胶凝酸及酸化返排液中钛合金管材均匀腐蚀行为研究

Study on Uniform Corrosion Behavior of Titanium Alloy in Oilfield Gelled Acid and Acidification Flowback Fluid

针对钛合金油管在酸化作业中的腐蚀问题,开展了在不同温度、压力、流速及添加不同比例缓蚀剂的胶凝酸溶液及酸化返排液中钛合金管材的均匀腐蚀试验。利用扫描电镜、EDS等工具分析了腐蚀形貌和表面腐蚀产物。结果表明:随着试验温度从50℃升至150℃和试验压力从5 MPa增至10 MPa,钛合金管材在0.1 mol/L浓度胶凝酸中腐蚀速率明显增加,且在5 MPa、150℃或10 MPa、100℃条件下发生溶蚀现象。而在90~160℃、16 MPa条件下,添加3%~6%质量分数的钼酸钠类缓释剂可明显降低腐蚀速率,但在3%缓释剂的90℃溶液中,流速增至60 r/min则导致管材腐蚀速率增加约4.5倍。同时,在高温酸化返排液中钛合金管材仍存明显动态腐蚀,需要添加一定比例缓释剂控制钛合金的腐蚀速率。

In order to solve titanium alloy oil pipes corrosion during acidification operations,uniform corrosion tests were conducted on titanium alloy pipes in gelled acid solutions at different temperatures,pressures,flow rates,and addition of different ratios of corrosion inhibitors,as well as in acidified flowback fluids.The surface morphology and corrosion products of the sample were analyzed by tools such as Scanning Electron Microscopy and Energy Dispersive Spectrometer etc.The results show that the corrosion rate of titanium alloy in 0.1 mol/L fresh gelled acid significantly increases with the rise of temperature from 50℃to 150℃and pressure from 5 MPa to 10 MPa.Corrosion occurs under conditions of 5 MPa at 150℃,or 10 MPa at 100℃.The dynamic corrosion rate of titanium alloy in the gelled acid solution at 90℃to 160℃was significantly reduced by adding 3%~6%mass ratio of sodium molybdate corrosion inhibitor.The corrosion rate was increased about 4.5 times with increase of flow rate to 60 r/min in a solution with a 3%corrosion inhibitor at 90℃.The obviously dynamic corrosion for titanium alloy pipe was observed in high temperature flowback fluid after acidification operation and can be controlled by adding a certain proportion of corrosion inhibitor.