Emulsified temperature-resistant and salt-resistant polyacrylamide and preparation method thereof

Abstract

The application discloses emulsified temperature-resistant salt-resistant polyacrylamide and a preparation method thereof. The polyacrylamide is prepared by using acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and N-dodecyl acrylamide as monomers, and using a composite initiator through aqueous solution polymerization to obtain a quaternary copolymer. The polymer has good emulsification, temperature resistance and salt resistance, and has a high viscosity retention rate under the conditions of a temperature of 50-75 DEG C and a salinity of 5000-35000 mg / L. The preparation process is simple and practical, and is beneficial to industrial production.

Description

An emulsified, temperature-resistant, and salt-resistant polyacrylamide and its preparation method Technical Field

[0001] This application relates to the field of polymer compound technology, and in particular to an emulsified, temperature-resistant, and salt-resistant polyacrylamide and its preparation method. Background Technology

[0002] With the rapid development of my country's economy, the dependence on foreign oil has been increasing year by year, posing a huge threat to my country's energy security. Therefore, how to increase my country's domestic oil production has become a difficult problem for major oilfields in China. Take the heavy oil extraction in the Bohai Oilfield as an example. The Bohai Oilfield is mostly fluvial sedimentary facies with complex geological structures and various types of oil and gas reservoirs. Geological faults are intertwined, the oil-water system is irregularly distributed, the oil reservoirs are relatively shallow, and the oil layer thickness is large, typically ranging from 5 to 120 meters, with an average of 32.7 meters. The total heavy oil reserves are 2.46 billion cubic meters, of which proven geological reserves are 1.44 billion cubic meters, accounting for more than 80% of the total oilfield reserves. Currently, chemical flooding in the Bohai Oilfield has basically solved the polymer flooding problem for deltaic sedimentary and Class I heavy oil reserves. However, for Class II heavy oil with high underground crude oil viscosity (greater than 150 mPa·s) and under high-salinity reservoir conditions, the reservoir adaptability of chemical flooding agents still needs further research.

[0003] Chemical flooding agents are mainly polyacrylamide polymers. However, in the Bohai Oilfield, existing polyacrylamide polymers have problems such as poor temperature and salt resistance, low viscosity-increasing ability, and difficulty in emulsifying heavy oil. Therefore, it is of great significance to synthesize a new type of polyacrylamide polymer that can achieve temperature resistance, salt resistance, and emulsification ability for heavy oil. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, this application provides an emulsified, temperature-resistant, and salt-resistant polyacrylamide and its preparation method.

[0005] In the first aspect, this application provides an emulsified, temperature-resistant, and salt-resistant polyacrylamide, which is achieved by the following technical solution.

[0006] An emulsified, temperature-resistant, and salt-resistant polyacrylamide, the structural formula of which is as follows:

[0007]

[0008] In the formula, x, y, z, and p are the molar numbers of structural units of acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and N-octadecylacrylamide (M), respectively, and x:y:z:p = (20~1000):(20~1000):(20~1000):(20~1000).

[0009] Furthermore, the viscosity-average molecular weight of polyacrylamide is 5 million to 15 million, and the anionic content is 5% to 45%.

[0010] Secondly, this application provides a method for preparing emulsified, temperature-resistant, and salt-resistant polyacrylamide, which is achieved by the following technical solution.

[0011] A method for preparing the above-mentioned emulsified, temperature-resistant, and salt-resistant polyacrylamide includes the following steps:

[0012] S1. Mix acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, N-octadecylacrylamide with deionized water. After complete dissolution, add acrylamide. The mass ratio of acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and N-octadecylacrylamide is 92:(25~40):(15~35):(1~4).

[0013] S2. Add emulsifier, surfactant, urea, chain transfer agent and solubilizer in sequence;

[0014] S3. Adjust the pH of the solution;

[0015] S4. Adjust the temperature to the initiation temperature and purge with nitrogen;

[0016] S5. Add initiator and reducing agent, and react for a certain period of time;

[0017] S6. After the reaction is complete, the gel block is granulated, dried, and pulverized to obtain emulsified, temperature-resistant, and salt-resistant polyacrylamide.

[0018] Furthermore, in step S1, the monomer concentration is 15%-35%.

