Annular protection fluid corrosion inhibitor for oil and gas well as well as preparation method and application of annular protection fluid corrosion inhibitor

Abstract

The invention relates to the technical field of oil and gas field corrosion and protection, in particular to an annulus protection fluid corrosion inhibitor for an oil and gas well and a preparation method and application thereof. The annulus protection liquid corrosion inhibitor for the oil and gas well is prepared by mixing the following raw materials in parts by weight: 20-30 parts of a bis Mannich base azine azole corrosion inhibitor main agent, 5-8 parts of a surfactant, 5-8 parts of a scale inhibitor, 30-40 parts of an organic solvent and 14-40 parts of water, the main agent of the bis-Mannich base azine azole corrosion inhibitor has a structural formula as shown in the following formula (I). According to the invention, a compound containing a triazine ring, an imidazole ring and a bis-mannich base structure is mainly used as a main agent of the bis-mannich base triazol corrosion inhibitor, and the main agent of the bis-mannich base triazol corrosion inhibitor is matched with other components, so that the uniform adsorption of the annulus protection liquid corrosion inhibitor for the oil and gas well on a metal surface is improved; and the corrosion inhibition effect is prevented from being influenced by the action with other additives of the annulus protection liquid in a corrosive medium.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field corrosion and protection, in particular to an annulus protection fluid corrosion inhibitor for oil and gas wells and a preparation method and application thereof. BACKGROUND

[0002] The main role of the annulus protection fluid is to slow down the corrosion of the oil casing, reduce the reservoir pressure borne by the casing head or the packer, and reduce the pressure difference between the oil pipe and the annulus. By adding corrosion inhibitors, bactericides, oxygen scavengers and other additives to the annulus protection fluid, the corrosion of the oil casing can be effectively inhibited, which is the most widely used oil casing annulus protection technology at present.

[0003] For the problem of oil casing annulus corrosion, the most commonly used corrosion inhibitor is imidazoline and its derivatives. This kind of corrosion inhibitor has good adsorption performance and can form a firm protective film on the metal surface, and has good corrosion inhibition effect on various corrosion media, especially strong acid media such as hydrochloric acid and sulfuric acid. However, most imidazoline corrosion inhibitors have poor temperature resistance, which leads to a decrease in corrosion inhibition efficiency. For example, in the patent application CN116554940A, a kind of imidazole amide corrosion inhibitor is prepared by reacting neodecanoic acid and diethylene triamine, and thiourea is added as a synergist. The thiourea has poor temperature resistance under high temperature conditions, and the prepared corrosion inhibition performance will decrease when the temperature is high. Literature 1: Li Jiyong, Oilfield Chemistry, Vol. 38, No. 1. In literature 1, in order to improve the temperature resistance of imidazoline, thiourea-based imidazoline quaternary ammonium salt is obtained by reacting thiourea with imidazoline medium, but only the corrosion inhibition effect at 90℃ is investigated. SUMMARY

[0004] In order to solve the problem of poor temperature resistance of existing imidazoline corrosion inhibitors, which leads to a decrease in corrosion inhibition efficiency, the present application provides an annulus protection fluid corrosion inhibitor for oil and gas wells and a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows.

[0006] The present application provides an annulus protection fluid corrosion inhibitor for oil and gas wells, which is prepared by mixing the following raw materials by weight: 30 parts of double Mannich base zineazole corrosion inhibitor main agent, 5-8 parts of surfactant, 5-8 parts of scale inhibitor, 30-40 parts of organic solvent and 14-30 parts of water; the double Mannich base zineazole corrosion inhibitor main agent has the following structural formula as shown in formula (I): ; Wherein, the value range of n is 1-4.

[0007] The present application mainly uses a compound containing a triazine ring, an imidazole ring and a double Mannich base structure as a double Mannich base triazole corrosion inhibitor main agent.

