Preparation method of polyacrylamide for oil displacement

Abstract

The present invention belongs to the technical field of polyacrylamide preparation, and specifically relates to a method for preparing polyacrylamide for oil displacement. The method for preparing polyacrylamide for oil displacement of the present invention uses acrylamide as the main monomer, N-(1,1-dimethyl-3-oxobutyl) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin and N-dodecyl acrylamide as functional monomers, and adopts a two-polymerization process to prepare polyacrylamide for oil displacement, and in the second polymerization, polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride are creatively added to improve the dispersibility and stability of the system. The polyacrylamide for oil displacement prepared by the preparation method of the present invention has excellent salt resistance and the ability to inhibit hydrolysis, and when used for oil displacement, it also has excellent injection ability, viscosity increase and stability.

Description

Technical Field

[0001] The invention belongs to the technical field of polyacrylamide preparation, and specifically relates to a method for preparing polyacrylamide for oil displacement. Background Art

[0002] With the exploitation of crude oil, the energy of the oil layer is gradually exhausted, and tertiary oil recovery technology is widely used to improve the recovery rate of crude oil in oil fields. Polyacrylamide is used as an oil displacement agent in the oil extraction industry to increase the viscosity of the injected water, improve the oil-water mobility ratio, and expand the swept volume, thereby improving the recovery rate of crude oil. When polyacrylamide is used for offshore oil recovery, it is usually prepared by preparing it with clean water and diluting it with seawater. Among them, the high mineralization water quality formed by various metal ions in seawater requires that the polyacrylamide used for oil recovery has excellent salt resistance. In addition, the molecular weight of polyacrylamide is a key factor in determining the oil recovery effect of polyacrylamide. The higher the molecular weight of polyacrylamide, the more beneficial it is to improve the recovery rate of crude oil. Therefore, the high molecular weight and high salt resistance of polyacrylamide play a key role in improving the recovery rate of crude oil.

[0003] In addition, polyacrylamide is easily hydrolyzed in formation water and is sensitive to some ions in formation water, so the viscosity of the polymer will drop quickly. In addition, after the polymer solution undergoes strong shear in the reservoir pores, its polymer molecular chains will deform and break, causing the viscosity of the polymer solution to drop rapidly. The polymer solution will flow along the large pores of the reservoir, reducing the sweep coefficient of the displacement polymer, thereby affecting the oil recovery effect.

[0004] In summary, there is an urgent need to explore a polyacrylamide for oil displacement with excellent hydrolysis resistance and salt resistance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing polyacrylamide for oil displacement. The polyacrylamide prepared by the preparation method has hydrolysis resistance and salt resistance.

[0006] The method for preparing polyacrylamide for oil displacement of the present invention comprises the following steps:

[0007] (1) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water are mixed and stirred until completely dissolved, then nitrogen is passed to remove oxygen and the mixture is transported to a polymerization reactor;

[0008] (2) under a nitrogen atmosphere, adding potassium persulfate and sodium bisulfite to the mixed solution prepared in step (1) to carry out a polymerization reaction, and then heating to 12-15° C. and aging for 1-1.2 hours to obtain a first polyacrylamide rubber sheet, and finally crushing the first polyacrylamide rubber sheet into rubber particles by a granulator;

[0009] (3) adding sodium hydroxide solution to the colloid particles prepared in step (2), and simultaneously adding 4,4'-azobis(sodium 4-cyanovalerate), polymethyl vinyl ether and polyacryloyloxyethyltrimethylammonium chloride to carry out hydrolysis and secondary polymerization reaction to prepare a second polyacrylamide colloid sheet;

[0010] (4) Cooling the second polyacrylamide rubber sheet to 80-83°C and performing secondary granulation in a twin-screw granulator. After granulation, vacuum drying and crushing are performed to prepare polyacrylamide for oil displacement.

[0011] in:

[0012] In step (1), the weight ratio of acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water is 1: 0.005-0.007: 0.3-0.5: 0.01-0.02: 0.04-0.06: 2.5-2.8.

[0013] The structural formula of 6-acryloylethylenediamine-β-cyclodextrin in step (1) is: .

[0014] In step (2), the sum of the mass of potassium persulfate and sodium bisulfite accounts for 0.035-0.045% of the mass of acrylamide, and the mass ratio of potassium persulfate to sodium bisulfite is 1:1.

[0015] The polymerization reaction temperature in step (2) is 1-3°C, and the polymerization reaction time is 5-5.5h.

[0016] In step (3), the mass of the sodium hydroxide solution added is 22-24% of the mass of acrylamide, and the mass concentration of the sodium hydroxide solution is 30-35%.

