High-temperature and high-salt resistant soluble temporary plugging microspheres for acidizing and fracturing and a preparation method thereof

Abstract

A high-temperature, high-salt soluble temporary plugging microsphere for acid fracturing and its preparation method are disclosed. The preparation method includes the following steps: (1) Dispersing micro / nano particles in an ethanol aqueous solution under stirring, adding a silane coupling agent to remove oxygen, stirring evenly, adjusting the pH of the system to 9-10, then heating and refluxing, centrifuging, washing with anhydrous ethanol, and drying; (2) Dispersing the product of step (1) in deionized water, then adding a functional monomer and stirring until dissolved, adjusting the pH of the system to 7-8, heating, adding a first initiator, stirring evenly, and refluxing; (3) Maintaining the reaction temperature of step (2), adding a slow-dissolving monomer, a polyol, and a synergist in sequence, stirring to dissolve, adding a second initiator, stirring, refluxing, then sealing, and heating; (4) Drying, pulverizing, and sieving. The temporary plugging microsphere has good plugging performance and good resistance to iron ions and salt and temperature.

Description

Technical Field

[0001] This invention belongs to the field of reservoir stimulation technology, specifically relating to a high-temperature resistant, high-salt soluble temporary plugging microsphere for acid fracturing and its preparation method. Background Technology

[0002] In the fracturing process of low-permeability oil and gas reservoirs, increasing fracture-controlled reserves is one of the important methods to improve fracturing efficiency. Among these methods, achieving intra-fracture deflection is a key factor in constructing a complex, fishbone-like fracture network structure with the main fracture as the framework and continuously expanding outwards. Chemical plugging agents temporarily seal the main fracture, altering its propagation direction to achieve this complex fracture network construction. Commonly used chemical plugging agents are mainly classified as alkali-soluble, acid-soluble, oil-soluble, and water-soluble.

[0003] Chinese invention patent (CN 105441043 A) discloses a temporary plugging microsphere, which comprises 23-26% polyvinyl alcohol, 32-36% gelatin, 4-6% agar, 25-32% weighting agent, 0.01-1% sodium tetraborate, and 3-4% aldehyde curing agent. Through the synergistic effect of the above components, the formed plugging agent is formed into microspheres with a diameter of 50-700 micrometers, which is beneficial to improving its strength. The expansion ratio of the plugging microsphere can reach 3.5, which can effectively seal reservoir porosity. After the plugging is completed, raising the temperature to 100-120℃ will cause the plugging microsphere to degrade, and the degradation rate reaches 100% within 4-7 hours. However, the post-processing of this plugging agent is difficult and the construction risk is high.

[0004] Chinese invention patent (CN 112795373 A) relates to a soluble temporary plugging agent, a temporary plugging ball, and a method for preparing the same for fracturing at different temperatures. To improve the thermal stability of biodegradable polyester materials, a novel biodegradable polyester material is synthesized using 16-46% polycaprolactone, 10-30% polyglycolic acid, 20-30% polylactic acid, 4-17% polybutylene butyrate, a chain extender triglycidyl isocyanate, and 3% nano-silica. By changing the proportions of each raw material, the degradation temperature of the material can be adjusted to meet the degradation requirements at different bottom hole temperatures. However, this temporary plugging agent requires a large amount of nano-silica, resulting in incomplete post-treatment and significant reservoir damage.

[0005] Therefore, given the construction problems of commonly used temporary plugging agents in acid fracturing, such as high residue content after fracturing, significant reservoir damage, and low temperature and salt resistance, it is of great significance to provide a temporary plugging agent that has good temporary plugging effect, can dissolve completely, leaves no residue, causes no damage, and has good temperature and salt resistance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-temperature, high-salt soluble plugging microsphere for acid fracturing and its preparation method. By bridging a slow-dissolving polymer onto the surface of rigid soluble micro / nano particles, a core-shell structure soluble plugging microsphere is formed. Functional groups are introduced to enhance the microsphere's temperature and salt resistance as well as its iron ion stability, ultimately enabling complete dissolution and providing excellent plugging performance.

