文昌9-2气田套管CO_2防腐选材优化设计

Optimal design of anti-corrosion material for casing tube in Wenchang 9-2 gas field

文昌9-2气田开发层的CO_2分压高达3.56MPa,井底温度高达165℃。本文采用高温高压动态腐蚀模拟实验研究了不同材质:3Cr、13Cr和超级13Cr套管材质在该环境的腐蚀特征,结果表明,低Cr钢腐蚀速率高,产物膜保护性差,无法满足要求;普通13Cr材质在温度低于140℃时表现为均匀腐蚀,而当温度达到160℃时,表现出了严重的局部腐蚀;超级13Cr材质在所有测试中均表现为均匀腐蚀。综合材质的腐蚀特征、井筒温度和CO_2分压,为文昌9-2气田推荐了混合管材的防腐方案。

The maximum partial pressure of CO2 is 3.46MPa and temperature is 165℃ at the bottom of gas well in Wenchang 9-2 gas field. The corrosion behavior of casing tube materials,3Cr,13Cr and super 13Cr under the conditions were investigated via the simulation test of dynamic corrosion at high pressure and temperature. The results show that carbon 3Cr cannot meet the requirements due to its high corrosion rate and poor protection of corrosion film. General corrosion occurs on normal martensitic stainless steel 13Cr below 140℃,however,serious local corrosion occurs on normal 13Cr above 160oC. Supermartensitic stainless steel super 13Cr performs well in corrosion resistance at all tests. The material selection of casing and tubing for Wenchang 9-2 gas field are optimized considering the corrosion resistance of these materials,temperature and partial pressure of CO2 of the well.