[0019] Further, in step S2, the emulsifier is selected as OP-10, and the mass ratio of emulsifier to acrylamide is (0.5-3):184; the surfactant is selected as Tween 20, and the mass ratio of surfactant to acrylamide is (10-15):92; the chain transfer agent is selected as acetone, and the mass-volume ratio of acrylamide to chain transfer agent is 46-122.67 g / ml; the cosolvent is selected as propylene glycol, and the mass-volume ratio of acrylamide to cosolvent is 61.33-184 g / ml; the mass ratio of urea to acrylamide is (5-10):184.

[0020] Furthermore, in step S3, the pH of the solution is adjusted using NaOH solution with a mass fraction of 20-40%, and the pH of the solution is adjusted to 2-12.

[0021] Furthermore, in step S4, the initiation temperature is 0–40°C; the nitrogen purging time is 20–40 min.

[0022] Furthermore, in step S5, the amount of initiator added is 0.2‰ to 0.5‰ of the total mass of the monomers; the initiator is a composite initiation system, including benzoyl peroxide (BPO), N-diisopropylimidazoline hydrochloride (VAO44), tert-butyl hydroperoxide (TBHP), and sodium metabisulfite (SDMS), and the mass ratio of the four initiators is m(BPO):m(VAO44):m(TBHP):m(SDMS) = (1~1.5):(1.5~2):(2~3.5):(3~4.5).

[0023] Furthermore, in step S5, the reducing agent is ferrous ammonium sulfate, and the amount of ferrous ammonium sulfate added is 0.2 to 0.5 times the mass of tert-butyl hydrogen peroxide.

[0024] Furthermore, in step S5, the reaction time is 8h to 16h.

[0025] This application has the following beneficial effects.

[0026] This invention yields a novel polyacrylamide through a free radical copolymerization reaction of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and a functional monomer (N-dodecylacrylamide). This polymer exhibits excellent emulsification, temperature resistance, and salt tolerance, with high viscosity retention at temperatures ranging from 50 to 75°C and mineralization levels from 5000 to 35000 mg / L. The invention utilizes a composite initiator, ensuring a stable free radical release rate and maintaining a stable free radical concentration within the system, thereby increasing initiation efficiency and facilitating the formation of high molecular weight products. Furthermore, the preparation process of this invention is simple and conducive to industrial production. Attached Figure Description

[0027] Figure 1 is a diagram illustrating the preparation process of the polyacrylamide polymer of the present invention. Detailed Implementation

[0028] The present patent application will be further described below with reference to the embodiments.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following preparation examples and examples are commercially available unless otherwise specified.

[0030] (1) Molecular design of polyacrylamide polymers

[0031]

[0032] (2) Preparation of polymerizable surfactants

[0033] ① Polymer synthesis

[0034] A certain mass of AM, AMPS, AA, and the functional monomer (N-dodecylacrylamide) was weighed and placed in a beaker containing ultrapure water, stirred, and dissolved (total monomer mass fraction: 25 wt%). Emulsifier, surfactant, urea, chain transfer agent, and cosolvent were added sequentially. The pH of the solution was then adjusted to 7.8–8.0 using NaOH solution (30 wt%). The solution was transferred to a reactor, and polymerization was carried out at 25°C. High-purity N2 was introduced for approximately 15 minutes, followed by the addition of peroxide initiator BPO and azo initiator VAO44, then redox initiators tert-butyl hydroperoxide and sodium metabisulfite. Finally, a reducing agent (ferrous ammonium sulfate) was added. When the solution began to become viscous, the N2 flow was stopped, and the reaction was allowed to stand until the system temperature reached its peak. After approximately 12 hours of aging, an elastic gel block was obtained.

[0035] ② Polymer post-processing

[0036] The obtained polymer blocks were pulverized using a granulator to obtain polymer granules. These granules were then dried using a blower at 50–60°C for 2 hours to obtain dried polymer particles. Subsequently, the dried polymer was granulated using a pulverizer and sieved to obtain a small-scale product of the functional polymer. The overall preparation process is shown in Figure 1.

[0037] (3) Optimization of the synthesis process of polyacrylamide polymer

[0038] Factors that significantly affect the reaction include: degree of hydrolysis, AMPS content, surfactant content, functional monomer content, co-solvent content, chain transfer agent content, pH value, reaction temperature, and reaction time. These factors will be examined individually below.

