Corrosion inhibitor for oilfield annulus protection fluid and preparation method thereof

Abstract

The application relates to the technical field of petroleum drilling and production chemical additives, in particular to an oilfield annular space protection liquid corrosion inhibitor and a preparation method thereof, which comprises the following raw materials in parts by weight: 15-25 parts of additive A, 15-20 parts of additive B, 8-12 parts of sodium molybdate, 8-10 parts of sodium gluconate, 4-6 parts of zinc salt and 30-50 parts of water. In the application, the additive A is prepared by modifying epoxy propyl trimethyl ammonium chloride with sesbania gum polysaccharide and reacting with a composite material, the sesbania gum polysaccharide has a natural polyhydroxyl macromolecular structure, can quickly adsorb on the steel surface of the oil pipe and the casing to form a flexible pre-adsorption film, can fill the micro corrosion gaps on the metal surface, can prolong the long-acting period of the corrosion inhibitor, the additive B takes petroleum coke-based activated carbon as a carrier, is modified by quinoline quaternization, forms a corrosion inhibition synergistic system, can inhibit the film peeling problem caused by the annular space fluid flow, and can synergistically reduce the uniform corrosion and local pitting corrosion rate of the pipe.

Description

Technical Field

[0001] This invention relates to the field of petroleum drilling and production chemical additives technology, specifically to a corrosion inhibitor for oilfield annular protection fluid and its preparation method. Background Technology

[0002] Corrosion inhibitors for oilfield annulus protection fluids are core chemical agents specifically designed to protect oil casing from corrosion in the confined annulus environment. They are typically formulated from imidazoline, organic amine, and other compounds, inhibiting electrochemical corrosion by forming a dense protective film on the metal surface. For complex operating conditions such as high temperature, high salinity, and CO2 / H2S content, modern corrosion inhibitors also need to have multiple synergistic effects such as oxygen removal, sterilization, and scale inhibition to address the increased corrosion risk after gas intrusion.

[0003] In existing technologies, small-molecule corrosion inhibitors exhibit poor dispersion stability, are prone to stratification and sedimentation after long-term standing, and their active corrosion-inhibiting molecules are rapidly consumed, resulting in a significant decrease in corrosion inhibition efficiency within a short period. Therefore, this invention provides a corrosion inhibitor for oilfield annular protective fluids and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion inhibitor for oilfield annular protective fluid and its preparation method. The corrosion inhibitor prepared by this invention not only has good high-temperature and high-salt corrosion inhibition performance, but also has the advantages of long-term slow release and strong resistance to media erosion, effectively improving the corrosion protection effect of oil and gas well casing materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In the first aspect, a corrosion inhibitor for annular protection fluid in oilfields comprises the following raw materials in parts by weight: 15-25 parts of additive A, 15-20 parts of additive B, 8-12 parts of sodium molybdate, 8-10 parts of sodium gluconate, 4-6 parts of zinc salt and 30-50 parts of water.

[0007] The raw materials for additive A include a first mixture, a modified glycidyltrimethylammonium chloride aqueous solution, and a composite material.

[0008] The raw materials for additive B include base powder, quinoline, and benzyl chloride.

[0009] Further, additive A is prepared by the following method: a first mixture is mixed with a modified glycidyltrimethylammonium chloride aqueous solution at a mass ratio of 1:(1.8-2.2), and stirred at a constant temperature of 45-55°C until the reaction is complete to obtain a first intermediate. 8.5-9.5% of the mass of the first intermediate composite material is added to the first intermediate, the temperature is raised to 75-82°C, and stirred for 1.6-1.9 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and filtered under negative pressure to obtain a filter cake. The filter cake is washed twice with anhydrous ethanol and once with isopropanol, and finally vacuum dried at 60°C to constant weight to obtain additive A. The composite material is prepared by compounding tetramethyldipropylenetriamine and 4-amino-5-methyl-1,2,4-triazol-3-thiol at a mass ratio of 92:8.

[0010] Further, the first mixture is prepared by the following method: guar gum polysaccharide powder and citric acid aqueous solution are mixed at a mass ratio of 1:(12-14), and stirred continuously at 28-32℃ and 200-250rpm for 40-60min to obtain the first mixture, wherein the volume fraction of the citric acid aqueous solution is 3.5-4.5%.

[0011] Further, the modified glycidyltrimethylammonium chloride aqueous solution is prepared by the following method: glycidyltrimethylammonium chloride, deionized water, and dipropylene glycol methyl ether are mixed at a mass ratio of 1:5.2:0.35, stirred at 180-220 rpm for 20-30 min at room temperature to obtain a mixture, 0.05-0.08% by mass of 1,3-benzothiazole-6-sulfonyl chloride is added to the mixture, stirred in the dark for 25-35 min, allowed to stand for 40-60 min, filtered, and the filtrate is collected to obtain the modified glycidyltrimethylammonium chloride aqueous solution.

