CN102304200B - Crosslinked polymer microspheres and preparation method thereof - Google Patents

Abstract

The invention provides a cross-linked polymer microsphere and a preparation method thereof. The preparation method comprises the following steps: under an inert atmosphere, the polymerization monomer is polymerized in an aqueous dispersion liquid in which a polymer dispersant, an inorganic salt and a cross-linking monomer are dissolved to obtain the cross-linked polymer microsphere. When the cross-linked polymer microspheres provided by the present invention are actually used, the aqueous dispersion containing the cross-linked polymer microspheres or the concentrated solution prepared by the cross-linked polymer microsphere powder can be directly used, and then passed through a high-pressure proportional pump. It is pumped into the water injection pipeline, mixed and diluted on-line on site, and then injected into the oil reservoir through the water injection well at a pre-designed mass percentage to achieve the purpose of improving the heterogeneity of the oil reservoir and increasing the oil recovery rate of the water injection development oil reservoir.

Description

A kind of cross-linked polymer microsphere and preparation method thereof

technical field

The invention relates to a cross-linked polymer microsphere capable of improving the heterogeneity of oil reservoirs and increasing the oil recovery rate of water injection development oil reservoirs and a preparation method thereof, belonging to the field of petroleum industry.

Background technique

At present, the early development of oil fields has gradually entered the middle and late stages of water flooding. How to further improve the volumetric sweep coefficient of injected water and the displacement efficiency within the water sweep volume, and economically and effectively exploit existing oil fields is a major issue to be solved urgently by the petroleum industry. One, in which the development and application of enhanced oil recovery technology has played an important role.

Enhanced oil recovery technology involves many aspects, and the methods based on improving the displacement effect can be divided into two categories: increasing the volumetric sweep coefficient of the injected fluid and improving the oil washing efficiency in the swept volume.

With the deepening of research, the influence of reservoir heterogeneity on the sweep coefficient of water flooding and chemical flooding fluid has attracted increasing attention in the industry. It is recognized that only through deep profile control can it be more economical and effective to adjust and improve The heterogeneity of the reservoir can be improved to improve the volumetric sweep coefficient of the injection fluid, ensure high displacement efficiency of the chemical flooding, and improve the oil recovery of the chemical flooding fluid and the subsequent water flooding stage. Among them, the deep profile control technology represented by cross-linked polymer flow gel, cross-linked polymer solution, and cross-linked polymer microspheres has economic advantages, obvious effects, long-term injection, and environmentally friendly technologies. The research and improvement of this method at a deeper level has very important significance for adjusting and improving the heterogeneity of reservoirs.

At present, the method for preparing cross-linked polymer coils for tertiary oil recovery is to use a linear partially hydrolyzed polyacrylamide (HPAM) dilute solution (mass fraction below its critical overlap mass fraction) to react with a cross-linking agent, Form an aqueous dispersion of cross-linked polymer coils (i.e., a cross-linked polymer solution); another method is to try to form a nano- or micro-scale aqueous dispersion, which contains cross-linking monomers. The copolymerization reaction of a variety of monomers forms polymer micelles, which swell and dissolve in water to form cross-linked polymer coils of different sizes. Theoretically speaking, only the use of cross-linked polymer coils whose particle size matches the formation pore size after injection can effectively retain and block throats, cause deep liquid flow to divert, and truly adjust and improve oil production. The heterogeneity of reservoirs can improve the recovery of crude oil in water flooding development.

Chinese patent ZL 200410006334.6 publicly reported in the preparation method of the water-soluble cross-linked polymer coil size is usually hundreds of nanometers, smaller particle size, Chinese patent ZL 200710063645. The size of the coils increases to several microns. The water-soluble cross-linked polymer coils prepared by the above two methods can meet the requirements of medium and low permeability reservoirs. The mine test has obtained a good effect of enhancing recovery . However, it is also found in the application of mines that for higher permeability reservoirs (permeability greater than 1000 mD), or medium and low permeability reservoirs with higher permeability bands, in order to obtain better plugging As a result, it is necessary to increase the mass fraction of water-soluble cross-linked polymer coils in the injection solution in the early stage of the test, which reduces the economy of the injection system. Therefore, research and search for a preparation method of large-scale water-soluble cross-linked polymer microspheres (coils) are useful for increasing and improving higher permeability reservoirs (permeability greater than 1000 mD), or there is a higher permeability The displacement effect of striped medium and low permeability reservoirs will have very practical value.

