Protecting Steel: Researchers Advance Fight Against Corrosion

All around the industry, a silent enemy targets oil infrastructure: corrosion. In a bid to protect vital equipment, researchers have been hard at work. At Chevron Technical Center, researchers have developed a screening method for particularly problematic microbiologically influenced corrosion (MIC) while Occidental Petroleum’s Chemical Management Team has developed a means to quantify metal loss as a way to measure effectiveness of corrosion inhibitor (CI) chemicals. Experts from both companies detailed their approaches during the SPE International Conference on Oilfield Chemistry in Galveston in April. Microbial corrosion threatens oil and gas operations, but properly identifying at-risk assets has traditionally been difficult. Researchers at Chevron Technical Center aimed to develop a method for more effective MIC threat screening—helping prevent corrosion, reduce biocide overtreatment, and keep assets online and in good working order. “There’s life in the oil field,” David Leach, production chemistry research scientist at Chevron Technical Center, said. When it comes to microbes in unconventional operations, some are “major bad actors” that can cause problems while others are “always present but not a real problem,” he said. It’s the bad actors, like sulfate-reducing bacteria (SRB), acid-producing bacteria (APB), methanogens, and biofilm formers or slime, that can cause problems, Leach said while presenting SPE 224254. The paper details the process his team followed to identify potential MIC threats in a reservoir or facilities, narrow those contenders to a manageable number for testing, and gain insight into how to best identify actual MIC-related threat. SRB can contribute to H2S production, generate iron sulfide solids, and lead to corrosion. APBs can cause chemical corrosion on steel surfaces, while methanogens can cause iron pitting through electrochemical mechanisms. Biofilm, or slime, can foul up filters, create clogs, and cause both organic and inorganic sludges that can lead to problems, he said. “Bacteria are always going to be present unless you’re really, really salty or really, really hot,” said Leach. Simply identifying MIC-risk elements in downhole or topside environments is not enough because of the many unknown factors contributing to MIC, he explained. Some environments with high levels of traditional MIC indicators show no issues, meaning detection alone doesn’t always correlate with operational impact, he added. MIC has long been a “complex damage mechanism” that can appear unexpectedly and be over- or underdiagnosed, the paper noted. Underdiagnoses can lead to corrosion that requires repair and tacks on capital expenditures, but overdiagnoses lead to unnecessary biocide treatments and drive up operating expenses. The “problematic” trees in the forest of data can make it hard to identify true risk, Leach said.