Composite bactericidal corrosion inhibitor suitable for flow-back fluid with complex components and preparation method of composite bactericidal corrosion inhibitor

Abstract

The invention discloses a composite bactericidal corrosion inhibitor suitable for flow-back fluid with complex components and a preparation method of the composite bactericidal corrosion inhibitor, and belongs to the technical field of petrochemical industry. The composite bactericidal corrosion inhibitor comprises alkyl imidazoline or alkenyl imidazoline, halogenated amide and a solvent, can effectively inhibit corrosion caused by sulfate reducing bacteria, chloride ions and the like, and has a bactericidal function. The use of the traditional bactericide in the flowback fluid only depends on a single component and lacks a synergistic interaction effect, so that the effect is poor, and sterilization and corrosion inhibition cannot be realized at the same time. According to the preparation method disclosed by the invention, the optimized solvent enables the immiscible alkyl imidazoline or alkenyl imidazoline and the halogenated amide to be mixed and dissolved and then act together to achieve a synergistic effect, so that the efficient composite bactericidal corrosion inhibitor with corrosion inhibition and bactericidal functions is prepared. The composite bactericidal corrosion inhibitor effectively solves the problems that a traditional bactericide is single in use function, short in service life, poor in bactericidal effect and difficult to apply to flowback fluid with complex components.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, and in particular to a composite bactericidal corrosion inhibitor suitable for flowback fluid with complex components and a preparation method thereof. Background Art

[0002] With the development of unconventional oil and gas resources, hydraulic fracturing technology has been widely used in the extraction of shale gas, shale oil, and other resources. In the high-temperature, high-pressure underground environment, when fracturing fluid comes into contact with the formation, it produces a large amount of complex flowback fluid. This flowback fluid often contains salts (such as chlorides and bromides), low concentrations of metal ions (such as barium and strontium), toxic non-metallic elements (such as arsenic and selenium), and even radioactive elements (such as radium), as well as organic compounds such as phenol and alkanes, and microorganisms such as sulfate-reducing bacteria and iron bacteria. Therefore, to effectively utilize water resources, hydraulic fracturing technology often recycles the flowback fluid, that is, after simple treatment, it is reused in the fracturing process, resulting in a more complex composition of the flowback fluid.

[0003] The presence of sulfate-reducing bacteria is one of the main causes of pipeline corrosion. This type of anaerobic microorganism generates hydrogen sulfide by reducing sulfate. Hydrogen sulfide is not only highly corrosive to metal pipelines, but also reduces the quality and safety of oil and gas production. In addition, salts such as chloride ions are also important inducements to corrosion, especially in flowback fluids, where the concentration of chloride ions is often high. Chloride ions and other substances can destroy the passivation film on the metal surface, promote local electrochemical corrosion, and lead to a significant increase in the corrosion rate of pipelines and equipment. In an environment with high salt concentration, the corrosive effect of chloride ions and other substances is particularly prominent, and often synergizes with other corrosion factors to aggravate corrosion problems and threaten equipment safety and production stability during oil and gas extraction. Conventional fungicides and corrosion inhibitors are usually used alone, and have the problems of single action and insufficient synergistic effect, making it difficult to achieve long-term bactericidal and anti-corrosion effects at the same time.

[0004] Although some composite bactericidal and corrosion inhibitors have been disclosed in the prior art, they are generally not formulated and adjusted to the complex composition of actual flowback fluids, making it difficult to achieve optimal compatibility, corrosion inhibition, and bactericidal effects, resulting in poor practical application results. Therefore, there is an urgent need to provide a new, highly effective, synergistic bactericidal and corrosion inhibitor specifically for use in flowback fluids from slickwater volume fracturing in complex environments, to address pipeline corrosion caused by sulfate-reducing bacteria, chloride ions, and other factors. Summary of the Invention

[0005] In order to address the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a composite bactericidal corrosion inhibitor suitable for return fluids with complex components and a preparation method thereof, so as to provide a new type of bactericidal corrosion inhibitor with high-efficiency synergistic effect, which is specifically used in the return fluid of slippery water volume fracturing in complex environments to solve the pipeline corrosion problem caused by sulfate-reducing bacteria, chloride ions, etc.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: providing a composite bactericidal corrosion inhibitor suitable for return fluid with complex components, comprising the following components: alkyl imidazoline or alkenyl imidazoline, halogenated amide and solvent.

