A betaine-type zwitterionic polymer oil displacement agent and its synthesis method

Abstract

This invention relates to a betaine-type zwitterionic polymer flooding agent and its synthesis method, belonging to the field of reservoir development technology. This invention grafts hydrophobic groups and betaine groups onto the same monomer. The water-soluble sulfonic acid groups in the betaine groups have strong hydration properties, which can increase the water solubility of the hydrophobic groups. Simultaneously, ether bonds are introduced into the polymer, further improving its water solubility. This invention also utilizes the dynamic acylhydrazone bonds formed by the reaction of nano-silica particles containing ketone groups on their surface and the acylhydrazine groups on the polymer side chains to connect the polymer molecular chains, forming a three-dimensional network structure. Combined with the physical crosslinking formed by hydrophobic association and the nano-silica particles, this significantly improves the temperature resistance, salt resistance, and shear resistance of the polymer flooding agent.

Description

Technical Field

[0001] This invention belongs to the field of oil reservoir development technology, specifically relating to a betaine-type zwitterionic polymer oil displacement agent and its synthesis method. Background Technology

[0002] With socio-economic development, people's dependence on petroleum and related products is increasing. However, as proven oil reserves continue to decrease and oilfield development gradually shifts towards tight reservoirs with higher temperatures, higher salinity, higher water content, and lower permeability, petroleum, as a non-renewable resource, becomes increasingly precious. Therefore, there is an urgent need for more effective development of oilfields to increase oil production to meet the ever-growing demands of industrial production. Polymer flooding is a production enhancement measure that involves injecting polymers into the formation to displace oil. Traditionally, polyacrylamide is used both domestically and internationally. It has advantages such as good water solubility, high fluidity, and low cost. However, in the high-temperature, high-salinity deep-well environment, it weakens the electrostatic repulsion between carboxylic acid groups, leading to a significant decrease in the apparent viscosity of the system. Simultaneously, polyacrylamide is highly sensitive to salt, resulting in poor thermal stability and shear resistance, thus significantly reducing the recovery rate of crude oil in this area.

[0003] For deep well environments characterized by high temperature and high salinity, a common method is to modify acrylamide copolymers to enhance their ability to withstand harsh conditions. Hydrophobic associating polymers are one such modified product. By introducing hydrophobic groups, strong intermolecular forces are generated, enabling the polymer flooding agent to form intermolecular associations and construct a polymer network structure with a certain strength, thus achieving a thickening effect. However, hydrophobic associating polymers suffer from slow dissolution rates, significantly limiting their thickening effect. Therefore, it is necessary to address these issues and provide a polymer flooding agent that combines salt resistance, temperature resistance, shear resistance, and high solubility. Summary of the Invention

[0004] The purpose of this invention is to provide a betaine-type zwitterionic polymer oil displacement agent and its synthesis method. Hydrophobic groups and betaine groups are grafted onto the same monomer. The water-soluble sulfonic acid groups in the betaine groups have strong hydration properties, which can increase the water solubility of the hydrophobic groups. Simultaneously, ether bonds are introduced into the polymer, further improving its water solubility. This invention utilizes the dynamic acylhydrazone bonds formed by the reaction of nano-silica particles containing ketone groups on their surface and the acylhydrazine groups on the polymer side chains to connect the polymer molecular chains, forming a three-dimensional network structure. Combined with the physical crosslinking formed by hydrophobic association and the nano-silica particles, this significantly improves the temperature and salt resistance, shear resistance, and solubility of the polymer oil displacement agent.

