Corrosion Behavior of Super 13Cr Steel in Three Super Environment of Gas Well in West of China

The corrosion behavior of super 13Cr steel in the “three super” environment of western oilfield gas well was investigated by weight loss method in autoclave. The corrosion rate was characterized with variation of temperature, CO2 partial pressure, Cl- ion concentration and flow rate. The micro-morphology of corrosion products formed on 13Cr steel was analyzed by scanning electron microscopy. The results show that uniform corrosion occurred in the environment containing CO2 and the corrosion product layer was thin, flat and dense. The corrosion rate increased with the increase of temperature, and reached a macimum value when the temperature was 180 ℃; the variation tendency of corrosion rate with CO2 partial pressure and chloride concentration is similar, firstly reached the maximum value at 3 MPa and 50 g·L-1, respectively, and then decreased with the increasing those two factors. The corrosion rate increased with flow rate when it was smaller than 2 m·s-1, and then the corrosion rate had little change with the further increase of flow rate. In all test conditions, the severity of super 13Cr steel corrosion rate was mild or moderate. The results show that super 13Cr steel is suitable for “three super” gas well tubing.