空气钻井中钻具腐蚀与控制分析

CORROSION CAUSED ON DRILLING TOOLS DURING AIR DRILLING AND SUGGESTED CONTROL MEASURES

在空气钻井中,井下流体多属气、液(含盐地层水、外加液体添加剂)、固(钻屑、砂子)多相混合流动的复杂状态,腐蚀性强。此外,还有地层砂子和钻屑对钻具的磨蚀和冲蚀。钻具腐蚀直接影响到钻井施工的进度和经济效益。对空气钻井中影响钻具腐蚀的主要因素和腐蚀机理进行了深入研究成果,结合现场实践和国内外有关研究成果,提出如下控制空气钻井操作中产生腐蚀的方法:通过开钻前分析,一旦证实潜在的腐蚀危险,应考虑结合机械和化学的方法来进行缓蚀;氮气产生装置在减少氧气浓度方面非常有效。建议在充气钻井过程中使用化学缓蚀剂。利用腐蚀试片和监测,同时结合专为高含氧环境设计的化学缓蚀剂组合,可减轻对钻具的腐蚀。

In air drilling, the downhole fluids normally include gases, liquids (brine, liquid additives), and solids (drill cuttings, sands), being highly corrosive to drilling tools under a complicated mixed multi-phase flow condition. In addition, the formation sands and cuttings often cause erosion to drilling tools. The corrosion to drilling tools will directly affect the progress and economic efficiency of drilling activity. In this paper an in-depth study has been made on the main factors of the corrosion and the corrosion mechanism. Through combining with the field practices and the related studies in China and other countries, measures used to control the corrosion during air drilling have been suggested, such as to combine mechanical and chemical inhibition methods once potential corrosion hazards shown by the pre-spud analysis, and to use nitrogen generator to effectively reduce the oxygen concentration. It is also suggested to use chemical inhibitors during aerated drilling process. And combining monitoring using corrosion coupons with inhibitors specially designed for highly-contented oxygen environment can reduce corrosion to drilling tools.