[0039] The degree of hydrolysis, dissolution time, and viscosity are in accordance with the industry standard "Performance Indicators and Evaluation Methods for Polymers Used in Offshore Oilfield Displacement".

[0040] Degree of hydrolysis: a) Prepare a polymer stock solution with a concentration of 5000 mg / L using distilled water. b) Dilute the above solution to a target concentration of 300 mg / L. c) Place a clean conductivity meter electrode into the test solution, ensuring the water level covers the black graduation mark on the probe, and read a stable conductivity value (conductivity meter set to low speed). d) Add 0.01 mol / L HCl solution to the test solution using a 1 mL pipette, and read a stable conductivity value. e) Repeat step d) until the total volume of hydrochloric acid added reaches 18 mL, at which point the titration ends. f) Plot the amount of hydrochloric acid consumed on the x-axis and the conductivity on the y-axis. Use the least squares method to fit the near-linear portions of the curve in the first and second halves of the graph to a straight line. The x-axis of the intersection of the two straight lines represents the volume of standard hydrochloric acid solution consumed at the titration endpoint. g) Calculate the degree of hydrolysis. Where: HD—degree of hydrolysis, expressed as a percentage; c—concentration of hydrochloric acid standard solution, mol / L; V—volume of hydrochloric acid standard solution consumed by the sample solution, mL; m—mass of the target solution weighed, g; 23—mass difference between sodium acrylate and acrylamide repeating units; 71—mass of acrylamide repeating units equivalent to 1.00 mL of hydrochloric acid standard solution [c(HCl)=1.000mol / L].

[0041] Dissolution time: a) The time required for a polymer solution with a concentration of 5000 mg / L prepared in distilled water to be filtered through a stainless steel mesh with a pore size of 149 μm under a pressure difference of 0.05 MPa, resulting in a residue content of less than 2%. b) Calculation of residue content: In the formula: I c — Residue content; m — Polymer sample mass, g; m1 — Mass of stainless steel mesh before filtration, g; m2 — Mass of stainless steel mesh after filtration, g.

[0042] Viscosity: a) Apparent viscosity was determined using a Brookfield viscometer. b) The composition of water, polymer mass concentration, test temperature, shear rate, and measurement system were specified.

[0043] ① The effect of degree of hydrolysis on polymer properties

[0044] By changing the amount of AA added, the degree of polymer hydrolysis can be altered. The dissolution time of the polymer and the viscosity of the aqueous solution are shown in Table 1.

[0045] Table 1. Effect of degree of hydrolysis on polymer solubility and viscosity.

[0046]

[0047] The following ingredients were added: 1 mL of cosolvent, 1.5 mL of chain transfer agent, 25 g of surfactant, 0.5 g of BPO, 3 g of emulsifier OP-10, 5 g of urea, 0.5 mL of tert-butyl hydroperoxide (0.5%), 3.5 mL of VA044 (1%), 1 mL of sodium metabisulfite (1%), 0.1 mL of ferrous ammonium sulfate (1 wt%), pH 8, and reaction temperature 25℃.

[0048] Experimental results show that as the degree of polymer hydrolysis increases from 0 to 25 mol%, the dissolution rate of the polymer slows down, but the viscosity of the polymer increases. Therefore, the degree of polymer hydrolysis should not be too low. The degree of polymer hydrolysis should be controlled between 20% and 27%. Therefore, the amount of AA added should be controlled between 50 and 80 g, preferably 70 g.

[0049] ②The effect of AMPS content on polymer properties

[0050] AMPS plays a role in temperature and salt resistance in polymers. Considering the high mineralization of the SZ36-1 block, AMPS groups need to be introduced into the polymer. Therefore, the amount of AMPS added was varied to explore its effect on the dissolution time and viscosity of the aqueous solution of the polymer, as shown in Table 2.

[0051] Table 2. Effects of AMPS content on polymer solubility and viscosity.

