Evaluation of corrosivity of produced fluids during SAGD operations
© 2014 by NACE International. Heavy oil extraction using steam flooding methods such as Steam Assisted Gravity Drainage (SAGD) has been used for several decades; yet no severe corrosion damage has been reported despite the presence of 35-40 mol. % CO2 and 2-3 mol. % H2S in the steam chambers. As acid gas partial pressures, pH and temperature traditionally drive corrosion control philosophies, this lack of observed corrosion was not expected. Thermodynamic modeling has been performed to obtain related pH profiles and to estimate carbon steel corrosion rates, in order to better understand the corrosive behavior exhibited by produced fluids under SAGD conditions. The results indicate that the corrosivity of produced fluids is very low despite the relatively high acid gas content. This can be explained by the formation of an adherent "protective" layer of iron oxide products (Fe2O3/Fe3O4) that is present primarily due to two factors; high temperatures (above ca. 130°C) which reduce acid gas solubility and partitioning of the gases primarily into the oil phase. These modeling results are also substantiated by weight loss and electrochemical testing experiments performed in simulated SAGD conditions. Pitting corrosion is also being assessed in this study.
author list (cited authors)
Case, R., Mahajanam, S., Dunn, J., Joosten, M., Achour, M., Marchebois, H., & Bonis, M.