Contents of the invention

The object of the present invention is to provide a cross-linked polymer microsphere and a preparation method thereof.

The preparation method of the cross-linked polymer microspheres provided by the present invention comprises the following steps: under an inert atmosphere, the polymerized monomer is polymerized in an aqueous dispersion in which a polymer dispersant, an inorganic salt and a cross-linked monomer are dissolved to obtain The cross-linked polymer microspheres.

In the above preparation method, the mass percentages of the polymer dispersant, inorganic salt and crosslinking monomer in the aqueous dispersion are 1.0% to 10.0%, 10.0% to 40.0% and 0.001% to 3.0% respectively ; The mass percentage of the polymerized monomer in the aqueous dispersion is 1.0%-40.0%.

In the above preparation method, the mass percentage of the polymer dispersant in the aqueous dispersion can specifically be 4.3%, 5.82% or 6.82%; the mass percentage of the inorganic salt in the aqueous dispersion can specifically be 18% or 195%; the mass percentage of the crosslinking monomer in the aqueous dispersion can be specifically 0.45% or 0.46%; the mass percentage of the polymerized monomer in the aqueous dispersion can be specifically 5.68% % or 5.7%.

In the above preparation method, the polymerized monomer can be a monomer molecule containing only a single double bond and a water-soluble group in the molecular structure; including nonionic monomers, such as: acrylamide, methacrylamide, N-ethylene Nyl formamide, N-vinylacetamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, (meth)acrylate-2-hydroxyethyl acrylamide or Allyl alcohol, etc.; anionic monomers, such as (meth)acrylic acid, itaconic acid, maleic acid, 2-acrylamide-2-methylpropanesulfonic acid or vinylsulfonic acid, etc. For example: (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyldiethylmethylammonium chloride, (meth)acryloyloxyethyldimethyl Benzyl ammonium chloride, (meth)acryloyloxyethyldiethyl benzyl ammonium chloride, dimethyl diallyl ammonium chloride, or the like.

In the above preparation method, the inorganic salt can be at least one of ammonium sulfate, sodium sulfate, potassium sulfate, ammonium chloride, potassium chloride and sodium chloride.

In the above preparation method, the crosslinking monomer can be a multifunctional monomer containing two or more double bonds in the molecular structure, and the distance between the double bonds can be adjusted by adjusting the length of the group connecting the double bonds. For example: bifunctional monomers can be N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, polyethylene glycol diallyl ether, N,N-diallyl dimethyl chloride Ammonium chloride, N,N'-diallyl-N,N,N',N'-tetramethylhexammonium chloride or N,N'-di-p-vinylbenzyl-N,N,N' , N'-tetramethylhexamethylenedichloride, etc.; the trifunctional monomer can be triacrylic acid-(propyl)trimethyl ester or pentaerythritol triallyl ether, etc.

In the above-mentioned preparation method, the polymer dispersant can be selected from commercially available polymer dispersants, such as commercially available: polyvinyl alcohol with a relative molecular mass of 4000-20000, polyethylene glycol with a relative molecular mass of 5000-30000 Amines, homopolymers or copolymers of vinylpyrrolidone, etc., wherein the homopolymer or copolymer of vinylpyrrolidone is better; Obtained by dilute solution polymerization of polymerized monomers, such as anionic crosslinked polymer microspheres containing acrylamide-sodium acrylate-2-acrylamide-2-methylpropanesulfonate structure in the synthetic molecular structure, the polymer dispersant It can be used as a homopolymer obtained by dilute solution polymerization of 2-acrylamide-2-methylpropanesulfonate sodium; another example is that the synthetic molecular structure contains acrylamide-acryloyloxyethyltrimethylammonium chloride-2-propene Zwitterionic cross-linked polymer microspheres with amide-2-methylpropanesulfonate sodium structure or cationic cross-linked polymer microspheres with acrylamide-acryloyloxyethyltrimethylammonium chloride structure in molecular structure, so The above-mentioned polymer dispersant can be used as a homopolymer obtained by dilute solution polymerization of acryloyloxyethyltrimethylammonium chloride.

