Composite corrosion inhibitor, preparation method and application thereof

Abstract

The application discloses a composite corrosion inhibitor and a preparation method and application thereof, relates to the technical field of corrosion inhibitors, and comprises the following components in mass fractions: 10-15 parts of a triazine derivative, 15-20 parts of a quaternary ammonium salt, 5-10 parts of thiourea, 20-30 parts of ethylene glycol, and 50-25 parts of water; wherein, the structural formula of the triazine derivative is shown as formula (I). 2‑ The triazine derivative can react with S in H2S to generate a non-toxic and harmless product such as thithiazine through a nucleophilic substitution reaction, so that H2S is efficiently and environmentally-friendly removed, the sulfur removal rate is greater than or equal to 95%, and meanwhile, the triazine derivative is compounded with the quaternary ammonium salt and the thiourea, so that the corrosion inhibition effect of the composite corrosion inhibitor on H2S / CO2 coexisting corrosion in oil and gas is further improved.

Description

Technical Field

[0001] This invention relates to the field of corrosion inhibitor technology, and in particular to a composite corrosion inhibitor, its preparation method, and its application. Background Technology

[0002] During oil and gas extraction, corrosive gases such as H2S and CO2 are often present in the extracted oil and gas. As the water / oil ratio in the produced fluids of oilfields continues to rise, these corrosive gases and water form an H2S / water / CO2 corrosion system, which causes severe corrosion to the metal structures of oil and gas wells, such as drilling strings, oil pipelines, and casings, resulting in huge economic losses.

[0003] Currently, corrosion inhibitors for H2S / CO2 coexistence corrosion mainly work by killing and inhibiting sulfate-reducing bacteria (SRB), and are not suitable for situations where the concentration of native H2S in the produced gas is high (100-1000 ppm). Summary of the Invention

[0004] The main objective of this invention is to propose a composite corrosion inhibitor, its preparation method, and its application, aiming to solve the problem that existing corrosion inhibitors for H2S / CO2 coexisting corrosion are not suitable for situations where the primary H2S concentration in the produced gas is high (100-1000 ppm).

[0005] To achieve the above objectives, the present invention proposes a composite corrosion inhibitor comprising the following components in parts by weight:

[0006] 10-15 parts of triazine derivatives, 15-20 parts of quaternary ammonium salts, 5-10 parts of thiourea, 20-30 parts of ethylene glycol, and 50-25 parts of water;

[0007] The triazine derivatives have the structural formula shown in formula (Ⅰ), where R includes C1 to C10 alkyl groups.

[0008]

[0009] In one embodiment, the quaternary ammonium salt includes at least one of hexadecyl dimethylammonium chloride, methyl phthalic acid dimethylammonium chloride, and octadecyl trimethylammonium chloride.

[0010] The present invention also provides a method for preparing the aforementioned composite corrosion inhibitor, comprising the following steps:

[0011] S10. Obtain triazine derivatives by mixing triazine derivatives with ethylene glycol and heating the mixture to obtain a first mixture.

[0012] S20. The first mixture is mixed with quaternary ammonium salt and thiourea to obtain a second mixture;

[0013] S30. Cool the second mixture and add water to mix, to obtain the composite corrosion inhibitor.

[0014] In one embodiment, step S10, the step of obtaining the triazine derivative, includes:

[0015] S01. Acetaldehyde, ethanolamine and 3-methoxypropylamine are mixed to obtain a mixture, which is then subjected to three stages of heat treatment under anaerobic conditions, followed by cooling and filtration to obtain the triazine derivative.

[0016] In one embodiment, step S01, the three-stage heat treatment includes:

[0017] The mixture is heated to 80°C at a heating rate of 2-3°C and held for 10 minutes, then heated to 90°C at a heating rate of 2-3°C and held for 2-3 hours; finally, it is heated to 110°C at a heating rate of 2-3°C and held for 1 hour.

