CN114478907A - Polyacrylamide-based anion-cation composite polymer and preparation method and application thereof - Google Patents

Abstract

The invention relates to a polyacrylamide-based anion-cation composite polymer and a preparation method and application thereof. The polymer comprises acrylamide structural units, anionic monomer structural units, nonionic monomer structural units, optional formula (I) orA nonionic interface active branching structural unit shown in a formula (II), a cationic interface active branching structural unit shown in a formula (III) or a formula (IV), an anionic interface active branching structural unit shown in a formula (V) or a formula (VI), and an optional cationic monomer structural unit:

Description

Polyacrylamide-based anion-cation composite polymer and preparation method and application thereof

Technical Field

The invention relates to the field of oil extraction, in particular to a polyacrylamide-based anion-cation composite polymer and a preparation method and application thereof.

Background

polymer-Surfactant (SP) flooding or polymer-surfactant-base (ASP) is two types of enhanced oil recovery methods developed following surfactant and polymer flooding. The polymer and the surfactant are compounded, the surfactant is mainly used for reducing the surface tension of an aqueous solution and reducing the oil-water interfacial tension to further achieve the purpose of improving the petroleum recovery ratio, and the polymer oil displacement agent is mainly used for increasing the viscosity of a displacement phase in an oil reservoir by utilizing the strong tackifying capacity of a water-soluble polymer, improving the fluidity ratio and adjusting the stratum permeability to achieve the purpose of improving the petroleum recovery ratio. Fluidity control and interface activity improvement are simultaneously realized through composite use.

However, the two oil displacement agents have large body characteristic difference, and the problems of chromatographic elution cannot play the best role. To solve this problem, researchers have proposed the idea of a polyepiter, a macromolecular surfactant. It has been reported in literature that macromolecular surfactants can reduce oil-water interfacial tension while viscosifying, but the extent of IFT reduction is limited, so that the use of polyepithelixes in EOR is less than that of polymers or surfactant flooding.

Because the synthesis of the prior polymer surfactant is mainly obtained by copolymerizing acrylamide and an surfactant monomer, hexadecyl trimethyl ammonium chloride, alkyl acrylamide sulfonate derivatives and the like are generally independently selected, and the effective compatibility of the surfactant monomers with different structures is not considered, the ultra-low interfacial tension is difficult to achieve, the effectiveness is questioned, and the interfacial tension value is generally 0.1-15 mN/m. Although the effect of hydrophobically modified water-soluble polymers on EOR is superior to that of conventional polymers, the degree to which their interfacial behavior is important to improve oil recovery efficiency is still unclear. The major problem with current polymeric surfactant applications is the inability to achieve lower interfacial tensions while maintaining higher product viscosities. Meanwhile, the polyacrylamide-based polymer inherits the determination that the temperature resistance and salt resistance of polyacrylamide are insufficient, so that the polyacrylamide-based polymer is a potential hazard of the surface-sizing agent.

The invention provides a polyacrylamide-based anion-cation composite polymer surfactant which is a method for solving the existing problems, and the effective combination of anion-cation non-ionic active structural units is introduced into a polyacrylamide main chain, so that a product has higher interfacial activity and interfacial stability, and the interfacial tension between a product aqueous solution and crude oil can be effectively reduced. The compatibility of the yin-yang composite active structural units also effectively improves the temperature resistance and salt resistance of the product. Meanwhile, the invention also relates to a multi-element composite redox initiation system, which can ensure high molecular weight of the product while introducing a large amount of interface active monomers, thereby ensuring high viscosity of the product aqueous solution. The dual functions of high viscosity and high interfacial activity ensure high sweep efficiency and high microscopic oil displacement efficiency of the product aqueous solution in the oil displacement process, thereby improving the oil recovery ratio.

Disclosure of Invention

The invention aims to solve the technical problems of insufficient interfacial activity and insufficient temperature and salt resistance of the existing polymer surfactant. Therefore, the invention provides a yin-yang composite polymer surfactant, wherein a multi-branched structure is constructed on a main chain by introducing a yin-yang composite interfacial activity branched chain on a polyacrylamide main chain, so that a product has higher interfacial activity and interfacial stability when arranged on an interface, and the interfacial tension between a product aqueous solution and crude oil can be effectively reduced.

The second technical problem to be solved by the invention is to solve the problem that the molecular weight of a polymerization product is greatly influenced when the surface active monomer is more in types and the content is higher, so that the invention provides a multi-element composite initiation system, the concentration of free radicals effectively decomposed from an initiator in the whole polymerization process is controlled at a lower level, the double-radical termination probability is effectively reduced, the molecular weight of the product is improved, and the high viscosity of the aqueous solution of the product is further ensured.

