Development And Performance Evaluation Of A Corrosion And Scale Inhibitor (system) Suitable For CO₂ Flooding

CO2 flooding is a measure to improve the recovery of oil and gas.Its advantages are obvious,but its disadvantages are also very serious.It will cause serious corrosion and scaling.Therefore,we must solve the problem of corrosion and scaling caused by CO2 flooding and ensure the smooth operation of CO2 flooding.In view of the corrosion and scaling problem of CO2 flooding,the corresponding inhibitors and scale inhibitors were designed and synthesized,and the inhibitors with good corrosion inhibition and good scale inhibition effect were mixed,and a kind of corrosion inhibitor which was suitable for solving the corrosion and scaling problem of CO2 flooding was developed.According to the molecular design principle,a series of inhibitors(EFA,EGA,DGA)and two kinds of three scale copolymer scale inhibitors m-PAEA and c-PAMEA were synthesized.A good corrosion inhibitor DGA,an excellent scale inhibitor c-PAMEA and a kind of corrosion and scale inhibitor m-PAEA with good corrosion resistance and scale inhibition were selected.Mannich base EFA was synthesized from furfural,ethylenediamine and acetophenone.The water soluble corrosion inhibitor EFA was obtained by the reaction of formaldehyde and Sodium Bisulfite to EFA methanesulfylation.When the temperature is 90,the EFA dosage is 400mg/L,the corrosion rate is 86.9%,and the corrosion rate is 0.071mm/a.But the yield was low,so the scheme was abandoned.The corrosion inhibitor EGA was synthesized with glucose,ethylenediamine and acetophenone.When the temperature was 80 C and the amount was 600 mg/L,the corrosion rate of the N80 steel sheet was 0.093 mm/a,and the pitting and uniform corrosion were serious.The corrosion rate of the N80 steel sheet was 0.073 mm/a when EGA was added to 1000 mg/L.The corrosion inhibitor is larger,so it is abandoned.A synthetic inhibitor DGA was designed with two ethylene three amine,glucose and acetophenone as raw materials.When the temperature was 80,and DGA was 400 mg/L,the corrosion rate was 0.046mm/a and the corrosion inhibition rate reached 89.4%.The anticorrosion target was achieved,and the corrosion inhibition performance was excellent.Finally,DGA was selected as the final research object.The electrochemical experiments show that the corrosion inhibitor DGA is a kind of mixed inhibitor which mainly inhibits the cathode.It can adsorb the corrosion inhibitor film on the surface of N80 and inhibit the corrosion of metal effectively.A kind of corrosion inhibitor m-PAEA,which has both corrosion inhibition and scale inhibition,was obtained by using formaldehyde and acetophenone to modify the three element copolymer AM/MA/AMPS,and the scale inhibition and corrosion inhibition performance were evaluated.When the temperature is 70,and the amount of m-PAEA is 200mg/L,the scale inhibition rate of CaCO3 scale and BaSO4 scale is 94%and 73.1%,respectively.When the addition amount is 600mg/L,the corrosion inhibition rate is 88.8%.Acrylic acid,maleic anhydride and 2-acrylamide based-2-methyl propane sulfonic acid(AMPS)were copolymerized,and the number of carboxyl groups of chelating group was increased by citric acid modification,and the copolymer scale inhibitor c-PAMEA was obtained.When the temperature is 70 c-PAMEA and the dosage of 20mg/L is 20mg/L,the scale inhibition rate of calcium carbonate and barium sulfate can reach 97.3%and 91.8%respectively.A combination of inhibitor DGA and scale inhibitor c-PAMEA was used to evaluate its compatibility.A corrosion inhibitor scale inhibitor MDP suitable for CO2 flooding was screened out.The inhibitor DGA has good compatibility with scale inhibitor c-PAMEA and has synergistic effect.The optimum dosage of MDP is DGA400 mg/L and c-PAMEA 20 mg/L.Under the condition of 90 degree temperature,the scale inhibition rate of calcium carbonate is 88.5%,and the corrosion inhibition rate can reach 88.9%.The scale inhibition and corrosion inhibition mechanism of the synthesized corrosion and scale inhibitor were discussed by SEM,EDS and XRD tests.The copper ion replacement experiment and SEM and EDS analysis show that there is a certain N element on the surface of the steel sheet,indicating that the corrosion inhibitor is mainly formed by the combination of the solitary pair of electrons of N and O atoms with the iron's empty orbit,forming an effective corrosion inhibitor protection film to avoid direct exposure of metal to corrosion medials.SEM and XRD experiments show that the scale of scale crystals with the addition of scale inhibitor is obviously distorted,and the scale crystals which are loose and easy to be washed away easily and easily can be washed away from the dense regular crystal,it avoids the blockage of oil Wells and pipelines.