含缓蚀剂钻井液对铝合金钻杆材料的腐蚀影响

Effect of drilling fluids containing corrosion inhibitors on aluminum alloy drill pipe corrosion

摘要:

铝合金钻杆在钻井液中发生腐蚀会引发严重的孔内事故。为了延缓钻井液对铝合金钻杆的腐蚀作用，在pH值为10、温度为70 ℃的聚磺体系钻井液中，分别加入一定比例的有机缓蚀剂（十二烷基苯磺酸钠，C18H29NaO3S或SDBS）及稀土缓蚀剂〔硫酸镧，La2(SO4)3〕，通过力学性能测试，研究缓蚀剂对7075系铝合金钻杆材料腐蚀的影响。结果表明：上述2种缓蚀剂均可降低铝合金在碱性钻井液中的腐蚀，提高铝合金钻杆抗拉强度最高达6.73%；合金中Cu、Mg、Si等元素的第二相粒子是腐蚀的敏感区域，第二相粒子脱落后即形成腐蚀坑；在产生腐蚀裂纹时，腐蚀产物主要由Al、C、O等元素组成。

Abstract:

Corrosion of the aluminum alloy drill pipe in the drilling fluid can affect the drilling performance and even cause serious downhole incidents. In order to improve the corrosion resistance of the aluminum alloy drill pipe, the organic corrosion inhibitor (C18H29NaO3S or SDBS) or rare earth corrosion inhibitor (La2(SO4)3) was added at some ratio to the polysulfonate drilling fluid at 10 pH and 70℃, and its effect on the 7075 aluminum alloy drill pipe corrosion was investigated through the mechanical test. The results show that both corrosion inhibitors can reduce aluminum alloy corrosion in alkaline drilling fluids, and improve the tensile strength of aluminum alloy drill pipe by up to 6.73%. The second phase particles of Cu, Mg, Si and other elements in the alloy are the corrosion-sensitive areas. Corrosion pits are formed where the second phase particles have fell off. The corrosion products mainly consist of Al, C, O and other elements.