The third technical problem to be solved by the invention is to provide a preparation method of a polyacrylamide-based anion-cation composite polymer surfactant corresponding to the first and second technical problems.

In order to solve one of the above problems, the present invention provides a polyacrylamide-based anion-cation complex polymer, which comprises an acrylamide structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, an optional nonionic interfacial activity branched structural unit represented by formula (I) or formula (II), a cationic interfacial activity branched structural unit represented by formula (III) or formula (IV), an anionic interfacial activity branched structural unit represented by formula (V) or formula (VI), and an optional cationic monomer structural unit:

wherein R 'is a hydrogen atom or a methyl group, and R' is-O-, -CH₂-、-CH₂O-, -COO-or-CONH-, m ═ 0 or 1, R₁Is C₁～C₂₈A hydrocarbon group of R₂Is a hydrogen atom or C₁～C₂₈N is the number of Poly(s) independently selected from

A and b are respectively 0-40 independently, and a and b are not 0 at the same time;

R₃an alkylene chain consisting of 1 to 28 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₈A hydrocarbon group of R₆Is C₁～C₂₈Is a hydrocarbon group of^-Is chloride ion, bromide ion, iodide ion;

y is a sulfonate, sulfate or carboxylate radical, R₇Is a hydrogen atom or C₁～C₂₈A hydrocarbon group of (1).

In the polyacrylamide-based anion-cation complex polymer of the present invention, preferably, R is₁Is C₆～C₂₀A hydrocarbon group of (a); r₂Is a hydrogen atom or C₆～C₂₀A hydrocarbon group of (a); a. b is respectively and independently 1-24;

R₃an alkylene chain consisting of 8 to 20 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₀A hydrocarbon group of (a); r₆Is C₆～C₂₀A hydrocarbon group of (a);

R₇is a hydrogen atom or C₆～C₂₀A hydrocarbon group of (1).

In the above technical scheme, the acrylamide structural unit is provided for an acrylamide monomer, the anionic monomer structural unit is provided for an anionic monomer, the cationic monomer structural unit is provided for a cationic monomer, the anionic surfactant branched structural unit is provided for an anionic surfactant branched monomer, the cationic surfactant branched structural unit is provided for a cationic surfactant branched monomer, and the nonionic surfactant branched structural unit is provided for a nonionic surfactant branched monomer.

In the technical scheme, the polyacrylamide-based anion-cation composite polymer is obtained by reacting a reaction system comprising the following components in parts by weight:

in the above technical solution, the anionic monomer may be selected from anionic monomers generally used in the art, and is preferably at least one selected from acrylic acid, methacrylic acid, vinylsulfonic acid, p-vinylbenzenesulfonic acid, maleic acid, fumaric acid, vinylbenzenesulfonic acid, allylsulfonic acid, allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and alkali metal salts or ammonium salts thereof.

In the above technical scheme, the cationic monomer may be selected from cationic monomers generally used in the art, and is preferably at least one selected from methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, and methacryloyloxyethyl dimethyl benzyl ammonium chloride.

In the above technical solution, the nonionic monomer may be selected from nonionic monomers generally used in the art, and is preferably at least one selected from the group consisting of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropylmethacrylamide, methylol methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, vinylpyrrolidone and tert-butylacrylamide.

In the technical scheme, the non-ionic surface active branched monomer is selected from at least one branched monomer shown in formulas (1) to (4),

the cationic surface active branching monomer is selected from at least one of the branching monomers shown in formulas (5) to (6),

the anionic surface active branched monomer is selected from at least one branched monomer shown in formulas (7) to (12),

wherein R is₁Is C₁～C₂₈A hydrocarbon group of R₂Is a hydrogen atom or C₁～C₂₈A and b are respectively 0-40 independently, and a and b are not 0 at the same time; preferably, R₁Is C₆～C₂₀A hydrocarbon group of (a); r₂Is a hydrogen atom or C₆～C₂₀A hydrocarbon group of (a); a. b is 1-24 independently.

R₃Is an alkyl chain consisting of 1 to 28 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₈A hydrocarbon group of R₆Is C₁～C₂₈Is a hydrocarbon group of^-Is chloride ion, bromide ion, iodide ion; preferably, R₃An alkylene chain consisting of 8 to 20 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₀A hydrocarbon group of (a); r₆Is C₆～C₂₀A hydrocarbon group of (2).

R₇Is a hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); preferably, R₇Is a hydrogen atom or C₆～C₂₀A hydrocarbon group of (1).

R₀Is selected from any one of the structures shown below,

in the above technical scheme, the reaction system further comprises at least one of the following components in parts by weight:

in the above technical scheme, the oxidant, the reducing agent and the azo initiator all belong to the part of a composite initiator system.