[0018] In one embodiment, in step S01:

[0019] The mass ratio of the acetaldehyde, the ethanolamine, and the 3-methoxypropylamine is (0.8–1):(2.5–3):(1.8–2); and / or,

[0020] The mixing method includes mixing under stirring conditions at a rotation speed of 120 rpm.

[0021] In one embodiment, step S10 includes: the mixing method comprising mixing under stirring conditions for 30 minutes; the heat treatment temperature being 55–60°C; and / or,

[0022] In step S20, the mixing method includes mixing under stirring conditions for a time of 30 minutes; and / or,

[0023] In step S30, the cooling temperature is 20-25°C, and the mixing method includes mixing under stirring conditions for 20 minutes.

[0024] The present invention also provides an application in which the aforementioned composite corrosion inhibitor or the composite corrosion inhibitor prepared by the aforementioned method is used to mitigate H2S / CO2 coexistence corrosion in oil and gas.

[0025] In one embodiment, the mass concentration of H2S in the oil and gas is 100 to 1000 ppm, and the volume concentration of CO2 in the oil and gas is 5% to 95%.

[0026] In one embodiment, the mass ratio of the composite corrosion inhibitor to H2S and CO2 in the oil and gas is 1:(0.2-14).

[0027] This invention proposes a composite corrosion inhibitor, wherein a triazine derivative can react with S in H2S. 2- A nucleophilic substitution reaction occurs, generating non-toxic and harmless products such as thiadiazine, thereby efficiently and environmentally removing hydrogen sulfide (H2S). When the mass concentration of H2S in the oil and gas is 100–1000 ppm and the volume concentration of CO2 is 5%–95%, the desulfurization rate is ≥95%. Simultaneously, the triazine derivatives, combined with quaternary ammonium salts and thiourea, further enhance the inhibitory effect of the composite corrosion inhibitor on H2S / CO2 coexisting corrosion in oil and gas. This composite corrosion inhibitor uses readily available raw materials, has a simple and easy-to-operate preparation process, and high compatibility. It can form a complete and dense adsorption film on the metal surface to shield against H2S / CO2 corrosion, especially showing good corrosion inhibition effects in primary and associated gas containing relatively high concentrations of H2S (100–1000 ppm) and CO2 (5%–95%). Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram illustrating the interaction principle between triazine derivatives and hydrogen sulfide in a composite corrosion inhibitor provided in an embodiment of the present invention.

[0030] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] During oil and gas extraction, corrosive gases such as H2S and CO2 are often present in the extracted oil and gas. As the water / oil ratio in the produced fluids of oilfields continues to rise, these corrosive gases and water form an H2S / water / CO2 corrosion system, which causes severe corrosion to the metal structures of oil and gas wells, such as drilling strings, oil pipelines, and casings, resulting in huge economic losses. Specifically, taking steel pipes as an example, in a single H2S corrosion system, H2S is a strong reducing gas that can react with the steel surface to form a ferrous sulfide (FeS) film. However, the FeS film has poor protective properties and is easily dissolved or ruptured, leading to continuous corrosion. At the same time, hydrogen atoms produced by the decomposition of H2S can be adsorbed on the metal surface and diffuse into the metal lattice, weakening the mechanical properties of the metal, making it brittle and prone to fracture, also known as "hydrogen embrittlement." In a single CO2 corrosion system, CO2 dissolves in water to form carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions, resulting in a weakly acidic solution. This acidic environment accelerates the dissolution of steel, forming ferrous ions, accompanied by the release of hydrogen gas. The corrosion damage caused by the coexistence of H2S and CO2 is higher than that caused by H2S or CO2 alone. This is because H2S causes mechanical loss in the metal in the CO2 corrosion system, while CO2 lowers the pH of the H2S corrosion system, meaning that the two have a synergistic effect: (1) the hydrogen gas produced during CO2 corrosion exacerbates hydrogen embrittlement, and (2) the ferrous ions formed by CO2 corrosion react with H2S to generate more FeS, further promoting the diffusion of hydrogen atoms and exacerbating mechanical loss. In other words, H2S itself is prone to pitting and crevice corrosion, while the presence of CO2 further lowers the pH value of the local area, accelerating the formation and expansion of corrosion pits. In addition, when H2S and CO2 coexist, the instability of the FeS film increases, making it prone to rupture in local areas, exposing new metal surfaces and leading to increased local corrosion.