[0008] The present application improves the uniform adsorption of the annulus protection fluid corrosion inhibitor for oil and gas wells on the metal surface by the cooperation of the double Mannich base triazole corrosion inhibitor main agent and other components, and avoids the influence of the corrosion effect caused by the reaction of the double Mannich base triazole corrosion inhibitor main agent with other additives of the annulus protection fluid in the corrosion medium.

[0009] The surfactant added in the present application can further improve the solubility and dispersibility of the double Mannich base triazole corrosion inhibitor main agent in water, so that the double Mannich base triazole corrosion inhibitor main agent can uniformly form a film on the metal surface; the scale inhibitor can clean the metal surface, effectively inhibit the deposition of inorganic scale on the metal surface, ensure the uniform adsorption of the corrosion inhibitor, and avoid the occurrence of under-deposit corrosion.

[0010] Preferably, the surfactant is at least one of an alkylphenol polyoxyethylene ether and a fatty alcohol polyoxyethylene ether. The surfactant used in the present application has good stability, strong adsorption film forming capacity, and can play a synergistic role with the corrosion inhibitor, is not affected by the pH of the solution, and has stable performance.

[0011] Preferably, the scale inhibitor is a mixture of polyepoxysuccinic acid and AA-AMPA-HPA terpolymer; the mass ratio of polyepoxysuccinic acid and AA-AMPA-HPA terpolymer is 3:6-7; the AA-AMPA-HPA terpolymer is obtained by a free radical polymerization reaction with acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate as monomers, the mass ratio of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate is 3:2:7, and the molecular weight of the AA-AMPA-HPA terpolymer is 2000-3000. The scale inhibitor used in the present application is resistant to high temperature and oxidation, and has good compatibility with the corrosion inhibitor.

[0012] Preferably, the organic solvent is at least one of N,N-dimethylformamide, methanol and ethanol.

[0013] The second aspect of the present application provides a preparation method of the annulus protection fluid corrosion inhibitor for oil and gas wells described in the first aspect, which comprises the following steps: The double Mannich base triazole corrosion inhibitor main agent, the surfactant, the scale inhibitor, the organic solvent and water are stirred and mixed to obtain the annulus protection fluid corrosion inhibitor for oil and gas wells.

[0014] Preferably, the preparation method of the double Mannich base triazine corrosion inhibitor main agent comprises the following steps: The melamine and chloroacetic acid are reacted under the action of an alkali solution at 80-90 DEG C, after the reaction is completed, the pH is adjusted to 1-2, and water is removed by evaporation to obtain a first intermediate product shown in formula (1).

[0015] The first intermediate product shown in formula (1) and the polyethylene polyamine shown in formula (2) are reacted under a first solvent system at 150-160 DEG C, then the reaction is continued under vacuum at 210-220 DEG C, and the first solvent is removed by evaporation to obtain a second intermediate product shown in formula (3).

[0016] The second intermediate product shown in formula (3), formaldehyde and phenylacetone are reacted under a second solvent system at 70-80 DEG C, and the second solvent is removed by evaporation to obtain the double Mannich base triazine corrosion inhibitor main agent.

[0017] ; Wherein, n=1-4.

[0018] The present application mainly uses melamine as raw material, generates a first intermediate product after modification by chloroacetic acid, reacts the first intermediate product with amine to generate an imidazoline ring, and then reacts with aldehyde and ketone to generate a double Mannich base corrosion inhibitor main agent containing a triazine ring and an imidazoline ring.

[0019] The double Mannich base corrosion inhibitor main agent contains an imidazoline ring and a Mannich structure, has multiple adsorption points, can be closely adsorbed with metal, and forms a hydrophobic film due to the benzene ring group, effectively isolates the contact between the metal layer and the corrosion medium, and effectively protects the metal.

[0020] Preferably, the mass ratio of melamine and chloroacetic acid is 1:1-1.2; the alkali solution is obtained by mixing an inorganic alkali and water; and the mass ratio of melamine and inorganic alkali is 5:4-5.

