高矿化度油田卤水中pH值对20碳钢在硫酸盐还原菌作用下腐蚀行为的影响

Effect of pH Value of High Salinity Oilfield Brine on Corrosion Behavior of Low Carbon Steel in the Presence of Sulfate Reducing Bacteria

目前对含硫酸盐还原菌(SRB)高矿化度下油气田卤水的腐蚀行为报道较少。采用挂片腐蚀试验和电化学试验法研究了20碳钢在含硫酸盐还原菌的不同p H值高矿化度油田卤水中的腐蚀规律,采用扫描电镜观察试样形貌。结果表明:20碳钢在p H值为5.5的含SRB腐蚀液中的腐蚀较p H值为7.5时严重,是不含SRB腐蚀液中的6倍多;p H值为7.5时,20碳钢表面微生物膜较厚,碳钢的腐蚀速率有所下降,致密的SRB生物膜的形成对溶液中Cl-的迁移起到了阻碍作用,碳钢的腐蚀得到了一定的抑制。

Coupon corrosion test and electrochemical test in high salinity oilfield brine containing sulfate reducing bacteria(denoted as SRB) were conducted to evaluate the corrosion behavior of 20 carbon steel at different pH values of the corrosive solution.The morphology of the corroded steel surface was observed with a scanning electron microscope.It was found that when the pH value of the SRB- containing high salinity oilfield brine increased from 5.5 to 7.5,the corrosion of the tested low carbon steel became more severe therewith.Besides,SRB obviously accelerated the corrosion of the low carbon steel in the corrosive medium(leading to an increase in the corrosion rate by about 6 times).In the SRB-containing high salinity oilfield brine with a pH value of 7.5,a relatively thick SRB biofilm was formed on steel surface thereby reducing the corrosion rate of the steel to some extent.The reason lay in that,along with the formation of the compact SRB biafilm,the migration of Cl^- in the corrosive solution was hindered thereby inhibiting the corrosion of the carbon steel at a certain degree.