[0005] The technical problem this invention aims to solve is that, in high-temperature, high-salt deep-well environments, traditionally used polyacrylamide weakens the electrostatic repulsion between carboxylic acid groups, leading to a significant decrease in the apparent viscosity of the system. Simultaneously, polyacrylamide is highly sensitive to salt, resulting in poor thermal stability and shear resistance, thus greatly reducing the recovery rate of crude oil in these areas. Hydrophobic associating polymers introduce hydrophobic groups to generate strong intermolecular forces, enabling the polymer flooding agent to form intermolecular associations and construct a polymer network structure with a certain strength, achieving a thickening effect. However, hydrophobic associating polymers suffer from slow dissolution rates, greatly limiting their thickening effect.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for synthesizing a betaine-type zwitterionic polymer oil displacement agent includes the following steps:

[0008] S1. Allyl polyoxyethylene ether is dissolved in an organic solvent, and manganese dioxide is added to carry out an oxidation reaction to obtain an unsaturated monomer containing aldehyde groups and ether bonds; the unsaturated monomer containing aldehyde groups and ether bonds and an organic small molecule containing hydrazide groups are dissolved in deionized water, acetic acid is added, and the reaction is carried out at 50-70℃ for 24-36 h to obtain an unsaturated monomer containing hydrazide groups and ether bonds.

[0009] In the above preparation process, the hydroxyl groups in allyl polyoxyethylene ether are oxidized to aldehyde groups to obtain an unsaturated monomer containing aldehyde groups and ether bonds. Then, it reacts with an organic small molecule containing two acyl hydrazine groups to obtain an unsaturated monomer containing acyl hydrazine groups and ether bonds.

[0010] Furthermore, in step S1, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:1.5-2.

[0011] Furthermore, in step S1, the molecular weight of the allyl polyoxyethylene ether is 102-938.

[0012] Furthermore, in step S1, the oxidation reaction is carried out at a temperature of 25-30°C.

[0013] Further, in step S1, the small organic molecule containing an acylhydrazine group includes at least one of 3,3'-dithiodipropionylhydrazine, 2,2'-dithiodiacetylhydrazine, 4,4'-dithiodibutyrylhydrazine, adipic acid dihydrazine, and malonate dihydrazine.

[0014] Furthermore, in step S1, the molar ratio of unsaturated monomers containing aldehyde groups and ether bonds to small organic molecules containing hydrazide groups is 1:(1.05-1.2).

[0015] S2. Dissolve acrylamide and acrylic acid in deionized water, adjust the pH of the system to 6-8, add unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups, stir until the solution is clear, introduce nitrogen gas, add initiator to carry out reaction, after the reaction is completed, dehydrate and precipitate in anhydrous ethanol, dry and pulverize to obtain polymer.

[0016] Further, in step S2, the molar ratio of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds, and betaine-type functional monomers containing hydrophobic groups is (70-80):(4-8):(7-10):(1.3-1.8).

[0017] Further, in step S2, the initiator is at least one selected from dimethyl azobisisobutyrate, azobisisopropylimidazoline hydrochloride, azodicarbonamide, and azobisisobutyramidine hydrochloride; the amount of initiator added is 0.2-0.5% of the total mass of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds, and betaine-type functional monomers containing hydrophobic groups.

[0018] Furthermore, in step S2, the reaction temperature is 40-60℃ and the reaction time is 3-8h.

[0019] S3. Add nano-silica particles with ketone groups on their surface to deionized water and disperse them evenly to obtain a nano-silica particle dispersion with ketone groups on their surface. Add the polymer to deionized water and stir evenly. Then add the nano-silica particle dispersion with ketone groups on its surface and stir evenly. Add acetic acid and adjust the pH to 5-5.5. React for 36-58 hours to obtain a betaine-type zwitterionic polymer oil displacement agent.

[0020] In the above preparation process, the acylhydrazine groups in the polymer react with the ketone groups on the surface of the nano-silica particles to form dynamic acylhydrazone bonds, thereby forming a polymer network structure.

[0021] Furthermore, in step S3, the mass concentration of the dispersion of nano-silica particles containing ketone groups on the surface is 2-5%.

[0022] Furthermore, in step S3, the molar ratio of nano-silica particles containing ketone groups on the surface to the polymer is (1-1.5):1.

[0023] Furthermore, the preparation method of betaine-type functional monomers containing hydrophobic groups includes the following steps:

[0024] A1. Sodium N-methyltaurate and 4-chloro-1-butene undergo a nucleophilic substitution reaction at 40-55℃ for 1-2 hours to obtain an intermediate;

[0025] Further, in step A1, the molar ratio of sodium N-methyltaurate and 4-chloro-1-butene is 1:(1.05-1.15).

