A salt-sensitive polyacrylamide dry powder granule and a polyacrylamide suspension comprising the same

Abstract

The application provides a salt-sensitive polyacrylamide dry powder particle and a polyacrylamide suspension containing the same. In the application, a functional monomer containing a salt-sensitive side chain is introduced onto a polyacrylamide molecule through a copolymerization reaction to obtain a polyacrylamide dry powder particle; wherein the functional monomer has the following structural formula, wherein n is an integer of 4-20. The obtained polyacrylamide dry powder particle can exhibit good water solubility in water with a mineralization degree of less than 50000 mg / L, does not affect the dissolution speed thereof in the application process, and exhibits a non-water-soluble characteristic when the mineralization degree reaches 150000 mg / L or more, so that the polyacrylamide dry powder particle can be stably suspended in water. Therefore, a suspension prepared by using the polyacrylamide dry powder particle can replace oil in a continuous phase with water, meets the application requirement, obviously reduces the use cost, and improves the green environmental protection of the product.

Description

Technical Field

[0001] This invention belongs to the field of water-soluble polymers, specifically including a salt-sensitive polyacrylamide dry powder granules and a polyacrylamide suspension containing the same. Background Technology

[0002] With the large-scale exploitation of shale oil and shale gas, large-volume fracturing technology using slickwater as fracturing fluid has been widely used because it can more effectively improve the permeability and conductivity of shale oil and gas reservoirs. Drag-reducing agents, as the core additives of slickwater fracturing fluid systems, directly determine the fracturing operation effect.

[0003] Currently, most high-performance drag-reducing agents use acrylamide polymers. To meet the requirements of large-volume fracturing, drag-reducing agents must be added online, which places extremely high demands on dissolution speed. Generally, complete dissolution is achieved within <30 seconds of addition; therefore, emulsion-type polyacrylamide has become the best choice. With the improvement of polyacrylamide dry powder preparation technology and the emergence of suspension technology, polyacrylamide dry powder can be prepared into a suspension with oil as the continuous phase, which can also ensure the requirements of online construction. For example, Chinese invention patent CN202210873789.6 describes an integrated thickener for fracturing and its preparation method. The thickener comprises the following components by weight percentage: 40-55% modified acrylamide polymer, 1-2% suspending agent, and 50-58% organic solvent. It eliminates the need for additional fracturing demulsifier and flow aid during use, simplifying the agent addition process and increasing the economic benefits for the operator. Chinese invention patent CN202110905455.8 describes a thickener suspension emulsion for fracturing fluid and its preparation method. The method includes: sequentially adding polyacrylamide powder, an anti-sticking agent, and a surfactant to a ball mill, and milling them to obtain a mixed powder; sequentially adding a first suspending agent, a second suspending agent, an anti-settling agent, and a structure modifier to a reactor and stirring to obtain a mixed solution; and sequentially adding the mixed powder and an emulsifier to the mixed solution and stirring to obtain the thickener suspension emulsion. The obtained thickener suspension emulsion exhibits superior solubility and higher stability, making it suitable for continuous mixing and high-volume fracturing operations. However, with the increase in oil prices, the cost of suspension fracturing operations using oil as the continuous phase also increases accordingly. While replacing the oil in the continuous phase with water would significantly reduce costs, polyacrylamide, as a water-soluble polymer, has excellent solubility in water, especially products prepared for slickwater fracturing, which dissolves even faster and may not meet application requirements.

[0004] Therefore, it is necessary to prepare a specially modified polyacrylamide dry powder granule that can be used to prepare aqueous suspensions that meet application requirements. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the first objective of this invention is to provide a salt-sensitive polyacrylamide dry powder granule. In this invention, by introducing a salt-sensitive side chain into the polyacrylamide structure, the resulting polyacrylamide dry powder granules achieve good water solubility in water with a mineralization level below 50,000 mg / L, and stability and insolubility in water with a mineralization level above 150,000 mg / L. Therefore, when using this polyacrylamide dry powder granule to prepare suspensions, the oil in the continuous phase can be replaced with water, meeting application requirements (complete dissolution within <30 seconds of addition) while also reducing usage costs and improving the product's environmental friendliness.

[0006] The second objective of this invention is to provide a method for preparing the salt-sensitive polyacrylamide dry powder particles as described above.