[0033] Currently, corrosion inhibitors for H2S / CO2 coexistence corrosion mainly work by killing and inhibiting sulfate-reducing bacteria (SRB), and are not suitable for situations where the concentration of native H2S in the produced gas is high (100-1000 ppm).

[0034] In view of this, the present invention provides a composite corrosion inhibitor comprising the following components in parts by weight:

[0035] 10-15 parts of triazine derivatives, 15-20 parts of quaternary ammonium salts, 5-10 parts of thiourea, 20-30 parts of ethylene glycol, and 50-25 parts of water;

[0036] The triazine derivatives have the structural formula shown in formula (Ⅰ), where R includes C1 to C10 alkyl groups.

[0037]

[0038] In the technical solution of this invention, the triazine derivative can react with S in H2S. 2- A nucleophilic substitution reaction occurs, generating non-toxic and harmless products such as thiadiazine, thus efficiently and environmentally removing H2S. When the mass concentration of H2S in oil and gas is 100–1000 ppm and the volume concentration of CO2 is 5%–95%, the desulfurization rate is ≥95%. Simultaneously, the triazine derivatives, combined with quaternary ammonium salts and thiourea, further enhance the inhibitory effect of the composite corrosion inhibitor on H2S / CO2 coexisting corrosion in oil and gas. This composite corrosion inhibitor uses readily available raw materials, has a simple and easy-to-operate preparation process, and high compatibility. It can form a complete and dense adsorption film on the metal surface to shield against H2S / CO2 corrosion, especially showing good corrosion inhibition effects in primary and associated gas containing relatively high concentrations of H2S (100–1000 ppm) and CO2 (5%–95%).

[0039] In some embodiments of the present invention, the quaternary ammonium salt includes at least one of hexadecyl dimethylammonium chloride, methylbenzenedimethylammonium chloride, and octadecyltrimethylammonium chloride. That is, the quaternary ammonium salt can be any one of hexadecyl dimethylammonium chloride, methylbenzenedimethylammonium chloride, and octadecyltrimethylammonium chloride, or two or three of these compounds, all within the scope of protection of the present invention. Selecting the above-mentioned quaternary ammonium salt can result in a better corrosion inhibition effect of the composite corrosion inhibitor, thereby achieving a higher corrosion inhibition rate.

[0040] The present invention also provides a method for preparing the aforementioned composite corrosion inhibitor, comprising the following steps:

[0041] S10. Obtain triazine derivatives by mixing triazine derivatives with ethylene glycol and heating the mixture to obtain a first mixture.

[0042] S20. The first mixture is mixed with quaternary ammonium salt and thiourea to obtain a second mixture;

[0043] S30. Cool the second mixture and add water to mix, to obtain the composite corrosion inhibitor.

[0044] In the technical solution of this invention, triazine derivatives and ethylene glycol are first mixed and heated to enhance the solubility of the triazine derivatives, making them easier to disperse in the solvent, thus obtaining a first mixture. Then, the first mixture is mixed with quaternary ammonium salt and thiourea to obtain a stable mixture, i.e., a second mixture. Finally, the second mixture is cooled to room temperature, resulting in more stable chemical properties. The cooled second mixture is then mixed with water to obtain a composite corrosion inhibitor. The preparation steps of the composite corrosion inhibitor of this invention are simple, low-cost, water-soluble, highly efficient, and environmentally friendly. The composite corrosion inhibitor prepared according to the steps of this invention exhibits good corrosion inhibition effects in primary and associated gases containing relatively high concentrations of H2S (100–1000 ppm) and CO2 (5%–95%).

