Corrosion inhibitor for inhibiting corrosion of injection-production system of CO2 injection oil displacement system

Abstract

The invention discloses a corrosion inhibitor for inhibiting corrosion of an injection-production system of a CO2 injection oil displacement system, and relates to the technical field of corrosion inhibitors, the corrosion inhibitor comprises the following raw materials by weight: 10-30 parts of a corrosion inhibitor active matter, 2-6 parts of a surfactant, and 60-80 parts of a solvent; the preparation method of the corrosion inhibitor active matter comprises the following steps: sequentially carrying out a dehydration reaction and a cyclization reaction on thiophene-2, 5-dicarboxylic acid, tetraethylenepentamine and xylene in a reaction container, then adding thiourea, and carrying out a reaction at 138-162 DEG C for 5-15 h to prepare the corrosion inhibitor active matter. By designing a stable and efficient corrosion inhibitor active matter structure and combining a synergistic effect mechanism of the surfactant, the performance of the corrosion inhibitor for inhibiting corrosion of an injection-production system of a CO2 injection oil displacement system is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion inhibitors, and in particular to a corrosion inhibitor for inhibiting corrosion of an injection-production system of a CO2 injection oil recovery system. Background Art

[0002] While CO2 flooding is widely used to enhance oil recovery, CO2 injection significantly enhances crude oil mobility and recovery efficiency. However, it also creates serious corrosion issues. CO2 reacts with water in the injection and production system to produce carbonic acid, creating an acidic environment that can easily lead to accelerated corrosion of metal materials in pipelines, wellbores, and injection systems. This corrosion is particularly severe under complex operating conditions such as high temperature, high pressure, and the presence of H2S, posing a significant threat to equipment safety and operational efficiency.

[0003] To address these issues, the current mainstream technical approach is to add corrosion inhibitors, which form a dense protective film on the metal surface to slow down the CO2-induced corrosion reaction. These inhibitors typically contain nitrogen- or sulfur-containing organic ligands, such as imidazolines, quaternary ammonium salts, or thiol derivatives. Some products also incorporate surfactants to enhance diffusion and adsorption. However, existing corrosion inhibitors still have numerous drawbacks. Firstly, they have poor thermal stability under high temperature and pressure, making them prone to degradation and resulting in an unstable protective film. Secondly, some corrosion inhibitors have complex molecular structures, cumbersome synthesis steps, and high costs, which limit their large-scale industrial application.

[0004] Therefore, how to develop a new type of corrosion inhibitor with excellent corrosion inhibition performance has become a key technical problem that needs to be broken through in the field of corrosion control of CO2 injection oil recovery system. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a corrosion inhibitor for inhibiting the corrosion of the injection and production system of the CO2 injection flooding system. By designing a stable and efficient corrosion inhibitor active substance structure and combining it with the synergistic mechanism of surfactants, the performance of the corrosion inhibitor in inhibiting the corrosion of the injection and production system of the CO2 injection flooding system is significantly improved.

[0006] The present invention proposes a corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 injection flooding system, characterized by comprising the following raw materials in parts by weight: 10-30 parts of a corrosion inhibitor active substance, 2-6 parts of a surfactant, and 60-80 parts of a solvent; The structural formula of the corrosion inhibitor active substance is as follows: .

[0007] Preferably, the preparation method of the corrosion inhibitor active material is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 138-162° C. for 5-15 hours to obtain the corrosion inhibitor active material.

[0008] Preferably, the molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea is 1:2-3:2-2.5.

[0009] Preferably, the dehydration reaction temperature is 120-140° C., and the time is 1-3 hours.

[0010] Preferably, the cyclization reaction temperature is 160-220° C., and the time is 5-10 h.

[0011] Preferably, the water-carrying agent is toluene or xylene, and the added amount of the water-carrying agent is 20-35% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0012] Preferably, the surfactant is composed of sodium dodecyl diphenyl oxide disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 2:1-4.

