Long-acting polymer microsphere as well as preparation method and application thereof

Abstract

The invention provides a polymer microsphere as well as a preparation method and application thereof. The polymer microspheres comprise an initial cross-linked network and a later reinforcing cross-linking agent; the later reinforcing cross-linking agent is modified polyethyleneimine with an acetyl group, and the acetyl group is a cross-linking delay protection unit; the initial cross-linked network is formed by copolymerization of components including acrylamide, an anionic monomer, a cationic monomer, a nonionic monomer and a cross-linking agent. The preparation method comprises the following steps: mixing the raw materials in parts by weight, emulsifying, and reacting to obtain the polymer microspheres. The prepared polymer microspheres have higher plugging efficiency after being aged for a long time at high temperature, the plugging validity period of the microspheres can be obviously prolonged, and the polymer microspheres can be applied to oil and gas field development under high-temperature oil reservoir conditions.

Description

Technical Field

[0001] This invention relates to polymers used in the field of oil and gas field development, and more specifically, to a long-lasting polymer microsphere, its preparation method, and its application. Background Technology

[0002] The current international situation is volatile, and the trend of deglobalization is intensifying. Energy supply is closely related to national strategic security. Crude oil is the most important component of the current energy supply, and a stable supply of crude oil is crucial to national energy security.

[0003] Because most of my country's oilfields are terrestrial sedimentary reservoirs with complex geological conditions and poor burial conditions, effective development is both difficult and inefficient. In particular, after years of water injection development, a large number of high-permeability water channels have formed, making it difficult to further improve the sweep efficiency. Ineffective injection and ineffective circulation have exacerbated the high cost of oil production, seriously affecting the stable supply of crude oil.

[0004] Profile control and water shut-off are common water control and oil enhancement measures. Polymer microspheres, with their excellent injectability, good stability, and ability to migrate deep underground, have been widely used. However, a current problem with pre-crosslinked products is that the crosslinked structure is obtained through a reaction on the surface. During underground service, under the influence of heat and oxygen, the molecular chains and crosslinking points are gradually degraded. Therefore, the overall sealing performance of pre-crosslinked products gradually deteriorates with service life. This results in insufficient sealing effectiveness for some high-permeability water channel blockages requiring long-term sealing, which is detrimental to improving oilfield quality and efficiency.

[0005] Effectively reinforcing the crosslinked network during its service life is a relatively effective solution. Reinforcing the crosslinked network requires the ability to effectively undergo macromolecular reactions after polymerization, thereby increasing the crosslinking density. Commonly used crosslinking agents that can react with polyacrylamide molecules to form macromolecular crosslinks include phenolic and metal ion crosslinking agents. However, phenolic crosslinking agents cannot coexist under free radical conditions, and metal ion crosslinking reactions are too rapid, both of which are unfavorable for use. Polyethyleneimine is a type of chemical agent that can effectively react with polyacrylamide at high temperatures to form crosslinks, but the crosslinking reaction between ordinary polyethyleneimine and polyacrylamide is still relatively fast, which cannot meet the long-term effectiveness requirements of deep plugging regulation. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a polymer microsphere, its preparation method, and its application. The polymer microspheres prepared by this invention can automatically reinforce the polymer network during their service life to compensate for the degradation of the polymer network caused by heat and oxygen.

[0007] This invention uses modified polyethyleneimine with acetyl groups as a post-reinforcing crosslinking agent. By introducing acetylated polyethyleneimine into the polymerization system of polyacrylamide microspheres, the imino and amino groups on the polyethyleneimine are protected by acetyl groups during the polymerization process and in the early stage of microsphere entry into the formation, and will not react with polyacrylamide. With the action of heat and oxygen, in the aqueous solution of high-temperature oil reservoirs, the acetamide groups hydrolyze to form imino and amino groups on the polyethyleneimine backbone, which then react with polyacrylamide to form crosslinking points, reinforcing the crosslinking network of polyacrylamide and improving the long-term sealing effectiveness of the microspheres.

[0008] Acetylated polyethyleneimine can effectively delay crosslinking, slow down the crosslinking reaction rate, and achieve a match between the time and depth of crosslinking reinforcement and the requirements for long-term performance. This solves the problem of effectively reinforcing the crosslinking network in a system that can be used for long-term service in a high-temperature aqueous solution environment of polyacrylamide microspheres, thereby improving the service life of polyacrylamide microspheres.

