The effect of acetic acid and monoethylene glycol on iron carbonate dissolution in deaerated environment

摘要

Hydrate formation and scale deposition continue to remain a major challenge in oil and gas production and transportation industry. As a result, Monoethylene Glycol (MEG) is introduced into the pipeline as an antifreeze and anticorrosion agent. Recent Investigations have shown that the MEG has to be separated from unwanted substance such as acetic acid (HAc) that are present in the formation water. Internal pipeline corrosion slows and decreases the production of oil and gas when associated with free water and reacts with CO_2 and organic acid by lowering the integrity of the pipe. In this study, the effect of acetic acid (HAc) and monoethylene Glycol (MEG) on iron carbonate layer corrosion were evaluated at 25°C and 80°C using 3.5% NaCI solution in a semi-circulation flow loop set up. Weight loss and electrochemical measurements using linear polarization resistance (LPR) and electrochemical impedance spectroscope (EIS) were used in measuring the corrosion rate as a function of HAc and MEG concentrations. Results obtained shows an average corrosion rate increased from 0.5 to 1.8 mm/yr at 25°C, and from 1.2 to 3.5 mm/yr at 80°C in the presence of HAc. However, there are decrease in corrosion rate from 1.8 to 0.95 mm/yr and from 3.5 to 1.6mm/yr respectively at 25°C and 80°C with the addition of 50% MEG. It is observed that the Fe~(2+) concentration affects the rate of film formation and not the protectiveness. It is also noted that charge transfer control is the main corrosion controlling mechanism under the test conditions. The higher temperature led to faster film dissolution and higher corrosion rate in the presence of HAc. The EIS results indicate that the charge transfer controlled behaviour was as a result of iron carbonate layer accelerated by the addition of MEG concentrations.