[0021] Further preferably, the inorganic alkali is sodium hydroxide, and the concentration of the inorganic alkali solution is 40wt%.

[0022] Preferably, the mass ratio of the first intermediate product shown in formula (1) and the polyethylene polyamine shown in formula (2) is 1:2-2.5; and the first solvent is N,N-dimethylformamide or dimethylbenzene.

[0023] Preferably, the mass ratio of the second intermediate product shown in formula (3), formaldehyde and phenylacetone is 4:1-1.2:4-4.2; the second solvent is N,N-dimethylformamide or ethanol.

[0024] The third aspect of the present application provides an application of the annulus protection fluid corrosion inhibitor for oil and gas well as a composite corrosion inhibitor for preparing the annulus protection fluid for oil and gas well, wherein the annulus protection fluid corrosion inhibitor for oil and gas well is the annulus protection fluid corrosion inhibitor for oil and gas well as described in the first aspect.

[0025] The annulus protection fluid corrosion inhibitor for oil and gas well of the present application can be widely applied to oxygen corrosion in the annulus environment of oil and gas well and high salinity water, and can effectively control the corrosion to the oil pipe and the casing by adding 1%-2% of the composite corrosion inhibitor in the annulus medium of oil and gas well, and has a high corrosion inhibition rate.

[0026] The beneficial effects of the present application are as follows: 1. The annulus protection fluid corrosion inhibitor for oil and gas well of the present application has good water solubility, and the present application mainly uses a compound containing triazine ring, imidazole ring and double Mannich base structure as a double Mannich base triazole corrosion inhibitor main agent. Since the double Mannich base triazole corrosion inhibitor main agent contains imidazole ring and Mannich structure, it has multiple adsorption points and can be closely adsorbed with metal, and the benzene ring group makes it form a hydrophobic film, effectively isolating the metal layer from the corrosion medium and effectively protecting the metal. Through the mutual cooperation of the double Mannich base triazole corrosion inhibitor main agent and other components, the uniform adsorption of the annulus protection fluid corrosion inhibitor for oil and gas well on the metal surface is improved, and the effect of the other additives in the corrosion medium on the annulus protection fluid is avoided to affect the corrosion inhibition effect.

[0027] 2. The present application can further improve the solubility and dispersibility of the double Mannich base triazole corrosion inhibitor main agent in water by adding a surfactant, so that it can uniformly form a film on the metal surface; by adding a scale inhibitor, the metal surface can be cleaned, the deposition of inorganic scale on the metal surface is effectively inhibited, the uniform adsorption of the corrosion inhibitor is ensured, and the occurrence of under-deposit corrosion is avoided. Through the mutual cooperation of the double Mannich base triazole corrosion inhibitor main agent, the surfactant and the scale inhibitor, the uniform adsorption of the annulus protection fluid corrosion inhibitor for oil and gas well on the metal surface is improved, and good temperature resistance and salt resistance are achieved.

[0028] 3. The annulus protection fluid corrosion inhibitor for oil and gas well of the present application can be widely applied to oxygen corrosion in the annulus environment of oil and gas well and high salinity water, and can effectively control the corrosion to the oil pipe and the casing, and has a high corrosion inhibition rate. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The infrared spectrum of the double Mannich base triazole corrosion inhibitor main agent prepared in Example 1. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0031] Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0032] The present application mainly prepares a composite corrosion inhibitor with stable performance, excellent corrosion inhibition performance and good temperature resistance and salt resistance by mixing the double Mannich base zaine corrosion inhibitor main agent with surfactant, scale inhibitor, organic solvent and water.

[0033] Wherein, the value range of n is 1-4.

