A bactericide for umbilical cable filling of deepwater oil and gas fields and a preparation method thereof

Abstract

The application discloses a bactericide for umbilical cable filling of a deepwater oil and gas field and a preparation method thereof. The preparation method comprises the following steps: mixing dicyandiamide and a formaldehyde aqueous solution, and obtaining an intermediate A under the conditions of stirring and negative pressure; adding an aqueous solution of sulfuric acid to obtain an intermediate B; adding dimethyl sulfoxide, controlling the reaction temperature to be 30-40 DEG C, and then adding a quaternary ammonium reagent dropwise to obtain an intermediate C; and mixing 30%-50% of the intermediate C, 1%-3% of D-serine, 10%-20% of a gemini quaternary ammonium salt and 27%-59% of distilled water, and then stirring and filtering to obtain the bactericide product. The bactericide can effectively remove the biofilm generated by microorganisms, convert the biofilm into free bacteria, and meet the requirements of medicament cleanliness and compatibility in the process of umbilical cable filling of the deepwater oil and gas field, has the characteristics of small medicament dosage, good bactericidal effect, no negative influence on oil-water separation, stable product, good compatibility and the like.

Description

Technical Field

[0001] This invention relates to the field of oilfield water treatment technology, and in particular to a bactericide for injecting umbilical cables in deepwater oil and gas fields and its preparation method. Background Technology

[0002] Microbial corrosion has always been a problem in oil and gas field production. Especially with the development of secondary and tertiary oil recovery technologies, most oilfields have entered a high water-cut development phase. The continuous increase in water injection and production, the rising water content of produced fluids, and the application of polymer flooding have created favorable conditions for bacterial growth in oilfield systems, making bacterial corrosion an increasingly serious problem. The growth, metabolism, and reproduction of microorganisms in oilfield systems can cause corrosion and damage to drilling and production equipment, water injection pipelines, and other metal materials; blockage of pipelines and water injection wells; decreased permeability of oil reservoir pores, hindering water injection for oil recovery; and even degradation of other oilfield chemicals and reduction of their efficiency. All these hazards result in significant economic losses for industrial and oilfield production operations.

[0003] Deepwater oil and gas field disinfectants need to be injected via umbilical cables. The injection of agents via umbilical cables involves not only the compatibility of the umbilical cables, but also the compatibility of the sealing materials of the subsea production system. The agents come into direct contact with many materials, and the injection environment has large temperature variations and high pressure, which places high demands on the stability of the agents. At the same time, the cleanliness of the agents must meet the NASA 1638 standard of level 8.

[0004] The main types of bactericides used in offshore oilfields include quaternary ammonium salts, quaternary phosphonium salts, glutaraldehyde, organic guanidines, and heterocyclic compounds. However, in recent years, considering that low-pH agents may corrode production equipment, offshore oilfields require that the pH value of supplied agents must be greater than 6. Quaternary phosphonium salt bactericides typically have a pH of around 3, which does not meet current oilfield corrosion control requirements. Although quaternary ammonium salt bactericides have bactericidal effects, they are highly foaming and have high viscosity at low temperatures, which can easily cause blockages or increased injection pressure during injection. Glutaraldehyde bactericides have good bactericidal effects, but they are highly toxic, have a strong odor, a short shelf life, and do not meet the compatibility requirements for umbilical cable materials in deepwater oil and gas fields. Organic guanidine bactericides are prone to developing resistance. Heterocyclic compound bactericides are highly toxic, have a strong odor, poor low-temperature stability, and poor compatibility with umbilical cable materials. Currently, the bactericides injected into deepwater oil and gas fields via umbilical cables are mostly tetramethylolphosphine sulfate. This agent has a low pH value, strong self-corrosiveness, and high phosphorus content, which does not conform to CNOOC's concept of low-carbon and environmentally friendly products. Moreover, the product is limited and there are no bactericide products that can be injected alternately.

[0005] Based on the above, it is necessary to develop a bactericide specifically for deep-water oil and gas fields that has good bactericidal effects against sulfate-reducing bacteria, saprophytic bacteria, and iron bacteria, good compatibility with oil-water systems in oil fields, no negative impact on oil-water separation, and meets the requirements for compatibility and low-temperature stability of umbilical cable materials in deep-water oil and gas fields. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a bactericide for injecting umbilical cables in deepwater oil and gas fields and its preparation method.

[0007] In a first aspect, the present invention provides a method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields, which is achieved by the following technical solution.