[0007] A method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing includes the following steps:

[0008] Step (1): Disperse the micro-nano particles in an ethanol aqueous solution under stirring, add silane coupling agent, remove oxygen for 30-40 min, stir evenly, adjust the pH of the system to 9-10, then heat to 45-60℃ and reflux for 12-24 h, centrifuge, wash with anhydrous ethanol, and dry; wherein, the micro-nano particles can dissolve in acidic solution;

[0009] Step (2): Disperse the product from step (1) in deionized water, then add the functional monomer and stir until dissolved. Adjust the pH of the system to 7-8, heat to 50-65℃, add the first initiator, stir evenly, and reflux for 5-8 hours. The functional monomer is an iron-resistant functional monomer, a temperature-resistant monomer, and a salt-resistant monomer.

[0010] Step (3): Maintain the reaction temperature of step (2), add the slow-dissolving monomer, polyol and synergist in sequence, stir to dissolve, add the second initiator, stir, reflux for 4-8 hours, then seal, heat to 120-160℃ and react for 2-5 hours;

[0011] Step (4): Dry, pulverize, and sieve.

[0012] Preferably, the anti-ferric ion functional monomer is at least one selected from acrylic acid, fumaric acid, maleic acid, citracic acid, itaconic acid, and pentenediaic acid.

[0013] Preferably, the slow-dissolving monomer is at least one selected from allyl alcohol, methacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, dicyclopentyl acrylate, and vinyl acetate.

[0014] Preferably, the synergist is at least one of polylactic acid, chitosan, polyglycolic acid, polybutylene succinate, and carboxymethyl cellulose.

[0015] Preferably, in step (1), the concentration of ethanol in the aqueous ethanol solution is 80-85 wt%; the micro-nano particles account for 5-10% of the mass of the aqueous ethanol solution, and the silane coupling agent accounts for 10-30% of the mass of the micro-nano particles.

[0016] Preferably, in steps (2) and (3), the total mass of the product, functional monomer, slow-dissolving monomer, polyol, synergist, and deionized water in step (1) is 100%, and the content of each substance is as follows: 3-6% of the product in step (1), 15-20% of the functional monomer, 15-25% of the slow-dissolving monomer, 10-15% of the polyol, 5-8% of the synergist, and the remainder is water;

[0017] The first initiator accounts for 10-20% of the functional monomer; the second initiator accounts for 15-20% of the slow-dissolving monomer mass.

[0018] The total mass of the functional monomers is calculated as 100%, and the content of each monomer is as follows: the content of the iron ion resistant functional monomer is 35-52%, the content of the temperature resistant monomer is 30-40%, and the content of the salt resistant monomer is 18-35%.

[0019] Preferably, the thermoresistant monomer is any one of N-vinylpyrrolidone carbamate, 4-vinylpyridine, 1,1-stilbene, acryloylmorpholine, dimethomorpholine, vinylimidazole, and styrene.

[0020] The salt-resistant monomer is any one of 2-acrylamido-2-methylpropanesulfonic acid, 1-(3-sulfonylpropyl)-2-vinylpyridinium inner salt, sodium vinylbenzenesulfonate, methacryloylethyl sulfobetaine, and methacrylic sulfonic acid.

[0021] The first initiator is at least one of potassium persulfate, sodium persulfate, ammonium persulfate, organic peroxide, and inorganic peroxide;

[0022] The second initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, persulfate, sulfite, organic peroxide, inorganic peroxide, and sulfite.

[0023] Preferably, the micro / nanoparticles are any one of iron(II,III) oxide, iron(II) hydroxide, magnesium carbonate, magnesium(II) hydroxide, and calcium(II) hydroxide, and the particle size of the micro / nanoparticles is 500 nm-1 μm.

[0024] The silane coupling agent is any one of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropylmethyldiethoxysilane, N-aminoethyl-γ-aminopropyltrimethoxysilane, N-aminoethyl-γ-aminopropyltriethoxysilane, and γ-diethylenetriaminepropylmethyldimethoxysilane.

[0025] Preferably, the polyol is any one of glycerol, pentaerythritol, sorbitol, and polyethylene glycol.

[0026] Preferably, in step (1), the drying conditions are drying at 50-70°C for 20-30 hours;

[0027] In step (4), the drying conditions are drying at 100-110℃ for 10-15 hours; the sieving is passing through a 20-120 mesh sieve.

