Modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor as well as preparation method and application thereof

Abstract

The invention provides a modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor as well as a preparation method and application thereof, and belongs to the technical field of chemical corrosion prevention of oil and gas fields. The preparation method of the corrosion inhibitor comprises the following steps: carrying out condensation reaction on oleic acid and diethylenetriamine in the presence of a water carrying agent xylene and a catalyst p-toluenesulfonic acid to obtain oleic acid imidazoline; in isopropanol, under the catalysis of potassium iodide, oleic acid imidazoline and chlorododecane are subjected to quaternization modification reaction to obtain oleic acid imidazoline dodecyl quaternary ammonium salt; in water, under the action of a cross-linking agent epoxy chloropropane, the oleic acid imidazoline dodecyl quaternary ammonium salt and sodium silicate are subjected to a cross-linking hybridization reaction to obtain the product. The stability is remarkably improved through quaternization modification of the organic oleic acid imidazoline, the organic oleic acid imidazoline and the inorganic sodium silicate are hybridized and crosslinked to form the hybrid composite corrosion inhibitor, synergistic coverage of an organic adsorption film and an inorganic deposition film is achieved, the corrosion rate is remarkably reduced, and the corrosion inhibition performance and environmental adaptability of the corrosion inhibitor are improved.

Description

Technical Field

[0001] This invention relates to the field of chemical corrosion protection technology in oil and gas fields, specifically to a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor, its preparation method, and its application. Background Technology

[0002] In recent years, with the exploration and development of onshore oil resources reaching a relatively high level, new reserves and production are insufficient to meet the ever-increasing energy demand, making the exploration and development of offshore oil and gas resources a focus of attention. Deep-sea areas, in particular, have become a crucial area for global oil exploration. Statistics show that nearly half of the world's major oil and gas discoveries in recent years have come from deep-sea regions, demonstrating the importance and potential of deep-sea exploration. The exploration and development of deep-sea oil and gas resources is not only a focal point for the oil industry but also a cutting-edge field of current scientific research.

[0003] Offshore drilling environments are far more severe and complex than onshore drilling environments, typically characterized by extreme conditions such as high pressure, high temperature, and high salinity. The presence of acidic corrosive gases like carbon dioxide and hydrogen sulfide, along with microorganisms like sulfate-reducing bacteria, creates a highly destructive corrosive media system. During well completion operations, the completion fluid, as the fluid directly in contact with the producing formation and critical metal equipment such as tubing and casing, is subjected to this harsh environment for extended periods. These corrosive media trigger a series of severe electrochemical corrosions, manifesting in various forms, including uniform corrosion, localized pitting corrosion, crevice corrosion, and even stress corrosion cracking. This directly leads to thinning of the tubing, casing, and production equipment walls, performance degradation, significantly shortening their service life and increasing maintenance costs. Furthermore, structural failure of the tubing string can cause well control safety risks. Corrosion products can also clog the producing formation, ultimately affecting the production capacity and safe operation of oil and gas wells.

[0004] Corrosion inhibitors are crucial additives in completion fluid systems. Their core application goal is to suppress the corrosion of downhole metal equipment, especially casing, tubing, and downhole tools, by the completion fluid. They form a dense protective film on the metal surface, effectively preventing corrosive media from contacting the substrate. Specifically, the polar groups of these corrosion inhibitor molecules are directionally adsorbed onto the metal surface, while the non-polar groups extend outwards, forming a hydrophobic barrier; or they react with metal ions to form an insoluble passivation film, fundamentally altering the electrochemical properties of the metal surface and inhibiting anodic metal dissolution or cathodic depolarization reactions. Through scientific screening and formulation (e.g., using imidazoline, quaternary ammonium salts, phosphate esters, etc., corrosion inhibitors tailored to different corrosive environments) and effectively dispersing them in the completion fluid system, corrosion rates can be reduced by over 90%, extending pipe life by 3 to 5 times. This provides continuous protection for the target metal equipment throughout the entire completion operation cycle and even the subsequent shut-in period, which has irreplaceable strategic significance for ensuring long-term safe production of oil and gas wells, reducing maintenance costs, and maximizing return on investment.

