ICT: Isolating The Cause

What is Internal Current Transfer?

Internal Current Transfer (ICT) is a phenomenon observed in pipelines where current bypasses an electrical isolation feature (insulated joint or flange). The presence of conductive fluid (brine) in the pipeline provides an unintended pathway for electrical current and can lead to corrosion on the internal surface of the pipeline.

In a pipeline, insulated/isolated flanges are employed to create a barrier against the flow of electrical currents. Typically, these isolation features are used as part of the cathodic protection (CP) system to ensure that adequate CP current is provided to the pipelines rather than being lost to well casings or site facilities. However, when a low resistivity brine accumulates within the pipeline, it can act as an alternative path for electrical current across the isolation feature, effectively bypassing its protective function. 

As current bypasses the isolation feature through the low resistivity electrolyte within the pipeline, corrosion occurs on the non-protected side of the isolation feature. Because the current is transferring inside the flange, the damage often goes unnoticed until a catastrophic failure occurs.

Assessing ICT Risk

Internal Current Transfer (ICT) poses a severe threat to pipeline integrity under specific conditions. The accelerated corrosion resulting from current pick-up at the wellhead and its subsequent transfer from the site-side of the pipe can rapidly deteriorate flanges, potentially leading to structural failure within a remarkably short timeframe, sometimes as little as weeks.

Interestingly, there are situations in fields characterized by highly saturated brine and relatively low well outputs where removing isolation can be an effective tool to reduce failure risk. This action eliminates the potential difference, and subsequent highly localized current flow observed in ICT, and presents an intriguing paradox: corrosion mitigation, through effective isolation, might inadvertently heighten the risk of failure due to highly localized vulnerability.

So, how do we balance these risks in areas prone to ICT? Our protocol involves a comprehensive evaluation of multiple factors before applying standardized solutions. We consider historical reservoir characteristics including brine concentration and outputs, along with the consistency and fluctuations in well site production volumes. In certain situations, we use a proprietary testing procedure to detect the presence of ICT as a part of our annual survey.

Isolation Monitoring: Regular inspection and maintenance of isolation features are crucial to identify and remediate possible interference before significant damage to the interior of the piping occurs that might compromise the protective barrier of the flanges. Our field staff are trained to collect and interpret diagnostic data while completing annual CP surveys to help identify the presence of ICT before it leads to a failure.

Mitigating The Risk of ICT

Given the detrimental effects of Internal Current Transfer (ICT) on pipeline integrity, corrosion professionals implement various measures to mitigate this issue:

Electrical Interference Bonding: The installation of appropriate interference bonds can help to prevent the unintentional flow of current across the isolation feature. This involves carefully designing and implementing isolation kits and bonding systems to maintain CP system integrity.

Electrical Isolation Enhancements: Various enhancements can be made to the location and sizing of electrical isolation features that can help to mitigate ICT in certain situations. This can include the installation of long line insulators, coated spools, or alternative piping configurations.

Brine Removal or Mitigation: Efforts are made to remove or mitigate the presence of brine inside the pipeline. Techniques such as pigging or chemical treatments are used to reduce or eliminate brine accumulation, thereby minimizing the conductive medium within the pipe.

Cathodic Protection System Enhancement: Cathodic protection systems are sometimes upgraded or re-designed to provide enhanced protection to vulnerable areas - occasionally including the removal of isolation features entirely. Adjustments in current densities or the installation of supplemental anodes can be implemented to reinforce protection. Though often a more costly effort, certain fields demand supplemental efforts based on known reservoir qualities, and network conditions.

These mitigation efforts aim to minimize the occurrence and impact of ICT-induced corrosion, safeguarding the pipeline infrastructure and extending its operational lifespan.

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