Salt-resistant polyacrylamide emulsion for oil field and preparation method thereof

Abstract

The invention belongs to the technical field of oil exploitation, and relates to a salt-resistant polyacrylamide emulsion for an oil field and a preparation method of the salt-resistant polyacrylamide emulsion. The preparation method comprises the following steps: dissolving acrylamide, a sulfo salt-resistant monomer, a hyperbranched hydrophobic monomer, a nano salt-resistant agent and PNIPAM microgel in a water phase according to a weight ratio, adding an initiator under the protection of nitrogen, and reacting to generate a jelly; shearing the jelly, granulating, drying, and sieving with a 120-mesh sieve to obtain hyperbranched polymer powder; mixing the white oil, the compound emulsifier and the suspension additive, and stirring at a high speed of 500-1000r / min; adding hyperbranched polymer powder, and continuously stirring until a uniform dispersion system is formed; and adding an oxidizing agent to terminate the reaction, cooling and defoaming to obtain the finished emulsion. Through the three-level innovative design of molecules, nanometer and intelligent materials, the problems of emulsion viscosity attenuation, slow dissolution and oil phase pollution in a high-salt oil field environment are solved, the viscosity retention rate exceeds 90% when the emulsion is directly prepared in flowback fluid or seawater, and the crude oil recovery rate is increased by 15% or above.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, specifically to a salt-resistant polyacrylamide emulsion for oil fields and its preparation method. Background Technology

[0002] Salt-resistant polyacrylamide emulsions for oilfields are functional polymer materials developed for oilfield environments with high salinity (over 30,000 mg / L). They need to maintain viscosity stability under high temperature (over 90℃) and high calcium and magnesium ion (over 500 mg / L) conditions. They are irreplaceable in tertiary oil recovery and fracturing with proppant transport, but existing products generally suffer from technical bottlenecks such as high-temperature viscosity decay, slow dissolution rate, and insufficient salt resistance, which restrict the efficiency of deep oil and gas resource development.

[0003] Invention patent CN118772331A discloses a preparation process for a salt-resistant polyacrylamide emulsion for oilfield use. The process involves mixing acrylamide, anionic monomer, salt-resistant agent, dispersant, and stabilizer to obtain a preliminary mixture. A chain extender, reducing agent, initiator, and water are then added to the preliminary mixture and stirred until homogeneous, yielding a final mixture. After the mixture reacts, an oxidant is added, and the mixture is cooled and defoamed to obtain the polyacrylamide emulsion. This emulsion exhibits good salt resistance and high stability even in the presence of salt. However, it fails to address the synergistic challenge of in-situ grafting of hyperbranched monomers and three-dimensional dispersion of nano-salt-resistant agents, particularly lacking a method to simultaneously construct a hydrophobic association network at the molecular level and achieve uniform distribution of nanoscale ion adsorption sites. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a salt-resistant polyacrylamide emulsion for oil fields and its preparation method.

[0005] The technical solution adopted by this invention to solve its technical problem is: an oilfield salt-resistant polyacrylamide emulsion, comprising the following components by weight: Acrylamide 80-100 parts; 90-110 parts of sulfonic acid group salt-resistant monomer; 20-27 parts of hyperbranched hydrophobic monomers selected from tetradecylacrylamide, octadecyl acrylate or mixtures thereof; 25-29 parts of a nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microspheres modified silica in a mass ratio of 1-3:2-4; 4-8 parts of hydrophobic silica-encapsulated PNIPAM (poly-N-isopropylacrylamide) microgel; 200-280 parts of white oil; 8-12 parts of compound emulsifier; Suspension agent 1-5 parts.

[0006] Preferably, the salt-resistant polyacrylamide emulsion for oilfield use comprises the following components in parts by weight: 95 parts of acrylamide; 98 parts of sulfonic acid group salt-resistant monomer; 26 parts of hyperbranched hydrophobic monomers selected from tetradecylacrylamide, octadecyl acrylate or mixtures thereof; 26 parts of a nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica in a mass ratio of 2:3; Five portions of PNIPAM (poly-N-isopropylacrylamide) microgels encapsulated in hydrophobic silica; 250 parts white oil; 9 parts of compound emulsifier; Three parts of suspending agent.