[0009] One objective of this invention is to provide a polymer microsphere comprising an initial crosslinking network and a later reinforcing crosslinking agent;

[0010] The post-reinforcing crosslinking agent is modified polyethyleneimine with acetyl groups, wherein the acetyl groups are crosslinking delay protection units;

[0011] Preferably, the post-reinforcing crosslinking agent contains the following structural units:

[0012] The above structural units may or may not be repeated.

[0013] The initial cross-linking network is formed during the microsphere reaction synthesis. During this initial cross-linking network formation reaction, the later-stage reinforcing cross-linking agent is merely mixed in and does not participate in the reaction. The later-stage reinforcing cross-linking agent only participates in the reaction during the use of the microspheres, further reinforcing the network.

[0014] In a preferred embodiment of the present invention,

[0015] The initial crosslinking network is formed by copolymerization of components including acrylamide, anionic monomers, cationic monomers, nonionic monomers and crosslinking agents;

[0016] The structural formula of the post-reinforcing crosslinking agent is shown in formula (Ⅰ):

[0017]

[0018] Among them, the molecular weight of the post-reinforcing crosslinking agent in formula (Ⅰ) is 1500 to 10000;

[0019] The degree of acetylation of the post-reinforcing crosslinking agent is 10-100%, preferably 15-75%, such as a range of any two values ​​of 15%, 25%, 35%, 45%, 55%, 65%, 75%, or above, for example, 15-25%. The degree of acetylation refers to the proportion of acetylated amino groups to the total number of amino groups.

[0020] In a preferred embodiment of the present invention,

[0021] The polymer microspheres are obtained by reacting a reaction system containing the following components, in parts by weight:

[0022] Acrylamide: 5-30 parts by weight; preferably 20-25 parts by weight;

[0023] 1-25 parts by weight of anionic monomer; preferably 5-10 parts by weight;

[0024] 0-5 parts by weight of cationic monomer; preferably 0.5-1 parts by weight;

[0025] 0-10 parts by weight of nonionic monomer; preferably 1-7.5 parts by weight;

[0026] The crosslinking agent is used in amounts of 0.001 to 0.5 parts by weight; preferably 0.01 to 0.25 parts by weight.

[0027] The amount of the post-reinforcing crosslinking agent is 0.005 to 0.5 parts by weight; preferably 0.01 to 0.5 parts by weight.

[0028] The anionic monomer is preferably in the range of any two values ​​consisting of 5, 6, 7.5, 9, 10 parts by weight or more; the crosslinking agent is preferably in the range of any two values ​​consisting of 0.01, 0.05, 0.1, 0.15, 0.2, 0.25 parts by weight or more, for example, 0.1 to 0.25 parts by weight; the post-reinforcing crosslinking agent is preferably in the range of any two values ​​consisting of 0.01, 0.05, 0.1, 0.2, 0.3, 0.5 parts by weight or more, for example, 0.05 to 0.5 parts by weight.

[0029] In a preferred embodiment of the present invention,

[0030] The anionic monomer is at least one of the following compounds and their alkali metal salts: acrylic acid, methacrylic acid, p-vinylbenzenesulfonic acid, maleic acid, fumaric acid, vinylbenzenesulfonic acid, allyl sulfonic acid, allylbenzenesulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

[0031] The cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropyltrimethylammonium chloride, dimethylethylallylammonium chloride, dimethyldiallylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, and methacryloyloxyethyldimethylbenzylammonium chloride.

[0032] The nonionic monomer is at least one of the following: methacrylamide, dimethacrylamide, diethylacrylamide, hydroxymethylacrylamide, hydroxyethylacrylamide, dimethylaminopropylmethacrylamide, hydroxymethyl methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, vinylpyrrolidone, and tert-butylacrylamide.

[0033] The crosslinking agent is at least one of methylene bisacrylamide, divinylbenzene, diallyl phthalate, ethyl diallyl cyanoacetate, polyethylene glycol diacrylate, ethylene glycol diacrylate, glycerol diacrylate, pentaerythritol diacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethylene glycol diallyl ether, glycerol diallyl ether, glycerol triallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, and pentaerythritol tetraallyl ether.

[0034] In a preferred embodiment of the present invention,

[0035] The reaction system of the polymer microspheres also includes the following components in parts by weight:

[0036] The azo initiator is used in amounts of 0.0005 to 0.05 parts by weight; preferably 0.001 to 0.01 parts by weight.

