Salt-resistant and shear-resistant gel particle for deep flow regulation of oil reservoir and preparation method of salt-resistant and shear-resistant gel particle

Abstract

The invention belongs to the technical field of deep flow regulation of oil reservoirs, and particularly relates to salt-resistant and shear-resistant gel particles for deep flow regulation of oil reservoirs and a preparation method of the salt-resistant and shear-resistant gel particles. The core-shell structure design is adopted, the inner core of the particle is prepared through a reverse emulsion method, and the outer shell of the particle forms a uniform coating structure through butyl acrylate and 1, 4-butanediol diacrylate. When ester bonds in the particle shells are hydrolyzed, water enters the particle cores, so that the particles absorb water and expand. Sodium alginate containing a large amount of-COO-and-OH is introduced into a particle inner core to serve as a functional monomer,-COO-is complexed with divalent metal ions to form a stable network structure, and a large amount of hydrogen bonds can be formed in the presence of-OH, so that the stability of a gel network is further enhanced. The salt-resistant and shear-resistant gel particle with the core-shell structure is high in mechanical performance, can keep good stability in a high-salt environment, is good in deep migration performance, and can effectively realize plugging and flow regulation of deep reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of deep flow regulation in oil reservoirs, and in particular relates to salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs and a preparation method thereof. Background Art

[0002] Due to the presence of fractures and high permeability water channels in deep reservoirs, the swept volume of injected water is limited, greatly reducing the water injection recovery rate. Polymer gel particles are widely used in oil fields as profile control agents to improve reservoir heterogeneity, increase the swept coefficient of injected water, and thus improve the recovery rate. During the preparation of polymer gel particles, these nano- or micron-sized particles can maintain a small particle size, and in the process of migrating to the reservoir, the particles absorb water and swell, increasing their size to block the dominant channels in the reservoir, thereby diverting the displacement fluid to areas containing a large amount of residual oil and enhancing the recovery of the residual oil. However, due to the significant shear effect of the reservoir pore throat, the mechanical properties and stability of the particles will decrease, and even particle rupture may occur. In addition, metal ions in the formation water will compress the diffuse double layer of the particles, resulting in insufficient swelling of the particles and poor plugging effect.

[0003] Therefore, there is an urgent need to develop a new type of polymer gel particles suitable for the deep environment of low-permeability reservoirs, which can have good salt resistance, shear resistance and deep migration ability, so as to achieve precise plugging and flow regulation and increase recovery rate. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a salt-resistant and shear-resistant gel particle for deep reservoir flow regulation and a preparation method thereof. The present invention adopts a core-shell structure design. The core of the particle is prepared by a reverse emulsion method, and the outer shell is formed into a uniform coating structure by butyl acrylate (BA) and 1,4-butanediol diacrylate (BDDA). When the ester bond in the particle shell is hydrolyzed, water enters the particle core, causing the particle to absorb water and swell. The particle core introduces a large amount of -COO - and -OH as functional monomers, -COO - It complexes with divalent metal ions to form a stable network structure. The presence of -OH can form a large number of hydrogen bonds, thereby further enhancing the stability of the gel network.

[0005] The technical solutions adopted are: A salt-resistant and shear-resistant gel particle for deep reservoir flow regulation comprises a gel particle core and a gel particle shell, wherein the raw materials used in the gel particle core include acrylamide, sodium alginate, ammonium persulfate, N,N'-methylenebisacrylamide, Span 80, Tween 80 and cyclohexane, and the raw materials used in the gel particle shell include butyl acrylate and 1,4-butanediol diacrylate; wherein, in the process of synthesizing the gel particle core, acrylamide, sodium alginate, ammonium persulfate and N,N'-methylenebisacrylamide are prepared into an aqueous phase mixed solution A, wherein sodium alginate is a monomer, accounting for 0.5% to 2% of the mass of the aqueous phase mixed solution A, and ammonium persulfate is 0.5% to 2% of the mass of the aqueous phase mixed solution A. The molar weight of the monomer is 0.3%, the molar weight of the monomer is 0.1%, and the acrylamide accounts for 40% of the mass of the aqueous mixed solution A; Span 80 and Tween 80 are taken as emulsifiers and mixed with cyclohexane to prepare an oil mixed solution B, in which the volume ratio of Span 80 to Tween 80 is 81.31:18.69, and the emulsifier accounts for 3% of the mass of the oil mixed solution B; the aqueous mixed solution A and the oil mixed solution B are mixed, and the outer shell of the gel particles is synthesized with butyl acrylate and 1,4-butanediol diacrylate as monomers, and the molar ratio of butyl acrylate to 1,4-butanediol diacrylate is 10:1.

