Temperature-resistant and salt-resistant cationic hydrophobic associated polymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil field chemicals, and discloses a temperature-resistant and salt-resistant cationic hydrophobic association polymer as well as a preparation method and application thereof. The polymer is prepared from the following components: acrylamide, N, N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylamine propyl ammonium chloride, ammonium persulfate, sodium hydrogen sulfite, fatty alcohol-polyoxyethylene ether and a solvent. According to the invention, a specific amount of acrylamide, N, N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylamine propyl ammonium chloride, ammonium persulfate, sodium hydrogen sulfite and fatty alcohol-polyoxyethylene ether are subjected to chemical synthesis, and a polymer with high thickening efficiency can be prepared. The polymer has the advantages of good thickening performance, small critical association concentration and excellent temperature resistance and salt resistance, and can adapt to unconventional oil fields. The product produced by the preparation method is low in residual monomer content, simple in preparation process, low in cost, easy to operate, less in pollution and easy for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemicals, and in particular to a temperature-resistant and salt-resistant cationic polymer and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of oil and gas field mining industry, more and more hydrophobic associating polymers are used in hydraulic fracturing and tertiary oil recovery. Among them, high molecular weight partially hydrolyzed polyacrylamide is the main one, but the hydrolyzed polyacrylamide product has a single structure, poor hydrolysis, and high environmental sensitivity. Its hydrolysis will be accelerated in a high temperature and strong alkaline environment. Researchers have found that adding ionic groups to polyacrylamide can effectively solve the problem of poor temperature and salt resistance.

[0003] For example, the patent CN101492515A provides an acrylamide modified graft copolymer, whose macromonomer is randomly distributed in the molecular chain, which not only enhances the rigidity of the entire macromolecular chain, promotes conformational extension, and is beneficial to viscosity increase and salt resistance, but also effectively separates the hydrophobic functional groups through the macromolecular side chains, significantly enhancing the intermolecular association. In addition, its molecular side chains with large steric hindrance and hydrophobic functional groups can inhibit the oxidative degradation of the main chain and the hydrolysis of the amide group, thereby improving the temperature resistance and anti-aging performance.

[0004] The present application provides a cationic acrylamide modified graft copolymer, which synthesizes a cationic macromonomer, and adopts micellar polymerization for copolymerization. The macromonomer is orderly embedded in the main chain of polyacrylamide, which enhances the intermolecular association. Not only does it enhance the heat and salt resistance of the macromolecular chain, but it also has a simple process and low cost. This application has the same application field as the patent CN101492515A, but the patent CN101492515A has problems such as poor heat and salt resistance when facing high-temperature and high-mineralization oil reservoirs, and the viscosity will be greatly reduced. There are factors such as poor thickening performance.

[0005] Therefore, the monomer and acrylamide are synthesized into a heat-resistant and salt-resistant hydrophobic associating polymer HACM by micellar polymerization, which solves the problem of poor heat and salt resistance of polymers in oil fields. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem of poor temperature and salt resistance of the prior art polymer.

[0007] In order to achieve the above object, the specific technical solution of the present invention is as follows: A heat-resistant and salt-resistant cationic hydrophobic associating polymer, which is formed by polymerizing the following raw materials: Acrylamide, N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride, ammonium persulfate, sodium bisulfite, fatty alcohol polyoxyethylene ether, solvent; , formula (1); , formula (2); The N,N-dimethyl-N-methylacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride has a structure shown in formula (1), and the acrylamide has a structure shown in formula (2).

[0008] In the cationic polymer, relative to 100 parts by weight of the solvent, the content of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride is 0.8 parts by weight, the content of acrylamide is 6-12 parts by weight, and the content of fatty alcohol polyoxyethylene ether is 0.3-0.35 parts by weight.

[0009] The acrylamide needs to be prepared into an aqueous solution with a concentration of 20-25wt% when mixed.

[0010] The solvent is deionized water.

[0011] The method comprises: mixing and reacting the components in the composition.

[0012] The operation of mixing the components in the heat-resistant and salt-resistant cationic polymer specifically comprises the following steps: (1) in the presence of the first part of the solvent, a fatty alcohol polyoxyethylene ether and N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride are first mixed to obtain a first mixed solution; and an acrylamide solution is first contacted with the second part of the solvent to dissolve, to obtain a solution I; (2) performing a second mixing of the first mixed solution and the solution I to obtain a second mixed solution; and performing a second contacting of the ammonium persulfate and the sodium bisulfite with a third portion of the solvent to dissolve the ammonium persulfate and the sodium bisulfite to obtain a solution II; (3) contacting the second mixed solution with the solution II for reaction; The weight ratio of the first part of solvent, the second part of solvent and the third part of solvent is 4-5:4-5:1.

