Salt-sensitive polyacrylamide dry powder particle and polyacrylamide suspension containing same

Abstract

The invention provides salt-sensitive polyacrylamide dry powder particles and a polyacrylamide suspension containing the salt-sensitive polyacrylamide dry powder particles. The preparation method comprises the following steps: introducing a functional monomer containing a salt-sensitive side chain into polyacrylamide molecules through a copolymerization reaction to obtain polyacrylamide dry powder particles; wherein the structural formula of the functional monomer is shown in the specification, and n is an integer from 4 to 20. The obtained polyacrylamide dry powder particles can show good water solubility in water with the degree of mineralization lower than 50000 mg / L, the dissolution rate of the polyacrylamide dry powder particles in the application process is not affected, meanwhile, when the degree of mineralization reaches 150000 mg / L or above, the polyacrylamide dry powder particles show the non-water-soluble characteristic, so that the polyacrylamide dry powder particles can be stably suspended in water, and the stability of the polyacrylamide dry powder particles is improved. Therefore, the suspension prepared from the polyacrylamide dry powder particles can replace continuous-phase oil with water, so that the application requirements are met, the use cost is obviously reduced, and the green environmental protection property of the product is also improved. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of water-soluble polymers, and specifically comprises salt-sensitive polyacrylamide dry powder particles and a polyacrylamide suspension containing the same. Background Art

[0002] With the large-scale exploitation of shale oil and shale gas, large-volume fracturing technology using slick water as fracturing fluid has been widely used because it can more effectively improve the permeability and conductivity of shale oil and gas layers. Drag reducers, as the core additives of the slick water fracturing fluid system, directly determine the construction effect of fracturing.

[0003] At present, most high-performance drag reducers use acrylamide polymers. In order to meet the requirements of large-volume fracturing, drag reducers must be added online, which has extremely high requirements on the dissolution rate. Generally, it takes less than 30 seconds to achieve complete dissolution after adding, so emulsion polyacrylamide becomes the best choice. With the improvement of polyacrylamide dry powder preparation technology and the emergence of suspension technology, polyacrylamide dry powder is prepared into a suspension with oil as the continuous phase, which can also meet the requirements of online construction. For example, Chinese invention patent CN202210873789.6 describes an integrated thickener for fracturing and its preparation method. The thickener includes the following components in weight percentage: 40-55% modified acrylamide polymer, 1-2% suspending agent, and 50-58% organic solvent. When used, there is no need to add a fracturing demulsification agent, which simplifies the agent filling process and increases the economic benefits of the operator. Chinese invention patent CN202110905455.8 describes a thickener suspension emulsion for fracturing fluid and a preparation method thereof, the method comprising: adding polyacrylamide powder, anti-adhesive agent and surfactant to a ball mill in sequence, and obtaining a mixed powder after ball milling; adding a first suspending agent, a second suspending agent, an anti-precipitation agent and a structure regulator in the reactor in sequence and stirring and mixing to obtain a mixed solution; adding the mixed powder and emulsifier in the mixed solution in sequence and stirring and mixing to obtain the thickener suspension emulsion, and the obtained thickener suspension emulsion has better solubility and higher stability, and is suitable for continuous mixing and large-volume construction. However, with the increase in oil prices, the cost of suspension fracturing construction with oil as the continuous phase has also increased accordingly. Although replacing the oil in the continuous phase with water will greatly reduce the cost of use, polyacrylamide, as a water-soluble polymer, has very good solubility in water, especially the product prepared for slippery water fracturing has a faster dissolution rate, and will not meet the application requirements.

