A corrosion inhibitor for suppressing corrosion in CO2 flooding systems.

Abstract

This invention discloses a corrosion inhibitor for suppressing corrosion in CO2 flooding oil injection systems, relating to the field of corrosion inhibitor technology. The corrosion inhibitor comprises the following raw materials in parts by weight: 10-30 parts of corrosion inhibitor active ingredient, 2-6 parts of surfactant, and 60-80 parts of solvent. The preparation method of the corrosion inhibitor active ingredient is as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and xylene are subjected to dehydration and cyclization reactions sequentially in a reaction vessel, followed by the addition of thiourea. The reaction is carried out at 138-162°C for 5-15 hours to obtain the corrosion inhibitor active ingredient. This invention significantly improves the corrosion inhibition performance of the corrosion inhibitor in CO2 flooding oil injection systems by designing a stable and efficient corrosion inhibitor active ingredient structure and combining it with the synergistic effect mechanism of surfactant.

Description

Technical Field

[0001] This invention relates to the field of corrosion inhibitors, and more particularly to a corrosion inhibitor for suppressing corrosion in CO2 flooding systems. Background Technology

[0002] With the widespread application of CO2-enhanced oil recovery technology, CO2 injection has greatly improved crude oil liquidity and recovery efficiency. However, it has also brought serious corrosion problems. CO2 reacts with water in the injection-production system to form carbonic acid, creating an acidic environment that easily leads to accelerated corrosion of metallic materials in pipelines, wellbores, and injection / distribution systems. This corrosion is particularly severe under complex conditions such as high temperature, high pressure, and H2S content, posing a significant threat to equipment safety and operational efficiency.

[0003] To address these issues, the mainstream technical approach is to add corrosion inhibitors, which form a dense protective film on the metal surface to slow down the corrosion reaction caused by CO2. 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 several drawbacks: firstly, they exhibit poor thermal stability under high temperature and pressure, making them prone to degradation and resulting in an unstable protective film; secondly, some inhibitors have complex molecular structures, require cumbersome synthesis steps, and are costly, limiting 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 urgently needs to be solved in the field of corrosion control of CO2-driven oil recovery systems. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, this invention proposes a corrosion inhibitor for inhibiting corrosion in CO2 flooding oil injection systems. By designing a stable and efficient corrosion inhibitory active structure and combining it with the synergistic mechanism of surfactants, the corrosion inhibitor significantly improves the performance of the corrosion inhibitor in inhibiting corrosion in CO2 flooding oil injection systems.

[0006] The present invention proposes a corrosion inhibitor for inhibiting corrosion in CO2 flooding oil injection systems, characterized in that it comprises the following raw materials in parts by weight: 10-30 parts of corrosion inhibitory active ingredient, 2-6 parts of surfactant, and 60-80 parts of solvent; 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.

[0007] The structural formula of the corrosion inhibitor is as follows: .

[0008] Preferably, the corrosion inhibitor is prepared as follows: thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 138-162℃ for 5-15 hours to obtain the corrosion inhibitor.

[0009] Preferably, the molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea is 1:2-3:2-2.5.

[0010] Preferably, the dehydration reaction is carried out at a temperature of 120-140℃ for 1-3 hours.

[0011] Preferably, the cyclization reaction is carried out at a temperature of 160-220℃ for 5-10 hours.

[0012] Preferably, the water-carrying agent is toluene or xylene, and the amount of water-carrying agent added is 20-35% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0013] Preferably, 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.

[0014] Preferably, the solvent is composed of an organic solvent and water in a volume ratio of 1:3-5.

[0015] Preferably, the organic solvent is one or more of methanol, ethanol, ethylene glycol and N,N-dimethylformamide.

[0016] Beneficial technical effects of the present invention:

[0017] (1) This invention introduces a nitrogen-sulfur heterocyclic structure obtained by reacting thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea into a corrosion inhibitor with chelating and conjugated structures. This structure has multiple amino and thiourea groups on the main molecular chain, giving it a strong electron-donating ability and enabling it to quickly form a stable coordination adsorption layer on the metal surface, effectively isolating CO2 from contact with the metal interface. On the other hand, the conjugated structure of the thiophene ring enhances the chemical stability of the molecule under high temperature and high pressure CO2 environment, ensuring that it is not easily decomposed in complex injection and production environments, and significantly improving the continuity and density of the adsorption film. Traditional corrosion inhibitors are mostly simple amine or imidazoline structures with single molecular configurations, which are easily affected by shear and high temperature decomposition, making it difficult to maintain effective protection during long-term oil displacement. However, the heterocyclic multi-site corrosion inhibitor constructed in this invention not only has higher thermal stability, but its molecular structure also facilitates the formation of a more robust adsorption interface layer on the metal surface, significantly improving the CO2 corrosion protection effect.

[0018] (2) The corrosion inhibitor of the present invention also includes a surfactant, which is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate. It can not only reduce the risk of aggregation and sedimentation 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 and dense film layer when adsorbed on the metal surface, thereby improving the integrity and shear resistance of the protective film. The surfactant synergistic mechanism introduced in the present invention not only realizes the intermolecular synergistic adsorption, but also further enhances the coverage effect on the metal surface through electrostatic interaction and hydrophobic chain reconstruction.