[0006] A method for preparing salt-resistant and shear-resistant gel particles for deep reservoir flow regulation comprises the following steps: The steps include: (1) Synthesis of gel particle core: a. Prepare the emulsion: dissolve sodium alginate, ammonium persulfate, N,N'-methylenebisacrylamide and acrylamide in deionized water to obtain an aqueous mixed solution A; mix Span 80, Tween 80 and cyclohexane thoroughly to obtain an oil mixed solution B; Mix the aqueous mixed solution A and the oily mixed solution B, and homogenize for 10 to 30 minutes to obtain a stable and uniform emulsion; b. Heating reaction and dehydration: the prepared emulsion is added to a three-necked flask and reacted in an oil bath to obtain a gel particle core suspension; subsequently, the gel particle core suspension is added to anhydrous ethanol for washing, and a suction filtration device is connected to obtain a gel particle core powder by suction filtration, and then vacuum dried to finally obtain a dry gel particle core powder; (2) Synthesis of core-shell structured gel particles: Dispersing the dried gel particle core powder in a mixed solution of cyclohexane and anhydrous ethanol, and uniformly dispersing the gel particle core by an ultrasonic device to form a gel particle core suspension; dissolving butyl acrylate and 1,4-butanediol diacrylate in deionized water to obtain a gel particle shell solution; Adding ammonium persulfate solution to the gel particle shell solution, and then adding it to a dropping funnel; connecting a condensation device, and dripping the gel particle shell solution with the ammonium persulfate solution into the gel particle core suspension under the condition of oil bath heating, and continuously introducing nitrogen into the reaction device during the reaction; After the reaction is completed, the product is added to anhydrous ethanol for washing, and connected to a suction filtration device to obtain core-shell structure gel particle powder by suction filtration, and then vacuum dried to finally obtain dry core-shell structure gel particle powder.

[0007] Preferably, in step (1), the aqueous mixed solution A and the oily mixed solution B are mixed in a mass ratio of 2:1 and 4 r min -1 Homogenize at a power of .

[0008] Preferably, in step (1), the emulsion is added into a three-necked flask and reacted in a constant temperature oil bath at 70° C. for 2 to 3 hours.

[0009] Preferably, in step (2), in the mixed solution of cyclohexane and anhydrous ethanol, the volume ratio of cyclohexane to anhydrous ethanol is 1:1.

[0010] Preferably, in step (2), the molar ratio of butyl acrylate to 1,4-butanediol diacrylate is 10:1.

[0011] Preferably, in step (2), the mass fraction of the ammonium persulfate solution is 2 wt %.

[0012] Preferably, in step (2), the synthesis is carried out under heating conditions in an oil bath at 65° C., and the reaction time is 16 to 24 hours.

[0013] Preferably, when washing with anhydrous ethanol, washing is performed 2 to 3 times; when drying, it is placed in a vacuum drying oven at 40° C. and dried for 12 hours.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces sodium alginate (SA) as a functional monomer, combines divalent metal ion complexation with hydrogen bonding, and constructs a stable multi-crosslinked network structure. This structure effectively enhances the mechanical properties and water retention capacity of the gel particles, significantly improves their stability and shear resistance in a high-salt environment, and overcomes the performance degradation problem of traditional gel particles under the influence of formation shear force and salt ions.