[0037] The oxidant is used in amounts of 0.00005 to 0.005 parts by weight; preferably 0.0001 to 0.001 parts by weight.

[0038] The reducing agent is 0.00005 to 0.005 parts by weight; preferably 0.0001 to 0.001 parts by weight.

[0039] Water 10-100 parts by weight; preferably 25-50 parts by weight;

[0040] 40-100 parts by weight of oil solvent; preferably 50-75 parts by weight.

[0041] The emulsifier is 2 to 20 parts by weight; preferably 2.5 to 15 parts by weight.

[0042] The preferred amounts of the azo initiator are within the range of any two values, such as 0.001, 0.003, 0.005, 0.008, 0.01 parts by weight or more, for example, 0.005 to 0.01 parts by weight; the preferred amounts of the oxidant are within the range of any two values, such as 0.0001, 0.0003, 0.0005, 0.0008, 0.001 parts by weight or more, for example, 0.0003 to 0.001 parts by weight; and the preferred amounts of the reducing agent are within the range of 0.0001, 0.0003, 0.0005, 0.0008, 0.001 parts by weight or more. The range of any two values ​​consisting of parts by weight or more, for example, 0.0005 to 0.001 parts by weight; water is preferably a range of any two values ​​consisting of 25, 30, 35, 40, 45, or 50 parts by weight or more, for example, 25 to 30 parts by weight; oil solvent is preferably a range of any two values ​​consisting of 50, 55, 60, 65, 70, or 75 parts by weight or more, for example, 50 to 60 parts by weight; emulsifier is preferably a range of any two values ​​consisting of 2.5, 5, 7.5, 10, 12.5, or 15 parts by weight or more, for example, 10 to 15 parts by weight.

[0043] In a preferred embodiment of the present invention,

[0044] The azo initiator is at least one of azobisisobutyronitrile, azobisisovalerate, azobisisoheptane, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2,2'-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobis(2,5-dimethyl-6-carboxy)hexanonitrile, and 4,4'-azobis(4-cyanopentanoic acid);

[0045] The oxidizing agent is at least one of the following: ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, tert-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxide, and dicyclohexyl peroxide.

[0046] The reducing agent is at least one of the following: sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N,N-dimethylaniline, tartaric acid, ferrous sulfate, N,N-diethylaniline, ferrous pyrophosphate, silver nitrate, thiol, ferrous chloride, tetraethyleneimine, glycerol, and pentaerythritol.

[0047] The oil solvent is at least one of aliphatic hydrocarbons, aromatic hydrocarbons, and mineral oil; preferably, the aliphatic hydrocarbon is at least one of cyclohexane, hexane, heptane, and octane; the aromatic hydrocarbon is at least one of benzene, toluene, ethylbenzene, and xylene; and the mineral oil is at least one of liquid paraffin, white oil, gasoline, diesel, and kerosene.

[0048] The emulsifier is at least two of the following: fatty alcohol polyoxypropylene polyoxyethylene ether, aromatic alcohol polyoxypropylene polyoxyethylene ether, fatty acid polyoxypropylene polyoxyethylene ester, fatty amine polyoxypropylene polyoxyethylene ether, sorbitan oleate, sorbitan stearate, sorbitan palmitate, and sorbitan laurate, preferably two. More preferably, the HLB value of the composite emulsion system is adjusted to be between 5 and 6 by adjusting the ratio of the two emulsifiers. Generally, two emulsifiers are used to adjust the hydrophilic-lipophilic balance, but more than two are also acceptable. The PO segment length in "polyoxypropylene / polyoxyethylene ether" can be 0, that is, "polyoxypropylene / polyoxyethylene ether" refers to polyoxyethylene ether or polyoxypropylene polyoxyethylene ether.

[0049] A second objective of this invention is to provide a method for preparing polymer microspheres, comprising:

[0050] The components are mixed according to the specified weight proportions, and after emulsification, the polymer microspheres are obtained by reaction.

[0051] In a preferred embodiment of the present invention,

[0052] The method includes the following steps:

[0053] (1) Mix the components including acrylamide, anionic monomer, cationic monomer, nonionic monomer, crosslinking agent, and post-crosslinking reinforcement agent according to the weight ratio to obtain a solution. After adjusting the pH value, add an azo initiator and mix to obtain an aqueous phase.