[0004] Therefore, a specially modified polyacrylamide dry powder particle must be prepared so that it can be used to prepare an aqueous suspension that meets application requirements. Summary of the invention

[0005] In view of the above problems existing in the prior art, the first object of the present invention is to provide a salt-sensitive polyacrylamide dry powder particle. In the present invention, after the salt-sensitive side chain is introduced into the polyacrylamide structure, the obtained polyacrylamide dry powder particle achieves good water solubility in water with a mineralization degree lower than 50000 mg / L, and is stable and insoluble in water with a mineralization degree higher than 150000 mg / L. Therefore, when the polyacrylamide dry powder particle is used to prepare a suspension, the oil in the continuous phase can be replaced by water, which meets the application requirements (complete dissolution is achieved after adding <30 seconds) while reducing the use cost and improving the green environmental protection of the product.

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

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

[0008] The fourth object of the present invention is to provide a method for preparing the polyacrylamide suspension as described above.

[0009] The fifth object of the present invention is to provide an application of the polyacrylamide suspension as described above in the exploitation of shale oil and shale gas.

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

[0011] The present invention discloses a salt-sensitive polyacrylamide dry powder particle, wherein a functional monomer containing a salt-sensitive side chain is introduced into a polyacrylamide molecule through a copolymerization reaction, thereby achieving structural modification of the polyacrylamide, and finally obtaining the polyacrylamide dry powder particle;

[0012] Wherein, the structural formula of the functional monomer is

[0013]

[0014] Here, n is an integer between 4 and 20.

[0015] Furthermore, in order to obtain the polyacrylamide dry powder particles and subsequently prepare a stable and uniform suspension, the polyacrylamide dry powder particles with a mesh size of more than 60 meshes are preferably controlled to be no more than 5wt%.

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

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

[0018]

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

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

[0021] The acrylamide, comonomer and functional monomer are dissolved in water, the pH of the system is adjusted to 6-8 and the temperature is lowered to 0-15°C, 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 extruded, granulated, dried and crushed to obtain the final product.

[0022] Further, the amount of the functional monomer added is 0.1-10wt% of the sum of the amounts of acrylamide, comonomers and functional monomers added. Exemplarily, the amount of the functional monomer added is 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt% of the sum of the amounts of acrylamide, comonomers and functional monomers added, etc.

[0023] Further, the comonomer is a selectively added polymerization monomer, and its added amount is 0-70wt% of the sum of the added amounts of acrylamide, comonomers and functional monomers. Exemplarily, its added amount is 0wt% (not added), 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt% or 70wt% of the sum of the added amounts of acrylamide, comonomers and functional monomers, etc.

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

[0025] Furthermore, the comonomer includes, but is not limited to, one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid, methyl allyl sulfonic acid and vinylbenzenesulfonic acid.

[0026] Further, the initiator may be an oxidative initiator or a reductive initiator. For example, the oxidative initiator includes but is not limited to one or more of persulfate, hydrogen peroxide and tert-butyl hydroperoxide, and the reductant includes but is not limited to one or more of bisulfite, sulfite, ferrous salt, thiosulfate, pyrosulfite and tertiary amine. The added amount of the initiator is 0.001-0.1wt% of the total amount of acrylamide, comonomer and functional monomer.

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

[0028] The present invention discloses a polyacrylamide suspension containing the polyacrylamide dry powder particles as described above, comprising the following raw materials in percentage by weight:

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

[0030] Suspending agent 0.01-10wt%;

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

[0032] Alcohol solvent 0-20wt%;

[0033] The rest is water.

[0034] Furthermore, the suspending agent is selected from the suspending agent commonly used in the art, which can be a water-soluble polymer, a water-phase anti-settling thixotropic agent, etc., wherein the water-soluble polymer includes but is not limited to homopolymers or copolymers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl pyrrolidone, methyl allyl sulfonic acid, tert-butyl acrylamide, etc., or a natural polymer or a modified natural polymer, such as cellulose, xanthan gum, carboxymethyl cellulose, hydroxyethyl cellulose, modified starch, etc. The water-phase anti-settling thixotropic agent includes but is not limited to polyamide wax, modified polyamide salt, water-based polyurethane resin, fumed silica, palystone powder, etc.

