Corrosion inhibitor for inhibiting CO2 corrosion, and preparation method and application thereof

Abstract

The application relates to the field of CO2 corrosion prevention technology, and discloses a CO2 corrosion inhibitor, a preparation method and application thereof. The CO2 corrosion inhibitor comprises the following components: S-benzyl thiourea hydrochloride 15-25%, organic acetylenic alcohol 15-25%, and hexamethylenetetramine 50-70%. A large number of hydrogen bonds are easily formed among the molecules of the three components, a cross-linking effect is generated, the chemical adsorption of amine and the film forming effect of organic acetylenic alcohol are mutually strengthened, the adsorption layer of the corrosion inhibitor is more stable, the cross-linking adsorption film on the surface of steel is thickened, the organic acetylenic alcohol small molecules can be embedded into the gap between the two cyclic molecules of S-benzyl thiourea hydrochloride and hexamethylenetetramine, and are adsorbed on the surface of steel, so that a dense cross-linking adsorption film is formed, and the corrosion speed of the metal is effectively reduced. The CO2 corrosion inhibitor provided by the application has few formula components, low cost, stable corrosion inhibition effect, good synergistic effect, and can effectively inhibit the corrosion of CO2 on steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of CO2 corrosion prevention, in particular to a corrosion inhibitor for inhibiting CO2 corrosion and a preparation method and application thereof. BACKGROUND

[0002] CO2 flooding technology is a kind of tertiary oil recovery technology with good prospects. CO2 is injected and stored into the oil layer through geological storage, and the oil recovery efficiency is improved by reducing the oil-water and oil-gas interfacial tension, reducing the viscosity of crude oil, improving the mobility ratio, improving the formation pressure and permeability. However, with the increase of CO2 content in the oil well, part of CO2 dissolves in water to form carbonic acid, which corrodes the metal products such as oil well pipes and equipment, seriously affecting the production of oil and gas fields. At present, the methods for CO2 corrosion include using appropriate plating, selecting corrosion-resistant materials, applying corrosion-resistant coatings, and adding corrosion inhibitors, etc. Among them, injecting corrosion inhibitors has the advantages of economy, high efficiency, simple operation, etc., and is a common corrosion prevention method.

[0003] In recent years, a large number of corrosion inhibitors for inhibiting CO2 corrosion have been developed. For example, the patent with publication number CN103820789A discloses a complex CO2 corrosion inhibitor composition, which is prepared by compounding imidazoline corrosion inhibitor and its derivatives, fatty amine and its derivatives, rosin amine and other organic compounds with thiourea and sodium dodecyl sulfonate. The prepared corrosion inhibitor has a more dense adsorption layer on the surface of carbon steel, thereby improving the corrosion inhibition effect of the corrosion inhibitor on carbon steel materials in the CO2 corrosion system. For another example, the patent application with publication number CN104513204A discloses a CO2 corrosion inhibitor composition containing a triple bond imidazoline, which is prepared by compounding a triple bond double imidazoline compound, a non-ionic surfactant and a low molecular alcohol. The prepared corrosion inhibitor has good water solubility, compatibility and corrosion inhibition in high salinity oil and gas field production fluids.

[0004] However, the existing CO2 corrosion inhibitor involves many components, has high cost, complex raw material preparation method, and the corrosion inhibition rate still needs to be improved. SUMMARY

[0005] The present application provides a corrosion inhibitor for inhibiting CO2 corrosion and a preparation method and application thereof, aiming to solve the technical problems of the existing CO2 corrosion inhibitor, such as complex compounding components, difficult raw material synthesis, high cost and low corrosion inhibition rate.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0007] The present application provides a corrosion inhibitor for inhibiting CO2 corrosion, which comprises the following components according to mass percentage:

[0008] S-benzyl thiourea hydrochloride 15% to 25%;

[0009] Organic alkynols 15%–25%;

[0010] Hexamethylenetetramine 50%–70%.

[0011] In some embodiments, the corrosion inhibitor for suppressing CO2 corrosion comprises, by weight percentage, the following components:

[0012] S-Benzylthiourea hydrochloride 18%–22%;

[0013] Organic alkynols: 18%–22%;

[0014] Hexamethylenetetramine 56%–64%.