[0007] A third objective of this invention is to provide a polyacrylamide suspension comprising the salt-sensitive polyacrylamide dry powder particles as described above.

[0008] A fourth objective of this invention is to provide a method for preparing the polyacrylamide suspension as described above.

[0009] The fifth objective of this invention is to provide an application of the polyacrylamide suspension described above in the extraction of shale oil and shale gas.

[0010] To achieve the first objective mentioned above, the technical solution adopted by the present invention includes:

[0011] This invention discloses a salt-sensitive polyacrylamide dry powder granules, which introduces functional monomers containing salt-sensitive side chains into polyacrylamide molecules through a copolymerization reaction, thereby achieving structural modification of polyacrylamide and finally obtaining the polyacrylamide dry powder granules.

[0012] The structural formula of the functional unit is as follows:

[0013]

[0014] Where n takes the value of an integer between 4 and 20.

[0015] Furthermore, in order to prepare a stable and uniform suspension of polyacrylamide dry powder particles in the subsequent process, it is advisable to control the amount of polyacrylamide dry powder particles with a mesh size of 60 mesh or higher to no more than 5 wt%.

[0016] Furthermore, the functional monomer is prepared according to the following steps:

[0017] The product is obtained by reacting N,N-dimethylaminopropylacrylamide with ethylene oxide under heating conditions. By controlling the ratio of the two, products with different n values ​​can be obtained. The specific reaction equation is as follows:

[0018]

[0019] To achieve the second objective mentioned above, the technical solution adopted by the present invention includes:

[0020] This invention discloses a method for preparing the polyacrylamide dry powder particles as described above, comprising the following steps:

[0021] Acrylamide, comonomers and functional monomers are dissolved in water, the pH of the system is adjusted to 6-8 and the temperature is lowered to 0-15℃, an initiator is added to the water in an anaerobic environment to initiate the reaction, and a colloid is obtained after the reaction is completed. The colloid is then extruded, granulated, dried and pulverized to obtain the final product.

[0022] Furthermore, the amount of the functional monomer added accounts for 0.1-10 wt% of the sum of the amounts of acrylamide, comonomer, and functional monomer. For example, the amount of the functional monomer added is 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, etc., of the sum of the amounts of acrylamide, comonomer, and functional monomer.

[0023] Furthermore, the comonomer is a selectively added polymeric monomer, and its addition amount is 0-70 wt% of the sum of the acrylamide, comonomer and functional monomer. For example, its addition amount is 0 wt% (no addition), 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt% or 70 wt% of the sum of the acrylamide, comonomer and functional monomer, etc.

[0024] Furthermore, the total concentration of the acrylamide, comonomer, and functional monomer in water is 15-40 wt%. For example, the total concentration of the acrylamide, comonomer, and functional monomer in water can be 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, etc.

[0025] Furthermore, the comonomers include, but are not limited to, one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid, methylallylsulfonic acid, and vinylbenzenesulfonic acid.

[0026] Furthermore, the initiator can be an oxidizing initiator or a reducing initiator. Exemplarily, the oxidizing initiator includes, but is not limited to, one or more of persulfate, hydrogen peroxide, and tert-butyl hydrogen peroxide; the reducing initiator includes, but is not limited to, one or more of bisulfite, sulfite, ferrous salt, thiosulfate, metabisulfite, and tertiary amine. The amount of the initiator added is 0.001-0.1 wt% of the total amount of acrylamide, comonomer, and functional monomer.

[0027] To achieve the third objective mentioned above, the technical solution adopted by the present invention includes:

[0028] This invention discloses a polyacrylamide suspension comprising polyacrylamide dry powder particles as described above, comprising the following raw materials in weight percentages:

[0029] Polyacrylamide dry powder granules 5-35wt%;

[0030] Suspension agent 0.01-10 wt%;

[0031] Water-soluble salts 10-50 wt%;

[0032] Alcohol solvents 0-20 wt%;

[0033] The rest is water.

[0034] Furthermore, the suspending agent is selected from commonly used suspending agents in the art, such as water-soluble polymers, aqueous anti-settling thixotropic agents, etc. The water-soluble polymers include, but are not limited to, homopolymers or copolymers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, methyl allylsulfonic acid, tert-butylacrylamide, etc., or natural polymers or modified natural polymers, such as cellulose, xanthan gum, carboxymethyl cellulose, hydroxyethyl cellulose, modified starch, etc. The aqueous anti-settling thixotropic agent includes, but is not limited to, polyamide wax, modified polyamide salts, waterborne polyurethane resins, fumed silica, pore stone powder, etc.