[0028] Preferably, in step (2), the pH of the system is adjusted to 7-8 using NaOH aqueous solution; in step (1), the pH of the system is adjusted to 9-10 using NaOH aqueous solution.

[0029] A high-temperature, high-salt soluble temporary plugging microsphere for acid fracturing is prepared using the method described above.

[0030] This invention is based on micro and nano particles that can be completely dissolved by acid. It utilizes the rigid support of these particles and the flexible soluble polymer to form high-performance soluble plugging microspheres for acid fracturing. By introducing functional monomers, the stability of these plugging microspheres against iron ions and their temperature and salt resistance are enhanced. By grafting slow-dissolving monomers, the polymer can be smoothly introduced into the fracture to achieve the plugging performance.

[0031] Advantages of this invention:

[0032] The temporary plugging microspheres provided by this invention are formed by bridging a slow-dissolving polymer onto the surface of rigid, acid-soluble micro-nano particles to create a core-shell structure. These microspheres can completely dissolve in acidic environments, exhibiting good plugging performance, as well as good resistance to iron ions and salt and temperature resistance. Detailed Implementation

[0033] Example 1

[0034] A method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing includes the following steps:

[0035] Step (1): Under stirring, 5g of micro / nano particles are dispersed in 100mL of 80wt% ethanol aqueous solution, 0.5g of aminopropyltrimethoxysilane is added, nitrogen gas is introduced to remove oxygen for 30min, the mixture is stirred evenly, the pH of the system is adjusted to 9 with NaOH aqueous solution, and then the temperature is raised to 45℃ and refluxed for 24h. After centrifugation, the mixture is washed 3 times with anhydrous ethanol and dried at 60℃ for 24h. The micro / nano particles are calcium hydroxide particles with a particle size of 500nm.

[0036] Step (2): Weigh 3g of the product from step (1) and disperse it in 40mL of deionized water. Stir until homogeneous, then add 7g of citralic acid, 7g of dimethomorpholine and 6g of 1-(3-sulfonylpropyl)-2-vinylpyridinium inner salt in sequence. Stir until dissolved, adjust the pH of the system to 7.5 with 5wt% NaOH aqueous solution, heat to 60℃, add 3g of potassium persulfate, stir until homogeneous, and reflux for 8h.

[0037] Step (3): Keep the reaction temperature of step (2) at 60°C, add 20g of methacrylate, 10g of sorbitol and 7g of polybutylene succinate in sequence, stir to dissolve, add 3g of dimethyl azobisisobutyrate, stir, reflux for 6h, then transfer to a high temperature and high pressure reactor and seal, heat to 140°C and react for 4h.

[0038] Step (4): Place the product from step (3) in an oven and dry it at 100°C for 12 hours. Then crush it and pass it through a 20-120 mesh sieve.

[0039] Example 2

[0040] A method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing includes the following steps:

[0041] Step (1): Under stirring, 10g of micro / nano particles are dispersed in 100mL of 85wt% ethanol aqueous solution, 3g of N-aminoethyl-γ-aminopropyltrimethoxysilane is added, nitrogen gas is introduced to remove oxygen for 40min, the mixture is stirred evenly, the pH of the system is adjusted to 10 with NaOH aqueous solution, and then the temperature is raised to 60℃ and refluxed for 12h. After centrifugation, the mixture is washed 3 times with anhydrous ethanol and dried at 50℃ for 30h. The micro / nano particles are iron oxide particles with a particle size of 1μm.

[0042] Step (2): Weigh 3g of the product from step (1) and disperse it in 44mL of deionized water. Stir until homogeneous, then add 7.8g of acrylic acid, 4.5g of N-vinylpyrrolidone carboxylate and 2.7g of 2-acrylamido-2-methylpropanesulfonic acid in sequence. Stir until dissolved, adjust the pH of the system to 7 with 5wt% NaOH aqueous solution, heat to 65℃, add 1.5g of ammonium persulfate, stir until homogeneous, and reflux for 5h.