[0034] The annulus protection fluid corrosion inhibitor for oil and gas wells has good water solubility. The double Mannich base zaine corrosion inhibitor main agent contains triazine ring and imidazole ring, and also contains double Mannich base structure, which can be closely adsorbed with metal and form a firm protective film on the metal surface, and has good corrosion inhibition effect on various corrosion media. The benzene ring structure can ensure the hydrophobicity of the protective film and effectively protect the metal. The present application expands the application range and improves the corrosion inhibition effect by the mutual cooperation of the components, and has good temperature resistance and salt resistance.

[0035] The present application adds scale inhibitor to ensure uniform adsorption of the annulus protection fluid corrosion inhibitor for oil and gas wells on the metal surface. The annulus protection fluid corrosion inhibitor for oil and gas wells can be widely used in oxygen corrosion in oil and gas well annulus environment and high salinity water, can effectively control the corrosion of oil pipe and casing, and has high corrosion inhibition rate.

[0036] The preparation method of the double Mannich base zaine corrosion inhibitor main agent comprises the following steps: Step 1, melamine and chloroacetic acid are reacted at 80-90 DEG C under the action of alkali solution, after the reaction is completed, the pH is adjusted to 1-2, and the water is removed by evaporation to obtain the first intermediate product shown in formula (1).

[0037]

[0038] In step 1, the alkali solution serves to neutralize the acidity of chloroacetic acid to generate sodium salt of chloroacetic acid, thereby promoting the reaction with melamine. The purpose of adjusting the pH is to neutralize the basic substances in the reaction system and promote the precipitation of the product. ​​

[0039] Step 2, the first intermediate product shown in formula (1) and polyethylene polyamine shown in formula (2) are subjected to amidation reaction under a first solvent system at 150-160°C, then subjected to cyclization reaction under vacuum condition at 210-220°C, and evaporated to remove the first solvent, to obtain the second intermediate product shown in formula (3). The vacuum degree is 10-20 kPa.

[0040] .

[0041] Step 3, the second intermediate product shown in formula (3), formaldehyde and acetophenone are subjected to reaction under a second solvent system at 70-80°C, and evaporated to remove the second solvent, to obtain the bimannich base xiazole corrosion inhibitor main agent.

[0042] .

[0043] The technical solutions of the present application are further described below through specific examples.

[0044] In each of the following examples, the method is a conventional method unless otherwise specified; and the reagents and materials are commercially available unless otherwise specified.

[0045] In each of the following examples, the AA-AMPA-HPA ternary polymer is obtained by free radical polymerization reaction with acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate as monomers, the mass ratio of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate is 3:2:7, and the molecular weight of the AA-AMPA-HPA ternary polymer is 2000-3000.

[0046] The molecular weight of the polyepoxysuccinic acid is 600.

[0047] The molecular weight of the alkylphenol polyoxyethylene ether is 800.

[0048] Example 1 An annulus protection fluid corrosion inhibitor for oil and gas wells is prepared by mixing the following raw materials by weight: 30 parts of bimannich base xiazole corrosion inhibitor main agent, 5 parts of surfactant, 8 parts of scale inhibitor, 30 parts of organic solvent and 27 parts of water.

[0049] The surfactant is alkylphenol polyoxyethylene ether. The scale inhibitor is a mixture of polyepoxysuccinic acid and AA-AMPA-HPA ternary polymer, and the mass ratio of polyepoxysuccinic acid to AA-AMPA-HPA ternary polymer is 3:7. The organic solvent is methanol.

[0050] The preparation method of the bimannich base xiazole corrosion inhibitor main agent is as follows: S1, add melamine 20 g, chloroacetic acid 20 g and 40 wt% sodium hydroxide solution 40 g into a flask, stir and react at 90℃ for 8-10 h, after the reaction is completed, add hydrochloric acid to adjust the pH of the solution to 1-2, evaporate the water to obtain the first intermediate product shown in formula (1).