[0035] Furthermore, the water-soluble salt can be an inorganic salt or an organic salt, including but not limited to sodium salts, potassium salts, ammonium salts, magnesium salts, calcium salts, barium salts, aluminum salts, etc. For example, the water-soluble salt can be sodium chloride, sodium sulfate, sodium formate, sodium acetate, potassium chloride, potassium sulfate, potassium formate, ammonium chloride, ammonium sulfate, calcium chloride, magnesium chloride, aluminum chloride, etc.

[0036] Furthermore, alcohol solvents may be selectively added based on the solubility state of the mixed raw materials to ensure that each raw material is fully dissolved. The alcohols include, but are not limited to, one or more of methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerol, and polyethylene glycol.

[0037] To achieve the fourth objective mentioned above, the technical solution adopted by the present invention includes:

[0038] This invention discloses a method for preparing the polyacrylamide suspension as described above, comprising the following steps:

[0039] Dissolve water-soluble salts in water, keep the temperature constant at 20-30℃, add a suspending agent, with or without adding alcohol solvent, stir evenly, and then add polyacrylamide dry powder particles to obtain a polyacrylamide suspension.

[0040] To achieve the fifth objective mentioned above, the technical solution adopted by the present invention includes:

[0041] This invention discloses an application of the polyacrylamide suspension described above in the extraction of shale oil and shale gas.

[0042] Beneficial effects of this invention:

[0043] This invention provides a salt-sensitive polyacrylamide dry powder granules and a polyacrylamide suspension containing the same. The polyacrylamide dry powder granules incorporate salt-sensitive side chains in their structure, achieving good water solubility in water with a salinity below 50,000 mg / L and stability and insolubility in water with a salinity above 150,000 mg / L. Therefore, using these polyacrylamide dry powder granules to prepare polyacrylamide suspensions for shale oil and shale gas extraction allows for the replacement of the continuous phase oil with water, meeting application requirements (complete dissolution within <30 seconds of addition) while reducing usage costs and improving the product's environmental friendliness. Detailed Implementation

[0044] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] Preparation of salt-sensitive functional monomers:

[0047] 156 kg of N,N-dimethylaminopropylacrylamide, 100 kg of hydrochloric acid, and 1 kg of p-hydroxyanisole were added to a 1 cubic meter reactor. The mixture was stirred, and 176 kg of ethylene oxide was slowly added. The mixture was heated to 95°C, and the reactor was sealed and reacted for 2 hours. After the reaction was completed, the water was removed under reduced pressure to obtain a pale yellow viscous liquid. The obtained salt-sensitive functional monomer is shown in Formula I.

[0048]

[0049] Preparation of polyacrylamide dry powder granules:

[0050] Add 7173 kg of water to a 10 cubic meter mixing vessel, and while stirring, add 2000 kg of acrylamide, 500 kg of acrylic acid, 277 kg of sodium hydroxide, and 50 kg of salt-sensitive functional monomer in sequence. Adjust the pH of the system to 7.0, cool to 3°C, transfer to a reaction vessel, purge with nitrogen for 30 minutes, and then add 100 g of ammonium persulfate (dissolved in 1000 g of water) and 800 g of sodium bisulfite (dissolved in 4000 g of water) in sequence. After the system thickens, continue purging with nitrogen for 5 minutes, seal the reaction vessel and react for about 3 hours, then naturally heat to 65-75°C and keep at that temperature for 2 hours. After the reaction is complete, extrude the colloidal material in the reaction vessel to granulate, and then transport it to a drying device for drying. After drying, pulverize and sieve, collect particles smaller than 60 mesh and package them, ensuring that the polyacrylamide dry powder particles with a mesh size greater than 60 mesh are controlled to be no more than 5 wt%.

[0051] The technical specifications of the product are shown in Table 1, and the viscosity is determined by the following method:

[0052] The instrument used was a 6-speed rotational viscometer with a reading of 300 rpm;

[0053] The polyacrylamide dry powder granules were dissolved in 400 ml of test water (including water containing 2% potassium chloride, tap water, or water containing 15% ammonium sulfate), with a stirring speed of 1000 rpm and a dissolution time of 3 min. The concentration of the polyacrylamide dry powder granules was 1800 ppm.