[0015] The present invention proposes a new method to improve the deep migration performance of gel particles by adopting a core-shell structure design. The inner core is prepared by an inverse emulsion method, and the outer shell is formed into a uniform coating structure by butyl acrylate (BA) and 1,4-butanediol diacrylate (BDDA), which can hydrolyze to achieve particle expansion. This structural design not only improves the stability of the gel particles, but also has a certain slow swelling performance, enabling it to effectively migrate in deep formations and perform precise plugging, meeting the needs of deep reservoir flow regulation.

[0016] The present invention optimizes multiple key conditions in the synthesis process of gel particles, including the hydrophilic-lipophilic balance value (HLB value) of the emulsion, the homogenization power of the emulsion, the selection and dosage of the initiator (ammonium persulfate), etc., so as to obtain a uniform and stable emulsion and gel particles with suitable particle size. In addition, by systematically studying the effects of monomer concentration and dosage, the optimal sodium alginate (SA) and shell monomer concentration combination was determined, further improving the salt resistance, shear resistance, deep migration and plugging performance of the gel particles. The present invention verified through core displacement experiments that the core-shell structure gel particles provided have good deep migration and plugging performance, providing reliable technical support for efficient plugging and flow regulation in deep oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a technical principle diagram of the present invention.

[0018] Figure 2 This is a comparison chart of the salt resistance of different concentrations of sodium alginate and AM, AM+AMPS in Test Example 1 of the present invention.

[0019] Figure 3 This is a force curve diagram of different concentrations of sodium alginate and AM, AM+AMPS in Test Example 1 of the present invention.

[0020] Figure 4 This is the effect of different shell monomer concentrations on the swelling time of gel particles in Test Example 2 of the present invention.

[0021] Figure 5 This is a comparison of the shear resistance of the gel particle core powder with different sodium alginate contents and AM, AM+AMPS in Test Example 3 of the present invention.

[0022] Figure 6 This is the displacement pressure curve of the core-shell structure gel particles without aging process in Test Example 4 of the present invention.

[0023] Figure 7 This is the displacement pressure curve of the core-shell structure gel particles with aging process in Test Example 4 of the present invention.

[0024] Figure 8 This is a comparison chart of the core plugging rates without and with the aging process in Test Example 4 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and features of the present invention clearer, the present invention is further described in detail in conjunction with the following embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through conventional channels.

[0027] Example 1.

[0028] A method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs comprises the following steps: (1) Synthesis of the gel particle core: The gel particle core is synthesized by the inverse emulsion polymerization method. The aqueous reaction solution is evenly dispersed in the oil phase medium through homogenization to form an oil-in-water emulsion, which belongs to the single droplet reaction nucleation mode. Each droplet forms an independent polymer gel particle after the reaction.

[0029] a. Preparation of emulsion: Sodium alginate (accounting for 2% of the mass of aqueous solution), ammonium persulfate (accounting for 0.3% of the total molar amount of monomers), N,N'-methylenebisacrylamide (accounting for 0.1% of the total molar amount of monomers) and acrylamide (accounting for 40% of the mass of aqueous solution) are completely dissolved in deionized water to obtain an aqueous mixed solution A; Span 80, Tween 80 and cyclohexane are mixed and completely dissolved to obtain an oil mixed solution B; the emulsifiers Span 80 and Tween 80 account for 3wt% of the mass of the oil mixed solution B, and the volume ratio of Span 80 to Tween 80 is 81.31:18.69; The aqueous mixed solution A and the oily mixed solution B were mixed and then heated to 2×10 4 r min - Homogenize at 100% power for 20 minutes to obtain a stable and homogeneous emulsion.

[0030] b. Heating reaction and dehydration: Add the prepared emulsion into a three-necked flask and react in a 70 °C constant temperature oil bath for 2 hours to obtain a gel particle core suspension. Subsequently, add the gel particle core suspension into anhydrous ethanol for cleaning, and connect a suction filtration device to obtain a gel particle core powder by suction filtration, and then vacuum dry to finally obtain a dry gel particle core powder.

[0031] (2) Synthesis of core-shell structured gel particles.