[0026] A2. The intermediate and myristoyl chloride were subjected to a quaternization reaction at 5-10℃ for 3 hours to obtain a betaine-type functional monomer containing a hydrophobic group.

[0027] Furthermore, in step A2, the molar ratio of the intermediate to myristoyl chloride is 1:(1.1-1.3).

[0028] In the above preparation process, hydrophobic groups and betaine groups are grafted onto the same monomer. The water-soluble sulfonic acid group in the betaine group has strong hydration properties, which can increase the water solubility of the hydrophobic group.

[0029] Furthermore, the method for preparing nano-silica particles with ketone groups on their surface includes the following steps:

[0030] B1. Mix nano-silica particles, aminosilane coupling agent, and anhydrous ethanol evenly, react at 90-100℃ for 24-36h, centrifuge, wash, and dry to obtain amino-modified nano-silica particles.

[0031] Further, in step B1, the ratio of nano-silica particles to aminosilane coupling agent and anhydrous ethanol is (2.2-2.5) g : (3.9-4.8) mL : (100-130) mL.

[0032] B2. Disperse amino-modified nano-silica particles in deionized water to obtain a dispersion; dissolve pyruvic acid and catalyst in deionized water, add the dispersion and react for 18-32 hours. After the reaction is completed, centrifuge, wash and dry to obtain nano-silica particles with ketone groups on the surface.

[0033] Further, in step B2, the catalyst is a mixture of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of (1-2):(0.5-1.5).

[0034] Furthermore, in step B2, the ratio of amino-modified nano-silica particles, pyruvic acid, and catalyst is (1.5-1.7) g : (2.1-2.4) mL : (0.21-0.28) g.

[0035] In the preparation process of the above-mentioned nano-silica particles with ketone groups on the surface, the nano-silica particles are first modified by an aminosilane coupling agent, and then the amino group is reacted with pyruvic acid to obtain nano-silica particles with ketone groups on the surface.

[0036] The present invention also provides a betaine-type zwitterionic polymer oil displacement agent prepared by the above preparation method.

[0037] The beneficial effects of this invention are:

[0038] (1) In the technical solution of the present invention, hydrophobic groups and betaine groups are grafted onto the same monomer. The water-soluble sulfonic acid group in the betaine group has strong hydration properties, which can increase the water solubility of the hydrophobic group. At the same time, ether bonds are introduced into the side chain of the polymer, which further improves the water solubility of the polymer.

[0039] (2) In the technical solution of the present invention, the nano silica particles containing ketone groups on the surface react with the hydrazide groups of the polymer side chain to form dynamic hydrazone bonds. The polymer molecular chains are connected by hydrazone bonds to form a three-dimensional network structure. The presence of dynamic hydrazone bonds can restore the broken chain segments of the polymer oil displacement agent under shearing action, thereby improving the viscosity, shear resistance and temperature resistance of the polymer oil displacement agent. At the same time, the introduction of nano silica particles further improves the temperature resistance and shear resistance of the polymer oil displacement agent.

[0040] (3) In the technical solution of the present invention, the viscosity of the oil displacement agent is improved by the physical cross-linking network formed by the hydrophobic interaction between the hydrophobic segments of the polymer oil displacement agent, the three-dimensional network structure formed by the polymer molecular chains connected by acylhydrazone bonds, and the synergistic effect of nano silica particles and betaine groups, thereby enhancing the oil displacement agent's temperature resistance, salt resistance and shear resistance. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] This embodiment provides a method for preparing a betaine-type functional monomer containing a hydrophobic group, comprising the following steps:

[0044] A1. Sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.1 were added to methanol and stirred until homogeneous. The mixture was then reacted at 40°C for 1 hour to obtain an intermediate.

[0045] A2. The intermediate and myristoyl chloride were mixed in a molar ratio of 1:1.1 and reacted at 5°C for 3 hours to obtain a betaine-type functional monomer containing a hydrophobic group.