[0013] Preferably, the solvent consists of an organic solvent and water in a volume ratio of 1:3-5.

[0014] Preferably, the organic solvent is one or more of methanol, ethanol, ethylene glycol and N,N-dimethylformamide.

[0015] Beneficial technical effects of the present invention: (1) The present invention introduces a nitrogen-sulfur heterocyclic structure obtained by the reaction of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea by designing a corrosion inhibitor active substance with a chelating and conjugated structure. On the one hand, this structure has multiple amino and thiourea groups on the main chain of the molecule, and has a strong electron donor ability. It can quickly form a stable coordination adsorption layer on the metal surface, effectively isolating the contact between CO2 and the metal interface; on the other hand, the conjugated structure of the thiophene ring enhances the chemical stability of the molecule in a high-temperature and high-pressure CO2 environment, ensuring that it is not easy to decompose in a complex injection and production environment, and significantly improving the continuity and density of the adsorption film. Traditional corrosion inhibitors are mostly simple amine or imidazoline structures with a single molecular configuration. They are easily affected by shear and high-temperature decomposition and are difficult to maintain effective protection during long-term oil recovery. The heterocyclic multi-site corrosion inhibitor active substance constructed by the present invention not only has higher thermal stability, but its molecular structure also facilitates the formation of a more solid adsorption interface layer on the metal surface, significantly improving the CO2 corrosion protection effect.

[0016] (2) The corrosion inhibitor of the present invention also includes a surfactant, and is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate, which can not only reduce the aggregation and sedimentation risks of the corrosion inhibitor in the injection and production system, but also improve its directional arrangement ability at the interface, so that the corrosion inhibitor active molecules form an orderly arranged dense film layer when adsorbed on the metal surface, thereby improving the integrity and shear resistance of the protective film; and the surfactant synergistic mechanism introduced by the present invention not only realizes intermolecular synergistic adsorption, but also further enhances the coverage effect of the metal surface through electrostatic action and hydrophobic chain reconstruction.

[0017] (3) In a simulated corrosion test at a CO2 partial pressure of 3.5 MPa, a temperature of 95°C, and a corrosion inhibitor concentration of 200 ppm, the corrosion inhibition rate of the corrosion inhibitor of the present invention on N80 steel reached over 95%. DETAILED DESCRIPTION

[0018] The present invention will be further explained below with reference to specific embodiments.

[0019] The sodium dodecyl diphenyl ether disulfonate of the present invention was purchased from Guangzhou Yuanzheng Chemical Co., Ltd.; the structural formula of sodium N,N'-bis(lauroyl)ethylenediamine dipropionate is as follows: .

[0020] Example 1

[0021] 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor for inhibiting the corrosion of the injection and production system of the CO2 injection flooding system, which was recorded as A1.

[0022] The structural formula of the corrosion inhibitor active substance is as follows: .

[0023] The preparation method of the corrosion inhibitor active material is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 155° C. for 10 hours to obtain the corrosion inhibitor active material.

[0024] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea is 1:2.4:2.2; the temperature of the dehydration reaction is 132°C and the time is 2 hours; the temperature of the cyclization reaction is 195°C and the time is 8 hours; the water-carrying agent is xylene, and the amount of the water-carrying agent added is 28% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0025] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 1:1.

[0026] The solvent consisted of ethanol and water in a volume ratio of 1:4.

[0027] Example 2

[0028] 10 parts of corrosion inhibitor active material, 2 parts of surfactant and 60 parts of solvent were mixed to obtain a corrosion inhibitor for inhibiting the corrosion of the injection and production system of the CO2 injection flooding system, which was recorded as A2.

[0029] The preparation method of the corrosion inhibitor active material is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 138° C. for 15 hours to obtain the corrosion inhibitor active material.

[0030] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea is 1:2.2:2.1; the temperature of the dehydration reaction is 120°C and the time is 3 hours; the temperature of the cyclization reaction is 160°C and the time is 10 hours; the water-carrying agent is xylene, and the amount of the water-carrying agent added is 20% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0031] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 2:1.