[0007] Furthermore, the mass ratio of the alkyl imidazoline or alkenyl imidazoline, the halogenated amide and the solvent is 1-4:1:1-2.

[0008] Furthermore, the mass ratio of the alkyl imidazoline or alkenyl imidazoline, the halogenated amide and the solvent is 1.6:1:1.9.

[0009] Furthermore, the alkenyl imidazoline is polyvinyl imidazoline or heptadecenylamine ethyl imidazoline quaternary ammonium salt, and the alkyl imidazoline is N-octadecyl imidazoline.

[0010] Furthermore, the halogenated amide includes at least one of 2,2-dibromo-3-nitrilopropionamide, 2,2-dibromo-3-cyanopropionamide, 2,2-dibromomalonamide, thiofluanid and diclofenac.

[0011] Furthermore, the solvent includes at least one of ethanol, OP-10, NP-10, sodium lauryl sulfate, glutaraldehyde, methanol and isopropyl alcohol.

[0012] The present invention provides a method for preparing the composite bactericidal corrosion inhibitor, comprising the following steps: (1) dissolving the halogenated amide in a solvent to prepare a halogenated amide solution; (2) heating the alkyl imidazoline or alkenyl imidazoline and halogenated amide solutions separately and then subjecting them to nitrogen treatment; (3) The product obtained in step (2) was stirred and mixed, and then subjected to ultrasonic treatment; and then reacted in a water bath under nitrogen flow for 1-1.5 hours; (4) Cooling the product obtained in step (3) and filtering it to obtain.

[0013] Furthermore, the heating temperature in step (2) is 30-70° C.; and the nitrogen treatment is specifically: nitrogen is passed through at a nitrogen flow rate of 10-40 mL / min for 5-20 minutes.

[0014] Furthermore, the frequency of the ultrasonic treatment in step (3) is 15-50 kHz, and the time is 15-30 minutes; the nitrogen treatment is specifically: nitrogen is passed at a nitrogen flow rate of 20-30 mL / min for 30-40 minutes.

[0015] Furthermore, the filtration in step (4) is specifically: filtering through a 0.22-0.45 μm microporous filter membrane.

[0016] The present invention has the following beneficial effects: (1) The composite bactericidal corrosion inhibitor of the present invention combines the dual functions of bactericidal and corrosion inhibition, and can play a continuous role in the flowback fluid, overcoming the problems of limited effect and short service life of traditional single-component bactericides, and filling the gap of composite bactericidal corrosion inhibitors that are not designed for flowback fluid. It can effectively inhibit the activity of sulfate-reducing bacteria in the flowback fluid with complex components with a small dosage (80ppm), and the bactericidal rate can reach more than 99.99%; when the concentration of the composite bactericidal corrosion inhibitor is 80mg / L, the corrosion inhibition rate can reach a maximum of 84.34%, and the corrosion rate is reduced to 0.0316mm / a, which is much lower than the 0.076mm / a in the industry standard SY / T 0611-2018. Therefore, the composite bactericidal corrosion inhibitor of the present invention has the characteristics of good compatibility with the flowback fluid with complex components, small dosage and high bactericidal corrosion inhibition rate.