[0052]

[0053]

[0054] The following ingredients were added: 1 mL of cosolvent, 1.5 mL of chain transfer agent, 25 g of surfactant, 0.5 g of BPO, 3 g of emulsifier OP-10, 5 g of urea, 0.5 mL of tert-butyl hydroperoxide (0.5%), 3.5 mL of VA044 (1%), 1 mL of sodium metabisulfite (1%), 0.1 mL of ferrous ammonium sulfate (1 wt%), pH 8, and reaction temperature 25℃.

[0055] Experimental results show that as the AMPS content increases, the polymer dissolution rate increases and the viscosity also increases slightly. However, when the AMPS content increases from 45g to 60g, the increase in viscosity is not very significant. In addition, in order to synthesize high molecular weight polymers, the AMPS content should not be increased further. The amount of AMPS added should be controlled at 30-70g, preferably 60g.

[0056] ③ The effect of surfactant content on polymer properties

[0057] Surfactants can form micelles in monomer aqueous solutions, promoting the solubility of functional monomers. The micelles formed between the two promote the polymerization of monomers. Therefore, the effect of varying the amount of surfactant added on polymer viscosity and dissolution time was investigated, as shown in Table 3.

[0058] Table 3. Effects of surfactant content on polymer solubility and viscosity.

[0059]

[0060] The following components were added: 1 mL of cosolvent, 1.5 mL of chain transfer agent, 0.5 g of BPO, 3 g of emulsifier OP-10, 5 g of urea, 0.5 mL of tert-butyl hydroperoxide (0.5%), 3.5 mL of VA044 (1%), 1 mL of sodium metabisulfite (1%), 0.1 mL of ferrous ammonium sulfate (1 wt%), pH 8, and reaction temperature 25℃.

[0061] Experimental results show that as the surfactant content increases, the polymer dissolution rate increases, and the viscosity also increases. When the amount added is 25g, the polymer viscosity reaches its peak. Therefore, the amount of surfactant added is 20-30g, preferably 25g.

[0062] ④ Effect of M monomer content on polymer properties

[0063] To further clarify the effect of functional monomer content on polymer properties, the amount of M added was varied, and its effect on the polymer is shown in Table 4.

[0064] Table 4. Effects of M content on polymer solubility and viscosity.

[0065]

[0066] The following ingredients were added: 1 mL of cosolvent, 1.5 mL of chain transfer agent, 25 g of surfactant, 0.5 g of BPO, 3 g of emulsifier OP-10, 5 g of urea, 0.5 mL of tert-butyl hydroperoxide (0.5%), 3.5 mL of VA044 (1%), 1 mL of sodium metabisulfite (1%), 0.1 mL of ferrous ammonium sulfate (1 wt%), pH 8, and reaction temperature 25℃.

[0067] Experimental results show that as monomer M increases from 2g to 10g, the polymer dissolution time increases from 25min to 125min, while the viscosity increases from 9.8mPa·s to 99.1mPa·s. Therefore, increasing M increases the viscosity of the polymer solution, but also makes the polymer more difficult to dissolve; thus, the amount of M added should not be excessive. When the amount of M added is 7g, the polymer viscosity is 55.2mPa·s, which is greater than the specified 50mPa·s. Therefore, the amount of M added should be 3–8g, preferably 7g.

[0068] ⑤ Effect of cosolvent content on polymer properties

[0069] To improve the dissolution rate of the polymer, the content of the co-solvent was increased, and its effect on the dissolution time and viscosity of the polymer was investigated, as shown in Table 5.

[0070] Table 5. Effect of cosolvent content on polymer solubility and viscosity.

[0071]

[0072]

[0073] The addition amounts of chain transfer agent were 1.5 mL, surfactant 25 g, BPO 0.5 g, emulsifier OP-10 3 g, urea 5 g, tert-butyl hydroperoxide (0.5%) 0.5 mL, VA044 (1%) 3.5 mL, sodium metabisulfite (1%) 1 mL, ferrous ammonium sulfate (1 wt%) 0.1 mL, pH 8, and reaction temperature 25 °C.

[0074] Experimental results show that as the cosolvent content increases from 1 mL to 5 mL, the polymer dissolution time decreases from 60 min to 25 min, but the viscosity decreases from 55.2 mPa·s to 35.1 mPa·s. When the cosolvent content is less than 3 mL, the viscosity of the polymer solution is higher than 50 mPa·s. Therefore, the cosolvent content is 1–3 mL, preferably 1 mL.