[0035] Furthermore, the water-soluble salt can be an inorganic salt or an organic salt, including but not limited to sodium salt, potassium salt, ammonium salt, magnesium salt, calcium salt, barium salt, aluminum salt, etc. Exemplarily, 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 according to the dissolution state of the raw materials after mixing to ensure that the raw materials are fully dissolved, and 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, the technical solution adopted by the present invention includes:

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

[0039] Dissolve the water-soluble salt in water, keep the temperature at 20-30°C, add the suspending agent, add or not add the alcohol solvent, stir evenly and then add the polyacrylamide dry powder particles to obtain the polyacrylamide suspension.

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

[0041] The present invention discloses an application of the polyacrylamide suspension as described above in the exploitation of shale oil and shale gas.

[0042] Beneficial effects of the present invention:

[0043] The invention provides a salt-sensitive polyacrylamide dry powder particle and a polyacrylamide suspension containing the same. The polyacrylamide dry powder particle introduces a salt-sensitive side chain in the structure, which can achieve good water solubility in water with a mineralization degree lower than 50000 mg / L, and stability and insolubility in water with a mineralization degree higher than 150000 mg / L. The polyacrylamide dry powder particle is then used to prepare a polyacrylamide suspension used in shale oil and shale gas exploitation, and the oil in the continuous phase can be replaced by water, which meets the application requirements (complete dissolution is achieved after adding for less than 30 seconds), while also reducing the use cost and improving the green environmental protection of the product. DETAILED DESCRIPTION

[0044] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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-dimethylaminopropyl acrylamide, 100 kg of hydrochloric acid and 1 kg of p-hydroxyanisole were added into a 1 cubic reactor, stirred, and 176 kg of ethylene oxide was slowly added. The reaction was heated to 95°C, and the reactor was sealed for reaction for 2 hours. After the reaction was completed, the water was removed under reduced pressure to obtain a light yellow viscous liquid. The obtained salt-sensitive functional monomer is shown in Formula I.

[0048]

[0049] Preparation of polyacrylamide dry powder particles:

[0050] Add 7173kg of water into a 10 cubic batching kettle, add 2000kg of acrylamide, 500kg of acrylic acid, 277kg of sodium hydroxide and 50kg of salt-sensitive functional monomer in sequence under stirring, adjust the pH of the system to 7.0, cool to 3°C, transfer to a reactor, and add 100g of ammonium persulfate (dissolved in 1000g of water) and 800g of sodium bisulfite (dissolved in 4000g of water) in sequence after passing nitrogen for 30min. Continue to pass nitrogen for 5min after the system becomes thick. Close the reactor and react for about 3h to naturally heat to 65-75°C, keep warm for 2h, extrude and granulate the colloidal material in the reactor after the reaction is completed, and transport it to a drying equipment for drying. After drying, crush and screen, collect and package the particles below 60 mesh, and ensure that the polyacrylamide dry powder particles with a mesh size above 60 mesh are controlled to be no more than 5wt%.

[0051] The technical indicators of the product are shown in Table 1, where the viscosity is measured as follows:

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

[0053] Dissolve the polyacrylamide dry powder particles in 400 ml of test water (including water containing 2% potassium chloride, tap water or water containing 15% ammonium sulfate), stir at 1000 rpm, dissolve for 3 minutes, and the concentration of the polyacrylamide dry powder particles is 1800 ppm.

[0054] Table 1 Technical indicators of polyacrylamide particles

[0055]

[0056]

[0057] Preparation of aqueous suspension:

[0058] Add 2400kg of water and 1600kg of ammonium sulfate into a 5 cubic batching kettle, stir and dissolve, control the temperature to 25°C, add 80kg of poly (N-vinyl pyrrolidone), stir and dissolve until a uniform solution is obtained, add 1000kg of the above-mentioned polyacrylamide dry powder particles, continue stirring until all the polyacrylamide particles are dispersed to form a uniform suspension, and then load into a ton barrel.