[0017] (2) The present invention uses ethanol, OP-10, etc. as solvents to dissolve and mix the incompatible alkyl imidazoline or alkenyl imidazoline and halogenated amide, thereby producing a synergistic effect and improving the bactericidal and corrosion inhibition capabilities: ① Alkyl imidazoline or alkenyl imidazole compounds physically destroy the cell membrane of microorganisms, making them more accessible to the oxidizing components of halogenated amide compounds; halogenated amide compounds, through the strong oxidizing properties of halogens, destroy the cell metabolic system of microorganisms, damage the enzyme system and DNA, and achieve multi-target sterilization, thereby improving the membrane penetration efficiency of alkyl imidazoline or alkenyl imidazoline compounds and further enhancing the sterilization effect; alkyl imidazoline or alkenyl imidazoline, halogenated amide and solvent are combined in a mass ratio of 1.6:1:1.9, which can not only achieve precise spatiotemporal coordination of membrane destruction and oxidative attack, but also maximize the synergistic effect of the two, thereby significantly improving the overall sterilization efficiency.

[0018] ② On the metal surface, the polar imidazoline ring of the alkyl imidazoline or alkenyl imidazoline compound is tightly adsorbed on the metal matrix through coordination or electrostatic interaction, while its long-chain alkyl tail forms a dense hydrophobic protective layer towards the solution, effectively isolating moisture and corrosive media; at the same time, the halogenated amide compound is evenly wrapped in the micromicelles formed by the self-assembly of the imidazoline molecules, so that it is directionally released at the metal interface and reacts with the metal to form a stable oxidative passivation film; this passivation film is denser and more durable under the physical barrier of the hydrophobic layer, thereby greatly improving the corrosion inhibition rate; The hydrophilic head of the imidazoline molecule maintains good compatibility with the solvent and water molecules in the aqueous phase, can maintain the stability of the micelle structure, and keep the halogenated amide in a controllable dispersion state. The two synergistically enhance the bactericidal and corrosion inhibition effects; the mass ratio of alkyl imidazoline or alkenyl imidazoline, halogenated amide and solvent of 1.6:1:1.9 ensures that the halogenated amide is sufficiently encapsulated and does not cause premature loss of activity due to excessive membrane rupture; at the same time, under this ratio, the thickness of the hydrophobic layer and the micropore density reach an optimal balance, which can not only stably shield the corrosive medium, but also leave sufficient channels for micelle release. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the preparation process of the composite bactericidal corrosion inhibitor of the present invention; Figure 2 It is a graph of microbial species and abundance in the flowback fluid; Figure 3 The types and contents of organic matter in the flowback fluid; Figure 4 This is a scanning electron microscope image of the surface of a 360 carbon steel test piece eroded by flowback fluid without the addition of the composite bactericidal corrosion inhibitor of Example 1 after 7 days; Figure 5 This is a scanning electron microscope image of the surface of an L360 carbon steel test piece corroded by the flowback fluid containing the composite bactericidal corrosion inhibitor of Example 1 after 7 days. DETAILED DESCRIPTION