[0008] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Mix dicyandiamide and formaldehyde aqueous solution in a molar ratio of 1:1-1:3 and react under stirring and negative pressure to obtain intermediate A; S2. Under stirring and negative pressure conditions, an aqueous solution of sulfuric acid with a molar ratio of 0.05:1 to 0.2:1 to dicyandiamide is added dropwise to the product obtained in step S1 to obtain intermediate B. S3. Under stirring and negative pressure conditions, dimethyl sulfoxide is added to the product obtained in step S2, the reaction temperature is controlled at 30-40℃, and then a quaternizing agent with a molar ratio of 0.2:1-0.8:1 to dicyandiamide is added dropwise. After the reaction, intermediate C is obtained. S4. Mix 30%-50% of intermediate C, 1%-3% of D-serine, 10%-20% of geminal quaternary ammonium salt, and 27%-59% of distilled water by mass, stir for 0.5-1 h, and filter to obtain the bactericide product.

[0009] Furthermore, in step S1, the concentration of the formaldehyde aqueous solution is 37 wt%.

[0010] Furthermore, in step S1, the reaction temperature is 60-90℃ and the reaction time is 0.5-2 hours.

[0011] Furthermore, in step S2, the concentration of the sulfuric acid aqueous solution is 30 wt%.

[0012] Furthermore, in step S2, the reaction temperature is 50-70℃ and the reaction time is 0.5-2 hours.

[0013] Furthermore, in step S3, the mass ratio of dimethyl sulfoxide to intermediate C is 1:1 to 3:1.

[0014] Furthermore, in step S3, the quaternizing agent is selected from epichlorohydrin and benzyl chloride.

[0015] Furthermore, in step S3, the quaternizing reagent is added dropwise over 0.5-1.5 hours, and after the addition is complete, the temperature is raised to 70-90℃, and the reaction is allowed to proceed for 1.5-2.5 hours.

[0016] Furthermore, in steps S1, S2, and S3, the negative pressure is -0.01 MPa to -0.03 MPa.

[0017] Furthermore, in step S4, the gemini quaternary ammonium salt is selected from one of tetradecyl dimethyl gemini quaternary ammonium salt (40%), dodecyl dimethyl gemini quaternary ammonium salt (40%), bis(tetradecyl dimethyl) benzyl ammonium chloride (40%), and bis(dodecyl dimethyl) benzyl ammonium chloride (40%).

[0018] Secondly, the present invention provides a bactericide for injecting umbilical cables in deepwater oil and gas fields, which is achieved by the following technical solution.

[0019] A bactericide for injecting umbilical cables in deepwater oil and gas fields, prepared by the above method.

[0020] This application has the following beneficial effects: Compared with conventional bactericides, this invention can effectively improve the bactericidal effect, remove the biofilm produced by microorganisms and transform them into free bacteria. It can also meet the requirements of agent cleanliness and compatibility in the deep-water oil and gas field umbilical cable injection process. It has the characteristics of small dosage, strong bactericidal effect on sulfate-reducing bacteria, saprophytic bacteria and iron bacteria, no negative impact on oil-water separation, product stability, good compatibility and wide applicability. Detailed Implementation

[0021] The present patent application will be further described below with reference to the embodiments.

[0022] Example 1

[0023] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 81.16g of 37% aqueous formaldehyde solution (containing 1mol of formaldehyde) to the reaction vessel, start the stirrer and turn on the vacuum pump to maintain a negative pressure of 0.01MPa in the vessel, and heat to 60℃ for 0.5 hours to obtain intermediate A; S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 16.35g of 30% sulfuric acid aqueous solution (containing 0.05mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 50℃ and react for 0.5 hours to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 200.10g of dimethyl sulfoxide, control the reaction temperature at 30℃, and then add 18.51g of epichlorohydrin (0.2mol) dropwise. After adding the solution for 0.5 hours, slowly raise the temperature to 70℃ and react for 1.5 hours to obtain intermediate C. S4. Add 50% by mass of intermediate C, 3% D-serine, 20% tetradecyl dimethyl gemini quaternary ammonium salt (40%), and 27% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 0.5 hours. Filter the mixture to obtain the bactericide product.

[0024] Example 2

[0025] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 81.16g of 37% aqueous formaldehyde solution (containing 1mol of formaldehyde) to the reaction vessel, start the stirrer and turn on the vacuum pump to maintain a negative pressure of 0.02MPa in the vessel, and heat to 60℃ for 0.5 hours to obtain intermediate A; S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 16.35g of 30% sulfuric acid aqueous solution (containing 0.05mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 50℃ and react for 0.5 hours to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 206.91g of dimethyl sulfoxide, control the reaction temperature at 30℃, and then add 25.32g of benzyl chloride (0.2mol) dropwise. After adding the benzyl chloride dropwise for 0.5 hours, slowly raise the temperature to 70℃ and react for 2 hours to obtain intermediate C. S4. Add 50% by mass of intermediate C, 3% D-serine, 20% dodecyl dimethyl gemini quaternary ammonium salt (40%), and 27% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 1 hour. Filter the mixture to obtain the bactericide product.

