High pressure and high temperature corrosion performance of high strength 15 Cr martensitic stainless steel was studied in different severe environments—live acid(10%HCl+1.5%HF+3%HAc+5.1% corrosion inhibitor),spent acid and formation water containing CO2.The results show that the corrosion of high strength 15 Cr martensitic stainless steel in live acid is most serious,and the uniform corrosion rate is far greater than those in spent acid and formation water containing CO2 corrosion environments,but all of them can be acceptable for oilfield.Acidizing corrosion inhibitor displays a good matching ability with the high strength 15 Cr martensitic stainless steel in terms of decreasing the uniform corrosion rate,which changes mainly the anodic process of high strength 15 Cr martensitic stainless steel.The corrosion potential moves to the positive direction,thus the corrosion current density decreases significantly.There are some different degrees of pitting of high strength 15 Cr martensitic stainless steel after corrosion tests in live acid,spent acid and formation water containing CO2,and the pitting density aggravates significantly and the maximum pit depth decreases in the corrosion sequence.
为更好地计算石油套管柱接头的力学性能,基于有限元方法中的“软接触”建立套管特殊螺纹接头接触模型,按照《ISO 13679:石油天然气工业套管及油管螺纹连接试验程序》B系试验载荷包络线对JIPΦ177.8×10.36 mm P110套管特殊螺纹接头进行仿真分析。发现接头螺纹段第1牙、第17牙各表面,密封面,台肩面的等效应力、法向接触应力、位移、法向张开位移、切向相对滑移以及切向接触应力分布的历程输出合理,说明在整个B系载荷包络线加载下,螺纹结构完整性与密封性良好;引入软接触模型后,螺纹啮合部位与接头密封部位接触状态较好,摩擦行为对整个接头的接触状态影响不大。结果表明采用“软接触”有限元模型计算套管特殊螺纹接头的接触问题是可行的。
通过高温高压鲜酸(10%HCl+1.5%HF+3%HAc+5.1%TG201缓蚀剂)、残酸、地层水CO2腐蚀实验及电化学分析,研究TP140钢在苛刻工况条件下的耐蚀性。结果表明:TP140钢在鲜酸、残酸和地层水CO2腐蚀实验条件下,其均匀腐蚀速率分别为3.7490,0.4361和0.5524 mm/a。残酸实验后,试样表面存在不完整Cu膜。未去除Cu膜的TP140钢试样的自腐蚀电位(-658 m V)高于去除Cu膜的TP140钢试样的(-692 m V),腐蚀驱动力小,但其自腐蚀电流密度(3.1141×10-5A/cm2)明显高于去除Cu膜的(1.0926×10-5A/cm2)。相比于TP140钢基体(Fe),Cu为正电性金属,膜的覆盖不致密形成典型的大阴极-小阳极结构,导致严重的局部腐蚀。TP140钢在鲜酸、残酸和地层水CO2腐蚀实验条件下,试样表面最大点蚀深度可达150μm。
