油田开采水中铁的去除及其对浊度的影响

IIron Removal and Its Effect on Turbidity in the Oil Field Produced Water

研究了加氢氧化钠去除油田开采水中铁和出水含铁质量浓度对浊度的影响。铁的测定使用邻二氮菲吸收光谱法,浊度采用便携式浊度仪测定。实验结果表明,进水pH对去除铁、降低浊度、处理装置防腐有重要影响。当pH小于7时,除铁效果不理想而且不能抑制处理装置的腐蚀,铁的去除率为负数。pH在8.3左右较佳,此时能达到除铁和抑制装置腐蚀的双重目的,出水总铁含量和浊度可以满足SY/T 5329-94碎屑岩油藏注水水质推荐指标中A1类标准的要求,出水放置2.5 h浊度几乎保持不变。而在pH值为6.6和7.3下由于氢氧化亚铁被氧化使水呈黄色而导致放置水样浊度缓慢上升。理论分析表明混凝剂能促进氢氧化亚铁的沉降,铁的去除机制主要是沉降、过滤拦截、吸附;在低pH值时,由于电化学腐蚀使得处理装置向水体中释放铁,导致出水铁浓度高于进水,在高pH值时,由于保护膜形成和阴极反应受到抑制而阻断了电化学腐蚀。

Iron removal in the oil field produced water and effect of iron mass concentration in the outlet water on turbidity were explored by addition alkali process. Iron contents were determined by 1,10- phenanthroline spectrophotometry and portable turbidimeter was adopted at the determination of turbidity. Results show that pH of inlet water has significant effects on iron removal, turbidity reduce and anti-corrosion of treatment devices. Iron removal is bad and corrosion of treatment device could not be restrained when pH is below 7, which resulted in negative iron removal rate. Better pH is about 8.3 where iron removal and anti--corrosion of treatment devices are attained. And the quality of outlet water can meet the A1 quality standards of recommended indexes in SY/T5329-94 about the injection water quality for clastic rock oil fields, and its turbidity keep invariablenes at a dwell time of 2. 5 h. However, outlet water turidity at 6.6 and 7. 3 of pH rose gradually because of Fe（OH）e oxidation. Coagulant can promote Fe（OH）2 settlement and major removal mechanisms of Fe（OH）2 include settlement, interception based on filtration and adsorption from theoretical analysis. At a low pH, electrochemical corrosion made treatment devices release iron which induces outlet iron contents above inlet iron contents. On the contrary, at a high pH, it is blockaded owing to protective layer formation and cathode reaction suppressed.