[0032] In a three-necked flask, the dried gel particle core powder is dispersed in a mixed solution of cyclohexane and anhydrous ethanol (the volume ratio of cyclohexane to anhydrous ethanol is 1:1), and the gel particle core is evenly dispersed by an ultrasonic device to form a gel particle core suspension; Dissolving butyl acrylate and 1,4-butanediol diacrylate in a molar ratio of 10:1 in deionized water to obtain a gel particle shell solution; Add ammonium persulfate solution (2wt%) to the gel particle shell solution, and then add it to the dropping funnel; connect the condensation device, and drop the gel particle shell solution with ammonium persulfate solution into the particle core suspension under the condition of heating in an oil bath at 65℃. In this process, nitrogen is continuously introduced to remove excess oxygen, and the reaction time is 24 hours.

[0033] After the reaction is completed, the product is added to anhydrous ethanol for washing, and connected to a suction filtration device to obtain core-shell structure gel particle powder by suction filtration, and then vacuum dried to finally obtain dry core-shell structure gel particle powder.

[0034] The shear force of the formation will significantly weaken the mechanical properties of traditional gel particles and may even cause them to break. At the same time, the salt ions in the formation will compress the diffuse double layer of the gel particles, thereby reducing their water absorption and expansion performance. - and -OH as functional monomers, -COO - It can complex with divalent metal ions, such as calcium ions and magnesium ions in formation water, to form a stable network structure. The presence of -OH can form a large number of hydrogen bonds, thereby further enhancing the stability of the gel network. In addition, by introducing a highly efficient cross-linking agent, a multi-cross-linked network structure system was constructed. Figure 1 As shown. The multi-crosslinked network structure can significantly improve the mechanical properties and water retention capacity of the gel particles, thereby significantly enhancing their salt resistance and shear resistance.

[0035] The core-shell structured salt-resistant and shear-resistant gel particles of the present invention have strong mechanical properties, can maintain good stability in a high-salt environment, have good deep migration performance, and can effectively achieve plugging and flow regulation in deep reservoirs.

[0036] Test Example 1: Effect of sodium alginate on the stability of gel particles.

[0037] Weigh a certain amount of sodium alginate (0.5%, 1%, 1.5%, 2% of the mass of the aqueous solution), ammonium persulfate (APS) (0.3% of the total molar amount of the monomer), N,N'-methylenebisacrylamide (0.1% of the total molar amount of the monomer) and acrylamide (40wt% of the mass of the aqueous solution), and completely dissolve them in deionized water to obtain an aqueous phase solution. Take Span 80, Tween 80 and cyclohexane, and after they are completely dissolved, obtain an oil phase solution. Mix the aqueous phase solution and the oil phase solution in a mass ratio of 2:1 and place them in a 2×10 4 r min -1 Homogenize at a power of 20 minutes to obtain four stable and uniform emulsions.

[0038] The prepared emulsions were added to three-necked bottles and heated in a constant temperature oil bath at 70°C for 2 hours. After the reaction, a gel particle core suspension was obtained. Subsequently, the suspension was added to anhydrous ethanol to disperse into smaller particle cores. A suction filtration device was connected to filter out the white powder, and it was washed with anhydrous ethanol 2 to 3 times. The obtained powder was placed in a vacuum drying oven at 40°C and dried for 12 hours, and finally four gel particle core powders were obtained.

[0039] The four gel particle core powders prepared were dispersed in the same mass ratio with traditional salt-resistant gel particles AM (gel particles synthesized with acrylamide as monomer) and AM+AMPS (gel particles synthesized with acrylamide and 2-acrylamide-2-methylpropanesulfonic acid as monomers) in a 4.5×10 4 mg·L -1 ,9×10 4 mg·L -1 , 13.5×10 4 mg·L -1 , 18×10 4 mg·L -1 24 samples to be analyzed were obtained by mixing with simulated formation water and stirring for 6 hours until the water was completely absorbed. The particle size of the gel particles was measured by dynamic light scattering particle size analyzer (DLS), and the change of the expansion factor with the increase of mineralization was recorded. The results are as follows: Figure 2 The expansion factor is calculated using the existing calculation formula.