[0045] In some embodiments of the present invention, step S10, the step of obtaining triazine derivatives includes: S01, mixing acetaldehyde, ethanolamine and 3-methoxypropylamine to obtain a mixture, performing three-stage heat treatment sequentially under anaerobic conditions, cooling, filtering, and obtaining the triazine derivatives.

[0046] In the technical solution of the present invention, the acetaldehyde, the ethanolamine and the 3-methoxypropylamine are synthesized under anaerobic and heating conditions to generate a triazine derivative of formula (I).

[0047] The method for preparing triazine derivatives of formula (I) in this invention uses readily available and inexpensive raw materials, has simple preparation steps, and achieves a high yield of triazine derivatives. The three-stage heat treatment reduces the formation of other byproducts and improves the purity and yield of the triazine derivatives.

[0048] In some embodiments of the present invention, step S01 includes the following three-stage heat treatment: heating the mixture to 80°C at a heating rate of 2-3°C and holding it at that temperature for 10 minutes; then heating it to 90°C at a heating rate of 2-3°C and holding it at that temperature for 2-3 hours; and finally heating it to 110°C at a heating rate of 2-3°C and holding it at that temperature for 1 hour.

[0049] In the technical solution of this invention, the three-stage heat treatment is a gradient heating step, that is, firstly, the mixture is slowly heated to 80°C and held at 80°C for 10 minutes to ensure that the reactants are heated to 80°C; then, the temperature is slowly increased from 80°C to 90°C and held at 90°C for 2-3 hours to ensure that the reactants are in full contact and heated, and to prevent side reactions from occurring; finally, the temperature is slowly increased from 90°C to 110°C and held at 110°C for 1 hour to ensure that the reactants react fully.

[0050] In some embodiments of the present invention, in step S01, the mass ratio of acetaldehyde, ethanolamine, and 3-methoxypropylamine is (0.8–1):(2.5–3):(1.8–2). This mass ratio ensures higher purity and yield of the obtained triazine derivatives.

[0051] In some embodiments of the present invention, in step S01, the mixing method includes mixing under stirring conditions, wherein the mixing speed is 120 rpm.

[0052] In the technical solution of this invention, the mixing methods include vortexing, stirring, and shaking. When stirring is used for mixing, the preferred mixing speed is 120 rpm. Selecting this speed ensures that acetaldehyde, ethanolamine, and 3-methoxypropylamine are mixed relatively evenly, and the contact area of ​​the three raw materials is large, which facilitates the rapid progress of the synthesis reaction.

[0053] In some embodiments of the present invention, step S10 includes: the mixing method includes mixing under stirring conditions for a mixing time of 30 min; and the heat treatment temperature is 55-60°C.

[0054] In the technical solution of this invention, the mixing methods include vortexing, stirring, and shaking. When stirring is used for mixing, the mixing time is 30 minutes. This mixing time ensures that the triazine derivative and ethylene glycol are mixed relatively evenly and sufficiently, preventing precipitation. The heat treatment temperature is 55–60°C, that is, the heat treatment temperature can be 55°C, 57°C, or 60°C. A heat treatment temperature within this range ensures that the triazine derivative and ethylene glycol are fully mixed and dissolved without reaction.

[0055] In some embodiments of the present invention, in step S20, the mixing method includes mixing under stirring conditions for a time of 30 minutes.

[0056] In the technical solution of this invention, the mixing method includes vortexing, stirring, shaking, etc. The mixing time is 30 minutes, which ensures that the first mixture and the quaternary ammonium salt and thiourea are fully mixed and that there is sufficient intermolecular contact.

[0057] In some embodiments of the present invention, in step S30, the cooling temperature is 20-25°C, and the mixing method includes mixing under stirring conditions for 20 minutes.

[0058] In the technical solution of the present invention, the cooling temperature is 20-25°C, that is, the cooling temperature can be 20°C, 22°C or 25°C. The cooling temperature within the above range can ensure that the temperature of the second mixture is low, thereby reducing the incompatibility phenomenon when the second mixture is mixed with water.