[0012] Further, the additive B is prepared by the following method: a base powder is mixed with quinoline at a mass ratio of 1:(1.2-1.8), heated to 80-100℃ under nitrogen protection, and stirred at 200-300 rpm for 1 hour to obtain a premix. 4-6% of benzyl chloride is added to the premix, the temperature is raised to 110-130℃, and refluxed for 4-6 hours to obtain a second intermediate. The second intermediate is cooled to 70-80℃, and 8-12% of the second intermediate by mass is added to a second mixture. The mixture is kept warm and stirred for 1 hour, and then distilled under reduced pressure for 2-3 hours at an absolute pressure of 0.06-0.08 MPa. After cooling, additive B is obtained. The base powder is petroleum coke-based activated carbon powder, and the second mixture is prepared by isopropanol and ethylene glycol at a mass ratio of 2:1.

[0013] Further, the base powder is prepared by the following method: high-sulfur petroleum coke with a sulfur content of not less than 2% is pulverized and passed through a 200-mesh sieve to obtain petroleum coke fine powder. The petroleum coke fine powder is added to a composite aqueous solution and impregnated at room temperature for 18-24 hours. The residue is then filtered to obtain filter residue. The filter residue is dried and dehydrated at 85℃-95℃ to constant weight, and then placed in a low-temperature plasma device. Under an atmosphere with a chamber pressure of 15-35 Pa and an argon flow rate of 30-50 sccm, the surface is cleaned and activated using the low-temperature plasma device. The pretreated filter residue is transferred into a tube furnace and heated to 800-900℃ at a rate of 5℃ / min under a nitrogen atmosphere. It is then held at this temperature for 1.5-2 hours for activation. After natural cooling, the activated crude product is obtained. The activated crude product is preliminarily washed with deionized water to remove surface dust. It is then directly placed in a 10% hydrochloric acid solution and boiled for 1 hour. After filtration, the filter residue is washed with deionized water until neutral and then dried at 105℃ to obtain the basic powder. The mass ratio of the petroleum coke to the composite aqueous solution is 1:(3-5).

[0014] Further, the composite aqueous solution is prepared by the following method: potassium dihydrogen phosphate, sodium metaborate, and dodecantungstic phosphate are mixed at a mass ratio of 100:(3-5):(1.5-2.5) to obtain a mixed product. 3.5-5.7 times the mass of deionized water is added to the mixed product, and the mixture is stirred at 300-400 rpm for 30-40 min and allowed to stand for 2 h to mature, thereby obtaining the composite aqueous solution.

[0015] Furthermore, the zinc salt is one of zinc sulfate, zinc chloride, or zinc nitrate.

[0016] Furthermore, the sodium molybdate, sodium gluconate, and zinc salt are all of industrial grade purity, with a mass concentration of not less than 98%.

[0017] Secondly, the present invention provides a method for preparing a corrosion inhibitor for annular protective fluid in oilfields, comprising the following steps:

[0018] Step 1: Add water to the reaction vessel and heat it to 40-50℃. While stirring at 300-400 rpm, add sodium gluconate, sodium molybdate and zinc salt in sequence and stir until completely dissolved to obtain a premix.

[0019] Step 2: Add additives A and B to the premix, continue stirring for 40-60 minutes, cool to room temperature, and obtain the corrosion inhibitor for oilfield annular protection fluid.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In this invention, additive A is prepared by modifying guar gum polysaccharide with glycidyltrimethylammonium chloride and reacting it with the composite material. Guar gum polysaccharide has a natural multi-hydroxyl macromolecular structure, which can be rapidly adsorbed on the steel surface of tubing and casing to form a flexible pre-adsorption film, filling the micro-corrosion gaps on the metal surface. Modified glycidyltrimethylammonium chloride introduces quaternary ammonium salt cationic groups, which can be directionally adsorbed on the active sites of the metal anode to inhibit anodic dissolution. Benzothiazole sulfonyl chloride modification further enhances the molecular temperature resistance and salt resistance. After the two are compounded, they form a composite protective film with sodium molybdate, sodium gluconate, and zinc salt inorganic corrosion inhibitors. At the same time, the long polysaccharide chain can improve the dispersion stability of the corrosion inhibitor system in the high-salinity formation water of the annulus, avoid the aggregation and sedimentation of the corrosion inhibitor components, and effectively inhibit the electrochemical corrosion of wellbore and tubing by CO2 and H2S acidic media, prolonging the long-term action period of the corrosion inhibitor, and is suitable for the high-temperature and high-salt annulus working conditions of oilfields.

