A temperature-resistant and salt-resistant water-soluble polymer, preparation method and application

Abstract

The present invention discloses a temperature-resistant and salt-resistant water-soluble polymer, a preparation method and an application thereof. The polymer contains structural unit A, structural unit B and structural unit C; based on the weight of the polymer being 100%, the content of structural unit A is 60-85 wt%, the content of structural unit B is 10-30 wt%, and the content of structural unit C is 5-15 wt%. The polymer of the present invention is applicable as an oil displacement agent to high-temperature and high-salt type III oil reservoirs and can further improve the crude oil recovery rate in tertiary oil recovery. The polymer of the present invention has a relatively high viscosity-average molecular weight and a relatively high apparent viscosity. At the same time, the surface tension value of the aqueous solution of this polymer is between 32 mN / m and 41 mN / m, showing good surface activity. It can be used as an oil displacement agent for high-temperature and high-salt type III oil reservoirs to further improve the crude oil recovery rate in tertiary oil recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production. Further, it relates to a temperature-resistant and salt-resistant water-soluble polymer, a preparation method and an application thereof. Background Art

[0002] High molecular weight partially hydrolyzed polyacrylamide is a kind of polymer flooding agent widely used in the tertiary oil recovery in oil fields. It shows good chemical stability, high viscosity retention rate and swept volume in the first and second type of reservoirs with low temperature and low salinity, thus improving the oil recovery rate. However, for the third type of reservoirs with high temperature and high salinity, high molecular weight partially hydrolyzed polyacrylamide has poor salt tolerance, is prone to hydrolysis and serious degradation, forms complex precipitation with calcium and magnesium ions and precipitates out, and the viscosity retention rate of the solution decreases, which makes its oil displacement effect in the third type of reservoirs poor and the economic benefit not obvious. At present, for the third type of reservoirs (formation temperature 70 - 95 °C, formation salinity 10000 - 30000 mg / L), the research and development of oil displacement agents resistant to high temperature and high salinity formation conditions has become a research hotspot.

[0003] In the tertiary oil recovery technology, the ternary chemical composite flooding technology can achieve ultra-low interfacial tension between oil and water, and at the same time maintain the viscosity of the injected fluid, greatly improving the oil recovery rate. However, the performance characteristics such as adsorption, diffusion and migration of the mixture of different component chemical agents in the porous medium of the reservoir vary greatly, resulting in the "chromatographic separation effect" during oil displacement in the reservoir pores. At the same time, the loss of the surfactant during the displacement process increases, and the oil recovery rate and economic benefit decrease. In addition, when using strong base additives, serious scaling occurs in many links during the production process, bringing difficulties to production management.

[0004] To ensure that the oil displacement system has sufficiently high viscosity and ultra-low interfacial tension simultaneously under high salinity and high temperature conditions, it is necessary to break through the previous framework of using polymer / surfactant compound systems. By combining the viscosity-increasing ability of high polymers with the surface activity of low molecular surfactants, functional groups with excellent surface activity are introduced onto the polymer chain to achieve the effect of both increasing viscosity and reducing interfacial tension. One material plays the roles of both polymer and surfactant. Therefore, such surface-active polymer flooding agents will, to a certain extent, solve the chromatographic separation effect problem existing in polymer-surfactant composite flooding. At the same time, due to the viscosity-increasing performance of the surface-active functional polymer, it also has the function of stabilizing foam and can act as a foam stabilizer in foam flooding and multi-component foam composite flooding. These superior properties make it have broad application prospects in tertiary oil recovery.

[0005] The research on surface-active functional polymers has been continuously deepened, and the development of new varieties and new synthesis methods is also a current research hotspot. However, due to the insufficient understanding of the relationship between structure and properties, and the very complex macromolecular aqueous solution system involving physical and chemical properties, the research progress in the field of surface-active functional polymers has been slow so far. Therefore, studying the relationship between its structure and properties and synthesizing copolymers with high molecular weight and good surface activity have important theoretical and application values.

[0006] In Chinese Patent CN1155555A, a ternary copolymer with high molecular weight and high surface activity is generated by copolymerizing two components, carboxymethyl cellulose and surface-active macromonomer, and adding a third monomer. Its molecular weight is 2×10 4 -2×10 5 , the surface tension can reach 28 - 35 mN / m, and the interfacial tension is 0.1 - 3 mN / m. This copolymer has excellent surface and interfacial activity, and effectively overcomes the defect of immiscibility in the application of the blend solution of polymer and low-molecular surfactant, reducing the cost. However, its molecular weight is on the low side, resulting in low viscosity of the copolymer, and it cannot effectively reduce the oil-water mobility ratio and increase the swept volume to achieve the purpose of improving oil recovery.

[0007] In Chinese Patent CN105331347A, a modified PVA polyvinyl alcohol high-molecular surfactant for oil displacement is obtained by reacting water-soluble PVA and oil-soluble substances under certain conditions. The prepared product has both water solubility and partial oil solubility, thereby increasing the compatibility of the surfactant solution with crude oil. However, under harsh reservoir conditions, it does not have the ability to resist temperature and salt, nor the ability to reduce the oil saturation in the swept reservoir. Sun Lili et al. from Southwest Petroleum Institute synthesized a new type of high-molecular surfactant by homogeneous polymerization method. This high-molecular surfactant is a terpolymer of acrylamide, acrylic acid, and methyl methacrylate. The ability of this high-molecular surfactant to reduce surface tension is inferior to that of low-molecular surfactants. When it is compounded with inorganic salts, due to the synergistic effect, it will produce a compounding performance superior to that of a single surfactant, making the surface tension drop lower. However, the temperature and salt resistance performance of this high-molecular surfactant is poor. Summary of the Invention

[0008] To solve the problems in the prior art, the present invention provides a temperature- and salt-resistant water-soluble polymer, a preparation method, and an application. By introducing surface-active monomers and temperature- and salt-resistant functional groups, a surface-active functional polymer with good surface activity, the ability to thicken water media, and water solubility with high temperature and high salt resistance is obtained.