[0020] The following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, the experiments were performed under conventional conditions or those recommended by the manufacturer. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0021] Example 1 A composite bactericidal corrosion inhibitor suitable for use in flowback fluids with complex components comprises the following ingredients in the following amounts: 35 wt% polyvinyl imidazoline, 22 wt% 2,2-dibromo-3-nitrilopropionamide, and 43 wt% methanol. The preparation method comprises the following steps: (1) Weighing polyvinyl imidazoline, 2,2-dibromo-3-nitrilopropionamide and methanol respectively, and then dissolving 2,2-dibromo-3-nitrilopropionamide in methanol to prepare a 2,2-dibromo-3-nitrilopropionamide solution; (2) Heat the polyvinyl imidazoline and 2,2-dibromo-3-nitrilopropionamide solutions from step (1) to 40°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 20 mL / min for 40 minutes to ensure that the oxygen content in the system is minimized. (3) The polyvinyl imidazoline and 2,2-dibromo-3-nitrilopropionamide solutions from step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 500 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 40 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced at a flow rate of 20 mL / min for 40 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask from step (3) was placed in a 40°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.45 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0022] Example 2 A composite bactericidal corrosion inhibitor suitable for use in flowback fluids with complex compositions comprises the following ingredients in the following amounts: 40 wt% heptadecenylamine ethyl imidazoline quaternary ammonium salt, 18 wt% 2,2-dibromo-3-cyanopropionamide, 10 wt% thiofluanid, and 32 wt% methanol. The preparation method comprises the following steps: (1) Weighing heptadecenylamine ethyl imidazoline quaternary ammonium salt, 2,2-dibromo-3-cyanopropionamide, thiofluanid and methanol respectively, and then dissolving 2,2-dibromo-3-cyanopropionamide and thiofluanid in methanol respectively to prepare 2,2-dibromo-3-cyanopropionamide solution and thiofluanid solution; (2) Heat the heptadecanylamine ethyl imidazoline quaternary ammonium salt, 2,2-dibromo-3-cyanopropionamide solution, and thiofluanid solution from step (1) to 50°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 20 mL / min for 40 minutes to ensure that the oxygen content in the system is reduced to a minimum. (3) The heptadecanylamine ethyl imidazoline quaternary ammonium salt, 2,2-dibromo-3-cyanopropionamide solution and thiofluanid solution prepared in step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 500 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 40 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at a microscopic scale, thereby ensuring the stability of the formulation system. (4) After the ultrasonic treatment, nitrogen was reintroduced at a flow rate of 20 mL / min for 40 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask from step (3) was placed in a 40°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.45 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0023] Example 3 A composite bactericidal corrosion inhibitor suitable for use in flowback fluids with complex components comprises the following ingredients in the following amounts: 30 wt% N-octadecyl imidazoline, 25 wt% 2,2-dibromomalonamide, and 45 wt% ethanol. The preparation method comprises the following steps: (1) Weigh N-octadecyl imidazoline, 2,2-dibromomalonamide, and ethanol respectively, and then dissolve 2,2-dibromomalonamide in methanol to prepare a 2,2-dibromomalonamide solution; (2) Heat the N-octadecyl imidazoline and 2,2-dibromomalonamide solutions from step (1) to 60°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 30 mL / min for 10 minutes to ensure that the oxygen content in the system is minimized. (3) The polyvinyl imidazoline and 2,2-dibromo-3-nitrilopropionamide solutions from step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 500 rpm using a high shear disperser for 20 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 15 kHz for 30 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced, maintaining a nitrogen flow rate of 20 mL / min, and continued for 30 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask from step (3) was placed in a 60°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.45 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0024] Example 4 A composite bactericidal corrosion inhibitor suitable for flowback fluids with complex components, comprising the following ingredients: 40 wt% polyvinyl imidazoline, 10 wt% 2,2-dibromo-3-cyanopropionamide, 10 wt% dichlorocyanamide, 20 wt% methanol, and 20 wt% octylphenol polyoxyethylene ether-10 (OP-10). The preparation method comprises the following steps: (1) Weighing polyvinyl imidazoline, 2,2-dibromo-3-cyanopropionamide, dichlorocyanamide, methanol and OP-10 respectively, and then dissolving 2,2-dibromo-3-cyanopropionamide and dichlorocyanamide in a mixed solvent of methanol and OP-10 respectively to prepare 2,2-dibromo-3-cyanopropionamide solution and dichlorocyanamide solution; (2) Heat the polyvinyl imidazoline, 2,2-dibromo-3-cyanopropionamide solution, and dichlorocyanobacterium solution from step (1) to 50°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 30 mL / min for 10 minutes to ensure that the oxygen content in the system is reduced to a minimum. (3) The polyvinyl imidazoline, 2,2-dibromo-3-cyanopropionamide solution, and dichlorocyanurate solution from step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 1000 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 30 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced, maintaining a nitrogen flow rate of 20 mL / min, and continued for 30 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask in step (3) was placed in a 50°C water bath and stirred at 200 rpm using a magnetic stirrer for 1 hour; (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.22 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0025] Example 5 A composite bactericidal corrosion inhibitor suitable for use in flowback fluids with complex components, comprising: 47 wt% heptadecenylamine ethyl imidazoline quaternary ammonium salt, 18 wt% 2,2-dibromo-3-nitrilopropionamide, and 35 wt% OP-10. The preparation method comprises the following steps: (1) Heptadecenylamineethylimidazoline quaternary ammonium salt, 2,2-dibromo-3-nitrilopropionamide, and OP-10 were weighed separately, and then 