[0043] Step (3): Keep the reaction temperature of step (2) at 65°C, add 15g of propylene alcohol, 15g of glycerol and 8g of polylactic acid in sequence, stir to dissolve, add 3g of azobisisobutyronitrile, stir, reflux for 4h, then transfer to a high temperature and high pressure reactor and seal, heat to 120°C and react for 5h.

[0044] Step (4): Place the product from step (3) in an oven and dry it at 110°C for 10 hours. Then crush it and pass it through a 20-120 mesh sieve.

[0045] Example 3

[0046] A method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing includes the following steps:

[0047] Step (1): Under stirring, 8g of micro / nano particles were dispersed in 100mL of 85wt% ethanol aqueous solution, and 1.6g of γ-diethylenetriaminepropylmethyldimethoxysilane was added. Nitrogen gas was introduced to remove oxygen for 30min, and the mixture was stirred evenly. The pH of the system was adjusted to 10 with NaOH aqueous solution, and then the temperature was raised to 50℃ and refluxed for 18h. After centrifugation, the mixture was washed 3 times with anhydrous ethanol and dried at 70℃ for 20h. The micro / nano particles were magnesium carbonate particles with a particle size of 700nm.

[0048] Step (2): Weigh 6g of the product from step (1) and disperse it in 34mL of deionized water. Stir until homogeneous, then add 8g of pentene edible acid, 8g of 4-vinylpyridine and 4g of sodium vinylbenzene sulfonate in sequence. Stir until dissolved, adjust the pH of the system to 8 with 5wt% NaOH aqueous solution, heat to 50℃, add 4g of tert-butyl peroxide, stir until homogeneous, and reflux for 7h.

[0049] Step (3): Keep the reaction temperature of step (2) at 50°C, add 25g of polyethylene glycol diacrylate, 10g of pentaerythritol and 5g of polybutylene succinate in sequence, stir to dissolve, add 4g of sodium persulfate, stir, reflux for 8h, then transfer to a high temperature and high pressure reactor and seal, heat to 160°C and react for 2h.

[0050] Step (4): Place the product from step (3) in an oven and dry it at 110°C for 10 hours. Then crush it and pass it through a 20-120 mesh sieve.

[0051] Example 4

[0052] A method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing includes the following steps:

[0053] Step (1): Under stirring, 5g of micro / nano particles are dispersed in 100mL of 85wt% ethanol aqueous solution, 1g of aminopropylmethyldiethoxysilane is added, nitrogen gas is introduced to remove oxygen for 35min, the mixture is stirred evenly, the pH of the system is adjusted to 10 with NaOH aqueous solution, and then the temperature is raised to 45℃ and refluxed for 24h. After centrifugation, the mixture is washed 3 times with anhydrous ethanol and dried at 70℃ for 20h. The micro / nano particles are iron hydroxide particles with a particle size of 700nm.

[0054] Step (2): Weigh 3g of the product from step (1) and disperse it in 40mL of deionized water. Stir until homogeneous, then add 7g of maleic acid, 6g of vinylimidazole and 7g of methylpropenesulfonic acid in sequence. Stir until dissolved, adjust the pH of the system to 8 with 5wt% NaOH aqueous solution, heat to 50℃, add 2g of hydrogen peroxide, stir until homogeneous, and reflux for 7h.

[0055] Step (3): Keep the reaction temperature of step (2) at 50°C, add 15g dicyclopentyl acrylate, 15g polyethylene glycol and 7g carboxymethyl cellulose in sequence, stir to dissolve, add 3g sodium sulfite, stir, reflux for 8h, then transfer to a high temperature and high pressure reactor and seal, heat to 150°C and react for 2h.

[0056] Step (4): Place the product from step (3) in an oven and dry it at 110°C for 10 hours. Then crush it and pass it through a 20-120 mesh sieve.

[0057] Comparative Example 1

[0058] It does not contain the anti-ferric monomer citrate, and is otherwise the same as in Example 1.

[0059] Comparative Example 2

[0060] It does not contain the synergist polybutylene succinate, and is otherwise the same as in Example 1.

[0061] Performance testing

[0062] 1. Density, particle size, and expansion rate testing

[0063] The density, particle size, and expansion rate of the temporarily plugged microspheres were measured using an electronic digital display density meter, a laser particle size analyzer, and the volumetric method. The results are shown in Table 1.