[0026] Example 3

[0027] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 162.32g of 37% aqueous formaldehyde solution (containing 2mol of formaldehyde) to the reaction vessel. Turn on the stirrer and the vacuum pump to maintain a negative pressure of 0.03MPa in the vessel. Heat the mixture to 75℃ and react for 1 hour to obtain intermediate A. S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 32.7g of 30% sulfuric acid aqueous solution (containing 0.1mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 60℃ and react for 1 hour to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 325.37g of dimethyl sulfoxide, control the reaction temperature at 35℃, and then add 46.27g of epichlorohydrin (0.5mol) dropwise. After adding the solution for 1 hour, slowly raise the temperature to 80℃ and react for 2.5 hours to obtain intermediate C. S4. Add 40% by mass of intermediate C, 2% D-serine, 15% ditetradecyl dimethyl benzyl ammonium chloride (40%), and 43% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 0.75 hours. Filter the mixture to obtain the bactericide product.

[0028] Example 4

[0029] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 162.32g of 37% aqueous formaldehyde solution (containing 2mol of formaldehyde) to the reaction vessel, start the stirrer and turn on the vacuum pump to maintain a negative pressure of 0.01MPa in the vessel, and heat to 75℃ for 1 hour to obtain intermediate A. S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 32.7g of 30% sulfuric acid aqueous solution (containing 0.1mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 60℃ and react for 1 hour to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 342.39g of dimethyl sulfoxide, control the reaction temperature at 35℃, and then add 46.27g of benzyl chloride (0.5mol) dropwise. After adding for 1 hour, slowly raise the temperature to 80℃ and react for 1.5 hours to obtain intermediate C. S4. Add 40% by mass of intermediate C, 2% D-serine, 15% didodecyl dimethyl benzyl ammonium chloride (40%), and 43% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 0.5 hours. Filter the mixture to obtain the bactericide product.

[0030] Example 5

[0031] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 243.49g of 37% aqueous formaldehyde solution (containing 3mol of formaldehyde) to the reaction vessel, start the stirrer and turn on the vacuum pump to maintain a negative pressure of 0.02MPa in the vessel, and heat to 90℃ for 2 hours to obtain intermediate A; S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 65.39g of 30% sulfuric acid aqueous solution (containing 0.2mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 70℃ and react for 2 hours to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 466.98g of dimethyl sulfoxide, control the reaction temperature at 40℃, and then add 74.02g of epichlorohydrin (0.8mol) dropwise. After 1.5 hours of dropwise addition, slowly raise the temperature to 90℃ and react for 2 hours to obtain intermediate C. S4. Add 30% by mass of intermediate C, 1% D-serine, 10% tetradecyl dimethyl gemini quaternary ammonium salt (40%), and 59% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 1 hour. Filter the mixture to obtain the bactericide product.

[0032] Example 6

[0033] A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields includes the following steps: S1. Add 84.08g of dicyandiamide (1mol) and 243.49g of 37% aqueous formaldehyde solution (containing 3mol of formaldehyde) to the reaction vessel. Turn on the stirrer and the vacuum pump to maintain a negative pressure of 0.03MPa in the vessel. Heat the mixture to 90℃ and react for 2 hours to obtain intermediate A. S2. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 65.39g of 30% sulfuric acid aqueous solution (containing 0.2mol of sulfuric acid) dropwise to the product obtained in S1. Heat the mixture to 70℃ and react for 2 hours to obtain intermediate B. S3. Start the stirrer and turn on the vacuum pump to maintain negative pressure in the container. Add 494.22g of dimethyl sulfoxide, control the reaction temperature at 40℃, and then add 101.26g of benzyl chloride (0.8mol) dropwise. After adding for 1.5 hours, slowly raise the temperature to 90℃ and react for 2.5 hours to obtain intermediate C. S4. Add 30% by mass of intermediate C, 1% D-serine, 10% dodecyl dimethyl gemini quaternary ammonium salt (40%), and 59% distilled water to a reaction vessel at room temperature and pressure. Start stirring and stir for 0.5 hours. Filter the mixture to obtain the bactericide product.

[0034] Performance testing I. Viscosity-Temperature Change Test Evaluation method: (1) The test reference is SY / T 0520-2008 "Determination of Crude Oil Viscosity - Rotational Viscometer Equilibrium Method"; (2) Anton Paar MCR 302e rheometer was used to reduce the temperature to the measurement temperature at a rate of 0.5℃ / min, accurate to ±0.1℃, and the shear rate was set to 10s.-1 .