In the above technical solution, the oxidant is preferably at least one selected from persulfates such as potassium persulfate or sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, tert-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, and dicyclohexyl peroxydicarbonate;

the reducing agent is preferably at least one selected from sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N-dimethylaniline, tartaric acid, ferrous sulfate, N-diethylaniline, ferrous pyrophosphate, silver nitrate, mercaptan, ferrous chloride, tetraethylene imine, glycerol and pentaerythritol;

the azo initiator is preferably at least one selected from azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2 '-azo [2- (2-imidazolin-2-yl) propane ] dihydrochloride, azobis (2, 5-dimethyl-6-carboxyl) hexanenitrile and 4, 4' -azobis (4-cyanovaleric acid);

the cosolvent is preferably at least one selected from urea, ammonia water, sodium formate and sodium acetate;

the defoamer is a silicone water-based defoamer, such as any one of commercially available silicone water-based defoamers;

the chelating agent is preferably at least one of ethylenediamine tetraacetic acid, disodium ethylenediamine tetraacetic acid and tetrasodium ethylenediamine tetraacetic acid.

In the technical scheme, the polyacrylamide-based anion-cation composite polymer surfactant can be prepared by adopting an aqueous solution polymerization method for acrylamide, an anionic monomer, a nonionic monomer, an anionic interface active branched monomer, a cationic interface active branched monomer, an optional nonionic interface active branched monomer and an optional cationic monomer.

According to another aspect of the invention, the preparation method of the polyacrylamide-based anion-cation composite polymer is provided, and the components comprising acrylamide, an anionic monomer, a nonionic monomer, an anionic interface active branched monomer, a cationic interface active branched monomer, an optional nonionic interface active branched monomer and an optional cationic monomer are subjected to aqueous solution polymerization.

Preferably, the preparation method comprises the following steps:

1) dissolving a portion of the components including acrylamide, anionic monomer, nonionic monomer, anionic surface active branching monomer, cationic surface active branching monomer, optional nonionic surface active branching monomer, and optional cationic monomer in water;

2) adjusting the pH value of the solution to 6-12, and adjusting the temperature to 0-25 ℃;

3) and adding the rest components under the inert atmosphere and adiabatic conditions, carrying out polymerization reaction, and keeping the temperature for 1-8 hours to obtain the polymer after the temperature of the reaction system is raised to the maximum temperature.

In the above technical solution, preferably, the chelating agent, the antifoaming agent, and the cosolvent may be dissolved in water in step 1); the composite initiator system including the oxidizing agent, the reducing agent and the azo type initiator may be added in step 3).

According to a preferred embodiment of the present invention, the preparation method of the polyacrylamide-based anion-cation complex polymer comprises the following steps:

1) weighing certain amounts of acrylamide monomer, anionic monomer, optional cationic monomer, nonionic monomer, anionic surfactant branched monomer, cationic surfactant branched monomer, optional nonionic surfactant branched monomer, chelating agent, defoaming agent and cosolvent, and dissolving in a certain amount of deionized water;

2) adding sodium hydroxide to adjust the pH value to 6-12 to prepare an aqueous solution, and placing the aqueous solution in a refrigerator or a cold water bath to adjust the temperature to 0-25 ℃;

3) adding the solution into an adiabatic reactor, introducing inert gas for deoxidizing, wherein the time for introducing the inert gas for deoxidizing is 30-60 min;

4) respectively dissolving the composite initiator in water to prepare aqueous solutions, sequentially adding the aqueous solutions into a reactor, continuously introducing inert gas and stirring;

5) stopping introducing the inert gas after the polymerization reaction is started, and keeping the temperature of the reaction system constant for 1-8 hours after the temperature of the reaction system is raised to the maximum temperature; obtaining a polymerization product;

6) and (3) cutting the polymerization product into particles, drying at 70-90 ℃, and crushing to obtain the polyacrylamide-based yin-yang composite polymer.

The third aspect of the invention is to provide an application of the polyacrylamide-based anion-cation composite polymer or the polyacrylamide-based anion-cation composite polymer obtained by the preparation method in an oil displacement agent.

The polyacrylamide-based anion-cation composite polymer surfactant prepared by the technical scheme has the viscosity of more than 20mPas at 85 ℃ and the molecular weight of more than 1100 ten thousand in 120000mg/L saline water at the concentration of 2000ppm, and the interfacial tension between the saline water solution and crude oil reaches 10^-2mN/m。

The polyacrylamide-based anion-cation composite polymer surfactant obtained by the technical scheme of the invention has an anion-cation composite branched structure shown as the following formula, so that when product molecules are arranged on an oil-water interface, tighter arrangement structures can be formed between side chains and between the side chains and a main chain, the polyacrylamide-based anion-cation composite polymer surfactant can be more stable, and further has higher interfacial activity.