[0007] Furthermore, the sulfonic acid salt-resistant monomer is one or a mixture of several of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium methacrylate sulfonate (SMAS), and sodium styrene sulfonate (SSS); the suspending agent is pentanol or methanol.

[0008] Furthermore, the composite emulsifier is a commonly used composite emulsifier in the prior art, which can be conventionally selected by those skilled in the art, such as a combination of sorbitan fatty acid ester emulsifier, polymeric emulsifier, and fatty alcohol polyoxyethylene ether emulsifier. The preferred sorbitan fatty acid ester emulsifier is SPAN60, SPAN80, etc.; the preferred polymeric emulsifier is oligomeric ethylene oxide methacrylate, polyisobutylene succinic anhydride ester, styrene-maleic anhydride copolymer, etc.

[0009] In this invention, the sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica were prepared using the method disclosed in CN118772331A, a preparation process for a salt-resistant polyacrylamide emulsion for oilfield use. The hydrophobic silica-encapsulated PNIPAM (poly-N-isopropylacrylamide) microgel was prepared using existing technology.

[0010] A method for preparing salt-resistant polyacrylamide emulsions for oilfield use includes the following steps: Step 1: Preparation of hyperbranched polymer powder: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel are dissolved in the aqueous phase according to the weight ratio. An initiator is added under nitrogen protection, and the mixture is reacted at 50-60℃ for 6-8 hours to generate a gel. B. The colloidal substance is cut, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder; Step 2, Emulsion Preparation: A. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 500-1000 r / min; B. Add the hyperbranched polymer powder obtained in step one and continue stirring until a uniform dispersion system is formed; C. Add an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion.

[0011] A preferred method for preparing a salt-resistant polyacrylamide emulsion for oilfield use includes the following steps: Step 1: Preparation of hyperbranched polymer powder: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel are dissolved in the aqueous phase according to the weight ratio. An initiator is added under nitrogen protection, and the mixture is reacted at 50-60℃ for 6-8 hours to generate a gel. B. The colloidal substance is cut, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder; Step 2, Emulsion Preparation: A. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 800 r / min; B. Add the hyperbranched polymer powder obtained in step one and continue stirring until a uniform dispersion system is formed; C. Add an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion.

[0012] Furthermore, in the preparation of hyperbranched polymer powder in step one, the initiator is azobisisobutyronitrile (AIBN), and the amount of initiator is 1-3 parts. After adding the initiator, the temperature is controlled in stages: the reaction is carried out at 50-55℃ for the first 3 hours; and at 55-60℃ for the next 3-5 hours.

[0013] Furthermore, in the preparation of hyperbranched polymer powder in step one, the shearing treatment of the colloidal body is carried out using a twin-screw cryogenic shearer at a shearing speed of 200-400 r / min.

[0014] Furthermore, in the preparation of hyperbranched polymer powder in step one, the granulation of the colloidal body is carried out using a two-roll extrusion granulator, with wet particle diameter of 1.0±0.3mm and length of 2-3mm.

[0015] Furthermore, in the preparation of hyperbranched polymer powder in step one, the drying treatment of the colloidal body is carried out in a stepped temperature-controlled fluidized bed drying tower for zoned drying. The zoned drying of the stepped temperature-controlled fluidized bed drying tower includes a pre-drying zone, a main drying zone, and an equilibrium zone: the temperature of the pre-drying zone is 50-55℃, and the drying time is 30-40 min; the temperature of the main drying zone is 60-65℃, and the drying time is 70-90 min; the temperature of the equilibrium zone is 40-45℃, and the drying time is 20-30 min.

[0016] Furthermore, in step one, the preparation of hyperbranched polymer powder, the sieving of the colloidal substance is performed using an ultrasonic vibrating screen.

