A corrosion and scale inhibitor for oil and gas wells and its preparation method

Abstract

This application discloses a corrosion and scale inhibitor for oil and gas wells and its preparation method, relating to the technical field of environmentally friendly materials. The invention comprises a compound comprising an imidazoline polyoxyethylene ether corrosion inhibitor, a quaternary ammonium salt corrosion inhibitor capsule, and an organophosphoric acid corrosion inhibitor; the quaternary ammonium salt corrosion inhibitor capsule comprises a quaternary ammonium salt corrosion inhibitor as a core and a dispersant as a wall. By compounding the imidazoline polyoxyethylene ether corrosion inhibitor, the quaternary ammonium salt corrosion inhibitor capsule, and the organophosphoric acid corrosion inhibitor, the invention improves the corrosion inhibition and long-term effectiveness of pipelines in oil and gas wells, saves the amount of corrosion and scale inhibitor used, and simultaneously reduces the deposition of inorganic deposits such as calcium carbonate on pipelines in oil and gas wells, thereby improving scale inhibition.

Description

Technical Field

[0001] The present application relates to the field of pipeline protection in oil and gas wells, and in particular to a corrosion and scale inhibitor for oil and gas wells and a preparation method thereof. Background Art

[0002] During the extraction and centralized transportation of oil and natural gas, the oil pipes used in oil and gas wells are easily corroded and fail due to the complex environment in the wells, which are often accompanied by corrosive media such as highly mineralized liquids, carbon dioxide, and hydrogen sulfide.

[0003] Currently, corrosion inhibitors are often added to protect pipelines in oil and gas wells. For example, an ultra-high temperature acidizing corrosion inhibitor for Cr-containing oil pipes and its preparation method (CN114989798A) uses a Mannich base compound as the primary corrosion inhibitor, and an oilfield water injection corrosion inhibitor (CN1277241) uses an imidazoline derivative as the primary component. Because the fluid in oil and gas wells is constantly flowing, corrosion inhibitors are often added continuously at a fixed flow rate from storage tanks to maintain an effective concentration of the corrosion inhibitor.

[0004] However, as the fluid flows longer in the oil and gas well, the concentration of the corrosion inhibitor gradually decreases due to adsorption by the pipeline and consumption of the corrosive medium in the fluid. If the flow rate of continuous addition of the corrosion inhibitor is too fast, although it can ensure that the concentration of the corrosion inhibitor in the later process can still be maintained at an effective level, it will also increase the unnecessary consumption of the corrosion inhibitor by the corrosive medium in the fluid in the previous process. If the flow rate of continuous addition of the corrosion inhibitor is too slow, the adsorption efficiency of the corrosion inhibitor in the later process fluid on the pipeline will be reduced, the coverage will decrease, and the corrosion inhibition effect will be worse. Summary of the Invention

[0005] In view of the deficiencies of the above-mentioned related technologies, the purpose of this application is to provide a corrosion and scale inhibitor for oil and gas wells and a preparation method thereof. By compounding imidazoline polyoxyethylene ether corrosion inhibitors, quaternary ammonium salt corrosion inhibitor capsules and organophosphate corrosion inhibitors, on the one hand, the imidazoline polyoxyethylene ether corrosion inhibitors are dispersed and adsorbed on the surface of the pipeline in the oil and gas wells to form a basic protective layer. On the other hand, in the early stage of corrosion inhibitor addition, the capsule wall of the quaternary ammonium salt corrosion inhibitor capsules isolates the quaternary ammonium salt corrosion inhibitor from the fluid, thereby avoiding the quaternary ammonium salt corrosion inhibitor from being consumed prematurely. As the addition time increases, the capsule wall made of dispersant dissolves, gradually releasing the quaternary ammonium salt corrosion inhibitor while increasing the dispersion effect of the quaternary ammonium salt corrosion inhibitor and the imidazoline polyoxyethylene ether corrosion inhibitor in the later process, thereby improving the adsorption efficiency of the later process pipeline, increasing the coverage degree, and improving the corrosion inhibition and long-term effect.

[0006] In the first aspect, the present application provides a corrosion and scale inhibitor for oil and gas wells using the following technical solution:

[0007] A corrosion and scale inhibitor for oil and gas wells is prepared by compounding an imidazoline polyoxyethylene ether corrosion inhibitor, a quaternary ammonium salt corrosion inhibitor capsule and an organic phosphoric acid corrosion inhibitor; the quaternary ammonium salt corrosion inhibitor capsule is prepared with the quaternary ammonium salt corrosion inhibitor as the core and a dispersant as the wall.

