西部“三超”气井环境中超级13Cr钢的腐蚀行为

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

在高压釜中采用失重法研究了井下油管所用超级13Cr钢的腐蚀行为,采用扫描电子显微镜观察了13Cr钢腐蚀产物膜的形貌特征。结果表明,超级13Cr钢的CO_2腐蚀主要是均匀腐蚀,表面形成了一层较薄的CO_2腐蚀产物膜,平整而致密。腐蚀速率随温度增加而增大,在180℃时达到最大值;随CO_2分压和Cl^-浓度变化的规律相似,先增大,分别在3 MPa和50 g·L^(-1)时达到最大,然后又减小;而腐蚀速率随流速先增大,然后在大于2.0 m·s^(-1)后不再变化。试验条件下所得到的腐蚀速率均属于中度及轻度腐蚀。超级13Cr管材在西部三超环境下具有较好的适应性。

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.