Betaine type zwitterionic polymer oil-displacing agent and synthesis method thereof

Abstract

The invention relates to a betaine type zwitterionic polymer oil-displacing agent and a synthesis method, and belongs to the technical field of oil reservoir development. A hydrophobic group and a betaine group are grafted on the same monomer, a water-soluble sulfonic acid group in the betaine group has strong hydration performance, the water solubility of the hydrophobic group can be improved, and the water-soluble sulfonic acid group in the betaine group has strong hydration performance; meanwhile, ether bonds are introduced into the polymer, so that the water solubility of the polymer is further improved. A dynamic acylhydrazone bond formed by reaction of nano silicon dioxide particles containing ketone groups on the surfaces and hydrazide groups of polymer side chains is connected with a polymer molecular chain to form a three-dimensional network structure, and then physical cross-linking and nano silicon dioxide particles formed by hydrophobic association are cooperated; the temperature resistance, the salt resistance and the shearing resistance of the polymer oil displacement agent are obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil reservoir development, and in particular relates to a betaine type zwitterionic polymer oil displacement agent and a synthesis method thereof. Background Art

[0002] With the development of social economy, people are becoming more and more dependent on oil and its related products. However, with the continuous reduction of proven oil reserves and the gradual shift of oil field development to more difficult high-temperature, high-mineralization, high-water-content, low-permeability tight oil reservoirs, oil as a non-renewable resource has become more and more valuable. Therefore, there is an urgent need to develop oil fields more effectively to increase oil production to meet the growing needs of industrial production. Polymer flooding refers to a production-increasing measure that injects polymers into the formation for oil recovery. Traditionally used at home and abroad is polyacrylamide, which has the advantages of good water solubility, strong fluidity and low cost. However, in the deep well environment of high temperature and high salt, the electrostatic repulsion between carboxylic acid groups will be weakened, resulting in a significant decrease in the apparent viscosity of the system. At the same time, polyacrylamide is highly sensitive to salt, resulting in poor thermal stability and poor shear resistance, which greatly reduces the recovery rate of crude oil in the area.

[0003] In view of the high temperature and high salt deep well environment, the commonly used method is to modify acrylamide copolymers to enable them to withstand harsh conditions, among which hydrophobic associating polymers are one type of modified products. By introducing hydrophobic groups to generate strong intermolecular forces, the polymer oil displacement agent forms intermolecular associations, forming a polymer network structure with a certain strength, thereby achieving a viscosity-increasing effect. However, hydrophobic associating polymers have the problem of slow dissolution, which greatly limits the viscosity-increasing effect of hydrophobic associating polymers. Therefore, it is necessary to solve the above problems and provide a polymer oil displacement agent that is salt-resistant, temperature-resistant, shear-resistant, and highly soluble. Summary of the invention

[0004] The purpose of the present invention is to provide a betaine type zwitterionic polymer oil-displacing agent and a synthesis method, wherein a hydrophobic group and a betaine group are grafted onto the same monomer, and the water-soluble sulfonic acid group in the betaine group has a strong hydration property, which can increase the water solubility of the hydrophobic group, and an ether bond is introduced into the polymer, further improving the water solubility of the polymer. The present invention utilizes a dynamic acylhydrazone bond formed by the reaction of nano-silica particles containing keto groups on the surface and hydrazide groups on the polymer side chains to connect polymer molecular chains to form a three-dimensional network structure, and then cooperates with the physical crosslinking formed by hydrophobic association and nano-silica particles to significantly improve the temperature and salt resistance, shear resistance and solubility of the polymer oil-displacing agent.

