This paper builds on the evidence for the optimum dose of organic film-forming corrosion inhibitor (FCCI) being at the critical micelle concentration (CMC) of the surfactant components, and the concept of micelle detection as a tool for understanding the effectiveness of the inhibitor dose in the field, which has been presented previously. It extends the underlying principles from laboratory testing, to the rapid analysis of field fluids and explores the different results available from alternative instrumentation.

An inhibitor optimisation trial was undertaken on an offshore oil production platform for protection of a subsea pipeline used to tie back wells 10 miles from the platform. Two micelle detection devices were used, both primarily using fluorescence detection – a simple handheld device for offshore testing and a more complex device used for testing shipped samples in an onshore lab. Electrochemical corrosion monitoring was also used to analyse the produced fluids as the inhibitor dose was varied from zero to 200% of the estimated optimum dose.

Results were clouded by a number of operational issues outside the control of the experiment but interpretation of the whole suggested that the offshore portable micelle analysis was overcome by large quantities of dispersed oil which masked the optical process. However the onshore testing gave some promising results, demonstrating a correlation between increased micelle levels and high inhibitor dose and suggesting that the original dose was sub-optimal.

These experiments supported the need to use the more complex instrument to be able to detect micelles in very impure systems. Making and testing such a device suitable for field operations is now a priority.

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