[0009] One object of the present invention is to provide a temperature- and salt-resistant water-soluble polymer.

[0010] The polymer contains structural unit A, structural unit B and structural unit C;

[0011] The structure of the structural unit A is as shown in (1);

[0012]

[0013] The structure of the structural unit B is as shown in (2);

[0014]

[0015] n is an integer from 6 to 20;

[0016] The structure of the structural unit C is as shown in (3);

[0017]

[0018] R1 is H, CH3; R2 is a C1-C 20 alkyl group.

[0019] In a preferred embodiment of the present invention,

[0020] The C1-C 20 alkyl group is straight-chain or branched-chain, and the C1-C 20 alkyl group includes: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl. More preferably: n-dodecyl, n-tetradecyl, n-hexadecyl.

[0021] In a preferred embodiment of the present invention,

[0022] Based on the weight of the polymer being 100%,

[0023] the content of the structural unit A is 60-85 wt%;

[0024] the content of the structural unit B is 10-30 wt%;

[0025] the content of the structural unit C is 5-15 wt%.

[0026] In a further preferred embodiment of the present invention,

[0027] Based on the weight of the polymer being 100%,

[0028] the content of the structural unit A is 70-85 wt%;

[0029] the content of the structural unit B is 10-20 wt%;

[0030] The content of structural unit C is 5-10 wt%.

[0031] In a preferred embodiment of the present invention,

[0032] The viscosity-average molecular weight of the polymer is 8 million - 15 million, preferably 10 million - 15 million;

[0033] The intrinsic viscosity η of the polymer is 1600-2650 mL / g, preferably 1900-2650 mL / g;

[0034] When the concentration of the polymer solution is 1500 mg / L, its surface tension is 32-41 mN / m, preferably 32-35.5 mN / m.

[0035] In a preferred embodiment of the present invention,

[0036] The structure of structural unit B is shown in formula (4), formula (5) or formula (6):

[0037]

[0038] The structure of the said structural unit C is shown in (7), (8) or (9);

[0039]

[0040] The second object of the present invention is to provide a preparation method of a temperature-resistant and salt-resistant water-soluble polymer.

[0041] The said method includes:

[0042] Monomer D, monomer E and monomer F carry out a solution polymerization reaction in the presence of an initiator to obtain the said polymer;

[0043] The said monomer D is acrylamide;

[0044] The structure of the said monomer E is shown in (10);

[0045]

[0046] n is an integer of 6-20;

[0047] The structure of the said monomer F is shown in (11);

[0048]

[0049] R1 is H, CH3; R2 is C1-C 20 alkyl;

[0050] The said C1-C 20The alkyl group is straight-chain or branched-chain, and the C1-C 20 The alkyl groups include: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl; more preferably: n-dodecyl, n-tetradecyl, n-hexadecyl.

[0051] Based on the total weight of the monomers being 100%, the content of monomer D is 60 - 85 wt%, the content of monomer E is 10 - 30 wt%, and the content of monomer F is 5 - 15 wt%; preferably: the content of monomer D is 70 - 85 wt%, the content of monomer E is 10 - 20 wt%, and the content of monomer F is 5 - 10 wt%.

[0052] Based on the total weight of the solvent and monomers being 100%, the content of the sum of monomer D, monomer E, and monomer F is 10 - 30 wt%, preferably 20 - 30 wt%.

[0053] The solvent is preferably water;

[0054] In a preferred embodiment of the present invention,

[0055] The polymerization temperature is 0 - 25 °C, preferably 0 - 15 °C;

[0056] The polymerization time is 2 - 15 hours, preferably 10 - 15 hours.

[0057] In a preferred embodiment of the present invention,

[0058] The polymerization reaction is carried out in the presence of a protective gas;

[0059] The protective gas is a gas that does not react with the raw materials and products; preferably nitrogen or argon.

[0060] In a preferred embodiment of the present invention,

[0061] The structural formula of monomer E is:

[0062]

[0063] The structural formula of monomer F is;

[0064]

[0065] In a preferred embodiment of the present invention,

[0066] The initiator is any two of azo initiators, peroxide initiators, and redox initiators;

[0067] The dosage of the initiator is 0.01 - 0.1 wt% of the total weight of the monomers.

[0068] In a preferred embodiment of the present invention,

[0069] The polymerization reaction is carried out under the conditions of a pH value of 7 - 10, preferably 7 - 9; the pH value is adjusted by adding a pH regulator to the polymerization system;

[0070] The pH regulator is at least one of sodium hydroxide, sodium carbonate, potassium carbonate, and ammonia water.

[0071] In a preferred embodiment of the present invention,

[0072] The polymerization reaction is carried out in the presence of a chelating agent;

[0073] The chelating agent is at least one of disodium ethylenediaminetetraacetate, nitrilotriacetic acid, and ammonium citrate;

[0074] The dosage of the chelating agent is 0.1 - 0.3 wt% of the total weight of the monomers.

[0075] In a preferred embodiment of the present invention,

[0076] The polymerization reaction is carried out in the presence of an auxiliary agent;

[0077] The auxiliary agent is at least one of urea, thiourea, and ammonia water;

[0078] The dosage of the auxiliary agent is 0.01 - 0.1 wt% of the total weight of the monomers.

[0079] In a preferred embodiment of the present invention,

[0080] The polymerization reaction is carried out in the presence of a molecular weight regulator;

[0081] The molecular weight regulator is at least one of isopropyl alcohol, ammonia water, N,N'-methylenebisacrylamide, and dimethylthiourea;

[0082] The dosage of the molecular weight regulator is 0.02 - 0.05 wt% of the total weight of the monomers.

[0083] In the present invention, the total weight of the monomers is the sum of the weights of monomer D, monomer E, and monomer F.

[0084] The third object of the present invention is to provide an application of a temperature-resistant and salt-resistant water-soluble polymer in tertiary oil recovery.

[0085] In the present invention, the intrinsic viscosity is measured according to the method for measuring the intrinsic viscosity of polyacrylamide specified in GB12005.1-89, and a 10 wt% NaCl solution is measured at 25 °C using an Ubbelohde viscometer. The surface tension is measured using a Dataphysics DCAT21 surface tensiometer.

