南海某油田CO2回注井防腐选材实验

Anti-corrosion Material Selection Experiment of CO2 Reinjection Well in an Oil Field in South China Sea

目的开展腐蚀选材实验,确定经济合理的井下油套管材质。方法分别模拟回注气层(114℃、CO2分压为24.89 MPa、凝析水Cl^–质量浓度为1000 mg/L)、回注水层(117℃、CO2分压为28.39 MPa、凝析水Cl-质量浓度为20000mg/L)工况,利用高温高压釜开展室内模拟腐蚀实验,评价3Cr、13Cr、超级13Cr和22Cr双相不锈钢材质。结果3Cr出现严重的均匀腐蚀及点蚀,最大均匀腐蚀速率出现在回注水层工况,达1.0973 mm/a;最大点蚀速率出现在回注水层工况,达0.4241 mm/a。13Cr均匀腐蚀速率较低,最高腐蚀速率为回注气层工况,达0.0274 mm/a;在回注水层工况条件下,点蚀速率较高,为0.3833 mm/a。S13Cr均匀腐蚀速率较低,回注气层工况腐蚀速率最高,达0.0113 mm/a,无点蚀。22Cr均匀腐蚀速率较低,为0.0011mm/a,无点蚀。整体规律为回注水层条件下的腐蚀速率大于回注气层,主要腐蚀产物为FeCO3,对13Cr以上管材,主要腐蚀形式为点蚀。结论对CO2回注深井,应尽量选取气层回注。在CO2分压为24.89MPa、地层温度为117℃、地层水Cl^–质量浓度为20000mg/L条件下,推荐选用超级13Cr为回注井管材。

Corrosion material selection experiments are carried out to determine economical and reasonable downhole tubing and casing materials.The reinjection gas layer(114℃,CO2 partial pressure of 24.89 MPa,condensate water Cl^–concentration of 1,000 mg/L),reinjection water layer(117℃,CO2 partial pressure of 28.39 MPa,condensate water Cl–concentration of 20,000 mg/L)working conditions are simulated respectively to conduct indoor simulated corrosion experiments using high temperature autoclaves,and the materials of 3Cr,13Cr,super 13Cr and 22 Cr duplex stainless steels are evaluated.3Cr has severe uniform corrosion and pitting corrosion;the maximum uniform corrosion rate is up to 1.0973 mm/a under the reinjection water layer condition,and the maximum pitting corrosion rate is up to 0.4241 mm/a under the reinjection water layer condition.The uniform corrosion rate of 13Cr is relatively low;the highest corrosion rate is up to 0.0274 mm/a under the reinjection gas layer condition,and the pitting corrosion rate is 0.3833 mm/a under the reinjection water layer condition.The uniform corrosion rate of S13Cr is low;the highest corrosion rate is 0.0113 mm/a under the reinjection gas layer;no pitting corrosion.22Cr has uniform corrosion rate lower than 0.0011 mm/a,without pitting corrosion.The overall rule is that the corrosion rate under the condition of the reinjection water layer is greater than that of the reinjection gas layer.The main corrosion product is FeCO3.For pipes above 13Cr,the main form of corrosion is pitting.For CO2 reinjection deep wells,gas reservoirs should be selected for reinjection as much as possible.Under the conditions of CO2 partial pressure of 24.89 MPa,formation temperature of 117℃,and formation water Cl^–concentration of 20,000 mg/L,Super 13Cr is recommended as reinjection well tubing.