The structure shown above is the form of the polymer in the aqueous solution, and the side chains can form a more compact micelle-like arrangement structure due to the matching of the larger density of the side chains and the different lengths of the side chains on the polymer, and the structure is formed due to the difference of the hydrophilicity and the hydrophobicity of the side chains and the main chain.

The polyacrylamide-based anion-cation composite polymer surfactant obtained by the technical scheme can simultaneously improve the viscosity of an aqueous solution and reduce the tension of an oil-water interface, and meanwhile, the anion-cation composite structure also enables a product to have better tolerance under the condition of high mineralization degree, so that the product has better performance in high-mineralization-degree saline water.

The invention is further illustrated by the following examples.

Detailed Description

While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.

The starting materials used in the embodiments of the present invention are commercially available.

[ example 1 ]

25g of an acrylamide monomer, 3g of 2-acrylamido-2-methylpropanesulfonic acid, 3.6g of t-butylacrylamide, 0.5g of methacryloyloxyethyl trimethyl ammonium chloride, 2.25g of a branched monomer represented by the formula (1) (wherein R is₁Is alkyl of 12 carbons, a is 6, b is 1, wherein R₀Being an acrylamide group), 2.25g of a branched monomer represented by the formula (5) (wherein R is₀Is allyl, R₄、R₅Are respectively methyl and R₆Is C12 alkyl, M^-Is chloride ion), 2.25g of a branched monomer represented by the formula (7) (wherein R is₇Is alkyl of 12 carbons, wherein R₀Acrylamide group), 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of organic silicon water-based antifoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to be 7.0, the solution is added into an adiabatic reactor after the temperature of the solution is adjusted to be 10 ℃, nitrogen is introduced to remove oxygen, stirring is carried out simultaneously, and nitrogen is continuously introduced to remove oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2, 2' -azo [2- (2-imidazolin-2-yl) propane]Dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water, and the solution was sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in example 1 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. An oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, the viscosity of crude oil is 1.25mPas, the product solution is injected after the water-flooding reaches the water content of more than 98 percent, and the percent of the product solution for improving the crude oil recovery rate is measured. The data records are shown in table 1 for sample # 1.

It can be seen that the viscosity of the sample obtained in example 1 in 120000mg/L saline can reach 24.5mPas, the interfacial tension is 0.021mN/m, the molecular weight is 1050 ten thousand, and the recovery ratio can be improved by 13.4% after water flooding. The performance data can prove that the product effectively plays a role in expanding swept volume and improving microscopic displacement efficiency in the oil displacement process. Meanwhile, the viscosity can be maintained under the condition of 85 ℃ and 120000mg/L of mineralization degree, and the excellent temperature resistance and salt resistance of the product are also proved.

[ example 2 ]

25g of an acrylamide monomer, 3g of 2-acrylamido-2-methylpropanesulfonic acid, 3.6g of t-butylacrylamide, 0.5g of methacryloyloxyethyl trimethyl ammonium chloride, 1.25g of a branched monomer represented by the formula (1) (wherein R is₁Is alkyl of 12 carbons, a is 6, b is 1, R₀Being an acrylamide group), 1.25g of a branched monomer represented by the formula (5) (wherein R is₀Is allyl, R₄、R₅Are respectively methyl and R₆Is C12 alkyl, M^-Being chloride ion)1.25g of a branched monomer represented by the formula (7) (wherein R₇Is alkyl of 12 carbons, R₀Acrylamide group), 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of defoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to be 7.0, the solution is added into an adiabatic reactor after the temperature of the solution is adjusted to be 10 ℃, nitrogen is introduced to remove oxygen, the stirring is carried out, and the nitrogen is continuously introduced to remove the oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2, 2' -azo [2- (2-imidazolin-2-yl) propane]Dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water, and the solution was sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in example 2 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. An oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, the viscosity of crude oil is 1.25mPas, the product solution is injected after the water-flooding reaches the water content of more than 98 percent, and the percent of the product solution for improving the crude oil recovery rate is measured. The data records are shown in table 1 for sample # 2.