[0017] Furthermore, in step one of the preparation of hyperbranched polymer powder, the viscosity-average molecular weight of the hyperbranched polymer powder is 1.2 × 10⁻⁶. 7 -1.5×10 7 The solid content of Da is not less than 95%.

[0018] Furthermore, in step two, during emulsion preparation, the oxidant is ammonium persulfate, and the amount of oxidant used is 1-2 parts.

[0019] Furthermore, in the second step of emulsion preparation, the finished emulsion has a solid content of 40-50%, a mineralization tolerance of over 80,000 mg / L, and a viscosity retention rate of over 85% after shearing at 120°C for 1 hour.

[0020] The present invention has the following beneficial effects: 1. Hyperbranched hydrophobic monomers selected from tetradecylacrylamide, octadecyl acrylate, or combinations thereof form a hyperbranched structure, enhancing hydrophobic association and resisting salt ion compression, constituting the molecular design; a nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microspheres modified silica selectively adsorbs Ca²⁺. + / Mg² + This invention reduces the ion shielding effect, forming nano-adsorption; the PNIPAM microgel encapsulated in hydrophobic silica enables intelligent phase inversion of the emulsion, avoiding oil phase residue contamination of the formation, thus constituting temperature-sensitive separation. Through innovative design at the molecular, nano, and smart material levels, this invention solves the problems of emulsion viscosity decay, slow dissolution, and oil phase contamination in high-salt oilfield environments, demonstrating industrialization potential.

[0021] 2. Tetradecylacrylamide, octadecyl acrylate, or combinations thereof, as hyperbranched hydrophobic monomers in salt-resistant polyacrylamide emulsions for oilfield use, utilize their long alkyl chains (C14 / C18) to form a reversible physical cross-linked network through hydrophobic association in high-salt environments, effectively resisting salt ions (such as Na+). + Ca² + Mg² + The charge shielding effect on polymer molecular chains prevents chain curling, maintains hydrodynamic volume and solution viscosity, and allows the emulsion to retain more than 85% viscosity even when the salinity exceeds 80,000 mg / L. In synergy with nano-salt-resistant agents (such as sulfonic acid-modified boron nitride), the hydrophobic groups adsorb salt ions, and the nanopores bind chloride ions and metal ions, further reducing the damage of salt to the molecular chains. This allows the emulsion to retain more than 90% viscosity when directly formulated in backflow fluid or seawater, increasing crude oil recovery by more than 15%. Detailed Implementation

[0022] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention. However, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention. Example 1

[0023] The salt-resistant polyacrylamide emulsion for oilfield use comprises the following components by weight: 95 parts acrylamide; 98 parts sulfonic acid-based salt-resistant monomer 2-acrylamido-2-methylpropanesulfonic acid; 26 parts hyperbranched hydrophobic monomer tetradecylacrylamide; 26 parts nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica in a mass ratio of 2:3; 5 parts PNIPAM microgel encapsulated in hydrophobic silica; 250 parts white oil; 9 parts composite emulsifier (sorbitan fatty acid ester emulsifier, polymeric emulsifier); and 3 parts pentanol suspending agent.

[0024] The preparation method of salt-resistant polyacrylamide emulsion for oilfield use is as follows: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel were dissolved in the aqueous phase according to the weight ratio. Under nitrogen protection, 2 parts of the initiator azobisisobutyronitrile were added. The reaction was carried out in stages: 50℃ for 3 hours, and then maintained at 56℃ for 5 hours to generate a gel. B. The colloidal substance was sheared, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder. The viscosity-average molecular weight of the hyperbranched polymer powder was 1.5 × 10⁻⁶. 7 The solid content of Da is not less than 95%.

[0025] The shearing process was carried out using a twin-screw cryogenic shear at a shearing speed of 400 r / min; the granulation process was carried out using a twin-roll extrusion granulator, with wet particle diameters of 1.0 ± 0.3 mm and lengths of 2-3 mm; the drying process was carried out using a stepped temperature-controlled fluidized bed drying tower for zoned drying, which included a pre-drying zone, a main drying zone, and an equilibrium zone: the temperature in the pre-drying zone was 55℃, and the drying time was 30 min; the temperature in the main drying zone was 60℃, and the drying time was 90 min; the temperature in the equilibrium zone was 43℃, and the drying time was 20 min.

