渤海油田中深层低含H2S气井油套管选材研究

Study on Tubing and Casing Material Selected for Low H2S Gas Well in Middle-deep Layers of Bohai Oilfield

目的解决渤海油田中深层低含H2S井下环境的油套管安全选材问题。方法利用高压釜模拟气井的腐蚀环境,对不同材质的备选油套管钢在不同井深模拟工况条件下的腐蚀速率和应力腐蚀开裂行为进行研究,采用电子扫描显微镜(SEM)及其能谱仪(EDS)和X射线衍射分析仪(XRD),分析或检测腐蚀形貌、腐蚀产物的组成,综合考虑均匀腐蚀和开裂,提出该气田的油套管选材方案。结果碳钢在气田工况下均未发生应力腐蚀开裂,但腐蚀速率高,为0.242~0.6003 mm/a。S13Cr在气田工况下均未发生应力腐蚀开裂,中层开发井工况下的最大腐蚀速率为0.0399 mm/a,深层开发井工况为0.1633 mm/a。超级双相不锈钢2507、镍基合金2535在该气田工况下应力腐蚀开裂敏感性低,腐蚀速率分别为0.0122 mm/a及0.0083 mm/a。结论超级13Cr马氏体不锈钢(S13Cr)材质适用于地层温度低于180℃的中层开发井全井段使用,2507超级双相不锈钢及2535镍基合金材质适于温度高于180℃的深层开发井,为节约深层开发井的投资,可以考虑采取组合管柱防腐方案。

To achieve the safe material selection of tubing and casing in the downhole environment with low H2S content in the middle and deep layers of the Bohai Oilfield,this paper simulates the corrosion environment of gas wells through the autoclave,analyzes the corrosion rate and stress corrosion cracking behavior of alternative casing and tubing steels with different materials under simulated working conditions for different well depths,discusses and tests the corrosion morphology and chemical composition of corrosion products by SEM,EDS and XRD,as well as proposes the selection scheme of casing and tubing in this gas field with consideration of uniform corrosion and cracking.There was no stress corrosion cracking of carbon steel under gas field conditions,but the corrosion rate was 0.242 mm/a to 0.6003 mm/a.No stress corrosion cracking occurred in S13Cr un-S13Cr under gas field conditions.The maximum corrosion rate of wells at middle layer is 0.0399 mm/a and that of wells at deep layer is 0.1633 mm/a.2507 super duplex stainless steel and 2535 nickel-based alloy have low susceptibility to stress corrosion cracking in simulated environments,and the corrosion rates were 0.0122 mm/a and 0.0083 mm/a,respectively.According to experimental research results,S13Cr is suggested to be used in whole wells at middle layer with temperature lower than 180℃,and 2507 super duplex stainless steel and 2535 nickel-based alloy are suitable for wells at deep layer with temperature higher than 180℃.In order to save the investment of wells at deep layer,the anti-corrosion scheme of combined string can be considered.