[0005] Single inorganic corrosion inhibitors require large quantities in seawater, but their corrosion inhibition is not sustainable and can easily cause environmental pollution. Single organic corrosion inhibitors have low corrosion inhibition efficiency in seawater and are expensive, limiting their application. For example, Chinese patent document CN103603003A discloses a metal cleaning solution, which involves a corrosion inhibitor composed of a gemini cationic imidazoline quaternary ammonium salt and O,O'-diphenyldithiophosphate-N,N-diethylammonium. The technical solution is essentially a synergistic effect of two specific organic corrosion inhibitors, but this synergy stems from the co-adsorption of different molecules on the metal surface under physical mixing. Stable chemical bonds are not formed between the molecules, therefore the resulting protective film is weaker in stability and tolerance than that of molecular structures directly constructed through chemical bonds. Secondly, the corrosion protection provided by this system relies entirely on the adsorption of the two organic molecules on the metal surface, forming a typical "single-layer protection" mechanism. Once this adsorption film is damaged or its coverage decreases due to temperature fluctuations, fluid erosion, or local pH changes, the underlying metal substrate will be directly exposed to the corrosive medium. Furthermore, both components are organic corrosion inhibitors with similar mechanisms of action and lack functional complementarity. These characteristics collectively limit the potential and adaptability of this compound system in dealing with more complex and harsh corrosive environments.

[0006] Therefore, developing a corrosion inhibitor that can be stable for a long time under extreme marine conditions, has excellent corrosion inhibition performance, is environmentally friendly and low in toxicity, and has a simple preparation process and controllable cost has become an urgent need in the field of chemical corrosion prevention in oil and gas fields. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor, its preparation method, and its application. This invention significantly improves stability through quaternization modification of organic oleic acid imidazoline and forms a hybrid composite corrosion inhibitor through hybrid cross-linking with inorganic sodium silicate. This achieves synergistic coverage of an "organic adsorption film + inorganic deposition film," significantly reducing the corrosion rate and improving the corrosion inhibition performance and environmental adaptability of the inhibitor.

[0008] The technical solution of the present invention is as follows: A method for preparing a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor includes the following steps: (1) In the presence of xylene as a water-carrying agent and p-toluenesulfonic acid as a catalyst, oleic acid and diethylenetriamine undergo a condensation reaction to obtain oleic acid imidazoline; (2) In isopropanol, under the catalysis of potassium iodide, oleic acid imidazoline and chlorododecane are subjected to a quaternization modification reaction to obtain oleic acid imidazoline dodecyl quaternary ammonium salt; (3) In water, under the action of the crosslinking agent epichlorohydrin, oleic acid imidazoline dodecyl quaternary ammonium salt and sodium silicate undergo a crosslinking hybrid reaction, and then the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor is obtained by centrifugation, washing and drying.

[0009] According to a preferred embodiment of the present invention, in step (1), the molar amount of oleic acid and the volume ratio of xylene are 5-10 mol / L, preferably 6.7 mol / L; the molar amount of p-toluenesulfonic acid is 0.5-2% of the molar amount of oleic acid, preferably 0.95%; and the molar ratio of oleic acid to diethylenetriamine is 1:1-1.5, preferably 1:1.2.

[0010] According to a preferred embodiment of the present invention, in step (1), diethylenetriamine is added to the reaction system dropwise.

[0011] According to a preferred embodiment of the present invention, in step (1), the condensation reaction conditions are as follows: reaction at 140-150℃ for 1-3 h, followed by reaction at 200-220℃ for 2-4 h; the reaction is carried out under stirring conditions.

[0012] According to a preferred embodiment of the present invention, in step (1), the reaction solution obtained by the condensation reaction is distilled under reduced pressure to obtain oleic acid imidazoline.

[0013] According to a preferred embodiment of the present invention, in step (1), the preparation method of oleic acid imidazoline includes the following steps: mixing oleic acid, xylene (a water-carrying agent), and p-toluenesulfonic acid (a catalyst), heating to 140-150°C, adding diethylenetriamine dropwise under stirring conditions, stirring at 140-150°C for 1-3 h after the addition is complete, continuing to heat to 200-220°C and stirring for 2-4 h, and obtaining oleic acid imidazoline by vacuum distillation.

[0014] According to a preferred embodiment of the present invention, in step (2), the mass ratio of oleic acid imidazoline to isopropanol is 1-3:1, preferably 2:1.

[0015] According to a preferred embodiment of the present invention, in step (2), the mass of potassium iodide is 0.1-0.5% of the mass of imidazoline oleate, preferably 0.33%.