[0040] like Figure 2 As shown in the figure, the expansion factor of AM gel particles is less than 5, and it changes with the increase of mineralization. As the mineralization increases, the expansion factor of AM+AMPS gel particles decreases. When the mineralization is 18×10 4 mg·L -1When the expansion factor of AM+AMPS gel particles is less than 5, the expansion factor of sodium alginate gel particles is greater than 10, and the fluctuation is not obvious with the increase of mineralization. In addition, the expansion factor increases with the increase of sodium alginate concentration. The effective inclusion of sodium alginate in the gel particle core powder prepared by the present invention can improve the salt resistance of the gel particles.

[0041] To further study the effect of sodium alginate on the mechanical properties of gel particles, the elastic moduli of the six gel particles in simulated formation water were calculated. The torque curves between the probe and the six gel particle samples were measured using an atomic force microscope (AFM). Figure 3 The Young's modulus of the gel particles is calculated as shown in Table 1.

[0042] Table 1 Young's modulus of four gel particle core powders prepared in Test Example 1 and AM, AM+AMPS

[0043] The results show that compared with gel particles without sodium alginate, gel particles containing sodium alginate have a higher Young's modulus, and the Young's modulus increases with the increase of sodium alginate content, indicating that adding sodium alginate to gel particles can effectively improve the mechanical properties of gel particles. However, high concentrations of sodium alginate will affect the dispersion effect of aqueous solution in the oil phase, thereby increasing the viscosity of the aqueous solution and reducing the stability of the emulsion. Therefore, in subsequent studies, 2wt% sodium alginate was used.

[0044] Test Example 2, the effect of controlling shell thickness on delayed expansion performance.

[0045] Take the gel particle core powder containing 2wt% sodium alginate prepared in Test Example 1, and disperse the dried core powder in a mixed solution of cyclohexane and anhydrous ethanol to obtain a suspension of the particle core. Use an ultrasonic device to evenly disperse the particle core. Take butyl acrylate and 1,4-butanediol diacrylate in a molar ratio of 10:1 and dissolve them in deionized water. The concentrations of the shell monomers are 0.5mol / L, 1mol / L, 1.5mol / L and 2mol / L, respectively, to obtain four degradable shell solutions.

[0046] Add 2wt% APS solution to the shell liquid, and then add it to the dropping funnel. Connect the condensation device, and slowly drip the prepared shell solution into the particle core suspension under the condition of 65℃ oil bath heating. In this process, nitrogen is continuously introduced to remove excess oxygen, and the reaction time is 24 hours. After the reaction, filter out the white powder with a filter device and wash it with anhydrous ethanol 2-3 times. Then put the white powder into a vacuum oven at 40℃ and dry it for 12 hours. Finally, four gel particles with a hydrophobic shell are obtained. The prepared gel particle powder is fully dispersed in a 4.5×10 4 mg·L -1 The samples were then aged in a 70°C constant temperature oven and the expansion factor was measured regularly. The changes in expansion factor over aging time were recorded. Figure 4 shown.

[0047] like Figure 4 As shown in the figure, in the first stage, the particle size changes slightly due to the presence of the shell layer. When the ester bonds in the shell layer are hydrolyzed, water absorption channels appear and the gel particles begin to absorb water and swell. When the shell monomer concentration is 0.5 mol / L, the gel particle size increases rapidly after 3 days and remains stable after 14 days. When the shell monomer concentration is 1 mol / L, the particle size remains unchanged in the first 6 days, then gradually increases and reaches a maximum value on the 18th day. When the shell monomer concentration is 1.5 mol / L, the particle size gradually increases in the first 10 days and finally reaches a maximum value on the 22nd day. When the shell monomer concentration is 2 mol / L, the particle size remains stable in the first 12 days and reaches a maximum value after 28 days. The results show that the shell structure can effectively inhibit the water absorption behavior of the particles. At the same time, by adjusting the shell monomer concentration, the expansion delay time can be accurately controlled to meet the needs of deep migration in different reservoirs.

[0048] Test Example 3, evaluation of shear resistance.