[0046] Example 2

[0047] This embodiment provides a method for preparing a betaine-type functional monomer containing a hydrophobic group, comprising the following steps:

[0048] A1. Sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.2 were added to methanol and stirred until homogeneous. The mixture was then reacted at 45°C for 1.5 h to obtain an intermediate.

[0049] A2. The intermediate and myristoyl chloride were mixed in a molar ratio of 1:1.2 and reacted at 5°C for 3 h to obtain a betaine-type functional monomer containing a hydrophobic group.

[0050] Example 3

[0051] This embodiment provides a method for preparing a betaine-type functional monomer containing a hydrophobic group, comprising the following steps:

[0052] A1. Sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.3 were added to methanol and stirred until homogeneous. The mixture was then reacted at 55°C for 2 hours to obtain an intermediate.

[0053] A2. The intermediate and myristoyl chloride were mixed in a molar ratio of 1:1.3 and reacted at 10°C for 3 h to obtain a betaine-type functional monomer containing a hydrophobic group.

[0054] Example 4

[0055] This embodiment provides a method for preparing nano-silica particles with ketone groups on their surface, comprising the following steps:

[0056] B1. Mix 22g of nano silica particles with 39mL of aminosilane coupling agent KH-550 and 1L of anhydrous ethanol evenly, react at 90℃ for 24h, centrifuge, wash and dry to obtain amino-modified nano silica particles.

[0057] B2. 15g of amino-modified nano silica particles were dispersed in 150mL of deionized water to obtain a dispersion. 21mL of pyruvic acid, 1.4g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 0.7g of N-hydroxysuccinimide were dissolved in 1L of deionized water, and the dispersion was added to react for 18h. After the reaction was completed, the particles were centrifuged, washed and dried to obtain nano silica particles with ketone groups on their surface.

[0058] Example 5

[0059] This embodiment provides a method for preparing nano-silica particles with ketone groups on their surface, including the following steps:

[0060] B1. Mix 23g of nano silica particles with 45mL of aminosilane coupling agent KH-550 and 1.2L of anhydrous ethanol evenly, react at 90℃ for 36h, centrifuge, wash and dry to obtain amino-modified nano silica particles.

[0061] B2. 16g of amino-modified nano silica particles were dispersed in 180mL of deionized water to obtain a dispersion. 22mL of pyruvic acid, 1.4g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.1g of N-hydroxysuccinimide were dissolved in 1L of deionized water, and the dispersion was added to react for 24h. After the reaction was completed, the particles were centrifuged, washed and dried to obtain nano silica particles with ketone groups on their surface.

[0062] Example 6

[0063] This embodiment provides a method for preparing nano-silica particles with ketone groups on their surface, including the following steps:

[0064] B1. Mix 25g of nano silica particles with 48mL of aminosilane coupling agent KH-550 and 1.3L of anhydrous ethanol evenly, react at 100℃ for 30h, centrifuge, wash and dry to obtain amino-modified nano silica particles.

[0065] B2. 17g of amino-modified nano silica particles were dispersed in 200mL of deionized water to obtain a dispersion. 24mL of pyruvic acid, 2.24g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 0.56g of N-hydroxysuccinimide were dissolved in 1L of deionized water, and the dispersion was added to react for 32h. After the reaction was completed, the particles were centrifuged, washed and dried to obtain nano silica particles with ketone groups on their surface.

[0066] Example 7

[0067] A method for synthesizing a betaine-type zwitterionic polymer oil displacement agent includes the following steps:

[0068] S1. Allyl polyoxyethylene ether with a molecular weight of 102 was dissolved in dichloromethane (mass concentration of 10%), and manganese dioxide was added. The reaction was carried out at 25°C for 3 hours. The molar ratio of allyl polyoxyethylene ether to manganese dioxide was 1:1.5, resulting in an unsaturated monomer containing aldehyde groups and ether bonds. The unsaturated monomer containing aldehyde groups and ether bonds with a molar ratio of 1:1.05 and 3,3'-dithiodipropionyl hydrazide were dissolved in deionized water (mass concentration of 0.2%), and a 5 mol / L acetic acid solution was added (the molar ratio of acetic acid to 3,3'-dithiodipropionyl hydrazide was 1:1). The reaction was carried out at 50°C for 24 hours, resulting in an unsaturated monomer containing hydrazide groups and ether bonds.