[0035] (3) Evaluation criteria: viscosity ≤ 80 mPa·s (5℃) The test results are shown in Table 1: Table 1. Results of viscosity-temperature change test As shown in Table 1, based on the conditions for adding chemicals to the umbilical cable, at a test temperature of 5°C, the viscosities of Examples 1, 2, 3, 4, 5, and 6, THPS (75%), polyhexamethylene guanidine hydrochloride (30%), glutaraldehyde (25%), D-serine (5%), and commercially available bactericide 1 (30%) meet the requirements (dynamic viscosity ≤ 80 mPa·s). At 5°C, the dynamic viscosity of simple quaternary ammonium salt bactericides is greater than 80 mPa·s, which cannot meet the requirements for adding bactericides to the umbilical cable.

[0036] II. Cleanliness Change Test Evaluation method: The bactericide was placed in an environment of -10℃ and 10 MPa for a certain period of time, and samples were taken for testing using a liquid particle tester. Its cleanliness was determined according to the NASA 1638 (NAS8) oil cleanliness standard, and the cleanliness level was required to be ≤NAS8.

[0037] The test results are shown in Table 2: Table 2. Test results of cleanliness changes at 25℃ and 0.1MPa As shown in Table 2, within the test time range, glutaraldehyde, tetradecyl dimethyl gemini quaternary ammonium salt (40%), dodecyl dimethyl gemini quaternary ammonium salt (40%), bis(tetradecyl dimethyl benzyl ammonium chloride) (40%), bis(dodecyl dimethyl benzyl ammonium chloride) (40%), commercially available bactericide 1 (30%), and commercially available bactericide 2 (40%) all exceeded the NASA 8 standard, indicating that the cleanliness level deteriorated over time and did not meet the requirements for umbilical cable refilling. However, in Examples 1, 2, 3, 4, 5, and 6, the cleanliness changes of tetramethyl phosphate sulfate (75%), polyhexamethylene guanidine hydrochloride (30%), dodecyl dimethyl benzyl ammonium chloride (44%), and D-serine (5%) were all normal and met the requirements for umbilical cable refilling.

[0038] III. Compatibility Testing (Non-metal quality change + Metal corrosion rate): Experimental materials: reagent stock solution, polytetrafluoroethylene, butyl rubber, stainless steel, bronze Evaluation method: Test various performance changes after soaking in the reagent for 32 days. Evaluation criteria: The weight change of polytetrafluoroethylene (PTFE) and butyl rubber over 32 days shall meet the requirement of ±10%; the volume change of PTFE and butyl rubber over 32 days shall meet the requirement of -5% to 25%; the self-corrosion rate of stainless steel and bronze shall be ≤0.01mm / a.

[0039] The results of the non-metallic mass change test are shown in Table 3, the results of the non-metallic volume change test are shown in Table 4, and the results of the metallic corrosion rate test are shown in Table 5.

[0040] Table 3 Results of Non-metallic Weight Change Test Table 4. Test results of non-metallic volume change Note: "-" indicates a reduction in volume. Table 5 Results of metal corrosion rate test As can be seen from the test data in Tables 3-5, the compatibility tests of Examples 1, 2, 3, 4, 5, and 6 of this invention, as well as D-serine, polyhexamethylene guanidine hydrochloride (30%), dodecyl dimethyl benzyl ammonium chloride (44%), tetradecyl dimethyl gemini quaternary ammonium salt (40%), dodecyl dimethyl gemini quaternary ammonium salt (40%), bis(tetradecyl dimethyl benzyl ammonium chloride) (40%), and bis(dodecyl dimethyl benzyl ammonium chloride) (40%), all meet the requirements.

[0041] IV. Low-Temperature Sterilization Performance Test Experimental materials: water from a deep-water oil and gas field in the South China Sea Evaluation method: The performance evaluation of the bactericide was based on SY / T 5329-2022 "Water Quality Indicators and Analysis Methods for Injection Water in Clastic Oil Reservoirs". Experimental temperature: 38 ℃, dosage concentration: 100 mg / L. Test results are shown in Table 6. Table 6. Sterilization Efficacy Test As can be seen from the data in Table 6, the three types of bacteria in Examples 1, 2, 3, 4, 5, and 6 of this invention, at an experimental temperature of 38 ℃ and a dosage concentration of 200 mg / L, can be completely killed.

