Microbial under-deposit corrosion of pipeline steel in alkali/surfactant/polymer solution

Alkali surfactant polymer (ASP) flooding technique is deployed in the oil industry to enhance oil recovery (EOR), especially in aged reservoirs. Microorganisms have been found to utilize the polymer constituent as a nutrient source to accelerate steel corrosion. This work aimed at examining the contributions of microorganisms, sediments, and polymer degradation to the overall corrosion behavior of steel pipes used in ASP flooding system via electrochemical, microscopic, and spectroscopic characterization techniques. The results demonstrate that rust deposition significantly influenced the steel's electrochemical behavior in the SRB-containing ASP solution; driving internal polarization and potential difference with the bare metal thereby establishing a galvanic interaction to accelerate steel corrosion. After 14 days of testing in the SRB environment, the steel covered by rust deposits recorded the most severe localized corrosion of all samples under examination, whereas pitting severity significantly reduced on the bare steel and the sand-deposited coupon. Factors such as sediment conductivity, film development, and microbial activities played crucial role in exacerbating steel corrosion under the rust deposits in the SRB-inoculated ASP solution.