High-temperature and high-pressure CO2 corrosion resistant corrosion inhibitor for oil well and preparation method thereof
By preparing a corrosion inhibitor system composed of double Mannich base quaternary ammonium salt and alkyl aromatic sulfonate, the existing corrosion inhibitors are easily coking and layered under high temperature and high pressure conditions, and efficiently suppressing CO2 corrosion in oil well pipelines is achieved.
Patent Information
- Application Number
- CN202410102292.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-24
- Publication Date
- 2025-07-25
AI Technical Summary
The existing corrosion inhibitors are prone to coking, delamination, and dispersing under high temperature and high pressure conditions, which cannot effectively alleviate the CO2 corrosion problem in oil well pipelines.
The corrosion inhibitor system consisting of a double Mannich base quaternary ammonium salt, alkyl aromatic sulfonate surfactant, dispersant and high-temperature scale inhibitor is used to improve the stability and high-temperature resistance of the corrosion inhibitor by forming a dense adsorption film and inhibiting charge transfer.
In the environment of high temperature and high pressure CO2, the corrosion inhibitor shows excellent corrosion inhibition performance, low corrosion rate, wide application range, and is suitable for oil wells corroded by high temperature and high pressure CO2.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of chemical engineering, and particularly relates to an oil well corrosion inhibitor resistant to high temperature and high pressure CO2 corrosion and a preparation method thereof. Background Technique
[0002] In oil and gas field exploitation, the number of times of using CO2 corrosion inhibitor for oil displacement and fracturing of oil wells increases year by year. While ensuring the improvement of oil recovery, the content of carbon dioxide corrosion inhibitor in the produced fluid (gas) after the measures is very high (more than 80%). And with the gradual development of exploration and development towards ultra-deep layers, a large number of ultra-high temperature and high pressure reservoirs have emerged, and the highest bottom hole temperature reaches above 160°C. The corrosion problem caused by high temperature, high pressure and high CO2 is becoming more and more serious.
[0003] At present, for the corrosion of oil and gas pipelines and downhole strings, the most commonly used method in major oil fields is to add corrosion inhibitors, which is both economical and effective and does not affect the normal production of oil fields. However, under high temperature conditions of 180 - 250°C, most of the existing corrosion inhibitors are prone to coking, delamination, poor dissolution and dispersion, and are not stable enough. Summary of the Invention
[0004] In order to solve the problems existing in the prior art, the present invention provides an oil well corrosion inhibitor resistant to high temperature and high pressure CO2 corrosion and a preparation method thereof. The prepared corrosion inhibitor has a significant corrosion inhibition effect on CO2 corrosion under high temperature, high pressure and high salinity conditions, and has a small dosage, a high corrosion inhibition rate, and is simple and convenient to use.
[0005] To achieve the above object, the present invention provides the following technical solution: An oil well corrosion inhibitor resistant to high temperature and high pressure CO2 corrosion, calculated by mass percentage, the raw materials include 20% - 30% of bis-Mannich base quaternary ammonium salt, 12% - 18% of high temperature surfactant, 10% - 15% of dispersant, 10% - 18% of high temperature scale inhibitor, and 20% - 35% of alcohol.
[0006] Further, the bis-Mannich base quaternary ammonium salt has the structure of formula (Ⅰ):
[0007]
[0008] Wherein -R is methyl, ethyl, benzyl. X is -Br, -Cl, -I.
[0009] Further, the high temperature surfactant is alkyl aromatic sulfonate, specifically alkyl toluene sulfonate.
[0010] Further, the main component of the dispersant is fatty alcohol polyoxyethylene ether.
[0011] Further, the alcohol is ethanol or any one of propanol, isopropanol, isobutanol, or a mixture of at least two of them.
[0012] Furthermore, by mass percentage, the high-temperature scale inhibitor is a copolymer of 30% 2-acrylamido-2-methylpropanesulfonic acid, 20% acrylic acid, 10% acrylamide, and 40% sodium hypophosphite.
[0013] The present invention also provides a preparation method for a corrosion inhibitor for oil wells resistant to high-temperature and high-pressure CO2 corrosion, and the specific steps are as follows:
[0014] S1: Add phenethylamine, furfural, and cyclopentanone to a solvent, adjust the pH value of the solution to acidic, and obtain a Mannich base.
