Corrosion of carbon steel infrastructure in the oil and gas industry can occur via a variety of chemical, physical, and/or microbiological mechanisms.  Although microbial corrosion is known to lead to infrastructure failure in many upstream and downstream operations, predicting when and how microorganisms attack metal surfaces remains a challenge.  In crude oil transmission pipelines, a kind of aggressive corrosion known as under deposit corrosion (UDC) can occur, wherein mixtures of solids (sands, clays, inorganic minerals), water, oily hydrocarbons, and microorganisms form discreet, (bio)corrosive sludges on the metal surface.  To prevent UDC, operators will use physical cleaning methods (e.g., pigging) combined with chemical treatments such as biocides, corrosion inhibitors, and/or biodispersants.   As such, it necessary to evaluate the efficacy of these treatments in preventing UDC by monitoring the sludge characteristics and the microorganisms that are potentially involved in the corrosion process.   Microorganisms are often monitored in oil and gas systems using growth-based tests, which provide good baselining data for many operations, but do not capture all the kinds of microorganisms that may be involved in UDC.  Newer genetic detection techniques for microorganisms (often referred to as next generation sequencing, NGS) are being used more frequently in the oil and gas industry to monitor for and detect potential microbial corrosion and the efficacies of chemical treatments. 

 

In this study, we evaluated the efficacies of a biocide and biodispersant being used to prevent microbial corrosion in a large dual diameter crude oil transmission line. Growth-based tests and NGS were used to evaluate the efficacy of the biocide alone, the biodispersant alone, and the combination of both chemicals.  The results indicated that the combined treatment was the most effective in preventing metal damage, and both growth-based and NGS approaches provided value towards understanding the effects of the chemical treatments.  Sludge samples were collected following pigging operations conducted several months later on the same pipeline segment to demonstrate the importance of repeated sampling and monitoring to ensure ongoing pipeline integrity.  The results of this study demonstrate the importance of considering and monitoring for microbial corrosion of crucial metal infrastructure in the oil and gas industry. 


When Metals and Microbes Meet \u2013 Preventing Microbial Corrosion in Oil and Gas Transmission Pipelines

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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