“I Put It in, but Where Does It Go?” – The Fate of Corrosion Inhibitors in Multiphase Systems

Abstract

Abstract Corrosion inhibitors have been used for many years for protecting oil and gas pipelines. The application of small quantities of an inhibitor to production fluids is often one of the most cost-effective methods for imparting corrosion protection in a system. However, even though the practice has become ubiquitous, the industry lacks a comprehensive knowledge of what actually happens to corrosion inhibitor molecules when added into a system. The work reported in this paper addresses some of the principal properties of corrosion inhibitors and how these impact the ultimate fate of the inhibitor in a production system. Specifically, the partitioning behavior of corrosion inhibitors is discussed and how this is affected by changes in inhibitor structure, temperature, brine salinity and oil type. Competitive, parasitic adsorption onto unwanted surfaces is discussed. The affinity of various corrosion inhibitors for sand, iron sulfide, barium sulfate, iron carbonate and emulsion drop surfaces is presented. Additionally, the ability for corrosion inhibitors to stabilize both oil-in water and water-in-oil emulsions is discussed. Phase inversion of the emulsion is demonstrated as production variables change. The impact of each of these factors on the in-situ inhibitor availability (ISIA) and the ultimate corrosion inhibition observed in the field is presented.