[0015] S2: Mix and purify the Mannich base, formaldehyde, and acetone to obtain a bis-Mannich base.
[0016] S3: Mix the bis-Mannich base with a solvent to obtain a bis-Mannich base solution. Under the condition of 100°C to 120°C, add a haloalkane to the bis-Mannich base solution to obtain a bis-Mannich base quaternary ammonium salt.
[0017] S4: Mix the bis-Mannich base quaternary ammonium salt, a high-temperature surfactant, a dispersant, a high-temperature scale inhibitor, and an alcohol to obtain a corrosion inhibitor for oil wells.
[0018] Furthermore, in S1, phenethylamine, furfural, and cyclopentanone are added to the solvent according to a mass ratio of 1:1.3 to 1.5:2 to 3, the pH value of the solution is adjusted to 2 to 4, and the reaction is stirred at 85°C to 90°C for 5 h to 7 h to obtain a Mannich base.
[0019] Furthermore, in S2, the Mannich base, formaldehyde, and acetone are mixed according to a mass ratio of 1:1.2 to 1.4:2 to 3, reacted at 85°C to 90°C for 3 to 6 h, and purified by vacuum distillation to generate a bis-Mannich base.
[0020] Furthermore, in S3, the solvent is N,N-dimethylformamide. Mix the bis-Mannich base with N,N-dimethylformamide to obtain a bis-Mannich base solution. Under the condition of 100°C to 120°C, add a haloalkane to the bis-Mannich base solution, stir and reflux for 5 h to 7 h, and distill off the solvent to obtain a bis-Mannich base quaternary ammonium salt.
[0021] Compared with the prior art, the present invention has at least the following beneficial effects:
[0022] The present invention provides an inhibitor for oil wells against high-temperature and high-pressure CO2 corrosion. Aiming at the actual working conditions in oil and gas fields or industries, a bis-Mannich base quaternary ammonium salt complex is used as the main agent. The N and O atoms in the bis-Mannich base have strong nucleophilicity, and the benzene ring containing a large π bond can coordinate with the 3d empty orbitals on the Fe atom in the metal to form a dense adsorption film, enhancing the high stability and high-temperature resistance of the inhibitor. On the other hand, the alkyl long chain and benzene ring of the bis-Mannich base have steric hindrance and certain hydrophobicity, blocking the transfer of charges or substances related to corrosion and effectively inhibiting metal corrosion. Its preparation raw materials are easily available, the preparation process is simple, and it has good compatibility, which can effectively reduce the corrosion of oil pipes under high-temperature and high-content CO2 conditions.
[0023] The bis-Mannich base quaternary ammonium salt, alkyl aromatic sulfonate surfactant, dispersant, etc. used in the inhibitor of the present invention have stable performance under high-temperature conditions. The maximum use temperature of the inhibitor reaches 160 °C, and it is stable in a strong acidic environment, suitable for the downhole working conditions of oil wells.
[0024] Furthermore, the bis-Mannich base quaternary ammonium salt and alkyl aromatic sulfonate used in the inhibitor of the present invention have a good synergistic effect and have very excellent corrosion inhibition performance under high-temperature and high-pressure CO2 conditions.
[0025] Furthermore, the fatty alcohol polyoxyethylene ether used in the inhibitor of the present invention can form a film at the oil-water interface to reduce its surface tension, so it has good dispersion performance.
[0026] Furthermore, the copolymer of 30% 2-acrylamido-2-methylpropanesulfonic acid, 20% acrylic acid, 10% acrylamide, and 40% sodium hypophosphite, which is a high-temperature scale inhibitor used in the inhibitor of the present invention, can inhibit the deposition of inorganic salts on the metal surface in a high-temperature environment, making it easier for the inhibitor film to adsorb.
[0027] Furthermore, the inhibitor for oil wells against high-temperature and high-pressure CO2 prepared by the present invention is suitable for working conditions where the CO2 partial pressure ranges from 1.0 to 5.0 MPa and the temperature ranges from 100 to 160 °C, and has the advantages of less dosage, good corrosion inhibition effect, and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a schematic diagram of the reaction mechanism of the bis-Mannich base quaternary ammonium salt. DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention will be further described below in conjunction with the drawings and specific embodiments.