[0022] 2. In this invention, additive B uses petroleum coke-based activated carbon as a carrier and is modified by quinoline quaternization to form a corrosion inhibition synergistic system. The modified activated carbon surface forms oxygen- and sulfur-containing active adsorption sites, which improves the loading capacity and binding strength of quinoline and benzyl chloride quaternized corrosion-inhibiting organic molecules. The porous structure of the activated carbon enables the slow release of quinoline quaternary ammonium corrosion inhibitor components, continuously replenishing corrosion-inhibiting active substances at the metal interface. The conductive framework of the activated carbon itself can block the diffusion of corrosive medium ions to the metal matrix, effectively improving the corrosion inhibitor's resistance to erosion and aging, inhibiting the film peeling problem caused by annular fluid flow, and synergistically reducing the rate of uniform corrosion and local pitting corrosion of the pipe.

[0023] 3. In this invention, after additive A and additive B are combined, the pre-adsorption effect of polysaccharide macromolecules in additive A and the physical embedding effect of activated carbon pores in additive B prolong the residence time of the corrosion inhibitor on the metal surface, thereby reducing the rate of damage to the protective film by fluid scouring and maintaining a complete and dense protective film for a long time in the high temperature, high salinity and flowing annular medium of oilfield. Attached Figure Description

[0024] Figure 1 The present invention provides a flowchart of a corrosion inhibitor for oilfield annular protective fluid and its preparation method. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0027] Example 1:

[0028] Preparation of the first mixture: Guillain polysaccharide powder and citric acid aqueous solution were mixed at a mass ratio of 1:12 and stirred continuously at 28°C and 200 rpm for 40 min to obtain the first mixture, wherein the volume fraction of the citric acid aqueous solution was 3.5%.

[0029] Preparation of modified glycidyltrimethylammonium chloride aqueous solution: Glycidyltrimethylammonium chloride, deionized water, and dipropylene glycol methyl ether were mixed at a mass ratio of 1:5.2:0.35 and stirred at 180 rpm for 20 min at room temperature to obtain a mixture. 0.05% by mass of 1,3-benzothiazole-6-sulfonyl chloride was added to the mixture, and the mixture was stirred in the dark for 25 min. After standing for 40 min, the mixture was filtered, and the filtrate was collected to obtain the modified glycidyltrimethylammonium chloride aqueous solution.

[0030] Preparation of Additive A: The first mixture was mixed with a modified glycidyltrimethylammonium chloride aqueous solution at a mass ratio of 1:1.8, and stirred at 45°C until the reaction was complete to obtain the first intermediate. 8.5% (by mass) of the composite material was added to the first intermediate, and the temperature was raised to 75°C and stirred for 1.6 hours. In this step, the primary amine group of 4-amino-5-methyl-1,2,4-triazol-3-thiol in the composite material reacts with the incompletely closed ring in the first intermediate. The oxygen group undergoes a nucleophilic ring-opening reaction, thereby stably grafting the triazole thiol structure onto the polysaccharide backbone. After the reaction is completed, the mixture is naturally cooled to room temperature and filtered under negative pressure to obtain a filter cake. The filter cake is washed twice with anhydrous ethanol and once with isopropanol, and finally dried under vacuum at 60°C to constant weight to obtain additive A. The composite material is prepared by compounding tetramethyldipropylenetriamine and 4-amino-5-methyl-1,2,4-triazole-3-thiol in a mass ratio of 92:8.

[0031] Preparation of composite aqueous solution: Potassium dihydrogen phosphate, sodium metaborate, and dodecantungstic phosphate were mixed in a mass ratio of 100:3:1.5 to obtain a mixed product. Deionized water with a mass of 3.5 times its weight was added to the mixed product, and the mixture was stirred at 300 rpm for 30 min and allowed to stand for 2 h to mature, thus obtaining a composite aqueous solution.