It can be seen that the sample obtained in example 2 has a viscosity of 22mPaS in 120000mg/L saline, an interfacial tension of 0.032mN/m, a molecular weight of 1220 ten thousand, and can improve the recovery efficiency by 12.3% after water flooding. The performance data can prove that the product effectively plays a role in expanding swept volume and improving microscopic displacement efficiency in the oil displacement process. Meanwhile, the viscosity can be maintained under the condition of 85 ℃ and 120000mg/L of mineralization degree, and the excellent temperature resistance and salt resistance of the product are also proved. Example 2 used a lower amount of branching monomer than example 1, and therefore the molecular weight was less affected, the molecular weight was higher, but the interfacial tension was slightly lower, and therefore the recovery factor was slightly lower than example 1.

[ example 3 ]

25g of an acrylamide monomer, 3g of 2-acrylamido-2-methylpropanesulfonic acid, 3.6g of t-butylacrylamide, 0.5g of methacryloyloxyethyl trimethyl ammonium chloride, 2.25g of a branched monomer represented by the formula (5) (wherein R is₀Is allyl, R₄、R₅Are respectively methyl and R₆Is C12 alkyl, M^-As bromide ion), 2.25g of a branched monomer represented by the formula (7) (wherein R is₇Is C12 alkyl, R₀Acrylamide group), 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of defoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to be 7.0, the solution is added into an adiabatic reactor after the temperature of the solution is adjusted to be 10 ℃, nitrogen is introduced to remove oxygen, the stirring is carried out, and the nitrogen is continuously introduced to remove the oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2, 2' -azo [2- (2-imidazolin-2-yl) propane]Dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water, and the solution was sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in example 3 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. The oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, and the viscosity of crude oil1.25mPas, injecting the product solution after the water-flooding reaches the water content of more than 98 percent, and measuring the percentage of the product solution for improving the crude oil recovery ratio. The data records are shown in table 1 for sample # 3.

It can be seen that the sample obtained in example 3 has a viscosity of 20.5mPaS in 120000mg/L saline, an interfacial tension of 0.024mN/m, a molecular weight of 1250 ten thousand, and can improve the recovery efficiency by 12.8% after water flooding. The performance data can prove that the product effectively plays a role in expanding swept volume and improving microscopic displacement efficiency in the oil displacement process. Meanwhile, the viscosity can be maintained under the condition of 85 ℃ and 120000mg/L of mineralization degree, and the excellent temperature resistance and salt resistance of the product are also proved. Compared with example 1, the branched monomer adopted in example 3 does not contain the nonionic surface active monomer, so that the salt resistance is slightly poor, the interfacial tension is slightly low, and the recovery efficiency increasing amplitude is also slightly low.

[ example 4 ]

25g of an acrylamide monomer, 3g of acrylic acid, 3.6g of methylolacrylamide, 0.5g of acryloyloxyethyldimethylbenzylammonium chloride, 1.25g of a branched monomer represented by the formula (1) (wherein R is₁Is alkyl of 12 carbons, a is 6, b is 1, R₀Being an acrylamide group), 1.75g of a branched monomer represented by the formula (3) (wherein R is₂Is alkyl of 10 carbons, R₀Allyl, a is 12, b is 0), 0.75g of a branched monomer of formula (5) (wherein R is₀Is allyl, R₄、R₅Are respectively methyl and R₆Is C12 alkyl, M^-Is bromide ion), 1.25g of a branched monomer represented by the formula (7) (wherein R is₇Is alkyl of 12 carbons, wherein R₀Acrylamide group), 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of defoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to be 7.0, the solution is added into an adiabatic reactor after the temperature of the solution is adjusted to be 10 ℃, nitrogen is introduced to remove oxygen, the stirring is carried out, and the nitrogen is continuously introduced to remove the oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2, 2' -azo [2- (2-imidazolin-2-yl) propane]Dihydrochloride, 0.00005g 4, 4' -azoNitrogen bis (4-cyanovaleric acid) was dissolved in 2g of deionized water and sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in example 4 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. An oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, the viscosity of crude oil is 1.25mPas, the product solution is injected after the water-flooding reaches the water content of more than 98 percent, and the percent of the product solution for improving the crude oil recovery rate is measured. The data records are shown in table 1 for sample # 4.

It can be seen that the viscosity of the sample obtained in example 4 in 120000mg/L saline can reach 19.8mPaS, the interfacial tension is 0.017mN/m, the molecular weight is 1000 ten thousand, and the recovery ratio can be improved by 11.3% after water flooding. The performance data can prove that the product effectively plays a role in expanding swept volume and improving microscopic displacement efficiency in the oil displacement process. Meanwhile, the viscosity can be maintained under the condition of 85 ℃ and 120000mg/L of mineralization degree, and the excellent temperature resistance and salt resistance of the product are also proved. The branched monomer represented by the formula (3) used in example 4 has a slightly lower reactivity ratio than those used in examples 2 and 3, and therefore has a smaller molecular weight, but has a higher interfacial tension activity and a slightly lower recovery ratio.

