连续油管在四川高含CO_(2)气田环境中的腐蚀规律研究

Study on the Corrosion Law of Coiled Tubing in High CO_(2)Gas Field Environment in Sichuan

针对四川高含CO_(2)气田连续油管作业腐蚀严重的问题,利用高温高压反应釜模拟连续油管作业工况,通过失重法测得CT80和2205DSS油管钢在CO_(2)环境中的腐蚀速率,采用扫描电镜(SEM)、X射线衍射分析(XRD)等表面分析技术对连续油管腐蚀后的表面形貌、元素组成进行分析。结果表明:在CO_(2)为主导的腐蚀环境下,随着温度、压力的升高,气相环境中CT80腐蚀速率逐渐增大,2205DSS腐蚀速率变化不大且较CT80腐蚀速率低;液相环境中CT80腐蚀速率随温度、压力升高呈先增大后降低趋势,2205DSS腐蚀速率较低且变化不大。腐蚀产物微观分析发现CT80液相主要腐蚀产物为FeCO_(3)和Fe_(2)O_(3),产物膜疏松多孔,腐蚀较为严重;2205DSS液相主要腐蚀产物为Cr_(2)O_(3),产物膜较为致密,腐蚀轻微。2205DSS连续油管具有较好的耐腐蚀性能,适合在高含CO_(2)气田中使用。

Aiming at the serious corrosion problem of coiled tubing operation in the gas field with high CO_(2)content in Sichuan,a high-tempera-ture and high-pressure autoclave was used to simulate the working conditions of coiled tubing,and the corrosion rate of CT80 and 2205DSS tub-ing steel in CO_(2)environment was measured by weight loss method.In addition,the surface morphology and element composition of coiled tubing were analyzed by surface analysis techniques such as scanning electron microscopy(SEM),X-ray diffraction analysis(XRD).Results showed that in the CO_(2)-dominated corrosive environment,with the increase of temperature and pressure,the corrosion rate of CT80 in the gas phase environment gradually increased,the corrosion rate of 2205DSS had little change and was lower than that of CT80.The corrosion rate of CT80 in the liquid phase environment increased with the increase of temperature and pressure and then decreased,and the corrosion rate of 2205DSS was very low and changed little.Moreover,microscopic analysis of corrosion products found that the corrosion products of CT80 liquid-phase corrosion specimens mainly were FeCO_(3)and Fe_(2)O_(3),and the product films were loose and porous,indicating that the corrosion was more serious.Comparably,the corrosion product of 2205DSS liquid-phase corrosion specimens were mainly Cr_(2)O_(3),and the product film was denser,indicating that the corrosion was slighter.Overall,2205DSS coiled tubing had good corrosion resistance and was suitable for use in high CO_(2)gas fields.