L80油管钢在CO2/H2S环境中的腐蚀行为

目的：研究L80油管在CO2/H2S环境中的腐蚀行为。方法利用扫描电镜（SEM）、EDAX能谱分析L80油管内壁腐蚀产物形貌特征和化学组成，采用高温高压反应釜，以实际油水分离的水样为腐蚀介质进行模拟实验，研究原油含水率、CO2/H2S 分压和温度对 L80油管腐蚀速率的影响规律。结果在CO2/H2S环境中，L80油管内壁呈现明显的局部腐蚀特征，部分表面点蚀坑深度超过100μm，形成FeS、FeCO3等腐蚀产物。随着含水率的增加，L80油管腐蚀速率逐渐增大，含水率为30%时的腐蚀速率为0.0377 mm/a，含水率为100%时的腐蚀速率为0.0952 mm/a。CO2分压不变时，随着 H2S分压的增加，L80钢的腐蚀速率增大，H2S分压为0.04 MPa时的腐蚀速率为0.0377 mm/a，H2S分压为0.3 MPa时的腐蚀速率为0.0952 mm/a；H2S分压不变时，随着CO2分压的增大，L80钢腐蚀速率变化不明显且腐蚀速率较小。随着温度的升高，腐蚀速率先以较大幅度增大，再以较小幅度减小，从40℃增加至100℃时，腐蚀速率由0.0083 mm/a升至0.1264 mm/a，100℃左右时的腐蚀速率最大，120℃对应的腐蚀速率为0.106 mm/a。结论 L80油管在CO2/H2S环境中以均匀腐蚀和局部点蚀为主。L80油管腐蚀速率对H2S分压比CO2分压更敏感，CO2分压增大促使具有良好保护性的FeCO3保护膜的形成，降低了腐蚀速率。温度升高至一定范围，导致碳酸盐等难溶性盐溶解度降低，并覆盖在钢表面形成保护层，从而使腐蚀速率下降。

Corrosion Behavior of L80 Tubing Steel in CO2/H2S Environment

ABSTRACT:Objective To study the corrosion behavior of L80 tubing in CO2/H2S environment.Methods Scanning elec- tron microscopy (SEM) and EDAX energy spectrum were used to analyze appearance characteristics and chemical compositions of corrosion products, and simulation experiment was conducted using HTHP autoclave and actual water sample after oil/water separation as the corrosive medium, to study the influence law of water cut, CO2/H2S partial pressure and temperature on L80 tubing corrosion rate.Results In CO2/H2S environment, L80 tubing inwall had obvious local corrosion characteristics, the depth of pitting corrosion in part area was more than 100μm,and corrosion products such as FeS,FeCO3 were formed. With the in-crease of water cut, the corrosion rate of L80 tubing gradually increased, the corrosion rate was 0.0377 mm/a when water cut was 30%, the corrosion rate was 0.0952 mm/a when water cut was 100%. When the CO2 partial pressure was constant, with the increase of H2S partial pressure, L80 steel corrosion rate increased; the corrosion rate was 0.0377 mm/a when H2S partial pres-sure was 0.04 MPa; the corrosion rate was 0.0952 mm/a when H2S partial pressure was 0.3 MPa. When the H2S partial pressure was constant, with increasing CO2 partial pressure, the corrosion rate of L80 steel did not significantly change, and the corrosion rate was smaller. With increasing temperature, the corrosion rate firstly significantly increased, and then decreased with a small-er amplitude. The corrosion rate changed from 0.0083 mm/a to 0.1264 mm/a when the temperature increased from 40℃ to 100℃, and the corrosion rate was the largest at about 100℃. The corrosion rate was 0.106 mm/a when the temperature was 120℃.ConclusionL80 tubing had mainly uniform and local corrosion in CO2/H2S environment. The corrosion rate of L80 tubing was more sensitive to H2S partial pressure than CO2 partial pressure. Good FeCO3 protective film was formed when CO2 partial pressure increased, reducing the corrosion rate. When the temperature increased to a certain range, the solubility of car-bonate and other slightly soluble salts was reduced, forming a protective layer on steel surface to decrease the corrosion rate.