In the above preparation method, the dispersion liquid may further include at least one of an oxidative initiator, a water-soluble thermal decomposition initiator, a chelating agent, a pH regulator and a co-solvent.

In the above-mentioned preparation method, the oxidizing initiator can be ammonium persulfate, and the oxidizing initiator can be alone or carry out oxidation-reduction reaction with a reducing gas to form a free radical to initiate a polymerization reaction, and the reducing gas It is preferably sulfur dioxide, and the addition amount of the oxidizing initiator can account for 0.0001%-0.0005% of the mass percentage of the aqueous dispersion, such as 0.00025% or 0.0003%; the water-soluble thermal decomposition initiator can be 2 , 2'-Azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-Azobis(2-amidino propane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane) dihydrochloride or 2,2'-azobis[2-(5-methyl base-2-imidazolin-2-yl) propane) dihydrochloride, the water-soluble thermal decomposition initiator is used to trigger the remaining polymerized monomers in the later stage of polymerization, and reduces the water dispersion of the cross-linked polymer microspheres The residual polymerized monomer content in the liquid, the addition of the water-soluble thermal decomposition initiator can account for 0.0001%-0.0008% of the mass percentage of the water dispersion, such as 0.0005% or 0.00075%; the chelating agent It is disodium ethylenediamine tetraacetate, which is used to slow down and eliminate the influence of heavy metal ions in the polymer monomer on the polymerization reaction. The amount of the chelating agent added can be 0.0001%- 0.0005%, such as 0.0005%; the pH adjuster is sodium hydroxide, sodium carbonate or sodium bicarbonate, which is used to adjust the pH value of the water dispersion to ensure the suitable acidity and alkalinity of the water dispersion; the cosolvent can be It is urea, so that the components in the water phase can be fully dissolved in water, and the addition amount of the co-solvent can be 0.001%-0.005%, such as 0.001%, in the mass percentage of the aqueous dispersion.

In the above preparation method, the method further includes the steps of precipitating, refining and drying the cross-linked polymer microspheres.

In the above preparation method, the temperature of the polymerization reaction may be 5°C-85°C, such as 35°C or 50°C; the time of the polymerization reaction may be 4 hours-12 hours, such as 10 hours.

The cross-linked polymer microspheres prepared by the above method of the present invention have a particle size of 3 μm-50 μm, such as 9.6 μm, 14.5 μm or 15.6 μm.

When the cross-linked polymer microspheres provided by the present invention are actually used, the aqueous dispersion containing the cross-linked polymer microspheres or the concentrated solution prepared by the cross-linked polymer microsphere powder can be directly used, and then passed through a high-pressure proportional pump. It is pumped into the water injection pipeline, mixed and diluted on-line on site, and then injected into the oil reservoir through the water injection well at a pre-designed mass percentage to achieve the purpose of improving the heterogeneity of the oil reservoir and increasing the oil recovery rate of the water injection development oil reservoir. When the cross-linked polymer microspheres of the present invention are used as a profile control agent suitable for improving reservoir heterogeneity and increasing oil recovery in water injection development reservoirs, the mass percentage is usually 0.1 to 3.0% of the injected water quality. It is effective within the range of ‰, and the effect is better when the mass percentage is 0.2-1.5 ‰ of the injected water quality, and the best effect is when the mass percentage is 0.4-0.8 ‰ of the injected water quality. Of course, for reservoirs with different geological conditions and different development stages, the actual use mass fraction and injection method should be determined through preliminary laboratory experiments and numerical simulations.