[0032] The solvent is composed of ethylene glycol and water in a volume ratio of 1:3.

[0033] Example 3

[0034] 30 parts of corrosion inhibitor active material, 6 parts of surfactant and 80 parts of solvent were mixed to obtain a corrosion inhibitor for inhibiting the corrosion of the injection and production system of the CO2 injection flooding system, which was recorded as A3.

[0035] The preparation method of the corrosion inhibitor active material is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 162° C. for 5 hours to obtain the corrosion inhibitor active material.

[0036] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea is 1:3:2.5; the temperature of the dehydration reaction is 140°C and the time is 1 hour; the temperature of the cyclization reaction is 220°C and the time is 5 hours; the water-carrying agent is xylene, and the amount of the water-carrying agent added is 35% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0037] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 1:2.

[0038] The solvent consisted of methanol and water in a volume ratio of 1:5.

[0039] Comparative Example 1

[0040] 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor, which was recorded as A4.

[0041] Wherein, the surfactant is sodium dodecyl diphenyl ether disulfonate.

[0042] The remaining conditions are the same as those in Example 1.

[0043] Comparative Example 2

[0044] 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor, which was recorded as A5.

[0045] The surfactant is sodium N,N'-bis(lauroyl)ethylenediamine dipropionate.

[0046] The remaining conditions are the same as those in Example 1.

[0047] Comparative Example 3

[0048] 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor, which was recorded as A6.

[0049] The structural formula of the corrosion inhibitor active substance is as follows: .

[0050] The preparation method of the corrosion inhibitor active material is as follows: oleic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 155° C. for 10 hours to obtain the corrosion inhibitor active material.

[0051] Among them, the molar ratio of oleic acid, tetraethylenepentamine and thiourea is 1:1.2:1.1; the temperature of the dehydration reaction is 132°C and the time is 2 hours; the temperature of the cyclization reaction is 195°C and the time is 8 hours; the water-carrying agent is xylene, and the amount of the water-carrying agent added is 28% of the total mass of oleic acid and tetraethylenepentamine.

[0052] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 1:1.

[0053] The solvent consisted of ethanol and water in a volume ratio of 1:4.

[0054] Comparative Example 4 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor, which was recorded as A7.

[0055] Wherein, the surfactant is sodium dodecyl diphenyl ether disulfonate.

[0056] The remaining conditions are the same as those in Comparative Example 3.

[0057] Comparative Example 5 20 parts of corrosion inhibitor active material, 4 parts of surfactant and 70 parts of solvent were mixed to obtain a corrosion inhibitor, which was recorded as A8.

[0058] The surfactant is sodium N,N'-bis(lauroyl)ethylenediamine dipropionate.

[0059] The remaining conditions are the same as those in Comparative Example 3.

[0060] In a simulated corrosion test with a CO2 partial pressure of 3.5 MPa, a temperature of 95°C, and a corrosion inhibitor concentration of 200 ppm, the corrosion inhibition rates of the corrosion inhibitors prepared in Examples 1-3 and Comparative Examples 1-5 were measured using N80 steel as the material. The test results are shown in Table 1.