[0016] According to a preferred embodiment of the present invention, in step (2), the mass ratio of oleic acid imidazoline to chlorododecane is 1:0.4-0.5, preferably 1:0.453; chlorododecane is added to the reaction system dropwise.

[0017] According to a preferred embodiment of the present invention, in step (2), the quaternization modification reaction temperature is 80-90℃, the reaction time is 3-5h, and the reaction is carried out under reflux stirring and protective gas protection. The protective gas is nitrogen or argon.

[0018] According to a preferred embodiment of the present invention, in step (2), the reaction obtained by the quaternization modification reaction is obtained by rotary evaporation to obtain oleic acid imidazoline dodecyl quaternary ammonium salt.

[0019] According to a preferred embodiment of the present invention, in step (2), the preparation method of oleic acid imidazoline dodecyl quaternary ammonium salt includes the following steps: mixing oleic acid imidazoline, isopropanol and potassium iodide, heating to 80-90°C, adding chlorododecane dropwise under stirring and protective gas protection, and after the addition is completed, refluxing and stirring at 80-90°C for 3-5 h, and rotary evaporating to obtain oleic acid imidazoline dodecyl quaternary ammonium salt.

[0020] According to a preferred embodiment of the present invention, in step (3), the mass ratio of sodium silicate to water is 1:2-20, preferably 1:20; the mass ratio of epichlorohydrin to sodium silicate is 0.43-4.3:1, preferably 4.3:1; and the mass ratio of oleic acid imidazoline dodecyl quaternary ammonium salt to sodium silicate is 0.6-6:1, preferably 6:1.

[0021] According to a preferred embodiment of the present invention, in step (3), the crosslinking hybridization reaction temperature is 60-70°C, the reaction time is 4-8h, and the reaction is carried out under stirring conditions.

[0022] According to a preferred embodiment of the present invention, in step (3), the preparation method of the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor includes the following steps: dissolving sodium silicate in water, adding epichlorohydrin, and mixing thoroughly; adding oleic acid imidazoline dodecyl quaternary ammonium salt, stirring and reacting at 60-70°C for 4-8 hours, and then centrifuging, washing, and drying to obtain the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor.

[0023] A modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor is prepared by the above method.

[0024] The above-mentioned modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor is applied to marine oil and gas completion fluids to reduce downhole corrosion rates, while improving the corrosion resistance of drill bits and enhancing the safety of seawater operations.

[0025] The technical features and beneficial effects of this invention are as follows: 1. This invention synthesizes oleic acid imidazoline using oleic acid and diethylenetriamine in the presence of xylene as a water-carrying agent and p-toluenesulfonic acid as a catalyst. The oleic acid imidazoline is then modified by quaternization with dodecyl chloride. Finally, the oleic acid imidazoline dodecyl quaternary ammonium salt is cross-linked with sodium silicate using epichlorohydrin as a cross-linking agent to obtain a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor suitable for marine oil and gas well completion fluids. This invention features a simple preparation method, inexpensive and readily available raw materials, environmental friendliness and low toxicity, and highly efficient corrosion inhibition capabilities.

[0026] 2. The modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor prepared in this invention works based on the "synergistic effect" and "dual film formation" mechanism between organic and inorganic components, such as... Figure 2 As shown.

[0027] The hybrid composite corrosion inhibitor of the present invention is constructed through three consecutive chemical reactions, the core of which lies in combining organic and inorganic components into a whole through covalent bonds.

[0028] The carboxyl group of oleic acid undergoes dehydration condensation with the primary amino group of diethylenetriamine to form an amide bond, followed by intramolecular cyclization at high temperature to generate oleic acid imidazoline. Quaternization modification is then performed: the tertiary nitrogen atom of the imidazoline ring undergoes a nucleophilic substitution reaction with dodecyl chloride to form a positively charged quaternary ammonium salt structure. Therefore, in the final product, the five-membered imidazoline ring and long-chain alkyl group of this component can chemically adsorb onto the metal surface through the lone pair electrons on the nitrogen atom. Simultaneously, the hydrophobic long carbon chain is oriented on the metal surface, forming a dense, hydrophobic organic adsorption monolayer that effectively blocks corrosive media such as water, chloride ions, and dissolved oxygen. Furthermore, the quaternary ammonium group not only enhances water solubility and dispersibility, but its positive charge also allows for strong electrostatic adsorption onto the negatively charged metal surface, improving coverage and stability, and also possessing a certain bactericidal effect.

