Abstract
Biocorrosion, also called microbiologically influenced corrosion (MIC), is a major threat to oil and gas pipelines. The formation and morphology of biofilms can be impacted by fluid flow. Fluid velocity affects biocide distribution and MIC. Thus, testing the efficacy of a biocide for the mitigation of MIC under flow condition is desired before a field trial after a static test in vials has confirmed its efficacy. In this work, a bench-top closed flow loop system was set up to investigate the biocide mitigation of MIC of C1018 carbon steel at 25°C for 7 days using enriched artificial seawater. An oilfield biofilm consortium was analyzed using metagenomics. The biofilm consortium was grown anaerobically in the flow loop which had a holding vessel for the culture medium and a chamber in the flow path to hold coupons. Peptide A was a chemically synthesized cyclic 14-mer with its main 12-mer sequence inspired by a biofilm dispersing protein secreted by a sea anemone that has biofilm-free exteriors. The combination of 50 ppm (w/w) THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide + 100 nM (180 ppb) Peptide A (biocide enhancer) resulted in extra 1-log reduction in sulfate reducing bacteria (SRB) sessile cell count and also in acid producing bacteria (APB) sessile cell count compared to 50 ppm THPS alone treatment. Furthermore, with the enhancement of 100 nM Peptide A, extra 44% reduction in weight loss and 36% abatement in pit depth were achieved compared to 50 ppm THPS alone treatment.
