pH Buffer Provides Corrosion Control Alternative for High Temperature Well Completions

Clear brines have been widely used in well completions for more than 30 years. When applied in packer fluid environments, brine corrosivity is a major concern, especially at high temperatures. Traditionally, film-forming amine and low molecular weight inorganic sulfur chemicals have been used as corrosion inhibitors. However, at high temperature, thermal decomposition of both inhibitors has become a critical issue. Therefore, it becomes necessary to develop a corrosion control alternative for high temperature applications.

This study applied a pH buffer as a corrosion inhibitor in brine packer fluids. The study systematically evaluated the effect of pH buffer on corrosion control of steel materials at elevated temperatures up to 218^oC. The paper describes laboratory results of pH buffer in sodium chloride, potassium chloride, sodium bromide and sodium chloride/sodium bromide brines and field case histories for buffered brine packer fluids in high-temperature high-pressure wells. The pH buffer applied is cost effective, readily available and easily handled and monitored in the field. Results from buffer capacity, general corrosion and stress corrosion cracking tests are presented. Field case histories are presented to demonstrate the successful use of the pH buffer in brine packer fluids at high temperatures.