[0054] Table 1 Technical Specifications of Polyacrylamide Granules

[0055]

[0056]

[0057] Preparation of aqueous suspensions:

[0058] Add 2400 kg of water and 1600 kg of ammonium sulfate to a 5 cubic meter batching vessel, stir and dissolve, then control the temperature at 25°C. Add 80 kg of poly(N-vinylpyrrolidone) and stir and dissolve until a uniform solution is formed. Add 1000 kg of the above-mentioned polyacrylamide dry powder granules and continue stirring until all the polyacrylamide granules are dispersed to form a uniform suspension. Then, pack the solution into a ton container.

[0059] Example 2

[0060] Preparation of salt-sensitive functional monomers:

[0061] 156 kg of N,N-dimethylaminopropylacrylamide, 100 kg of hydrochloric acid, and 1 kg of p-hydroxyanisole were added to a 1 cubic meter reactor. The mixture was stirred, and 660 kg of ethylene oxide was slowly added. The mixture was heated to 95°C, and the reactor was sealed and reacted for 2 hours. After the reaction was completed, the water was removed under reduced pressure to obtain a pale yellow viscous liquid. The obtained salt-sensitive functional monomer is shown in Formula II.

[0062]

[0063] Preparation of polyacrylamide dry powder granules:

[0064] Add 6865 kg of water to a 10 cubic meter mixing vessel. While stirring, add 1900 kg of acrylamide, 500 kg of acrylic acid, 300 kg of 2-acrylamido-2-methylpropanesulfonic acid, 335 kg of sodium hydroxide, and 150 kg of salt-sensitive functional monomer in sequence. Adjust the pH of the system to 8.0, cool to 10°C, transfer to a reaction vessel, purge with nitrogen for 30 minutes, then add 500 g of hydrogen peroxide (dissolved in 3000 g of water) and 100 g of ferrous sulfate heptahydrate (dissolved in 1000 g of water) in sequence. After the system thickens, continue purging with nitrogen for 5 minutes. Seal the reaction vessel and react for about 4 hours. Naturally raise the temperature to 65-75°C and keep it at that temperature for 2 hours. After the reaction is complete, extrude the colloidal material in the reaction vessel to granulate, and then transport it to a drying device for drying. After drying, pulverize and sieve, collect particles smaller than 60 mesh and package them, ensuring that the polyacrylamide dry powder particles with a mesh size greater than 60 mesh are controlled to be no more than 5 wt%.

[0065] The technical specifications of the product are shown in Table 2, and the viscosity is determined by the following method:

[0066] The instrument used was a 6-speed rotational viscometer with a reading of 300 rpm;

[0067] The polyacrylamide dry powder granules were dissolved in 400 ml of test water (including water containing 2% potassium chloride, tap water, or water containing 15% ammonium sulfate), with a stirring speed of 1000 rpm and a dissolution time of 3 min. The concentration of the polyacrylamide dry powder granules was 1800 ppm.

[0068] Table 2 Technical Specifications of Polyacrylamide Particles

[0069] project index <![CDATA[Molecular weight (×10 4 )]]> 2010 Degree of hydrolysis (%) 17.5 Viscosity (mPa·s) in water containing 2% potassium chloride 12 Viscosity of tap water (mPa.s) 26 Viscosity (mPa·s) in a solution containing 15% ammonium sulfate 1.3

[0070] Preparation of aqueous suspensions:

[0071] Add 2400 kg of water and 1300 kg of calcium chloride to a 5 cubic meter mixing tank, stir and dissolve, then control the temperature at 30°C. Add 120 kg of xanthan gum and stir until dissolved into a uniform solution. Add 300 kg of ethanol and stir until uniform. Add 1600 kg of the above-mentioned polyacrylamide dry powder granules and continue stirring until all polyacrylamide granules are dispersed to form a uniform suspension. Pour the solution into a ton container.