[0005] The technical problem to be solved by the present invention is that the polyacrylamide traditionally used at home and abroad will weaken the electrostatic repulsion between carboxylic acid groups in a deep well environment with high temperature and high salt, resulting in a significant decrease in the apparent viscosity of the system. At the same time, polyacrylamide is very sensitive to salt, resulting in poor thermal stability and poor shear resistance, thereby greatly reducing the recovery rate of crude oil in the region. Hydrophobic associating polymers introduce hydrophobic groups to generate strong intermolecular forces to form intermolecular associations in polymer oil-displacing agents, forming a polymer network structure with a certain strength, thereby achieving a viscosity-increasing effect. However, hydrophobic associating polymers have the problem of slow dissolution, which greatly limits the viscosity-increasing effect of hydrophobic associating polymers.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

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

[0008] S1. Dissolve allyl polyoxyethylene ether in an organic solvent, add manganese dioxide for oxidation reaction, and obtain an unsaturated monomer containing an aldehyde group and an ether bond; dissolve the unsaturated monomer containing an aldehyde group and an ether bond and an organic small molecule containing a hydrazide group in deionized water, add acetic acid, and react at 50-70° C. for 24-36 hours to obtain an unsaturated monomer containing a hydrazide group and an ether bond;

[0009] In the above preparation process, the hydroxyl group in the allyl polyoxyethylene ether is oxidized to an aldehyde group to obtain an unsaturated monomer containing an aldehyde group and an ether bond, which is then reacted with an organic small molecule containing two hydrazide groups to obtain an unsaturated monomer containing a hydrazide group and an ether bond.

[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 temperature of the oxidation reaction is 25-30°C.

[0013] Furthermore, in step S1, the organic small molecule containing a hydrazide group includes at least one of 3,3'-dithiodipropionyl hydrazide, 2,2'-dithiodiacetyl hydrazide, 4,4'-dithiodibutyryl hydrazide, adipic acid dihydrazide, and malonic acid dihydrazide.

[0014] Furthermore, in step S1, the molar ratio of the unsaturated monomer containing an aldehyde group and an ether bond to the organic small molecule containing a hydrazide group is 1:(1.05-1.2).

[0015] S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the pH of the system to 6-8, adding an unsaturated monomer containing a hydrazide group and an ether bond and a betaine-type functional monomer containing a hydrophobic group, stirring until the solution is clear, introducing nitrogen, adding an initiator to react, and after the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying, and crushing to obtain a polymer;

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

[0017] Furthermore, in step S2, the initiator is at least one of dimethyl azobisisobutyrate, azobisisopropylimidazoline hydrochloride, azodicarbonamide and azobisisobutylamidine hydrochloride; the amount of the 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°C and the reaction time is 3-8h.

[0019] S3. Add the nano-silica particles containing ketone groups on the surface into deionized water and disperse them evenly to obtain a dispersion of nano-silica particles containing ketone groups on the surface. Add the polymer into the deionized water and stir evenly. Then add the dispersion of nano-silica particles containing ketone groups on the 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 hydrazide 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-silicon dioxide particles containing keto groups on the surface is 2-5%.

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

[0023] Furthermore, the preparation method of the betaine-type functional monomer containing a hydrophobic group comprises the following steps:

[0024] A1, reacting sodium N-methyltaurate with 4-chloro-1-butene at 40-55°C for 1-2h to obtain an intermediate;

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

[0026] A2. The intermediate and myristoyl chloride are reacted at 5-10° C. for 3 h to form a quaternary ammonium salt, thereby obtaining a betaine-type functional monomer containing a hydrophobic group.

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

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

[0029] Furthermore, the method for preparing nano-silicon dioxide particles containing ketone groups on the surface comprises the following steps:

[0030] B1, mixing nano-silica particles, aminosilane coupling agent and anhydrous ethanol evenly, reacting at 90-100° C. for 24-36 hours, centrifuging, washing and drying to obtain amino-modified nano-silica particles;

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

[0032] B2. Dispersing amino-modified nano-silica particles in deionized water to obtain a dispersion; dissolving pyruvic acid and a catalyst in deionized water, adding the dispersion to react for 18-32 hours, and centrifuging, washing, and drying after the reaction to obtain nano-silica particles containing keto groups on the surface.

[0033] Furthermore, 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 usage 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 nano-silica particles containing ketone groups on the surface, the nano-silica particles are first modified by using an aminosilane coupling agent, and then the amino group is reacted with pyruvic acid to obtain the nano-silica particles containing 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] Beneficial effects of the present invention:

[0038] (1) In the technical solution of the present invention, the hydrophobic group and the betaine group 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, an ether bond is introduced into the side chain of the polymer, further improving the water solubility of the polymer.

