地层水环境对套管材料腐蚀行为的实验研究

Experimental study on corrosion behavior of casing materials in formation water environment

通过水质检测、套管基体和腐蚀产物分析、套管材料的腐蚀速率及极化曲线实验,研究了套管在套损井地层水服役环境下的腐蚀行为。结果表明,地层水水型为硫酸钠水型,Cl^(-)含量、氧含量、侵蚀性二氧化碳及细菌含量较高,是造成腐蚀的主要原因。套管组织中以多边形铁素体和珠光体为主,含有A类、B类和D类三类夹杂物;D类夹杂物数量最多,A类和B类次之。相对于套管内壁腐蚀,套管外壁腐蚀较严重,腐蚀产物主要是以FeCO_(3)、Fe_(3)O_(4)、FeS为主。4种套管钢的腐蚀速率关系:P110>J55>N80>N80Q,腐蚀电流密度(i_(corr))满足关系:i_(N80Q)<i_(N80)<i_(J55)<i_(P110),与高压腐蚀模拟实验反映的腐蚀速率关系吻合。

The corrosion behavior of casing in formation water service environment was studied through water quality detection,casing matriXand corrosion products analysis,casing material corrosion rate and polarization curve experiments.The results show that the water produced from casing damage wells is sodium sulfate water with high Cl-content,oxygen content,aggressive carbon dioxide content and bacteria content,which are the main causes of corrosion.The casing structure is dominated by polygonal ferrite and pearlite,containing class A,B and D inclusions.The number of inclusions of class D is the largest,followed by Class A and Class B.Compared with the inner casing corrosion,the outer casing corrosion is more serious,and the corrosion products are mainly FeCO_(3),Fe_(3)O_(4) and FeS.The corrosion rate relationship of the four kinds of casing steel is P110>J55>N80>N80Q,and the corrosion current density(i_(corr))satisfies the relationship of i_(N80Q)<i_(N80)<i_(J55)<i_(P110),which is consistent with the corrosion rate relationship reflected in the high-pressure corrosion simulation experiment.