[ example 5 ]

10g of an acrylamide monomer, 252-acrylamido-2-methylpropanesulfonic acid, 8.5g of tert-butylacrylamide, 15.5g of methacryloyloxyethyltrimethylammonium chloride, 4.75g of a branched monomer represented by the formula (2) (wherein R is₀Is allyl, R₁Alkyl of 12 carbons, a is 2, b is 6), 5.25g of a branched monomer represented by formula (6) (wherein R is₀Is vinyl, R₃Is a hydrocarbon radical of C4, R₄、R₅Are respectively methyl and R₆Is C12 alkyl, M^-Is bromide ion), 4.25g of a branched monomer represented by the formula (12) (wherein R is₀Allyl, R7 is alkyl with 10 carbons), 0.02g of ethylene diamine tetraacetic acid disodium, 0.2g of urea and 0.001 part of antifoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to 7.0, the solution is added into an adiabatic reactor after the temperature is adjusted to 10 ℃, nitrogen is introduced to remove oxygen, stirring is carried out simultaneously, and nitrogen is continuously introduced to remove oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ammonium ferrous sulfate, 0.00007g of azodiisobutyl amidine hydrochloride and 0.00005g of 2, 2' -azo [2- (2-imidazoline-2-yl) propane]Dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water, and the solution was sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in example 5 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. An oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, the viscosity of crude oil is 1.25mPas, the product solution is injected after the water-flooding reaches the water content of more than 98 percent, and the percent of the product solution for improving the crude oil recovery rate is measured. The data records are shown in table 1 for sample # 5.

It can be seen that the viscosity of the sample obtained in example 5 in 120000mg/L saline can reach 15.6mPas, the interfacial tension is 0.018mN/m, the molecular weight is 950 ten thousand, and the recovery ratio can be improved by 10.5% after water flooding. The performance data can prove that the product effectively plays a role in expanding swept volume and improving microscopic displacement efficiency in the oil displacement process. Meanwhile, the viscosity can be maintained under the condition of 85 ℃ and 120000mg/L of mineralization degree, and the excellent temperature resistance and salt resistance of the product are also proved. Compared with examples 3 and 4, example 5 has a higher branched monomer content, thus having a lower molecular weight, a lower viscosity, a higher interfacial activity and a slightly lower recovery ratio.

[ COMPARATIVE EXAMPLE 1 ]

25g of an acrylamide monomer, 3g of 2-acrylamido-2-methylpropanesulfonic acid, 3.6g of t-butylacrylamide, 0.5g of methacryloyloxyethyl trimethyl ammonium chloride, 1.25g of a branched monomer represented by the formula (1) (wherein R is₁Is alkyl of 12 carbons, a is 6, b is 1, R₀Acrylamide group), 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of defoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to be 7.0, the solution is added into an adiabatic reactor after the temperature of the solution is adjusted to be 10 ℃, nitrogen is introduced to remove oxygen, the stirring is carried out, and the nitrogen is continuously introduced to remove the oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2, 2' -azo [2- (2-imidazolin-2-yl) propane]Dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water, and the solution was sequentially added to the reactor. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in comparative example 1 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. The oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, the injection speed is 0.5mL/min, the viscosity of crude oil is 1.25mPas, and the product solution reaches the content of oil in water floodingInjecting after the water rate is more than 98 percent, and measuring the percentage of the product solution for improving the crude oil recovery rate. The data records are shown in table 1 for sample # 6.

It can be seen that the sample obtained in comparative example 1 has a viscosity of 18.5mPaS in 120000mg/L saline, an interfacial tension of 0.17mN/m, a molecular weight of 1550 ten thousand, and can improve the recovery efficiency by 8.2% after water flooding. This is because the nonionic surfactant branched monomer was used in comparative example 1, and therefore, although the influence on the molecular weight was small, the viscosity of the product was high and the molecular weight was high, but the interfacial activity of the product was poor, and finally, the recovery efficiency was improved by less than 9%.