[0075] ⑥ Effect of chain transfer agent content on polymer properties

[0076] To improve the dissolution rate of polymers, in addition to increasing the content of co-solvents, the content of chain transfer agents can also be increased to reduce the molecular weight of the polymer and shorten the dissolution time. The effect of chain transfer agent content on polymer dissolution time and viscosity is shown in Table 6.

[0077] Table 6. Effect of chain transfer agent content on polymer solubility and viscosity.

[0078]

[0079]

[0080] The amount of cosolvent added was 1 mL, the amount of surfactant added was 25 g, BPO was 0.5 g, emulsifier OP-10 was 3 g, urea was 5 g, hydrogen peroxide tert-butyl (0.5%) was 0.5 mL, VA044 (1%) was 3.5 mL, sodium metabisulfite (1%) was 1 mL, ferrous ammonium sulfate (1 wt%) was 0.1 mL, the pH was 8, and the reaction temperature was 25℃.

[0081] Experimental results show that as the chain transfer agent content increases from 1.5 mL to 4 mL, the polymer dissolution time decreases from 60 min to 25 min, but the viscosity decreases from 55.2 mPa·s to 41.0 mPa·s. Therefore, excessively high chain transfer agent content leads to a decrease in polymer molecular weight and viscosity. When the chain transfer agent content is 2.5 mL, the polymer solution viscosity is 56.5 mPa·s, meeting the requirements, but the dissolution time is 35 min, exceeding the required 30 min. Therefore, the chain transfer agent dosage is 1.5–4 mL, preferably 1.5 mL.

[0082] ⑦ Effect of pH value

[0083] To investigate the effect of pH on polymerization performance, the pH during polymerization was changed to 2, 4, 6, 8, 10, and 12, and the formulations are shown in Table 7 below:

[0084] Table 7 Effect of pH on polymer solubility and viscosity

[0085]

[0086] The amount of cosolvent added was 1 mL, the amount of chain transfer agent added was 1.5 mL, the amount of surfactant added was 25 g, BPO was 0.5 g, OP-10 emulsifier was 3 g, urea was 5 g, tert-butyl hydroperoxide (0.5%) was 0.5 mL, VA044 (1%) was 3.5 mL, sodium metabisulfite (1%) was 1 mL, ferrous ammonium sulfate (1 wt%) was 0.1 mL, and the reaction temperature was 25℃.

[0087] Experimental results show that as the pH increases from 2 to 12 during polymerization, the polymer dissolves faster, but the viscosity gradually decreases. This is because: under acidic conditions, cross-linking reactions easily occur between polymer chains, leading to polymer insolubility; under strongly alkaline conditions, the amide portion of monomer M undergoes hydrolysis, reducing polymer viscosity. Therefore, the optimal pH for polymerization is approximately 2–12, preferably 8.

[0088] ⑧ Effect of reaction time

[0089] To investigate the effect of reaction time on polymerization performance, the reaction time was varied to 3 h, 6 h, 9 h, 12 h, and 15 h, and the formulations are shown in Table 8 below:

[0090] Table 8. Effect of reaction time on polymer solubility and viscosity.

[0091]

[0092] The following ingredients were added: 1 mL of cosolvent, 1.5 mL of chain transfer agent, 25 g of surfactant, 0.5 g of BPO, 3 g of emulsifier OP-10, 5 g of urea, 0.5 mL of tert-butyl hydroperoxide (0.5%), 3.5 mL of VA044 (1%), 1 mL of sodium metabisulfite (1%), 0.1 mL of ferrous ammonium sulfate (1 wt%), pH 8, and reaction temperature 25℃.

[0093] Experimental results show that as the polymerization time increases from 3 h to 15 h, the polymer dissolution rate slows down, but the viscosity gradually increases. This is because: at shorter reaction times, the polymer cannot form clumps or the clumps are softer, resulting in a lower molecular weight and thus a faster dissolution rate but lower viscosity; when the reaction time is extended to over 12 h, the polymer clumps become more elastic, have a higher molecular weight, and therefore the dissolution rate slows down, but the viscosity is higher, reaching over 50 mPa·s. Therefore, to ensure a more complete reaction and obtain a high molecular weight functional polymer, the polymerization time should be between 8 and 16 h, preferably 12 h.