[0030] The present invention provides a corrosion inhibitor for oil wells resistant to high temperature, high pressure CO2 corrosion. By mass percentage, it includes 20% - 30% of bis-Mannich base quaternary ammonium salt, 12% - 18% of high temperature surfactant, 10 - 15% of dispersant, 10% - 18% of high temperature scale inhibitor, and 20% - 35% of alcohol.
[0031] Among them, as Figure 1 shown, the preparation method of the bis-Mannich base quaternary ammonium salt is as follows:
[0032] S1: Add phenylethylamine, furfural, and cyclopentanone to the solvent in a mass ratio of 1:1.3 - 1.5:2 - 3, and drop 20% (mass fraction) HCl to adjust the pH value of the solution to 2 - 4. React and stir at 85°C - 90°C for 5h - 7h to obtain Mannich base;
[0033] S2: Then mix the Mannich base obtained in S1, formaldehyde, and acetone in a mass ratio of 1:1.2 - 1.4:2 - 3, react at 85°C - 90°C for 3 - 6h, and carry out vacuum distillation for purification to generate bis-Mannich base.
[0034] S3: Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add alkyl halide to the bis-Mannich base under the condition of 100°C - 120°C, stir and reflux for 5 - 7h, and distill off the solvent to obtain bis-Mannich base quaternary ammonium salt;
[0035] Among them, the preparation method of the corrosion inhibitor for oil wells resistant to high temperature, high pressure CO2 corrosion of the present invention is as follows:
[0036] Mix the bis-Mannich base quaternary ammonium salt, high temperature surfactant, dispersant, high temperature scale inhibitor, and alcohol according to the above mass fraction requirements, and stir at room temperature for 1 - 2h to obtain a corrosion inhibitor for oil wells.
[0037] Among them, the high temperature surfactant is alkyl aromatic sulfonate, specifically alkyl toluene sulfonate.
[0038] Among them, the main component of the dispersant is fatty alcohol polyoxyethylene ether, which consists of two parts: a hydrophilic group and a hydrophobic group.
[0039] Among them, the high temperature scale inhibitor is a copolymer of 30% 2-acrylamido-2-methylpropanesulfonic acid, 20% acrylic acid, 10% acrylamide, and 40% sodium hypophosphite.
[0040] Among them, the alcohol is ethanol or any one of propanol, isopropanol, and isobutanol, or a mixture of at least two of them.
[0041] The above percentages are all mass percentages.
[0042] Example 1
[0043] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.3:2, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 2, react and stir at 85 °C for 5 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.2:2, react and stir at 85 °C for 3 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 100 °C, stir and reflux for 5 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0044] The corrosion inhibitor is composed of the following components by weight percentage: 30% bis-Mannich base quaternary ammonium salt, 15% alkyl toluene sulfonate, 10% dispersant, 15% high-temperature scale inhibitor, and 30% ethanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0731 mm / a.
[0045] Example 2
[0046] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.5:3, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 4, react and stir at 85 °C for 5 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.4:3, react and stir at 85 °C for 3 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 100 °C, stir and reflux for 5 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0047] The corrosion inhibitor is composed of the following components by weight percentage: 30% bis-Mannich base quaternary ammonium salt, 15% alkyl toluene sulfonate, 10% dispersant, 15% high-temperature scale inhibitor, and 30% ethanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0825 mm / a.
[0048] Example 3
[0049] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.3:2, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 2, react and stir at 90 °C for 6 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.2:2, react and stir at 90 °C for 5 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 120 °C, stir and reflux for 6 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0050] The corrosion inhibitor is composed of the following components by weight percentage: 30% bis-Mannich base quaternary ammonium salt, 15% alkyl toluene sulfonate, 10% dispersant, 15% high-temperature scale inhibitor, and 30% ethanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0791 mm / a.
[0051] Example 4
[0052] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.4:2.5, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 3, react and stir at 90 °C for 6 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.3:2.5, react and stir at 90 °C for 5 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 110 °C, stir and reflux for 6 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0053] The corrosion inhibitor is composed of the following components by weight percentage: 25% bis-Mannich base quaternary ammonium salt, 15% alkyl toluene sulfonate, 15% dispersant, 15% high-temperature scale inhibitor, and 30% ethanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0846 mm / a.