[0049] The core powders of the gel particles with different sodium alginate contents in Test Example 1 were dispersed in a 4.5×10 4 mg·L -1 Through core experiments, under the condition of confining pressure of 3 MPa, the water content of the simulated formation water was 10 mL•min -1 The dispersed gel particle suspension was injected into a 100 mD core with a length of 5 cm at a speed of 1.5 200 μm. At the outlet, the gel particle suspension after displacement was recovered. The Young's modulus after the gel particles were moved was measured using an atomic force microscope (AFM), and then the above operation was repeated. The Young's modulus retention rate was calculated by the existing technical formula, that is, R = (M b -M a) / M b Where R is the Young's modulus retention rate; M b is Young's modulus before migration, unit is kPa; Ma is Young's modulus after migration, unit is kPa.

[0050] like Figure 5 As shown in the figure, with the increase of migration distance, the Young's modulus of AM gel particles gradually decreases, and the final Young's modulus retention rate is 65.32%. The insertion of AMPS slightly increases the flexibility of the molecular chain, and the sulfonic acid group has the ability to increase the polarity of the polymer molecule and the flexibility of the molecular chain. Therefore, the Young's modulus of AM+AMPS gel particles decreases slower than that of AM gel particles, and has better shear resistance, with a final retention rate of 69.53%. The Young's modulus of gel particles containing sodium alginate decreases slowly with the increase of migration distance, and the final retention rate is greater than 90%. This shows that the multi-cross-linked network structure significantly improves the elasticity of the gel particles, and the sodium alginate gel particles perform better in shear stability. Therefore, gel particles with a multi-cross-linked network structure can maintain better stability during migration, which lays the foundation for improving effective deep plugging.

[0051] Test Example 4: The plugging performance was evaluated through core displacement experiments.

[0052] The gel particles containing 2 wt% sodium alginate described in Test Example 1 were dispersed in a 4 mg·L -1 The core permeability is 100um 2 、200um 2 、500um 2 Test when.

[0053] In order to investigate the migration performance of core-shell particles, the experimental process did not include the aging process. -1 1 PV simulated water, 1 PV gel particle suspension, and 4 PV simulated water were injected in sequence at a rate of 1 PV. The displacement pressure versus injection volume curve was obtained, as shown in Figure 6 shown.

[0054] In order to explore the plugging performance of core-shell gel particles, the experimental process includes an aging process. Under a confining pressure of 3 MPa, the -11 PV of simulated water and 1 PV of gel particle suspension were injected in sequence at a rate of 1 PV. The core injected with core-shell gel particles was then taken out, sealed, and placed in a 70°C constant temperature incubator for 30 days. The aged core was placed in a core holder and connected to a displacement device. Under a confining pressure of 3 MPa, the core was flushed at a rate of 0.3 mL•min -1 4 PV simulated water was injected at a rate of , and the displacement pressure vs. injection volume curve was obtained, as shown in Figure 7 The final calculation result of the plugging rate is shown as Figure 8 shown.

[0055] The experimental results show that in the absence of aging, the core-shell structure of the core-shell gel particles remains intact. The shell prevents expansion and water absorption, keeping the particle size small. During the particle injection process, the accumulation of particles at the pore throats leads to an increase in injection pressure. However, when the second water injection is performed, the displacement pressure decreases in the direction of the initial water injection pressure. Most of the core-shell gel particles are able to flow through the core pore throat structure, and the plugging rate is less than 20%. During the entire aging process, the particle size increases sharply due to the hydrolysis of the shell, and the hydrophilicity of the particles is improved. Sodium alginate improves both stability and salt tolerance, with a plugging rate of more than 90%, indicating that the core-shell gel particles have good plugging and flow regulation capabilities.