[0064] Table 1. Results of density, particle size, and expansion rate

[0065]

[0066] As shown in Table 1, the density of the temporary plugging microspheres is 1.25-1.4 g / cm³. 3 The particle size is 0.03-0.85 mm, and the expansion rate reaches 2.4-3.9 times. It can be seen that this temporary plugging agent can be successfully transported to the front end of the crack and expand in the pores to achieve sealing and diversion.

[0067] 2. Solubility test

[0068] Prepare 100 mL of 5% dilute hydrochloric acid. At different temperatures, add 5 g of soluble temporary plugging microspheres to the solution and stir until it becomes transparent. Record the time required for complete dissolution. At room temperature, evaluate the residue content and reservoir damage of the dissolved samples according to the experimental test methods in the standards SY / T6376-2008 "General Technical Conditions for Fracturing Fluids" and SY / T "Technical Requirements for Water-Based Fracturing Fluids". The test evaluation results are shown in Table 2.

[0069] Table 2. Solubility of samples in acid and evaluation results of reservoir damage after dissolution.

[0070]

[0071] As shown in Table 2, when the temperature reaches 130℃, the dissolution time of the samples in all four examples meets the requirements for on-site temporary plugging construction. Simultaneously, the resulting reservoir damage rate is very low, indicating that the soluble plugging microspheres cause minimal damage to the reservoir after dissolution.

[0072] 3. Sealing strength testing

[0073] 100 mL of 5 wt% soluble temporary plugging microsphere dispersion fluid was prepared using 5% dilute hydrochloric acid solution. Artificial rock cores were cut to simulate cracks with a crack width of 0.2-2 mm. The plugging strength was evaluated by testing the sample injection pressure at 50℃ using a core displacement device. The test results are shown in Table 3.

[0074] Table 3 Evaluation results of sample plugging strength

[0075]

[0076] As shown in Table 3, the plugging strength increases rapidly with increasing plugging time and then gradually stabilizes, exhibiting strong plugging performance. However, the plugging strength begins to decrease as the soluble plugging microspheres gradually dissolve. The synergist in this invention can significantly improve the plugging performance.

[0077] 4. Temperature resistance test

[0078] Similar to the above-mentioned sealing strength test, the maximum sealing strength of the samples was tested at different temperatures, and the results are shown in Table 4.

[0079] Table 4. Effect of temperature on sample plugging performance

[0080]

[0081] As shown in Table 4, the sealing strength of the samples gradually decreased with increasing temperature. When the temperature reached 130℃, the maximum sealing strength of Example 1 still reached 35.4MPa, demonstrating good overall temperature resistance and meeting the requirements of on-site construction. The sealing performance of Comparative Example 2 decreased significantly.

[0082] 5. Salt and iron ion resistance testing

[0083] The plugging strength of the samples at 50℃ was evaluated by changing the mineralization and iron ion content of the 5% dilute hydrochloric acid solution. The evaluation method for plugging strength is the same as above, and the test results are shown in Table 5.

[0084] Table 5. Effects of mineralization and iron ion content on the plugging performance of the example samples.

[0085]

[0086] Table 5 shows that when the mineralization exceeds 100,000 mg / L, the maximum plugging strength of the sample decreases significantly, and the temporary plugging performance weakens. Therefore, the optimal mineralization environment that the sample can adapt to under the action of the rigid ring structure on the surface of the temporary plugging microspheres is equal to or less than 100,000 mg / L. Similarly, when the iron ion concentration reaches 6,000 mg / L, the plugging pressure of the temporary plugging microspheres decreases significantly. When the iron ion concentration is 5,000 mg / L, the present invention still exhibits excellent iron ion resistance stability. However, in Comparative Example 1, without the presence of iron ion-resistant monomers, the plugging strength decreases significantly with increasing iron ion concentration.

