Corrosion Behavior of Deep Water Oil Production Tubing Material Under Supercritical CO_2 Environment: Part 1-Effect of Pressure and Temperature

摘要

The objective of the present study was to evaluate the corrosion properties of carbon steel in supercritical carbon dioxide (CO_2)/brine mixtures related to the deep water oil production development. Corrosion tests were performed in 25 wt°/o sodium chloride (NaCl) solution under different CO_2 partial pressures (4, 8, 12 MPa) and temperatures (65°C, 90°C). Corrosion behavior of carbon steel was evaluated using electrochemical methods (linear polarization resistance LPR and electrochemical impedance spectroscopy EIS), weight-loss measurements, and surface analytical techniques (scanning electron microscopy SEM, energy-dispersive x-ray spectroscopy EDS, x-ray diffraction XRD, and infinite focus microscopy IFM). The corrosion rates measured at 65°C showed a high corrosion rate (～10 mm/y) and a slight difference with pressure. Under these conditions, the sample surface was locally covered by iron carbide (Fe_3C), which is porous and non-protective. However, the corrosion rates measured at 90°C increased with time at the initial period of the test and decreased to a very low value (~0.05 mm/y) due to the formation of protective iron carbonate (FeCO_3) layer regardless the CO_2 partial pressure.