[0069] S2. Acrylamide and acrylic acid were dissolved in deionized water, and the pH of the system was adjusted to 6. Unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 1 were added. The mixture was stirred until the solution (total monomer mass concentration in the solution was 25%) was clear. Nitrogen gas was introduced, and dimethyl azobisisobutyrate (0.2% of the total monomer mass) was added. The mixture was reacted at 40°C for 5 hours. After the reaction was completed, the mixture was dehydrated and precipitated in anhydrous ethanol, dried, and pulverized to obtain the polymer. The molar ratio of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups was 70:8:7:1.3.

[0070] S3. The nano-silica particles with ketone groups on their surface prepared in Example 4 were added to deionized water and dispersed evenly to obtain a dispersion of nano-silica particles with ketone groups on their surface with a mass concentration of 2%. The polymer was added to deionized water (mass concentration of 0.2%) and stirred evenly. Then the dispersion of nano-silica particles with ketone groups on their surface was added and stirred evenly. A 2 mol / L acetic acid solution was added to adjust the pH to 5-5.5. The reaction was carried out for 36 hours. Granulation, drying and pulverization were performed to obtain a betaine-type zwitterionic polymer oil displacement agent, wherein the molar ratio of nano-silica particles with ketone groups on their surface to the polymer was 1:1.

[0071] Example 8

[0072] A method for synthesizing a betaine-type zwitterionic polymer oil displacement agent includes the following steps:

[0073] S1. Allyl polyoxyethylene ether with a molecular weight of 418 was dissolved in dichloromethane (mass concentration of 10%), and manganese dioxide was added. The reaction was carried out at 30°C for 3 hours. The molar ratio of allyl polyoxyethylene ether to manganese dioxide was 1:1.7, resulting in an unsaturated monomer containing aldehyde groups and ether bonds. The unsaturated monomer containing aldehyde groups and ether bonds with a molar ratio of 1:1.1 and 2,2'-dithiodiacetylhydrazine were dissolved in deionized water (mass concentration of 0.2%), and a 5 mol / L acetic acid solution was added (the molar ratio of acetic acid to 2,2'-dithiodiacetylhydrazine was 1:1). The reaction was carried out at 60°C for 28 hours, resulting in an unsaturated monomer containing hydrazide groups and ether bonds.

[0074] S2. Acrylamide and acrylic acid were dissolved in deionized water, and the pH of the system was adjusted to 7. Unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 2 were added. The mixture was stirred until the solution (total monomer mass concentration in the solution was 25%) was clear. Nitrogen gas was introduced, and azobisisopropylimidazoline hydrochloride (accounting for 0.3% of the total monomer mass) was added. The mixture was reacted at 45°C for 4 hours. After the reaction was completed, the mixture was dehydrated and precipitated in anhydrous ethanol, dried, and pulverized to obtain the polymer. The molar ratio of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups was 75:6:8:1.5.

[0075] S3. The nano-silica particles with ketone groups on their surface prepared in Example 4 were added to deionized water and dispersed evenly to obtain a 3% (w / w) dispersion of nano-silica particles with ketone groups on their surface. The polymer was added to deionized water (w / w) with a mass concentration of 0.2% and stirred evenly. Then, the dispersion of nano-silica particles with ketone groups on their surface was added and stirred evenly. A 2 mol / L acetic acid solution was added to adjust the pH to 5.5. The reaction was carried out for 48 hours. The mixture was then granulated, dried, and pulverized to obtain a betaine-type zwitterionic polymer oil displacement agent, wherein the molar ratio of nano-silica particles with ketone groups on their surface to the polymer was 1.2:1.

