Study on Corrosion of Pipe for Offshore Production Water Reinjection and Corrosion Inhibitor Evaluation Taking Western Oilfields in South China Sea as An Example
In view of the problems that the corrosion degree of pipeline is difficult to be quantitatively described and seriously difficult to control in the process of production water reinjection development in offshore oilfields,taking the western oilfields in the South China Sea as an example,the corrosion experiments were carried out by using high temperature and high pressure reactor based on oil field working condition parameters.The corrosion of three wellbore pipe steels was analyzed.A quaternary ammonium salt corrosion inhibitor was synthesized,and the corrosion inhibition effect was evaluated.Then the corrosion type of the steels was determined by electrochemical test,isothermal adsorption model and SEM,and the action mechanism of corrosion inhibitor was studied.The results show that the wellbore pipe steels produce serious corrosion during production water reinjection,and the pitting corrosion rate is high.After adding the synthetic corrosion inhibitor,the uniform corrosion rate of all steels is lower than 0.12 mm/a,which can effectively slow down the corrosion of steels.The corrosion of the steel by production water is CO2/H2S corrosion.The synthesized quaternary ammonium salt inhibitor is a mixed inhibitor mainly inhibiting cathodic reaction,its adsorption behavior on the steel surface conforms to Langmuir adsorption isotherm,and the Gibbs free energy is negative,indicating that the adsorption process is spontaneous.By forming a protective film on the steel surface,the corrosion inhibitor isolates the contact between the corrosion medium and the steels,which can effectively restrain the corrosion and ensure the safety of the pipe during the water reinjection development in the offshore oil field.
offshore oil fieldproduction water reinjectioncorrosioncorrosion inhibition
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