温度对VM110SS套管钢在酸性环境中腐蚀行为的影响

Influence of temperature on corrosion behavior of VM110SS casing steel in sour environment

关键词:  CO₂  H₂S  VM110SS钢  温度  腐蚀速率  腐蚀产物膜 

Key words:  CO₂  H₂S  VM110SS  temperature  corrosion rate  corrosion product film

摘要:

模拟川东某气田气井封隔器失效后套管面临的腐蚀环境,利用自制高温高压釜进行VM110SS套管钢在总压18 MPa、CO₂分压0.54 MPa、H₂S分压0.41 MPa、温度30～150 ℃条件下的腐蚀实验,得出了该气井工况下温度对VM110SS套管钢腐蚀速率的影响。采用扫描电镜和电子能谱分析方法对试样表面腐蚀产物形貌及成分进行分析。结果 表明,VM110SS钢的平均腐蚀速率随温度的升高呈现先增大后减小的规律,气液相腐蚀速率最大值出现在90 ℃。在90 ℃气相中腐蚀速率为0.838 mm/a、液相中腐蚀速率为1.130 mm/a,发生极严重腐蚀。所有实验温度条件下,试样均发生均匀腐蚀,且腐蚀产物以硫铁化合物为主。本实验为酸性气田在不同井深及温度条件下套管的腐蚀状况评估提供了参考。 

Abstract:

The influence of temperature on corrosion behavior of VM110SS casing steel in sour environment was studied in high temperature and high pressure autoclave by simulating the downhole environment of a gas field in Sichuan. The partial pressure of CO₂, partial pressure of H₂S and total pressure are 0.54 MPa, 0.41 MPa and 18 MPa respectively. The test temperature is from 30 ℃ to 150 ℃. The relation between temperature and corrosion rate of the VM110SS steel can be obtained. The compositions and appearance of corrosion products were analyzed by SEM and EDS. The results showed that the corrosion rate of VM110SS increased firstly then decreased with the increase of test temperature. The maximum value appeared at 90 ℃. The corrosion rate in gas phase was 0.838 mm/a, and the corrosion rate in liquid phase was 1.130 mm/a, which showed a extremely severe corrosion. Uniform corrosion characteristic was presented to specimens at all test temperatures and corrosion product was composed mainly of iron sulfides. The paper provides theoretical basis for casing corrosion mechanism at different temperature and guidance for casing steel selection.