[0029] The inorganic component, sodium silicate, is introduced into the system through a cross-linking hybrid reaction: after the epoxy group of the cross-linking agent epichlorohydrin undergoes ring-opening, one end of its active intermediate condenses with the inorganic sodium silicate phase to form a strong Si-OC bond, while the other end reacts with the molecular chain of the organic phase, oleic acid imidazoline dodecyl quaternary ammonium salt, to form a COC or CN bond. Through this "bridging," the organic and inorganic components form a stable three-dimensional hybrid network structure, rather than a simple physical mixture. During the protection process, the silicate ions in this hybrid structure can react with metal ions (such as Fe) dissolved during corrosion. 2+The reaction produces insoluble iron silicate and other complexes, which are deposited on the metal surface or at defects in organic films, thus forming a strong inorganic deposition protective film.

[0030] This invention achieves highly efficient corrosion inhibition by constructing a synergistic protective layer of "organic adsorption film + inorganic deposition film" on the metal surface. The dense organic film acts as the main barrier to block corrosive media, while the inorganic film can actively repair microscopic defects or damage points that the organic film cannot cover. This dual protection mechanism, derived from chemical hybridization, enables it to maintain extremely high corrosion inhibition efficiency and excellent environmental adaptability even under extreme conditions such as high temperature and high mineralization.

[0031] 3. Experiments of this invention demonstrate that the corrosion inhibitor system formed by the hybrid composite of oleic acid imidazoline quaternary ammonium salt and sodium silicate achieves a corrosion inhibition rate as high as 96.34% at room temperature; 82.18% at high temperature (210℃); and 91.35% at high salinity (250,000 mg / L). In the simulated completion fluid system, the corrosion inhibition rate reaches 93.44%, exhibiting a very outstanding corrosion inhibition effect and excellent environmental adaptability. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope image of the steel sheet surface after the corrosion test in Example 1. Figure 2 This is a schematic diagram illustrating the corrosion inhibition mechanism of the hybrid composite corrosion inhibitor of the present invention; Figure 3 This is a comparison of the surface corrosion of steel sheets under different mineralization levels in Experiment Example 3. Detailed Implementation

[0033] This invention, through extensive experimental screening, determined the optimal mass ratio range of oleic acid imidazoline quaternary ammonium salt to sodium silicate. To illustrate this invention in detail, but without limiting its scope, several representative embodiments are provided below.

[0034] Furthermore, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods; and unless otherwise specified, the reagents, materials and equipment are all commercially available.

[0035] Example 1 A method for preparing a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor includes the following steps: (1) At 25°C, 64 mL (0.20 mol) of oleic acid, 30 mL of xylene as a water-carrying agent and 0.32 g (0.0019 mol) of p-toluenesulfonic acid as a catalyst were added to a three-necked flask, and 24 mL (0.24 mol) of diethylenetriamine was added to a dropping funnel and condenser water was introduced.

[0036] (2) Turn on the electric heating mantle to heat and stir, raise the temperature to 140°C, and add diethylenetriamine dropwise to the reaction system through a constant pressure dropping funnel. After the addition is completed, stir the reaction for 2 h.

[0037] (3) Continue heating to 200℃, keep the temperature constant and stir the reaction for 3 h, then cool to 140℃, and use a vacuum pump to distill under reduced pressure for 0.5 h to separate the excess diethylenetriamine and water-carrying agent xylene to obtain oleic acid imidazoline.

[0038] (4) 100 g of the synthesized oleic acid imidazoline, 50 g of isopropanol and 0.33 g of potassium iodide catalyst were added to a 250 mL three-necked flask and placed in a constant temperature oil bath. The temperature was set to 80 °C and the rotation speed was 300 rpm. Nitrogen gas was continuously introduced for 30 min to remove the air in the flask. At the same time, stirring was continued. 45.3 g of chlorododecane was added dropwise to the three-necked flask at a rate of 1 second / drop. After the addition was completed, the reaction was continued to be stirred under reflux at 80 °C for 4 h. Heating was stopped, and the isopropanol and unreacted chlorododecane were removed by rotary evaporation at 50 °C for 30 min. A viscous brownish-yellow liquid was obtained, which is the oleic acid imidazoline dodecyl quaternary ammonium salt.

