压应力对特殊螺纹套管材料腐蚀的影响

Influence of compressive stress on corrosion of premium connection casing material

关键词:  套管  油管  特殊螺纹  碳钢  不锈钢  压应力  腐蚀

Key words:  casing  tubing  premium connection  carbon steel  stainless steel  compressive stress  corrosion

摘要:

设计模拟材料承受压应力的夹具,运用高温高压釜,试验研究不同压应力下两种套管钢材料在硫化氢、二氧化碳与氯离子共同作用下的腐蚀速率,测试压应力作用下套管钢材料的腐蚀电化学行为。结果表明:在试验介质中石油套管材料腐蚀形态为点蚀,压应力的增加对试样的腐蚀有促进作用;当压应力小于材料屈服强度的一半时,材料腐蚀不明显,当压应力大于材料拉伸屈服强度的一半以后,材料腐蚀速率快速增加;石油套管与油管特殊螺纹接头密封面及扭矩台肩压应力设计值不应超过材料屈服强度的一半。

Abstract:

The fixture was design to simulate material enduring compressive stress, and the fixture was put in high temperature autoclave, and the corrosion rates of two kinds of casing materials(carbon steel and stainless steel) enduring compressive stress were tested in H₂S and CO₂ and CL-water solution. The corrosion electrochemical behaviors of the steel casing were tested under compressive stress. The results show that the corrosion morphology of oil casing is pitting in the test medium. The compressive stress accelerates the corrosion of petroleum casing steel. When the compressive stress is less than the half of the material yield strength, material corrosion is not obvious, and the corrosion rate increases quickly when compressive stress is greater than the half of the yield strength. The compressive stress design values of oil casing and tubing premium connection sealing surface and torque shoulder should not exceed the half of yield strength of material.