渤海油田注水井下环境复杂,管柱多次发生穿孔,套管腐蚀严重。在渤海某油田实际注水井取水样,分析其水质和细菌类型,并以现场水样为腐蚀介质进行模拟试验,开展了注水井水样中的微生物腐蚀性评价,对比分析了加入杀菌剂或缓蚀剂前后N80钢、3Cr钢和13Cr钢等在对应环境中的腐蚀速率,并建立了长期腐蚀速率预测模型。结果表明:微生物腐蚀是造成渤海油田注水井管柱腐蚀的主要原因,注入水中的细菌以硫酸盐还原菌(SRB)和铁氧化细菌(IOB)为主,杀菌剂可有效降低油套管的腐蚀速率;N80钢和3Cr钢在微生物环境中的均匀腐蚀速率分别为0.58 mm·a^-1和0.27 mm·a^-1,加入杀菌剂后的均匀腐蚀速率分别为0.18 mm·a^-1和0.13 mm·a^-1,N80钢在不加杀菌剂的环境中无法满足生产要求;低浓度杀菌剂对注水井油套管的微生物腐蚀具有明显的抑制作用,选用3Cr材质并加入低浓度杀菌剂能够满足注水井的防腐蚀要求。

The downhole environment of water injection wells in Bohai oilfield is complex, and the string perforation and casing corrosion are serious. The water samples were taken from the actual water injection wells in an oilfield in Bohai, and the water quality and bacterial types were analyzed. The field water samples were used as corrosive media to carry out the simulation test. The microbial corrosion evaluation in the water injection wells was carried out. The corrosion rates of N80 steel, 3Cr steel and 13Cr steel in the corresponding environment before and after adding fungicides or corrosion inhibitors were compared and analyzed, and the long-term corrosion rate prediction model was established. The results showed that microbial corrosion was the main reason for the corrosion of water injection well string in Bohai Oilfield. The bacteria in the injected water were mainly sulfate reducing bacteria (SRB) and iron oxidizing bacteria (IOB), and the bactericide can effectively reduced the corrosion rate of tubing and casing. The uniform corrosion rates of N80 steel and 3Cr steel in microbial environment were 0.58 mm·a^-1 and 0.27 mm·a^-1, respectively. The uniform corrosion rates after adding fungicide were 0.18 mm·a^-1 and 0.13 mm·a^-1, respectively. N80 steel could not meet the production requirements in the environment without fungicide. Low concentration bactericide had obvious inhibitory effect on the microbial corrosion of oil casing in water injection wells. The selection of 3Cr material and the addition of low concentration bactericide could meet the anti-corrosion requirements of water injection wells.