稠油热采井浅层套管腐蚀机理研究

Research on Corrosion Mechanism of Shallow Casing of Heavy Oil Thermal Recovery Well

为了对浅层套管在地层水环境下的腐蚀产物组分进行化验分析并确认其腐蚀机理,开展了N80、P110、110H、130TT 4种材质在Cl^(-)质量浓度分别为5 000、20 000、40 000 mg·L^(-1)和温度分别为50、100、165、200、280℃条件下的全因子腐蚀实验。结果表明:随着温度升高腐蚀速率逐渐增加,相同温度下,Cl^(-)质量浓度从5 000 mg·L^(-1)增加到40 000 mg·L^(-1),腐蚀速率呈下降趋势,在高温时这种趋势更为显著。为了更好地比较Cl^(-)质量浓度对腐蚀速率的影响,开展了无Cl^(-)、无氧环境、无HCO_(3)^(-)环境下的腐蚀实验,可以看出无Cl^(-)存在时4种材料的腐蚀速率最小,在无氧环境下腐蚀速率远小于含氧环境的腐蚀速率。XRD组分分析测试显示,不同材质、温度、Cl^(-)环境下,腐蚀产物组成未发生明显改变,主要为Fe_(2)O_(3)和Fe_(3)O_(4),Cl^(-)会优先在试样表面吸附形成Fe^(2+),并且作为催化剂加速阳极溶解,阴极反应主要为吸氧反应,O_(2)的存在会导致腐蚀产物转变为Fe_(2)O_(3)和Fe_(3)O_(4),生成的腐蚀产物相对疏松,并且产物膜中存在裂纹,为离子扩散提供通道,导致腐蚀加剧。

In order to analyze and identify the corrosion mechanism of shallow casings in subsurface water environments by laboratory tests on the composition of corrosion products,full-factor corrosion experiments were conducted on four materials including N80,P110,110H,and 130TT under different conditions of Cl^(-)mass concentration (5 000,20 000,40 000 mg·L^(-1)) and temperatures (50,100,165,200,280℃).The results showed that as temperature increased,the corrosion rate gradually rose.At the same temperature,as Cl^(-)mass concentration increased from 5 000 mg·L^(-1) to 40 000mg·L^(-1),the corrosion rate decreased.This trend was more pronounced at higher temperatures.To better assess the impact of Cl^(-)mass concentration on the corrosion rate,corrosion experiments were carried out in environments without Cl^(-),without oxygen,and without HCO_(3)^(-).It was observed that in the absence of Cl^(-),the corrosion rate of the four materials was the lowest.Under oxygen-free conditions,the corrosion rate was significantly lower compared to an oxygencontaining environment.XRD component analysis tests revealed that under different material compositions,temperatures,and Cl^(-)environments,there was no significant change in the composition of the corrosion products.The main components were Fe_(2)O_(3) and Fe_(3)O_(4).Cl^(-)preferentially adsorbed on the specimen surface to form Fe^(2+)and acted as a catalyst to accelerate anodic dissolution.The cathodic reaction primarily involved oxygen absorption.The presence of O_(2) led to the transformation of corrosion products into Fe_(2)O_(3) and Fe_(3)O_(4).The generated corrosion products were relatively porous,and cracks existed in the product film,providing channels for ion diffusion,which exacerbated the corrosion process.