[0086] In the research of the inventors of the present invention, it was found that a polymer composed of specific structural units A, B, and C can achieve a good oil displacement effect when used as an oil displacement agent. For example, the structural unit A is a unit having the structure shown in formula (1), the structural unit B can be one of the units having the structures shown in formula (4), formula (5), or formula (6), and the structural unit C can be one of the units having the structures shown in formula (7), (8), and (9).

[0087]

[0088] The method for preparing the polymer of the present invention is to carry out a polymerization reaction of a monomer mixture in water in the presence of an initiator and a solvent under solution polymerization reaction conditions. The monomer mixture contains monomer D, monomer E, and monomer F; monomer D is acrylamide, monomer E is a monomer having the structure shown in formula (10), and monomer F is a monomer having the structure shown in formula (11); and based on the total amount of the monomer mixture, the content of monomer D is 60-85 wt%, the content of monomer E is 10-30 wt%, and the content of monomer F is 5-15 wt%; the conditions of the polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained after the polymerization reaction is 8 million - 15 million.

[0089] In the research of the inventors of the present invention, it was found that a polymer obtained by reacting specific monomers D, E, and F can achieve a good oil displacement effect when used as an oil displacement agent. For example, monomer D is acrylamide, monomer E can be at least one of the monomers having the structures shown in formula (12), formula (13), and formula (14), and monomer F can be at least one of the monomers having the structures shown in formula (15), formula (16), and formula (17).

[0090]

[0091] According to the method of the present invention, the polymerization reaction is carried out in the presence of an inert gas. The polymerization reaction conditions include: the polymerization temperature is 0-25 °C, preferably 0-15 °C; the polymerization time is 2-15 hours, preferably 10-15 hours. The inert gas is a gas that does not react with the raw materials and products, and can be at least one of nitrogen gas or the gases of Group 0 elements in the periodic table that are conventional in the art, preferably nitrogen gas.

[0092] According to the method of the present invention, the polymerization reaction is preferably carried out under the condition that the pH value is 7-10, more preferably 7-9. The above pH value can be obtained by adding a pH regulator to the polymerization system. The pH regulator used to adjust the pH value can be various pH regulators commonly used in the art, for example, it can be at least one of sodium hydroxide, sodium carbonate, potassium carbonate, and ammonia water, and preferably sodium hydroxide.

[0093] According to the method of the present invention, the initiator can be various initiators commonly used in the art. For example, it can be selected from any two of the free radical polymerization initiators; the free radical polymerization initiators include azo initiators, peroxide initiators, and redox initiators; the azo initiators are selected from at least one of dimethyl azobisisobutyrate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, azodicarbonamide, 2,2'-azobis(2-isopropylimidazoline) hydrochloride, azoisobutyronitrile formamide, azodicyclohexylcarbonitrile, azodicyanovaleric acid, 2,2'-azobis(2-isopropylimidazoline), azobisisobutyronitrile, azodisovaleronitrile, and azodiisooctanenitrile; the peroxide initiators are selected from at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide, and tert-butyl peroxybenzoate; the redox initiators are selected from at least one of sulfate-sulfite, persulfate-thiourea, persulfate-organic salt, and ammonium persulfate-fatty amine.

[0094] According to the method of the present invention, adding a chelating agent can prevent the influence of metal ions on the polymerization reaction. Therefore, preferably, the polymerization reaction is carried out in the presence of a chelating agent. The chelating agent can be disodium ethylenediaminetetraacetate, nitrilotriacetic acid, or ammonium citrate, and preferably disodium ethylenediaminetetraacetate.

[0095] According to the method of the present invention, adding an auxiliary agent can improve the solubility of the copolymer. Therefore, preferably, the polymerization reaction is carried out in the presence of an auxiliary agent. The auxiliary agent can be substances such as urea, thiourea, and ammonia water, and preferably urea.

[0096] According to the method of the present invention, adding a molecular weight regulator can synthesize polymers with different molecular weights. Therefore, preferably, the polymerization reaction is carried out in the presence of a molecular weight regulator. The molecular weight regulator can be at least one of isopropyl alcohol, ammonia water, N,N'-methylenebisacrylamide, and dimethylthiourea.

[0097] Preferably, the method of the present invention further includes purifying and drying the polymer mixture obtained by polymerization to obtain a purified polymer. The purification is preferably carried out by precipitation purification using acetone.

[0098] The present invention also provides a polymer with surface activity function prepared by the above method.

[0099] From the perspective of molecular design, the present invention introduces surface-active functional monomers E and F into the macromolecular structure of polyacrylamide. On the one hand, it provides the surface activity of the polymer, and on the other hand, it improves the temperature and salt resistance of the polymer product. The active carbon-carbon double bonds in the molecular structures of monomers E and F endow them with high reactivity and can easily copolymerize with various other olefin monomers to form different functional polymers. The polyether structure in the molecular structure of monomer E gives it good hydrophilicity and surface activity, and at the same time, it is resistant to acid, alkali, and hard water. The molecular structure of monomer F contains a long-side-chain alkyl group, a strong anionic and hydrophilic functional group sulfonic acid group, which has good surface activity, excellent anti-cation precipitation performance, and temperature resistance. The surface-active functional polymer described in the present invention combines the thickening property of macromolecules and the surface activity of low-molecular surfactants, and has the advantages of easy mobility control and reduction of oil / water interfacial tension, etc., and can solve problems such as chromatographic separation effects existing in polymer-surfactant composite flooding.

[0100] The polymer of the present invention has a relatively high viscosity-average molecular weight, which can reach more than 8 million; when the temperature rises to 80 °C, it still has a relatively high apparent viscosity, and at the same time, the surface tension value of the polymer aqueous solution is between 32 mN / m - 41 mN / m, showing good surface activity. It shows that the polymer of the present invention can effectively solve the problems of poor temperature resistance and resistance to inorganic high-valent cations of the existing oil displacement system, and can be used as an oil displacement agent for high-temperature and high-salt type III oil reservoirs to further improve the oil recovery rate in tertiary oil recovery. Specific embodiments

[0101] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0102] The test methods related to the present invention are as follows:

[0103] The dissolution time of the polymer is determined according to the method specified in GB12005.8 - 89.

