinfection and UV disinfection, and choose the more appropriate sterilization ways, determine operating conditions. By this way, we can prevent and control the hazardous microorganisms in oil-field back-injection water.Aim at the problems existing in original treatment process, we carry on water quality analysis, corrosion and scaling products analysis, judge the reasons for the instability caused water quality. The results show that instable water quality may be due to microbiologically influenced corrosion caused by sulfate-reducing bacteria, iron bacteria, saprophytic bacteria and so on..Research the effects of pH, temperature, COD, Ca2+, Mg2+, Fe3+, Fe2+, Cl- on the growth of sulfate-reducing bacteria and iron bacteria. When pH range between 6.0～8.0, temperature between 30 40℃, Ca2+ concentration between 200～300mg/L, Fe2+ concentration increased and the existence of Mg2+ facilitate sulfate-reducing bacteria growth, but COD has no effect on sulfate-reducing bacteria growth. When pH<7, temperature between 30 35℃, COD reached 350mg/L and the existence of Ca2+ and Mg2+facilitate iron bacteria growth, but more Fe3+ goes against iron bacteria growth. When Cl- concentration between 1001500mg/L has no effect on sulfate-reducing bacteria and iron bacteria growth.The sterilization problems are analyzed based on the outstanding microorganism problems in oilfield injection water. The results show that ClO2 is suitable to apply in the oil rejection water to sterilize. Its sterilization effect is better than UV. When the dosage is between 0.5～1.0mg/L, the bacteria sterilization rates of sulfate-reducing bacteria and iron bacteria was fulfilled, when the dosage reaches 5mg/L, the sterilization rates can reach or very close to 100%. The pH value influence reaction slightly, the sterilization rates all reach above 95% when pH range is between 6～11. Though the higher the temperature, the better the effect of sterilization, but we need not improve sterilization temperature to achieve the better sterilization rates in practical application. The longer reaction time, the higher the rate of sterilization and only 10 min after the reaction, the residue of bacterial can meet the standards.Through the above means, water quality of instability and pipeline serious problems about corrosion, scaling and barricade of pipeline after treated by original process are solved. Then we can prevent and control the hazardous microorganisms in oil-field back-injection water.
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