Effect of Hydrolysed Polyacrylamide Towards MIC Bacteria Growth and MIC Corrosion Rates

Abstract

AbstractMicrobiological-Induced Corrosion (MIC) has become one of the common threats for oil and gas pipelines. Implementation of polymer flooding during enhanced oil recovery (EOR) activities raised a concerned from oil and gas operators, since 90% of the polymer injected found will be backproduced and flow into the pipelines together with the hydrocarbon’s fluids. A study has been conducted to improve the understanding on how HPAM polymer affects MIC bacteria growth, as well as further influenced on the MIC rates. The experimental works started with bacteria culture in anaerobic bottle where their culture media were divided into three set, i.e. blank (without organic carbon), HPAM only and mixture of HPAM with volatile fatty acids (VFA) or lactate. The bacteria in the culture were oilfield consortium bacterium. Metal coupons (Carbon Steel C1018) were immersed in each bottle to allow sessile bacteria to form biofilm on their surface. The incubation temperature was set at 37C to simulate the pipelines’ temperature. After 7, 14, 21 and 28 days, bacteria growth was monitored by enumerating the planktonic and sessile bacteria, and metal coupons were weighted to observe their weight loss and getting their uniform corrosion rate. Once cleaned the coupons will be examined under scanning electron microscopy (SEM) to observe their surface morphology, and subsequently measure their pit depths under infinite focus microscope (IFM) to obtain their pit rate. Results found that bacteria growth were increased up to 4 log higher whenever HPAM is available in the media. However, uniform corrosion rate (UCR) was observed to decrease in each medium, due to precipitation of iron sulphide (FeS) on the coupons surface. Contrast to that, pitting rates were observed increasing on each coupon surface, which finally results in higher pitting rate for all coupons immersed in HPAM-enriched media. The conclusion has been made that the mechanism of MIC in the presence of HPAM is categorized as localized corrosion.KeywordsMicrobiological-induced corrosionEnhanced oil recoveryHydrolysed polyacrylamide