[0032] Preparation of basic powder: High-sulfur petroleum coke with a sulfur content of not less than 2% is pulverized and passed through a 200-mesh sieve to obtain petroleum coke fine powder. The petroleum coke fine powder is added to a composite aqueous solution and impregnated at room temperature for 18 hours. After filtration, filter residue is obtained. The filter residue is dried and dehydrated at 85℃ to constant weight and then placed in a low-temperature plasma device. Under an atmosphere with a chamber pressure of 15Pa and an argon flow rate of 30sccm, it is pretreated at 350W power for 20 minutes. For the extremely harsh conditions of ultra-high temperature and high H2S in deep wells, the pretreated filter residue is transferred to a tube furnace and heated under a nitrogen atmosphere at 5℃ / The temperature is increased to 800℃ at a rate of min, and activated by holding for 1.5h. In conventional oilfield applications, this step can also be replaced by conventional industrial rotary kilns and chemical activation methods to meet the cost control requirements of large-scale production of bulk consumables. After natural cooling, activated crude product is obtained. The activated crude product is preliminarily washed with deionized water to remove surface dust, and then directly placed in a 10% hydrochloric acid solution for boiling and acid washing for 1h. After filtration, the filter residue is washed with deionized water until neutral, and then dried at 105℃ to obtain basic powder. The mass ratio of petroleum coke to composite aqueous solution is 1:3.

[0033] Preparation of Additive B: The base powder and quinoline were mixed at a mass ratio of 1:1.2, heated to 80°C under nitrogen protection, and stirred at 200 rpm for 1 hour to obtain a premix. 4% (by mass) of benzyl chloride was added to the premix, and the mixture was heated to 110°C and refluxed for 4 hours to obtain a second intermediate. The second intermediate was cooled to 70°C, and 8% (by mass) of a second mixture was added. The mixture was kept warm and stirred for 1 hour, and then distilled under reduced pressure at 0.06 MPa for 2 hours. After cooling, Additive B was obtained. The base powder was petroleum coke-based activated carbon powder, and the second mixture was prepared by mixing isopropanol and ethylene glycol at a mass ratio of 2:1.

[0034] The zinc salt is one of zinc sulfate, zinc chloride, or zinc nitrate.

[0035] The sodium molybdate, sodium gluconate, and zinc salt are all of industrial grade purity, with a mass concentration of not less than 98%.

[0036] Preparation of raw materials: 15 parts additive A, 15 parts additive B, 8 parts sodium molybdate, 8 parts sodium gluconate, 4 parts zinc salt and 30 parts water.

[0037] Preparation of corrosion inhibitors for oilfield annular protective fluids:

[0038] Step 1: Add water to the reaction vessel and heat to 40°C. While stirring at 300 rpm, add sodium gluconate, sodium molybdate, and zinc salt in sequence and stir until completely dissolved to obtain a premix.

[0039] Step 2: Add additives A and B to the premix, continue stirring for 40 minutes, cool to room temperature, and obtain the corrosion inhibitor for oilfield annular protection fluid.

[0040] Example 2:

[0041] Preparation of the first mixture: Guillain polysaccharide powder and citric acid aqueous solution were mixed at a mass ratio of 1:13 and stirred continuously at 30℃ and 230rpm for 50min to obtain the first mixture, wherein the volume fraction of the citric acid aqueous solution was 4%.

[0042] Preparation of modified glycidyltrimethylammonium chloride aqueous solution: Glycidyltrimethylammonium chloride, deionized water, and dipropylene glycol methyl ether were mixed at a mass ratio of 1:5.2:0.35 and stirred at 200 rpm for 25 min at room temperature to obtain a mixture. 0.06% by mass of 1,3-benzothiazole-6-sulfonyl chloride was added to the mixture, and the mixture was stirred in the dark for 30 min. After standing for 50 min, the mixture was filtered, and the filtrate was collected to obtain the modified glycidyltrimethylammonium chloride aqueous solution.

[0043] Preparation of Additive A: The first mixture was mixed with a modified glycidyltrimethylammonium chloride aqueous solution at a mass ratio of 1:2 and stirred at 50°C until the reaction was complete to obtain the first intermediate. 9% (by mass) of the composite material was added to the first intermediate, and the temperature was raised to 79°C and stirred for 1.7 h. In this step, the primary amine group of 4-amino-5-methyl-1,2,4-triazole-3-thiol in the composite material underwent a nucleophilic ring-opening reaction with the incompletely closed epoxy group in the first intermediate, thereby stably grafting the triazole thiol structure onto the polysaccharide backbone. After the reaction, the mixture was naturally cooled to room temperature and filtered under negative pressure to obtain a filter cake. The filter cake was washed twice with anhydrous ethanol and once with isopropanol, and finally vacuum dried at 60°C to constant weight to obtain Additive A. The composite material was prepared by compounding tetramethyldipropylenetriamine and 4-amino-5-methyl-1,2,4-triazole-3-thiol at a mass ratio of 92:8.

[0044] Preparation of composite aqueous solution: Potassium dihydrogen phosphate, sodium metaborate, and dodecantungstic phosphate were mixed in a mass ratio of 100:4:2 to obtain a mixed product. Five times the mass of deionized water was added to the mixed product, and the mixture was stirred at 400 rpm for 35 min and allowed to stand for 2 h to mature, thus obtaining a composite aqueous solution.