[0008] Preferably, the following components are included in parts by weight: 20-40 parts of imidazoline polyoxyethylene ether corrosion inhibitor, 10-20 parts of quaternary ammonium salt corrosion inhibitor capsules and 5-10 parts of organophosphoric acid corrosion inhibitor.

[0009] Preferably, the following components are included in parts by weight: 30 parts of imidazoline polyoxyethylene ether corrosion inhibitor, 15 parts of quaternary ammonium salt corrosion inhibitor capsules and 8 parts of organophosphoric acid corrosion inhibitor.

[0010] Preferably, the quaternary ammonium salt corrosion inhibitor includes one or more of benzoic acid imidazoline quaternary ammonium salt and its derivatives, heptadecenylamine ethyl imidazoline quaternary ammonium salt and its derivatives.

[0011] Preferably, the quaternary ammonium salt corrosion inhibitor is heptadecenylamineethylimidazoline quaternary ammonium salt.

[0012] Preferably, the dispersant includes one or both of sodium polyacrylate and polyacrylic acid.

[0013] Preferably, the dispersant is sodium polyacrylate.

[0014] Preferably, the imidazoline polyoxyethylene ether corrosion inhibitor includes one or more of imidazoline polyoxyethylene ether, oleic acid imidazoline polyoxyethylene ether and rosin imidazoline polyoxyethylene ether.

[0015] Preferably, the imidazoline polyoxyethylene ether corrosion inhibitor is imidazoline polyoxyethylene ether.

[0016] Preferably, the organic phosphoric acid corrosion inhibitor includes one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid and ethylenediaminetetramethylphosphonic acid.

[0017] Preferably, the organic phosphoric acid corrosion inhibitor is hydroxyethylidene diphosphonic acid.

[0018] On the other hand, the present application provides a method for preparing a corrosion and scale inhibitor for oil and gas wells using the following technical solution:

[0019] A method for preparing a corrosion and scale inhibitor for oil and gas wells comprises the following steps: preparing a solution with a quaternary ammonium salt corrosion inhibitor and a dispersant, adjusting the pH value of the solution to 4 during stirring, continuously stirring until precipitation is generated, collecting the precipitation by centrifugation, washing, and then drying to obtain quaternary ammonium salt corrosion inhibitor capsules; and mixing the quaternary ammonium salt corrosion inhibitor capsules, an imidazoline polyoxyethylene ether corrosion inhibitor, and a quaternary organophosphoric acid corrosion inhibitor to obtain the corrosion and scale inhibitor for oil and gas wells.

[0020] Preferably, the quaternary ammonium salt corrosion inhibitor is heptadecenylamineethylimidazoline quaternary ammonium salt, and the dispersant is sodium polyacrylate.

[0021] Preferably, the weight ratio of the heptadecenylaminoethylimidazoline quaternary ammonium salt to the sodium polyacrylate is 1:1-2.

[0022] Preferably, the weight ratio of the heptadecenylaminoethylimidazoline quaternary ammonium salt to the sodium polyacrylate is 1:1.5.

[0023] Preferably, the mass concentration of the quaternary ammonium salt corrosion inhibitor and the dispersant in the solution is 8%-12%.

[0024] Preferably, the mass concentration of the quaternary ammonium salt corrosion inhibitor and dispersant in the solution is 10%.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. By compounding imidazoline polyoxyethylene ether corrosion inhibitors, quaternary ammonium salt corrosion inhibitor capsules and organophosphoric acid corrosion inhibitors, on the one hand, the imidazoline polyoxyethylene ether corrosion inhibitor is dispersed and adsorbed on the surface of the upstream pipeline in the oil and gas well to form a basic protective layer. The capsule wall of the quaternary ammonium salt corrosion inhibitor capsule isolates the quaternary ammonium salt corrosion inhibitor from the fluid, thereby preventing the quaternary ammonium salt corrosion inhibitor from being consumed prematurely. On the other hand, as the flow rate of the corrosion and scale inhibitor used in the oil and gas well increases, the capsule wall made of the dispersant dissolves, gradually releasing the quaternary ammonium salt corrosion inhibitor. The dispersant dissolved in the fluid increases the dispersion effect of the quaternary ammonium salt corrosion inhibitor and the imidazoline polyoxyethylene ether corrosion inhibitor in the downstream, thereby improving the adsorption efficiency of the downstream pipeline, increasing the coverage, and also improving the chelating ability of the imidazoline polyoxyethylene ether and the organophosphoric acid corrosion inhibitor. Under the combined effect, the three produce a synergistic effect, which improves the adsorption efficiency and covering effect of the pipelines in the oil and gas wells, and complexes the metal ions in the fluid, achieving the corrosion and scale inhibition effects on the front and middle pipelines in the oil and gas wells.

