Abstract
Mitigating the risk of MIC in oil field production relies heavily on biocides and mechanical cleaning such as pigging. Biocides are often the only option for treating semi-stagnant, sour vessels such as SWD’s, but it can be difficult to know whether biocide treatments are being effective when it comes to stopping or preventing corrosion. To study the effect of repeated biocide treatments to mitigate MIC, we used a once-through biofilm reactor to generate and remediate corrosive biofilms on carbon steel coupons grown solely from a produced water sample from a West Texas SWD. After four weeks of growth, the reactor started receiving a weekly batch treatment of biocide for four consecutive weeks. Coupons were pulled and replaced before and after each batch treatment. ATP quantification was used to test biocide efficacy in real time on sessile and planktonic samples. ATP quantification showed an ~80% percent reduction in sessile microbial activity after each biocide batch and a subsequent 66 – 1649% rebound by the time of the next treatment. Despite this rapid rebound in microbial activity each week, corrosion analysis showed a significant reduction in both pitting and general corrosion rates. DNA sequencing on sessile samples showed that biocide treatments eliminated Methanocalculus, a hydrogenotrophic methanogen, from biofilm reactor bulk fluids.