[0013] The conditions for first mixing acrylamide and N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride and second mixing the first mixed solution with the solution I include: stirring speed of 50-60 rpm, temperature of 20-30° C., and time of 5-10 min.

[0014] In step (3), the contact reaction conditions include: temperature of 50-55°C and time of 6-7h.

[0015] An application of the heat-resistant and salt-resistant cationic polymer in oil and gas development.

[0016] Compared with the prior art, the present invention has the following beneficial effects: A new type of temperature-resistant and salt-resistant long carbon chain hydrophobic cationic monomer DMHOAC was designed. The monomer contains a long carbon chain, an ester group, and an amide group. It has good salt resistance and temperature resistance.

[0017] The present invention successfully prepares a high-performance polymer by precisely polymerizing a specific amount of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride, acrylamide, fatty alcohol polyoxyethylene ether, ammonium persulfate and solvent. The polymer not only has high thickening efficiency, but also has excellent thickening performance and exhibits a small critical association concentration, which means that a significant thickening effect can be achieved at a lower concentration. In addition, the polymer also has excellent temperature and salt resistance, so that it can adapt to the application requirements of complex environments such as unconventional oil fields.

[0018] It is worth noting that the preparation method provided by the present invention is not only simple in process and low in cost, but also easy to operate and generates less pollution during the production process. This method ensures that the residual monomer content of the product is low, thereby improving the purity and performance of the product. These advantages make the polymer easier to achieve industrial production and provide an efficient and environmentally friendly solution for related industries.

[0019] In summary, the present invention successfully prepares a polymer with high thickening efficiency, excellent thickening performance, and excellent temperature and salt resistance through precise polymerization reaction and optimized preparation process. The preparation process of the polymer is simple, low in cost, less in pollution, easy to industrialize, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the apparent viscosity result of the salt resistance test of the embodiment of the present invention.

[0021] Figure 2 The following are the apparent viscosity results at different temperatures of the embodiments of the present invention.

[0022] Figure 3 This is the FTIR characterization spectrum of the embodiment of the present invention. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] It should be noted that, in various aspects of the present invention, for the same components in various aspects, the present invention is described only once in one aspect without repeated description, which should not be understood by those skilled in the art as a limitation of the present invention.

[0025] It should be noted that in the present invention, raw materials not described can be obtained from general commercial sources, and those skilled in the art can purchase them as needed, and they will not be described in detail in the present invention.

[0026] In the present invention, unless otherwise specified, the room temperature or normal temperature refers to 25±2°C.

[0027] As mentioned above, the first aspect of the present invention provides a heat-resistant and salt-resistant cationic polymer, which contains the following components stored in a mixture or separately: N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride, acrylamide, fatty alcohol polyoxyethylene ether, ammonium persulfate, solvent; , formula (1); , formula (2); The N,N-dimethyl-N-methylacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride has a structure shown in formula (1), and the acrylamide has a structure shown in formula (2).

[0028] Preferably, in the heat-resistant and salt-resistant cationic polymer, relative to 100 parts by weight of the solvent, the content of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride is 1-2 parts by weight, the content of acrylamide is 19-20 parts by weight, the content of fatty alcohol polyoxyethylene ether is 0.3-0.35 parts by weight, and the content of ammonium persulfate and sodium bisulfite is 0.08-0.09 parts by weight.

[0029] The inventors have found that by adopting the specific implementation method in this preferred case, a polymer with higher thickening performance can be obtained.

[0030] According to a particularly preferred embodiment, the acrylamide is an aqueous solution of acrylamide with a concentration of 20-25 wt%.

[0031] According to a particularly preferred embodiment, the concentration of the fatty alcohol polyoxyethylene ether is 80-90%.

[0032] As mentioned above, the second aspect of the present invention provides a method for preparing a temperature-resistant and salt-resistant cationic polymer, which comprises: mixing the components in the composition described in the first aspect.

