Protective liquid capable of inhibiting oxygen corrosion for nitrogen injection well as well as preparation method and application of protective liquid

Abstract

The invention relates to protection liquid capable of inhibiting oxygen corrosion for a nitrogen injection well and a preparation method and application of the protection liquid, and belongs to the technical field of nitrogen injection oil displacement. The annulus protection liquid provided by the invention is prepared from the following components in percentage by mass: 10 to 15 percent of imidazole-Schiff base corrosion inhibitor, 10 to 15 percent of organic salt, 5 to 10 percent of imidazole corrosion inhibitor, 5 to 10 percent of deoxidant, 3 to 8 percent of pH regulator, 0.5 to 2.0 percent of sterilizing agent, 0.3 to 0.8 percent of scale inhibitor and the balance of water, wherein the imidazole corrosion inhibitor is selected from one or more of 1-methylbenzimidazole, 2-methylbenzimidazole and 2-phenylbenzimidazole. According to the annulus protection liquid, the imidazole-Schiff base corrosion inhibitor and the imidazole corrosion inhibitor are compounded, so that the problem of nitrogen injection well annulus oxygen corrosion can be effectively solved, meanwhile, the effects of scale inhibition, sterilization and free oxygen adsorption are considered, and the annulus protection liquid is good in stability and small in damage to a reservoir stratum.

Description

Technical Field

[0001] This application relates to a protective fluid for nitrogen injection wells that can inhibit oxygen corrosion, its preparation method and application, belonging to the field of nitrogen injection oil displacement technology. Background Technology

[0002] With the continuous improvement and maturation of oil and gas field exploration and development technologies, oil and gas field exploration and development has gradually deepened. In recent years, the focus has been on the development of low-permeability oil fields. These oil fields have abundant geological reserves, a large amount of untapped reserves, and the proportion of oil production is increasing year by year.

[0003] Currently, low-permeability oil and gas field development often employs nitrogen and water mixed injection to improve oil and gas recovery. However, due to insufficient purity of the injected nitrogen, oxygen injection is often unavoidable. The increased oxygen content during injection and production causes severe oxygen corrosion at the wellhead and in the downhole tubing. Furthermore, considering the high salinity of formation water, scaling of the downhole tubing also occurs alongside oxygen corrosion, causing significant damage and reducing the safe service life of the oil and gas well, thus increasing equipment maintenance and replacement costs.

[0004] To address the corrosion problem of oxygen on the tubing and casing string, current technologies often fill the annular space of the tubing and casing with an annular protective fluid. This fluid often contains corrosion inhibitors; some of these inhibitors can form an adsorption film on the tubing and casing walls, thereby reducing oxygen corrosion.

[0005] However, the strength and protective effect of the adsorbed film formed in the corrosion inhibitor system of the currently disclosed annular protective fluid formulations are limited by the defects in the matching of the corrosion inhibitor system, and there is still considerable room for improvement. In addition, the corrosion inhibitor system in the existing technology often only considers the effects of corrosion inhibition and scale inhibition, without taking into account the influence of bacteria and oxygen.

[0006] Therefore, providing an annular protective fluid with better corrosion inhibition effect, while also taking into account scale inhibition, sterilization and adsorption of free oxygen to enhance corrosion inhibition effect, is of great significance for preventing oxygen corrosion in the annulus and downhole tubing of nitrogen injection wells. Summary of the Invention

[0007] To address the aforementioned issues, this application provides a protective fluid for nitrogen injection wells that can inhibit oxygen corrosion, along with its preparation method and application. The annular protective fluid provided in this application, by combining imidazole-Schiff base corrosion inhibitors with imidazole corrosion inhibitors, can more effectively improve the oxygen corrosion problem in the annulus of nitrogen injection wells, while also achieving scale inhibition, sterilization, and free oxygen adsorption effects. Furthermore, it exhibits good stability and minimal damage to the reservoir.

[0008] This application provides a protective fluid for nitrogen injection wells that can inhibit oxygen corrosion. The annular protective fluid comprises the following components by mass percentage: 10-15% imidazole-Schiff base corrosion inhibitor, 10-15% organic salt, 5-10% imidazole corrosion inhibitor, 5-10% oxygen scavenger, 3-8% pH adjuster, 0.5-2.0% sterilizer, 0.3-0.8% scale inhibitor, and the balance being water. The imidazole-Schiff base corrosion inhibitor has the following structure: , The imidazole corrosion inhibitor is selected from one or more of 1-methylbenzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole.

[0009] Optionally, the scale inhibitor is selected from one or more of polyepoxysuccinate and aminotrimethylenephosphonate.