[0054] (2) Mix the emulsifier and the oil solvent to obtain the oil phase;

[0055] (3) The aqueous phase obtained in step (1) is added to the oil phase obtained in step (2) and emulsified to obtain an emulsion;

[0056] (4) First, add the oxidant to the emulsion obtained in step (3) and mix, then add the reducing agent, and after the reaction, the polymer microspheres are obtained.

[0057] In a preferred embodiment of the present invention,

[0058] Step (1),

[0059] Adjust the pH value with an alkaline solution, such as an aqueous solution of sodium hydroxide.

[0060] Adjust the pH value to between 5.8 and 6.2;

[0061] Adjust the temperature of the aqueous solution to not exceed 20℃, and add an azo initiator;

[0062] Step (3),

[0063] Mixing is carried out under stirring;

[0064] Mixing is carried out under continuous nitrogen purging, the purpose of which is to remove oxygen;

[0065] Stir and continuously purge with nitrogen for at least 1 hour;

[0066] Step (4),

[0067] An aqueous solution with added oxidizing agent;

[0068] After adding the oxidant, stir and mix for 1–10 minutes;

[0069] An aqueous solution containing a reducing agent; the reducing agent is added dropwise.

[0070] Stop adding reducing agent when the temperature of the system exceeds 50°C;

[0071] The reaction temperature is 55–70℃. After the reducing agent is added, the system temperature spontaneously rises to the highest point, and then the reaction is carried out at this temperature.

[0072] The reaction time is 1 to 2 hours.

[0073] The third objective of this invention is to provide an application of polymer microspheres in oil and gas field development, preferably in oil and gas field development with reservoir conditions at temperatures above 90°C, and more preferably in oil and gas field development with reservoir conditions at temperatures above 110°C.

[0074] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0075] This invention introduces acetylated polyethyleneimine into the polymerization system of polyacrylamide microspheres. During the polymerization process and in the early stage of microspheres entering the formation, the imino and amino groups on the polyethyleneimine are protected by acetyl groups and will not react with polyacrylamide. With the action of heat and oxygen, in the aqueous solution of high-temperature oil reservoirs, the acetamide groups hydrolyze to form imino and amino groups on the polyethyleneimine backbone, which then react with polyacrylamide to form crosslinking points, strengthen the crosslinking network of polyacrylamide, and improve the long-term sealing effectiveness of the microspheres.

[0076] The solution addresses the issue of effectively reinforcing the cross-linked network of polyacrylamide microspheres during long-term service in high-temperature aqueous environments, thereby extending the service life of the polyacrylamide microspheres.

[0077] The polymer microspheres obtained by the technical solution of the present invention, after aging in brine with a mineralization of 120,000 mg / L and a calcium and magnesium ion content of 2,000 mg / L at 110°C for 4 months, retain a core plugging rate of more than 85%, and after aging at 130°C for 4 months, retain a core plugging rate of more than 80%. Detailed Implementation

[0078] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0079] All raw materials used in the examples are commercially available.

[0080] The acetylated polyethyleneimine used in this invention was purchased from Sigma-Aldrich, catalog number 913235 (https: / / www.sigmaaldrich.cn / CN / zh / product / aldrich / 913235), with a degree of acetylation of 20%.

[0081] Test method:

[0082] Plugging rate: The polymer microspheres obtained in the examples or comparative examples were prepared into a 0.5 wt% solution in brine with a mineralization of 120,000 mg / L and a calcium and magnesium ion content of 2,000 mg / L. The plugging rate of the microspheres for a 500 mD permeability core was measured at 110°C and 130°C, and recorded as the initial plugging rate. Subsequently, the prepared solution was deoxygenated in a glove box until the oxygen content was less than 2 ppm, sealed in a high-pressure container, and aged in aging chambers at 110°C and 130°C for 4 months. After aging, the solutions were taken out, and the plugging rate after aging was measured using the above method. The plugging rate retention rate was calculated by multiplying the ratio of the plugging rate after aging to the initial plugging rate by 100%.

[0083] The numbers in the examples and comparative examples refer to parts by weight.