[0033] Preferably, the operation of mixing the components in the cationic polymer composition comprises the following steps: (1) in the presence of a first portion of solvent, acrylamide and N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride are first mixed to obtain a first mixed solution; and The fatty alcohol polyoxyethylene ether is first contacted with the second part of the solvent to dissolve, thereby obtaining a solution I; (2) performing a second mixing of the first mixed solution and the solution I to obtain a second mixed solution; and performing a second contacting of the ammonium persulfate with a third portion of the solvent to dissolve the ammonium persulfate to obtain a solution II; (3) contacting the second mixed solution with the solution II for reaction; The weight ratio of the first part of solvent, the second part of solvent and the third part of solvent is 4-5:4-5:1.

[0034] The present invention has no special requirements for the operations of the first contact and the second contact, as long as the fatty alcohol polyoxyethylene ether and ammonium persulfate can be dissolved respectively. Exemplarily, the conditions of the first contact and the second contact independently include: a stirring speed of 50-60rpm and a temperature of 20-30°C.

[0035] Preferably, the conditions for the first mixing and the second mixing independently include: a stirring speed of 50-60 rpm, a temperature of 20-30° C., and a time of 5-10 min.

[0036] Preferably, in step (3), the contact reaction conditions include at least: a temperature of 50-55° C. and a reaction time of 6-7 h.

[0037] As mentioned above, the fourth aspect of the present invention provides the use of the cationic polymer described in the third aspect in oil and gas development.

[0038] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials used are commercially available products.

[0039] N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride: self-synthesized; Acrylamide: purchased from BASF; Sodium bisulfite: purchased from BASF; Fatty alcohol polyoxyethylene ether: purchased from BASF; Ammonium persulfate: purchased from BASF; In the following examples, the solvent is deionized water.

[0040] Example 1 This embodiment provides a method for preparing a cationic polymer, the method comprising: (1) Add 20 g of acrylamide aqueous solution (concentration: 40 wt%) and 20 g of deionized water into a reactor at 30° C., then add 1 g of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride (concentration: 80 wt%), and stir at 50 rpm for 10 min to obtain a first mixed solution; and weigh 0.35 g of fatty alcohol polyoxyethylene ether and dissolve it in 20 g of deionized water to obtain solution I; (2) Stirring the first mixed solution and solution I at 60 rpm for 5 min at 30° C. to obtain a second mixed solution; and dissolving 0.012 g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 in 10 g of deionized water to obtain solution II; (3) The second mixed solution and solution II obtained above were reacted in a reactor at 55° C. for 6 h to obtain a heat-resistant and salt-resistant cationic polymer H1.

[0041] Example 2 This embodiment provides a method for preparing a cationic polymer, the method comprising: (1) Add 25 g of acrylamide aqueous solution (concentration of 40 wt%) and 25 g of deionized water into a reactor at 30° C., then add 1 g of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride (concentration of 80 wt%), and stir at 50 rpm for 10 min to obtain a first mixed solution; and weigh 0.35 g of fatty alcohol polyoxyethylene ether and dissolve it in 1 g of deionized water to obtain solution I; (2) Stirring the first mixed solution and solution I obtained above at 30° C. and 60 rpm for 8 min to obtain a second mixed solution; and dissolving 0.012 g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 in 10 g of deionized water to obtain solution II; (3) The second mixed solution and solution II obtained above were reacted in a reactor at 55° C. for 6 h to obtain a cationic polymer H2.

[0042] Example 3 This embodiment provides a method for preparing a heat-resistant and salt-resistant cationic polymer, the method comprising: (1) In a reaction kettle at 30° C., 30 g of an aqueous solution of acrylamide (with a concentration of 40 wt%) and 20 g of deionized water were added, and then 1 g of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride (with a concentration of 80 wt%) was added, and stirred at 55 rpm for 8 min to obtain a first mixed solution; and 0.35 g of fatty alcohol polyoxyethylene ether was weighed and dissolved in 10 g of deionized water to obtain a solution I; (2) Stirring the first mixed solution and solution I obtained above at 30° C. and 60 rpm for 5 min to obtain a second mixed solution; and dissolving 0.012 g of ammonium persulfate in 10 g of deionized water to obtain solution II; (3) The second mixed solution and solution II obtained above were reacted in a reactor at 55° C. for 6 h to obtain a cationic polymer H3.

[0043] Example 4 In this example, a heat-resistant and salt-resistant cationic polymer is prepared in a manner similar to that of Example 3, except that 0.3 g of fatty alcohol polyoxyethylene ether is used.

[0044] The remaining steps are the same as those in Example 3.

[0045] Cationic polymer H4 was obtained.