[0059] Mixing methods include vortexing, stirring, and shaking. When using stirring, the mixing time is 20 minutes. This mixing time ensures that the second mixture and water are thoroughly mixed, increasing the probability of intermolecular contact.

[0060] This invention also provides an application in which the aforementioned composite corrosion inhibitor, or the composite corrosion inhibitor prepared by the aforementioned method, is used to mitigate H2S / CO2 coexisting corrosion in oil and gas. That is, when oil and gas are introduced into water containing the composite corrosion inhibitor, the triazine derivatives in the composite corrosion inhibitor react with hydrogen sulfide in the oil and gas flow, transforming it into a non-toxic and harmless product. Figure 1 Meanwhile, the triazine derivatives, quaternary ammonium salts, thiourea, and other components in the composite corrosion inhibitor can be adsorbed onto the metal surface through polar groups, while the non-polar groups are arranged from the metal surface to the oil-water mixture system, forming a complete and dense adsorption film on the metal surface. This adsorption film can prevent H2S / CO2 in the oil and gas from contacting the metal surface and causing electrochemical corrosion. At the same time, the triazine derivatives in the composite corrosion inhibitor can react with H2S in the oil and gas, ultimately reducing the H2S content in the oil and gas.

[0061] Because the composite corrosion inhibitor prepared using the aforementioned composite corrosion inhibitor or its preparation method is used, it possesses all the beneficial effects of the aforementioned composite corrosion inhibitor or its preparation method. In this invention, the mass concentration of H2S in the oil and gas can be less than 100 ppm or within the range of 100–1000 ppm, and the volume concentration of CO2 in the oil and gas can be less than 5% or within the range of 5%–95%, in which case the composite corrosion inhibitor of this invention can be used for corrosion inhibition treatment.

[0062] In some embodiments of the present invention, the mass concentration of H2S in the oil and gas is 100 to 1000 ppm, and the volume concentration of CO2 in the oil and gas is 5% to 95%.

[0063] In the technical solution of this invention, when the mass concentration of H2S in the oil and gas is high, i.e., between 100 and 1000 ppm, and the volume concentration of CO2 in the oil and gas is between 5% and 95%, an H2S / CO2 co-corrosion system is formed. Existing corrosion inhibitors have limited effectiveness in this situation. However, the composite corrosion inhibitor of this invention has a strong corrosion inhibition effect on this co-corrosion system. When the mass concentration of H2S in the oil and gas is between 100 and 1000 ppm and the volume concentration of CO2 is between 5% and 95%, the desulfurization rate is ≥95%. Using the composite corrosion inhibitor of this invention can effectively reduce the H2S content in the oil and gas, while reducing the impact of H2S and CO2 corrosion on on-site production, lowering operational and maintenance pressure, and providing technical support for normal production.

[0064] In some embodiments of the present invention, the mass ratio of the composite corrosion inhibitor to H2S and CO2 in the oil and gas is 1:(0.2-14).

[0065] In the technical solution of the present invention, the mass ratio of the composite corrosion inhibitor to H2S and CO2 in oil and gas can be 1:0.5, 1:1, 1:5, 1:10 or 1:14. The mass ratio within the above range can ensure a good corrosion inhibition effect.

[0066] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0067] Example 1

[0068] A method for preparing a composite corrosion inhibitor includes the following steps:

[0069] S01. Preparation of triazine derivatives: (1) Add acetaldehyde, ethanolamine and 3-methoxypropylamine to a three-necked flask in a mass ratio of 1:3:2 and place it in a magnetic stirring sleeve. Connect a water separator, condenser, thermometer and helium tube to the flask. (2) After passing helium for 5 minutes, turn on the magnetic stirring sleeve and control the magnetic stirring speed to 120 rpm. Raise the temperature to 80°C at a rate of 2°C per minute and hold for 10 minutes. Continue to raise the temperature to 90°C and hold for 2 hours. Continue to raise the temperature to 110°C and react for 1 hour. Helium is continuously passed through the flask during the reaction. (3) After cooling, triazine derivatives are obtained.