[0072] Example 3

[0073] Preparation of salt-sensitive functional monomers:

[0074] 156 kg of N,N-dimethylaminopropylacrylamide, 100 kg of hydrochloric acid, and 1 kg of p-hydroxyanisole were added to a 1 cubic meter reactor. The mixture was stirred, and 440 kg of ethylene oxide was slowly added. The mixture was heated to 95°C, and the reactor was sealed and reacted for 2 hours. After the reaction was completed, the water was removed under reduced pressure to obtain a pale yellow viscous liquid. The obtained salt-sensitive functional monomer is shown in Formula III.

[0075]

[0076] Preparation of polyacrylamide dry powder granules:

[0077] Add 6435 kg of water to a 10 cubic meter mixing vessel. While stirring, add 1900 kg of acrylamide, 600 kg of acrylic acid, 200 kg of 2-acrylamido-2-methylpropanesulfonic acid, 200 kg of methacrylic acid, 465 kg of sodium hydroxide, and 200 kg of salt-sensitive functional monomers in sequence. Adjust the pH of the system to 6.0, cool to 5°C, transfer to a reaction vessel, purge with nitrogen for 30 minutes, and then add 300 g of tert-butyl hydroperoxide (dissolved in 1000 g of water) and heptahydrate sulfur. 100g of ferrous sulfate (dissolved in 1000g of water) and 200g of sodium metabisulfite (dissolved in 1000g of water) are added. After the system thickens, nitrogen gas is continuously purged for 5 minutes. The system is then sealed and reacted for about 3 hours. The temperature is naturally raised to 65-75℃ and maintained for 2 hours. After the reaction is completed, the colloidal material in the reactor is extruded and granulated, and then transported to a drying device for drying. After drying, the material is crushed and sieved, and particles smaller than 60 mesh are collected and packaged. The particle size of polyacrylamide dry powder with a mesh size greater than 60 mesh is controlled to be no more than 5 wt%.

[0078] The technical specifications of the product are shown in Table 3, among which the viscosity is determined by:

[0079] The instrument used was a 6-speed rotational viscometer with a reading of 300 rpm;

[0080] The polyacrylamide dry powder granules were dissolved in 400 ml of test water (including water containing 2% potassium chloride, tap water, or water containing 15% ammonium sulfate), with a stirring speed of 1000 rpm and a dissolution time of 3 min. The concentration of the polyacrylamide dry powder granules was 1800 ppm.

[0081] Table 3 Technical Specifications of Polyacrylamide Particles

[0082] project index <![CDATA[Molecular weight (×10 4 )]]> 1600 Degree of hydrolysis (%) 25.8 Viscosity (mPa·s) in water containing 2% potassium chloride 8 Viscosity of tap water (mPa.s) 22 Viscosity (mPa·s) in a solution containing 15% ammonium sulfate 1.1

[0083] Preparation of aqueous suspensions:

[0084] Add 2600 kg of water and 1500 kg of magnesium chloride to a 5 cubic meter batching vessel, stir and dissolve, then control the temperature at 20°C. Add 50 kg of fumed silica and stir and dissolve until a uniform solution is formed. Add 800 kg of the above-mentioned polyacrylamide dry powder granules and continue stirring until all the polyacrylamide granules are dispersed to form a uniform suspension. Then, pour the solution into a ton container.

[0085] Example 4

[0086] Preparation of salt-sensitive functional monomers:

[0087] 156 kg of N,N-dimethylaminopropylacrylamide, 100 kg of hydrochloric acid, and 1 kg of p-hydroxyanisole were added to a 1 cubic meter reactor. The mixture was stirred, and 880 kg of ethylene oxide was slowly added. The mixture was heated to 95°C, and the reactor was sealed and reacted for 2 hours. After the reaction was completed, the water was removed under reduced pressure to obtain a pale yellow viscous liquid. The obtained salt-sensitive functional monomer is shown in Formula IV.

[0088]

[0089] Preparation of polyacrylamide dry powder granules:

[0090] Add 7690 kg of water to a 10 cubic meter mixing vessel. While stirring, add 1100 kg of acrylamide, 700 kg of acrylic acid, 100 kg of 2-acrylamido-2-methylpropanesulfonic acid, 408 kg of sodium hydroxide, and 210 kg of salt-sensitive functional monomer in sequence. Adjust the pH of the system to 7.5, cool to 15°C, transfer to a reaction vessel, purge with nitrogen for 30 minutes, and then add 400 g of sodium persulfate (dissolved in 2000 g of water) and 200 g of sodium thiosulfate (dissolved in 1000 g of water) in sequence. After the system thickens, continue to purge with nitrogen for 5 minutes. Seal the system and react for about 5 hours. Naturally raise the temperature to 65-75°C and keep it at that temperature for 2 hours. After the reaction is complete, extrude the colloidal material in the reaction vessel to granulate, and then transport it to a drying device for drying. After drying, crush and sieve the material, collect the particles smaller than 60 mesh, and package them to ensure that the polyacrylamide dry powder particles with a mesh size greater than 60 mesh are controlled to be no more than 5 wt%.