[0045] Preparation of basic powder: High-sulfur petroleum coke with a sulfur content of not less than 2% is pulverized and passed through a 200-mesh sieve to obtain petroleum coke fine powder. The petroleum coke fine powder is added to a composite aqueous solution and impregnated at room temperature for 22 hours. After filtration, filter residue is obtained. The filter residue is dried and dehydrated at 90℃ to constant weight and then placed in a low-temperature plasma device. Under an atmosphere with a chamber pressure of 25Pa and an argon flow rate of 40sccm, it is pretreated at 400W power for 22 minutes. For the extremely harsh conditions of ultra-high temperature and high H2S in deep wells, the pretreated filter residue is transferred to a tube furnace and heated under a nitrogen atmosphere at 5℃ / The temperature is increased to 850℃ at a rate of min, and activated by holding for 1.8h. In conventional oilfield applications, this step can also be replaced by conventional industrial rotary kilns and chemical activation methods to meet the cost control requirements of large-scale production of bulk consumables. After natural cooling, activated crude product is obtained. The activated crude product is preliminarily washed with deionized water to remove surface dust, and then directly placed in a 10% hydrochloric acid solution for boiling and acid washing for 1h. After filtration, the filter residue is washed with deionized water until neutral, and then dried at 105℃ to obtain basic powder. The mass ratio of petroleum coke to composite aqueous solution is 1:4.

[0046] Preparation of Additive B: The base powder and quinoline were mixed at a mass ratio of 1:1.6, heated to 90°C under nitrogen protection, and stirred at 250 rpm for 1 hour to obtain a premix. 5% (by mass) of benzyl chloride was added to the premix, and the mixture was heated to 120°C and refluxed for 5 hours to obtain a second intermediate. The second intermediate was cooled to 75°C, and 10% (by mass) of a second mixture was added. The mixture was kept warm and stirred for 1 hour, and then distilled under reduced pressure at 0.07 MPa for 2.5 hours. After cooling, Additive B was obtained. The base powder was petroleum coke-based activated carbon powder, and the second mixture was prepared by mixing isopropanol and ethylene glycol at a mass ratio of 2:1.

[0047] The zinc salt is one of zinc sulfate, zinc chloride, or zinc nitrate.

[0048] The sodium molybdate, sodium gluconate, and zinc salt are all of industrial grade purity, with a mass concentration of not less than 98%.

[0049] Preparation of raw materials: 20 parts additive A, 18 parts additive B, 10 parts sodium molybdate, 9 parts sodium gluconate, 5 parts zinc salt and 40 parts water.

[0050] Preparation of corrosion inhibitors for oilfield annular protective fluids:

[0051] Step 1: Add water to the reaction vessel and heat to 45°C. While stirring at 400 rpm, add sodium gluconate, sodium molybdate, and zinc salt in sequence and stir until completely dissolved to obtain a premix.

[0052] Step 2: Add additives A and B to the premix, continue stirring for 50 minutes, cool to room temperature, and obtain the corrosion inhibitor for oilfield annular protection fluid.

[0053] Example 3:

[0054] Preparation of the first mixture: Guillain polysaccharide powder and citric acid aqueous solution were mixed at a mass ratio of 1:14 and stirred continuously at 32℃ and 250rpm for 60min to obtain the first mixture, wherein the volume fraction of the citric acid aqueous solution was 4.5%.

[0055] Preparation of modified glycidyltrimethylammonium chloride aqueous solution: Glycidyltrimethylammonium chloride, deionized water, and dipropylene glycol methyl ether were mixed at a mass ratio of 1:5.2:0.35 and stirred at 220 rpm for 30 min at room temperature to obtain a mixture. 0.08% by mass of 1,3-benzothiazole-6-sulfonyl chloride was added to the mixture, and the mixture was stirred in the dark for 35 min. After standing for 60 min, the mixture was filtered, and the filtrate was collected to obtain the modified glycidyltrimethylammonium chloride aqueous solution.