[0039] (5) Dissolve 1.5 g of sodium silicate in 30 mL of deionized water, sonicate at 40 °C for 30 min, add 6.5 g of epichlorohydrin, and magnetically stir at 60 °C for 3 h to form a sodium silicate-epoxychlorohydrin mixed solution. Add 9 g of oleic acid imidazoline dodecyl quaternary ammonium salt to the sodium silicate-epoxychlorohydrin mixed solution, and magnetically stir at 300 rpm at 65 °C for 6 h to crosslink the epichlorohydrin and oleic acid imidazoline dodecyl quaternary ammonium salt to form a mixed solution. Centrifuge the mixture, wash the lower precipitate three times with deionized water, and dry at 60 °C for 24 h to finally obtain the hybrid composite corrosion inhibitor.

[0040] Example 2 A method for preparing a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor is as described in Example 1, except that: in step (5), the amount of sodium silicate used is 9 g; other steps and conditions are the same as in Example 1.

[0041] Example 3 A method for preparing a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor is as described in Example 1, except that: in step (5), the amount of sodium silicate used is 15 g; other steps and conditions are the same as in Example 1.

[0042] Comparative Example 1 A method for preparing a corrosion inhibitor is as described in Example 3, except that step (5) is omitted, while the other steps and conditions are the same as in Example 3, and the resulting product is a single oleic acid imidazoline dodecyl quaternary ammonium salt.

[0043] Comparative Example 2 A method for preparing a corrosion inhibitor, as described in Example 3, differs in that: the organic component synthesis and quaternization reaction in steps (1) to (4) are not carried out, and only the process of reacting sodium silicate with the crosslinking agent epichlorohydrin in step (5) is retained, and the final product is a sodium silicate crosslinker.

[0044] The specific steps are as follows: 15 g of sodium silicate was dissolved in 30 mL of deionized water and sonicated at 40 °C for 30 min. 6.5 g of epichlorohydrin was added, and the mixture was magnetically stirred at 60 °C for 3 h to form a sodium silicate-epoxychlorohydrin mixed solution. Then, the mixture was magnetically stirred at 300 rpm at 65 °C for 6 h. The mixture was centrifuged, and the lower precipitate was washed three times with deionized water. Finally, the mixture was dried at 60 °C for 24 h to obtain the sodium silicate crosslinked product.

[0045] Comparative Example 3 A method for preparing a corrosion inhibitor is described in Example 3, except that the hybrid crosslinking reaction of sodium silicate and oleic acid imidazoline dodecyl quaternary ammonium salt in step (5) is not performed; instead, sodium silicate, the crosslinking agent epichlorohydrin, and oleic acid imidazoline dodecyl quaternary ammonium salt are physically mixed and compounded. Other steps and conditions are the same as in Example 3.

[0046] Step (5) is as follows: 15 g of sodium silicate was dissolved in 30 mL of deionized water and sonicated at 40 °C for 30 min to form an aqueous sodium silicate solution. Then, under room temperature (25 °C) and magnetic stirring at 300 rpm, 6.5 g of epichlorohydrin and 9 g of oleic acid imidazoline dodecyl quaternary ammonium salt were added sequentially to the above aqueous sodium silicate solution. The mixture was stirred continuously at room temperature for 30 minutes to ensure thorough mixing. The resulting mixture was centrifuged, and the lower precipitate was washed three times with deionized water. The mixture was then dried at 60 °C for 24 h to obtain a physical compound mixture of sodium silicate-epoxychlorohydrin-quaternary ammonium salt.

[0047] Comparative Example 4 A method for preparing a corrosion inhibitor, as described in Example 3, differs in that: the quaternizing agent dodecyl chloride in step (4) is replaced with benzyl chloride, and after quaternization, oleic acid imidazoline benzyl quaternary ammonium salt is obtained, which is then subjected to the hybrid crosslinking reaction in step (5) with sodium silicate and crosslinking agent epichlorohydrin, and the final product is a benzyl quaternary ammonium salt-sodium silicate hybrid composite corrosion inhibitor.