[0056] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A salt-resistant and shear-resistant gel particle for deep flow regulation in oil reservoirs, characterized in that: The invention comprises a gel particle core and a gel particle shell, wherein the raw materials used in the gel particle core include acrylamide, sodium alginate, ammonium persulfate, N,N'-methylenebisacrylamide, Span 80, Tween 80 and cyclohexane, and the raw materials used in the gel particle shell include butyl acrylate and 1,4-butanediol diacrylate; wherein, in the synthesis process of the gel particle core, acrylamide, sodium alginate, ammonium persulfate and N,N'-methylenebisacrylamide are prepared into an aqueous phase mixed solution A, wherein sodium alginate is a monomer, accounting for 0.5% to 2% of the mass of the aqueous phase mixed solution A, and ammonium persulfate accounts for 0.3% of the molar weight of the monomer. %, N,N'-methylenebisacrylamide accounts for 0.1% of the molar amount of the monomer, and acrylamide accounts for 40% of the mass of the aqueous phase mixed solution A; Span 80 and Tween 80 are taken as emulsifiers and mixed with cyclohexane to prepare an oil phase mixed solution B, in which the volume ratio of Span 80 to Tween 80 is 81.31:18.69, and the emulsifier accounts for 3% of the mass of the oil phase mixed solution B; the aqueous phase mixed solution A and the oil phase mixed solution B are mixed, and the outer shell of the gel particles is synthesized with butyl acrylate and 1,4-butanediol diacrylate as monomers, and the molar ratio of butyl acrylate to 1,4-butanediol diacrylate is 10:

1.

2. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 1, characterized in that: The steps include: (1) Synthesis of gel particle core: a. Prepare the emulsion: dissolve sodium alginate, ammonium persulfate, N,N'-methylenebisacrylamide and acrylamide in deionized water to obtain an aqueous mixed solution A; mix Span 80, Tween 80 and cyclohexane thoroughly to obtain an oil mixed solution B; Mix the aqueous mixed solution A and the oily mixed solution B, and homogenize for 10 to 30 minutes to obtain a stable and uniform emulsion; b. Heating reaction and dehydration: the prepared emulsion is added to a three-necked flask and reacted in an oil bath to obtain a gel particle core suspension; subsequently, the gel particle core suspension is added to anhydrous ethanol for washing, and a suction filtration device is connected to obtain a gel particle core powder by suction filtration, and then vacuum dried to finally obtain a dry gel particle core powder; (2) Synthesis of core-shell structured gel particles: Dispersing the dried gel particle core powder in a mixed solution of cyclohexane and anhydrous ethanol, and uniformly dispersing the gel particle core by an ultrasonic device to form a gel particle core suspension; dissolving butyl acrylate and 1,4-butanediol diacrylate in deionized water to obtain a gel particle shell solution; Adding ammonium persulfate solution to the gel particle shell solution, and then adding it to a dropping funnel; connecting a condensation device, and dripping the gel particle shell solution with the ammonium persulfate solution into the gel particle core suspension under the condition of oil bath heating, and continuously introducing nitrogen into the reaction device during the reaction; After the reaction is completed, the product is added to anhydrous ethanol for washing, and connected to a suction filtration device to obtain core-shell structure gel particle powder by suction filtration, and then vacuum dried to finally obtain dry core-shell structure gel particle powder.

3. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: In the step (1), the aqueous mixed solution A and the oily mixed solution B are mixed in a mass ratio of 2:1 and heated to 2×10 4 r min - ¹ of power.

4. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: In the step (1), the emulsion is added into a three-necked flask and reacted in a constant temperature oil bath at 70°C for 2 to 3 hours.

5. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: In the step (2), in the mixed solution of cyclohexane and anhydrous ethanol, the volume ratio of cyclohexane to anhydrous ethanol is 1:

1.

6. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: In the step (2), the molar ratio of butyl acrylate to 1,4-butanediol diacrylate is 10:

1.

7. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: In the step (2), the mass fraction of the ammonium persulfate solution is 2 wt %.

8. The method for preparing salt-resistant and shear-resistant gel particles for deep reservoir flow regulation according to claim 2, characterized in that: In the step (2), the synthesis is carried out under the condition of heating in an oil bath at 65° C., and the reaction time is 16 to 24 hours.

9. The method for preparing salt-resistant and shear-resistant gel particles for deep flow regulation in oil reservoirs according to claim 2, characterized in that: When cleaning with anhydrous ethanol, wash 2 to 3 times; when drying, place it in a vacuum drying oven at 40 °C for 12 hours.

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