长庆油田含硫化氢区块中J55钢套管的腐蚀机理

Corrosion Mechanism of J55 Steel Casing in Block Containing Hydrogen Sulfide in Changqing Oilfield

采用能谱分析仪、扫描电子显微镜、X射线衍射仪等对长庆油田含硫化氢区块中J55钢套管表面的腐蚀产物,及不同腐蚀环境(纯CO_(2)、纯H_(2)S、不同分压CO_(2)+H_(2)S环境)中J55钢试样表面腐蚀产物的组成及形貌进行了分析,计算了腐蚀速率,并研究了含硫化氢区块J55钢套管的腐蚀机理。结果表明:J55钢在纯CO_(2)环境中会形成粗粒径且致密性较差的FeCO_(3)腐蚀产物膜,其腐蚀速率较高;H_(2)S的加入使得J55钢在CO_(2)+H_(2)S环境中形成了细粒径致密性高的FeS腐蚀产物膜,对基体金属能起到一定的保护作用,从而显著降低了腐蚀速率;J55钢在长庆油田含硫区块的腐蚀机理为以H_(2)S腐蚀占主导的CO_(2)+H_(2)S腐蚀。

The corrosion product composition and morphology on the surface of J55 steel casing in H_(2)S containing block in Changqing Oilfield and in different corrosive enviroments(pure CO_(2), pure H_(2)S, different partial pressure CO_(2)+H_(2)S enviroments) were analyzed by energy spectrum analyzer, scanning electron microscope and X-ray diffractometer. The corrosion rate was calculated, and the corrosion mechanism of J55 steel casing in H_(2)S containing block was studied. The results show that the coarse-grained FeCO_(3) corrosion product film with low compactness was formed in a single CO_(2)environment for J55 steel, whose corrosion rate was high. The addition of H_(2)S made J55 steel form a fine-grained and dense FeS corrosion product film in CO_(2)+H_(2)S environments, which could protect the base metal and significantly reduce the corrosion rate of J55 steel. The corrosion mechanism of J55 steel in sulfur-containing block of Changqing Oilfield was CO_(2)+H_(2)S corrosion dominated by H_(2)S corrosion.