[0027] 2. As the time of adding corrosion and scale inhibitors for oil and gas wells increases, the amount of dissolution of the capsule wall made of the dispersant increases, and the release amount of the quaternary ammonium salt corrosion inhibitor increases. The quaternary ammonium salt corrosion inhibitor works synergistically through multiple mechanisms of adsorption-chelation-lattice distortion. On the one hand, its strong adsorption effect is conducive to repairing the defects of the film formed by the imidazoline polyoxyethylene ether corrosion inhibitor on the pipeline surface due to water flow impact or reduced consumption, thereby improving the corrosion inhibition effect and its long-term effectiveness; on the other hand, it inhibits the generation and accumulation of scale on the pipeline surface and improves the scale inhibition effect.

[0028] 3. The present application uses sodium polyacrylate as a dispersant, and controls the pH to induce sodium polyacrylate to precipitate from the solution on the surface of the quaternary ammonium salt corrosion inhibitor emulsion to self-assemble into a wall and then dry, thereby forming a quaternary ammonium salt corrosion inhibitor capsule. When in use, the wall material dissolves to release the sodium polyacrylate while releasing the quaternary ammonium salt corrosion inhibitor. The high dispersion efficiency of the imidazoline polyoxyethylene ether corrosion inhibitor and the high adsorption capacity of the quaternary ammonium salt corrosion inhibitor are utilized to efficiently respond to form a film on the pipeline in the oil and gas well to improve the corrosion inhibition rate and scale inhibition rate. The defects of the imidazoline polyoxyethylene ether corrosion inhibitor film are reinforced by the high adsorption capacity of the quaternary ammonium salt corrosion inhibitor. Under the combined effect, the corrosion inhibition effect and its long-term effectiveness are improved. DETAILED DESCRIPTION

[0029] The present application is described in further detail below in conjunction with Examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. In the following examples, if specific conditions are not specified, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The methods used are conventional methods well known in the art unless otherwise specified, and the consumables and reagents used are commercially available unless otherwise specified. Unless otherwise indicated, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0030] The raw materials used in the examples and comparative examples can all be obtained commercially.

[0031] Example 1

[0032] Example 1 of the present application provides a corrosion and scale inhibitor for oil and gas wells, which is obtained by compounding 30 parts by weight of imidazoline polyoxyethylene ether, 15 parts by weight of heptadecenylamine ethyl imidazoline quaternary ammonium salt capsules and 8 parts by weight of organic phosphoric acid corrosion inhibitor.

[0033] The heptadecanylamine ethyl imidazoline quaternary ammonium salt capsules are prepared by the following steps:

[0034] 10 parts by weight of heptadecanylaminoethylimidazoline quaternary ammonium salt were dissolved in cyclohexane and 2% by weight of sorbitan oleate was added. 15 parts by weight of sodium polyacrylate were dissolved in water, mixed and emulsified to form an O / W emulsion. 0.1 mol / L dilute hydrochloric acid was added dropwise to the emulsion to adjust the pH of the solution to 4. The mixture was stirred for 1 hour and centrifuged at 3000 rpm for 5 minutes. The precipitate was collected, washed three times with deionized water, and dried to obtain heptadecanylaminoethylimidazoline quaternary ammonium salt capsules with heptadecanylaminoethylimidazoline quaternary ammonium salt as the core and sodium polyacrylate as the wall.

[0035] In this embodiment, the organic phosphoric acid corrosion inhibitor is hydroxyethylidene diphosphonic acid.