[0051] S2, mix 20 g of the first intermediate product shown in formula (1) with 40 g of diethylenetriamine / n=2 shown in formula (2), add 60 g of N,N-dimethylformamide as a reaction solvent, react at 150℃ for 6 h, then vacuumize to 15 kPa and heat to 210℃, continue to react under vacuum for 6 h, cool down, and evaporate the solvent to obtain the second intermediate product shown in formula (3).

[0052] S3, mix 40 g of the second intermediate product shown in formula (3) with 10 g of formaldehyde and 40 g of phenylethanone, and add 90 g of N,N-dimethylformamide as a reaction solvent, react at 70℃ for 8 h, and evaporate the reaction solvent to obtain the double mannich base zine azole corrosion inhibitor main agent, n=2.

[0053] The preparation method of the annulus protection fluid corrosion inhibitor for oil and gas wells is as follows: After mixing 20 parts of the double mannich base zine azole corrosion inhibitor main agent, 5 parts of a surfactant, 5 parts of a scale inhibitor, 30 parts of an organic solvent and 40 parts of water, stirring at room temperature, the annulus protection fluid corrosion inhibitor for oil and gas wells is obtained.

[0054] Example 2 An annulus protection fluid corrosion inhibitor for oil and gas wells, which is different from example 1 in that the mixing ratio of each raw material is different, as shown in table 1.

[0055] Table 1: Mixing ratio of each raw material of the annulus protection fluid corrosion inhibitor for oil and gas wells in different examples Comparative example 1 An annulus protection fluid corrosion inhibitor for oil and gas wells, which is different from example 1 in that the double mannich base zine azole corrosion inhibitor main agent is replaced by an oleic acid imidazoline main agent. The annulus protection fluid corrosion inhibitor for oil and gas wells is prepared by mixing the following raw materials by weight:

[0056] Oleic acid imidazoline main agent 30 parts, surfactant 5 parts, scale inhibitor 8 parts, organic solvent 30 parts and water 27 parts. The chemical formula of the oleic acid imidazoline main agent is C 40 H 74 N2O2, and the molecular weight is 615.03.

[0057] Comparative example 2 An annulus protection fluid corrosion inhibitor for oil and gas well, which is different from Example 1 in that no surfactant is added. The annulus protection fluid corrosion inhibitor for oil and gas well is prepared by mixing the following raw materials in parts by weight:

[0058] The bimannich base triazine corrosion inhibitor base 30 parts, the scale inhibitor 8 parts, the organic solvent 30 parts and the water 27 parts.

[0059] Comparative Example 3 An annulus protection fluid corrosion inhibitor for oil and gas well, which is different from Example 1 in that no scale inhibitor is added. The annulus protection fluid corrosion inhibitor for oil and gas well is prepared by mixing the following raw materials in parts by weight:

[0060] The bimannich base triazine corrosion inhibitor base 30 parts, the surfactant 5 parts, the organic solvent 30 parts and the water 27 parts.

[0061] Test 1: Infrared spectrum detection.

[0062] The bimannich base triazine corrosion inhibitor base prepared in Example 1 is subjected to infrared spectrum detection, and the results are shown in Figure 1 .

[0063] From Figure 1 it can be seen that 3401 cm -1 and 3310 cm -1 are -NH2 stretching vibration absorption peaks, 1725 cm -1 is C=O stretching vibration, 1675 cm -1 is -NH2 N-H bond in-plane bending vibration absorption peak, 1570 cm -1 is imidazole ring skeleton vibration absorption peak, 1386 cm -1 is the stretching vibration absorption peak of C-N bond in triazine ring, 1452 cm -1 is benzene ring stretching vibration absorption peak, 1300 cm -1 is -NH- stretching vibration absorption peak. From the infrared spectrum, it can be determined that the bimannich base triazine corrosion inhibitor base is successfully synthesized, and its structural formula is shown as follows:

[0064] ; n=2.

[0065] Test 2: Corrosion performance evaluation.

