油气混输管道的内壁腐蚀

Inner Wall Anticorrosion Techniuque for Oil-Gas Mixed Transporation Pipelines

较之单相输送管道，油气温输管道的内壁腐蚀要严重得多。其内壁腐蚀主要是CO2腐蚀和H2S腐蚀。混输管道的腐蚀与流型有关，以段塞流和分层流流型下的腐蚀最具代表性。通常认为，当系统中CO2分压超过20kPa时，该烃类流体是具有腐蚀性的，且CO2腐蚀速度与CO2分压的0．67次幕成正比；当合H2S的天然气输送系统的总压大于0．448MPa、H2S分压高于0．34kPa、介质pH值＜6时，将会发生硫化物应力腐蚀开裂。在油田油气集输系统中，允许的CO2浓度可通过腐蚀诺漠图及计算确定；多相流管道管径的确定亦应当考虑腐蚀问题。

By contrast, internal corrosion of oil-gas mixed flowing pipelines is much severe than single-phase pipeline. In oil-gas pipelines the corrosion are mainly CO2 corrosion and H2S corrosion. The internal corrosion is related to flow pattern,and at the conditions of slug flow and stratified flow,the corrosion characteristics are more representative. As CO2 partial pressure (Pco2 )is greater than 20 kPa,the hydrocarbon fluid in pipeline is corrosive and the corrosion rate is in direct proportion to P. Asthe total presure in the pipeline system is greaterthan 0.448MPa, H2S partial pressure is over 0. 34kPa,and the pH of fluid less than 6,the stress corrosion cracking (SCC)may be occur. In oil-gas gathering and transferring system in oilfield, the allowable concentration of CO, can be determined by corrosion nomogram and calculation. When sizing the diameter of multiphase flowlines,the influence of corrosion must be taken into account.