[0070] S10. Add triazine derivatives and ethylene glycol to an atmospheric pressure enamel reactor in proportion, stir for 30 minutes, and slowly heat to 55°C to obtain the first mixture.

[0071] S20. While stirring, add quaternary ammonium salt and thiourea to the first mixture in proportion. After stirring continuously for 30 minutes, stop heating to obtain the second mixture.

[0072] S30. While stirring, cool the second mixture until it reaches 20°C. Add water to the cooled second mixture in proportion while stirring. After stirring for 20 minutes, the composite corrosion inhibitor is obtained.

[0073] The mass ratio of triazine derivatives, ethylene glycol, octadecyltrimethylammonium chloride, thiourea, and water is 10:20:15:5:50.

[0074] Example 2

[0075] The difference between Example 2 and Example 1 is that:

[0076] The mass ratio of triazine derivatives, ethylene glycol, quaternary ammonium salts, thiourea, and water is 15:30:20:10:25.

[0077] Example 3

[0078] The difference between Example 3 and Example 1 is that:

[0079] The mass ratio of triazine derivatives, ethylene glycol, quaternary ammonium salts, thiourea, and water is 12:25:18:7:38.

[0080] Comparative Example 1

[0081] The difference between Comparative Example 1 and Example 1 is that:

[0082] In S10, triazine derivatives and octadecyltrimethylammonium chloride are added to an atmospheric pressure enamel reactor in proportion, stirred for 30 minutes, and then slowly heated to 55°C to obtain the first mixture.

[0083] In S20, while stirring, thiourea and ethylene glycol are added to the first mixture in proportion. After stirring continuously for 30 minutes, heating is stopped to obtain the second mixture.

[0084] In S30, the second mixture is cooled to 20°C while being stirred. Water is then added to the cooled second mixture in proportion while stirring. After stirring for 20 minutes, a composite corrosion inhibitor is obtained.

[0085] Comparative Example 2

[0086] This comparative example provides an existing corrosion inhibitor, and the specific preparation steps are as follows:

[0087] S10. After adding 300 kg of water to the reactor, start the stirrer;

[0088] S20, heat the temperature to 50℃, and add 270kg of oleic acid-based hydroxyethyl imidazoline;

[0089] S30. Stir for 30 minutes to mix thoroughly. While stirring, add 270 kg of dodecyl dimethyl benzyl ammonium chloride, 80 kg of aminotrimethylphosphonic acid, and 80 kg of hydroxyethylidene diphosphonic acid.

[0090] S40, stir for 30 minutes to mix evenly, then take samples for testing and package.

[0091] Performance testing

[0092] The composite corrosion inhibitors obtained in Examples 1-3 were tested according to the test procedures recorded in Appendix B.6.2 of the "Technical Specification for Corrosion and Scale Inhibitors for Oilfield Water Treatment" (Q / SY 17126-2019), specifically the determination of corrosion rate in simulated field water containing H2S and CO2. The preparation method for simulated field water containing 500ppm H2S and 30% CO2 was as follows: based on the ion content of the field water, the mass of each substance required to prepare 1L of simulated field water was calculated, and the simulated field water was prepared in sequence. The metal pipe was made of N80 material, and the amount of composite corrosion inhibitor added was 100ppm. The formula for calculating the corrosion inhibition rate is:

[0093]

[0094] In the formula: η is the corrosion inhibition rate, %;

[0095] The average corrosion rate of the blank water sample is given in mm / a.

[0096] The average corrosion rate of the water sample with added corrosion inhibitor is expressed in mm / a.

[0097] The measurement results are shown in Table 1.

[0098] Table 1 shows the corrosion inhibition effect of the composite corrosion inhibitors in Examples 1-3.