[0015] In some embodiments, the organic alkynol is any one or a mixture of ethynol, propynol, 1,4-butynediol or methylbutynol.

[0016] Another aspect of this application provides a corrosion inhibitor for suppressing CO2 corrosion, comprising the following components by mass percentage:

[0017] S-benzylthiourea hydrochloride 20%, 1,4-butynediol 20%, hexamethylenetetramine 60%;

[0018] or

[0019] S-Benzylthiourea hydrochloride 18%, Ethynyl alcohol 18%, Hexamethylenetetramine 64%;

[0020] or

[0021] S-Benzylthiourea hydrochloride 22%, propargyl alcohol 20%, hexamethylenetetramine 58%.

[0022] Another aspect of this application provides a method for preparing the corrosion inhibitor for inhibiting CO2 corrosion, comprising:

[0023] Weigh out S-benzylthiourea hydrochloride, organic alkynol and hexamethylenetetramine according to the mass percentage, mix them evenly to obtain the corrosion inhibitor for CO2 corrosion.

[0024] Another aspect of this application provides the application of the above-mentioned CO2 corrosion inhibitor or the CO2 corrosion inhibitor prepared by the above-mentioned preparation method in the corrosion protection of steel in oil and gas fields.

[0025] Another aspect of this application provides a method for corrosion protection of steel in oil and gas fields, which involves injecting the aforementioned corrosion inhibitor that suppresses CO2 corrosion into the formation water of the oil and gas field to protect the steel from corrosion.

[0026] In some embodiments, the concentration of the corrosion inhibitor that inhibits CO2 corrosion is 200 mg / L.

[0027] Compared with the prior art, the beneficial effects of this application are as follows:

[0028] The corrosion inhibitor formulation of this application for inhibiting CO2 corrosion has few components, readily available and low-cost raw materials, and good corrosion inhibition effect; the synergistic effect of each component is good, which can effectively inhibit the corrosion of steel by CO2.

[0029] In the CO2 corrosion inhibitor of this application, the benzyl group in S-benzylthiourea hydrochloride can directly increase the effective coverage area of ​​the inhibitor molecules, and at the same time, it can act as an electron-donating group to increase the adsorption coordination atoms. Moreover, the benzyl group is hydrophobic, forming a more effective protective barrier to isolate the corrosive medium. In S-benzylthiourea hydrochloride, -NH2 is an electron-donating group. Under the combined effect of the electron-donating effect of the substituent and the delocalization effect of the conjugated structure, the electron cloud density of the central group increases, which coordinates with the metal to form a chemical adsorption, thereby reducing the corrosion of steel by CO2. The lone pair electrons on the hexamethylenetetramine molecule can coordinate with the empty d orbitals on the iron atoms on the steel surface to form a chemical adsorption and form a dense protective film. The π bond in the alkynol triple bond can combine with the empty d orbitals of the metal atom to form a coordinate bond, thereby allowing the inhibitor molecules to be adsorbed on the metal surface. Most importantly, in the CO2 corrosion inhibitor of this application, the three components exhibit a synergistic effect. The S-benzylthiourea hydrochloride, hexamethylenetetramine, and alkynol readily form numerous hydrogen bonds, resulting in a cross-linking effect. This mutually reinforces the chemical adsorption of the amine and the film-forming effect of the organic alkynol, making the corrosion inhibitor adsorbed layer more stable and increasing the thickness of the cross-linked adsorbed film on the steel surface. Simultaneously, the small molecules of the organic alkynol can embed into the gaps between the two cyclic molecules of S-benzylthiourea hydrochloride and hexamethylenetetramine, adsorbing onto the steel surface to form a dense cross-linked adsorbed film, effectively reducing the corrosion rate of the metal. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram illustrating the synergistic effect of the components of the corrosion inhibitor that suppresses CO2 corrosion in this application;

[0032] Figure 2 Impedance diagrams for different corrosion inhibitors;

[0033] Figure 3The image shows the SEM image of the J55 sample after CO2 saturation and simulated formation water corrosion. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0036] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0037] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0038] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0039] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0040] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0042] In a first aspect, embodiments of this application provide a corrosion inhibitor for suppressing CO2 corrosion. The corrosion inhibitor for suppressing CO2 corrosion of this application comprises, by mass percentage, the following components:

[0043] S-benzylthiourea hydrochloride 15%–25%;

[0044] Organic alkynols 15%–25%;

[0045] Hexamethylenetetramine 50%–70%.