[0046] Example 5 In this example, a heat-resistant and salt-resistant cationic polymer was prepared in a manner similar to that of Example 3, except that 0.01 g of ammonium persulfate and sodium bisulfite were used.

[0047] The remaining steps are the same as those in Example 3.

[0048] Cationic polymer H5 was obtained.

[0049] Comparative Example 1 In this comparative example, a heat-resistant and salt-resistant cationic polymer was prepared in a manner similar to that of Example 3, except that an equal mass of trimethylbenzene was used to replace acrylamide.

[0050] The remaining steps are the same as those in Example 3.

[0051] The cationic polymer HA1 was obtained.

[0052] Comparative Example 2 In this comparative example, a cationic polymer was prepared in a similar manner to that of Example 3, except that an equal mass of sodium lauryl sulfate was used to replace the fatty alcohol polyoxyethylene ether.

[0053] The remaining steps are the same as those in Example 3.

[0054] The cationic polymer HA2 was obtained.

[0055] Comparative Example 3 In this comparative example, a heat-resistant and salt-resistant cationic polymer was prepared in a similar manner to Example 3, except that 0.4 g of fatty alcohol polyoxyethylene ether was used.

[0056] The remaining steps are the same as those in Example 3.

[0057] Cationic polymer HA3 was obtained.

[0058] Comparative Example 4 In this comparative example, a heat-resistant and salt-resistant cationic polymer was prepared in a similar manner to Example 3, except that 35 g of acrylamide was used.

[0059] The remaining steps are the same as those in Example 3.

[0060] Cationic polymer HA4 was obtained.

[0061] Test Results The thickening rate and heat and salt resistance of the heat and salt resistant cationic polymers prepared in the examples and comparative examples were tested. The specific results are shown in Table 1.

[0062] Among them, the thickening rate and temperature and salt resistance are tested by the apparent viscosity method in reference to the thickening performance and temperature and salt resistance in standard Q / SY 1750-2014; The specific detection method is: (1) At room temperature, pour 300 mL of distilled water into the mixer, turn on the mixer, adjust the voltage, keep the liquid in a vortex state and be able to see the bottom of the mixer, then weigh 1.500 g of polymer (the polymerizing agent needs to be dried in an oven at 105°C for 4 h or the net weight minus the water content), slowly and evenly add the polymer (addition time is less than 30 s), start timing after the polymer is added, and measure the liquid viscosity every 5 min using a six-speed rotary viscometer. After the viscosity tends to stabilize, measure its apparent viscosity to obtain its thickening properties.

[0063] Table 1 Apparent viscosity / mPa·s Example 1 67.32 Example 2 69.86 Example 3 70.36 Example 4 68.32 Example 5 26.44 Comparative Example 1 43.25 Comparative Example 2 44.28 Comparative Example 3 42.19 Comparative Example 4 44.32 It can be seen from Table 1 that the heat-resistant and salt-resistant cationic polymer provided by the present invention can be used to prepare a polymer with good thickening performance.

[0064] (2) Prepare 10000-80000 mg / L NaCl aqueous solution and 500-5000 mg / L CaCl2 aqueous solution as solvents to prepare a polymer solution with a mass concentration of 0.5%. Use a rotational viscometer to measure its apparent viscosity at room temperature.

[0065] from Figure 1 It can be seen that the heat-resistant and salt-resistant cationic polymer provided by the present invention can be used to prepare a polymer with good salt resistance.

[0066] (2) Prepare a polymer solution with a mass concentration of 0.5% and measure its apparent viscosity at different temperatures.

[0067] from Figure 2 It can be seen that the heat-resistant and salt-resistant cationic polymer provided by the present invention can be used to prepare a polymer with good heat resistance.

[0068] (3) The polymer was characterized by FTIR, and the product was purified by soaking in anhydrous ethanol. After drying, the product was mixed with potassium bromide at a mass ratio of 1:100, ground and pressed into tablets to prepare samples. from Figure 3 It can be obtained that the stretching vibration absorption peak of -NH- bond is at 3434 cm -1 The asymmetric stretching vibration absorption peak of -CH2- bond is at 2918 cm -1 The symmetric stretching vibration absorption peak of -CH2- bond is at 2850 cm -1 The stretching vibration absorption peak of the C=O bond in the ester group is at 1668 cm -1 The in-plane bending vibration absorption peak of the NH bond of the amide group is at 1554 cm -1 The stretching vibration absorption peak of CN bond is at 1406 cm -1 The stretching vibration absorption peak of COC bond is at 1103 cm -1 The out-of-plane bending vibration absorption peak of the NH bond is at 802 cm -1 All groups in the target structure are shown in the spectrum, and there is no double bond absorption peak in the spectrum. This indicates that the polymer was successfully synthesized.