[0036] Example 2

[0037] Example 2 of the present application provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Example 2 and Example 1 is that Example 2 is obtained by compounding 20 parts by weight of imidazoline polyoxyethylene ether, 20 parts by weight of heptadecanylamine ethyl imidazoline quaternary ammonium salt capsules and 5 parts by weight of organic phosphoric acid corrosion inhibitor.

[0038] Example 3

[0039] Example 3 of the present application provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Example 3 and Example 1 is that Example 2 is obtained by compounding 40 parts by weight of imidazoline polyoxyethylene ether, 10 parts by weight of heptadecanylamine ethyl imidazoline quaternary ammonium salt capsules and 10 parts by weight of organic phosphoric acid corrosion inhibitor.

[0040] Example 4

[0041] Example 4 of the present application provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Example 4 and Example 1 is that, in Example 4, 10 parts by weight of 17-enylaminoethylimidazoline quaternary ammonium salt and 10 parts by weight of sodium polyacrylate are used in the preparation of the 17-enylaminoethylimidazoline quaternary ammonium salt capsules.

[0042] Example 5

[0043] Example 5 of the present application provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Example 5 and Example 1 is that when preparing the heptadecanylaminoethylimidazoline quaternary ammonium salt capsules in Example 5, 10 parts by weight of heptadecanylaminoethylimidazoline quaternary ammonium salt and 20 parts by weight of sodium polyacrylate are used.

[0044] Comparative Example 1

[0045] Comparative Example 1 provides a corrosion and scale inhibitor for oil and gas wells. The difference between Comparative Example 1 and Example 1 is that: in Comparative Example 1, no heptadecenylamine ethyl imidazoline quaternary ammonium salt capsules are added, and hydroxyethylidene diphosphonic acid is used in equal parts by weight to supplement it.

[0046] Comparative Example 2

[0047] Comparative Example 2 provides a corrosion and scale inhibitor for oil and gas wells. The difference between Comparative Example 2 and Example 1 is that: in Comparative Example 2, no organic phosphoric acid corrosion inhibitor is added, and an equal weight portion of heptadecenylamine ethyl imidazoline quaternary ammonium salt capsule is used to supplement it.

[0048] Comparative Example 3

[0049] Comparative Example 3 provides a corrosion and scale inhibitor for oil and gas wells. The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, imidazoline polyoxyethylene ether is not added, and hydroxyethylidene diphosphonic acid is used as a supplement in equal parts by weight.

[0050] Comparative Example 4

[0051] Comparative Example 4 provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Comparative Example 4 and Example 1 is that equal parts by weight of heptadecanylamine ethyl imidazoline quaternary ammonium salt are used to replace heptadecanylamine ethyl imidazoline quaternary ammonium salt capsules in Comparative Example 2.

[0052] Comparative Example 5

[0053] Comparative Example 5 provides a corrosion inhibitor and scale inhibitor for oil and gas wells. The difference between Comparative Example 5 and Example 1 is that in Comparative Example 5, 6 parts by weight of heptadecanylamine ethyl imidazoline quaternary ammonium salt and 9 parts by weight of sodium polyacrylate are used to replace 15 parts by weight of heptadecanylamine ethyl imidazoline quaternary ammonium salt capsules.

[0054] Test and Inspection

[0055] (1) The dosage of the corrosion inhibitor and scale inhibitor for oil and gas wells is 30 ppm. A 5% sodium chloride solution is used as the corrosion water sample. 42MnMo7 steel is used as the hanging sample. A simulation experiment is carried out for 10 days under the conditions of 70°C and 20 MPa. The corrosion inhibition rates (%) of the corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5 are detected. The scale inhibition rates (%) of the corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5 on calcium carbonate are respectively detected in accordance with the SY / T5673-2020 standard. The results are shown in Table 1 below.