In the profile control treatment of oil reservoirs, the cross-linked polymer microspheres provided by the present invention have higher permeability (permeability greater than 1000 mD), or medium and low permeability with higher permeability bands The mechanical retention and plugging of larger throats in the reservoir can cause deep liquid flow to change direction, which can adjust and improve the heterogeneity of the reservoir, and block the dominant water channel formed by long-term water injection in the deep reservoir. The aqueous solution system of cross-linked polymer microspheres provided by the present invention is particularly suitable for higher permeability reservoirs (permeability greater than 1000 mD), or the application of medium and low permeability reservoirs with higher permeability bands, Improve the recovery rate of crude oil in the middle and late stages of water flooding development.

Detailed ways

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

Using a determined volume of cross-linked polymer microsphere aqueous solution to plug profile control performance and oil displacement efficiency of artificial core with a gas permeability of 2.0 ^μm2 , to simulate the plugging of reservoir formation pores by cross-linked polymer microsphere aqueous solution To evaluate the plugging profile control performance of cross-linked polymer microsphere aqueous solution.

Embodiment 1, the preparation of cross-linked polymer microspheres

Add 1.50 grams of polyvinylpyrrolidone (K-60), 16.50 grams of ammonium sulfate, 1.50 grams of sodium chloride, and 5.68 grams of acrylamide (AM) in a jacketed reactor equipped with a gas inlet pipe, a thermometer, and a constant speed stirrer , sodium acrylate 1.02 g, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) 3.30 g, N,N'-diallyl-N,N,N',N'-tetramethylhexanedichloride 0.45 g of ammonium chloride, 0.50 mg of disodium edetate as a chelating agent, and 1.0 mg of cosolvent urea, all the above ingredients were dissolved in 68.00 g of ultrapure water (conductivity ≤ 4 μS/cm), and mixed with 35% sodium hydroxide Adjust the pH value of the solution to 7.5-8.5; in the above water dispersion, the mass percentage of ammonium sulfate and sodium chloride is 18.0%; the mass percentage of acrylamide is 5.68%; polyvinylpyrrolidone, sodium acrylate and 2- The mass percent of acrylamide-2-methylpropanesulfonic acid is 5.82%; the mass percent of N,N'-diallyl-N,N,N',N'-tetramethylhexammonium chloride The content of urea is 0.45%; the mass percentage of disodium edetate is 0.0005%; the mass percentage of urea is 0.001%.

Set 35°C as the initiation temperature, first pass inert gas high-purity nitrogen into the above-mentioned saline dispersion to drive oxygen, reduce the oxygen content in the system (≤0.3μg/g) to facilitate the polymerization reaction, and add 0.30 mg of ammonium persulfate ( Accounting for the mass percent of the aqueous dispersion is 0.0003%), 0.50 mg of 2,2'-azobis(2-amidinopropane) dihydrochloride (accounting for the mass percent of the aqueous dispersion is 0.0005%), Then pass through reducing gas sulfur dioxide and ammonium persulfate in the water phase to form an oxidation-reduction initiation system, and the polymerization reaction is carried out for 4 hours, and then the temperature is raised to 50 ° C and continued for 6 hours to obtain water of cross-linked polymer microspheres. The dispersion has a viscosity of 848mPa.s at 25°C and a median particle size distribution of 14.5μm.

Take out part of the aqueous dispersion containing cross-linked polymer microspheres prepared above and dissolve it in water, add absolute ethanol as a precipitant to the aqueous solution, and precipitate cross-linked polymer microspheres with a particle size of 14.5 μm, pass through petroleum ether Extract and dry to make cross-linked polymer microsphere powder.