[0046] The chemical structure of the S-benzylthiourea hydrochloride of this application is shown in formula (1):

[0047]

[0048]

[0049] In this application, the benzyl group in S-benzylthiourea hydrochloride directly increases the effective coverage area of ​​the corrosion inhibitor molecule and also acts as an electron-donating group to increase the adsorption coordination atoms. The benzyl group is hydrophobic, forming a more effective protective barrier against corrosive media. In S-benzylthiourea hydrochloride, the -NH2 group is an electron-donating group. Under the combined effect of the electron-donating effect of the substituent and the delocalization effect of the conjugated structure, the electron cloud density of the central group increases, leading to coordination bonding with the metal and forming chemisorption, thereby reducing CO2 corrosion of the steel. The mass percentage of S-benzylthiourea hydrochloride in the CO2 corrosion inhibitor of this application is 15% to 25%, for example, 15%, 18%, 20%, 22%, 24%, 25%, or any value within this range.

[0050] In this process, the lone pair electrons on the hexamethylenetetramine molecule can coordinate with the empty d orbitals on the iron atoms on the steel surface to form a chemical adsorption, resulting in a dense protective film. The π bond in the alkynol triple bond can combine with the empty d orbitals of the metal atoms to form a coordinate bond, thereby allowing the corrosion inhibitor molecules to adsorb onto the metal surface. The hexamethylenetetramine content in the CO2 corrosion inhibitor of this application is 50% to 70% by mass, for example, 50%, 58%, 60%, 64%, 70%, or any value within this range.

[0051] Among them, organic alkynols can not only undergo π-bond adsorption, but especially after introducing hydroxyl groups (-OH) into these compounds, they can donate protons to the cathode region of the metal surface to generate adsorption, thereby reducing metal corrosion. The organic alkynols in the corrosion inhibitor for inhibiting CO2 corrosion of this application have a mass percentage of 15% to 25%, for example 15%, 16%, 18%, 20%, 22%, 25%, or any value within this range.

[0052] In the CO2 corrosion inhibitor of this application embodiment, S-benzylthiourea hydrochloride, organic alkynyl alcohol, and hexamethylenetetramine are mixed in a specific ratio. The components work synergistically to effectively solve the CO2 corrosion problem. The principle is as follows: S-benzylthiourea hydrochloride, hexamethylenetetramine, and alkynyl alcohol readily form numerous hydrogen bonds, resulting in a cross-linking effect. This strengthens the chemical adsorption of the amine and the film-forming effect of the organic alkynyl alcohol, making the corrosion inhibitor adsorption layer more stable and increasing the thickness of the cross-linked adsorption film on the steel surface. Simultaneously, the small molecules of organic alkynyl alcohol can embed into the gaps between the two cyclic molecules of S-benzylthiourea hydrochloride and hexamethylenetetramine, adsorbing onto the steel surface to form a dense cross-linked adsorption film, effectively reducing the corrosion rate of the metal. The adsorption principle is as follows: Figure 1 As shown. The corrosion inhibitor for CO2 corrosion of this application has few components and low cost, stable corrosion inhibition effect and good synergistic effect.

[0053] When the percentage content of S-benzylthiourea hydrochloride, hexamethylenetetramine, and alkynol is outside the above range, the corrosion inhibitor adsorption layer is unstable and the improvement on the morphology of the adsorption film is not obvious. In addition, the adsorbent is difficult to form a dense cross-linked adsorption film on the surface of the film. The above reasons lead to an insignificant synergistic effect and a reduced corrosion inhibition effect.

[0054] The corrosion inhibitor for inhibiting CO2 corrosion described in this application embodiment preferably comprises, by mass percentage: 18%–22% S-benzylthiourea hydrochloride; 18%–22% organic alkynol; and 56%–64% hexamethylenetetramine. The corrosion inhibitor for inhibiting CO2 corrosion prepared using the above components exhibits excellent synergistic effects among its components and demonstrates good corrosion inhibition performance.

[0055] In the embodiments of this application, the organic alkynol is any one or a mixture of ethynol, propynol, 1,4-butynediol or methylbutynol.