[0056] Table 1:

[0057] Data Source Scale inhibition rate (%) Corrosion inhibition rate (%) Example 1 94.3 91.5 Example 2 93.2 90.8 Example 3 93.8 91.2 Example 4 91.7 90.1 Example 5 93.6 91.1 Comparative Example 1 75.5 70.3 Comparative Example 2 78.3 71.5 Comparative Example 3 73.7 68.6 Comparative Example 4 82.1 79.4 Comparative Example 5 84.3 80.2

[0058] (2) The initial dosage of the corrosion inhibitor and scale inhibitor for oil and gas wells was 30 ppm. A 5% sodium chloride solution was used as the corrosion water sample. 42MnMo7 steel was used as a coupon sample and placed under conditions of 70°C and 20 MPa. The coupons were replaced every day. The simulation experiment lasted 10 days. The corrosion inhibition rates (%) of the corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5 were tested. The corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5 were prepared into solutions. 42MnMo7 steel was used as a coupon sample and placed under conditions of 70°C and 20 MPa. After 10 days, the coupons were removed to obtain diluted solutions of the corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5. The scale inhibition rates (%) of the diluted solutions of the corrosion inhibitor and scale inhibitor for oil and gas wells of Examples 1-5 and Comparative Examples 1-5 on calcium carbonate were tested respectively according to the SY / T5673-2020 standard. The results are shown in Table 2 below.

[0059] Table 2:

[0060] Data Source Scale inhibition rate (%) Corrosion inhibition rate (%) Example 1 92.3 90.6 Example 2 90.8 89.5 Example 3 91.6 89.8 Example 4 88.7 87.9 Example 5 90.4 89.2 Comparative Example 1 67.2 65.2 Comparative Example 2 73.2 68.4 Comparative Example 3 68.3 65.5 Comparative Example 4 73.8 75.6 Comparative Example 5 74.9 76.3

[0061] Result Analysis

[0062] The following describes this application in detail in conjunction with the data results in Table 1 and Table 2.

[0063] Referring to Table 1, the scale inhibition rate and corrosion inhibition rate of the corrosion inhibitors and scale inhibitors for oil and gas wells of Examples 1-5 both reached over 90%, among which the scale inhibition rate of the corrosion inhibitor and scale inhibitor for oil and gas wells of Example 1 reached 94.3%, and the corrosion inhibition rate reached 91.5%. Taking Example 1 as a reference, Comparative Examples 1-3 investigated the effect of the type of compounding materials in the corrosion inhibitor and scale inhibitor for oil and gas wells on the scale inhibition rate and corrosion inhibition rate of the corrosion inhibitor and scale inhibitor for oil and gas wells. The scale inhibition rate and corrosion inhibition rate of the corrosion inhibitor and scale inhibitor for oil and gas wells of Example 1 were much higher than the scale inhibition rate and corrosion inhibition rate of the scale inhibitor for oil and gas transportation of Comparative Examples 1-3. This indicates that the compounding of imidazoline polyoxyethylene ether, heptadecanylaminoethyl imidazoline quaternary ammonium salt capsules and organophosphoric acid corrosion inhibitors has a synergistic effect in improving the scale inhibition rate and corrosion inhibition rate of the corrosion inhibitor and scale inhibitor for oil and gas wells.

[0064] Using Example 1 as a control, Comparative Examples 4 and 5 investigated the effect of the addition form of heptadecenylaminoethylimidazoline quaternary ammonium salt on the scale inhibition and corrosion inhibition rates of the corrosion inhibitors for oil and gas wells. The scale inhibition and corrosion inhibition rates of the corrosion inhibitor for oil and gas wells in Example 1 were much higher than those of the scale inhibitors for oil and gas transportation in Comparative Examples 4 and 5. This indicates that the use of sodium polyacrylate as the capsule wall of the heptadecenylaminoethylimidazoline quaternary ammonium salt is beneficial for improving the scale inhibition and corrosion inhibition rates of the corrosion inhibitor for oil and gas wells. The analysis shows that, in the initial stage of adding the corrosion and scale inhibitor for oil and gas wells, part of the sodium polyacrylate dissolved in the water, and produced a synergistic effect with the imidazoline polyoxyethylene ether to improve the dispersion effect of the imidazoline polyoxyethylene ether, and further improved the chelating ability of the imidazoline polyoxyethylene ether with the organic phosphoric acid corrosion inhibitor. The three produced a synergistic effect, achieving the effect of quickly inhibiting suspended scale in the initial stage of adding the corrosion and scale inhibitor for oil and gas wells, and accelerated the dispersion and adsorption efficiency of the imidazoline polyoxyethylene ether on the sample. Under the combined effect, the scale inhibition rate and corrosion inhibition rate were improved.