[0059] Example 2

[0060] Preparation of salt-sensitive functional monomers:

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

[0062]

[0063] Preparation of polyacrylamide dry powder particles:

[0064] Add 6865kg of water into a 10 cubic batching kettle, add 1900kg of acrylamide, 500kg of acrylic acid, 300kg of 2-acrylamido-2-methylpropanesulfonic acid, 335kg of sodium hydroxide and 150kg of salt-sensitive functional monomer in sequence under stirring, adjust the pH of the system to 8.0, cool to 10°C, transfer to a reactor, and add 500g of hydrogen peroxide (dissolved in 3000g of water) and 100g of ferrous sulfate heptahydrate (dissolved in 1000g of water) in sequence after passing nitrogen for 30min. Continue to pass nitrogen for 5min after the system becomes thick. Close the reactor and react for about 4h to naturally heat to 65-75°C, keep warm for 2h, extrude and granulate the colloidal material in the reactor after the reaction is completed, and transport it to a drying equipment for drying. After drying, crush and screen, collect and package the particles below 60 mesh, and ensure that the polyacrylamide dry powder particles with a mesh number above 60 mesh are controlled to be no more than 5wt%.

[0065] The technical indicators of the product are shown in Table 2, where the viscosity is measured as follows:

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

[0067] Dissolve the polyacrylamide dry powder particles in 400 ml of test water (including water containing 2% potassium chloride, tap water or water containing 15% ammonium sulfate), stir at 1000 rpm, dissolve for 3 minutes, and the concentration of the polyacrylamide dry powder particles is 1800 ppm.

[0068] Table 2 Technical indicators of polyacrylamide particles

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

[0070] Preparation of aqueous suspension:

[0071] Add 2400kg of water and 1300kg of calcium chloride into a 5-cubic-meter batching kettle, stir and dissolve, then control the temperature to 30℃, add 120kg of xanthan gum, stir and dissolve until a uniform solution is obtained, add 300kg of ethanol, stir evenly, add 1600kg of the above-mentioned polyacrylamide dry powder particles, continue stirring until all the polyacrylamide particles are dispersed to form a uniform suspension, and then load into a ton barrel.

[0072] Example 3

[0073] Preparation of salt-sensitive functional monomers:

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

[0075]

[0076] Preparation of polyacrylamide dry powder particles:

[0077] Add 6435kg of water into a 10 cubic batching kettle, add 1900kg of acrylamide, 600kg of acrylic acid, 200kg of 2-acrylamido-2-methylpropanesulfonic acid, 200kg of methacrylic acid, 465kg of sodium hydroxide, and 200kg of salt-sensitive functional monomer in sequence under stirring, adjust the pH of the system to 6.0, cool to 5°C, transfer to a reactor, pass nitrogen for 30 minutes, then add 300g of tert-butyl hydroperoxide (dissolved in 1000g of water), 7-hydrated sulfuric acid in sequence. 100g of ferrous acid (dissolved in 1000g of water), 200g of sodium pyrosulfite (dissolved in 1000g of water), after the system becomes thick, continue to pass nitrogen for 5min, close the system and react for about 3h to naturally raise the temperature to 65-75℃, keep warm for 2h, after the reaction is completed, extrude the colloidal material in the reactor into granules, and transport it to the drying equipment for drying, crush and sieve after drying, collect and package the granules below 60 mesh, and ensure that the polyacrylamide dry powder granules above 60 mesh are controlled to be no more than 5wt%.

[0078] The technical indicators of the product are shown in Table 3, where the viscosity is measured as follows:

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

[0080] Dissolve the polyacrylamide dry powder particles in 400 ml of test water (including water containing 2% potassium chloride, tap water or water containing 15% ammonium sulfate), stir at 1000 rpm, dissolve for 3 minutes, and the concentration of the polyacrylamide dry powder particles is 1800 ppm.

[0081] Table 3 Technical indicators of polyacrylamide particles

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

[0083] Preparation of aqueous suspension:

[0084] Add 2600kg of water and 1500kg of magnesium chloride into a 5 cubic batching kettle, stir and dissolve, then control the temperature to 20℃, add 50kg of fumed silica, stir and dissolve until a uniform solution is obtained, add 800kg of the above-mentioned polyacrylamide dry powder particles, continue stirring until all the polyacrylamide particles are dispersed to form a uniform suspension, and then load into a ton barrel.