[0069] According to the above results, the heat-resistant and salt-resistant cationic polymer provided by the present invention exhibits significant advantages and superiority. First, in terms of thickening performance, the apparent viscosity of the polymer prepared in the embodiment is significantly higher than that of the comparative example, indicating that the polymer has excellent thickening ability. This property makes the polymer have significant advantages in applications where the viscosity of the liquid needs to be increased, such as oil and gas field exploitation, water treatment and other fields.

[0070] Secondly, the polymer exhibits excellent salt tolerance. In aqueous solutions containing high concentrations of NaCl and CaCl2, the polymer can still maintain a high apparent viscosity, showing its strong salt tolerance. This is a very important feature for applications in saline-alkali land, seawater or saline environments.

[0071] In addition, the polymer also has good temperature resistance. The apparent viscosity was measured at different temperatures, and the results showed that the polymer can still maintain a stable viscosity at high temperatures, indicating that it has excellent temperature resistance. This makes the polymer have unique advantages in applications in high temperature environments, such as the exploitation of high-temperature oil and gas wells.

[0072] Finally, FTIR characterization confirmed that all groups in the target structure of the polymer were successfully synthesized, and there was no double bond absorption peak in the figure, indicating that the polymer was successfully synthesized and the structure was stable. This result further proves the reliability of the synthesis method and structure of the polymer, and provides a strong guarantee for its stability and durability in practical applications.

[0073] In summary, the heat-resistant and salt-resistant cationic polymer not only has excellent thickening performance, but also exhibits excellent salt and temperature resistance, as well as a stable chemical structure. These advantages make the polymer have broad application prospects and unique advantages in many fields, especially in oil and gas field exploitation, water treatment, and high-temperature environment applications.

[0074] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the aggregation of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A heat-resistant and salt-resistant cationic hydrophobically associating polymer, characterized in that: The polymer is formed by polymerization of the following raw materials: Acrylamide, N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride, ammonium persulfate, sodium bisulfite, fatty alcohol polyoxyethylene ether, solvent; , formula (1); , formula (2); The N,N-dimethyl-N-methylacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride has a structure shown in formula (1), and the acrylamide has a structure shown in formula (2).

2. The polymer according to claim 1, characterized in that In the cationic polymer, relative to 100 parts by weight of the solvent, the content of N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride is 0.8 parts by weight, the content of acrylamide is 6-12 parts by weight, and the content of fatty alcohol polyoxyethylene ether is 0.3-0.35 parts by weight.

3. The polymer according to claim 1 or 2, characterized in that The acrylamide needs to be prepared into an aqueous solution with a concentration of 20-25wt% when mixed.

4. The polymer according to claim 1 or 2, wherein The solvent is deionized water.

5. A method for preparing a heat-resistant and salt-resistant cationic polymer, characterized in that: The method comprises: mixing and reacting the components in the composition according to any one of claims 1 to 4.

6. The method according to claim 5, characterized in that The operation of mixing the components in the heat-resistant and salt-resistant cationic polymer specifically comprises the following steps: (1) in the presence of the first part of the solvent, a fatty alcohol polyoxyethylene ether and N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropyl ammonium chloride are first mixed to obtain a first mixed solution; and an acrylamide solution is first contacted with the second part of the solvent to dissolve, to obtain a solution I; (2) performing a second mixing of the first mixed solution and the solution I to obtain a second mixed solution; and performing a second contacting of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 with a third portion of the solvent to dissolve the mixture to obtain a solution II; (3) contacting the second mixed solution with the solution II for reaction; The weight ratio of the first part of solvent, the second part of solvent and the third part of solvent is 4-5:4-5:

1.

7. The method according to claim 6, characterized in that The conditions for first mixing acrylamide and N,N-dimethyl-N-methacryloyloxyethyl-N-2-hydroxy-1-octadecylaminopropylammonium chloride and second mixing the first mixed solution with the solution I include: stirring speed of 50-60 rpm, temperature of 20-30° C., and time of 5-10 min.

8. The method according to claim 6 or 7, characterized in that: In step (3), the contact reaction conditions include: temperature of 50-55°C and time of 6-7h.

9. Use of the heat-resistant and salt-resistant cationic polymer according to claim 1 in oil and gas development.

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