[0056] Preparation of Additive A: The first mixture was mixed with a modified glycidyltrimethylammonium chloride aqueous solution at a mass ratio of 1:2.2, and stirred at 55°C until the reaction was complete to obtain the first intermediate. 9.5% (by mass) of the composite material was added to the first intermediate, and the temperature was raised to 82°C and stirred for 1.9 h. In this step, the primary amine group of 4-amino-5-methyl-1,2,4-triazol-3-thiol in the composite material reacts with the incompletely closed ring in the first intermediate. The oxygen group undergoes a nucleophilic ring-opening reaction, thereby stably grafting the triazole thiol structure onto the polysaccharide backbone. After the reaction is completed, the mixture is naturally cooled to room temperature and filtered under negative pressure to obtain a filter cake. The filter cake is washed twice with anhydrous ethanol and once with isopropanol, and finally dried under vacuum at 60°C to constant weight to obtain additive A. The composite material is prepared by compounding tetramethyldipropylenetriamine and 4-amino-5-methyl-1,2,4-triazole-3-thiol in a mass ratio of 92:8.

[0057] Preparation of composite aqueous solution: Potassium dihydrogen phosphate, sodium metaborate, and dodecantungstic phosphate were mixed in a mass ratio of 100:5:2.5 to obtain a mixed product. Deionized water with a mass of 5.7 times its weight was added to the mixed product, and the mixture was stirred at 400 rpm for 40 min and allowed to stand for 2 h to mature, thus obtaining a composite aqueous solution.

[0058] Preparation of basic powder: High-sulfur petroleum coke with a sulfur content of not less than 2% is pulverized and passed through a 200-mesh sieve to obtain petroleum coke fine powder. The petroleum coke fine powder is added to a composite aqueous solution and impregnated at room temperature for 24 hours. After filtration, filter residue is obtained. The filter residue is dried and dehydrated at 95℃ to constant weight and then placed in a low-temperature plasma device. Under an atmosphere with a chamber pressure of 35Pa and an argon flow rate of 50sccm, it is pretreated at 450W power for 25 minutes. For the extremely harsh conditions of ultra-high temperature and high H2S in deep wells, the pretreated filter residue is transferred to a tube furnace and heated under a nitrogen atmosphere at 5℃ / The temperature is increased to 900℃ at a rate of min, and activated by holding for 2 hours. In conventional oilfield applications, this step can also be replaced by conventional industrial rotary kilns and chemical activation methods to meet the cost control requirements of large-scale production of bulk consumables. After natural cooling, activated crude product is obtained. The activated crude product is preliminarily washed with deionized water to remove surface dust, and then directly placed in a 10% hydrochloric acid solution for boiling and acid washing for 1 hour. After filtration, the filter residue is washed with deionized water until neutral, and then dried at 105℃ to obtain basic powder. The mass ratio of petroleum coke to composite aqueous solution is 1:5.

[0059] Preparation of Additive B: The base powder and quinoline were mixed at a mass ratio of 1:1.8, heated to 100°C under nitrogen protection, and stirred at 300 rpm for 1 hour to obtain a premix. 6% (by mass) of benzyl chloride was added to the premix, and the mixture was heated to 130°C and refluxed for 6 hours to obtain a second intermediate. The second intermediate was cooled to 80°C, and a second mixture of 12% (by mass) of the second intermediate was added. The mixture was kept warm and stirred for 1 hour, and then distilled under reduced pressure at 0.08 MPa for 3 hours. After cooling, Additive B was obtained. The base powder was petroleum coke-based activated carbon powder, and the second mixture was prepared by mixing isopropanol and ethylene glycol at a mass ratio of 2:1.

[0060] The zinc salt is one of zinc sulfate, zinc chloride, or zinc nitrate.

[0061] The sodium molybdate, sodium gluconate, and zinc salt are all of industrial grade purity, with a mass concentration of not less than 98%.

[0062] Preparation of raw materials: 25 parts additive A, 20 parts additive B, 12 parts sodium molybdate, 10 parts sodium gluconate, 6 parts zinc salt and 50 parts water.

[0063] Preparation of corrosion inhibitors for oilfield annular protective fluids:

[0064] Step 1: Add water to the reaction vessel and heat to 50°C. While stirring at 400 rpm, add sodium gluconate, sodium molybdate, and zinc salt in sequence and stir until completely dissolved to obtain a premix.

[0065] Step 2: Add additives A and B to the premix, continue stirring for 60 minutes, cool to room temperature, and obtain the corrosion inhibitor for oilfield annular protection fluid.

[0066] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not contain additive A.

[0067] Comparative Example 2 differs from Example 1 in that it does not contain additive B.

[0068] Comparative Example 3 differs from Example 1 in that: no composite material is added during the preparation of additive A, and no quinoline and benzyl chloride are added during the preparation of additive B.