[0076] Example 9

[0077] A method for synthesizing a betaine-type zwitterionic polymer oil displacement agent includes the following steps:

[0078] S1. Allyl polyoxyethylene ether with a molecular weight of 938 was dissolved in dichloromethane (mass concentration of 10%), and manganese dioxide was added. The reaction was carried out at 30°C for 3 hours. The molar ratio of allyl polyoxyethylene ether to manganese dioxide was 1:2, resulting in an unsaturated monomer containing aldehyde groups and ether bonds. The unsaturated monomer containing aldehyde groups and ether bonds with a molar ratio of 1:1.2 and adipic acid dihydrazide were dissolved in deionized water (mass concentration of 0.2%), and a 5 mol / L acetic acid solution was added (molar ratio of acetic acid to adipic acid dihydrazide was 1:1). The reaction was carried out at 70°C for 36 hours, resulting in an unsaturated monomer containing hydrazide groups and ether bonds.

[0079] S2. Dissolve acrylamide and acrylic acid in deionized water, adjust the pH of the system to 8, add unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 3, stir until the solution (total monomer mass concentration in the solution is 25%) is clear, purge with nitrogen gas, add azobisisobutyramidine hydrochloride (accounting for 0.5% of the total monomer mass) and react at 60°C for 3 hours. After the reaction is completed, dehydrate and precipitate in anhydrous ethanol, dry and pulverize to obtain the polymer, wherein the molar ratio of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups is 80:4:7:1.8;

[0080] S3. The nano-silica particles with ketone groups on their surface prepared in Example 6 were added to deionized water and dispersed evenly to obtain a dispersion of nano-silica particles with ketone groups on their surface with a mass concentration of 5%. The polymer was added to deionized water (mass concentration of 0.2%) and stirred evenly. Then the dispersion of nano-silica particles with ketone groups on their surface was added and stirred evenly. A 2 mol / L acetic acid solution was added to adjust the pH to 5.5. The reaction was carried out for 58 hours. The mixture was then granulated, dried, and pulverized to obtain a betaine-type zwitterionic polymer oil displacement agent, wherein the molar ratio of nano-silica particles with ketone groups on their surface to the polymer was 1.5:1.

[0081] Comparative Example 1

[0082] Compared with Example 8, in Comparative Example 1, the betaine-type functional monomer containing hydrophobic groups was replaced with hexadecyl acrylate and N,N-dimethyl (methacryloyloxyethyl)ammonium propanesulfonic acid inner salt in a molar ratio of 1:1. Other steps and raw materials were the same as in Example 8.

[0083] Comparative Example 2

[0084] Compared with Example 8, Comparative Example 2 did not add nano-silica particles with ketone groups on the surface, but acylhydrazone bonds were formed between polymer molecular chains. The preparation steps are as follows.

[0085] S1. Allyl polyoxyethylene ether with a molecular weight of 418 was dissolved in dichloromethane (mass concentration of 10%), and manganese dioxide was added and oxidized at 30°C for 3 hours. The molar ratio of allyl polyoxyethylene ether to manganese dioxide was 1:1.7, and an unsaturated monomer containing aldehyde group and ether bond was obtained.

[0086] S2. Dissolve acrylamide and acrylic acid in deionized water, adjust the pH of the system to 7, add unsaturated monomers containing aldehyde groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 2, stir until the solution (total monomer mass concentration in the solution is 25%) is clear, purge with nitrogen gas, add azobisisopropylimidazoline hydrochloride (0.3% of the total monomer mass) and react at 45°C for 4 hours. After the reaction is completed, dehydrate and precipitate in anhydrous ethanol, dry and pulverize to obtain the polymer, wherein the molar ratio of acrylamide, acrylic acid, unsaturated monomers containing aldehyde groups and ether bonds and betaine-type functional monomers containing hydrophobic groups is 75:6:8:1.5;

[0087] S3. Dissolve 2,2'-dithiodiacetylhydrazine in deionized water to obtain a 10% aqueous solution. Add the polymer to the deionized water (0.2% by mass) and stir until homogeneous. Then add the 2,2'-dithiodiacetylhydrazine aqueous solution and a 2 mol / L acetic acid solution to adjust the pH to 5.5. React for 48 hours, granulate, dry, and pulverize to obtain a betaine-type zwitterionic polymer oil displacement agent, wherein the molar ratio of 2,2'-dithiodiacetylhydrazine to the polymer is 1.2:1.