[0061] Table 1 Corrosion inhibition performance evaluation results Group Corrosion inhibition rate (%) Example 1 95.83 Example 2 92.45 Example 3 93.71 Comparative Example 1 80.46 Comparative Example 2 83.15 Comparative Example 3 81.44 Comparative Example 4 78.29 Comparative Example 5 82.03 It can be seen from the test results of Examples 1-3 in Table 1 that the corrosion inhibitor prepared by the present invention has an excellent corrosion inhibition effect, among which the corrosion inhibition rate of corrosion inhibitor A1 reaches more than 95%. This is because the present invention introduces a nitrogen-containing sulfur heterocyclic structure obtained by the reaction of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea by designing a corrosion inhibitor active substance with a chelating and conjugated structure. On the one hand, this structure has multiple amino and thiourea groups on the main chain of the molecule, has a strong electron donor ability, can quickly form a stable coordination adsorption layer on the metal surface, and effectively isolate the contact between CO2 and the metal interface; on the other hand, the conjugated structure of the thiophene ring enhances the chemical stability of the molecule in a high-temperature and high-pressure CO2 environment, ensuring that it is not easily decomposed in a complex injection and production environment, significantly improving the continuity and density of the corrosion inhibition film. Traditional corrosion inhibitors are mostly simple amine or imidazoline structures with a single molecular configuration. They are easily affected by shear and high-temperature decomposition, and it is difficult to maintain effective protection during long-term oil displacement processes. The heterocyclic multi-site corrosion inhibitor active substance constructed in the present invention not only has higher thermal stability, but its molecular structure also facilitates the formation of a stronger adsorption interface layer on the metal surface, significantly improving the CO2 corrosion prevention and control capabilities.

[0062] It can be seen from the test results of Example 1 and Comparative Examples 1-2 in Table 1 that the surfactant of the present invention is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate, which can not only reduce the aggregation and sedimentation risks of the corrosion inhibitor in the injection-production system, but also improve its directional arrangement ability at the interface, so that the corrosion inhibitor active molecules form an orderly arranged dense film layer when adsorbed on the metal surface, thereby improving the integrity and shear resistance of the protective film; and the surfactant synergistic mechanism introduced by the present invention not only realizes intermolecular synergistic adsorption, but also further enhances the coverage effect of the metal surface through electrostatic action and hydrophobic chain reconstruction, that is, the surfactant of the present invention has a synergistic promoting effect in improving the corrosion inhibition performance of the corrosion inhibitor.

[0063] It can be seen from the test results of Example 1 and Comparative Examples 3-5 in Table 1 that when an oleic acid-based corrosion inhibitor is used instead of the corrosion inhibitor active material of the present invention, even if the surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate, the corrosion inhibition performance is very different from that of the corrosion inhibitor of Example 1 of the present invention. This is because when the corrosion inhibitor active material is an oleic acid-based corrosion inhibitor, the synergistic promotion effect of the surfactant cannot be exerted. This further explains that the reason why the corrosion inhibitor of the present invention has such a high corrosion inhibition rate is the result of the combined action of the corrosion inhibitor active material and the surfactant of the present invention.

[0064] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents, and all should be included in the scope of protection of the present application.

Claims

1. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system, characterized in that: The raw materials include the following parts by weight: 10-30 parts of corrosion inhibitor active material, 2-6 parts of surfactant, and 60-80 parts of solvent; The structural formula of the corrosion inhibitor active substance is as follows: .

2. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 1, characterized in that: The preparation method of the corrosion inhibitor active material is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are sequentially subjected to dehydration reaction and cyclization reaction in a reaction container, and then thiourea is added and reacted at 138-162° C. for 5-15 hours to obtain the corrosion inhibitor active material.

3. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 2, characterized in that: The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and thiourea is 1:2-3:2-2.

5.

4. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 2, characterized in that: The dehydration reaction temperature is 120-140°C and the time is 1-3 hours.

5. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 2, characterized in that: The cyclization reaction temperature is 160-220°C and the time is 5-10 hours.

6. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 2, characterized in that: The water-carrying agent is toluene or xylene, and the added amount of the water-carrying agent is 20-35% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

7. The corrosion inhibitor for inhibiting corrosion of the injection and production system of the CO2 flooding system according to claim 1, characterized in that: The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a mass ratio of 2:1-4.

8. The corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 1, characterized in that: The solvent consists of an organic solvent and water in a volume ratio of 1:3-5.

9. A corrosion inhibitor for inhibiting corrosion of the injection and production system of a CO2 flooding system according to claim 8, characterized in that: The organic solvent is one or more of methanol, ethanol, ethylene glycol and N,N-dimethylformamide.

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