[0010] Optionally, the oxygen scavenger is selected from one or more of dimethyl ketoxime and sulfites.

[0011] Optionally, the pH adjuster is selected from one or more of carbonates and bicarbonates.

[0012] Optionally, the sterilizing agent is selected from one or more of bromonitol, glutaraldehyde, cinnamaldehyde, sodium dichloroisocyanurate, and dichlorocyanomethane.

[0013] Optionally, the organic salt is selected from one or more of formate and acetate.

[0014] Optionally, the preparation method of the imidazole-Schiff base corrosion inhibitor includes: 1) Phenylacetic acid is reacted with diethylenetriamine under an inert gas atmosphere by amidation and cyclization to obtain the first intermediate product; 2) The first intermediate reacts with phenylacetaldehyde in an alcohol solvent to obtain the second intermediate; 3) The second intermediate product is added to an aqueous solution of sodium chloroacetate to react and obtain the imidazole-Schiff base corrosion inhibitor.

[0015] Optionally, step 1) includes controlling the reaction temperature to rise from 150°C to 210°C at a rate of 15~30°C / h; and / or, In step 2), the reaction is carried out under reflux at 80-85°C for 6-8 hours; and / or, In step 3), the reaction temperature is 65~75℃ and the reaction time is 2~4h.

[0016] Optionally, the alcohol solvent in step 2) is one or more of ethanol, isopropanol, n-butanol, isobutanol, and hexanol.

[0017] This application provides a method for preparing the above-mentioned protective fluid for nitrogen injection wells that can inhibit oxygen corrosion, the preparation method comprising the following steps: 1) Add an appropriate amount of water to the preparation container, then add the sterilizing agent and stir until well mixed; 2) Continue adding imidazole-Schiff base corrosion inhibitor and imidazole corrosion inhibitor, and stir until homogeneous; 3) Continue adding oxygen remover and scale inhibitor and stir until well mixed; 4) Add organic salts to adjust the density; 5) Add a pH adjuster to adjust the pH to obtain the protective fluid for nitrogen injection wells that can inhibit oxygen corrosion.

[0018] This application provides the application of the above-mentioned protective fluid for nitrogen injection wells that can inhibit oxygen corrosion, or the protective fluid for nitrogen injection wells prepared by the above-mentioned preparation method, in preventing oxygen corrosion in the annulus of nitrogen injection wells.

[0019] The beneficial effects of this application include at least the following aspects: The imidazole-Schiff base corrosion inhibitor used in this application is an imidazole-Schiff base compound with a benzene ring side group and a quaternary ammonium salt structure. The benzene ring structure provides good oil solubility, allowing the corrosion inhibitor to be added well into the oil displacement environment. The quaternary ammonium salt cation itself has very high surface activity, and after the corrosion inhibitor is added, it easily forms a dense protective film on the metal surface, achieving a good corrosion inhibition and protection effect. The imidazole structure and the C=N Schiff structure outside the imidazole structure have strong electron-donating ability and can further form coordination bonds with the metal to form chemical adsorption, allowing the corrosion inhibitor covering the metal surface to be tightly adsorbed. Its electron-donating ability can improve the stability of the metal surface and increase the difficulty of metal corrosion by increasing the activation energy of metal corrosion, thereby giving the corrosion inhibitor an excellent corrosion inhibition effect.

[0020] Furthermore, experiments revealed that the length of the carbon chain connecting the two benzene rings has a significant impact on its corrosion inhibition effect. The corrosion inhibitor provided in this application has a better working effect with the carbon chain length connecting the two benzene rings, as well as with the quaternary ammonium salt, imidazole structure, and C=N Schiff structure. This ensures that while forming a coordinate bond with the metal to achieve good chemical adsorption, it also ensures the adsorption effect on oily components, allowing the oily components to form a dense protective film on the metal surface, thus achieving a good corrosion inhibition and protection effect.

[0021] If the carbon chain connected to the two benzene rings is too short, the benzene rings and the adsorbed oily components will form obstacles in the spatial structure, which is not conducive to the good adsorption effect of quaternary ammonium salts, imidazole structures and C=N Schiff structures on the metal surface. If the carbon chain connected to the two benzene rings is too long, although the two benzene rings can adsorb more oily substances to form a protective film, the longer distance between the benzene rings and the metal surface results in a slightly weaker protective force between the benzene rings and the adsorbed oily components and the metal surface, leading to a poorer corrosion inhibition effect.

