咪唑啉类缓蚀剂对 P110 钢在 CO2 注入井环空环境中应力腐蚀行为的影响

目的研究咪唑啉类缓蚀剂对P110钢在CO2注入井环空环境中的应力腐蚀(SCC)行为的影响,为CO2注入井环空环境腐蚀防护方法的建立提供参考和依据。方法在实验室模拟的CO2驱注井环空环境中进行应力腐蚀试验、电化学测试和腐蚀形貌分析。根据现场提取的CO2注入井环空介质的成分分析结果配制模拟溶液,选用咪唑啉类缓蚀剂,调节模拟液p H至4。通入高纯N2进行除氧,以防止硫化物氧化。应力腐蚀试样采用三点弯试样,通过将试样的挠度控制为设定值来控制加载载荷。应力腐蚀试验和电化学试验均在密闭高压釜内进行。实验结束后,采用扫描电镜对腐蚀形貌进行观察。结果在CO2注入井环空环境下,咪唑啉缓蚀剂的浓度对P110钢的SCC行为有重要影响。在拉应力载荷存在时,添加足量的缓蚀剂对均匀腐蚀和SCC均具有较好的抑制效果,但当用量不足时,缓蚀剂的添加会增大P110钢的SCC敏感性,其SCC机制为氢脆与局部阳极溶解的混合机制。因此,P110钢在模拟CO2注入井的环空环境中会发生SCC,其机制为AD+HE机制。结论咪唑啉缓蚀剂的浓度对P110钢的SCC行为有重要影响,足量的缓蚀剂对均匀腐蚀和SCC均具有较好的抑制效果,但浓度不足时反而会增大SCC敏感性。

Effect of Imidazoline Corrosion Inhibitor on Stress Corrosion Cracking Behavior of P110 Steel in Simulated Annulus Environment in CO2 Injection Wells

Objective To study the effect of imidazoline corrosion inhibitor on the stress corrosion cracking (SCC) behavior of P110 steel in simulated annulus environment in CO2 injection wells, in order to provide reference and basis for the establishment of protection method against corrosion in the annulus environment of CO2 injection wells. Methods P110 steel in simulated annulus environment in CO2 injection wells was treated by SCC tests, electrochemical measurements and corrosion morphology analysis. According to the site-extracted component analysis results of annulus medium in the CO2 injection well, simulated solution was prepared in laboratory, imidazoline corrosion inhibitor was selected, and the pH of the simulated solution was adjusted to 4. Highly pure N2 was introduced to deoxidize, in order to prevent the oxidation of sulfide. Three-point bend specimen was used in the stress corrosion test, and the deflection of the sample was controlled at the set value to control the load. Both the stress corrosion test and electrochemical test were carried out in a closed autoclave. After the experiment, the corrosion morphology was observed by scanning electron microscope. Results In the annulus environment of the CO2 injection well, concentration of imidazoline corrosion inhibitor had important effect on the SCC behavior of P110 steel. In the presence of tensile stress load, the addition of sufficient corrosion inhibitor had good inhibition effect on uniform corrosion and SCC, but when the dosage was insufficient, the addition of corrosion inhibitor would increase the SCC sensitivity of P110 steel, and the SCC mechanism was the mixed mechanism of local anodic dissolution and hydrogen embrittlement. Therefore,SCC occured on P110 steel in simulated annulus environment in CO2 injection wells, and its mechanism was AD+HE. Conclusion The concentration of imidazoline corrosion inhibitor posed a significant influence on the SCC behavior of P110 steel. Adequate imidazoline corrosion inhibitor could well inhibit both uniform corrosion and SCC, while the addition of inadequate imidazoline corrosion inhibitor increased the SCC susceptibility instead.