高酸性气田地面集输管线电化学腐蚀研究

Researches on the Electrochemical Corrosion of the Gathering Lines in Sour Gas Fields

在高酸性天然气的集输过程中,元素硫和凝析水/地层水很有可能沉积在集输管线的底部,导致管线的严重腐蚀。针对这种现象,开展了地面集输管线材料的电化学腐蚀研究。室内研究结果表明,当元素硫悬浮在试验介质中时,L245的腐蚀速率为0.0937mm/a;而试验材料浸没在元素硫中时,L245的腐蚀速率为23.068mm/a,且以局部腐蚀为主。在现场试验条件下,天然气流速为0m/s时,会出现凝析水/模拟盐水以及元素硫的沉积,导致L360的腐蚀特别严重(1.267mm/a),在较高的流速(2.25m/s和4.0m/s)下,随着流速的增大,L360的腐蚀速率有所上升(分别为0.177mm/a和0.362mm/a),但比流速为0时要小;增加水中Cl-含量会加剧材料的腐蚀。研究结果表明,元素硫和地层水/凝析水的沉积对管线腐蚀的影响特别大,应重视其防护方法。

Elemental sulfur and produced water would deposit in the gathering lines of sour gas, and led to serious corrosion of the gathering lines. Based on these phenomena, research on the electrochemical corrosion of the gathering lines were carried out. The laboratory results showed that the corrosion rate of L245 metal was 0.0937mm/a when the elemental sulfur was suspended in the water. It increased to 23.068mm/a when L245 was immerged in the elemental sulfur, and the corrosion type was localized corrosion. The corrosion rate of L360 was 1.267 mm/a when the velocity was very low (for example, 0 m/s) in the field because produced water and elemental sulfur would deposit. The corrosion rate of L360 were 0.177 mm/a and 0.362 mm/a when the velocity of the sour gas was 2.25m/s and 4.0m/s respectively, which were much lower than the corrosion rate in the low velocity (such as 0). The corrosion rate of the materials would accelerate when Cl-content in the water increased. Deposition of elemental and produced water would have a great influence on the corrosion of the gathering lines based on the results. Therefore, inhibition methods should be considered.