[0094] 9. The effect of temperature

[0095] To investigate the effect of temperature on polymer properties, the initiation temperature during polymerization was varied to 0, 10, 20, 30, and 40 °C, and the formulations are shown in Table 9 below:

[0096] Table 9. Effects of temperature on polymer solubility and viscosity.

[0097]

[0098] The amount of solubilizer added is 1 mL, chain transfer agent added is 1.5 mL, surfactant added is 25 g, BPO is 0.5 g, emulsifier OP-10 is 3 g, urea is 5 g, hydrogen peroxide tert-butyl (0.5%) is 0.5 mL, VA044 (1%) is 3.5 mL, sodium metabisulfite (1%) is 1 mL, ferrous ammonium sulfate (1 wt%) is 0.1 mL, and pH is 8.

[0099] Experimental results show that as the polymerization temperature increases from 25°C to 40°C, the polymer dissolution rate increases, but the viscosity gradually decreases. This is because at room temperature (25°C), the gel effect during free radical polymerization of the monomers is weak. As initiation proceeds and the temperature gradually increases, the molecular weight increases slowly, resulting in a polymer with high viscosity. However, as the initiation temperature gradually increases, the gel effect of the polymer intensifies, causing the polymer molecular weight to be lower than that at room temperature. Therefore, the polymer viscosity decreases, but the dissolution rate increases. Therefore, to obtain a high-viscosity polymer, an initial initiation temperature of 0–40°C should be selected, preferably 25°C.

[0100] Example 1

[0101] Weigh 184g AM, 15g AMPS, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant (Tween 20), 5g urea, 1.5mL chain transfer agent (acetone), and 1mL cosolvent (propylene glycol) sequentially. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to thicken, stop the N2 flow and allow the reaction to stand until the system reaches its peak temperature. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 20 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 10.3 mPa·s.

[0102] Example 2

[0103] Weigh 184g AM, 15g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 70 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 44.5 mPa·s.

[0104] Example 3

[0105] Weigh 184g AM, 30g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to thicken, stop the N2 flow and allow the reaction to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 65 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 47.3 mPa·s.

[0106] Example 4

[0107] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of aging, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 60 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 55.2 mPa·s.

[0108] Example 5

[0109] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 15g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to thicken, stop the N2 flow and allow the reaction to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 65 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 34.2 mPa·s.

[0110] Example 6

[0111] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 5g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of aging, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 70 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 15.6 mPa·s.

[0112] Example 7

[0113] Weigh 184g AM, 60g AMPS, 70g AA, and 10g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of aging, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 125 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 99.1 mPa·s.

[0114] Example 8

[0115] Weigh 184g AM, 60g AMPS, 70g AA, and 2g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 25 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 9.8 mPa·s.

[0116] Example 9

[0117] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 2.5mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 45 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 52.1 mPa·s.

[0118] Example 10

[0119] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 5mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of aging, an elastic gel block is obtained. After granulation, drying, pulverization, and sieving, a polymer dry powder is obtained. The polymer dissolves in 9374 mg / L brine at 45°C in 25 minutes. At 75°C, in 35000 mg / L brine, the viscosity of a 1750 mg / L polymer solution is 35.1 mPa·s.

[0120] Example 11

[0121] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 2.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15min, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to thicken, stop the N2 flow and allow the reaction to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 35 minutes. At 75°C, the viscosity of a 1750 mg / L polymer solution in 35000 mg / L brine is 56.5 mPa·s.

[0122] Example 12

[0123] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 4mL chain transfer agent, and 1mL cosolvent sequentially. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer to a reactor, and adjust the temperature to 25℃ for polymerization. After introducing high-purity N2 for approximately 15 minutes, add 0.5g of peroxide initiator BPO and 3.5mL of azo initiator VA044 solution (1wt%). Next, add 0.5mL of redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL of sodium metabisulfite (1wt%). Finally, add 0.1mL of ferrous ammonium sulfate (1wt%). Stop introducing N2 when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic gel block is obtained. After granulation, drying, pulverization, and sieving, the polymer powder was obtained. The polymer dissolved in 9374 mg / L brine at 45℃ for 25 min, and the polymer solution with a concentration of 1750 mg / L in 35000 mg / L brine at 75℃ had a viscosity of 41.0 mPa·s.

