Sodium bromide brine (NaBr) has been widely used as a packer fluid in well completions for more than 20 years. While NaBr brines exhibit low corrosion even at high temperatures, some oilfield tubular materials are susceptible to pitting and localized corrosion. Traditionally, film-forming amine and low molecular weight inorganic sulfur (SCN-) chemicals have been added as corrosion inhibitors. However, when applied at high temperature, thermal decomposition has become a critical issue. Furthermore, adverse effects on tubular materials, downhole elastomers and formation rock have been documented. Alternatively, corrosion may be controlled by increasing the pH of the brines. While pH can be raised by the addition of sodium hydroxide (NaOH), lime (CaO), hydrated lime (Ca(OH)2), and the magnesium analogues, these chemicals provide less control and less protection for tubular materials, especially when the influx of an acid gas is possible.

This paper describes laboratory results of a pH buffer applied as a corrosion inhibitor in NaBr brines and field case histories for buffered NaBr packer fluids in high-temperature high-pressure wells. Results from buffer capacity, general corrosion, galvanic corrosion, and stress corrosion cracking (SCC) tests are presented. Field case histories are presented to demonstrate the successful use of the pH buffer in NaBr brines.

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