Dealing with Unexpected "Synergy" from Bacteria & Sand in Condensate Pipeline

MIC (Microbiologically Influenced Corrosion) is a well-known source of corrosion which could lead to failure in oil and gas facilities. Common mitigation to control the corrosion due to bacteria shares many success stories, however, a 51 km of 14” condensate line was found severely suffering from MIC, despite the implementation of the mitigation in place. A thorough review of the operating condition, fluid sources, pipeline profile, flow regime and applied mitigation - including sand production trending - was done with the main findings indicating that a combination of the above situation triggered an unexpected thinning rate due to a “synergy” of bacteria and evidence of sand inside the line at the first 23 km of the line. A significant thinning rate up to 80% NWT (Nominal Wall Thickness) was identified from ILI (In-Line Inspection) result, which triggered the pipeline replacement and more effort to ensure the new pipe will not suffer similar failure. This paper will describe the lessons learned in dealing with the “synergy” of bacteria and sand and new approach for MIC mitigation under this specific condition, as well as tips to prevent similar cases in the future.