[0084] Examples 1-3, Comparative Examples 1-3:

[0085] The components and dosages of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0086] The specific synthesis process is as follows:

[0087] Acrylamide, anionic monomer, cationic monomer, nonionic monomer, crosslinking agent, and post-reinforcing crosslinking agent were weighed according to the amounts specified in Table 1 and prepared into homogeneous solutions in deionized water. The pH was adjusted to between 5.8 and 6.2 using a 32 wt% sodium hydroxide aqueous solution. The temperature of the aqueous solution was adjusted to not exceed 20°C, and an azo initiator was added and stirred until homogeneous. The emulsifier and oil solvent were prepared into homogeneous solutions. The above oil phase was added to the reactor, and stirring was started. The aqueous phase was added, and nitrogen gas was continuously purged for at least 1 hour. The oxidant aqueous solution was added to the reactor and stirred continuously for 10 minutes. The reducing agent aqueous solution was added dropwise to the reactor until the temperature spontaneously rose to 50°C, at which point the dropwise addition was stopped. After the system temperature reached its maximum point, it was kept in a water bath at 60°C for 1 hour. The product was obtained.

[0088] The polymer microspheres obtained in Examples 1-3 and Comparative Examples 1-3 were prepared into 0.5 wt% solutions in brine with a mineralization of 120,000 mg / L and a calcium and magnesium ion content of 2,000 mg / L. The plugging rates of these solutions on 500 mD permeability cores were measured at 110°C and 130°C, respectively, and recorded as the initial plugging rates. Subsequently, the prepared solutions were deoxygenated in a glove box until the oxygen content was less than 2 ppm, sealed in high-pressure containers, and aged for 4 months in aging chambers at 110°C and 130°C, respectively. The aged solutions were then removed, and the plugging rates after aging were measured using the same method. The plugging rate retention rate was calculated by multiplying the ratio of the aged plugging rate to the initial plugging rate by 100%, as shown in Appendix Table 2.

[0089]

[0090] Table 2. Plugging rates of the products from Examples 1-3 and Comparative Examples 1-3 after aging at different temperatures.

[0091]

[0092] As can be seen from Table 2:

[0093] Compared with Comparative Example 1, Example 1 showed a 66.3% increase in the plugging rate after aging at 110°C for 4 months and a 69.5% increase after aging at 130°C for 4 months.

[0094] Compared with Comparative Example 2, Example 2 showed a 66.4% increase in the plugging rate after aging at 110°C for 4 months and a 71% increase in the plugging rate after aging at 130°C for 4 months.

[0095] Compared with Comparative Example 3, Example 3 showed a 68.6% increase in the plugging rate after aging at 110°C for 4 months and a 73.5% increase after aging at 130°C for 4 months.

[0096] Test results show that, compared with the polymer microspheres prepared in Comparative Examples 1-3 without the addition of a post-reinforcing crosslinking agent, the polymer microspheres prepared in Examples 1-3 have a stronger blocking efficiency after long-term aging at high temperature, and can significantly extend the blocking effectiveness of the microspheres.

Claims

1. A polymer microsphere comprising an initial crosslinking network and a subsequent reinforcing crosslinking agent; The post-reinforcing crosslinking agent is modified polyethyleneimine with acetyl groups, wherein the acetyl groups are crosslinking delay protection units; Preferably, the post-reinforcing crosslinking agent contains the following structural units:

2. The polymer microspheres as described in claim 1, characterized in that: The initial crosslinking network is formed by copolymerization of components including acrylamide, anionic monomers, cationic monomers, nonionic monomers, and crosslinking agents; and / or, The structural formula of the post-reinforcing crosslinking agent is shown in formula (Ⅰ): And / or, The degree of acetylation of the post-reinforcing crosslinking agent is 10-100%, preferably 15-75%.

3. The polymer microspheres as described in claim 1, characterized in that: The polymer microspheres are obtained by reacting a reaction system containing the following components, in parts by weight:

4. The polymer microspheres as described in claim 2 or 3, characterized in that: The anionic monomer is at least one of the following compounds and their alkali metal salts: acrylic acid, methacrylic acid, p-vinylbenzenesulfonic acid, maleic acid, fumaric acid, vinylbenzenesulfonic acid, allyl sulfonic acid, allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; and / or, The cationic monomer is at least one selected from the following: methacryloyloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropyltrimethylammonium chloride, dimethylethylallylammonium chloride, dimethyldiallylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, and methacryloyloxyethyldimethylbenzylammonium chloride; and / or, The nonionic monomer is at least one selected from the following: methacrylamide, dimethacrylamide, diethylacrylamide, hydroxymethylacrylamide, hydroxyethylacrylamide, dimethylaminopropylmethacrylamide, hydroxymethyl methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, vinylpyrrolidone, and tert-butylacrylamide; and / or, The crosslinking agent is at least one of methylene bisacrylamide, divinylbenzene, diallyl phthalate, ethyl diallyl cyanoacetate, polyethylene glycol diacrylate, ethylene glycol diacrylate, glycerol diacrylate, pentaerythritol diacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethylene glycol diallyl ether, glycerol diallyl ether, glycerol triallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, and pentaerythritol tetraallyl ether.