[0069] Performance testing: The corrosion inhibitors used in the oilfield annulus protection fluids treated in Examples 1-3 and Comparative Examples 1-3 were tested, and the test data are recorded in the table below:

[0070] Table 1

[0071] Testing items Static corrosion rate (mm / a) Pitting depth (μm) Corrosion inhibitor stability (settling rate, %) Example 1 0.021 2.3 0.8 Example 2 0.019 2.1 0.6 Example 3 0.020 2.2 0.5 Comparative Example 1 0.087 12.6 8.2 Comparative Example 2 0.079 10.8 3.5 Comparative Example 3 0.063 8.4 5.1

[0072] In the performance test, the static corrosion rate was determined according to GB / T 18175-2014, the pitting depth was determined according to GB / T 18590-2025, and the stability of the corrosion inhibitor was evaluated by measuring the mass ratio of bottom sediment after the sample was kept at a constant temperature of 60℃ for 72 hours.

[0073] The data obtained from the performance test table show that the static corrosion rate of the corrosion inhibitors for oilfield annular protective fluid prepared in Examples 1-3 is significantly lower than that in Comparative Examples 1-3, and the pitting depth is significantly reduced. At the same time, the stability of the corrosion inhibitors is better than that in Comparative Examples 1-3. This indicates that the guar gum polysaccharide in Additive A forms a flexible pre-adsorption film on the metal surface through its natural multi-hydroxyl macromolecular structure. It works synergistically with the quaternary ammonium salt cationic groups introduced by modification to be directionally adsorbed on the active sites of the metal anode, effectively inhibiting the anode dissolution process. Meanwhile, the introduction of benzothiazole sulfonyl chloride further enhances the temperature and salt resistance of the molecules. In Additive B, the petroleum coke-based activated carbon, after being modified by quinoline quaternization, has a porous structure that enables the slow release and continuous replenishment of corrosion-inhibiting active molecules. Its conductive framework blocks the diffusion path of corrosive medium ions to the metal matrix.

[0074] When additives A and B are combined, they form a dual-layer synergistic protection system consisting of an adsorption film and a slow-release barrier layer. Simultaneously, the polysaccharide polymer of additive A improves the dispersibility of activated carbon powder in the annular protective solution, while the active sites of additive B fix the corrosion-inhibiting small molecules in additive A. The two work synergistically to inhibit the dual electrochemical reactions at the anodic and cathodic points. Comparative Example 1, lacking additive A, cannot form a pre-adsorption film and a cation-oriented adsorption layer, allowing the corrosive medium to directly attack the metal surface, resulting in a significantly increased corrosion rate. Comparative Example 2, lacking additive B, lacks a slow-release barrier layer and a long-term corrosion-inhibiting molecule replenishment mechanism, leading to rapid film loss under scouring conditions and a significantly increased pitting depth. Comparative Example 3, lacking the introduction of composite materials in additive A and the quaternization modification of additive B, lacks the strong chemisorption groups of triazole thiol and the corrosion-inhibiting core of quinoline quaternary ammonium salt, thus failing to exert its synergistic effect, and its performance is inferior to the examples.

[0075] By comparing and analyzing the relevant data in the table, it can be seen that the corrosion inhibitor for oilfield annular protective fluid prepared by this invention not only has a low static corrosion rate and pitting depth, but also good storage stability. This indicates that the corrosion inhibitor for oilfield annular protective fluid and its preparation method provided by this invention have a broader market prospect and are more suitable for widespread application.

[0076] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A corrosion inhibitor for oilfield annular protective fluid, characterized in that, It includes the following raw materials by weight: 15-25 parts additive A, 15-20 parts additive B, 8-12 parts sodium molybdate, 8-10 parts sodium gluconate, 4-6 parts zinc salt and 30-50 parts water; The raw materials for additive A include a first mixture, a modified glycidyltrimethylammonium chloride aqueous solution, and a composite material. The raw materials for additive B include base powder, quinoline, and benzyl chloride.

2. The corrosion inhibitor for oilfield annular protective fluid according to claim 1, characterized in that, Additive A is prepared by the following method: a first mixture is mixed with a modified glycidyltrimethylammonium chloride aqueous solution at a mass ratio of 1:(1.8-2.2), and stirred at a constant temperature of 45-55℃ until the reaction is complete to obtain a first intermediate. 8.5-9.5% of the mass of the first intermediate composite material is added to the first intermediate, the temperature is raised to 75-82℃, and stirred for 1.6-1.9 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and filtered under negative pressure to obtain a filter cake. The filter cake is washed twice with anhydrous ethanol and once with isopropanol, and finally vacuum dried at 60℃ to constant weight to obtain additive A. The composite material is prepared by compounding tetramethyldipropylenetriamine and 4-amino-5-methyl-1,2,4-triazol-3-thiol at a mass ratio of 92:

8.