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

[0040] (3) In the technical solution of the present invention, the viscosity of the oil-displacing agent is improved, and the temperature resistance, salt resistance and shear resistance of the oil-displacing agent are enhanced through the physical cross-linking network formed by the hydrophobic association interaction between the hydrophobic segments of the polymer oil-displacing agent, the three-dimensional network structure formed by connecting the polymer molecular chains through acylhydrazone bonds, and the synergistic effect of the nano-silica particles and the betaine groups. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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. Add sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.1 into methanol, stir evenly, and react at 40°C for 1 hour to obtain an intermediate;

[0045] A2. The intermediate and myristic acid chloride in a molar ratio of 1:1.1 are mixed 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. Add sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.2 into methanol, stir evenly, and react at 45°C for 1.5h to obtain an intermediate;

[0049] A2. The intermediate and myristic acid chloride in a molar ratio of 1:1.2 are mixed and reacted at 5°C for 3 hours 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. Add sodium N-methyltaurate and 4-chloro-1-butene in a molar ratio of 1:1.3 into methanol, stir evenly, and react at 55°C for 2h to obtain an intermediate;

[0053] A2. The intermediate and myristic acid chloride in a molar ratio of 1:1.3 were mixed 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-silicon dioxide particles containing ketone groups on the surface, comprising the following steps:

[0056] B1, 22g of nano-silica particles, 39mL of aminosilane coupling agent KH-550, and 1L of anhydrous ethanol were mixed evenly, reacted at 90°C for 24h, centrifuged, washed, and dried to obtain amino-modified nano-silica particles;

[0057] B2. Disperse 15 g of amino-modified nano-silica particles in 150 mL of deionized water to obtain a dispersion; dissolve 21 mL of pyruvic acid, 1.4 g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 0.7 g of N-hydroxysuccinimide in 1 L of deionized water, add the dispersion and react for 18 h. After the reaction is completed, centrifuge, wash and dry to obtain nano-silica particles containing keto groups on the surface.

[0058] Example 5

[0059] This embodiment provides a method for preparing nano-silicon dioxide particles containing ketone groups on the surface, comprising the following steps:

[0060] B1, 23g of nano-silica particles, 45mL of aminosilane coupling agent KH-550, and 1.2L of anhydrous ethanol were mixed evenly, reacted at 90°C for 36h, centrifuged, washed, and dried to obtain amino-modified nano-silica particles;

[0061] B2. Disperse 16 g of amino-modified nano-silica particles in 180 mL of deionized water to obtain a dispersion; dissolve 22 mL of pyruvic acid, 1.4 g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.1 g of N-hydroxysuccinimide in 1 L of deionized water, add the dispersion and react for 24 hours. After the reaction is completed, centrifuge, wash and dry to obtain nano-silica particles containing keto groups on the surface.

[0062] Example 6

[0063] This embodiment provides a method for preparing nano-silicon dioxide particles containing ketone groups on the surface, comprising the following steps:

[0064] B1, 25g of nano-silica particles, 48mL of aminosilane coupling agent KH-550, and 1.3L of anhydrous ethanol were mixed evenly, reacted at 100°C for 30h, centrifuged, washed, and dried to obtain amino-modified nano-silica particles;

[0065] B2. Disperse 17 g of amino-modified nano-silica particles in 200 mL of deionized water to obtain a dispersion; dissolve 24 mL of pyruvic acid, 2.24 g of N-3-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 0.56 g of N-hydroxysuccinimide in 1 L of deionized water, add the dispersion and react for 32 hours. After the reaction is completed, centrifuge, wash and dry to obtain nano-silica particles containing keto groups on the surface.