[0104] The intrinsic viscosity η of the polymer is determined according to the method for determining the intrinsic viscosity of polyacrylamide specified in GB12005.1 - 89, and a 10 wt% NaCl solution is measured at 25 °C using an Ubbelohde viscometer.

[0105] The viscosity-average molecular weight is calculated according to the formula M = (η / K) 1\α where K = 4.5×10 -3 and α = 0.80.

[0106] The apparent viscosity of the polymer solution was measured using a Brookfield DV-III viscometer at a constant shear rate of 7.34 s -1 .

[0107] The surface tension was measured according to the method specified in GB / T 22237-2008 using a Dataphysics DCAT21 surface tensiometer.

[0108] The solid content was determined according to the method specified in GB12005.2-89.

[0109] The molecular structural formula and the composition of the structural units were determined by quantitative 13 C spectroscopy.

[0110] All the reagents used in the examples were commercially available chemically pure reagents;

[0111] The polymer sample KYP used in the comparative example was an in-use sample provided by the oilfield. KYP contains acrylamide structural units and 2-methyl-2-acrylamidopropanesulfonic acid structural units. Based on the weight of KYP, the content of acrylamide structural units is 75 wt%, the content of 2-methyl-2-acrylamidopropanesulfonic acid structural units is 25 wt%, the viscosity-average molecular weight of KYP is 10.1 million, and the intrinsic viscosity is 1915 mL / g.

[0112] Monomer F1 was prepared according to the method in the literature Fine Chemicals, 2006, 23(3): 234-237, and its structure is shown in formula (15):

[0113]

[0114] Monomer F2 was prepared according to the method in the literature Fine Chemicals, 2006, 23(3): 234-237, and its structure is shown in formula (16):

[0115]

[0116] Monomer F3 was prepared according to the method in the literature Fine Chemicals, 2006, 23(3): 234-237, and its structure is shown in formula (17):

[0117]

[0118] Example 1

[0119] Using the aqueous solution polymerization method, 22.5 g of monomer F1 as a water-soluble surface active monomer, 90.0 g of acrylamide, and 37.5 g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25(OCH2CH2)6OOCCH=CHCH3) and distilled water. Based on the total content of the monomer and distilled water, the total content of the monomer is 10 wt%, and it is fully stirred until the solution in the polymerization reaction flask becomes a transparent solution. Then, 60 mg of the auxiliary agent urea, 200 mg of disodium ethylenediaminetetraacetate, 3 mL of ammonia water, and 80 mg of isopropanol are added. At the same time, the pH value of the system is adjusted to 10.0 with sodium hydroxide, the initial temperature of the system is controlled at 25 °C, and high-purity nitrogen with a volume concentration of 99.99% is introduced for 30 minutes to remove the oxygen in the polymerization reaction flask. Then, 50 mg of ammonium persulfate and 25 mg of sodium bisulfite are added in sequence, and high-purity nitrogen is continuously introduced for 10 minutes. The reactor is sealed and reacted for 2 hours to obtain a transparent polymer with viscosity. The colloidal product is taken out, and through granulation, drying, crushing, and screening, a high-molecular-weight surface-active functional polymer product P1 can be obtained.

[0120] Perform performance measurement on the polymer P1: Quantitatively 13 In the 13C spectrum, characteristic peaks of C=O, C-O-C, -CH2-SO3, and -CH2-CH3 bonds in formula (18) appear at 165.69 ppm, 72.33 ppm, 63.75 ppm, and 29.75 ppm respectively. At the same time, the C characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed, and it can be determined that the copolymer molecule obtained has the structure shown in formula (18). Through the integral area of the characteristic peaks, x1:y1:z1 can be calculated to be 1:0.04:0.025. The intrinsic viscosity of polymer P1 is 1602 mL / g, and the viscosity-average molecular weight is 808×10 - ⁴. When the concentration of the polymer solution is 1500 mg / L, the surface tension is 32.2 mN / m. Polymer solutions are prepared respectively with simulated formation waters with oilfield salinities of 5000 mg / L, 15000 mg / L, and 25000 mg / L. Under the conditions that the concentration of the polymer solution is 1500 mg / L and the shear rate is 7.34 s 4 ⁻¹, the apparent viscosities of polymer P1 solution at different temperatures and salinities are shown in Table 1. Here, the salinity mentioned refers to the total content of inorganic ions such as Na -1 ⁺, K + ⁺, Ca + ²⁺, Mg 2+ ²⁺, Cl 2+ ⁻, SO4 - ²⁻, CO3 2- ²⁻, etc. in the simulated formation water. 2-

[0121]

[0122] Example 2

[0123] Using aqueous solution polymerization method, 30.0g of monomer F1 as a water-soluble surfactant monomer, 210.0g of acrylamide, 60.0g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water, based on the total content of monomers and distilled water, the total content of monomers is 20wt%, and the solution in the polymerization reaction bottle is fully stirred until it becomes a transparent solution. Then add 100mg of auxiliary urea, 360mg of disodium ethylenediaminetetraacetate, 5mL of ammonia water and 150mg of isopropanol, and adjust the pH value of the system to 9.0 with sodium hydroxide at the same time. The initial temperature of the system is controlled to be 15°C, and high-purity nitrogen with a volume concentration of 99.99% is introduced for 30 minutes to remove oxygen in the polymerization reaction bottle. Then add 100mg of ammonium persulfate and 50mg of sodium bisulfite in sequence, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, react for 10 hours, and obtain a transparent and viscous polymer. Take out the colloidal product, and obtain a high molecular weight surface active functional polymer product P2 through granulation, drying, crushing and screening.