[0065] Referring to Table 2, under the condition where the simulated corrosion and scale inhibitor for oil and gas wells was consumed, compared to the data in Table 1, the scale inhibition rate of the simulated corrosion and scale inhibitor for oil and gas transportation of Examples 1-5 decreased by 2%-3.2%, and the corrosion inhibition rate of the simulated corrosion and scale inhibitor for oil and gas transportation of Examples 1-5 decreased by 0.9%-2.2%. In contrast, the scale inhibition rate of the simulated corrosion and scale inhibitor for oil and gas transportation of Comparative Examples 1, 4, and 5 decreased by 8.3%-9.4%, and the corrosion inhibition rate of the corrosion and scale inhibitor for oil and gas wells of Comparative Examples 1, 4, and 5 decreased by 3.9%-5.1%. This indicates that the addition of heptadecenylaminoethylimidazoline quaternary ammonium salt in the form of capsules to the corrosion and scale inhibitor for oil and gas wells is beneficial to improving the corrosion and scale inhibition rate after the well corrosion and scale inhibitor is consumed. Analysis shows that the capsule wall of the quaternary ammonium corrosion inhibitor capsule isolates the quaternary ammonium corrosion inhibitor from the liquid, thereby preventing the quaternary ammonium corrosion inhibitor from being consumed prematurely by the sample. As time goes by, the capsule wall made of dispersant dissolves and gradually releases the quaternary ammonium corrosion inhibitor. On the one hand, its strong adsorption effect is conducive to repairing the defects of the film formed by the imidazoline polyoxyethylene ether corrosion inhibitor on the surface of the pipeline, thereby improving the corrosion inhibition effect and its long-term effectiveness; on the other hand, it inhibits the generation and accumulation of scale on the surface of the pipeline and improves the scale inhibition effect.

[0066] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A corrosion and scale inhibitor for oil and gas wells, characterized by: The invention is prepared by compounding an imidazoline polyoxyethylene ether corrosion inhibitor, a quaternary ammonium salt corrosion inhibitor capsule and an organic phosphoric acid corrosion inhibitor; the quaternary ammonium salt corrosion inhibitor capsule is prepared with the quaternary ammonium salt corrosion inhibitor as the core and the dispersant as the wall; the imidazoline polyoxyethylene ether corrosion inhibitor is 20-40 parts, the quaternary ammonium salt corrosion inhibitor capsule is 10-20 parts and the organic phosphoric acid corrosion inhibitor is 5-10 parts; the quaternary ammonium salt corrosion inhibitor is heptadecenylaminoethyl imidazoline quaternary ammonium salt; the dispersant is sodium polyacrylate; the imidazoline polyoxyethylene ether corrosion inhibitor is imidazoline polyoxyethylene ether; and the organic phosphoric acid corrosion inhibitor is hydroxyethylidene diphosphonic acid; The weight ratio of the heptadecenylaminoethyl imidazoline quaternary ammonium salt to the sodium polyacrylate is 1:1-2; The quaternary ammonium salt corrosion inhibitor capsule is prepared by the following steps: dissolving heptadecenylamineethylimidazoline quaternary ammonium salt in an organic solvent as an oil phase, preparing an aqueous solution of sodium polyacrylate as an aqueous phase, mixing the oil phase and the aqueous phase, adjusting the pH of the aqueous phase to 4, continuously stirring for 0.5-1.5 hours, collecting the precipitate by centrifugation, washing, and then drying to obtain the quaternary ammonium salt corrosion inhibitor capsule.

2. The method for preparing a corrosion and scale inhibitor for oil and gas wells according to claim 1, wherein: The following steps are involved: A quaternary ammonium salt corrosion inhibitor is dissolved in an organic solvent as an oil phase, a dispersant is prepared into an aqueous solution as an aqueous phase, the oil phase and the aqueous phase are mixed, and the pH of the aqueous phase is adjusted to 4, and the mixture is stirred for 0.5-1.5 hours. The precipitate is collected by centrifugation, washed, and then dried to obtain a quaternary ammonium salt corrosion inhibitor capsule; The quaternary ammonium salt corrosion inhibitor capsule, the imidazoline polyoxyethylene ether corrosion inhibitor and the organic phosphoric acid corrosion inhibitor are mixed to obtain the corrosion and scale inhibitor for oil and gas wells.

3. The method for preparing a corrosion and scale inhibitor for oil and gas wells according to claim 2, characterized in that: The oil phase is added with 2% by mass of a lipophilic nonionic dispersant.