2,2-dibromo-3-nitrilopropionamide was dissolved in methanol to prepare a 2,2-dibromo-3-nitrilopropionamide solution; (2) Heat the heptadecanylamine ethyl imidazoline quaternary ammonium salt and 2,2-dibromo-3-nitrilopropionamide solutions from step (1) to 40°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 30 mL / min for 10 minutes to ensure that the oxygen content in the system is minimized. (3) The heptadecanylamine ethyl imidazoline quaternary ammonium salt and 2,2-dibromo-3-nitrilopropionamide solution of step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 1000 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 20 kHz for 30 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced, maintaining a nitrogen flow rate of 20 mL / min, and continued for 30 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask from step (3) was placed in a 40°C water bath and stirred at 300 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.45 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0026] Example 6 A composite bactericidal corrosion inhibitor suitable for use in flowback fluids with complex components, comprising the following ingredients in the following amounts: 60 wt% N-octadecyl imidazoline, 15 wt% 2,2-dibromo-3-nitrilopropionamide, and 25 wt% nonylphenol polyoxyethylene ether (NP-10). The preparation method comprises the following steps: (1) Weigh N-octadecyl imidazoline, 2,2-dibromo-3-nitrilopropionamide, and NP-10 respectively, and then dissolve 2,2-dibromo-3-nitrilopropionamide in NP-10 to prepare a 2,2-dibromo-3-nitrilopropionamide solution; (2) Heat the N-octadecyl imidazoline and 2,2-dibromo-3-nitrilopropionamide solutions from step (1) to 50°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 30 mL / min for 10 minutes to ensure that the oxygen content in the system is minimized. (3) The N-octadecyl imidazoline and 2,2-dibromo-3-nitrilopropionamide solutions from step (2) were sequentially poured into a three-necked flask from which air had been evacuated, and stirred at 1000 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 30 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced at a flow rate of 20 mL / min for 30 minutes to ensure that there was no residual oxygen in the system. Then, under the protection of nitrogen, the three-necked flask from step (3) was placed in a 50°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.22 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0027] Comparative Example 1 A bactericidal corrosion inhibitor comprising the following ingredients in the following amounts: 43 wt% quinoline quaternary ammonium salt, 43 wt% polyvinyl imidazoline, and 14 wt% methanol. The preparation method is as follows: (1) Weighing quinoline quaternary ammonium salt, polyvinyl imidazoline and methanol respectively, and then dissolving the quinoline quaternary ammonium salt in methanol to prepare a quinoline quaternary ammonium salt solution; (2) Heat the polyvinyl imidazoline and quinoline quaternary ammonium salt solutions from step (1) to 50°C in a thermostatic bath to reduce viscosity and improve subsequent mixing uniformity. Simultaneously, place a 500 mL three-necked flask in a nitrogen atmosphere to exclude air, maintaining a nitrogen flow rate of 30 mL / min for 10 minutes to ensure that the oxygen content in the system is minimized. (3) The polyvinyl imidazoline and quinoline quaternary ammonium salt solutions from step (2) were poured into a three-necked flask from which air had been evacuated, and stirred at 1000 rpm using a high shear disperser for 15 minutes. After stirring, the mixture was immediately placed in an ultrasonic processor for ultrasonic treatment at a frequency of 30 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced, maintaining a nitrogen flow rate of 20 mL / min, and continued for 30 minutes to ensure that there was no residual oxygen in the system. Subsequently, under nitrogen protection, the three-necked flask from step (3) was placed in a 50°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.22 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0028] Comparative Example 2 A bactericidal corrosion inhibitor comprises the following ingredients in the following amounts: 33 wt% imidazoline quaternary ammonium salt, 33 wt% 2,2-dibromo-3-cyanopropionamide, and 34 wt% ethanol. The preparation method is as follows: (1) Weighing imidazoline quaternary ammonium salt, 2,2-dibromo-3-cyanopropionamide and ethanol respectively, and then dissolving the imidazoline quaternary ammonium salt and 2,2-dibromo-3-cyanopropionamide in ethanol respectively to prepare imidazoline quaternary ammonium salt solution and 2,2-dibromo-3-cyanopropionamide solution; (2) Heat the imidazoline quaternary ammonium salt solution and 2,2-dibromo-3-cyanopropionamide solution in step (1) to 50°C in a thermostatic bath to reduce viscosity and improve the uniformity of subsequent mixing. At the same time, place a 500 mL three-necked flask in a nitrogen environment to exclude air, maintain a nitrogen flow rate of 30 mL / min, and continue nitrogen flow for 10 minutes to ensure that the oxygen content in the system is reduced to a minimum; (3) Pour the imidazoline quaternary ammonium salt solution and 2,2-dibromo-3-cyanopropionamide solution from step (2) into a three-necked flask from which air has been evacuated, and stir and mix at 1000 rpm using a high shear disperser for 15 minutes. After stirring, immediately place the mixture in an ultrasonic processor for ultrasonic treatment at a frequency of 30 kHz for 15 minutes. The effect of ultrasound can further promote the uniform dispersion of the components at the microscopic scale, ensuring the stability of the formulation system; (4) After the ultrasonic treatment, nitrogen was reintroduced, maintaining a nitrogen flow rate of 20 mL / min, and continued for 30 minutes to ensure that there was no residual oxygen in the system. Subsequently, under nitrogen protection, the three-necked flask from step (3) was placed in a 50°C water bath and stirred at 400 rpm using a magnetic stirrer for 1 hour. (5) Remove the three-necked flask from step (4) from the water bath and continue to cool naturally to 25°C under nitrogen protection. Keep stirring during the cooling process to prevent the mixture from stratification or sedimentation during the cooling process; (6) The product obtained in step (5) was filtered through a 0.22 μm microporous filter membrane to remove trace solid impurities that may be generated during the reaction and ensure the purity of the final product. After filtration, it was placed in a dry and sterile glass bottle and sealed for storage.

