The Corrosion Rule Of The Oil Tube And Annular Tube When The CO₂ And H₂S Exist

Recently, the eastern oil field has entered the later stage of production, and the western oilfield has increase the development efforts especially under the acidic environment. So thecorrosion problem in the course of production is becoming more and more serious. The thesisanalyze the corrosion phenomena of the oil tube and annular tube as well as its cause. Besides,we introduce the computing technique of the corrosion prevention used in the production.The thesis get the corrosion rule by simulating reality in the lab according to an oil field'sproduction fluid and behavior, supplying the reference for the selection of the anti-corrosionmaterial. In the experiment, we simulate the scene in 80℃and 40℃. The material P110 carryout the weightlessness experiment when the partial pressure is 0.1MPa. The material 110S'sCO₂ partial pressure is 0.5MPa, and 13Cr's & CO₂'s partial pressure is 2.5MPa. Besides, whenthe temperature is 80℃and 40℃as well as the H₂S partial pressure is 0.5MPa and 0.01MPa,we carry out the weightlessness corrosion experiment at different CO₂ partial pressure. By theexperiment, we analyze the corrosion rate, corrosion products appearance and ingredient,corrosion microstructure and so on.According to the experiment, we get the following conclusion.When the CO₂ exists, itmainly appears the CO₂ weightlessness corrosion. With the decline of the temperature or theCO₂ partial pressure, their corrosion rate minish. That's because there will be a FeCO₃ film togenerate at the bottom and at high temperature. The film is rough, porous and very thick, andthe pores are the anodic active sites, so they cause the generating of deeper pores so that therewill be more serious corrosion. When there exists CO₂ and H₂S in the weightlessnessexperiment, the temperature is 80℃and H₂S partial pressure is 0.5MPa, if the CO₂ partialpressure is high, there will be more effect of the corrosion rate to the material P110 and 110S.However, when it is low, the effect is small. We find that when the CO₂ and H₂S partial pressure ratio is 250, there appears the maximum to both materials. 13Cr's corrosion rate willdecline first and then increase with the increase of CO₂ partial pressure, but its range ofvariation is small. When the temperature is 40℃and the H₂S partial pressure is 0.5MPa,although the P110 and 110S'corrosion rate are high, the range of variation is small. 13Cr'scorrosion rate will increase when the CO₂ partial pressure increase, but its corroion rate isapparently lower that other two materials. That's because there forms the chromic oxidepassive film in the course of corrosion, and the passive film prevent the entrance of H₂S andCO₂ so that it has the protective action.