[0019] (3) 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 rate of N80 steel reached over 95%. Detailed Implementation

[0020] The present invention will be further explained below with reference to specific embodiments.

[0021] The sodium dodecyl diphenyl ether disulfonate of this invention was purchased from Guangzhou Yuanzheng Chemical Co., Ltd.; the structural formula of sodium N,N'-bis(lauroyl)ethylenediamine dipropionate is as follows: .

[0022] Example 1

[0023] A corrosion inhibitor, denoted as A1, is obtained by mixing 20 parts of corrosion inhibitory active material, 4 parts of surfactant and 70 parts of solvent to inhibit corrosion of the injection and production system in CO2 oil displacement system.

[0024] The structural formula of the corrosion inhibitor is as follows: .

[0025] The corrosion inhibitor is prepared as follows: Thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 155℃ for 10 h to obtain the corrosion inhibitor.

[0026] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea is 1:2.4:2.2; the dehydration reaction temperature is 132℃ and the time is 2h; the cyclization reaction temperature is 195℃ and the time is 8h; the water-carrying agent is xylene, and the amount of water-carrying agent added is 28% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0027] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a 1:1 mass ratio.

[0028] The solvent consists of ethanol and water in a volume ratio of 1:4.

[0029] Example 2

[0030] A corrosion inhibitor, denoted as A2, is obtained by mixing 10 parts of corrosion inhibitory active material, 2 parts of surfactant and 60 parts of solvent to inhibit corrosion of the injection and production system in CO2 oil displacement system.

[0031] The corrosion inhibitor is prepared as follows: Thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 138°C for 15 hours to obtain the corrosion inhibitor.

[0032] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea is 1:2.2:2.1; the dehydration reaction temperature is 120℃ and the time is 3h; the cyclization reaction temperature is 160℃ and the time is 10h; the water-carrying agent is xylene, and the amount of water-carrying agent added is 20% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0033] 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.

[0034] The solvent consists of ethylene glycol and water in a volume ratio of 1:3.

[0035] Example 3

[0036] A corrosion inhibitor, denoted as A3, was obtained by mixing 30 parts of corrosion inhibitory active material, 6 parts of surfactant and 80 parts of solvent to inhibit corrosion of the injection and production system in CO2 flooding oil recovery system.

[0037] The corrosion inhibitor is prepared as follows: Thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 162℃ for 5 hours to obtain the corrosion inhibitor.

[0038] The molar ratio of thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea is 1:3:2.5; the dehydration reaction temperature is 140℃ and the time is 1h; the cyclization reaction temperature is 220℃ and the time is 5h; the water-carrying agent is xylene, and the amount of water-carrying agent added is 35% of the total mass of thiophene-2,5-dicarboxylic acid and tetraethylenepentamine.

[0039] 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.

[0040] The solvent consists of methanol and water in a volume ratio of 1:5.

[0041] Comparative Example 1

[0042] Mix 20 parts of corrosion inhibitor, 4 parts of surfactant and 70 parts of solvent to obtain corrosion inhibitor, denoted as A4.

[0043] The surfactant is sodium dodecyl diphenyl ether disulfonate.

[0044] All other conditions are the same as in Example 1.

[0045] Comparative Example 2

[0046] Mix 20 parts of corrosion inhibitor, 4 parts of surfactant and 70 parts of solvent to obtain corrosion inhibitor, denoted as A5.

[0047] The surfactant is sodium N,N'-bis(lauroyl)ethylenediamine dipropionate.

[0048] All other conditions are the same as in Example 1.

[0049] Comparative Example 3

[0050] Mix 20 parts of corrosion inhibitor, 4 parts of surfactant and 70 parts of solvent to obtain corrosion inhibitor, denoted as A6.

[0051] The structural formula of the corrosion inhibitor is as follows: .

[0052] The corrosion inhibitor is prepared as follows: oleic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 155℃ for 10 hours to obtain the corrosion inhibitor.

[0053] The molar ratio of oleic acid, tetraethylenepentamine, and thiourea is 1:1.2:1.1; the dehydration reaction temperature is 132℃ and the time is 2h; the cyclization reaction temperature is 195℃ and the time is 8h; the water-carrying agent is xylene, and the amount of water-carrying agent added is 28% of the total mass of oleic acid and tetraethylenepentamine.

[0054] The surfactant is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate in a 1:1 mass ratio.

[0055] The solvent consists of ethanol and water in a volume ratio of 1:4.

[0056] Comparative Example 4

[0057] Mix 20 parts of corrosion inhibitor, 4 parts of surfactant and 70 parts of solvent to obtain corrosion inhibitor, denoted as A7.

[0058] The surfactant is sodium dodecyl diphenyl ether disulfonate.

[0059] All other conditions are the same as those in Comparative Example 3.

[0060] Comparative Example 5

[0061] A corrosion inhibitor, denoted as A8, is obtained by mixing 20 parts of corrosion inhibitor, 4 parts of surfactant, and 70 parts of solvent.