[0017] In step (3), the amount of 4,4'-azobis(sodium 4-cyanovalerate) added is 0.06%-0.08% of the mass of acrylamide.

[0018] In step (3), the sum of the mass of polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride accounts for 0.24-0.26% of the mass of acrylamide, and the mass ratio of polymethyl vinyl ether to polyacryloyloxyethyl trimethyl ammonium chloride is 1:0.7-0.8.

[0019] In step (3), the temperature of the hydrolysis and secondary polymerization reaction is 90-93° C., and the time of the hydrolysis and secondary polymerization reaction is 4.3-4.5 h.

[0020] In step (4), the vacuum drying temperature is 72-75° C. and the drying time is 5.5-5.8 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The preparation method of polyacrylamide for oil displacement described in the present invention uses acrylamide as the main monomer, and N-(1,1-dimethyl-3-oxobutyl) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin and N-dodecyl acrylamide as functional monomers for polymerization reaction. The introduction of N-(1,1-dimethyl-3-oxobutyl) acrylamide effectively inhibits the hydrolysis structure of the amide group. In addition, by introducing an alkyl group into the acrylamide monomer skeleton, the prepared polyacrylamide can have good water solubility. At the same time, due to the introduction of a small amount of hydrophobic groups, the temperature resistance of the polyacrylamide can be improved through hydrophobic association. 6-acryloylethylenediamine-β-cyclodextrin, using its cyclic structure to enhance the stability of the prepared polyacrylamide main chain, has a strong anti-interference effect on metal cations in the solution. In addition, due to the large steric hindrance and stable spatial conformation of 6-acryloylethylenediamine-β-cyclodextrin, it can also increase the energy barrier of the rotational motion of the polyacrylamide molecular chain, making the prepared polyacrylamide molecular chain more inclined to linear orientation in aqueous solution, thereby improving the injection performance of the prepared polyacrylamide for oil displacement. Therefore, N-(1,1-dimethyl-3-oxobutyl) acrylamide and 6-acryloylethylenediamine-β-cyclodextrin are compounded to improve the hydrolysis resistance and salt resistance of the prepared polyacrylamide. The introduction of N-dodecyl acrylamide can make the prepared polyacrylamide aggregate intramolecularly or intermolecularly under the action of hydrophobic association, forming a spatial network structure, which increases the hydrodynamic radius of the fluid, promotes the increase of solution viscosity, and has good antioxidant properties. It can be seen that the combination of N-(1,1-dimethyl-3-oxobutyl) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin (rigid monomer) and N-dodecyl acrylamide with acrylamide makes the prepared polyacrylamide for oil recovery have good salt resistance, stability and hydrolysis inhibition.

[0023] (2) The preparation method of polyacrylamide for oil displacement described in the present invention adopts two polymerization processes. The first polymerization process adopts a low-temperature initiator composed of potassium persulfate and sodium bisulfite. At low temperatures, the generation and growth of free radicals are very slow, and the probability of free radical expansion termination reaction is small, which is conducive to chain growth reaction. However, if only one polymerization is used, the conversion rate of monomers such as acrylamide is reduced due to the rapid consumption rate of the initiator. Therefore, a compound 4,4'-azobis (sodium 4-cyanovalerate) initiator is used, which has a very fast decomposition rate. Once the thermal decomposition process is initiated, a large amount of heat can be released in a short time. After decomposition, only a carbon-centered free radical is formed, which has a strong hydrogen abstraction ability, thereby making the polymerization reaction more complete and ensuring that the residual monomer content is below 0.01%.

[0024] (3) In the preparation method of polyacrylamide for oil displacement described in the present invention, polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride are creatively added in the secondary polymerization. Polyacryloyloxyethyl trimethyl ammonium chloride has both steric stabilization and terminal charged quaternary ammonium salt groups to provide electrostatic effect to improve the stability of the system. Polymethyl vinyl ether is compounded to utilize the hydrogen bond formed between ether oxygen and water to play a hydrophilic role. The methyl group connected to the ether oxygen in the molecule of polymethyl vinyl ether is utilized to change the normal hydrogen bond network structure of water molecules around the polymer molecular chain to form a special molecular cluster to play a lipophilic role, thereby playing a good dispersing role in the secondary polymerization system. Therefore, polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride are compounded to enhance the stability and dispersibility of the secondary polymerization system.

[0025] (4) The polyacrylamide for oil recovery prepared by the preparation method of the present invention has excellent salt resistance and ability to inhibit hydrolysis. When used for oil recovery, it also has excellent injection ability, viscosity increasing property and stability. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to the embodiments.

