Cailiao Baohu (Apr 2023)
Research on Main Controlling Factors of the Corrosion of L80-3Cr Tubing in an Offshore Oil Field and Evaluation of Protection Methods
Abstract
In view of the working environment of the L80-3Cr tubing in an offshore oilfield in China，the weight loss method was employed to study the effects of carbon dioxide partial pressure，corrosive medium flow rate and corrosive medium gas-liquid ratio on the corrosion rate of tubing materials.Results showed that as the partial pressure of carbon dioxide increased，the corrosion rate of L80-3Cr increased firstly and then decreased，which reached the maximum when the partial pressure of carbon dioxide was 3.0 MPa.The results of SEM observation and XRD analysis on the surface of the sample possessing the highest corrosion rate showed that the corrosion product film formed on the surface of the sample was mainly composed of ferrous carbonate，and the poor film compactness and loose porosity were the main reasons for high corrosion rate.In corrosive medium with low flow rate，the corrosion rate of L80-3Cr was relatively small.However，the corrosion rate of L80-3Cr increased rapidly in high-velocity corrosion medium.Furthermore，gas-liquid two-phase flow passing through the surface of the sample could increase the corrosion rate of the material.With the increase of the gas content in the corrosive medium，the corrosion rate of the sample increased firstly，and then decreased slightly after the gas-liquid ratio increased to 0.227.Besides，the performances of hybrid corrosion inhibitors commonly used in oilfields were evaluated by electrochemical tests.The inhibition efficiency increased slightly with the increase of the concentration of corrosion inhibitor.The corrosion inhibitor mainly inhibited the occurrence of corrosion by adsorbing the film at the interface of the metal solution to enhance the polarization resistance of the corrosion reaction.
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