[0091] The technical specifications of the product are shown in Table 4, and the viscosity is determined by the following method:

[0092] The instrument used was a 6-speed rotational viscometer with a reading of 300 rpm;

[0093] The polyacrylamide dry powder granules were dissolved in 400 ml of test water (including water containing 2% potassium chloride, tap water, or water containing 15% ammonium sulfate), with a stirring speed of 1000 rpm and a dissolution time of 3 min. The concentration of the polyacrylamide dry powder granules was 1800 ppm.

[0094] Table 4 Technical Specifications of Polyacrylamide Particles

[0095] project index <![CDATA[Molecular weight (×10 4 )]]> 2200 Degree of hydrolysis (%) 33.2 Viscosity (mPa·s) in water containing 2% potassium chloride 15 Viscosity of tap water (mPa.s) 31 Viscosity (mPa·s) in a solution containing 15% ammonium sulfate 1

[0096] Preparation of aqueous suspensions:

[0097] Add 3000 kg of water, 500 kg of sodium chloride, and 1000 kg of calcium chloride to a 5 cubic meter batching vessel. Stir and dissolve the mixture, then control the temperature at 25°C. Add 200 kg of polyamide wax and stir until dissolved into a uniform solution. Add 1800 kg of the above-mentioned polyacrylamide dry powder granules and continue stirring until all the polyacrylamide granules are dispersed to form a uniform suspension. Pour the solution into a ton container.

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A salt-sensitive polyacrylamide dry powder granule, characterized in that, A functional monomer containing a salt-sensitive side chain is introduced into a polyacrylamide molecule via a copolymerization reaction to obtain the polyacrylamide dry powder particles. The structural formula of the functional unit is as follows: ； Where n takes the value of an integer between 4 and 20.

2. The polyacrylamide dry powder granules according to claim 1, characterized in that, The particle size of polyacrylamide dry powder with a mesh size of 60 or higher shall not exceed 5 wt%.

3. The method for preparing polyacrylamide dry powder granules according to any one of claims 1-2, characterized in that, Includes the following steps: Acrylamide, optionally comonomers and functional monomers are dissolved in water, the pH of the system is adjusted to 6-8 and the temperature is lowered to 0-15℃, an initiator is added to the water in an anaerobic environment to initiate the reaction, and a colloid is obtained after the reaction is completed. The colloid is then extruded, granulated, dried and pulverized to obtain the final product.

4. The preparation method according to claim 3, characterized in that, The amount of the functional monomer added is 0.1-10 wt% of the sum of the amounts of acrylamide, comonomer, and functional monomer.

5. The preparation method according to claim 3, characterized in that, The amount of comonomer added is 0-70 wt% of the sum of the amounts of acrylamide, comonomer, and functional monomer.

6. The preparation method according to claim 3, characterized in that, The total concentration of acrylamide, comonomer, and functional monomer in water is 15-40 wt%.

7. The preparation method according to claim 3, characterized in that, The comonomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid, methylallylsulfonic acid, and vinylbenzenesulfonic acid.

8. A polyacrylamide suspension, characterized in that, Including the following raw materials by weight percentage: 5-35 wt% of the polyacrylamide dry powder particles as described in any one of claims 1-2; Suspension agent 0.01-10 wt%; Water-soluble salts 10-50 wt%; Alcohol solvents 0-20wt% The rest is water.

9. The method for preparing the polyacrylamide suspension as described in claim 8, characterized in that, Includes the following steps: Dissolve water-soluble salts in water, keep the temperature constant at 20-30℃, add a suspending agent, with or without adding alcohol solvent, stir evenly, and then add polyacrylamide dry powder particles to obtain a polyacrylamide suspension.

10. The application of the polyacrylamide suspension as described in claim 8 in the extraction of shale oil and shale gas.

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