[0066] Example 7

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

[0068] S1. Dissolve allyl polyoxyethylene ether with a molecular weight of 102 in dichloromethane (mass concentration of 10%), add manganese dioxide and perform oxidation reaction at 25°C for 3 hours, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:1.5, and obtain an unsaturated monomer containing an aldehyde group and an ether bond; dissolve the unsaturated monomer containing an aldehyde group and an ether bond and 3,3'-dithiodipropionyl hydrazide with a molar ratio of 1:1.05 in deionized water (mass concentration of 0.2%), add acetic acid solution with a concentration of 5 mol / L (the molar ratio of acetic acid to 3,3'-dithiodipropionyl hydrazide is 1:1), and react at 50°C for 24 hours to obtain an unsaturated monomer containing a hydrazide group and an ether bond;

[0069] S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the system pH to 6, adding unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 1, stirring until the solution (the total monomer mass concentration in the solution is 25%) is clear, passing nitrogen, adding dimethyl azobisisobutyrate (accounting for 0.2% of the total monomer mass) and reacting at 40° C. for 5 hours. After the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying and crushing to obtain a 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 70:8:7:1.3;

[0070] S3. The nano-silica particles containing ketone groups on the surface prepared in Example 4 are added to deionized water and dispersed evenly to obtain a dispersion of nano-silica particles containing ketone groups on the surface with a mass concentration of 2%. The polymer is added to deionized water (mass concentration is 0.2%) and stirred evenly, and then the dispersion of nano-silica particles containing ketone groups on the surface is added and stirred evenly. An acetic acid solution with a concentration of 2 mol / L is added, the pH is adjusted to 5-5.5, the reaction is carried out for 36 hours, granulated, dried, and crushed to obtain a betaine-type zwitterionic polymer oil-displacing agent, wherein the molar ratio of the nano-silica particles containing ketone groups on the surface to the polymer is 1:1.

[0071] Example 8

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

[0073] S1. Dissolve allyl polyoxyethylene ether with a molecular weight of 418 in dichloromethane (mass concentration of 10%), add manganese dioxide and perform oxidation reaction at 30°C for 3 hours, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:1.7, and obtain an unsaturated monomer containing an aldehyde group and an ether bond; dissolve the unsaturated monomer containing an aldehyde group and an ether bond and 2,2'-dithiodiacetylhydrazine with a molar ratio of 1:1.1 in deionized water (mass concentration of 0.2%), add acetic acid solution with a concentration of 5 mol / L (the molar ratio of acetic acid to 2,2'-dithiodiacetylhydrazine is 1:1), and react at 60°C for 28 hours to obtain an unsaturated monomer containing a hydrazide group and an ether bond;

[0074] S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the system pH to 7, adding unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 2, stirring until the solution (the total monomer mass concentration in the solution is 25%) is clear, passing nitrogen, adding azodiisopropylimidazoline hydrochloride (accounting for 0.3% of the total monomer mass) and reacting at 45° C. for 4 hours. After the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying and crushing to obtain a 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 75:6:8:1.5;

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

[0076] Example 9

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

[0078] S1. Dissolve allyl polyoxyethylene ether with a molecular weight of 938 in dichloromethane (mass concentration of 10%), add manganese dioxide and perform oxidation reaction at 30°C for 3 hours, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:2, and obtain an unsaturated monomer containing an aldehyde group and an ether bond; dissolve an unsaturated monomer containing an aldehyde group and an ether bond and adipic acid dihydrazide with a molar ratio of 1:1.2 in deionized water (mass concentration of 0.2%), add acetic acid solution with a concentration of 5 mol / L (the molar ratio of acetic acid to adipic acid dihydrazide is 1:1), and react at 70°C for 36 hours to obtain an unsaturated monomer containing a hydrazide group and an ether bond;

[0079] S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the system pH to 8, adding unsaturated monomers containing hydrazide groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 3, stirring until the solution (the total monomer mass concentration in the solution is 25%) is clear, passing nitrogen, adding azobisisobutylamidine hydrochloride (accounting for 0.5% of the total monomer mass) and reacting at 60° C. for 3 hours. After the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying and crushing to obtain a 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 containing ketone groups on the surface prepared in Example 6 are added to deionized water and dispersed evenly to obtain a dispersion of nano-silica particles containing ketone groups on the surface with a mass concentration of 5%. The polymer is added to deionized water (mass concentration is 0.2%) and stirred evenly, and then the dispersion of nano-silica particles containing ketone groups on the surface is added and stirred evenly. An acetic acid solution with a concentration of 2 mol / L is added, the pH is adjusted to 5.5, the reaction is carried out for 58 hours, granulated, dried, and crushed to obtain a betaine-type zwitterionic polymer oil-displacing agent, wherein the molar ratio of the nano-silica particles containing ketone groups on the surface to the polymer is 1.5:1.

