低H2S、高CO2超深井环境中P110SS抗硫钢的腐蚀行为

目的研究高温条件下抗硫低合金钢P110SS在低H2S、高CO_2环境中的腐蚀行为。方法模拟我国西部酸性油田工况环境,利用高温高压设备,通过失重法测试腐蚀速率,并用SEM、EDS和XRD分析腐蚀产物。结果在8 MPa的纯CO_2环境中,腐蚀速率随温度升高而降低,210℃时为0.35 mm/a,腐蚀产物为碳酸盐。当加入6 k Pa硫化氢时,腐蚀速率依然随温度升高而降低,150℃时为0.74 mm/a,腐蚀产物呈现双层结构,内层为结晶良好的FeCO_3,外层为FeS。当硫化氢分压升至165 k Pa时,腐蚀加剧,且腐蚀速率随温度升高而增大,210℃时达2.78 mm/a,腐蚀产物主要为铁的硫化物,同时随腐蚀时间延长至2160 h,腐蚀速率有所降低。结论在纯CO2环境中,高温时生成的内层碳酸盐腐蚀产物膜相对完整,对基体的保护能力较强。当加入6 k Pa硫化氢时,腐蚀由CO_2主导,呈现与纯CO_2环境中相同的腐蚀速率规律,内层的FeCO_3细密均匀。当硫化氢分压升至165 k Pa时,腐蚀由H_2S和CO_2混合控制,疏松破损的铁的硫化物无法对基体形成良好的保护,因此腐蚀速率显著升高。

Corrosion Behavior of P110SS Anti-sulfer Pipeline Steel in Low H2S and High CO2 Partial Pressure Environment of Ultradeep Well

ABSTRACT:Objective To study the corrosion behavior of anti-sulfer lean alloy steel P110SS in high temperature environ-ment containing low H2S and high CO2.Methods The corrosion rates acquired by weight loss test of P110SS were studied using high temperature and pressure autoclave in the simulated corrosion environment based on acid oilfield in West China. Combined with SEM, EDS and XRD, the features of corrosion products were analyzed.ResultsThe corrosion rate of P110SS diminished with the raise of temperature in single CO2 environment. The corrosion rate was 0.35 mm/a at 210℃. The same regular pattern appeared when 6 kPa H2S was joined. The corrosion rate was 0.74 mm/a at 150℃. And the scales on the steel had a two-layer structure. The inner layer consisted of fine-grained FeCO3 and the outer layer was mainly composed of FeS. When H2S partial pressure increased to 165 kPa, the corrosion aggravated and it presented the opposite law of corrosion rate. The corrosion rate was 2.78 mm/a at 210℃. The main product was iron sulfide. Meanwhile, the corrosion rate decreased when the corrosion time was prolonged to 2160 h. Conclusion The mechanism of the above-mentioned variations was discussed according to the analy-sis on characteristics of corrosion products in different conditions. In single CO2 environment, the inner corrosion scale gener-ated at high temperature, which was flawless carbonate, could protect the substrate preferably. It showed the same regular pat-tern owing to the domination of CO2 when 6 kPa H2S was injected. The inner FeCO3 scale was fine. With the H2S partial pres-sure increased to 165 kPa, the corrosion process was controled by H2S and CO2. The corrision rate rose notablely due to the poor protection effect of loose and worn iron sulfide.