The above-mentioned cross-linked polymer microspheres with a mass fraction of 400 mg/kg were matured in the simulated water of Bohai SZ36-1 oil field at 60 °C for ⁹⁶ hours to obtain an aqueous solution of cross-linked polymer coils. The displacement experiment of simulated oil in SZ36-1 oilfield shows that the simulated oil recovery can be increased by 20.6% under the experimental conditions.

Embodiment 2, the preparation of cross-linked polymer microspheres

Add 2.50 grams of polyvinylpyrrolidone (K-17), 17.50 grams of ammonium sulfate, 1.50 grams of sodium chloride, and 5.68 grams of acrylamide (AM) in a jacketed reactor equipped with a gas inlet pipe, a thermometer, and a constant speed stirrer , sodium acrylate 1.02 g, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) 3.30 g, N,N'-diallyl-N,N,N',N'-tetramethylhexanedichloride 0.45 grams of ammonium chloride, 0.50 milligrams of disodium edetate as a chelating agent, and 1.0 milligrams of urea. The above ingredients were dissolved in 66.00 grams of ultrapure water (conductivity ≤ 4 μS/cm), and the solution was adjusted with 35% sodium hydroxide The pH is 7.5-8.5. In the above aqueous dispersion, the mass percentage of ammonium sulfate and sodium chloride is 19.0%; the mass percentage of acrylamide is 5.68%; polyvinylpyrrolidone, sodium acrylate and 2-acrylamide-2-methylpropanesulfonate The mass percentage of acid is 6.82%; the mass percentage of N, N'-diallyl-N, N, N', N'-tetramethylhexammonium chloride is 0.45%; ethylenediamine The mass percentage content of disodium tetraacetate is 0.0005%; the mass percentage content of urea is 0.001%.

Set 35°C as the initiation temperature, first pass inert gas high-purity nitrogen into the above-mentioned saline dispersion to drive oxygen, reduce the oxygen content in the system (≤0.3μg/g) to facilitate the polymerization reaction, and add 0.30 mg of ammonium persulfate ( Accounting for the mass percent of the aqueous dispersion is 0.0003%), 0.50 mg of 2,2'-azobis(2-amidinopropane) dihydrochloride (accounting for the mass percent of the aqueous dispersion is 0.0005%), Then, the reducing gas sulfur dioxide and ammonium persulfate in the water phase are introduced to form an oxidation-reduction initiation system, and the polymerization reaction is carried out for 4 hours, and then the temperature is raised to 50°C for 6 hours to obtain large-sized cross-linked polymer microspheres The viscosity of the aqueous dispersion is 640mPa.s at 25°C, and the median particle size distribution is 9.6μm.

Take out part of the aqueous dispersion containing cross-linked polymer microspheres prepared above and dissolve it in water, add absolute ethanol as a precipitant to the aqueous solution, and precipitate cross-linked polymer microspheres with a particle size of 9.6 μm. Extract and dry to make large-size cross-linked polymer microsphere powder.

The above-mentioned large-sized cross-linked polymer microspheres with a mass fraction of 400mg/kg were matured in the simulated water of Bohai SZ36-1 oilfield at 60°C for 96 hours to obtain ^an aqueous solution of cross-linked polymer coils. The displacement experiment of simulated oil in Bohai SZ36-1 oilfield was carried out, and it was measured that the simulated oil recovery could be increased by 18.2% under the experimental conditions.

Embodiment 3, the preparation of cross-linked polymer microsphere

The crosslinked polymer microsphere aqueous solution powder was prepared according to the same method as in Example 1.

The above-prepared cross-linked polymer microspheres with a mass fraction of 400mg/kg were matured for 96 hours in the simulated water of Bohai SZ36-1 oilfield at 60°C to obtain ^an aqueous solution of cross-linked polymer coils. The displacement experiment of simulated oil in Bohai SZ36-1 oilfield was carried out, and it was measured that the simulated oil recovery could be increased by 18.6% under the experimental conditions.

