Abstract

This work details a microbiologically influenced corrosion (MIC) failure analysis case study for a produced water pipeline. A pipeline in a shale and tight asset experienced heavy corrosion and ultimate failure within a 7-month period, with estimated corrosion rate at 161 mils per year (MPY), or 4.1 mm per year (MMPY). Upon removal by the inspection team, heavy white deposit buildup (a suspected microbial biofilm) was observed directly associated with the corrosion failure on top of a black scale underlayer. Detailed assessments were performed using ATP photometry, qPCR speciation, and 16S rRNA gene sequencing to profile the microbial population present, which was dominated by high-risk anaerobic microbial strains such as sulfate-reducing bacteria and methanogens. Scale analysis confirmed iron carbonate and iron sulfides associated with microbial iron metabolism and corrosion, and scanning electron microscopy explored surface morphology. This study will lay out detailed root cause analysis and include best practices for MIC diagnosis and recommendations for future prediction and prevention in oilfield assets.

Introduction

Microbiologically influenced corrosion (MIC) is a key oilfield problem associated with microbial activity, and can be described as the accelerated corrosion of surfaces (usually concrete or iron/steel) by the biological action of naturally present or externally introduced microorganisms. MIC incidents can occur anywhere that a system is exposed to the environment, where microorganisms can enter often via fluid flow and colonize various surfaces for their own growth. MIC is a persistent concern in practically any upstream, midstream, or downstream system where water could be present for microorganism colonization, including topside, subsurface, aerobic (with oxygen), anaerobic (without oxygen), and at extreme temperatures and salinities.1-2 This includes subsurface reservoir and well tubing, oilfield separators, fluid pipelines, water dump lines, relief valves, treatment facilities, etc. MIC failures result in process upsets, loss of containment, lost production opportunities, and increased operating expenses.

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