[0081] Comparative Example 1

[0082] Compared with Example 8, in Comparative Example 1, the betaine-type functional monomer containing a hydrophobic group is replaced with hexadecyl acrylate and N,N-dimethyl(methacryloyloxyethyl)ammoniumpropanesulfonic acid salt in a molar ratio of 1:1, and the other steps and raw materials are synchronized with Example 8.

[0083] Comparative Example 2

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

[0085] S1. Dissolve allyl polyoxyethylene ether with a molecular weight of 418 in dichloromethane (mass concentration of 10%), add manganese dioxide and perform oxidation reaction at 30°C for 3 hours, the molar ratio of allyl polyoxyethylene ether to manganese dioxide is 1:1.7, and obtain an unsaturated monomer containing an aldehyde group and an ether bond;

[0086] S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the system pH to 7, adding unsaturated monomers containing aldehyde groups and ether bonds and betaine-type functional monomers containing hydrophobic groups prepared in Example 2, stirring until the solution (the total monomer mass concentration in the solution is 25%) is clear, passing nitrogen, adding azodiisopropylimidazoline hydrochloride (accounting for 0.3% of the total monomer mass) and reacting at 45° C. for 4 hours. After the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying and crushing to obtain a 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 an aqueous solution with a mass concentration of 10%, add the polymer into deionized water (mass concentration of 0.2%) and stir evenly, then add the 2,2'-dithiodiacetylhydrazine aqueous solution, add acetic acid solution with a concentration of 2 mol / L, adjust the pH to 5.5, react for 48 hours, granulate, dry and crush 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, in Comparative Example 3, no nano-silica particles containing keto groups on the surface are added, and no acylhydrazone bonds are formed between polymer molecular chains, that is, step S3 is not performed, and other steps and raw materials are the same as in Example 8.

[0090] Performance Testing

[0091] (1) Solubility: The apparent viscosity of the polymer oil-displacing 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 was 45° C., rotation speed was 10 rpm), and the time required for the polymer oil-displacing agent to dissolve was obtained;

[0092] (2) Temperature resistance: A 40000 mg / L sodium chloride solution was prepared, and the polymer oil-displacing agents prepared in Examples 7-9 and Comparative Examples 1-2 were prepared into a polymer solution with a concentration of 2 g / L, and the viscosity was tested; then the solution was slowly stirred at 85° C. for 6 h, and the test viscosity was measured;

[0093] (3) Shear resistance: Prepare mineral water with a mineralization degree of 12000 mg / L, prepare the polymer oil-displacing agents prepared in Examples 7-9 and Comparative Examples 1-3 into a polymer solution with a concentration of 3 g / L, and test the viscosity; then test the viscosity of the polymer solution at a shear rate of 7.34 s -1 The viscosity of the sample was measured at a shear rate of 200 s-1 The viscosity of the sample was measured at a shear rate of 7.34 s -1 Viscosity at 2 min of shear.

[0094] Table 1

[0095]

[0096] Table 2

[0097]

[0098] It can be seen from the data in Table 1 that the betaine-type zwitterionic polymer oil-displacing agent prepared by the present invention has good solubility, and the viscosity can reach 794.2 mPa·s or more in a 40000 mg / L sodium chloride solution, and has good salt resistance. The betaine-type zwitterionic polymer oil-displacing agent is slowly stirred at 85°C for 6 hours in a 40000 mg / L sodium chloride solution, and the viscosity retention rate exceeds 80%, indicating that the betaine-type zwitterionic polymer oil-displacing agent has excellent temperature resistance. It can be seen from the data in Table 2 that at 7.34s -1 After 2 min of shearing at a low shear rate, the solution viscosity decreased slightly, and the viscosity retention rate exceeded 85%. -1 After shearing for 2 minutes at high shear rate, the solution viscosity decreased more than that at low shear rate, but after low shear rate, the viscosity increased again, and the viscosity retention rate exceeded 73%. The broken polymer chain segments recovered again, indicating that the betaine-type zwitterionic polymer oil displacement agent has excellent shear resistance.