[0022] Meanwhile, the protective fluid provided in this application can also achieve the effects of scale inhibition, sterilization and adsorption of free oxygen, and it has good stability. By compounding imidazole-Schiff base corrosion inhibitors with imidazole corrosion inhibitors, it can achieve better corrosion inhibition effect. Compared with the protective fluids of the prior art, it has comprehensive performance advantages, stronger market competitiveness, and is suitable for use in conjunction with nitrogen injection for the development of low-permeability oil and gas fields. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a diagram illustrating the synthesis reaction process of the imidazole-Schiff base corrosion inhibitor involved in this application. Detailed Implementation

[0024] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are all purchased through commercial channels.

[0025] like Figure 1 The diagram shows the synthesis reaction process of the imidazole-Schiff base corrosion inhibitor involved in this application. The specific synthesis steps are shown in Example 1 below.

[0026] Example 1: Synthesis of Imidazole-Schiff Base Corrosion Inhibitor Imidazole-Schiff base corrosion inhibitor sample 1 S1. Under nitrogen protection, 10g of phenylacetic acid was added to 20ml of xylene solvent. After heating to 85℃, diethylenetriamine was added dropwise. The temperature was slowly increased to remove water. The temperature was controlled at 150℃ and increased to 210℃ over 3 hours. During the dehydration process, acylation and cyclization reactions were gradually achieved. After the reaction was completed, the product was separated and purified to obtain the first intermediate product. S2. Take 10g of the first intermediate product and add it to 500ml of ethanol solvent, then add 7.5g of phenylacetaldehyde to react. The reaction is carried out at 83℃ under reflux for 7h. After the reaction is completed, separate and purify to obtain the second intermediate product. S3. Take 10g of the second intermediate product and add it to 100ml of 40wt% sodium chloroacetate aqueous solution. React at 70℃ for 3h. After the reaction is completed, separate and purify to obtain the corrosion inhibitor product.

[0027] like Figure 1 This is a diagram showing the reaction process of the corrosion inhibitor.

[0028] The carbon spectrum of the prepared corrosion inhibitor was used for structural characterization. The results showed that a characteristic carbon peak of benzene ring was observed at δ=132.0 ppm, and characteristic carbon peaks of C=N were observed at δ=163.1 ppm and δ=168.6 ppm, respectively. Among them, the carbon peak at δ=168.6 ppm is the carbon peak of C=N on the imidazole ring, and a carbon peak of COOR (R is Na) was observed at δ=172.4 ppm. Therefore, based on the carbon spectrum results, it can be inferred that the corrosion inhibitor was successfully synthesized.

[0029] Imidazole-Schiff base corrosion inhibitor sample 2 S1. Under nitrogen protection, 10g of phenylacetic acid was added to 20ml of xylene solvent. After heating to 90℃, diethylenetriamine was added dropwise. The temperature was slowly increased to remove water. The temperature was controlled at 150℃ and increased to 210℃ over 4 hours. During the dehydration process, acylation and cyclization reactions were gradually achieved. After the reaction was completed, the first intermediate product was obtained by separation and purification. S2. Take 10g of the first intermediate product and add it to 500ml of ethanol solvent, then add 7.5g of phenylacetaldehyde to react. The reaction is carried out at 80℃ under reflux for 8h. After the reaction is completed, separate and purify to obtain the second intermediate product. S3. Take 10g of the second intermediate product and add it to 100ml of 40wt% sodium chloroacetate aqueous solution for reaction. The reaction temperature is 65℃ and the reaction time is 4h. After the reaction is completed, separate and purify to obtain the corrosion inhibitor product.

[0030] Imidazole-Schiff base corrosion inhibitor sample 3 S1. Under nitrogen protection, 10g of phenylacetic acid was added to 20ml of xylene solvent. After heating to 80℃, diethylenetriamine was added dropwise. The temperature was slowly increased to remove water. The temperature was controlled at 150℃ and increased to 210℃ over 2 hours. During the dehydration process, acylation and cyclization reactions were gradually achieved. After the reaction was completed, the first intermediate product was obtained by separation and purification. S2. Take 10g of the first intermediate product and add it to 500ml of ethanol solvent, then add 7.5g of phenylacetaldehyde to react. The reaction is carried out at 85℃ under reflux for 6h. After the reaction is completed, separate and purify to obtain the second intermediate product. S3. Take 10g of the second intermediate product and add it to 100ml of 40wt% sodium chloroacetate aqueous solution for reaction. The reaction temperature is 75℃ and the reaction time is 2h. After the reaction is completed, separate and purify to obtain the corrosion inhibitor product.