[0027] Example 1

[0028] The method for preparing polyacrylamide for oil displacement described in Example 1 is composed of the following steps:

[0029] (1) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water are mixed and stirred until completely dissolved, then nitrogen is passed to remove oxygen and the mixture is transported to a polymerization reactor;

[0030] (2) under a nitrogen atmosphere, adding potassium persulfate and sodium bisulfite to the mixed solution prepared in step (1) to carry out a polymerization reaction, then heating to 13° C. and aging for 1.1 h to obtain a first polyacrylamide rubber sheet, and finally crushing the first polyacrylamide rubber sheet into rubber particles by a granulator;

[0031] (3) adding sodium hydroxide solution to the colloid particles prepared in step (2), and simultaneously adding 4,4'-azobis(sodium 4-cyanovalerate), polymethyl vinyl ether and polyacryloyloxyethyltrimethylammonium chloride to carry out hydrolysis and secondary polymerization reaction to prepare a second polyacrylamide colloid sheet;

[0032] (4) The second polyacrylamide rubber sheet is cooled to 82° C. and subjected to secondary granulation in a twin-screw granulator. After granulation, the sheet is vacuum dried and crushed to prepare polyacrylamide for oil displacement.

[0033] in:

[0034] In step (1), the weight ratio of acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water is 1:0.006:0.4:0.015:0.05:2.7.

[0035] The structural formula of 6-acryloylethylenediamine-β-cyclodextrin in step (1) is: .

[0036] In step (2), the sum of the mass of potassium persulfate and sodium bisulfite accounts for 0.040% of the mass of acrylamide, and the mass ratio of potassium persulfate to sodium bisulfite is 1:1.

[0037] The polymerization reaction temperature in step (2) is 2° C. and the polymerization reaction time is 5.3 h.

[0038] The mass of the sodium hydroxide solution added in step (3) is 23% of the mass of acrylamide, and the mass concentration of the sodium hydroxide solution is 33%.

[0039] In step (3), the amount of 4,4'-azobis(sodium 4-cyanovalerate) added is 0.07% of the mass of acrylamide.

[0040] In step (3), the sum of the mass of polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride accounts for 0.25% of the mass of acrylamide, and the mass ratio of polymethyl vinyl ether to polyacryloyloxyethyl trimethyl ammonium chloride is 1:0.75.

[0041] The temperature of the hydrolysis and secondary polymerization reaction in step (3) is 92° C., and the time of the hydrolysis and secondary polymerization reaction is 4.4 h.

[0042] In step (4), the vacuum drying temperature is 73°C and the drying time is 5.7h.

[0043] Example 2

[0044] The method for preparing polyacrylamide for oil displacement described in Example 2 is composed of the following steps:

[0045] (1) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water are mixed and stirred until completely dissolved, then nitrogen is passed to remove oxygen and the mixture is transported to a polymerization reactor;

[0046] (2) under a nitrogen atmosphere, adding potassium persulfate and sodium bisulfite to the mixed solution prepared in step (1) to carry out a polymerization reaction, then heating to 15° C. and aging for 1.2 h to obtain a first polyacrylamide rubber sheet, and finally crushing the first polyacrylamide rubber sheet into rubber particles by a granulator;

[0047] (3) adding sodium hydroxide solution to the colloid particles prepared in step (2), and simultaneously adding 4,4'-azobis(sodium 4-cyanovalerate), polymethyl vinyl ether and polyacryloyloxyethyltrimethylammonium chloride to carry out hydrolysis and secondary polymerization reaction to prepare a second polyacrylamide colloid sheet;

[0048] (4) The second polyacrylamide rubber sheet is cooled to 83° C. and subjected to secondary granulation in a twin-screw granulator. After granulation, the sheet is vacuum dried and crushed to prepare polyacrylamide for oil displacement.

[0049] in:

[0050] In step (1), the weight ratio of acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water is 1:0.005:0.5:0.02:0.06:2.8.

[0051] The structural formula of 6-acryloylethylenediamine-β-cyclodextrin in step (1) is: .

[0052] In step (2), the sum of the mass of potassium persulfate and sodium bisulfite accounts for 0.045% of the mass of acrylamide, and the mass ratio of potassium persulfate to sodium bisulfite is 1:1.

[0053] The polymerization temperature in step (2) is 1° C. and the polymerization time is 5.5 h.

[0054] The mass of the sodium hydroxide solution added in step (3) is 24% of the mass of acrylamide, and the mass concentration of the sodium hydroxide solution is 30%.