[0029] Test example: The experimental medium is the fracturing flowback fluid of a shale gas hydraulic fracturing in Sichuan, and its main components are shown in Table 1. Figure 2 and 3 : Table 1 Flowback liquid ion concentration (mg / L)

[0030] From Table 1, Figure 2 and 3 It can be seen that the fracturing flowback fluid from a shale gas hydraulic fracturing operation in Sichuan has a complex composition, containing a large number of ions, organic matter, and microorganisms. Therefore, the present invention uses a large amount of field flowback fluid as the experimental medium, which is more representative and realistic than the commonly used simulated water experiments with salts.

[0031] (1) Bactericidal Activity Test of Composite Bactericidal Corrosion Inhibitors: According to GB / T 14643.5-1993, the number of sulfate-reducing bacteria in fracturing flowback fluids containing 80 ppm of composite bactericidal corrosion inhibitors was determined. The experimental results were calculated using the extinction dilution method. The bactericidal test results of different composite bactericidal corrosion inhibitors in Examples 1-6 of the present invention and Comparative Examples 1-2 are shown in Table 2.

[0032] Table 2 Bactericidal rate of sulfate-reducing bacteria after 24 hours of bactericidal corrosion inhibitor action

[0033] Note: Initial bacterial count: 1.0×10 7 pieces / mL.

