Initial Corrosion Behavior of 3Cr Alloy Steel in Urea Assisted Heavy Oil Steam Huff and Puff Environments
The initial corrosion behavior of 3Cr alloy steel in urea assisted heavy oil steam huff and puff environments was studied by means of mass loss measurement,macroscopic morphology observa-tion,SEM,EDS,XRD and XPS.The results show that the initial corrosion of 3Cr alloy steel in urea assist-ed heavy oil steam huff and puff environment is a synergistic corrosion of CO2(acid gas)and NH3(alka-line gas)in high temperature steam,showing uniform corrosion characteristics.The corrosion products are mainly FeCO3.When the concentration of urea solution is in the range between 10％and 20％,with the increase of the concentration of urea solution,the amount and compactness of corrosion products all increase.When the concentration of urea solution higher than 30％,the adhesion of the corrosion prod-uct scale to the steel substrate becomes weaker with the increase of the concentration of urea solution,as a result,obvious spallation of the formed scales may emerge.If there not crude oil exists in the well-bore environment of the urea assisted steam huff and puff production well,the average corrosion rate of 3Cr alloy steel is higher than the oilfield corrosion control index 0.076 mm/a when the concentration of urea solution is greater than 10％,so that this operating condition is not recommended.In the presence of crude oil,the corrosion rate of 3Cr alloy steel is greater than 0.076 mm/a for 30％urea solution,appar-ently which cannot meet the requirements of wellbore corrosion control in production wells,therefore,this operating condition is not recommended too.Anyhow,the average corrosion rate of 3Cr alloy steel with crude oil is lower than that without crude oil.The incorporation of crude oil has certain corrosion inhibition effect due to the geometric covering effect.Therefore,it is suggested that the concentration of urea solu-tion should not exceed 10％when designing the site operation scheme.
3Cr alloy steelurea corrosioncorrosion productheavy oil reservoirsteam huff and puff
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