A study of the interaction between a kinetic hydrate inhibitor and selected corrosion inhibitors

Abstract

In field operations where natural gas hydrates can occur and CO2 corrosion is a problem, chemicals called inhibitors can be employed. Kinetic hydrate inhibitors (KHIs) and corrosion inhibitors (CIs) are added in small concentrations to ensure flow assurance and for controlling CO2 corrosion. When production chemicals are mixed fatal interactions can arise. Previous studies have been carried out and interactions have been revealed between different commercial KHIs and CIs. Finding a compatible CI/KHI package is of great interest for oil field companies in order to control two hazardous issues during petroleum production. The purpose of this master’s thesis was to study interactions between a commercial KHI and three different CIs. Surface tension measurements were performed prior to the corrosion and hydrate testing. Finding critical micelle concentration (CMC) for each solution containing both inhibitors was needed for selecting the proper CI concentration. Two kinds of tests were performed for evaluating the chemical performance in the presence of one another. Corrosion testing was done in kettle tests by using the linear polarization technique. A hydrate rocking cell system was employed in the hydrate testing. CI efficiency and hydrate induction time was the parameters which were compared among the tests to reveal potential interactions. Corrosion test results revealed a trend of antagonism between the KHI and two of the CIs. The third CI was slightly improved in the presence of the KHI. Hydrate test results revealed an antagonistic effect of CI to KHI performance. The hydrate induction time was reduced by more than 50 % in nearly all the test. One of the inhibitor combinations showed moderately compatibility in both tests. Further research in this area could include a more detailed analysis of each couple to investigate what happens on a molecular level and at a surface. By understanding these mechanisms the search for a compatible CI/KHI package with certain qualities will be more efficient.