Operators have long observed that the severity of downhole CO2 corrosion is often largely dependent on location in the tubing string. At greater depths (corresponding to temperatures greater than 150 C), ferrous carbonate (FeCO3 or siderite) forms a tight adherent scale, effectively inhibiting corrosion. At intermediate depths, a patchy scale forms which results in accelerated pitting attack. A laboratory apparatus developed to test the temperature dependence of the kinetics and solubility of FeCO3 is described. Field and laboratory observations concerning ferrous carbonate scale adherence are compared to laboratory kinetics data. The solubilities and rates of formation of ferrous carbonate and calcium carbonate scales are contrasted.

You can access this article if you purchase or spend a download.