[ COMPARATIVE EXAMPLE 2 ]

25g of acrylamide monomer, 3g of 2-acrylamido-2-methylpropanesulfonic acid, 3.6g of tert-butylacrylamide, 0.02g of disodium ethylene diamine tetraacetate, 0.2g of urea and 0.001 part of antifoaming agent are dissolved in 100g of water to prepare a mixed aqueous solution, the pH value is adjusted to 7.0, the solution is added into an adiabatic reactor after the temperature is adjusted to 10 ℃, nitrogen is introduced to remove oxygen, stirring is carried out simultaneously, and nitrogen is continuously introduced to remove oxygen for 30 min. 0.00021g of potassium bromate, 0.00020g of sodium metabisulfite, 0.00017g of tert-butyl hydroperoxide, 0.00022g of ferrous ammonium sulfate, 0.00007g of azobisisobutylamidine hydrochloride, 0.00005g of 2,2 '-azo [2- (2-imidazolin-2-yl) propane ] dihydrochloride and 0.00005g of 4, 4' -azobis (4-cyanovaleric acid) were dissolved in 2g of deionized water and added to the reactor in succession. Nitrogen was continuously introduced and stirred. And stopping introducing the nitrogen after the viscosity of the polymerization reaction system is obviously increased and the polymerization reaction starts. When the temperature of the reaction system rises to the maximum temperature, the temperature is kept constant for 2 hours. Taking out the polymerization product, cutting into particles, drying in a 90 ℃ oven until the solid content is more than 88%, and crushing for later use.

The sample obtained in comparative example 2 was dissolved in 120000mg/L saline solution with stirring to prepare a product solution having a concentration of 2000mg/L, and the solution viscosity and shear rate were measured at 85 ℃ in a coaxial cylinder mode using a Haake rheometer^-1. The interfacial tension of the above solution with crude oil was measured using a TX500c interfacial tension meter. The molecular weight of the product was determined using an Ubbelohde viscometer. An oil displacement experiment is carried out in a sand filling pipe with the permeability of 1500mD, the temperature is 85 ℃, and the injection speed is 0.5mL/min, the crude oil viscosity is 1.25mPas, the product solution is injected after the water-flooding reaches the water content of more than 98 percent, and the percentage of the product solution for improving the crude oil recovery ratio is measured. The data records are shown in table 1 for sample # 7.

It can be seen that the viscosity of the sample obtained in comparative example 2 in 120000mg/L saline can reach 5.3mPaS, the interfacial tension can not be measured, the molecular weight is 1600 ten thousand, and the recovery ratio can be improved by 7.1% after water flooding. This is because the solution viscosity in the hypersalinity saline is only 5.3mPaS due to the lack of the hydrophobic association structure, and the interfacial tension between the product aqueous solution and the crude oil is high in the product due to the absence of the interfacial active monomer, and the data cannot be obtained by the test, so that the conventional anionic polyacrylamide in the comparative example 2 only has the effect of enlarging the swept volume but does not have the effect of obviously reducing the interfacial tension in the displacement experiment, and the recovery ratio is the lowest.

TABLE 1 Properties of the products obtained in examples and comparative examples

Numbering	1	2	3	4	5	6	7
								Viscosity mPaS	24.5	22	20.5	19.8	15.6	18.5	5.3
Interfacial tension mN/m	0.021	0.032	0.024	0.020	0.018	0.17	---
								Molecular weight of ten thousand	1050	1220	1250	1000	950	1550	1600
Recovery ratio%	13.4	12.3	12.8	11.3	10.5	8.2	7.1

Claims (10)

1. A polyacrylamide-based anion-cation composite polymer comprises an acrylamide structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, an optional nonionic interfacial activity branching structural unit shown in a formula (I) or a formula (II), a cationic interfacial activity branching structural unit shown in a formula (III) or a formula (IV), an anionic interfacial activity branching structural unit shown in a formula (V) or a formula (VI), and an optional cationic monomer structural unit:

wherein R 'is a hydrogen atom or a methyl group, and R' is-O-, -CH₂-、-CH₂O-, -COO-or-CONH-, m ═ 0 or 1, R₁Is C₁～C₂₈A hydrocarbon group of R₂Is a hydrogen atom or C₁～C₂₈N is the number of Poly(s) independently selected from

A and b are respectively 0-40 independently, and a and b are not 0 at the same time;

R₃an alkylene chain consisting of 1 to 28 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₈A hydrocarbon group of R₆Is C₁～C₂₈Is a hydrocarbon group of^-Is chloride ion, bromide ion, iodide ion;

y is a sulfonate, sulfate or carboxylate radical, R₇Is a hydrogen atom or C₁～C₂₈A hydrocarbon group of (1).

2. The polyacrylamide-based yin-yang composite polymer according to claim 1, wherein:

R₁is C₆～C₂₀A hydrocarbon group of R₂Is a hydrogen atom or C₆～C₂₀A and b are each independently 1 to 24;

R₃is composed of 8-20 methylene groupsAlkylene chain, R₄、R₅Independently of a hydrogen atom or C₁～C₂₀A hydrocarbon group of (a); r is₆Is C₆～C₂₀A hydrocarbon group of (a);

R₇is a hydrogen atom or C₆～C₂₀A hydrocarbon group of (1).

