恶劣环境气井井下油管的相变诱导腐蚀研究

PHASE-TRANSITION INDUCED CORROSION OF DOWNHOLE TUBING IN GAS WELLS UNDER HARSH ENVIRONMENT

井下油管的使用寿命和性能与勘探开发和油气田经营效益密切相关,对于含硫气田,还有可能导致重大安全事故和环境问题。而过去的腐蚀机理研究主要集中在化学腐蚀和电化学腐蚀方面,对金属腐蚀类型、腐蚀产物膜的生成与破坏等研究较多。同一口井中处于相同腐蚀环境下井下油管各部位的腐蚀差异较大,这是由于环境因素造成的。为此,从环境因素(井下油管内的油、气、水三相的相态变化)探讨了恶劣环境下气井井下油管的腐蚀受产出流体的组分、温度、压力、油管性能等多方面影响,并针对特定的情况进行了分析。其研究成果有助于相关的决策部门和设计部门找到井下油管严重腐蚀的部位并设计合理的油管组合,可防止或减轻由于腐蚀、冲蚀等对油管造成的严重损坏,大大减少油气井的维护费用,从而取得良好的经济效益。

Due to the hostile working environment,the downhole tubing's working life and performance are closely associated with the exploratory development and the profitability of the oilfield,even probably leading to great safety accidents and environmental problems in those sour gas fields.The former studies on corrosion mechanism is mainly focused on chemical corrosion and electrochemical corrosion,and most research achievements have been concentrated on metal corrosion,formation and destruction of corrosion scaling layer,etc.Great differences were found out at different parts of downhole tubing under the same corrosion conditions,which are resulted from the environmental factors.So.from the perspective of environment,namely the phase transition between the oil,gas,and water inside the downhole tubing,this paper studied the effects of composition,temperature and pressure of produced fluids and tubing properties on corrosion behavior of downhole tubing in a gas well under hostile environments.Special analysis is also made for the given instances.The results will be helpful for the designing and policy-planning departments to locate the most serious corrosion parts of the downhole tubing and then make the proper tubing assembly design to prevent or even eliminate any damage on tubing caused by corrosion or erosion,so as to largely reduce the maintenance costs of wells to get better economic efficiencies.