Experiment on sulfate-reducing bacteria influenced corrosion of carbon steels under corrosive working conditions in Tahe Oilfield

In order to study the influence of sulfate-reducing bacteria(SRB) on the corrosion behavior of carbon steel under the corrosive working conditions in Tahe Oilfield, the tests were carried out by simulating the corrosive working conditions with a high temperature and high pressure autoclave to measure the bacteria counts, the corrosion morphology and pitting depth was analyzed with scanning electron microscope and laser scanning confocal microscope, and the corrosion rate was calculated using a weight loss method. The study found out that, under the condition of high salinity(the mass concentration of Cl^- is 11.87×10⁴ mg/L), the temperature rose from 40 ℃ to 80 ℃, and the bacteria counts reduced from 110 cells/mL to 25 cells/mL. The maximum pitting rate, 5.475 mm/a, occurred at 40 ℃, and at 60 ℃, the bacteria activity decreased and the pitting rate decreased at first and then rose with the salinity increase. Under 60 ℃ condition with high salinity, changing the partial pressure of H₂S had no obvious effect on bacteria count in solution, but the pitting rate and uniform corrosion rate decreased. The study results indicate that SRB can survive under the extreme conditions of Tahe Oilfield, temperature rise and increasing of salinity may result in the decreasing of SRB concentration, but partial pressure of H₂S has little influence on SRB concentration. Temperature is an important factor affecting SRB corrosion. The higher the temperature is, the slighter the pitting caused by SRB is. Additionally, increasing of salinity may affect the activity of bacteria, further weakening the pitting due to bacteria.