[0085] Example 4

[0086] Preparation of salt-sensitive functional monomers:

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

[0088]

[0089] Preparation of polyacrylamide dry powder particles:

[0090] 7690 kg of water was added to a 10 cubic batching kettle, and 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 were added in sequence under stirring. The pH of the system was adjusted to 7.5, and the temperature was lowered to 15°C, and the mixture was transferred to a reactor. After nitrogen was passed for 30 minutes, 400 g of sodium persulfate (dissolved in 2000 g of water) and 200 g of sodium thiosulfate (dissolved in 1000 g of water) were added in sequence. After the system became thick, nitrogen was continued to be passed for 5 minutes. The system was closed and reacted for about 5 hours, and the temperature was naturally raised to 65-75°C, and the mixture was kept warm for 2 hours. After the reaction was completed, the colloidal material in the reactor was extruded and granulated, and transported to a drying equipment for drying. After drying, the particles were crushed and sieved, and the particles below 60 mesh were collected and packaged to ensure that the polyacrylamide dry powder particles with a mesh size above 60 mesh were controlled to be no more than 5wt%.

[0091] The technical indicators of the product are shown in Table 4, where the viscosity is measured as follows:

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

[0093] Dissolve the polyacrylamide dry powder particles in 400 ml of test water (including water containing 2% potassium chloride, tap water or water containing 15% ammonium sulfate), stir at 1000 rpm, dissolve for 3 minutes, and the concentration of the polyacrylamide dry powder particles is 1800 ppm.

[0094] Table 4 Technical indicators of polyacrylamide particles

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

[0096] Preparation of aqueous suspension:

[0097] Add 3000kg of water, 500kg of sodium chloride and 1000kg of calcium chloride into a 5 cubic batching kettle, stir and dissolve, then control the temperature to 25°C, add 200kg of polyamide wax, stir and dissolve until a uniform solution is obtained, add 1800kg of the above-mentioned polyacrylamide dry powder particles, continue stirring until all the polyacrylamide particles are dispersed to form a uniform suspension, and then load into a ton barrel.

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A salt-sensitive polyacrylamide dry powder particle, characterized in that: Introducing a functional monomer containing a salt-sensitive side chain into a polyacrylamide molecule through a copolymerization reaction to obtain the polyacrylamide dry powder particles; Wherein, the structural formula of the functional monomer is Here, n is an integer between 4 and 20.

2. The polyacrylamide dry powder particles according to claim 1, characterized in that: The content of polyacrylamide dry powder particles with a mesh size of more than 60 meshes is not more than 5wt%.

3. The method for preparing the polyacrylamide dry powder particles according to any one of claims 1 to 2, characterized in that: The steps include: The acrylamide, comonomer and functional monomer are dissolved in water, the pH of the system is adjusted to 6-8 and the temperature is lowered to 0-15°C, 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 extruded, granulated, dried and crushed to obtain the final product.

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

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

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, methallylsulfonic acid and vinylbenzenesulfonic acid.

8. A polyacrylamide suspension, characterized in that: The following raw materials are included in weight percentage: 5-35wt% of the polyacrylamide dry powder particles according to any one of claims 1 to 2; Suspending agent 0.01-10wt%; Water-soluble salt 10-50wt%; Alcohol solvent 0-20wt%; The rest is water.

9. The method for preparing a polyacrylamide suspension according to claim 8, characterized in that: The steps include: Dissolve the water-soluble salt in water, keep the temperature at 20-30°C, add the suspending agent, add or not add the alcohol solvent, stir evenly and then add the polyacrylamide dry powder particles to obtain the polyacrylamide suspension.

10. Use of the polyacrylamide suspension according to claim 8 in the exploitation of shale oil and shale gas.

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