[0026] C. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 800 r / min; D. Add the hyperbranched polymer powder obtained in step B and continue stirring until a uniform dispersion system is formed; E. Add 1 part of ammonium persulfate as an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion. The finished emulsion has a solid content of 48%, a mineralization tolerance of over 80,000 mg / L, and a viscosity retention rate of over 85% after shearing at 120°C for 1 hour. Example 2

[0027] The oilfield salt-resistant polyacrylamide emulsion comprises the following components by weight: 80 parts acrylamide; 90 parts sulfonic acid-based salt-resistant monomers 2-acrylamido-2-methylpropanesulfonic acid and sodium methpropylene sulfonate; 27 parts hyperbranched hydrophobic monomer octadecyl acrylate; 25 parts nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica in a mass ratio of 1:2; 8 parts PNIPAM microgel encapsulated in hydrophobic silica; 240 parts white oil; 10 parts composite emulsifier (polymer emulsifier, fatty alcohol polyoxyethylene ether emulsifier); and 1 part methanol as a suspending agent.

[0028] The preparation method of salt-resistant polyacrylamide emulsion for oilfield use is as follows: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel were dissolved in the aqueous phase according to the weight ratio. Under nitrogen protection, 1 part of the initiator azobisisobutyronitrile was added. The reaction was carried out in stages: 55℃ for 3 hours, and then the reaction was maintained at 59℃ for 3 hours to generate a gel. B. The colloidal substance was sheared, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder. The viscosity-average molecular weight of the hyperbranched polymer powder was 1.2 × 10⁻⁶. 7 The solid content of Da is not less than 95%.

[0029] The shearing process was carried out using a twin-screw cryogenic shear at a shearing speed of 250 r / min; the granulation process was carried out using a twin-roll extrusion granulator, with wet particle diameters of 1.0 ± 0.3 mm and lengths of 2-3 mm; the drying process was carried out using a stepped temperature-controlled fluidized bed drying tower for zoned drying, which included a pre-drying zone, a main drying zone, and an equilibrium zone: the temperature in the pre-drying zone was 50℃, and the drying time was 40 min; the temperature in the main drying zone was 63℃, and the drying time was 80 min; the temperature in the equilibrium zone was 45℃, and the drying time was 25 min.

[0030] C. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 1000 r / min; D. Add the hyperbranched polymer powder obtained in step B and continue stirring until a uniform dispersion system is formed; E. Add 2 parts of ammonium persulfate as an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion. The finished emulsion has a solid content of 47%, a mineralization tolerance of over 80,000 mg / L, and a viscosity retention rate of over 85% after shearing at 120°C for 1 hour. Example 3

[0031] The oilfield salt-resistant polyacrylamide emulsion comprises the following components by weight: 100 parts acrylamide; 105 parts sodium styrene sulfonate, a sulfonic acid-based salt-resistant monomer; 23 parts hyperbranched hydrophobic monomer composed of tetradecyl acrylamide and octadecyl acrylate; 25 parts nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica in a mass ratio of 1:4; 4 parts PNIPAM microgel encapsulated in hydrophobic silica; 200 parts white oil; 8 parts composite emulsifier (sorbitan fatty acid ester emulsifier and fatty alcohol polyoxyethylene ether emulsifier); and 5 parts methanol as a suspending agent.

[0032] The preparation method of salt-resistant polyacrylamide emulsion for oilfield use is as follows: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel were dissolved in the aqueous phase according to the weight ratio. Under nitrogen protection, 2 parts of the initiator azobisisobutyronitrile were added. The reaction was carried out in stages: 54℃ for 3 hours, and then kept at 60℃ for 4 hours to generate a gel. B. The colloidal substance was sheared, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder. The viscosity-average molecular weight of the hyperbranched polymer powder was 1.3 × 10⁻⁶. 7 The solid content of Da is not less than 95%.