[0056] The corrosion inhibitor for inhibiting CO2 corrosion described in this application embodiment comprises, by mass percentage: 20% S-benzylthiourea hydrochloride, 20% 1,4-butynediol, and 60% hexamethylenetetramine; or 18% S-benzylthiourea hydrochloride, 18% ethynyl alcohol, and 64% hexamethylenetetramine; or 22% S-benzylthiourea hydrochloride, 20% propynyl alcohol, and 58% hexamethylenetetramine. The corrosion inhibitor for inhibiting CO2 corrosion prepared using the above components exhibits a better synergistic effect among the components, further enhancing the corrosion inhibition effect.

[0057] Secondly, this application provides a method for preparing a corrosion inhibitor to suppress CO2 corrosion, comprising:

[0058] Weigh out S-benzylthiourea hydrochloride, organic alkynol and hexamethylenetetramine according to the mass percentage, mix them evenly to obtain the corrosion inhibitor for CO2 corrosion.

[0059] Thirdly, the corrosion inhibitor for inhibiting CO2 corrosion in this application can be used for corrosion protection of steel in oil and gas fields, inhibiting CO2 corrosion of steel, preventing CO2 corrosion of steel oil casings, pipelines, equipment or structures in oil and gas fields, increasing the service life of steel oil casings, pipelines, equipment or structures in oil and gas fields, reducing costs, and having good economic benefits.

[0060] Fourthly, this application provides a method for corrosion protection of steel in oil and gas fields. The method involves continuously or periodically injecting the CO2 corrosion inhibitor of this application into the formation water of the oil and gas field to protect the steel from corrosion. The injection cycle depends on the dosage of the corrosion inhibitor added each time and the pipeline operating parameters. In the formation water of the oil and gas field, the CO2 corrosion inhibitor exhibits good slow-release effect when the added concentration is 100–300 mg / L. Considering both the slow-release effect and economic efficiency, the added concentration of the CO2 corrosion inhibitor can be selected as 200 mg / L.

[0061] The present application will be further illustrated by the following examples.

[0062] The corrosion inhibitor was prepared according to the components and proportions described in Table 1. Examples 1-6 are the components of the CO2 corrosion inhibitors of this application, and Comparative Examples 1-3 are the components of the corrosion inhibitors of the comparative examples of this application.

[0063] Table 1 Components of different corrosion inhibitors

[0064]

[0065] To better simulate the underground environment of oil and gas wells, simulated formation water was prepared. The corrosion inhibitors for inhibiting CO2 corrosion from Examples 1-6 and Comparative Examples 1-3 were added to the simulated formation water to prepare solutions with a concentration of 200 mg / L. The simulated formation water was prepared as follows: 33.12 g NaCl, 0.17 g Na2SO4, 0.24 g NaHCO3, 23.82 g CaCl2, 0.37 g MgCl2·6H2O, 2.14 g KCl, 0.19 g BaCl2, 1.10 g SrCl2, 0.0428 g Na3PO4, and 0.10 g NaNO3 were added to 1 L of water and stirred until completely dissolved.

[0066] The corrosion inhibitors for inhibiting CO2 corrosion in Examples 1-6 and the corrosion inhibitors in Comparative Examples 1-3 were subjected to high-pressure static plate tests and electrochemical impedance spectroscopy tests to evaluate their corrosion inhibition performance.

[0067] 1. High-voltage static clamp test

[0068] A sample measuring 40mm × 13mm × 2mm was prepared using J55 oil casing. The test temperature was 60℃, and the test apparatus was a TFCZ-22MPa / 350℃ high-temperature and high-pressure reactor. The test method is as follows:

