Introduction

Corrosion inhibitors are complex blends of many different compounds, only a portion of which are nitrogencontaining materials. Other chemicals such as surfactants, emulsifiers, and biocides can also be present. Solvent and carrier systems can include high-boiling-point aromatics, xylene, various alcohols, saturated hydrocarbons, and water. These other chemicals can be just as damaging to particular elastomers as the nitrogencontaining compounds. Furthermore, they can also have synergistic effects that make elastomer degradation much worse than would be observed otherwise.

To understand the interaction between corrosion inhibitors and elastomers used in well equipment, an understanding of the ways inhibitors are used is necessary. The treatment method can be as important as the inhibitor or elastomer type in this interaction because different treatment methods expose the elastomers to a variety of inhibitor concentrations for varying time periods.

Oilfield corrosion inhibitors can generally be divided into two broad classifications based on the carrier system used in the field. Water-soluble inhibitor systems utilize water as the carrier, while hydrocarbon-soluble inhibitors use diesel fuel, kerosene, condensate, or other liquid hydrocarbon as the carrier. In selecting appropriate elastomer systems, it is also important to know the location of the inhibitor system, i.e., in the tubing or annular space.