[0033] The shearing process was carried out using a twin-screw cryogenic shear at a shearing speed of 200 r / min; the granulation process was carried out using a twin-roll extrusion granulator, with wet particle diameters of 1.0 ± 0.3 mm and lengths of 2-3 mm; the drying process was carried out using a stepped temperature-controlled fluidized bed drying tower for zoned drying, which included a pre-drying zone, a main drying zone, and an equilibrium zone: the temperature in the pre-drying zone was 53℃, and the drying time was 35 min; the temperature in the main drying zone was 62℃, and the drying time was 70 min; the temperature in the equilibrium zone was 40℃, and the drying time was 28 min.

[0034] C. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 500 r / min; D. Add the hyperbranched polymer powder obtained in step B and continue stirring until a uniform dispersion system is formed; E. Add 2 parts of ammonium persulfate as an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion. The finished emulsion has a solid content of 50%, a mineralization tolerance of over 80,000 mg / L, and a viscosity retention rate of over 85% after shearing at 120°C for 1 hour. Example 4

[0035] The oilfield salt-resistant polyacrylamide emulsion comprises the following components by weight: 90 parts acrylamide; 110 parts sodium methacrylate sulfonate, a sulfonic acid-based salt-resistant monomer; 20 parts tetradecylacrylamide, a hyperbranched hydrophobic monomer; 27 parts nano-salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silica in a mass ratio of 3:2; 7 parts PNIPAM microgel encapsulated in hydrophobic silica; 280 parts white oil; 12 parts composite emulsifier (sorbitan fatty acid ester emulsifier and fatty alcohol polyoxyethylene ether emulsifier); and 2 parts pentanol, a suspending agent.

[0036] The preparation method of salt-resistant polyacrylamide emulsion for oilfield use is as follows: A. Acrylamide, sulfonic acid salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel were dissolved in the aqueous phase according to the weight ratio. Under nitrogen protection, 3 parts of the initiator azobisisobutyronitrile were added. The reaction was carried out in stages: 52℃ for 3 hours, and then maintained at 55℃ for 4 hours to generate a gel. B. The colloidal substance was sheared, granulated, dried, and then passed through a 120-mesh sieve to obtain hyperbranched polymer powder. The viscosity-average molecular weight of the hyperbranched polymer powder was 1.3 × 10⁻⁶. 7 The solid content of Da is not less than 95%.

[0037] The shearing process was carried out using a twin-screw cryogenic shear at a shearing speed of 350 r / min; the granulation process was carried out using a twin-roll extrusion granulator, with wet particle diameters of 1.0 ± 0.3 mm and lengths of 2-3 mm; the drying process was carried out using a stepped temperature-controlled fluidized bed drying tower for zoned drying, which included a pre-drying zone, a main drying zone, and an equilibrium zone: the temperature in the pre-drying zone was 55℃, and the drying time was 35 min; the temperature in the main drying zone was 65℃, and the drying time was 75 min; the temperature in the equilibrium zone was 42℃, and the drying time was 30 min.

[0038] C. Mix the white oil, composite emulsifier, and suspending agent, and stir at a high speed of 900 r / min; D. Add the hyperbranched polymer powder obtained in step B and continue stirring until a uniform dispersion system is formed; E. Add 1 part of ammonium persulfate as an oxidant to terminate the reaction, cool and defoam to obtain the finished emulsion. The finished emulsion has a solid content of 48%, a mineralization tolerance of over 80,000 mg / L, and a viscosity retention rate of over 85% after shearing at 120°C for 1 hour.

[0039] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0040] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. An oilfield salt-resistant polyacrylamide emulsion, characterized by, The following components by weight parts are included: Acrylamide 80-100 parts; Sulfonic acid-based salt-resistant monomer 90-110 parts; Hyperbranched hydrophobic monomer selected from tetradecyl acrylamide, octadecyl acrylate or a mixture thereof 20-27 parts; Nano salt-resistant agent composed of sulfonic acid-modified porous boron nitride and chitosan microsphere-modified silicon dioxide with a mass ratio of 1-3:2-4 25-29 parts; Hydrophobic silica-coated PNIPAM microgel 4-8 parts; White oil 200-280 parts; Composite emulsifier 8-12 parts; Suspension aid 1-5 parts.