[0054] Example 5
[0055] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.5:2, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 4, react and stir at 85 °C for 7 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.4:2, react and stir at 85 °C for 6 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 100 °C, stir and reflux for 7 h, distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0056] The corrosion inhibitor is composed of the following components by weight percentage: 20% bis-Mannich base quaternary ammonium salt, 15% alkyl toluene sulfonate, 15% dispersant, 15% high-temperature scale inhibitor, and 35% isopropanol and propanol mixture. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0783 mm / a.
[0057] Example 6
[0058] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.3:3, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 2, react and stir at 90 °C for 5 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.2:3, react and stir at 90 °C for 3 h for purification by vacuum distillation to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 120 °C, stir and reflux for 5 h, distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0059] The corrosion inhibitor is composed of the following components by weight percentage: 25% bis-Mannich base quaternary ammonium salt, 18% alkyl toluene sulfonate, 12% dispersant, 10% high-temperature scale inhibitor, and 35% propanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0803 mm / a.
[0060] Example 7
[0061] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.3:2, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 4, react and stir at 85°C for 7 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.2:2, react and stir at 85°C for 5 h, and carry out vacuum distillation for purification to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 100°C, stir and reflux for 6 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0062] The corrosion inhibitor is composed of the following components by weight percentage: 28% bis-Mannich base quaternary ammonium salt, 12% alkyl toluene sulfonate, 10% dispersant, 18% high-temperature scale inhibitor, and 32% isobutanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0867 mm / a.
[0063] Example 8
[0064] The preparation method of the bis-Mannich base quaternary ammonium salt is as follows: Add phenethylamine, furfural, and cyclopentanone into a solvent according to a mass ratio of 1:1.3:2, dropwise add 20% (mass fraction) HCl to adjust the pH value of the solution to 4, react and stir at 85°C for 7 h to obtain the Mannich base; then mix the obtained Mannich base, formaldehyde, and acetone according to a mass ratio of 1:1.2:2, react and stir at 85°C for 5 h, and carry out vacuum distillation for purification to generate the bis-Mannich base. Place the bis-Mannich base in a synthesis device, use an appropriate amount of N,N-dimethylformamide as the solvent, add an alkyl halide to the bis-Mannich base at 100°C, stir and reflux for 6 h, and distill off the solvent to obtain the bis-Mannich base quaternary ammonium salt.
[0065] The corrosion inhibitor is composed of the following components by weight percentage: 30% bis-Mannich base quaternary ammonium salt, 18% alkyl toluene sulfonate, 14% dispersant, 18% high-temperature scale inhibitor, and 20% isopropanol. The corrosion inhibitor of this formulation has good water solubility in the test medium, and the corrosion rate is 0.0705 mm / a.
[0066] Comparative Example 1:
[0067] The components of the corrosion inhibitor are 30% bis-Mannich base quaternary ammonium salt, 20% alkyl toluene sulfonate, 20% dispersant, 30% ethanol, and the corrosion rate is 0.1763 mm / a. The bis-Mannich base quaternary ammonium salt is prepared in Example 1.
[0068] Comparative Example 2:
[0069] The corrosion inhibitor consists of the following components by weight percentage: 30% Mannich base quaternary ammonium salt (Formula II), 15% alkyl toluene sulfonate, 10% dispersant, 15% high-temperature scale inhibitor, and 30% ethanol, with a corrosion rate of 0.1946 mm / a.
[0070]
[0071] Comparative Example 3:
[0072] The components of the corrosion inhibitor are 30% bis-Mannich base quaternary ammonium salt, 20% dispersant, 20% high-temperature scale inhibitor, and 30% ethanol, with a corrosion rate of 0.1599 mm / a. The bis-Mannich base quaternary ammonium salt is prepared as in Example 1.
[0073] Comparing the above examples with the comparative examples, it can be seen that the corrosion inhibitor prepared by the present invention has good water solubility and low corrosion rate in the test medium, and can effectively inhibit the corrosion of oil well pipes in a high-temperature and high-pressure CO2 environment.
[0074] The measurement conditions for the corrosion rate of the oil well corrosion inhibitor obtained in the examples of the present invention are as follows:
[0075] Prepare simulated water: 100000 mg / L NaCl, 5000 mg / L MgCl2·6H2O, 3000 mg / L Na2SO4, 5000 mg / L CaCl2, 500 mg / L NaHCO3.