Embodiment 4, the preparation of cross-linked polymer microspheres

Add 1.42 g of acrylamide (AM), 6.40 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and ultrapure water into a jacketed reactor equipped with a gas inlet tube, a thermometer, and a constant-speed stirrer. (Conductivity≤4μS/cm) 42 grams, nitrogen gas 30 minutes, add ammonium persulfate 0.46 mg, sodium bisulfite 0.26 mg, trigger temperature 35 ℃, react for 4 hours to obtain AM-AMPS copolymer solution as a dispersant.

Continue to add 43.80 grams of ammonium sulfate, 3.80 grams of sodium chloride, 14.20 grams of acrylamide (AM), 2.55 grams of sodium acrylate, 8.30 grams of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) in the reactor, N, N'-diallyl-N, N, N', N'-tetramethylhexammonium chloride 1.15 grams, chelating agent edetate disodium 1.25 mg, urea 2.5 mg, ultrapure water (conductivity rate≤4μS/cm) 120.00 grams, and with 35% sodium hydroxide to adjust the pH value of the solution to 7.5-8.5, in the above water dispersion, the mass percentage of ammonium sulfate and sodium chloride is 19.0%; the mass percentage of acrylamide The content is 5.7%; the mass percentage content of sodium acrylate and 2-acrylamide-2-methylpropanesulfonic acid is 4.3%; N, N'-diallyl-N, N, N', N'- The mass percentage of tetramethylhexammonium chloride is 0.46%, the mass percentage of disodium edetate is 0.0005%, and the mass percentage of urea is 0.001%.

Set 35°C as the initiation temperature, first pass inert gas high-purity nitrogen into the above-mentioned saline dispersion to drive oxygen, reduce the oxygen content in the system (≤0.3μg/g) to facilitate the polymerization reaction to be initiated, add 0.25 mg of ammonium persulfate ( Accounting for the mass percentage of the aqueous dispersion is 0.00025%), 0.75 mg of 2,2'-azobis(2-amidinopropane) dihydrochloride (accounting for the mass percentage of the aqueous dispersion is 0.00075%), Then, the reducing gas sulfur dioxide and ammonium persulfate in the water phase are introduced to form an oxidation-reduction initiation system, and the polymerization reaction is carried out for 4 hours, and then the temperature is raised to 50°C for 6 hours to obtain large-sized cross-linked polymer microspheres The viscosity of the aqueous dispersion is 940mPa.s at 25°C, and the median particle size distribution is 15.6μm.

Take out part of the aqueous dispersion containing cross-linked polymer microspheres prepared above and dissolve in water, add absolute ethanol as a precipitating agent to the aqueous solution, and precipitate cross-linked polymer microspheres with a particle size of 15.6 μm, pass through petroleum ether Extract and dry to make large-size cross-linked polymer microsphere powder.

The above-mentioned cross-linked polymer microspheres with a mass fraction of 400 mg/kg were matured for 96 hours in the simulated water of Bohai SZ36-1 oilfield at 60°C to obtain ^an aqueous solution of cross-linked polymer coils. The displacement experiment of simulated oil in SZ36-1 oil field shows that the simulated oil recovery can be increased by 19.5% under the experimental conditions.

Comparative example 1, the preparation of cross-linked polymer coils

According to Example 5 in the preparation method disclosed in the Chinese patent ZL 200710063645.X, a W/O type dispersion containing crosslinked polymer coils with a bimodal distribution of particle diameters was prepared;

Take a small amount of the above-mentioned W/O dispersion containing cross-linked polymer coils with bimodal particle size distribution, add absolute ethanol as a precipitant to precipitate cross-linked polymer coils with bimodal particle size distribution, and pass through petroleum Ether extraction, drying to produce cross-linked polymer coil powder with bimodal particle size distribution.

The cross-linked polymer coils with a mass fraction of 400 mg/kg were matured in the simulated water of Bohai SZ36-1 oilfield at 60°C for ⁹⁶ hours to obtain an aqueous solution of cross-linked polymer coils. The displacement experiment of simulated oil in the -1 oilfield shows that the simulated oil recovery can be increased by 15.0% under the experimental conditions. The experimental results are shown in Table 1.

