Laboratory Investigation of MIC Due to Hydrotest Using Seawater and Subsequent Exposure to Pipeline Fluids with and without SRB Spiking

Microbiologically Influenced Corrosion (MIC) is a major threat to pipelines and storage tanks. Even though MIC during hydrotest itself may be limited due to lack of nutrients and a relatively short duration, biofilms left behind may flourish after the pipeline is commissioned resulting in MIC pitting over the long run. This work investigated MIC in simulated hydrotest with X65 coupons using untreated natural seawater and enriched artificial seawater spiked or not spiked with a laboratory strain of Sulfate Reducing Bacteria (SRB) for up to 90 days. The MIC threat after hydrotested pipes were subsequently exposed to pipeline fluids was also investigated by using simulated pipeline fluids containing a mixture of oil, natural seawater and CO₂ or a mixture of oil, simulated formation water (65000 ppm (w/w) NaCl, 22 mM SO₄^2-) and CO₂. Tests were performed at 22°C and 37°C in anaerobic vials. The effectiveness of a 30 minute slug of THPS treatment of the coupons right after hydrotest was also evaluated. MIC pitting was observed in simulated hydrotest using enriched artificial seawater spiked with SRB. MIC pitting was also observed on coupons exposed to simulated pipeline fluids after hydrotesting with SRB spiking using either natural seawater or enriched artificial seawater.