[0048] The specific steps are as follows: Steps (1)-(3) are the same as in Example 3; (4) Add 100 g of synthesized oleic acid imidazoline and 40 g of isopropanol to a 250 mL three-necked flask, place it in a constant temperature water bath, set the temperature to 70 ℃ and the rotation speed to 300 rpm, continuously purge nitrogen gas for 30 min to remove air from the flask, and continue stirring. Add 34 g of benzyl chloride dropwise to the three-necked flask at a rate of 2 seconds / drop. After the addition is complete, continue the reaction at 70 ℃ for 2 h. Stop heating, reduce the pressure to 50 ℃ and rotary evaporate for 30 min to remove isopropanol and unreacted benzyl chloride, and obtain a brownish-yellow liquid, which is oleic acid imidazoline benzyl quaternary ammonium salt.

[0049] (5) Dissolve 15 g of sodium silicate in 30 mL of deionized water, sonicate at 40 °C for 30 min, add 6.5 g of epichlorohydrin, and magnetically stir at 60 °C for 3 h to form a sodium silicate-epoxychlorohydrin mixed solution. Add 9 g of oleic acid imidazoline benzyl quaternary ammonium salt to the sodium silicate-epoxychlorohydrin mixed solution, and magnetically stir at 300 rpm at 65 °C for 6 h to crosslink the epichlorohydrin and oleic acid imidazoline benzyl quaternary ammonium salt to form a mixed solution. Centrifuge the mixture, wash the lower precipitate three times with deionized water, and dry at 60 °C for 24 h to finally obtain the benzyl quaternary ammonium salt-sodium silicate hybrid corrosion inhibitor.

[0050] Experimental Example 1 Referring to HG / T 2159-91 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Plate Method", the corrosion inhibition performance of the corrosion inhibitors prepared in the examples and comparative examples was determined at room temperature using a type II (72.4×11.5×2mm) Q235 steel plate. The experimental results are shown in Table 1. Sample preparation: The corrosion inhibitors prepared in the examples and comparative examples were mixed with pure water, wherein the mass concentration of the corrosion inhibitor was 1%.

[0051] Table 1 Corrosion inhibition at room temperature (25℃) This experiment systematically verified the effects of different structural designs and preparation processes on corrosion inhibition performance under ambient temperature conditions. Data shows that the product prepared by the chemical hybridization process (Example 3) achieved a corrosion inhibition rate of 96.34%, exhibiting significantly better performance characteristics than single-component systems. Compared to Comparative Example 1 (81.71%) containing only organic components and Comparative Example 2 (47.17%) containing only inorganic components, the performance improvement of Example 3 confirms the synergistic enhancement effect produced by the organic-inorganic hybrid system. In particular, the performance of Example 3 is significantly better than that of the physically mixed compound system Comparative Example 3 (80.49%) and the benzyl quaternary ammonium salt hybrid product Comparative Example 4 (82.93%). This significant performance difference indicates that the stable network structure formed during the chemical hybridization process and the specific molecular configuration of dodecyl groups play a crucial role in improving the integrity and density of the protective film, rather than being achieved by simple component superposition.

[0052] Figure 1 The images are scanning electron microscope (SEM) images of the steel sheet surface after the corrosion test. In the image, a represents Example 3, and b to e represent Comparative Examples 1 to 4, respectively. It can be clearly seen that the addition of Example 3 forms a good protective layer on the steel sheet surface, while the addition of Comparative Examples 1 to 4 has a protective effect on the steel sheet surface, but obvious corrosion marks appear on the steel sheet surface. In particular, the steel sheet surface with the addition of Comparative Example 2 is severely corroded.

[0053] Experimental Example 2 Referring to HG / T 2159-91 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Dropper Method", corrosion inhibitors were added under high temperature conditions, and the corrosion was measured using a type II (72.4×11.5×2mm) Q235 steel strip. The experimental results are shown in Tables 2-5. Sample preparation: The corrosion inhibitors prepared in the examples and comparative examples were mixed with pure water, wherein the mass concentration of the corrosion inhibitor was 1%.