3. The corrosion inhibitor for oilfield annular protective fluid according to claim 2, characterized in that, The first mixture is prepared by the following method: guar gum polysaccharide powder and citric acid aqueous solution are mixed at a mass ratio of 1:(12-14), and stirred continuously at 28-32℃ and 200-250rpm for 40-60min to obtain the first mixture, wherein the volume fraction of the citric acid aqueous solution is 3.5-4.5%.

4. The corrosion inhibitor for oilfield annular protective fluid according to claim 2, characterized in that, The modified glycidyltrimethylammonium chloride aqueous solution is prepared by the following method: glycidyltrimethylammonium chloride, deionized water, and dipropylene glycol methyl ether are mixed at a mass ratio of 1:5.2:0.35 and stirred at 180-220 rpm for 20-30 min at room temperature to obtain a mixture. 0.05-0.08% by mass of 1,3-benzothiazole-6-sulfonyl chloride is added to the mixture, and the mixture is stirred in the dark for 25-35 min. After standing for 40-60 min, the mixture is filtered, and the filtrate is collected to obtain the modified glycidyltrimethylammonium chloride aqueous solution.

5. The corrosion inhibitor for oilfield annular protective fluid according to claim 1, characterized in that, Additive B is prepared by the following method: a base powder is mixed with quinoline at a mass ratio of 1:(1.2-1.8), heated to 80-100℃ under nitrogen protection, and stirred at 200-300 rpm for 1 hour to obtain a premix. 4-6% of benzyl chloride is added to the premix, the temperature is raised to 110-130℃, and refluxed for 4-6 hours to obtain a second intermediate. The second intermediate is cooled to 70-80℃, and 8-12% of the second intermediate is added to a second mixture. The mixture is kept warm and stirred for 1 hour, and then distilled under reduced pressure for 2-3 hours at an absolute pressure of 0.06-0.08 MPa. After cooling, additive B is obtained. The base powder is petroleum coke-based activated carbon powder, and the second mixture is prepared by isopropanol and ethylene glycol at a mass ratio of 2:

1.

6. The corrosion inhibitor for oilfield annular protective fluid according to claim 5, characterized in that, The base powder is prepared by the following method: high-sulfur petroleum coke with a sulfur content of not less than 2% is pulverized and passed through a 200-mesh sieve to obtain petroleum coke fine powder. The petroleum coke fine powder is added to a composite aqueous solution and impregnated at room temperature for 18-24 hours. After filtration, filter residue is obtained. The filter residue is dried and dehydrated at 85℃-95℃ to constant weight and then placed in a low-temperature plasma device. Under an atmosphere with a chamber pressure of 15-35Pa and an argon flow rate of 30-50sccm, the surface is cleaned and activated using the low-temperature plasma device. The treated filter residue is transferred to a tubular furnace and heated to 800-900℃ at a rate of 5℃ / min under a nitrogen atmosphere. It is then held at this temperature for 1.5-2 hours for activation. After natural cooling, the activated crude product is obtained. The activated crude product is preliminarily washed with deionized water to remove surface dust. It is then directly placed in a 10% hydrochloric acid solution and boiled for 1 hour for acid washing. After filtration, the filter residue is washed with deionized water until neutral and then dried at 105℃ to obtain the basic powder. The mass ratio of the petroleum coke to the composite aqueous solution is 1:(3-5).

7. The corrosion inhibitor for oilfield annular protection fluid according to claim 6, characterized in that, The composite aqueous solution is prepared by the following method: potassium dihydrogen phosphate, sodium metaborate, and dodecantungstic phosphate are mixed at a mass ratio of 100:(3-5):(1.5-2.5) to obtain a mixed product. 3.5-5.7 times the mass of deionized water is added to the mixed product, and the mixture is stirred at 300-400 rpm for 30-40 min and allowed to stand for 2 h to mature, thus obtaining the composite aqueous solution.

8. The corrosion inhibitor for oilfield annular protection fluid according to claim 1, characterized in that, The zinc salt is one of zinc sulfate, zinc chloride, or zinc nitrate.

9. The corrosion inhibitor for oilfield annular protective fluid according to claim 1, characterized in that, The sodium molybdate, sodium gluconate, and zinc salt are all of industrial grade purity, with a mass concentration of not less than 98%.

10. The method for preparing the corrosion inhibitor for oilfield annular protective fluid according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Add water to the reaction vessel and heat it to 40-50℃. While stirring at 300-400 rpm, add sodium gluconate, sodium molybdate and zinc salt in sequence and stir until completely dissolved to obtain a premix. Step 2: Add additive A and additive B to the premix, continue stirring for 40-60 minutes, cool to room temperature, and obtain the corrosion inhibitor for oilfield annular protection fluid.

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