Claims

1. A method for preparing high-temperature resistant, high-salt soluble temporary plugging microspheres for acid fracturing, characterized in that: Includes the following steps: Step (1): Disperse the micro-nano particles in an ethanol aqueous solution under stirring, add silane coupling agent, remove oxygen for 30-40 min, stir evenly, adjust the pH of the system to 9-10, then heat to 45-60℃ and reflux for 12-24 h, centrifuge, wash with anhydrous ethanol, and dry; wherein, the micro-nano particles can dissolve in acidic solution; Step (2): Disperse the product from step (1) in deionized water, then add the functional monomer and stir until dissolved. Adjust the pH of the system to 7-8, heat to 50-65℃, add the first initiator, stir evenly, and reflux for 5-8 hours. The functional monomer is an iron-resistant functional monomer, a temperature-resistant monomer, and a salt-resistant monomer. Step (3): Maintain the reaction temperature of step (2), add the slow-dissolving monomer, polyol and synergist in sequence, stir to dissolve, add the second initiator, stir, reflux for 4-8 hours, then seal, heat to 120-160℃ and react for 2-5 hours; Step (4): Drying, pulverizing, and sieving; The iron-resistant functional monomer is at least one of acrylic acid, fumaric acid, maleic acid, citracic acid, itaconic acid, and pentenoic acid. The slow-dissolving monomer is at least one of allyl alcohol, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, dicyclopentyl acrylate, and vinyl acetate; The synergist is at least one of polylactic acid, chitosan, polyglycolic acid, polybutylene succinate, and carboxymethyl cellulose; The thermoresistant monomer is any one of N-vinylpyrrolidone carbamate, 4-vinylpyridine, 1,1-stilbene, acryloylmorpholine, vinylimidazole, and styrene; The salt-resistant monomer is any one of 2-acrylamido-2-methylpropanesulfonic acid, 1-(3-sulfonylpropyl)-2-vinylpyridinium inner salt, sodium vinylbenzenesulfonate, methacryloylethyl sulfobetaine, and methacrylic sulfonic acid.

2. The method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing according to claim 1, characterized in that: In step (1), the concentration of ethanol in the aqueous ethanol solution is 80-85 wt%; the micro-nano particles account for 5-10% of the mass of the aqueous ethanol solution, and the silane coupling agent accounts for 10-30% of the mass of the micro-nano particles.

3. The method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing according to claim 1, characterized in that: In steps (2) and (3), the total mass of the product, functional monomer, slow-dissolving monomer, polyol, synergist, and deionized water in step (1) is 100%, and the content of each substance is as follows: 3-6% of the product in step (1), 15-20% of the functional monomer, 15-25% of the slow-dissolving monomer, 10-15% of the polyol, 5-8% of the synergist, and the remainder is water; The first initiator accounts for 10-20% of the functional monomer; the second initiator accounts for 15-20% of the slow-dissolving monomer mass. The total mass of the functional monomers is calculated as 100%, and the content of each monomer is as follows: the content of the iron ion resistant functional monomer is 35-52%, the content of the temperature resistant monomer is 30-40%, and the content of the salt resistant monomer is 18-35%.

4. The method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing according to claim 1, characterized in that: The first initiator is at least one of organic peroxide and inorganic peroxide; The second initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, organic peroxide, and inorganic peroxide.

5. The method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing according to claim 4, characterized in that: The micro-nano particles are any one of iron(II,III) oxide, iron(II) hydroxide, magnesium carbonate, magnesium(II) hydroxide, and calcium(II) hydroxide, and the particle size of the micro-nano particles is 500 nm-1 μm. The silane coupling agent is any one of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropylmethyldiethoxysilane, N-aminoethyl-γ-aminopropyltrimethoxysilane, N-aminoethyl-γ-aminopropyltriethoxysilane, and γ-diethylenetriaminepropylmethyldimethoxysilane. The polyol is any one of glycerol, pentaerythritol, sorbitol, and polyethylene glycol.

6. The method for preparing high-temperature resistant, high-salt soluble plugging microspheres for acid fracturing according to claim 1, characterized in that: In step (1), the drying conditions are drying at 50-70℃ for 20-30 hours; In step (4), the drying conditions are drying at 100-110℃ for 10-15 hours; the sieving is passing through a 20-120 mesh sieve.

7. A type of high-temperature resistant, high-salt soluble temporary plugging microsphere for acid fracturing, characterized in that: It is prepared by the preparation method described in any one of claims 1-6.

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