[0054] Table 2 Corrosion inhibition of 1% Example 3 at high temperature Table 3. Corrosion inhibition of 1% Comparative Example 1 at high temperature. Table 4. Corrosion inhibition of 1% Comparative Example 3 at high temperatures. Table 5. Corrosion inhibition of 1% Comparative Example 4 at high temperature. This experimental example reveals the performance stability of different systems under high-temperature conditions through temperature gradient testing. Data shows that the hybrid product of this invention, Example 3, maintains an 82.18% corrosion inhibition rate at 210℃, and its performance curve is flat within the 120-210℃ temperature range, indicating that its protective film structure has excellent thermal stability. In contrast, the physical hybrid system, Comparative Example 3, shows a significant performance degradation within the same temperature range (from 70.73% to 38.33%), reflecting the inherent limitation of physical hybrid systems lacking chemical bonds, which are easily damaged at high temperatures. Meanwhile, the performance of the benzyl quaternary ammonium salt hybrid product, Comparative Example 4, at high temperatures (59.23%) is significantly lower than that of the dodecyl system, indicating that the long-chain structure of dodecyl has a unique advantage in maintaining molecular order and film integrity at high temperatures. These results demonstrate that the corrosion inhibitor represented by Example 3 of this invention has superior durability and reliability under high-temperature conditions, making it suitable for high-temperature applications requiring high corrosion inhibition performance. They also confirm the synergistic effect of specific molecular structures and chemical hybridization processes from a thermal stability perspective.

[0055] Experimental Example 3 Referring to HG / T 2159-91 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Dropper Method", corrosion inhibitors were added at different salinities and room temperature (25℃), and the results were measured using a type II (72.4×11.5×2mm) Q235 steel strip. The experimental results are shown in Tables 6 to 9. Sample preparation: The corrosion inhibitors prepared in the examples and comparative examples were mixed with water of different salinities to prepare the sample, wherein the mass concentration of the corrosion inhibitor was 1%.

[0056] Table 6. Corrosion inhibition of 1% Example 3 at different mineralization levels. Table 7. Corrosion inhibition of 1% Comparative Example 2 under different mineralization degrees. Table 8. Corrosion inhibition of 1% Comparative Example 3 under different mineralization degrees. Table 9. Corrosion inhibition of 1% Comparative Example 4 under different mineralization degrees. This experiment investigated the tolerance of different systems to high ionic strength environments. The data shows that, although the corrosion inhibition rate of the hybrid product of this invention (Example 3) fluctuated slightly with increasing mineralization, the overall corrosion inhibition rate remained above 90%, indicating that its protective film has excellent resistance to ion penetration. In contrast, the corrosion inhibition performance of Comparative Example 2 deteriorated sharply with increasing mineralization. The performance of the physically mixed system (Comparative Example 3) decreased significantly with increasing mineralization (from 80.49% to 71.95%), reflecting the structural instability of the non-chemically bonded system when resisting high-concentration ion impacts. The benzyl quaternary ammonium salt hybrid product (Comparative Example 4) also showed a similar trend, but its overall performance was significantly lower than that of Example 3, further confirming that the long-chain hydrophobic structure of dodecyl groups can construct a dense barrier and prevent ion penetration.

[0057] Figure 3 The corrosion of steel sheets under different mineralization levels (mineralization increases from left to right) is shown in (a) with the addition of Example 3, where it is clear that the corrosion inhibitor of the present invention has a good corrosion inhibition effect, and the steel sheet surface still has a metallic luster. (b) with the addition of Comparative Example 2, the steel sheet corrosion is obvious, and obvious rust appears on the surface.

[0058] Test Example 4 Corrosion inhibition performance was evaluated at room temperature (25℃) under simulated seawater completion fluid conditions. The standard seawater completion fluid (base slurry) formulation was used as the corrosion medium. Its composition was self-made seawater (simulated seawater salinity 350,000 mg / L), 0.1wt% XC (thickening agent), 1.5wt% PAC-LV (filtration loss reducer), 1wt% PVCap (hydrate inhibitor) and 1wt% corrosion inhibitor. The experimental results are shown in Table 10.

[0059] Table 10 Simulated seawater completion fluid corrosion inhibition conditions This experiment verified the applicability of each system in a complex system simulating actual working conditions. Data shows that Example 3 of this invention maintained a high corrosion inhibition rate of 93.44% in a completion fluid system containing multiple additives. Furthermore, the completion fluid system with the corrosion inhibitor from Example 3, after standing at room temperature for 24 hours, was homogeneous and stable, with no precipitation, stratification, or flocculation observed, indicating good compatibility with the completion fluid components and that the protective film maintained its complete function in complex media. In contrast, the performance of single organic components (Comparative Example 1, 77.87%), physically mixed systems (Comparative Example 3, 75.41%), and other structural hybrid products (Comparative Example 4, 77.05%) was significantly lower. This reflects the stronger adaptability and structural retention ability of the stable network structure formed by the chemical hybridization of this invention in complex media environments.