[0034] As shown in Table 2, the composite bactericidal corrosion inhibitors of Examples 1-6 of the present invention have a sterilization rate of more than 99.99% against sulfate-reducing bacteria after 24 hours of application, demonstrating excellent sterilization effects. This is due to the synergistic effect of the following three ingredients: alkyl imidazolines or alkenyl imidazolines physically destroy the cell membranes of microorganisms, making them more accessible to the oxidizing components of halogenated amide compounds; while halogenated amide compounds, through the strong oxidizing properties of halogens, disrupt the microorganism's cellular metabolic system, destroying the enzyme system and DNA, achieving multi-target sterilization, thereby improving the membrane penetration efficiency of alkyl imidazolines or alkenyl imidazolines and further enhancing the sterilization effect; on the metal surface, alkyl imidazolines or alkenyl imidazolines adsorb on the metal surface through polar groups to form a hydrophobic protective film, which can effectively isolate moisture and corrosive media, and provide a physical barrier to the protective oxide film formed by the passivation reaction of halogenated amides with metals, thereby improving the stability of the oxide film and achieving the effect of improving the corrosion inhibition rate; in addition, the hydrophilicity of imidazolines and the hydrophobicity of halogenated amides optimize the dispersibility of the agent through micellization; at the same time, the solvent can also enhance the solubility and dispersibility of the agent, further improving its application effect in return flow fluid.

[0035] (2) Corrosion inhibition test of bactericidal corrosion inhibitor The corrosion inhibition performance of the composite bactericidal corrosion inhibitors (80 mg / L) of Examples 1-6 and the bactericidal corrosion inhibitors (80 mg / L) of Comparative Examples 1-2 on carbon steel was tested using the weight loss method. The material used was a standard L360 carbon steel test piece with a size of 40 mm × 13 mm × 2 mm, an accuracy of 0.1 mm, a hanging hole of φ4.0 ± 0.1 mm, and a surface area of 12.52 cm. 2 ; Experimental media are Table 1 and Figure 1 、 2 The specimens were completely immersed in the complex flowback fluid from hydraulic fracturing of a shale gas reservoir in Sichuan. The test temperature was 80±2°C and the test period was 7 days. After the test, the specimens were cleaned with a stiff brush and then rinsed with acid, tap water, deionized water, and anhydrous ethanol. The specimens were then dried and allowed to stand at a constant weight for 24 hours. The corrosion rates were then calculated after weighing. The results are shown in Table 3.

[0036] Table 3 Corrosion inhibition effect of composite bactericidal corrosion inhibitors of Examples 1-6 and Comparative Example 1-2 on L360 carbon steel in shale gas hydraulic fracturing field circulating flowback fluid medium

[0037] As shown in Table 3, when the concentration of the composite bactericidal corrosion inhibitor is 80 mg / L, the corrosion inhibition rate can reach a maximum of 84.34%. At this time, the corrosion rate of L360 carbon steel drops to 0.0316 mm / a, which is much lower than the 0.076 mm / a in the industry standard SY / T 0611-2018. The corrosion inhibition rates of the bactericidal corrosion inhibitors in Comparative Examples 1-2 are only 60.35% and 44.93%, and the corrosion rates are 0.0802 mm / a and 0.1114 mm / a, respectively. It can be seen that the corrosion inhibition effect of the composite bactericidal corrosion inhibitor of the present invention is significantly better than that of the bactericidal corrosion inhibitor of Comparative Examples 1-2, which indicates that the addition of the composite bactericidal corrosion inhibitor of the present invention to the shale gas flowback fluid has good corrosion inhibition performance on L360 carbon steel.

[0038] The test results of (1) and (2) show that the composite bactericidal corrosion inhibitor of the present invention can not only effectively kill sulfate-reducing bacteria, but also form a dense protective film on the metal surface, significantly inhibiting the corrosion of pipelines and equipment. Through the combination of ingredients, it exhibits excellent durability and dual protection functions in hydraulic fracturing flowback fluid.

[0039] (3) Appearance test experiment L360 carbon steel specimens treated with a blank solution and the composite bactericidal corrosion inhibitor (80 mg / L) from Example 1 of the present invention were subjected to coupon erosion and other treatments. The surfaces of the L360 carbon steel specimens were then tested according to the scanning electron microscope (SEM) operating instructions and the test requirements of this experiment. A Zeiss Gemini field-emission scanning electron microscope (FESEM) was used for testing at a total magnification of 100×.

