Investigation On Corrosion And Protect Of Cr13 Steel In Saturated CO₂/H₂S Medium

Corrosion has been increasingly becoming a major obstacle to the sustainable development of oilfields.Oil production fluid containing H2S, CO2, corrosive anions as well as others cause steel corrosion under temperature and pressure during oil production. It is imperative to study and protect corrosion as corrosion has restricted developing, manufacturing and transporting in oilfields.So far, a few papers about corrosion mechanism and protection methods of 13Cr steel have been published.Weight loss method, electrochemical measurement techniques and surface analytical technology were used to study the mechanism and main influence factors on 13Cr steel in CO2 and H2S saturated system. At the same time, the inhibition effect and mechanism of the surfactants to control corrosion of 13Cr steel in CO2 and H2S saturated system were discussed. The main conclusions are as follows:1. Effect of concentration of Cl- on Crl3 steel corrosion behavior in CO2 and H2S saturated system Corrosion rate of Cr13 steel in CO2 and H2S saturated system was accelerating as the concentration of Cl- increased at the different temperature, and reached the maximum value at 200 g/L Cl-. It was uniform corrosion at low concentration of Cl-, however, it changed to local corrosion as pitting corrosion when concentration of Cl- was up to 100 g/L Cl-.And the composition of corrosion products on 13Cr steel was affected by concentration of Cl-, mainly FeS at low concentration of Cl-, mostly FeS and low Fe7S8 at 100 g/L, and mainly Fe1-xS at 200 g/L.2. Effect of concentration of temperature on Cr13 steel corrosion behavior in CO2 and H2S saturated systemCorrosion rate of Crl3 steel in CO2 and H2S saturated system was accelerating as temperature increased at low concentration of Cl-, and reached the maximum value at 90℃.Corrosion rate of Crl3 steel was accelerating as temperature increased at 100 g/L and 200 g/L Cl-.And the composition of corrosion products on 13Cr steel was affected temperature, mainly FeS at low concentration of Cl-, mostly FeS and low Fe7S8 at low temperature, and mainly Fe1-xS at high temperature.3. Study on inhibition of n-2-n Gemini surfactantsInhibition efficiency of n-2-n Gemini surfactants effect on Cr13 steel CO2 and H2S saturated system containing 50 g/L Cl- was increased with the increasing of surfactants concentration at different temperature. The adsorption mechanism of this cationic gemini surfactants on steel surface in CO2 and H2S saturated system was found to be fitted with Langmuir adsorption model, and it is spontaneous process.