甲酸盐对套管/油管腐蚀速率评价方法与影响因素  

Method of Evaluating Corrosion Rate of Formates to Casing and Tubing Strings and the Influencing Factors

作　　者：杨向同[1] 肖伟伟[2] 刘洪涛[1] 徐同台[2] 谢俊峰[1] 张瑞芳[2] 

机构地区：[1]新疆库尔勒塔里木油田油气工程研究院,新疆库尔勒841000 [2]北京石大胡杨石油科技发展有限公司,北京102200

出　　处：《钻井液与完井液》2016年第6期51-57,共7页Drilling Fluid & Completion Fluid

摘　　要：由于目前还没有关于甲酸盐腐蚀速率评价标准,借鉴国内外金属腐蚀速率评价方法,提出甲酸盐对石油钻完井用的套管/油管腐蚀速率评价方法。实验采用金属挂片失重法,使用CGF-Ⅱ高温高压静态腐蚀仪,研究了甲酸盐种类、甲酸盐生产工艺、p H值、钢材材质、密度、缓冲剂等因素对腐蚀速率的影响。结果表明,甲酸钠对TP140钢材腐蚀速率是甲酸钾的2倍多,因为甲酸钠中Cl元素含量(0.619%)大于甲酸钾(0.024 3%);由于生产工艺不同,甲酸钾A中S元素含量(0.18%)大于甲酸钾B(0.047 7%)与C(0.04 6%),因而前者的腐蚀速率远高于后2者;酸性条件下甲酸盐对钢材腐蚀程度较为严重,现场应用的甲酸盐盐水需使用碳酸钠/碳酸氢钠或碳酸钾/碳酸氢钾进行缓冲;TP140在甲酸钾盐水中的腐蚀速率是BG13Cr、JFE13Cr中腐蚀速率的20倍,表明甲酸钾对不锈钢的腐蚀速率远低于对碳钢的腐蚀速率;因为高浓度的HCOO-离子才对钢材腐蚀有一定保护作用,所以TP140钢材在1.20 g/cm^3甲酸钾盐水中的腐蚀速率是1.40~1.57 g/cm^3甲酸钾盐水的2倍多,因此在使用低密度甲酸盐体系时需加入缓蚀剂。上述实验结果为石油钻完井过程中使用甲酸盐水时的防腐工作提供了实验依据。Standard method for evaluating the corrosion rate of formatesis not presently available. A method of evaluating the corrosion rate of formates to casing/tubing strings has been presented with an idea borrowed from the methods of evaluating the corrosion rate of metals. In laboratory experiment, metal coupon weight loss method and a CGF-II HTHP static corrosion tester were used to study the influencing factors such as the type of the formate, production technique, pH, steel material quality, density, and retarder etc. It has been found that using TP140 steel coupon, the corrosion rate of sodium formate was more than 2 times that of potassium formate, because the Cl content in sodium formate （0.619%） was greater than the Cl content in potassium formate （0.0243%）. For potassium formate, different production processes resulted in different sulfur contents; potassium formate A contained 0.18% sulfur, far more than that of potassium formate B （0.0477%） and potassium formate C （0.046%）, and thus, the corrosion rate of potassium formate A was much higher than that of the latter two. The corrosion of formate salts to steel is much severe under acidic conditions. Water solutions of formate salts taken from a well site needed to be buffered with sodium carbonate and sodium bicarbonateor potassium carbonate and potassium bicarbonate. The corrosion rate of TP140 steel in potassium formate solution was 20 times of the steel BG13Cr or JFE13Cr, indicating that potassium formate had lower corrosion rate to stainless steel than to carbon steel. Since high concentration of HCOO- is good for the protection of steel, the corrosion rate of TP140 steel in 1.20 g/cm3 potassium formate solution was more than 2 times of the corrosion rate of TP140 in potassium formation solution of 1.40-1.57 g/cm3. Thus, corrosion inhibitors should be used when low density formate muds are used. Based on these experimental data, the use of corrosion inhibition measures can be justifed when using formate drilling fluids.

关 键 词：甲酸盐钻井液 腐蚀速率 套管 油管 

分 类 号：TE254.4[石油与天然气工程—油气井工程]