[0066] The annulus protection fluid corrosion inhibitors for oil and gas well prepared in Examples 1-10 and Comparative Examples 1-3 are subjected to corrosion performance evaluation, and the results are shown in Tables 2 and 3.

[0067] The corrosion performance evaluation method is as follows: Reference standard: SY / T 5273-2000 Performance evaluation method of corrosion inhibitor for oilfield produced water, the corrosion inhibitor dosage is 1%.

[0068] The test temperature is 70℃ and 180℃; the test sample is N80 steel sample; the corrosion period is 7 days; the rotating speed is 100r / min; the total pressure is 5MPa; the carbon dioxide partial pressure is 3MPa; the hydrogen sulfide partial pressure is 2MPa; the simulated water is obtained by adding 5% NaCl, 0.4% CaCl2, 0.2% MgCl2·6H2O, 0.6% Na2SO4 and 0.04% NaHCO3 into distilled water.

[0069] Table 2: Evaluation results of corrosion inhibition rate at 70℃ Table 3: Evaluation results of corrosion inhibition rate at 180℃ Analysis of the results in Table 2 and Table 3: In Example 1 to Example 3, the influence of different scale inhibitor dosages on corrosion inhibition performance is compared under the condition of fixed surfactant and organic solvent dosage. It can be seen that the scale inhibitor dosage of 5 to 8 parts can ensure good corrosion inhibition effect, and the corrosion inhibition rate at 180℃ is more than 86% and the corrosion rate is less than 0.053mm / a when the scale inhibitor dosage is 5 to 7 parts.

[0070] In Example 4 to Example 6, the influence of different surfactants on corrosion inhibition performance is compared under the condition of fixed scale inhibitor and organic solvent dosage. It can be seen that the surfactant dosage of 5 to 8 parts can ensure good corrosion inhibition effect, and the corrosion inhibition rate at 180℃ is more than 85%.

[0071] In Example 7 to Example 9, the influence of different organic solvents on corrosion inhibition performance is compared under the condition of fixed scale inhibitor and surfactant dosage. The organic solvent of 30 to 40 parts can ensure good corrosion inhibition effect, and the corrosion inhibition rate at 180℃ is more than 85%.

[0072] Compared with Example 1, the corrosion inhibition rate at 70℃ and 180℃ of Comparative Example 1 using imidazoline oleate as the main agent is obviously lower, and the corrosion rate is obviously higher. In Comparative Example 2 to Comparative Example 3, the corrosion inhibition performance is affected without adding surfactant or scale inhibitor, among which the corrosion inhibition rate at 180℃ is about 82%, and the corrosion rate is greater than 0.06. Compared with Example 1, the corrosion inhibition rate at 70℃ and 180℃ of the corrosion inhibitor in Comparative Example 2 to Comparative Example 3 is obviously lower, and the corrosion rate is obviously higher.

[0073] The amount of the bimannich base xiazole corrosion inhibitor main agent is insufficient, and the corrosion inhibitor performance is affected.

[0074] In summary, the oil and gas well annulus protection fluid corrosion inhibitor has excellent corrosion inhibition performance at 70 DEG C, and still has good corrosion inhibition performance at 180 DEG C, which indicates that the oil and gas well annulus protection fluid corrosion inhibitor has good temperature resistance. The corrosion inhibition performance evaluation is carried out in a salt water system, and thus it is further proved that the oil and gas well annulus protection fluid corrosion inhibitor has good temperature resistance and salt resistance.

[0075] The above only is the preferred embodiment of the present application, and does not limit the present application, and any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A corrosion inhibitor for annular protection fluid in oil and gas wells, characterized in that, The corrosion inhibitor for the annulus protection fluid used in oil and gas wells is prepared by mixing the following raw materials in parts by weight: The mixture consists of 30 parts of the main component of the dimanisilazine alkali-based corrosion inhibitor, 5 to 8 parts of the surfactant, 5 to 8 parts of the scale inhibitor, 30 to 40 parts of the organic solvent, and 14 to 40 parts of water. The main component of the bismannich base-azinazole corrosion inhibitor has the following structural formula (I): ； The value of n ranges from 1 to 4.