[0069] Corrosion inhibitors were added to simulated groundwater to prepare a test solution with a concentration of 200 mg / L. The samples were sequentially polished to a mirror finish using 800-mesh, 1000-mesh, and 1600-mesh sandpaper, and then mounted on the sample fixing device in the high-temperature, high-pressure reactor. Three parallel samples were set up in each test group. 600 mL of the test solution was added to the high-temperature, high-pressure reactor, and the mixture was heated and deoxygenated with CO2 gas for 15 minutes. Once the set temperature was reached, CO2 gas was introduced to bring the pressure inside the reactor to 1.6 MPa, and the inlet valve was closed. After the CO2 pressure inside the reactor decreased, CO2 was introduced again until the pressure reached 1.6 MPa, and the inlet valve was closed. Stirring continued until the pressure decreased, and then CO2 was introduced again until the pressure reached 1.6 MPa, and the inlet valve was closed. If the CO2 pressure inside the reactor stabilized, N2 gas was introduced to bring the pressure to 5.0 MPa before starting the test. If the pressure decreased, N2 gas needed to be introduced continuously. The test cycle was 72 hours. The same method was used to conduct a blank experiment, in which the test solution was simulated groundwater without the addition of corrosion inhibitors, and the remaining steps were the same as the test method described above.

[0070] After the test, the sample was immersed in an acid cleaning solution (prepared with 500 mL HCl, 20 g hexamethylenetetramine, and 500 mL distilled water) for 5 minutes to remove surface corrosion products. After rinsing off the surface acid with distilled water, the sample was dehydrated with anhydrous ethanol and dried. It was then placed in a desiccator for 1 hour before weighing. The formulas for calculating the corrosion inhibition rate and corrosion rate are as follows:

[0071]

[0072] In the formula: η—corrosion inhibition rate, expressed as a percentage;

[0073] Δm0—mass loss in the blank test, in grams (g);

[0074] Δm1 — Mass loss of the test piece during the dosing test, in grams (g).

[0075]

[0076] In the formula: r c —Corrosion rate, in millimeters per year (mm / a);

[0077] m — mass loss before the experiment, in grams (g);

[0078] m1 — mass loss after the test, in grams (g);

[0079] S – Total area of ​​the test piece, in square centimeters (cm²) 2 )

[0080] t — Test time, in hours (h);

[0081] ρ — density of the sample material, in g / cm³ 3 )

[0082] Table 2 shows the corrosion inhibition efficiency data of the corrosion inhibitors of Examples 1-6 and Comparative Examples 1-3 on J55 samples.

[0083] Table 2. Corrosion inhibition performance data of corrosion inhibitors in Examples 1-6 and Comparative Examples 1-3.

[0084] Inhibitor composition Corrosion rate (mm / a) Inhibition efficiency (%) Blank 0.3293 / Comparative Example 1 0.1283 69.56 Comparative Example 2 0.0911 75.11 Comparative Example 3 0.0854 78.48 Example 1 0.0753 84.04 Example 2 0.0486 96.97 Example 3 0.0299 99.17 Example 4 0.0443 97.11 Example 5 0.0694 86.65 Example 6 0.0710 85.33

[0085] Table 2 shows that the single S-benzylthiourea hydrochloride corrosion inhibitor, such as Comparative Example 1, has a low corrosion inhibition rate for J55 samples. Binary corrosion inhibitors, such as the S-benzylthiourea hydrochloride compounded with hexamethylenetetramine in Comparative Example 2 and the S-benzylthiourea hydrochloride compounded with organic alkynol in Comparative Example 3, show improved corrosion inhibition effects on J55 samples compared to the single S-benzylthiourea hydrochloride. The CO2 corrosion inhibitors in Examples 1-6 are ternary compound corrosion inhibitors, exhibiting the highest corrosion inhibition rate for J55 samples. A synergistic effect exists among the three components; S-benzylthiourea hydrochloride, hexamethylenetetramine, and alkynol readily form numerous hydrogen bonds, resulting in a cross-linking effect. This mutually reinforces the chemical adsorption of the amine and the film-forming effect with the organic alkynol, making the corrosion inhibitor adsorption layer more stable and increasing the thickness of the cross-linked adsorption film on the steel surface. Meanwhile, small organic alkynol molecules can embed into the gaps between the two cyclic molecules of S-benzylthiourea hydrochloride and hexamethylenetetramine, adsorbing onto the steel surface to form a dense cross-linked adsorption film, effectively reducing the corrosion rate of the metal.