[0124] Determination of the properties of polymer P2: Quantitative 13 In the C spectrum, C=O, COC, -CH2-SO3 in formula (19) appeared at 165.69ppm, 72.33ppm, 63.75ppm, and 29.75ppm, respectively. - The characteristic peaks of -CH2-CH3 bonds and the characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed. It can be determined that the copolymer molecule has the structure shown in formula (19). The integral area of ​​the characteristic peaks can be used to calculate that x1:y1:z1 is 1:0.03:0.022. The intrinsic viscosity of polymer P2 is 1902 mL / g, and the viscosity-average molecular weight is 1006×10 4 When the concentration of the polymer solution is 1500 mg / L, the surface tension is 31.9 mN / m. The polymer solutions were prepared with simulated formation water with oilfield salinity of 5000 mg / L, 15000 mg / L and 25000 mg / L, respectively. When the concentration of the polymer solution is 1500 mg / L and the shear rate is 7.34 s -1 Under the condition of , the apparent viscosity of polymer P2 solution at different temperatures and salinities is shown in Table 1. The salinity here refers to the Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- 、CO3 2- The sum of the inorganic ion contents.

[0125] Example 3

[0126] Using aqueous solution polymerization method, 18.75g of monomer F1 as a water-soluble surfactant monomer, 281.25g of acrylamide, 75.0g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water, based on the total content of monomer and distilled water, the total content of monomer is 25wt%, and the solution in the polymerization reaction bottle becomes a transparent solution. Then add 120mg auxiliary urea, 400mg disodium ethylenediaminetetraacetate, 5mL ammonia water and 120mg isopropanol, and adjust the pH value of the system to 8.0 with sodium hydroxide, control the initial temperature of the system to 8°C, and pass high-purity nitrogen with a volume concentration of 99.99% for 30 minutes to remove oxygen in the polymerization reaction bottle. Then add 60mg ammonium persulfate and 30mg sodium bisulfite in sequence, continue to pass high-purity nitrogen for 10 minutes, seal the reactor, react for 12 hours, obtain a transparent and viscous polymer, take out the colloidal product, and obtain a high molecular weight surface active functional polymer product P3 through granulation, drying, crushing and screening.

[0127] Performance determination of polymer P3: quantitative 13 In the C spectrum, C=O, COC, -CH2-SO3 in formula (19) appeared at 165.69ppm, 72.33ppm, 63.75ppm, and 29.75ppm, respectively. - , -CH2-CH3 bonds, and the characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed. It can be determined that the copolymer molecule has the structure shown in formula (19). The integral area of ​​the characteristic peaks can be used to calculate that x1:y1:z1 is 1:0.04:0.02. The characteristic viscosity of polymer P3 is 2123mL / g, the viscosity-average molecular weight is 1155×104, and the surface tension is 33.7mN / m when the concentration of the polymer solution is 1500mg / L. The polymer solutions were prepared using simulated formation water with oilfield mineralization of 5000mg / L, 15000mg / L and 25000mg / L, respectively. When the polymer solution concentration was 1500mg / L and the shear rate was 7.34s -1 The apparent viscosity of polymer P3 solution at different temperatures and salinities is shown in Table 1. The salinity here refers to the Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- 、CO32- The total content of inorganic ions such as

[0128]

[0129] Example 4

[0130] Using the aqueous solution polymerization method, add 18.75 g of monomer F2 as a water-soluble surface active monomer, 262.5 g of acrylamide, 93.75 g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water into the polymerization reaction flask. Based on the total content of the monomer and distilled water, the total content of the monomer is 25 wt%. Stir well until the solution in the polymerization reaction flask becomes a transparent solution. Then add 100 mg of the auxiliary agent urea, 300 mg of disodium ethylenediaminetetraacetate, 10 mL of ammonia water, and 150 mg of isopropanol. At the same time, adjust the pH value of the system to 7.0 with sodium hydroxide, control the initial temperature of the system at 5 °C, and introduce high-purity nitrogen with a volume concentration of 99.99% for 30 minutes to remove the oxygen in the polymerization reaction flask. Then add 100 mg of ammonium persulfate and 50 mg of sodium bisulfite in sequence, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, and react for 12 hours to obtain a transparent polymer with viscosity. Take out the colloidal product, and through granulation, drying, crushing, and screening, the high-molecular-weight surface active functional polymer product P4 can be obtained.

[0131] Perform performance measurement on polymer P4: Quantitatively 13 In the 13C spectrum, characteristic peaks of C=O, C-O-C, -CH2-SO3 - , -CH2-CH3 bonds in formula (20) appear at 165.69 ppm, 72.33 ppm, 63.75 ppm, and 29.75 ppm respectively. At the same time, the C characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed, and it can be determined that the copolymer molecule obtained has the structure shown in formula (20). Through the integral area of the characteristic peaks, x1:y1:z1 can be calculated as 1:0.035:0.02. The intrinsic viscosity of polymer P4 is 2227 mL / g, and the viscosity-average molecular weight is 1225×10 4 . When the concentration of the polymer solution is 1500 mg / L, the surface tension is 32.5 mN / m. Prepare polymer solutions with simulated formation waters with oilfield salinities of 5000 mg / L, 15000 mg / L, and 25000 mg / L respectively. At a polymer solution concentration of 1500 mg / L and a shear rate of 7.34 s -1 , the apparent viscosities of polymer P4 solutions at different temperatures and salinities are shown in Table 1. Here, the salinity mentioned is the Na + 、K+ , Ca 2+ , Mg 2+ , Cl - , SO4 2- , CO3 2- The total content of inorganic ions such as etc.

