Research On The Corrosion And Protection Of Gas Pipeline Of CO₂

FangShen-S5 well, containing CO₂ as high as 85%, is CO₂ Gas Well. The String in Downhole, pipeline and equipments on the ground of this Gas Well has been severely eroded, because of the high CO₂ content and water component. There are serious security risks. In order to solve the serious corrosion problem of pipeline and equipments of FangShen-S5 Well, it is an urgent need to studying on the corrosion mechanism of gas pipeline of CO₂ and equipments and some measures against the CO₂ corrosion must be taken for the Well.In this article, the CO₂ corrosion mechanism of gas pipeline of CO₂ is studied by corrosion weigh-loss method in a simulation environment with corrosion environment. SEM, EDS and electrochemical station are used as accessorial analytical method. The valuable experience is accumulated. This paper expatiates on the corrosion mechanism of the CO₂,安and outlines the factors that affect the CO₂ corrosion. On the condition of different temperature and CO₂ partial pressure, It analyzes the corrosion condition of gas pipeline of FangShen-S5 well and the corrosion products, structure and composition of surface morpHology. It's found through the experimental data that 20 steel at 65℃is at maximum corrosion rate of carbon dioxide; the corrosion rate of CO₂ increases by about 3.14 times with three times partial pressure of CO₂ in the corrosion process; while the corrosion rate increases by about 1.65 times with 2.8times temperature. We can conclude that the partial pressure of CO₂ in influencing factors is the main influencing factor and the temperature followed. By scanning electron microscopy for accumulating valuable data, we can knows that the corrosion products on metal surfaces is divided into three tiers: fine-outer layer , loose-middle layer and compact-inner layer.On the basis of studying the mechanism of CO₂ corrosion of gas pipelines of CO₂ with the combination of the existing gas well applications, we put forward the corresponding anti-corrosion measures: selecting a strong anti-corrosion steel for the gas line, reducing the temperature of electric heater or canceling the heater.