The application of corrosion inhibitors to mitigate carbon dioxide corrosion in offshore oil and gas pipelines has been practiced for several tens of years. In many instances, the performance of the corrosion inhibitor has achieved the mitigation required and as such, the use of such products has become commonplace. However, the depletion of relatively easily accessible reserves has focused attention on deeper, hotter and frequently more corrosive fields.

The concept that the injection of a corrosion inhibitor demonstrated to achieve a corrosion rate of less than 0.1 mm/y on a representative piece of carbon steel in a static or rotating autoclave is a panacea for aqueous carbon dioxide corrosion is becoming less evident in upstream operations. Considerations regarding the impact of the active inhibitor molecules preferentially partitioning into either the water phase or the liquid hydrocarbon phase and the availability of the inhibitor molecules at top of line locations appear less frequent and the requirement to conduct corrosion inhibitor testing in representative conditions using representative fluids and representative materials is seen as a nuisance rather than a fundamental. Typical test requirements for the assessment of a carbon dioxide corrosion inhibitor, for application in a subsea pipeline, and user expectations are identified and discussed together with some general considerations relating to the production of more aggressive fluids.

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