2. The corrosion inhibitor for annular protection fluid in oil and gas wells according to claim 1, characterized in that, The surfactant is at least one of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

3. The corrosion inhibitor for annular protection fluid in oil and gas wells according to claim 1, characterized in that, The scale inhibitor is a mixture of polyepoxysuccinic acid and AA-AMPA-HPA terpolymer; wherein the mass ratio of polyepoxysuccinic acid and AA-AMPA-HPA terpolymer is 3:6 to 7; the AA-AMPA-HPA terpolymer is obtained by free radical polymerization of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate as monomers, the mass ratio of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate is 3:2:7, and the molecular weight of the AA-AMPA-HPA terpolymer is 2000 to 3000.

4. The corrosion inhibitor for annular protection fluid in oil and gas wells according to claim 1, characterized in that, The organic solvent is at least one of N,N-dimethylformamide, methanol, and ethanol.

5. A method for preparing the corrosion inhibitor for annular protective fluid in oil and gas wells according to any one of claims 1 to 4, characterized in that, Includes the following steps: The main component of the bismannich alkali-zinc azole corrosion inhibitor, surfactant, scale inhibitor, organic solvent and water are stirred and mixed to obtain the annulus protection fluid corrosion inhibitor for oil and gas wells.

6. The method for preparing the corrosion inhibitor for annular protection fluid in oil and gas wells according to claim 1, characterized in that, The preparation method of the main agent of the bismannich base-azinazole corrosion inhibitor includes the following steps: Melamine and chloroacetic acid were reacted in an alkaline solution at 80℃~90℃. After the reaction was completed, the pH was adjusted to 1~2 and the water was removed by evaporation to obtain the first intermediate product shown in formula (1). The first intermediate product shown in formula (1) and the polyethylene polyamine shown in formula (2) were reacted in the first solvent system at 150℃~160℃, and then the reaction was continued under vacuum at 210℃~220℃. The first solvent was removed by evaporation to obtain the second intermediate product shown in formula (3). The second intermediate product shown in formula (3), formaldehyde and acetophenone were reacted in the second solvent system at 70℃~80℃, and the second solvent was removed by evaporation to obtain the main agent of the bismannich base azithiazole corrosion inhibitor. The specific chemical reaction formula is shown below: ； Where n = 1 to 4.

7. The method for preparing the corrosion inhibitor for annular protective fluid in oil and gas wells according to claim 6, characterized in that, The mass ratio of melamine to chloroacetic acid is 1:1 to 1.2; the alkaline solution is obtained by mixing inorganic alkali and water; the mass ratio of melamine to inorganic alkali is 5:4 to 5.

8. The method for preparing the corrosion inhibitor for annular protective fluid in oil and gas wells according to claim 6, characterized in that, The mass ratio of the first intermediate product shown in formula (1) to the polyethylene polyamine shown in formula (2) is 1:2 to 2.5; the first solvent is N,N-dimethylformamide or xylene.

9. The method for preparing the corrosion inhibitor for annular protective fluid in oil and gas wells according to claim 6, characterized in that, The mass ratio of the second intermediate product, formaldehyde and acetophenone shown in formula (3) is 4:1 to 1.2:4 to 4.2; the second solvent is N,N-dimethylformamide or ethanol.

10. An application of a corrosion inhibitor for annular protection fluid in oil and gas wells as a composite corrosion inhibitor in the preparation of annular protection fluid for oil and gas wells, characterized in that, The corrosion inhibitor for annular protection fluid in oil and gas wells is the corrosion inhibitor for annular protection fluid in oil and gas wells as described in any one of claims 1 to 4.

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