[0124] Example 13

[0125] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent sequentially. Adjust the pH of the solution to 2 using NaOH solution (30wt%). Transfer the solution to a reactor and adjust the temperature to 25℃ for polymerization. After introducing high-purity N2 for approximately 15 minutes, add 0.5g of peroxide initiator BPO and 3.5mL of azo initiator VA044 solution (1wt%). Next, add 0.5mL of redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL of sodium metabisulfite (1wt%). Finally, add 0.1mL of ferrous ammonium sulfate (1wt%). Stop introducing N2 when the solution begins to become viscous and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic gel block is obtained. After granulation, drying, pulverization, and sieving, a polymer powder was obtained. The obtained polymer was insoluble in both pure water and 9374 mg / L saline solution.

[0126] Example 14

[0127] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 10 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to thicken, stop the N2 flow and allow the reaction to stand until the system reaches its peak temperature. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 40 minutes. At 75°C, in 35000 mg / L brine, a polymer solution with a concentration of 1750 mg / L has a viscosity of 49.2 mPa·s.

[0128] Example 15

[0129] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 1.5mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 12 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 12 hours of curing, an elastic gel block is obtained. This block is then granulated, dried, pulverized, and sieved to obtain a polymer powder. The polymer dissolves in 9374 mg / L brine at 45°C in 35 minutes. At 75°C, the viscosity of a 1750 mg / L polymer solution in 35000 mg / L brine is 37.1 mPa·s.

[0130] Example 16

[0131] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 4mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After aging for approximately 3 hours, a viscous polymer block is obtained. After granulation, drying, pulverization, and sieving, a polymer powder is obtained. The polymer dissolves in 9374 mg / L brine at 45°C in 10 minutes. At 75°C, in 35000 mg / L brine, the viscosity of a 1750 mg / L polymer solution is 6.4 mPa·s.

[0132] Example 17

[0133] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction is 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 4mL chain transfer agent, and 1mL cosolvent. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer it to a reactor, adjust the temperature to 25℃, and proceed with polymerization. After introducing high-purity N2 for about 15 minutes, add 0.5g peroxide initiator BPO and 3.5mL azo initiator VA044 solution (1wt%). Then, add 0.5mL redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL sodium metabisulfite (1wt%). Finally, add 0.1mL ferrous ammonium sulfate (1wt%). Once the solution begins to become viscous, the N2 flow is stopped, and the reaction is allowed to stand until the system temperature reaches its peak. After approximately 9 hours of aging, a relatively soft polymer block is obtained. After granulation, drying, pulverization, and sieving, a polymer powder is obtained. The polymer dissolves in 9374 mg / L brine at 45°C in 25 minutes. At 75°C, in 35000 mg / L brine, the viscosity of a 1750 mg / L polymer solution is 36.1 mPa·s.

[0134] Example 18

[0135] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 4mL chain transfer agent, and 1mL cosolvent sequentially. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer to a reactor, and adjust the temperature to 20℃ for polymerization. After introducing high-purity N2 for approximately 15 minutes, add 0.5g of peroxide initiator BPO and 3.5mL of azo initiator VA044 solution (1wt%). Next, add 0.5mL of redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL of sodium metabisulfite (1wt%). Finally, add 0.1mL of ferrous ammonium sulfate (1wt%). Stop the N2 flow when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic gel block is obtained. After granulation, drying, pulverization, and sieving, the polymer powder was obtained. The polymer dissolved in 9374 mg / L brine at 45℃ for 30 min, and the viscosity of the polymer solution at 1750 mg / L in 35000 mg / L brine at 75℃ was 32.6 mPa·s.

