Corrosion Behavior of Deep Water Oil Production Tubing Material under Supercritical CO₂ Environment: Part II. Effect of Crude Oil and Flow

Deep water oil production tubing materials are exposed to high CO₂ pressure and temperature conditions that can affect the corrosion performance of such materials. The present study aimed to evaluate the corrosion behavior of carbon steel exposed to supercritical CO₂/oil/brine mixtures at different water cuts (0, 30, 50, 70, and 100%), CO₂ partial pressures (8 and 12 MPa) and temperatures (65 and 90°C) in a flowing 25 wt.% NaCl solution. Corrosion behavior of carbon steel was evaluated by using electrical resistance (ER) measurements, weight loss measurements and surface analytical techniques (SEM and EDS). The corrosion rates of carbon steel increased with increasing water cut. There was no indication of corrosion attack with 0% water cut. At lower water cuts (30 and 50%), the steel surface was covered by iron carbonate (FeCO₃), while iron carbide (Fe₃C) was present on the steel surface at higher water cuts (70 and 100%) with very high corrosion rates. In addition, the presence of flow prevented the formation of protective FeCO₃ at high water cut conditions.