[0099] Comparative Example 8 and Comparative Example 1 show that the water solubility of the betaine-type zwitterionic polymer oil displacement agent decreases, and the temperature resistance and shear resistance also decrease due to the replacement of the betaine-type functional monomer containing a hydrophobic group with hexadecyl acrylate and N,N-dimethyl (methacryloyloxyethyl) ammonium propanesulfonic acid inner salt. Comparative Example 8 and Comparative Example 2 show that the temperature resistance and shear resistance decrease due to the absence of nano-silica particles. Comparative Example 8 and Comparative Example 3 show that the temperature resistance and shear resistance of the solution decrease significantly due to the absence of nano-silica particles and the absence of acylhydrazone bonds between polymer segments.

[0100] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0101] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for synthesizing a betaine-type zwitterionic polymer oil-displacing agent, characterized in that: The following steps are involved: S1. Dissolve allyl polyoxyethylene ether in an organic solvent, add manganese dioxide for oxidation reaction, and obtain an unsaturated monomer containing an aldehyde group and an ether bond; dissolve the unsaturated monomer containing an aldehyde group and an ether bond and an organic small molecule containing a hydrazide group in deionized water, add acetic acid, and react at 50-70° C. for 24-36 hours to obtain an unsaturated monomer containing a hydrazide group and an ether bond; S2, dissolving acrylamide and acrylic acid in deionized water, adjusting the pH of the system to 6-8, adding an unsaturated monomer containing a hydrazide group and an ether bond and a betaine-type functional monomer containing a hydrophobic group, stirring until the solution is clear, introducing nitrogen, adding an initiator to react, and after the reaction is completed, dehydrating and precipitating in anhydrous ethanol, drying, and crushing to obtain a polymer; S3. Add the nano-silica particles containing ketone groups on the surface into deionized water and disperse them evenly to obtain a dispersion of nano-silica particles containing ketone groups on the surface. Add the polymer into the deionized water and stir evenly. Then add the dispersion of nano-silica particles containing ketone groups on the 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-displacing agent according to claim 1, characterized in that: In the 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-displacing agent according to claim 1, characterized in that: In the step S1, the molar ratio of the unsaturated monomer containing an aldehyde group and an ether bond to the organic small molecule containing a hydrazide group is 1:(1.05-1.2).

4. The method for synthesizing a betaine-type zwitterionic polymer oil-displacing agent according to claim 1, characterized in that: In the step S2, the molar ratio of acrylamide, acrylic acid, unsaturated monomer containing hydrazide group and ether bond and betaine type functional monomer containing hydrophobic group is (70-80): (4-8): (7-10): (1.3-1.8), and in the step S3, the molar ratio of nano-silica particles containing keto group on the surface and 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: The method for preparing the betaine-type functional monomer containing a hydrophobic group comprises the following steps: A1, reacting sodium N-methyltaurate with 4-chloro-1-butene at 40-55°C for 1-2h to obtain an intermediate; A2. The intermediate and myristoyl chloride are reacted at 5-10° C. for 3 h to form a quaternary ammonium salt, thereby obtaining a betaine-type functional monomer containing a hydrophobic group.

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

7. 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 silicon dioxide particles containing ketone groups on the surface comprises the following steps: B1, mixing nano-silica particles, aminosilane coupling agent and anhydrous ethanol evenly, reacting at 90-100° C. for 24-36 hours, centrifuging, washing and drying to obtain amino-modified nano-silica particles; B2. Dispersing amino-modified nano-silica particles in deionized water to obtain a dispersion; dissolving pyruvic acid and a catalyst in deionized water, adding the dispersion to react for 18-32 hours, and centrifuging, washing, and drying after the reaction to obtain nano-silica particles containing keto groups on the surface.

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

9. The method for synthesizing a betaine type zwitterionic polymer oil-displacing agent according to claim 7, characterized in that: In the step B2, the usage 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.

10. A betaine type zwitterionic polymer oil-displacing agent synthesized by the method for synthesizing a betaine type zwitterionic polymer oil-displacing agent according to any one of claims 1 to 9.

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