3. The polyacrylamide-based yin-yang composite polymer according to claim 1, wherein the polymer is obtained by reacting a reaction system comprising the following components in parts by weight:

4. the polyacrylamide-based yin-yang composite polymer according to claim 3, wherein:

the anionic monomer is at least one selected from acrylic acid, methacrylic acid, vinylsulfonic acid, p-vinylbenzenesulfonic acid, maleic acid, fumaric acid, vinylbenzenesulfonic acid, allylsulfonic acid, allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and alkali metal salts or ammonium salts thereof; and/or the presence of a gas in the gas,

the cationic monomer is selected from at least one of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropyl trimethyl ammonium chloride, dimethyl ethyl allyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride and methacryloyloxyethyl dimethyl benzyl ammonium chloride; and/or the presence of a gas in the gas,

the nonionic monomer is at least one selected from methacrylamide, dimethylacrylamide, diethylacrylamide, hydroxymethyl acrylamide, hydroxyethyl acrylamide, dimethylaminopropyl methacrylamide, hydroxymethyl methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, vinyl pyrrolidone and tert-butyl acrylamide.

5. The polyacrylamide-based yin-yang composite polymer according to claim 3, wherein:

the non-ionic interfacial activity branched monomer is selected from at least one branched monomer shown in formulas (1) to (4),

and/or the cationic surface active branching monomer is selected from at least one of the branching monomers shown in formulas (5) to (6),

and/or the anionic surface active branched monomer is selected from at least one branched monomer shown in formulas (7) to (12),

wherein R is₁Is C₁～C₂₈A hydrocarbon group of R₂Is a hydrogen atom or C₁～C₂₈A and b are respectively 0-40 independently, and a and b are not 0 at the same time;

R₃is an alkyl chain consisting of 1 to 28 methylene groups, R₄、R₅Independently of a hydrogen atom or C₁～C₂₈A hydrocarbon group of R₆Is C₁～C₂₈Is a hydrocarbon group of^-Is chloride ion, bromide ion, iodide ion;

R₇is a hydrogen atom or C₁～C₂₈A hydrocarbon group of (a);

R₀is selected from any one of the structures shown below,

6. the polyacrylamide-based yin-yang composite polymer according to claim 3, wherein:

the reaction system further comprises at least one of the following components in parts by weight:

7. the polyacrylamide-based yin-yang composite polymer according to claim 6, wherein:

the oxidant is at least one selected from potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, tert-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate; and/or the presence of a gas in the gas,

the reducing agent is selected from at least one of sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N-dimethylaniline, tartaric acid, ferrous sulfate, N-diethylaniline, ferrous pyrophosphate, silver nitrate, mercaptan, ferrous chloride, tetraethylene imine, glycerol and pentaerythritol; and/or the presence of a gas in the gas,

the azo initiator is selected from at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2 '-azo [2- (2-imidazoline-2-yl) propane ] dihydrochloride, azobis (2, 5-dimethyl-6-carboxyl) hexanenitrile and 4, 4' -azobis (4-cyanovaleric acid); and/or the presence of a gas in the gas,

the cosolvent is at least one selected from urea, ammonia water, sodium formate and sodium acetate; and/or the presence of a gas in the gas,

the defoaming agent is an organic silicon water-based defoaming agent; and/or the presence of a gas in the gas,

the chelating agent is at least one of ethylenediamine tetraacetic acid, disodium ethylenediamine tetraacetic acid and tetrasodium ethylenediamine tetraacetic acid.

8. A method for preparing the polyacrylamide-based anion-cation complex polymer according to any one of claims 1 to 7, comprising aqueous solution polymerization of the components comprising acrylamide, anionic monomer, nonionic monomer, anionic surfactant branched monomer, cationic surfactant branched monomer, optional nonionic surfactant branched monomer, and optional cationic monomer.

9. The method for preparing a polyacrylamide-based anion-cation composite polymer according to claim 8, which comprises the steps of:

1) dissolving a portion of the components including acrylamide, anionic monomer, nonionic monomer, anionic surface active branching monomer, cationic surface active branching monomer, optional nonionic surface active branching monomer, and optional cationic monomer in water;

2) adjusting the pH value of the solution to 6-12, and adjusting the temperature to 0-25 ℃;

3) and adding the rest components under the inert atmosphere and adiabatic conditions, carrying out polymerization reaction, and keeping the temperature for 1-8 hours to obtain the polymer after the temperature of the reaction system is raised to the maximum temperature.

10. Use of the polyacrylamide-based anion-cation complex polymer according to any one of claims 1 to 7 or the polyacrylamide-based anion-cation complex polymer obtained by the preparation method according to any one of claims 8 to 9 in an oil displacement agent.