[0042] V. Medium-temperature sterilization performance test Experimental materials: water from a deep-water oil and gas field in the South China Sea Evaluation method: The performance evaluation of the bactericide was based on SY / T 5329-2022 "Water Quality Indicators and Analysis Methods for Injection Water in Clastic Rock Reservoirs". Experimental temperature: 60 ℃, dosage concentration: 150 mg / L. Test results are shown in Table 7. Table 7. Sterilization Efficacy Test As can be seen from the data in Table 7, the three types of bacteria in Examples 1, 2, 3, 4, 5, and 6 of the present invention can be completely killed at an experimental temperature of 60 ℃ and a drug concentration of 150 mg / L.

[0043] VI. High-Temperature Sterilization Performance Test Experimental materials: water from a deep-water oil and gas field in the South China Sea Evaluation method: The performance evaluation of the bactericide was based on SY / T 5329-2022 "Water Quality Indicators and Analysis Methods for Injection Water in Clastic Rock Reservoirs". Experimental temperature: 80 ℃, dosage concentration: 200 mg / L. Test results are shown in Table 8. Table 8. Sterilization Efficacy Test As can be seen from the data in Table 8, the three types of bacteria in Examples 1, 2, 3, 4, 5, and 6 of the present invention can be completely killed at an experimental temperature of 80 ℃ and a drug concentration of 200 mg / L.

[0044] VII. Test on the impact of oil-water separation Experimental materials: Produced wastewater from an offshore oil field (a mixture of oil, gas, and water phases). Evaluation methods: SY / T 5280-2018 "General Technical Conditions for Crude Oil Demulsifiers" and SY / T 5797-93 "Performance Evaluation Method for Water-in-Oil Emulsion Demulsifiers" Experimental temperature: 65℃; Demulsifier used: YFPZ-1216 Sterilization concentration: 200 mg / L (administered via shock dosing over 8 hours) The test results are as follows: Table 9. Effect of bactericides on oil-water separation efficiency Oil sample volume: 80 ml; water content: 70%; experimental temperature: 65℃; hand-cranked vibration: 200 times. In summary, Embodiments 1, 2, 3, 4, 5, and 6 of this invention have a more efficient bactericidal effect in the protection against microbial corrosion in deepwater oil and gas fields, while meeting the requirements for viscosity-temperature change testing, cleanliness testing, compatibility testing (non-metallic quality change + metallic corrosion rate), and low-temperature, medium-temperature, and high-temperature bactericidal performance testing of umbilical cables in deepwater oil and gas fields.

[0045] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a bactericide for injecting umbilical cables in deepwater oil and gas fields, characterized in that: Includes the following steps: S1. Mix dicyandiamide and formaldehyde aqueous solution in a molar ratio of 1:1-1:3 and react under stirring and negative pressure to obtain intermediate A; S2. Under stirring and negative pressure conditions, an aqueous solution of sulfuric acid with a molar ratio of 0.05:1 to 0.2:1 to dicyandiamide is added dropwise to the product obtained in step S1 to obtain intermediate B. S3. Under stirring and negative pressure conditions, dimethyl sulfoxide is added to the product obtained in step S2, the reaction temperature is controlled at 30-40℃, and then a quaternizing agent with a molar ratio of 0.2:1-0.8:1 to dicyandiamide is added dropwise. After the reaction, intermediate C is obtained. S4. Mix 30%-50% of intermediate C, 1%-3% of D-serine, 10%-20% of geminal quaternary ammonium salt, and 27%-59% of distilled water by mass, stir for 0.5-1 h, and filter to obtain the bactericide product.

2. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S1, the reaction temperature is 60-90℃ and the reaction time is 0.5-2 hours.

3. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S2, the reaction temperature is 50-70℃ and the reaction time is 0.5-2 hours.

4. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S3, the mass ratio of dimethyl sulfoxide to intermediate C is 1:1 to 3:

1.

5. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S3, the quaternizing agent is selected from epichlorohydrin and benzyl chloride.

6. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S3, the quaternizing reagent is added dropwise over 0.5-1.5 hours. After the addition is complete, the temperature is raised to 70-90℃ and the reaction is allowed to proceed for 1.5-2.5 hours.

7. The method for preparing a bactericide for deepwater oil and gas field umbilical cable injection according to claim 1, characterized in that: In step S4, the gemini quaternary ammonium salt is selected from one of tetradecyl dimethyl gemini quaternary ammonium salt, dodecyl dimethyl gemini quaternary ammonium salt, ditetradecyl dimethyl benzyl ammonium chloride, and didodecyl dimethyl benzyl ammonium chloride.

8. A bactericide for injecting umbilical cables in deepwater oil and gas fields, prepared by any one of the preparation methods described in claims 1-7.

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