[0086] When the dosage of each component of the CO2 corrosion inhibitor in this application is different, its corrosion inhibition effect varies. Specifically, when S-benzylthiourea hydrochloride is in the range of 18%–22%, 1,4-butynediol is in the range of 18%–22%, and hexamethylenetetramine is in the range of 56%–64%, the corrosion inhibition effect reaches over 95%. This is because the three components can synergistically adsorb on the metal surface, forming a competitive relationship, which in turn affects the synergistic effect. When the components are within the above-mentioned content range, the components compete for adsorption on the metal surface to reach adsorption equilibrium, resulting in a good synergistic effect and forming a dense adsorption film on the metal surface, thus inhibiting metal corrosion. In Example 3, when S-benzylthiourea hydrochloride is 20%, 1,4-butynediol is 20%, and hexamethylenetetramine is 60%, the synergistic effect of the three components is optimal, the adsorption film formed on the metal surface is the densest, and the metal corrosion inhibition effect is the best.

[0087] 2. Electrochemical impedance spectroscopy

[0088] The testing method was as follows: a corrosion inhibitor was added to simulated formation water to obtain a test solution with a corrosion inhibitor concentration of 200 mg / L. CO2 was then introduced into the test solution until CO2 saturation. Using the CO2-saturated test solution as the electrolyte, a three-electrode system was employed for testing, with the J55 sample as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the auxiliary electrode. The test frequency ranged from 0.01 Hz to 100 kHz, and the AC amplitude was 5 mV.

[0089] Simultaneously, a blank experiment was conducted. The test solution for the blank experiment was simulated formation water without corrosion inhibitor, and the remaining steps were the same as the test method described above.

[0090] Electrochemical impedance spectroscopy was performed on the corrosion inhibitors for CO2 corrosion in Examples 1-6 and the corrosion inhibitors in Comparative Examples 1-3, respectively. The test results are as follows: Figure 2 As shown.

[0091] from Figure 2 It can be seen that the capacitive arc resistance of the S-benzylthiourea hydrochloride corrosion inhibitor in Comparative Example 1 is increased compared to the blank group, while the capacitive arc resistance of the binary corrosion inhibitors in Comparative Examples 2-3 is increased compared to the S-benzylthiourea hydrochloride corrosion inhibitor. The capacitive arc resistance of the ternary compound corrosion inhibitors in Examples 1-6 is significantly increased compared to the S-benzylthiourea hydrochloride corrosion inhibitor in Comparative Example 1 and the binary corrosion inhibitors in Comparative Examples 2-3. Among them, the ternary compound corrosion inhibitor in Example 3 has the largest capacitive arc resistance. This is because the ternary compound corrosion inhibitors in Examples 1-6 adsorb on the metal surface, forming a protective layer against electrolyte corrosive substances, thereby enhancing the resistance of the J55 sample to electrochemical corrosion. The test results are consistent with the high-voltage static plate test results, further demonstrating that the corrosion inhibitors in Examples 1-6 can effectively reduce the corrosion rate of steel, thereby extending the service life of steel.

[0092] The J55 sample was corroded for 72 hours in CO2-saturated simulated formation water without corrosion inhibitor and in CO2-saturated simulated formation water containing 200 mg / L corrosion inhibitor. The surface morphology was then observed. Figure 3 As shown.

[0093] Figure 3 In the diagram, a is the SEM image of the J55 sample from the blank experiment without corrosion inhibitor; b is the SEM image of the J55 sample with corrosion inhibitor as Comparative Example 1; c is the SEM image of the J55 sample with corrosion inhibitor as Comparative Example 2; and d is the SEM image of the J55 sample with corrosion inhibitor as Example 3. Figure 3 As can be seen, in sample a, the surface of J55 is clearly severely corroded, leaving large and deep pores; in sample b, the corrosion of J55 is reduced, with only a few pores remaining; in sample c, the surface of J55 is relatively smooth, indicating that the corrosion inhibitor in Comparative Example 2 provides good protection for the J55 sample; and in sample d, the surface of J55 is relatively smooth and flat, with a relatively clear overall surface morphology. The above test results demonstrate that in the corrosion inhibitor of this application, there is a synergistic effect between S-benzylthiourea hydrochloride, organic alkynol, and hexamethylenetetramine, resulting in excellent corrosion inhibition performance at 60℃.

[0094] The corrosion inhibition rate of existing commercial corrosion inhibitors was tested using the above method, as detailed below:

[0095] Corrosion inhibitor 1

[0096] A sodium chloride solution was prepared by mixing 20%–30% of a hydrophobic imidazoline corrosion inhibitor with a carbon chain length of C11–C17, 3%–7% thiourea, 5%–10% sodium dodecyl sulfonate, and distilled water. The solution was then subjected to a coating test at 60°C. After 72 hours, the corrosion inhibition rate of the inhibitor was 58.9%–96.7%.