Claims

1. A method for preparing a modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor, comprising the following steps: (1) In the presence of xylene as a water-carrying agent and p-toluenesulfonic acid as a catalyst, oleic acid and diethylenetriamine undergo a condensation reaction to obtain oleic acid imidazoline; (2) In isopropanol, under the catalysis of potassium iodide, oleic acid imidazoline and chlorododecane are subjected to a quaternization modification reaction to obtain oleic acid imidazoline dodecyl quaternary ammonium salt; (3) In water, under the action of the crosslinking agent epichlorohydrin, oleic acid imidazoline dodecyl quaternary ammonium salt and sodium silicate undergo a crosslinking hybrid reaction, and then the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor is obtained by centrifugation, washing and drying.

2. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The molar amount of oleic acid and the volume ratio of xylene are 5-10 mol / L, preferably 6.7 mol / L; the molar amount of p-toluenesulfonic acid is 0.5-2% of the molar amount of oleic acid, preferably 0.95%; the molar ratio of oleic acid to diethylenetriamine is 1:1-1.5, preferably 1:1.

2. ii. Diethylenetriamine is added dropwise to the reaction system; iii. The condensation reaction conditions are as follows: react at 140-150℃ for 1-3 h, then at 200-220℃ for 2-4 h; the reaction is carried out under stirring conditions.

3. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, In step (1), the preparation method of oleic acid imidazoline includes the following steps: oleic acid, xylene (a water-carrying agent), and p-toluenesulfonic acid (a catalyst) are mixed, heated to 140-150℃, and diethylenetriamine is added dropwise under stirring. After the addition is complete, the mixture is stirred at 140-150℃ for 1-3 h, and then heated to 200-220℃ for 2-4 h. The mixture is then distilled under reduced pressure to obtain oleic acid imidazoline.

4. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. The mass ratio of imidazoline oleate to isopropanol is 1-3:1, preferably 2:1; ii. The mass of potassium iodide is 0.1-0.5% of the mass of imidazoline oleate, preferably 0.33%; iii. The mass ratio of oleic acid imidazoline to chlorododecane is 1:0.4-0.5, preferably 1:0.453; chlorododecane is added to the reaction system dropwise. iv. The quaternization modification reaction temperature is 80-90℃, the reaction time is 3-5h, and the reaction is carried out under reflux stirring and protective gas protection; the protective gas is nitrogen or argon.

5. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, In step (2), the preparation method of oleic acid imidazoline dodecyl quaternary ammonium salt includes the following steps: oleic acid imidazoline, isopropanol and potassium iodide are mixed, the temperature is raised to 80-90℃, chlorododecane is added dropwise under stirring and protective gas protection, and after the addition is completed, the mixture is refluxed and stirred at 80-90℃ for 3-5 h, and oleic acid imidazoline dodecyl quaternary ammonium salt is obtained by rotary evaporation.

6. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, In step (3), the mass ratio of sodium silicate to water is 1:2-20, preferably 1:20; the mass ratio of epichlorohydrin to sodium silicate is 0.43-4.3:1, preferably 4.3:1; and the mass ratio of oleic acid imidazoline dodecyl quaternary ammonium salt to sodium silicate is 0.6-6:1, preferably 6:

1.

7. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, In step (3), the cross-linking hybridization reaction temperature is 60-70℃, the reaction time is 4-8h, and the reaction is carried out under stirring conditions.

8. The preparation method of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor according to claim 1, characterized in that, In step (3), the preparation method of the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor includes the following steps: dissolving sodium silicate in water, adding epichlorohydrin, and mixing thoroughly; adding oleic acid imidazoline dodecyl quaternary ammonium salt, stirring and reacting at 60-70℃ for 4-8 hours, and then centrifuging, washing, and drying to obtain the modified oleic acid imidazoline-sodium silicate hybrid composite corrosion inhibitor.

9. A modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor, characterized in that, It is prepared by the above method.

10. The application of the modified oleic acid imidazoline-sodium silicate hybrid corrosion inhibitor as described in claim 9, characterized in that, It is used in marine oil and gas completion fluids to reduce downhole corrosion rates, while improving the corrosion resistance of drill bits and enhancing the safety of seawater operations.

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