[0040] From the SEM test results of the L360 test piece, it can be seen that the surface of the L360 carbon steel test piece in the blank sample solution without the addition of the composite bactericidal corrosion inhibitor of Example 1 has no film layer, and the appearance is dull and rough, with pits and cracks (see Figure 4 ); The surface of L360 carbon steel to which the composite bactericidal corrosion inhibitor of Example 1 was added had a uniform and dense covering film with uniform thickness, and the corrosion products were significantly reduced (see Figure 5 ). It can be seen that the corrosion resistance of the L360 carbon steel specimen treated with the composite bactericidal corrosion inhibitor of Example 1 of the present invention is greatly improved.

[0041] (4) Stability and compatibility test of bactericidal corrosion inhibitors In order to test the stability and compatibility of the composite bactericidal corrosion inhibitor of the present invention, the fracturing fluids added with the composite bactericidal corrosion inhibitors of Examples 1-6 were placed at 20°C, 40°C and 60°C for 24 hours and their states were observed. The observation results are shown in Table 4.

[0042] Table 4 Stability and compatibility of the composite bactericidal corrosion inhibitor of the present invention at 20°C, 40°C and 60°C

[0043] As shown in Table 4, the composite bactericidal and corrosion inhibitor of the present invention is a brown-yellow clear and transparent liquid with a stable state. It does not change color, flocculate or precipitate at 20°C, 40°C and 60°C. It has good compatibility with the fracturing fluid and can maintain its original bactericidal and corrosion inhibition performance after being placed for 24 hours.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite bactericidal corrosion inhibitor suitable for flowback fluid with complex components, characterized in that: The invention comprises the following components: alkyl imidazoline or alkenyl imidazoline, halogenated amide and solvent.

2. The composite bactericidal corrosion inhibitor according to claim 1, characterized in that The mass ratio of the alkyl imidazoline or alkenyl imidazoline, the halogenated amide and the solvent is 1-4:1:1-2.

3. The composite bactericidal corrosion inhibitor according to claim 2, characterized in that The mass ratio of the alkyl imidazoline or alkenyl imidazoline, the halogenated amide and the solvent is 1.6:1:1.

9.

4. The composite bactericidal corrosion inhibitor according to any one of claims 1 to 3, characterized in that The alkenyl imidazoline is polyvinyl imidazoline or heptadecenylaminoethyl imidazoline quaternary ammonium salt; the alkyl imidazoline is N-octadecyl imidazoline.

5. The composite bactericidal corrosion inhibitor according to any one of claims 1 to 3, characterized in that The halogenated amide includes at least one of 2,2-dibromo-3-nitrilopropionamide, 2,2-dibromo-3-cyanopropionamide, 2,2-dibromomalonamide, thiofluanid and diclofenac.

6. The composite bactericidal corrosion inhibitor according to any one of claims 1 to 3, characterized in that The solvent includes at least one of ethanol, OP-10, NP-10, sodium lauryl sulfate, glutaraldehyde, methanol and isopropyl alcohol.

7. The method for preparing the composite bactericidal corrosion inhibitor according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) dissolving the halogenated amide in a solvent to prepare a halogenated amide solution; (2) heating the alkyl imidazoline or alkenyl imidazoline and halogenated amide solutions separately and then subjecting them to nitrogen treatment; (3) The product obtained in step (2) was stirred and mixed, and then ultrasonically treated, and then reacted in a water bath under nitrogen for 1-1.5 hours; (4) Cooling the product obtained in step (3) and filtering it to obtain.

8. The preparation method according to claim 7, characterized in that The heating temperature in step (2) is 30-70° C.; the nitrogen treatment is specifically: nitrogen flow at a nitrogen flow rate of 10-40 mL / min for 5-20 minutes.

9. The preparation method according to claim 7, characterized in that The frequency of the ultrasonic treatment in step (3) is 15-50 kHz, and the time is 15-30 minutes; the nitrogen treatment is specifically: nitrogen flow at a nitrogen flow rate of 20-30 mL / min for 30-40 minutes.

10. The preparation method according to claim 7, characterized in that The filtration in step (4) is specifically: filtering through a 0.22-0.45 μm microporous filter membrane.

Images