The results of each embodiment and comparative example are comprehensively listed in Table 1.

Table 1, comparative example and the comparison of the enhanced oil recovery of each embodiment

Comparing Examples 1 and 3, it can be seen that the cross-linked polymer microspheres prepared by the present invention have different plugging and profile control effects on rock cores with different permeability, which means that the size of the cross-linked polymer microspheres of the present invention is different from that of the rock cores. The channel matching problem needs to be achieved by adjusting the amount of polymer dispersant, inorganic salt and/or mass fraction of cross-linked polymer coils during polymerization.

Comparing Examples 1, 2 and 4, it can be seen that the enhanced oil recovery capability of the cross-linked polymer microspheres prepared by the present invention can be adjusted by adjusting the molecular structure and preparation method.

The above examples and comparative results only suggest the effect that the preparation method of the present invention can achieve, that is, different large-sized cross-linked polymer microspheres can be prepared adaptively according to the reservoir characteristics and recovery degree.

On the other hand, comparing Comparative Example 1 with the four specific examples, it can be seen that the aqueous solution of the profile control agent for plugging and profile control obtained under the conditions of the same mass fraction, the same salinity, the same temperature, and the same aging time , when carrying out oil displacement experiments on rock cores with the same gas permeability, the cross-linked polymer microsphere aqueous solution obtained by this method can better improve the recovery of simulated oil, indicating that the cross-linked polymer obtained by this method The microsphere aqueous solution has the same or better plugging ability than the smaller cross-linked polymer coil solution obtained by the emulsion polymerization method for porous media with higher permeability.

Claims (6)

1. A preparation method for cross-linked polymer microspheres, comprising the steps of: under an inert atmosphere, the polymerization monomer is polymerized in an aqueous dispersion that is dissolved with a polymer dispersant, an inorganic salt and a cross-linking monomer to obtain The cross-linked polymer microspheres; The mass percentages of the polymer dispersant, inorganic salt and crosslinking monomer in the aqueous dispersion are 1.0% to 10.0%, 10.0% to 40.0% and 0.001% to 3.0% respectively; The mass percentage of the aqueous dispersion is 1.0% to 40.0%; The polymerizable monomer is acrylamide, methacrylamide or N,N-dimethylacrylamide; The inorganic salt is at least one of ammonium sulfate, sodium sulfate, potassium sulfate, ammonium chloride, potassium chloride and sodium chloride; The crosslinking monomer is N,N'-diallyl-N,N,N',N'-tetramethylhexammonium chloride or N,N'-di-p-vinylbenzyl-N, N,N',N'-Tetramethylhexamethylene dichloride; The polymer dispersant is vinylpyrrolidone homopolymer, vinylpyrrolidone copolymer or 2-acrylamide-2-methylpropanesulfonate sodium homopolymer. 2. The preparation method according to claim 1, characterized in that: the dispersion also includes at least one of an oxidizing initiator, a water-soluble thermal decomposition initiator, a chelating agent, a pH regulator and a cosolvent. 3. The preparation method according to claim 2, characterized in that: the oxidizing initiator is ammonium persulfate; the water-soluble thermal decomposition initiator is 2,2'-azobis{2-[1- (2-Hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'- Azobis[2-(2-imidazolin-2-yl)propane) dihydrochloride or 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane) dihydrochloride; the chelating agent is disodium edetate; the pH regulator is sodium hydroxide, sodium carbonate or sodium bicarbonate; the cosolvent is urea. 4. The preparation method according to claim 1 or 2, characterized in that: the method further comprises the steps of precipitating, refining and drying the cross-linked polymer microspheres. 5. The cross-linked polymer microsphere prepared by the method according to any one of claims 1-4; the particle diameter of the cross-linked polymer microsphere is 3 μm-50 μm. 6. the crosslinked polymer microsphere described in claim 5 is as the application of oil displacement agent.