[0088] Comparative Example 3

[0089] Compared with Example 8, Comparative Example 3 did not add nano-silica particles with ketone groups on the surface, and no acylhydrazone bonds were formed between the polymer molecular chains. That is, step S3 was not performed, and the other steps and raw materials were the same as in Example 8.

[0090] Performance testing

[0091] (1) Solubility: The apparent viscosity of the polymer oil displacement agents (concentration of 1000 mg / L) prepared in Examples 7-9 and Comparative Examples 1-2 at different dissolution times was tested using a DV-II (Brookfield, USA) viscometer (test temperature 45℃, rotation speed 10 rpm) to obtain the time required for the polymer oil displacement agents to dissolve.

[0092] (2) Temperature resistance: Prepare a 40000 mg / L sodium chloride solution, and prepare a polymer oil displacement agent with a concentration of 2 g / L using the polymer oil displacement agents prepared in Examples 7-9 and Comparative Examples 1-2. Test the viscosity; then stir slowly at 85°C for 6 h and measure the test viscosity.

[0093] (3) Shear resistance: A mineralized water solution with a salinity of 12000 mg / L was prepared. The polymer oil displacement agents obtained in Examples 7-9 and Comparative Examples 1-3 were formulated into a polymer solution with a concentration of 3 g / L, and the viscosity was tested. Then, the viscosity was tested at a shear rate of 7.34 s⁻¹. -1 Viscosity at 2 min under shear; then tested at a shear rate of 200 s.-1 Viscosity at 2 min under shear; final test at a shear rate of 7.34 s. -1 Viscosity after 2 minutes of shearing.

[0094] Table 1

[0095]

[0096] Table 2

[0097]

[0098] As shown in Table 1, the betaine-type zwitterionic polymer oil displacement agent prepared in this invention has good solubility, with a viscosity exceeding 794.2 mPa·s in a 40,000 mg / L sodium chloride solution, exhibiting good salt resistance. After slow stirring at 85°C for 6 hours in a 40,000 mg / L sodium chloride solution, the viscosity retention rate of the betaine-type zwitterionic polymer oil displacement agent exceeds 80%, indicating that the betaine-type zwitterionic polymer oil displacement agent has excellent temperature resistance. As shown in Table 2, at 7.34 s... -1 After shearing at a low shear rate for 2 minutes, the solution viscosity decreased slightly, with a viscosity retention rate exceeding 85% at 200 s. -1 After shearing at a high shear rate for 2 minutes, the solution viscosity decreased more than that at a low shear rate. However, after further low-speed shearing, the viscosity increased again, with a viscosity retention rate of over 73%. The broken polymer chains recovered, indicating that the betaine-type zwitterionic polymer oil displacement agent has excellent shear resistance.

[0099] Comparing the data from Example 8 and Comparative Example 1, it can be seen that replacing the betaine-type functional monomers containing hydrophobic groups with hexadecyl acrylate and N,N-dimethyl(methacryloyloxyethyl)ammonium propanesulfonic acid inner salt leads to a decrease in the water solubility, temperature resistance, and shear resistance of the betaine-type zwitterionic polymer oil displacement agent. Comparing the data from Example 8 and Comparative Example 2, it can be seen that the absence of nano-silica particles results in a decrease in temperature resistance and shear resistance. Comparing the data from Example 8 and Comparative Example 3, it can be seen that the absence of nano-silica particles and the lack of acylhydrazone bonds between polymer segments significantly reduces the temperature resistance and shear resistance of the solution.