[0055] In step (3), the amount of 4,4'-azobis(sodium 4-cyanovalerate) added is 0.08% of the mass of acrylamide.

[0056] In step (3), the sum of the mass of polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride accounts for 0.26% of the mass of acrylamide, and the mass ratio of polymethyl vinyl ether to polyacryloyloxyethyl trimethyl ammonium chloride is 1:0.7.

[0057] The temperature of the hydrolysis and secondary polymerization reaction in step (3) is 93° C., and the time of the hydrolysis and secondary polymerization reaction is 4.5 h.

[0058] In step (4), the vacuum drying temperature is 75°C and the drying time is 5.8h.

[0059] Example 3

[0060] The method for preparing polyacrylamide for oil displacement described in Example 3 is composed of the following steps:

[0061] (1) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water are mixed and stirred until completely dissolved, then nitrogen is passed to remove oxygen and the mixture is transported to a polymerization reactor;

[0062] (2) under a nitrogen atmosphere, adding potassium persulfate and sodium bisulfite to the mixed solution prepared in step (1) to carry out a polymerization reaction, then heating to 12° C. and aging for 1 hour to obtain a first polyacrylamide rubber sheet, and finally crushing the first polyacrylamide rubber sheet into rubber particles by a granulator;

[0063] (3) adding sodium hydroxide solution to the colloid particles prepared in step (2), and simultaneously adding 4,4'-azobis(sodium 4-cyanovalerate), polymethyl vinyl ether and polyacryloyloxyethyltrimethylammonium chloride to carry out hydrolysis and secondary polymerization reaction to prepare a second polyacrylamide colloid sheet;

[0064] (4) The second polyacrylamide rubber sheet is cooled to 80° C. and subjected to secondary granulation in a twin-screw granulator. After granulation, the sheet is vacuum dried and crushed to prepare polyacrylamide for oil displacement.

[0065] in:

[0066] In step (1), the weight ratio of acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water is 1:0.007:0.3:0.01:0.04:2.5.

[0067] The structural formula of 6-acryloylethylenediamine-β-cyclodextrin in step (1) is: .

[0068] In step (2), the sum of the mass of potassium persulfate and sodium bisulfite accounts for 0.035% of the mass of acrylamide, and the mass ratio of potassium persulfate to sodium bisulfite is 1:1.

[0069] The polymerization temperature in step (2) is 3° C. and the polymerization time is 5 h.

[0070] The mass of the sodium hydroxide solution added in step (3) is 22% of the mass of acrylamide, and the mass concentration of the sodium hydroxide solution is 35%.

[0071] In step (3), the amount of 4,4'-azobis(sodium 4-cyanovalerate) added is 0.06% of the mass of acrylamide.

[0072] In step (3), the sum of the mass of polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride accounts for 0.24% of the mass of acrylamide, and the mass ratio of polymethyl vinyl ether to polyacryloyloxyethyl trimethyl ammonium chloride is 1:0.8.

[0073] In step (3), the temperature of the hydrolysis and secondary polymerization reaction is 90° C., and the time of the hydrolysis and secondary polymerization reaction is 4.3 h.

[0074] In step (4), the vacuum drying temperature is 72°C and the drying time is 5.5 h.

[0075] Comparative Example 1

[0076] The preparation method of the polyacrylamide for oil displacement described in this comparative example 1 is the same as that in Example 1, the only difference being that the raw materials 6-acryloylethylenediamine-β-cyclodextrin and N-(1,1-dimethyl-3-oxobutyl)acrylamide are not added in step (1).

[0077] Comparative Example 2

[0078] The preparation method of the polyacrylamide for oil displacement described in this comparative example 2 is the same as that in Example 1, the only difference being that the raw material N-dodecyl acrylamide is not added in step (1).

[0079] Comparative Example 3

[0080] The method for preparing the polyacrylamide for oil displacement described in Comparative Example 3 is the same as that in Example 1, except that polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride are not added in step (3).

