Compounding experimental study on corrosion and scale inhibitor of CO₂ flooding well

In view of the characteristics of corrosion and scaling of CO₂ flooding in an oilfield in the western part of the country, imidazoline, quaternary ammonium salt, amide salt, phosphonate inhibitors and amino trimethylene phosphonic acid, poly-aspartic acid scale inhibitors used in oil field were chosen, then the compounding experimental studies were proceeded. The electrochemical test method and the static scale inhibition test experiment were used to select the good corrosion inhibitor and single agent for the scale inhibitor. The compounding agent was used for the optimal concentration test at the total concentration of 240 mg/L. The protective effect of the composite corrosion and scale inhibitor was evaluated by weight loss method, the scale ratio of the simulated condition, and the scanning electron microscope (SEM). The experimental results showed that: the corrosion inhibition rate of corrosion inhibitor and scale inhibitor obtained by single-agent screening in saturated CO₂ simulated formation water at 60 ℃ was as high as 94.13% for the N80 carbon steel, and the scale inhibition rate was as high as 93.98%. When the inhibitor and scale inhibitor were compounded in a ratio of 2:1, the total concentration was 240 mg/L, the corrosion inhibition rate was 91.98%, and the scale inhibition rate was 91.1%. In the simulation of the most demanding production condition, the effect of anti-corrosion and anti-scaling of the composite corrosion and scale inhibitor could meet the oil field control indicators. Studies showed that the combination of phosphonate and poly-aspartic acid corrosion and scale inhibitor could inhibit the corrosion and scaling of CO₂ flooding wells.