[0031] Comparison of imidazole-Schiff base corrosion inhibitors: Sample 4 It is basically the same as the imidazole-Schiff base corrosion inhibitor sample 1, except that in step S1, phenylacetic acid is replaced with an equal amount of benzoic acid, and in step S2, phenylacetaldehyde is replaced with an equal amount of benzaldehyde.

[0032] Comparison of imidazole-Schiff base corrosion inhibitors in sample 5 It is basically the same as the imidazole-Schiff base corrosion inhibitor sample 1, except that in step S1, phenylacetic acid is replaced with an equal amount of phenylpropionic acid, and in step S2, phenylacetaldehyde is replaced with an equal amount of phenylpropionic acid.

[0033] Corrosion inhibitor comparison sample 6 The tall oil fatty acid imidazoline quaternary ammonium salt corrosion inhibitor TFAIQAS is disclosed in the existing master's thesis (synthesis and performance evaluation of modified imidazoline corrosion inhibitor, An Shiyu) (refer to Figure 8 in section 2.2.2 for preparation steps).

[0034] Corrosion inhibitor comparison sample 6 The THAIB (preparation steps are described in Figure 10 of section 2.2.3) is a tall oil fatty acid imidazoline Mannich base corrosion inhibitor disclosed in the existing master's thesis (synthesis and performance evaluation of modified imidazoline corrosion inhibitor, An Shiyu).

[0035] Test Example 1 The corrosion inhibition performance of the prepared corrosion inhibitor was tested.

[0036] N80 carbon steel (sample size: 50mm*20mm*5mm) was used as the experimental material. Before use, the sample was polished stepwise with water-resistant sandpaper, then soaked in petroleum ether to remove oil, and then soaked in ethanol to clean the surface. Finally, it was dried at room temperature before testing. The corrosive medium was a 3mol / L hydrochloric acid solution. The experimental procedure was as follows: the N80 carbon steel sample was suspended in the hydrochloric acid solution for 72 hours at a temperature of 45℃. After the experiment, the sample was removed and polished with sandpaper until the surface was shiny to remove corrosion products. Then, it was cleaned sequentially with distilled water, petroleum ether, and ethanol. Finally, it was dried and weighed. The corrosion inhibition efficiency of the N80 carbon steel sample in hydrochloric acid solution was calculated by calculating the weight loss of the sample.

[0037] The formula for calculating corrosion inhibition efficiency is as follows: Corrosion inhibition efficiency % = [(Δm0-Δm1) / Δm0] * 100%.

[0038] Wherein, Δm0 represents the weight loss of the N80 carbon steel specimen without the added corrosion inhibitor, and Δm0 represents the weight loss of the N80 carbon steel specimen after adding the added corrosion inhibitor. The amount of corrosion inhibitor added to the hydrochloric acid solution was 150 mg / L. The corrosion inhibition efficiency test results are shown in Table 1 below.

[0039] Table 1. Test results of corrosion inhibition efficiency of the above corrosion inhibitor products.

[0040] As shown in Table 1, the corrosion inhibitor prepared in this application exhibits excellent corrosion inhibition performance and provides good protection for N80 carbon steel. Even in a strong hydrochloric acid environment, it maintains good protective properties, demonstrating the significant influence of the terminal benzene ring carbon chain length on the protective performance of the oily protective film on the metal surface. Compared to existing corrosion inhibitors, this inhibitor possesses a combination of quaternary ammonium salt, imidazole, and C=N Schiff structures. Furthermore, the two benzene rings have minimal steric hindrance to the adsorption of the quaternary ammonium salt, imidazole, and C=N Schiff structures onto the metal surface. Therefore, this corrosion inhibitor can achieve better adsorption on the metal surface, adsorbing oily components to form a dense protective film, resulting in superior corrosion inhibition.

[0041] Example 2: Preparation and Effect Testing of Protective Solution The protective fluid provided in this application consists of the following components by mass percentage: 10-15% imidazole-Schiff base corrosion inhibitor, 10-15% organic salt, 5-10% imidazole corrosion inhibitor, 5-10% oxygen scavenger, 3-8% pH adjuster, 0.5-2.0% sterilizer, 0.3-0.8% scale inhibitor, and the balance being water. The preparation method is as follows: 1) First, add an appropriate amount of water to a container, then add the sterilizer and stir until homogeneous; 2) Continue to add the imidazole-Schiff base corrosion inhibitor and the imidazole corrosion inhibitor and stir until homogeneous; 3) Continue to add the oxygen scavenger and scale inhibitor and stir until homogeneous; 4) Add the organic salt to adjust the density; 5) Add the pH adjuster to adjust the pH, thus obtaining a protective fluid for nitrogen injection wells that can inhibit oxygen corrosion.