5. The polymer microspheres as described in claim 2 or 3, characterized in that: The reaction system of the polymer microspheres also includes the following components in parts by weight:

6. The polymer microspheres as described in claim 5, characterized in that: The azo initiator is at least one selected from azobisisobutyronitrile, azobisisovalerate, azobisisoheptane, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2,2'-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobis(2,5-dimethyl-6-carboxy)hexanenitrile, and 4,4'-azobis(4-cyanopentanoic acid); and / or, The oxidizing agent is at least one selected from the following: ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, tert-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, dicumene peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxide, and dicyclohexyl peroxide; and / or, The reducing agent is at least one selected from sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N,N-dimethylaniline, tartaric acid, ferrous sulfate, N,N-diethylaniline, ferrous pyrophosphate, silver nitrate, thiols, ferrous chloride, tetraethyleneimine, glycerol, and pentaerythritol; and / or, The oil solvent is at least one of aliphatic hydrocarbons, aromatic hydrocarbons, and mineral oil; preferably, the aliphatic hydrocarbon is at least one of cyclohexane, hexane, heptane, and octane; the aromatic hydrocarbon is at least one of benzene, toluene, ethylbenzene, and xylene; and the mineral oil is at least one of liquid paraffin, white oil, gasoline, diesel oil, and kerosene; and / or, The emulsifier is at least two of the following: fatty alcohol polyoxypropylene / polyoxyethylene ether, aromatic alcohol polyoxypropylene / polyoxyethylene ether, fatty acid polyoxypropylene / polyoxyethylene ester, fatty amine polyoxypropylene / polyoxyethylene ether, sorbitan oleate, sorbitan stearate, sorbitan palmitate, and sorbitan laurate, preferably two; more preferably, the HLB value of the composite emulsion system is between 5 and 6 by adjusting the ratio of the two emulsifiers.

7. A method for preparing polymer microspheres according to any one of claims 1 to 6, comprising: The components are mixed according to the specified weight proportions, and after emulsification, the polymer microspheres are obtained by reaction.

8. The method for preparing polymer microspheres as described in claim 7, characterized in that... The method includes the following steps: (1) Mix the components including acrylamide, anionic monomer, cationic monomer, nonionic monomer, crosslinking agent, and post-reinforcing crosslinking agent according to the weight ratio to obtain a solution. After adjusting the pH value, add an azo initiator and mix to obtain an aqueous phase. (2) Mix the emulsifier and the oil solvent to obtain the oil phase; (3) The aqueous phase obtained in step (1) is added to the oil phase obtained in step (2) and emulsified to obtain an emulsion; (4) First, add the oxidant to the emulsion obtained in step (3) and mix, then add the reducing agent, and after the reaction, the polymer microspheres are obtained.

9. The method for preparing polymer microspheres as described in claim 8, characterized in that... Step (1), Adjust the pH value with an alkaline solution; and / or, Adjust the pH value to between 5.8 and 6.2; and / or, Step (3), Mixing is carried out under stirring; and / or, Mixing is carried out under a continuous nitrogen purging; and / or, Step (4), An aqueous solution containing an oxidizing agent; and / or, After adding the oxidant, stir and mix for 1–10 minutes; and / or, An aqueous solution containing a reducing agent; the reducing agent is added dropwise; and / or, Stop adding reducing agent when the system temperature exceeds 50°C; and / or, The reaction temperature is 55–70℃; and / or, The reaction time is 1 to 2 hours.

10. The application of polymer microspheres as described in any one of claims 1 to 6 or polymer microspheres obtained by the preparation method as described in any one of claims 7 to 9 in oil and gas field development, preferably in oil and gas field development under reservoir conditions with temperatures greater than 90°C, and more preferably in oil and gas field development under reservoir conditions with temperatures greater than 110°C.

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