[0081] The performance tests were conducted on the polyacrylamides for oil displacement prepared in Examples 1-3 and Comparative Examples 1-3, wherein the residual acrylamide content was determined with reference to Section 6.10 of Q / SH 0237-2008; the shear viscosity retention rate was determined with reference to Section 6.8 of Q / SH 0237-2008, and the brine used was brine II; the thermal stability was tested with reference to Section 6.12 of Q / SH 0237-2008, wherein the brine used was brine II, the experimental temperature was 80° C., and the thermal aging times were 7 days and 1 month, respectively; the results are shown in Table 1 below:

[0082] Table 1 Performance test results of polyacrylamide for oil displacement in Examples 1-3 and Comparative Examples 1-3

[0083]

[0084] It can be seen from Table 1 that the viscosity retention rate of the polyacrylamide for oil displacement prepared in Examples 1-3 is significantly higher than that of Comparative Examples 1-3. The high viscosity retention rate of the polyacrylamide for oil displacement prepared in Examples 1-3 after shearing and heat aging indicates that the prepared polyacrylamide has excellent hydrolysis resistance and salt resistance. However, due to the lack of functional monomers 6-acryloylethylenediamine-β-cyclodextrin and N-(1,1-dimethyl-3-oxobutyl)acrylamide in the raw material of Comparative Example 1, and the lack of functional monomer N-dodecylacrylamide in the raw material of Comparative Example 2, the viscosity retention rate of the polyacrylamide for oil displacement prepared in Comparative Example 1-2 is low. It can be seen that the compounding of N-(1,1-dimethyl-3-oxobutyl)acrylamide, 6-acryloylethylenediamine-β-cyclodextrin (rigid monomer), and N-dodecylacrylamide with acrylamide makes the prepared polyacrylamide for oil displacement have good salt resistance, stability and hydrolysis inhibition. In the secondary polymerization reaction of Comparative Example 3, polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride were not added, and the stability and dispersibility of the secondary polymerization reaction system could not be guaranteed, resulting in a decrease in the viscosity retention rate of the prepared polyacrylamide for oil recovery. In addition, it can be seen from the monomer residual rate that the use of specific functional monomers and acrylamide in combination, and the addition of stabilizers and dispersants in the secondary polymerization are more conducive to the completion of the polymerization reaction.

Claims

1. A method for preparing polyacrylamide for oil displacement, Features: It consists of the following steps: (1) acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water are mixed and stirred until completely dissolved, then nitrogen is passed to remove oxygen and the mixture is transported to a polymerization reactor; (2) under a nitrogen atmosphere, adding potassium persulfate and sodium bisulfite to the mixed solution prepared in step (1) to carry out a polymerization reaction, and then heating to 12-15° C. and aging for 1-1.2 hours to obtain a first polyacrylamide rubber sheet, and finally crushing the first polyacrylamide rubber sheet into rubber particles by a granulator; (3) adding sodium hydroxide solution to the colloid particles prepared in step (2), and simultaneously adding 4,4'-azobis(sodium 4-cyanovalerate), polymethyl vinyl ether and polyacryloyloxyethyltrimethylammonium chloride to carry out hydrolysis and secondary polymerization reaction to prepare a second polyacrylamide colloid sheet; (4) Cooling the second polyacrylamide rubber sheet to 80-83°C and performing secondary granulation in a twin-screw granulator. After granulation, vacuum drying and crushing are performed to prepare polyacrylamide for oil displacement.

2. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (1), the weight ratio of acrylamide, 6-acryloylethylenediamine-β-cyclodextrin, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-dodecylacrylamide, urea and deionized water is 1:0.005-0.007:0.3-0.5:0.01-0.02:0.04-0.06:2.5-2.

8.

3. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (2), the sum of the mass of potassium persulfate and sodium bisulfite accounts for 0.035-0.045% of the mass of acrylamide, and the mass ratio of potassium persulfate to sodium bisulfite is 1:

1.

4. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: The polymerization reaction temperature in step (2) is 1-3°C, and the polymerization reaction time is 5-5.5h.

5. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (3), the mass of the sodium hydroxide solution added is 22-24% of the mass of acrylamide, and the mass concentration of the sodium hydroxide solution is 30-35%.

6. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (3), the amount of 4,4'-azobis(sodium 4-cyanovalerate) added is 0.06%-0.08% of the mass of acrylamide.

7. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (3), the sum of the mass of polymethyl vinyl ether and polyacryloyloxyethyl trimethyl ammonium chloride accounts for 0.24-0.26% of the mass of acrylamide, and the mass ratio of polymethyl vinyl ether to polyacryloyloxyethyl trimethyl ammonium chloride is 1:0.7-0.

8.

8. The method for preparing the polyacrylamide for oil displacement according to claim 1, Features: In step (3), the temperature of the hydrolysis and secondary polymerization reaction is 90-93° C., and the time of the hydrolysis and secondary polymerization reaction is 4.3-4.5 h.

9. The method for preparing polyacrylamide for oil displacement according to claim 1, Features: In step (4), the vacuum drying temperature is 72-75° C. and the drying time is 5.5-5.8 h.

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