[0097] Corrosion inhibitor 2

[0098] A corrosion inhibitor solution was prepared by mixing 15-50% ethylene bisoleamide or 9-heptadecenyl-N-di(aminoethyl)amide, 10-25% propynyl alcohol, 5-15% mercaptoic acid, 5-25% piperidine, 5-15% mercaptopyridine, and distilled water. The corrosion inhibition rate of the corrosion inhibitor was 92.75%-98.35%.

[0099] Corrosion inhibitor 3

[0100] 15-80% of polyoxyethylene alkylolamide (molecular formula R-CON-(C2H4O)2-(C2H4O)) n A corrosion inhibitor solution was prepared using a solvent consisting of 1-30% propynyl alcohol or 1,4-butynediol, 0.1-5% potassium iodide, 1-30% ethyleneamine, 0.1-5% antimony trioxide, and 5-60% isopropanol. A high-temperature carbon dioxide corrosion inhibition experiment was conducted, and the corrosion inhibition rate was 88.13%-91.57%.

[0101] Corrosion inhibitor 4

[0102] A corrosion inhibitor solution is prepared by mixing 20-50 parts of a modified imidazoline derivative, 10-25 parts of OP-10, 3-10 parts of hexamethylenetetramine, 2-5 parts of iodide, 6-10 parts of propynyl alcohol, and 30-60 parts of water or isopropanol solvent. The corrosion inhibition efficiency of the corrosion inhibitor composition is 91.3%-93.1%. The modified imidazoline derivative is synthesized by reacting lauric acid or oleic acid with tetraethylenepentamine or polyethylenepolyamine to obtain a first mixture; reacting the first mixture with carbon disulfide to obtain a second mixture; and mixing the second mixture with phosphorous acid to obtain the modified imidazoline derivative.

[0103] Existing corrosion inhibitors 1-4 have numerous and complex formulations, and their corrosion inhibition rates are lower than the optimal corrosion inhibition rate of the corrosion inhibitor proposed in this application. The corrosion inhibitor for inhibiting CO2 corrosion proposed in this application has fewer formulation components, lower cost, and better corrosion inhibition effect, effectively suppressing the corrosion of steel in a carbon dioxide environment.

[0104] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.

Claims

1. A corrosion inhibitor that suppresses CO2 corrosion, characterized in that, It consists of the following components by mass percentage: S-benzylthiourea hydrochloride 18%~22%; Organic alkynols 18%~20%; Hexamethylenetetramine 58%~64%; The organic alkynol is any one or a mixture of ethynol, propynol, 1,4-butynediol or methylbutynol.

2. The corrosion inhibitor for suppressing CO2 corrosion according to claim 1, characterized in that, It consists of the following components by mass percentage: S-benzylthiourea hydrochloride 20%, 1,4-butynediol 20%, hexamethylenetetramine 60%; or S-benzylthiourea hydrochloride 18%, ethynyl alcohol 18%, hexamethylenetetramine 64%; or S-Benzylthiourea hydrochloride 22%, propargyl alcohol 20%, hexamethylenetetramine 58%.

3. The method for preparing the corrosion inhibitor for inhibiting CO2 corrosion according to claim 1, characterized in that, include: Weigh out S-benzylthiourea hydrochloride, organic alkynol and hexamethylenetetramine according to the mass percentage, mix them evenly to obtain the corrosion inhibitor for CO2 corrosion.

4. The application of the corrosion inhibitor for inhibiting CO2 corrosion according to any one of claims 1-2 in the corrosion protection of steel in oil and gas fields.

5. A method for corrosion protection of steel in oil and gas fields, characterized in that, Corrosion protection of oil and gas field steel is achieved by adding the corrosion inhibitor for inhibiting CO2 corrosion as described in any one of claims 1-2 into the formation water of the oil and gas field.

6. The method for corrosion protection of steel in oil and gas fields according to claim 5, characterized in that, The concentration of the corrosion inhibitor that inhibits CO2 corrosion is 200 mg / L.

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