[0100] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0101] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for synthesizing a betaine-type zwitterionic polymer oil displacement agent, characterized in that: Includes the following steps: S1. Allyl polyoxyethylene ether is dissolved in an organic solvent, and manganese dioxide is added to carry out an oxidation reaction to obtain an unsaturated monomer containing aldehyde groups and ether bonds; the unsaturated monomer containing aldehyde groups and ether bonds and an organic small molecule containing hydrazide groups are dissolved in deionized water, acetic acid is added, and the reaction is carried out at 50-70℃ for 24-36 h to obtain an unsaturated monomer containing hydrazide groups and ether bonds. Organic small molecules containing hydrazide groups include at least one of 3,3'-dithiodipropionylhydrazide, 2,2'-dithiodiacetylhydrazide, 4,4'-dithiodibutyrylhydrazide, adipic acid dihydrazide, and malonate dihydrazide. S2. Dissolve acrylamide and acrylic acid in deionized water, adjust the pH of the system to 6-8, add unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups, stir until the solution is clear, introduce nitrogen gas, add initiator to carry out reaction, after the reaction is completed, dehydrate and precipitate in anhydrous ethanol, dry and pulverize to obtain polymer. The method for preparing the betaine-type functional monomer containing a hydrophobic group includes the following steps: A1. Sodium N-methyltaurate and 4-chloro-1-butene undergo a nucleophilic substitution reaction at 40-55℃ for 1-2 hours to obtain an intermediate; A2. The intermediate and myristoyl chloride were subjected to a quaternization reaction at 5-10℃ for 3 hours to obtain a betaine-type functional monomer containing a hydrophobic group. S3. Add nano-silica particles with ketone groups on their surface to deionized water and disperse them evenly to obtain a nano-silica particle dispersion with ketone groups on their surface. Add the polymer to deionized water and stir evenly. Then add the nano-silica particle dispersion with ketone groups on its surface and stir evenly. Add acetic acid and adjust the pH to 5-5.

5. React for 36-58 hours to obtain a betaine-type zwitterionic polymer oil displacement agent.

2. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 1, characterized in that: In step S1, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:1.5-2, and the molecular weight of allyl polyoxyethylene ether is 102-938.

3. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 1, characterized in that: In step S1, the molar ratio of unsaturated monomers containing aldehyde groups and ether bonds to small organic molecules containing hydrazide groups is 1:(1.05-1.2).

4. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 1, characterized in that: In step S2, the molar ratio of acrylamide, acrylic acid, unsaturated monomers containing hydrazide groups and ether bonds, and betaine-type functional monomers containing hydrophobic groups is (70-80):(4-8):(7-10):(1.3-1.8). In step S3, the molar ratio of nano-silica particles with ketone groups on their surface to the polymer is (1-1.5):

1.

5. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 1, characterized in that: In step A1, the molar ratio of sodium N-methyltaurate to 4-chloro-1-butene is 1:(1.05-1.15), and in step A2, the molar ratio of the intermediate to myristoyl chloride is 1:(1.1-1.3).

6. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 1, characterized in that: The method for preparing the nano-silica particles containing ketone groups on their surface includes the following steps: B1. Mix nano-silica particles, aminosilane coupling agent, and anhydrous ethanol evenly, react at 90-100℃ for 24-36h, centrifuge, wash, and dry to obtain amino-modified nano-silica particles. B2. Disperse amino-modified nano-silica particles in deionized water to obtain a dispersion; dissolve pyruvic acid and catalyst in deionized water, add the dispersion and react for 18-32 hours. After the reaction is completed, centrifuge, wash and dry to obtain nano-silica particles with ketone groups on the surface.

7. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 6, characterized in that: In step B1, the ratio of nano-silica particles to aminosilane coupling agent and anhydrous ethanol is (2.2-2.5)g:(3.9-4.8)mL:(100-130)mL.

8. The method for synthesizing a betaine-type zwitterionic polymer oil displacement agent according to claim 6, characterized in that: In step B2, the ratio of amino-modified nano-silica particles, pyruvic acid, and catalyst is (1.5-1.7)g:(2.1-2.4)mL:(0.21-0.28)g.

9. A betaine-type zwitterionic polymer oil displacement agent synthesized using the method described in any one of claims 1-8.

Images