Abstract
The use of analytical techniques to monitor the level of corrosion inhibitors is widespread in the industry. Residual chemical analysis, either qualitative or quantitative, yields information that relate to the corrosion protection in the system. The residual methods have the advantage of speed, sensitivity, ease of setup and low cost and can be excellent tools provided that the field and laboratory personnel understand the limitations. The accuracy of a chemical analysis is as good as the sample submitted; hence, samples must be representative of the system being monitored. The use of residual analysis for monitoring of sweet corrosion and recommended guidelines for the analysts to achieve the accuracy and precision of the analysis are discussed in the paper. Field case histories involving equipment leaks in gas/condensate production systems with sweet corrosion problems are presented in the paper. In one case, the cause of the leaks was traced to changes in the field conditions that impacted the performance of the corrosion inhibitor being monitored by residual analysis. In the other system, the leak in the pipeline occurred in an elbow. The mechanical configuration of the pipeline, variable high and turbulent velocity flows, solids carried by the fluids promoted corrosion-erosion processes in some areas. In both situations, the applicability of the chemical inhibitors and the analytical procedures to the changes in the field conditions was reviewed and the appropriate program revision put in place.