[0099]

[0100] Table 1 shows that the composite corrosion inhibitor in Comparative Example 1, which was not prepared in the required order, had poor compatibility and precipitated after standing, making it impossible to conduct corrosion inhibition and desulfurization effect evaluation experiments. The corrosion inhibitor prepared in Comparative Example 2, after experimental evaluation, had a corrosion inhibition rate of only 64.52%, less than 70%, failing to meet the standard requirements, and had no desulfurization effect. In Examples 1-3, the composite corrosion inhibitors were all prepared in the required proportions and order. After corrosion inhibition effect evaluation experiments, the corrosion inhibition rates were all greater than 85%, meeting the standard requirements: corrosion inhibition rate ≥ 70% and desulfurization rate ≥ 95%, proving that the composite corrosion inhibitor had good corrosion inhibition and desulfurization effects.

[0101] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A composite corrosion inhibitor, characterized in that, The components include the following parts by mass: 10-15 parts of triazine derivatives, 15-20 parts of quaternary ammonium salts, 5-10 parts of thiourea, 20-30 parts of ethylene glycol, and 50-25 parts of water; The triazine derivatives have the structural formula shown in formula (Ⅰ), where R includes C1 to C10 alkyl groups.

2. The composite corrosion inhibitor as described in claim 1, characterized in that, The quaternary ammonium salt includes at least one of hexadecyl dimethylammonium chloride, methyl phthalic acid dimethylammonium chloride, and octadecyl trimethylammonium chloride.

3. A method for preparing the composite corrosion inhibitor as described in claim 1 or 2, characterized in that, Includes the following steps: S10. Obtain triazine derivatives by mixing triazine derivatives with ethylene glycol and heating the mixture to obtain a first mixture. S20. The first mixture is mixed with quaternary ammonium salt and thiourea to obtain a second mixture; S30. Cool the second mixture and add water to mix, to obtain the composite corrosion inhibitor.

4. The method for preparing the composite corrosion inhibitor as described in claim 3, characterized in that, In step S10, the step of obtaining triazine derivatives includes: S01. Acetaldehyde, ethanolamine and 3-methoxypropylamine are mixed to obtain a mixture, which is then subjected to three stages of heat treatment under anaerobic conditions, followed by cooling and filtration to obtain the triazine derivative.

5. The method for preparing the composite corrosion inhibitor as described in claim 4, characterized in that, In step S01, the three-stage heat treatment includes: The mixture is heated to 80°C at a heating rate of 2-3°C and held for 10 minutes, then heated to 90°C at a heating rate of 2-3°C and held for 2-3 hours; finally, it is heated to 110°C at a heating rate of 2-3°C and held for 1 hour.

6. The method for preparing the composite corrosion inhibitor as described in claim 4, characterized in that, In step S01: The mass ratio of the acetaldehyde, the ethanolamine, and the 3-methoxypropylamine is (0.8–1):(2.5–3):(1.8–2); and / or, The mixing method includes mixing under stirring conditions at a rotation speed of 120 rpm.

7. The method for preparing the composite corrosion inhibitor as described in claim 3, characterized in that, Step S10 includes: the mixing method comprising mixing under stirring conditions for 30 minutes; the heat treatment temperature being 55–60°C; and / or, In step S20, the mixing method includes mixing under stirring conditions for a time of 30 minutes; and / or, In step S30, the cooling temperature is 20-25°C, and the mixing method includes mixing under stirring conditions for 20 minutes.

8. An application characterized in that, The composite corrosion inhibitor as described in any one of claims 1 to 2, or the composite corrosion inhibitor prepared by the method described in any one of claims 3 to 7, is used to mitigate H2S / CO2 coexistence corrosion in oil and gas.

9. The application as described in claim 8, characterized in that, The mass concentration of H2S in the oil and gas is 100-1000 ppm, and the volume concentration of CO2 in the oil and gas is 5%-95%.

10. The application as described in claim 8, characterized in that, The mass ratio of the composite corrosion inhibitor to H2S and CO2 in the oil and gas is 1:(0.2-14).

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