[0076] Total pressure: 20 MPa; CO2 partial pressure: 5 MPa; test temperature: 160 °C; test time: 96 h; test material: N80 steel; corrosion inhibitor dosage: 300 mg / L.
[0077] During the test, first polish the N80 steel until it is shiny, then clean and dry it with petroleum ether and ethanol, weigh it. Put the weighed steel sheet into the autoclave, seal it and remove oxygen for 2 h. Pass in the deoxygenated simulated water and add 300 ppm corrosion inhibitor, stir evenly, heat up to 160 °C, pass in high-purity CO2 and maintain the CO2 pressure at 5 MPa, pass in high-purity N2 and maintain the N2 pressure at 20 MPa. After stabilizing for 96 h under this condition, take out the specimen, remove the corrosion product film on the surface of the specimen, dry it and weigh it, and calculate the corrosion rate.
Claims
1. An inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion, characterized in that, By mass percentage, the raw materials include 20% - 30% of double Mannich base quaternary ammonium salt, 12% - 18% of high-temperature surfactant, 10% - 15% of dispersant, 10% - 18% of high-temperature scale inhibitor, and 20% - 35% of alcohol.
2. An inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion according to claim 1, characterized in that, The double Mannich base quaternary ammonium salt has the structure of formula (Ⅰ): where -R is methyl, ethyl, benzyl; X is -Br, -Cl, -I.
3. An inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion according to claim 1, characterized in that, The high-temperature surfactant is alkyl aromatic sulfonate, specifically alkyl toluene sulfonate.
4. An inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion according to claim 1, characterized in that, The main component of the dispersant is fatty alcohol polyoxyethylene ether.
5. An inhibitor for oil wells against high-temperature and high-pressure CO2 corrosion according to claim 1, characterized in that, The alcohol is ethanol or any one of propanol, isopropanol, isobutanol, or a mixture of at least two of them.
6. An inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion according to claim 1, characterized in that, By mass percentage, the high-temperature scale inhibitor is a copolymer of 30% 2-acrylamido-2-methylpropanesulfonic acid, 20% acrylic acid, 10% acrylamide, and 40% sodium hypophosphite.
7. A preparation method of an inhibitor for oil wells resistant to high-temperature and high-pressure CO2 corrosion according to any one of claims 1 to 6, characterized in that, The specific steps are as follows: S1: Add phenethylamine, furfural, and cyclopentanone into a solvent, adjust the pH value of the solution to acidic, and obtain Mannich base. S2: Mix and purify Mannich base, formaldehyde, and acetone to obtain double Mannich base. S3: Mix the double Mannich base with a solvent to obtain a double Mannich base solution. Under the condition of 100°C - 120°C, add haloalkane to the double Mannich base solution to obtain double Mannich base quaternary ammonium salt. S4: Mix the double Mannich base quaternary ammonium salt, high-temperature surfactant, dispersant, high-temperature scale inhibitor, and alcohol to obtain an oil well corrosion inhibitor.
8. The preparation method of an anti-high temperature and high pressure CO2 corrosion inhibitor for oil wells according to claim 7, characterized in that, In S1, add phenethylamine, furfural, and cyclopentanone into a solvent according to the mass ratio of 1:1.3 - 1.5:2 - 3, adjust the pH value of the solution to 2 - 4, react and stir at 85°C - 90°C for 5h - 7h to obtain Mannich base.
9. The preparation method of an inhibitor for oil wells resistant to high temperature and high pressure CO2 corrosion according to claim 7, characterized in that, In S2, mix Mannich base, formaldehyde, and acetone according to the mass ratio of 1:1.2 - 1.4:2 - 3, react at 85°C - 90°C for 3 - 6h, and carry out vacuum distillation for purification to generate double Mannich base.
10. The preparation method of a corrosion inhibitor for oil wells resistant to high-temperature and high-pressure CO2 corrosion according to claim 7, characterized in that, In S3, the solvent is N,N-dimethylformamide. Mix the double Mannich base with N,N-dimethylformamide to obtain a double Mannich base solution. Under the condition of 100°C - 120°C, add haloalkane to the double Mannich base solution, stir and reflux for 5h - 7h, and distill off the solvent to obtain double Mannich base quaternary ammonium salt.