[0042] The performance of the obtained protective liquid was tested using P110 steel. The results are shown in Table 3 below, and the composition of each protective liquid is shown in Table 2.

[0043] Table 2. Composition of each protective fluid and its effect on preventing oxygen corrosion.

[0044] Table 2 (Continued)

[0045] Table 3 Corrosion protection results of P110 steel with various protective solutions

[0046] According to the results in Tables 2 and 3, the protective solution provided in this application, by using an imidazole-Schiff base corrosion inhibitor in combination with imidazole-based corrosion inhibitors such as 1-methylbenzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole, exhibits a significant synergistic effect compared to using imidazole-based corrosion inhibitors or imidazole-Schiff base corrosion inhibitors alone. The imidazole-Schiff base corrosion inhibitor provided in this application has a better adsorption effect on the metal surface compared to imidazole-based corrosion inhibitors such as 1-methylbenzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole. However, due to the presence of long linear carbon chains, some pores may exist, resulting in the benzene ring density on the metal surface not being at its highest. By adding imidazole-based corrosion inhibitors such as 1-methylbenzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole, which contain benzene rings and have relatively short linear carbon chains, and combining them with the imidazole-Schiff base corrosion inhibitor, the benzene ring density on the metal surface can be further improved, thereby facilitating the adsorption of oil layers and their tight adhesion to the metal surface, thus further enhancing the oxygen corrosion protection effect.

[0047] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A protective fluid for nitrogen injection wells that inhibits oxygen corrosion, characterized in that, The annular protective fluid comprises the following components by mass percentage: 10-15% imidazole-Schiff base corrosion inhibitor, 10-15% organic salt, 5-10% imidazole corrosion inhibitor, 5-10% oxygen scavenger, 3-8% pH adjuster, 0.5-2.0% sterilizer, 0.3-0.8% scale inhibitor, and the balance being water; The imidazole-Schiff base corrosion inhibitor has the following structure: ， The imidazole corrosion inhibitor is selected from one or more of 1-methylbenzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole.

2. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The scale inhibitor is selected from one or more of polyepoxysuccinate and aminotrimethylene phosphonate.

3. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The oxygen scavenger is selected from one or more of dimethyl ketoxime and sulfites.

4. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The pH adjuster is selected from one or more of carbonates and bicarbonates.

5. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The sterilizing agent is selected from one or more of bromonitol, glutaraldehyde, cinnamaldehyde, sodium dichloroisocyanurate, and dichlorocyanomethane.

6. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The organic salt is selected from one or more of formate and acetate.

7. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 1, characterized in that, The preparation method of the imidazole-Schiff base corrosion inhibitor includes: 1) Phenylacetic acid is reacted with diethylenetriamine under an inert gas atmosphere by amidation and cyclization to obtain the first intermediate product; 2) The first intermediate reacts with phenylacetaldehyde in an alcohol solvent to obtain the second intermediate; 3) The second intermediate product is added to an aqueous solution of sodium chloroacetate to react and obtain the imidazole-Schiff base corrosion inhibitor.

8. The protective fluid for nitrogen injection wells that inhibits oxygen corrosion according to claim 7, characterized in that, Step 1) includes controlling the reaction temperature to rise from 150°C to 210°C at a rate of 15~30°C / h; and / or, In step 2), the reaction is carried out under reflux at 80-85°C for 6-8 hours; and / or, In step 3), the reaction temperature is 65~75℃ and the reaction time is 2~4h.

9. The method for preparing a protective fluid for nitrogen injection wells that can inhibit oxygen corrosion as described in any one of claims 1 to 8, characterized in that, The preparation method includes the following steps: 1) Add an appropriate amount of water to the preparation container, then add the sterilizing agent and stir until well mixed; 2) Continue adding imidazole-Schiff base corrosion inhibitor and imidazole corrosion inhibitor, and stir until homogeneous; 3) Continue adding oxygen remover and scale inhibitor and stir until well mixed; 4) Add organic salts to adjust the density; 5) Add a pH adjuster to adjust the pH to obtain the protective fluid for nitrogen injection wells that can inhibit oxygen corrosion.

10. The protective fluid for nitrogen injection wells that can inhibit oxygen corrosion as described in any one of claims 1 to 8, or the protective fluid for nitrogen injection wells that can inhibit oxygen corrosion prepared by the preparation method described in claim 9, is used in the prevention of oxygen corrosion in the annulus of nitrogen injection wells.

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