[0132] Example 5

[0133] Using the aqueous solution polymerization method, add 18.75 g of monomer F2 as a water-soluble surfactant monomer, 300.0 g of acrylamide, 56.25 g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water to the polymerization reaction flask. Based on the total content of the monomer and distilled water, the total content of the monomer is 25 wt%, and stir well until the solution in the polymerization reaction flask becomes a transparent solution. Then add 150 mg of the auxiliary agent urea, 400 mg of disodium ethylenediaminetetraacetate, 5 mL of ammonia water, and 150 mg of isopropanol. At the same time, adjust the pH value of the system to 8.0 with sodium hydroxide, control the initial temperature of the system to be 2 °C, and introduce high-purity nitrogen with a volume concentration of 99.99% for 30 minutes to remove the oxygen in the polymerization reaction flask. Then add 60 mg of ammonium persulfate and 30 mg of sodium bisulfite in sequence, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, and react for 12 hours to obtain a transparent polymer with viscosity. Take out the colloidal product, and through granulation, drying, pulverization, and screening, the high-molecular-weight surfactant-functional polymer product P5 can be obtained.

[0134] Perform performance measurement on polymer P5: Quantitatively 13 In the 13C spectrum, characteristic peaks of C=O, C-O-C, -CH2-SO3 - , -CH2-CH3 bonds in formula (20) appear at 165.69 ppm, 72.33 ppm, 63.75 ppm, and 29.75 ppm respectively. At the same time, the C characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed, and it can be determined that the copolymer molecule obtained has the structure shown in formula (20). Through the integral area of the characteristic peaks, x1:y1:z1 can be calculated to be 1:0.02:0.015. The intrinsic viscosity of polymer P5 is 2440 mL / g, and the viscosity-average molecular weight is 1377×10 4 . When the concentration of the polymer solution is 1500 mg / L, the surface tension is 34.8 mN / m. Prepare polymer solutions with simulated formation water with oilfield salinities of 5000 mg / L, 15000 mg / L, and 25000 mg / L respectively. When the concentration of the polymer solution is 1500 mg / L and the shear rate is 7.34 s -1Under the conditions, the apparent viscosities of the polymer P5 solution at different temperatures and salinities are shown in Table 1. The salinity mentioned here is the sum of the contents of inorganic ions such as Na + 、K + 、Ca 2+ 、Mg 2+ 、Cl - 、SO4 2- 、CO3 2- in the simulated formation water.

[0135]

[0136] Example 6

[0137] Using the aqueous solution polymerization method, add 37.5 g of monomer F3 as a water-soluble surfactant monomer, 281.25 g of acrylamide, 56.25 g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water to the polymerization reaction flask. Based on the total content of the monomer and distilled water, the total content of the monomer is 25 wt%, and stir well until the solution in the polymerization reaction flask becomes a transparent solution. Then add 120 mg of the auxiliary agent urea, 360 mg of disodium ethylenediaminetetraacetate, 5 mL of ammonia water and 150 mg of isopropanol. At the same time, adjust the pH value of the system to 7.0 with sodium hydroxide, control the initial temperature of the system at 5 °C, and introduce high-purity nitrogen with a volume concentration of 99.99% for 30 minutes to remove the oxygen in the polymerization reaction flask. Then add 100 mg of ammonium persulfate and 50 mg of sodium bisulfite in sequence, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, and react for 15 hours to obtain a transparent polymer with viscosity. Take out the colloidal product, and through granulation, drying, crushing, and screening, a high-molecular-weight surfactant-functional polymer product P6 can be obtained.

[0138] Perform performance measurement on the polymer P6: Quantitatively 13 In the 13C spectrum, characteristic peaks of C=O, C-O-C, -CH2-SO3 - , -CH2-CH3 bonds in formula (21) appear at 165.69 ppm, 72.33 ppm, 63.75 ppm, and 29.75 ppm respectively. At the same time, the C characteristic peaks of -CH-CH2- and C=O on the main chain are superimposed, and it can be determined that the copolymer molecule obtained has the structure shown in formula (21). Through the integral area of the characteristic peaks, x1:y1:z1 can be calculated to be 1:0.02:0.026. The intrinsic viscosity of the polymer P6 is 2492 mL / g, and the viscosity-average molecular weight is 1411×10 4When the concentration of the polymer solution is 1500 mg / L, the surface tension is 33.3 mN / m. The polymer solutions were prepared with simulated formation water with oilfield salinity of 5000 mg / L, 15000 mg / L and 25000 mg / L, respectively. When the concentration of the polymer solution is 1500 mg / L and the shear rate is 7.34 s -1 Under the condition of , the apparent viscosity of polymer P6 solution at different temperatures and salinity is shown in Table 1. The salinity here refers to the Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- 、CO3 2- The sum of the inorganic ion contents.

[0139] Example 7

[0140] Using aqueous solution polymerization method, 37.5g of monomer F3 as a water-soluble surfactant monomer, 300.0g of acrylamide, 37.5g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 16 OOCCH=CHCH3) and distilled water, based on the total content of monomers and distilled water, the total content of monomers is 25wt%, and the solution in the polymerization reaction bottle is fully stirred until it becomes a transparent solution. Then add 120mg of auxiliary urea, 480mg of disodium ethylenediaminetetraacetate, 5mL of ammonia water and 150mg of isopropanol, and adjust the pH value of the system to 8.0 with sodium hydroxide at the same time. The initial temperature of the system is controlled to be 0°C, and high-purity nitrogen with a volume concentration of 99.99% is introduced for 30 minutes to remove oxygen in the polymerization reaction bottle. Then add 100mg of ammonium persulfate and 50mg of sodium bisulfite in sequence, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, react for 15 hours, and obtain a transparent and viscous polymer. Take out the colloidal product, and obtain a high molecular weight surface active functional polymer product P7 through granulation, drying, crushing and screening.

[0141] Performance determination of polymer P7: quantitative 13 In the C spectrum, C=O, COC, -CH2-SO3 in formula (21) appeared at 165.69ppm, 72.33ppm, 63.75ppm, and 29.75ppm, respectively. -The characteristic peaks of -CH2-CH3 bonds and -CH-CH2- and C=O on the main chain are superimposed, and it can be determined that the copolymer molecule has the structure shown in formula (21). The integral area of ​​the characteristic peaks can be used to calculate that x1:y1:z1 is 1:0.015:0.025. The intrinsic viscosity of polymer P7 is 2648 mL / g, and the viscosity-average molecular weight is 1499×10 4 When the concentration of the polymer solution is 1500 mg / L, the surface tension is 35.5 mN / m. The polymer solutions were prepared with simulated formation water with oilfield salinity of 5000 mg / L, 15000 mg / L and 25000 mg / L, respectively. When the concentration of the polymer solution is 1500 mg / L and the shear rate is 7.34 s -1 Under the condition of , the apparent viscosity of polymer P7 solution at different temperatures and salinity is shown in Table 1. The salinity here refers to the Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- 、CO3 2- The sum of the inorganic ion contents.