[0136] Example 19

[0137] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier OP-10, 25g surfactant, 5g urea, 4mL chain transfer agent, and 1mL cosolvent sequentially. Adjust the pH of the solution to 8.0 with NaOH solution (30wt%), transfer to a reactor, and adjust the temperature to 40℃ for polymerization. After introducing high-purity N2 for approximately 15 minutes, add 0.5g of peroxide initiator BPO and 3.5mL of azo initiator VA044 solution (1wt%). Next, add 0.5mL of redox initiator tert-butyl hydroperoxide (0.5wt%) and 1mL of sodium metabisulfite (1wt%). Finally, add 0.1mL of ferrous ammonium sulfate (1wt%). Stop introducing N2 when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic gel block is obtained. After granulation, drying, pulverization, and sieving, the polymer powder was obtained. The polymer dissolved in 9374 mg / L brine at 45℃ for 30 min, and the viscosity of the polymer solution at 1750 mg / L in 35000 mg / L brine at 75℃ was 11.3 mPa·s.

[0138] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An emulsified, temperature-resistant, and salt-resistant polyacrylamide, characterized in that: The structural formula of polyacrylamide is as follows: In the formula, x, y, z, and p are the molar numbers of structural units of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and N-octadecylacrylamide, respectively, and x:y:z:p = (20~1000):(20~1000):(20~1000):(20~1000). The preparation method of polyacrylamide includes the following steps: S1. Mixing acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and N-octadecylacrylamide with deionized water, waiting... After complete dissolution, acrylamide is added. The mass ratio of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and N-octadecylacrylamide is 92:(25~40):(15~35):(1~4); S2. Emulsifier, surfactant, urea, chain transfer agent, and cosolvent are added sequentially; S3. The pH of the solution is adjusted to 6, 7.8~8.0, 10, or 12; S4. The temperature is adjusted to 20~40℃, and nitrogen gas is introduced; S5. Initiator and reducing agent are added, and the reaction is carried out for 8 h~16 h; S6. After the reaction is completed, the gel block is granulated, dried, and pulverized to obtain emulsified temperature-resistant and salt-resistant polyacrylamide.

2. The emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 1, characterized in that: The viscosity-average molecular weight of polyacrylamide is 5 million to 15 million, and the anionic content is 5% to 45%.

3. A method for preparing the emulsified, temperature-resistant, and salt-resistant polyacrylamide as described in claim 1 or 2, characterized in that: Includes the following steps: S1. Mix acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and N-octadecylacrylamide with deionized water. After complete dissolution, add acrylamide. The mass ratio of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and N-octadecylacrylamide is 92:(25~40):(15~35):(1~4). S2. Add emulsifier, surfactant, urea, chain transfer agent, and cosolvent in sequence. S3. Adjust the pH of the solution to 6, 7.8~8.0, 10, or 12. S4. Adjust the temperature to 20~40℃ and purge with nitrogen. S5. Add initiator and reducing agent, and react for 8~16 h. S6. After the reaction is complete, granulate, dry, and pulverize the gel block to obtain emulsified, temperature-resistant, and salt-resistant polyacrylamide.

4. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 3, characterized in that: In step S1, the monomer concentration is 15%-35%.

5. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 3, characterized in that: In step S2, the emulsifier is OP-10, and the mass ratio of emulsifier to acrylamide is (0.5~3):184; the surfactant is Tween 20, and the mass ratio of surfactant to acrylamide is (10~15):92; the chain transfer agent is acetone, and the mass-volume ratio of acrylamide to chain transfer agent is 46-122.67 g / ml; the cosolvent is propylene glycol, and the mass-volume ratio of acrylamide to cosolvent is 61.33-184 g / ml; and the mass ratio of urea to acrylamide is (5~10):

184.

6. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 3, characterized in that: In step S3, the pH of the solution is adjusted using NaOH solution, with a mass fraction of 20-40%.

7. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 3, characterized in that: In step S4, the nitrogen gas is introduced for 20-40 minutes.

8. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 3, characterized in that: In step S5, the amount of initiator added is 0.2‰~0.5‰ of the total mass of the monomers; the initiator is a composite initiation system, including benzoyl peroxide, N-diisopropylimidazoline hydrochloride, tert-butyl hydroperoxide, and sodium metabisulfite, with a mass ratio of (1~1.5):(1.5~2):(2~3.5):(3~4.5).

9. The preparation method of emulsified, temperature-resistant, and salt-resistant polyacrylamide according to claim 8, characterized in that: In step S5, the reducing agent is ferrous ammonium sulfate, and the amount of ferrous ammonium sulfate added is 0.2 to 0.5 times the mass of tert-butyl hydrogen peroxide.

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