2. The salt-resistant polyacrylamide emulsion for oil fields according to claim 1, wherein The sulfonic acid-based salt-resistant monomer is one or a mixture of several of 2-acrylamido-2-methylpropane sulfonic acid, sodium methacrylate sulfonate, and sodium styrene sulfonate; the suspension aid is amyl alcohol or methanol.

3. The method for producing a salt-resistant polyacrylamide emulsion for oil fields according to claim 1 or 2, characterized by, The following steps are included: Step one, preparation of hyperbranched polymer powder: A. Acrylamide, sulfonic acid-based salt-resistant monomer, hyperbranched hydrophobic monomer, nano salt-resistant agent, and PNIPAM microgel are dissolved in water phase according to the weight ratio, and an initiator is added under nitrogen protection. Reaction at 50-60°C for 6-8h to form a gel body; B. The gel body is cut, granulated, dried, and then passed through a 120 mesh sieve to obtain hyperbranched polymer powder; Step two, emulsion preparation: A. Mix white oil, composite emulsifier, and suspension aid, and stir at high speed of 500-1000r / min; B. Add the hyperbranched polymer powder obtained in step one, and continue stirring until a uniformly dispersed system is formed; C. Add an oxidizing agent to terminate the reaction, cool and defoam to obtain the finished emulsion.

4. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, characterized by, In the preparation of the hyperbranched polymer powder in step one, the initiator is azobisisobutyronitrile. After adding the initiator, the temperature is controlled in stages: the first 3h is kept at 50-55°C for reaction; the next 3-5h is kept at 55-60°C for reaction.

5. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, characterized by, In the preparation of the hyperbranched polymer powder in step one, the cutting treatment of the gel body is carried out using a double screw low temperature cutter at a shearing speed of 200-400r / min.

6. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, wherein the monomer solution is prepared by mixing 100 parts by weight of the monomer mixture, 0.1 to 0.5 parts by weight of the initiator, and 0.1 to 0.5 parts by weight of the polymerization inhibitor. In the preparation of the hyperbranched polymer powder in step one, the granulation treatment of the gel body is carried out using a double roller extrusion granulator, and the wet granules have a diameter of 1.0±0.3mm and a length of 2-3mm.

7. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, wherein the monomer solution is prepared by mixing 100 parts by weight of the monomer mixture, 0.1 to 0.5 parts by weight of the initiator, and 0.1 to 0.5 parts by weight of the polymerization inhibitor. In the preparation of the hyperbranched polymer powder in step one, the drying treatment of the gel body is carried out using a step-controlled temperature fluidized bed drying tower for zoned drying. The zoned drying of the step-controlled temperature fluidized bed drying tower includes a pre-drying zone, a main drying zone, and a balance zone: the temperature of the pre-drying zone is 50-55°C, and the drying time is 30-40min; the temperature of the main drying zone is 60-65°C, and the drying time is 70-90min; the temperature of the balance zone is 40-45°C, and the drying time is 20-30min.

8. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, wherein the monomer solution is prepared by mixing 100 parts by weight of the monomer mixture, 0.1 to 0.5 parts by weight of the initiator, and 0.1 to 0.5 parts by weight of the polymerization inhibitor. The viscosity average molecular weight of the hyperbranched polymer powder is 1.2×10 7 -1.5×10 7 Da, and the solid content is not less than 95%.

9. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, wherein In the preparation of the emulsion in step two, the oxidizing agent is ammonium persulfate.

10. The method for preparing a salt-resistant polyacrylamide emulsion for oil fields according to claim 3, wherein In the preparation of the emulsion in step two, the solid content of the finished emulsion is 40-50%, the mineralization tolerance exceeds 80,000mg / L, and the viscosity retention rate after 1 hour of shearing at 120°C exceeds 85%.