[0142]

[0143] Example 8

[0144] Using aqueous solution polymerization method, 22.5g of monomer F3 as a water-soluble surfactant monomer, 382.5g of acrylamide, 45.0g of dodecyl alcohol polyoxyethylene ether methacrylate (C 12 H 25 (OCH2CH2) 20 OOCCH=CHCH3) and distilled water, based on the total content of monomer and distilled water, the total content of monomer is 30wt%, and the solution in the polymerization reaction bottle becomes a transparent solution. Then add 120mg auxiliary urea, 480mg disodium ethylenediaminetetraacetate, 5mL ammonia water and 150mg isopropanol, and adjust the pH value of the system to 8.0 with sodium hydroxide at the same time. The initial temperature of the system is controlled to be 0°C, and high-purity nitrogen with a volume concentration of 99.99% is introduced for 30 minutes to remove oxygen in the polymerization reaction bottle. Then add 60mg ammonium persulfate and 30mg sodium bisulfite in turn, continue to introduce high-purity nitrogen for 10 minutes, seal the reactor, react for 15 hours, and obtain a transparent and viscous polymer. Take out the colloidal product, and obtain a high molecular weight surface active functional polymer product P8 through granulation, drying, crushing and screening.

[0145] Performance determination of polymer P8: quantitative 13In the C spectrum, characteristic peaks of C=O, C-O-C, -CH2-SO3, and -CH2-CH3 bonds in formula (22) appeared at 165.69 ppm, 72.33 ppm, 63.75 ppm, and 29.75 ppm respectively. At the same time, the C characteristic peaks of -CH-CH2- and C=O on the main chain overlapped, indicating that the obtained copolymer molecule had the structure shown in formula (22). The ratio of x1:y1:z1 was calculated to be 1:0.016:0.013 through the integral area of the characteristic peaks. The intrinsic viscosity of polymer P8 was 2659 mL / g, and the viscosity-average molecular weight was 1507×10 - , when the polymer solution concentration was 1500 mg / L, the surface tension was 40.1 mN / m. Polymer solutions were prepared with simulated formation water with oilfield salinity of 5000 mg / L, 15000 mg / L, and 25000 mg / L respectively. At a polymer solution concentration of 1500 mg / L and a shear rate of 7.34 s 4 , the apparent viscosities of polymer P8 solution at different temperatures and salinities are shown in Table 1. Here, the salinity refers to the total content of inorganic ions such as Na -1 , K + , Ca + , Mg 2+ , Cl 2+ , SO4 - , and CO3 2- . 2-

[0146]

[0147] Comparative Example 1

[0148] The performance of the comparative sample KYP (provided by the oilfield) was compared with the product obtained in the example. The results are shown in Table 1. The apparent viscosities of the polymer aqueous solution at different temperatures and salinities are given in Table 1. The apparent viscosities at 25 °C and 80 °C at different salinities are shown when the polymer aqueous solution concentration is 1500 mg / L.

[0149] Table 1 Apparent Viscosities of Surface-Active Functional Polymers at Different Temperatures and Salinities

[0150]

[0151] Note: Polymer aqueous solution concentration 1500 mg / L, shear rate 7.34 s -1 .

[0152] As can be seen from Table 1, the aqueous solution of acrylamide polymer with the code KYP provided by the oilfield has a relatively high apparent viscosity at low temperature and low salinity. However, as the temperature and salinity increase, the apparent viscosity decreases significantly. The polymer according to the present invention has a relatively high apparent viscosity at low temperature. When the temperature rises to 80 °C and the salinity is 15,000 mg / L, the apparent viscosity of the polymer aqueous solution can reach 10.6 - 20.6 mPa·s. When the salinity is 25,000 mg / L, it still has a relatively high apparent viscosity, and the apparent viscosity of the polymer aqueous solution can reach 9.0 - 16.5 mPa·s, indicating that the polymer of the present invention has good temperature and salt resistance performance.

[0153] Comparative Example 2

[0154] The performance of the comparative sample KYP (provided by the oilfield) was compared with the product obtained in the examples. The surface tension of polymer aqueous solutions with different concentrations prepared with simulated formation water with a salinity of 15,000 mg / L was observed at 25 °C. The results are shown in Table 2.

[0155] Table 2 Surface tension of surfactant-functional polymer aqueous solutions at different concentrations

[0156] 100 mg / L 500 mg / L 1000 mg / L 1500 mg / L 2000 mg / L 2500 mg / L Example 1 64.0 55.7 44.3 32.2 31.9 31.3 Example 2 63.6 55.3 44.2 31.9 31.5 31.0 Example 3 64.9 54.6 45.0 33.7 32.9 32.3 Example 4 63.7 53.0 42.8 32.5 31.6 31.7 Example 5 65.3 55.1 45.6 34.8 34.3 33.6 Example 6 64.2 54.5 44.8 33.3 32.6 32.5 Example 7 65.3 57.2 45.8 35.5 34.9 34.3 Example 8 66.6 58.9 47.3 37.3 40.1 38.9 KYP 68.9 67.3 65.1 62.9 63.1 63.3

[0157] Note: Polymer aqueous solutions with different concentrations were prepared with brine with a salinity of 15,000 mg / L, and their surface tension was measured at 25 °C.

[0158] As can be seen from Table 2, with the increase in concentration, the surface tension of the polymer aqueous solution according to the present invention gradually decreases. When the concentration is 1,500 mg / L, the surface tension of the polymer aqueous solution is between 31.9 - 37.3 mN / m, showing good surface activity. For the aqueous solution of the comparative sample KYP, the decrease in surface tension with the increase in concentration is very small, between 60 - 70 mN / m. When the concentration of the KYP aqueous solution is 1,500 mg / L, its surface tension is 62.9 mN / m, showing poor surface activity.

