Specialty Corrosion Inhibitor Successfully Inhibits Offshore Corrosive Mercury-Containing Gas Stream Offering

This paper presents a real case illustrating a challenge where an offshore gas operator observed severe bottom of line corrosion associated with presence of mercury. The uninhibited corrosion rate exceeded 5 mm/yr with the total concentration of mercury present being around 60-100 ppm. Several corrosion inhibitor formulations were reviewed, studied for thermal stability and compatibility with produced brine. After passing no HARMS testing, a specially formulated corrosion inhibitor was evaluated for performance in the high-pressure rotating cage cylinder electrode (HPRCE) under field's simulated sour and sweet conditions in the presence of mercury. Furthermore, successful inhibition performance across weld electrodes representing pipe material was also reported. This corrosion inhibitor was then field deployed with great performance. The presence of mercury and the range of operating conditions meant that effective chemical dose rates had to be field optimized to effectively control the localized corrosion. Corrosion rates were also monitored via high sensitivity ER probe and are presented in this work.

In oil and gas production, corrosion is a major cause of failures. These failures result in significant environmental contaminants, safety problems, increase in the high operating costs and decrease in the production rates. Extensive literature is available about various corrosion drivers and their mechanisms, helping operators to avoid or mitigate these catastrophic failures. However, literature about the adversities of mercury presence on the corrosion behavior of metallic materials in a reservoir or pipeline environment is limited. Mercury occurs in reservoirs in many forms, e.g., as inorganic mercury, as organic mercury and as elemental mercury. Mercury presence provides corrosive elements to carbon steel metallurgy and interferes with the corrosion inhibition mechanism.