NMR Investigation of Viscoelastic Surfactants Compatibility with Corrosion Inhibitors

Abstract

Viscoelastic surfactants (VES) have been successfully applied as acid-diversion fluids. However, high temperature, interaction of VES and metallic cations, alcohol-based additives, and chelating agents all interfere with the apparent viscosity of the VES-based acid and reduce its efficiency. One of the most essential additives in acidizing that can significantly interfere with VES behavior is corrosion inhibitors. Many parameters would impact the performance of corrosion inhibitors including tabular materials, acid types and concentrations, as well as the presence of other additives that might interfere with the corrosion inhibitors. Hence a wide range of corrosion inhibitors is available to address corrosion issues adequately. The present study characterizes the interactions of various types of industrial corrosion inhibitors with different kinds of VES-based systems including zwitterionic and nonionic surfactants. Viscosity measurements were conducted on the VES-based solutions combined with different concentrations of tested corrosion inhibitor formulae, the industrial packages, to characterize the rheological properties of the VES-based acids. To understand the nature of the VES interactions with corrosion inhibitors, nuclear magnetic resonance (NMR) spectroscopy was conducted. The results of rheological measurements showed that addition of different types of corrosion inhibitors in the industrial concentration range leads to change in the conformation of micellar structures and rheology of the VES-based solutions. NMR was conducted to determine the chemical groups involved in the interaction/reaction of corrosion inhibitors and viscoelastic surfactants. Furthermore, the effects of additives and solvents present in industrial corrosion inhibitors were studied. The results showed that amide part of VES is the leading functional group that can interact with corrosion inhibitor solutions and causes alternation of micellar structures due to change in the repulsion forces between surfactants headgroups. The results presented in this study can be used to select corrosion inhibitors more efficiently and optimizing their effectiveness in the presence of VES-based fluids. These results can be utilized to predict any probable interactions and rheological changes in VES-based stimulation fluids due to the addition of corrosion inhibitors.