[0159] In Table 2, compared with the in-use sample KYP in the oilfield, the aqueous solutions of the samples in the present invention show excellent surface activity at different concentrations. The excellent surface activity enables the polymer to reduce the oil-water interfacial tension, thereby achieving oil-water separation and better improving the oil displacement effect.

[0160] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0161] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination manners.

[0162] Furthermore, any combinations can be made among the various different embodiments of the present invention, as long as they do not violate the idea of the present invention, and they should equally be regarded as the content disclosed by the present invention.

Claims

1. A temperature-resistant and salt-resistant water-soluble polymer, characterized in that: The polymer contains structural unit A, structural unit B and structural unit C; the structure of structural unit A is shown in (1); The structure of structural unit B is shown in (2); n is an integer from 6 to 20; The structure of structural unit C is shown in (3); R1 is H, CH3; R2 is an alkyl group having 1 to 20 C Based on 100% by weight of the polymer, The content of structural unit A is 60 - 85 wt%, The content of structural unit B is 10 - 30 wt%, The content of structural unit C is 5 - 15 wt%; The viscosity-average molecular weight of the polymer is 8 million - 15 million; The intrinsic viscosity η of the polymer is 1600 - 2650 mL / g; When the polymer solution concentration is 1500 mg / L, its surface tension is 32 - 41 mN / m.

2. The temperature-resistant and salt-resistant water-soluble polymer according to claim 1, characterized in that: The C1-C 20 alkyl group is straight-chain or branched-chain, and the C1-C 20 alkyl group includes: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl.

3. The temperature-resistant and salt-resistant water-soluble polymer according to claim 1, characterized in that: Based on 100% by weight of the polymer, The content of structural unit A is 70 - 85 wt%; The content of structural unit B is 10 - 20 wt%; The content of structural unit C is 5 - 10 wt%.

4. The temperature-resistant and salt-resistant water-soluble polymer according to claim 1, wherein: The viscosity-average molecular weight of the polymer is 10 million - 15 million; The intrinsic viscosity η of the polymer is 1900 - 2650 mL / g; When the polymer solution concentration is 1500 mg / L, its surface tension is 32 - 35.5 mN / m.

5. The temperature-resistant and salt-resistant water-soluble polymer according to claim 1, wherein: The structure of the structural unit B is as shown in Formula (4), Formula (5) or Formula (6): The structure of structural unit C is shown in (7), (8) or (9); 6. A method for preparing a polymer according to any one of claims 1 to 5, characterized in that The method includes: Monomer D, monomer E and monomer F carry out solution polymerization reaction in the presence of an initiator to obtain the polymer; Monomer D is acrylamide; The structure of monomer E is shown in (10); n is an integer from 6 to 20; The structure of monomer F is shown in (11); R1 is H, CH3; R2 is an alkyl group having 1 to 20 C The C1-C 20 alkyl group is straight-chain or branched-chain, and the C1-C 20 alkyl group includes: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl; Based on 100% by weight of the total monomers, the content of monomer D is 60 - 85 wt%, the content of monomer E is 10 - 30 wt%, and the content of monomer F is 5 - 15 wt%; Based on 100% by weight of the total weight of the solvent and monomers, the content of the sum of monomer D, monomer E and monomer F is 10 - 30 wt%.

7. The preparation method according to claim 6, characterized in that: Based on 100% by weight of the total monomers, the content of monomer D is 70 - 85 wt%, the content of monomer E is 10 - 20 wt%, and the content of monomer F is 5 - 10 wt%; Based on 100% by weight of the total weight of the solvent and monomers, the content of the sum of monomer D, monomer E and monomer F is 20 - 30 wt%.

8. The preparation method according to claim 6, characterized in that: The polymerization temperature is 0 - 25 °C; The polymerization time is 2 - 15 hours.

9. The preparation method according to claim 8, characterized in that: The polymerization temperature is 0 - 15 °C; The polymerization time is 10 - 15 hours.

10. The preparation method according to claim 6, characterized in that: The polymerization reaction is carried out in the presence of a protective gas; The protective gas is a gas that does not react with raw materials and products.

11. The preparation method according to claim 10, characterized in that: The protective gas is nitrogen or argon.

12. The preparation method according to claim 6, wherein: The initiator is any two of azo initiators, peroxide initiators and redox initiators; The dosage of the initiator is 0.01-0.1 wt% of the total weight of the monomers.

13. The preparation method according to claim 6, wherein: The polymerization reaction is carried out under the condition that the pH value is 7-10; the pH value is adjusted by adding a pH regulator to the polymerization system; The pH regulator is at least one of sodium hydroxide, sodium carbonate, potassium carbonate and ammonia water.

14. The preparation method according to claim 13, wherein: The pH value is 7-9.

15. The preparation method according to claim 6, wherein: The polymerization reaction is carried out in the presence of a chelating agent; The chelating agent is at least one of disodium ethylenediaminetetraacetate, nitrilotriacetic acid, ammonium citrate; The dosage of the chelating agent is 0.1-0.3 wt% of the total weight of the monomers.

16. The preparation method according to claim 6, wherein: The polymerization reaction is carried out in the presence of an auxiliary agent; The auxiliary agent is at least one of urea, thiourea, ammonia water; The dosage of the auxiliary agent is 0.01-0.1 wt% of the total weight of the monomers.

17. The preparation method according to claim 6, wherein: The polymerization reaction is carried out in the presence of a molecular weight regulator; The molecular weight regulator is at least one of isopropanol, ammonia water, N,N'-methylenebisacrylamide and dimethylthiourea; The dosage of the molecular weight regulator is 0.02-0.05 wt% of the total weight of the monomers.

18. The preparation method according to claim 6, wherein: The structural formula of monomer E is: The structural formula of monomer F is; 19. Application of a polymer according to any one of claims 1 to 5 in tertiary oil recovery.

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