Research On Anti-corrosion And Anti-scaling Of CO₂ Flooding And Conveying System

CO₂ flooding technology is one of the measures to improve oil recovery.It is widely used in major oil fields because of its strong diffusibility and fluidity,relatively low viscosity and good solubility.However,in the process of CO₂ flooding and transportation,CO₂ is highly susceptible to temperature,pressure,metal ions,etc.,causing serious corrosion and scaling in oil pipes,gathering pipelines and oil production equipment,thereby reducing oil recovery.,affecting crude oil production.In this paper,the main synthetic raw materials such as oleic acid,dimer acid,diethylenetriamine,hydroxyethylethylenediamine,epichlorohydrin and benzyl chloride were selected.Xylene was used as a water-carrying agent and boric acid as a catalyst to synthesize four kinds of quaternary ammonium.The salt type corrosion inhibitor was evaluated and its corrosion inhibition performance was evaluated.The2-（3,3-ethylaminobenzylimidazolium）heptadecane chloride with good corrosion inhibition effect on CO₂ was screened and its synthesis conditions were selected.The oleic acid imidazoline quaternary ammonium salt corrosion inhibitor ZCBM with better corrosion inhibition effect on CO₂ was obtained by compounding with dispersant OP-10 and corrosion inhibitor synergist butynediol;HEDP was evaluated.The scale inhibition performance of 8 commonly used scale inhibitors such as BHMTPMPA,PESA,PBTCA,HPAA,PESP,TH164,TH-163,BHMTPMPA,PESA and PBTCA with better selection effect,and better scale inhibition performance.The composite scale inhibitor ADGJ;the anti-scaling agent（ADGJ）and the corrosion inhibitor（ZCBM）are compounded to obtain a multi-effect corrosion and scale inhibitor（ZCAD）capable of simultaneously inhibiting corrosion and scaling.The performance of corrosion and scale inhibitors was evaluated by static weight loss method and static scale inhibition method.The experimental results show that when the ZCAD addition amount is 300 mg·L^-1,the corrosion rate of N80 steel sheet in corrosive medium is 0.0682 mm·a^-1,the corrosion inhibition rate is 93.23%;when the ZCAD addition amount is 30 mg·L^-1,the scale inhibition rate of calcium carbonate scale is 98.20%.When the ZCAD addition amount is 60 mg·L^-1,the scale inhibition rate of sulfuric acid scale is 94.61%,and the ZCAD addition amount is 40 mg·L^-1,the scale inhibition rate of calcium sulfate scale is 96.87%.The mechanism of corrosion and scale inhibitor was speculated by electrochemical workstation（CS350 type）,which showed that the corrosion and scale inhibitor ZCAD is a mixed corrosion and scale inhibitor that controls both cathode and anode corrosion.The results of scanning electron microscopy showed that the surface of the test piece without corrosion inhibitor or corrosion inhibitor was more serious.After adding the corrosion and scale inhibitor ZCAD,the surface of the test piece was smooth and bright without corrosion marks.