Study On Water Quality Characteristic And Corrosion Law Of CO₂ Flooding Response Wells In Jiyuan Oilfield

Aiming at serious corrosion problem of downhole casing in response well of CO₂ flooding in Huang 3 well area of Jiyuan Oilfield.In the paper,the corrosion mechanism and anti-corrosion measures are studied.The first of all,determination of ingredients and concentration of produced water from oil wells in different periods by interior titration experiment,the basic water quality characteristics of produced water in the area are obtained,the main mechanism of steel corrosion caused by produced water from CO₂ flooding wells is clarified,and the corrosion rate of steel is measured.The results show that CO₂ and dissolved oxygen are the main corrosion factors,and Cl^-concentration and salinity in produced water of individual oil wells are higher.Secondly,the effects of time,temperature and pressure on Corrosion of metal steel were studied.The results show that when CO₂ is continuously injected,the longer the injection time is,the higher the corrosion rate of metals is;when the temperature increases,the corrosion rate of metals increases first and then decreases;and when the partial pressure of CO₂ increases,the corrosion rate of metals also increases.At the same time,based on the calculation software of MATLAB,the prediction model of CO₂ corrosion was established by using grey correlation analysis and BP neural network.The results show that the p H of the extracted water has the greatest influence on the corrosion rate of steel,the influence of Cl^-concentration and salinity of the extracted water on the corrosion rate of steel increases with the increase of CO₂ injection time,the error between the predicted results of BP neural network and the measured values was small.Fanally,five different types of steel（316L steel,5Cr steel,20# steel,304 steel and N80 steel）were selected to test the corrosion rate of the metal in the produced water of CO₂ flooding wells,and the corrosion inhibition effect of the adsorptive corrosion inhibitor was evaluated by electrochemical method.The results show that the current density in solution decreases greatly and the anode slope increases considerably after adding the adsorption inhibitor,which indicates that the inhibitor has good corrosion inhibition effect and 304 steel and 5Cr steel have good corrosion resistance.The research results in this paper can provide reference and suggestions for the corrosion of steel in the produced water of CO₂ flooding response wells in Huang 3 well area of Jiyuan Oilfield.