[0062] The surfactant is sodium N,N'-bis(lauroyl)ethylenediamine dipropionate.

[0063] All other conditions are the same as those in Comparative Example 3.

[0064] 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, using N80 steel as the material, the corrosion inhibition rate of the corrosion inhibitors prepared in Examples 1-3 and Comparative Examples 1-5 was determined. The test results are shown in Table 1.

[0065] Table 1 Evaluation results of corrosion inhibition performance

[0066] 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

[0067] As can be seen from the experimental results of Examples 1-3 in Table 1, the corrosion inhibitors prepared by this invention have excellent corrosion inhibition effects, with the corrosion inhibition rate of corrosion inhibitor A1 reaching over 95%. This is because this invention introduces a nitrogen-sulfur heterocyclic structure obtained by reacting thiophene-2,5-dicarboxylic acid, tetraethylenepentamine, and thiourea into a corrosion-inhibiting active material with chelating and conjugated structures. This structure, on the one hand, has multiple amino and thiourea groups on the main molecular chain, possessing extremely strong electron-donating ability, enabling it to rapidly form a stable coordination adsorption layer on the metal surface, effectively isolating CO2 from contact with the metal interface; on the other hand, the conjugated structure of the thiophene ring enhances the chemical stability of the molecule under high temperature and high pressure CO2 environment, ensuring that it is not easily decomposed in complex injection and production environments, significantly improving the continuity and density of the corrosion-inhibiting film. Traditional corrosion inhibitors are mostly simple amine or imidazoline structures with a single molecular configuration, which are easily affected by shearing and high-temperature decomposition, making it difficult to maintain effective protection during long-term oil displacement. However, the heterocyclic multi-site corrosion inhibitor constructed in this invention not only has higher thermal stability, but its molecular structure also facilitates the formation of a more robust adsorption interface layer on the metal surface, significantly improving the ability to control CO2 corrosion.

[0068] As can be seen from the experimental results of Example 1 and Comparative Examples 1-2 in Table 1, the surfactant of the present invention is composed of sodium dodecyl diphenyl ether disulfonate and sodium N,N'-bis(lauroyl)ethylenediamine dipropionate. It can not only reduce the risk of aggregation and sedimentation of corrosion inhibitors in injection and production systems, but also improve their directional arrangement ability at the interface, so that the corrosion inhibitor molecules form an ordered and dense film layer when adsorbed on the metal surface, thereby improving the integrity and shear resistance of the protective film. Furthermore, the surfactant synergistic mechanism introduced in the present invention not only realizes intermolecular synergistic adsorption, but also further enhances the coverage effect on the metal surface through electrostatic interaction and hydrophobic chain reconstruction. That is, the surfactant of the present invention has a synergistic promoting effect on improving the corrosion inhibition performance of corrosion inhibitors.

[0069] As can be seen from the test results of Example 1 and Comparative Examples 3-5 in Table 1, 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 significantly different from that of the corrosion inhibitor in Example 1 of the present invention. This is because when the corrosion inhibitor active material is an oleic acid-based corrosion inhibitor, the synergistic promoting effect of the surfactant cannot be exerted. This further illustrates that the reason why the corrosion inhibitor of the present invention has such a high corrosion inhibition rate is the result of the combined effect of the composition of the corrosion inhibitor active material and the surfactant of the present invention.

[0070] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A corrosion inhibitor for suppressing corrosion in a CO2-enhanced oil recovery system, characterized in that, The raw materials comprise, by weight, 10-30 parts of corrosion inhibitor, 2-6 parts of surfactant, and 60-80 parts of solvent; wherein 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; the structural formula of the corrosion inhibitor is as follows: .

2. The corrosion inhibitor for suppressing corrosion in a CO2-assisted oil recovery system according to claim 1, characterized in that, The corrosion inhibitor is prepared as follows: Thiophene-2,5-dicarboxylic acid, tetraethylenepentamine and a water-carrying agent are subjected to dehydration and cyclization reactions in a reaction vessel in sequence, and then thiourea is added. The reaction is carried out at 138-162℃ for 5-15 hours to obtain the corrosion inhibitor.

3. The corrosion inhibitor for suppressing corrosion in a CO2-assisted oil recovery 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. The corrosion inhibitor for suppressing corrosion in a CO2-assisted oil recovery system according to claim 2, characterized in that, The dehydration reaction is carried out at a temperature of 120-140℃ for 1-3 hours.

5. A corrosion inhibitor for suppressing corrosion in a CO2-assisted oil recovery system according to claim 2, characterized in that, The cyclization reaction takes place at a temperature of 160-220℃ for 5-10 hours.

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

7. The corrosion inhibitor for suppressing corrosion in a CO2-assisted oil recovery system according to claim 1, characterized in that, The solvent is composed of an organic solvent and water in a volume ratio of 1:3-5.

8. A corrosion inhibitor for suppressing corrosion in a CO2-enhanced oil recovery system according to claim 7, characterized in that, The organic solvent is one or more of methanol, ethanol, ethylene glycol, and N,N-dimethylformamide.

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