Polymer microspheres, preparation method thereof, composite profile control agent and water shutoff and profile control method

Abstract

The invention discloses polymer microspheres and a preparation method thereof, a composite profile control agent and a water shutoff and profile control method, and belongs to the technical field of oil production engineering. The polymer microsphere comprises an inner core and a shell, the inner core is obtained by reacting a first monomer composition with a first cross-linking agent, the first monomer composition comprises at least one of acrylamide, acrylic acid, N-vinyl pyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate, and the first cross-linking agent is at least one of N, N '-methylene bisacrylamide and tetraallyl ammonium chloride; the shell is obtained by reacting a second monomer composition with a second cross-linking agent, the second monomer composition comprises acrylamide, acrylic acid, methyl methacrylate and / or butyl acrylate, and the second cross-linking agent is at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate and polypropylene glycol diacrylate. The profile control agent formed by the polymer microspheres and the phenolic resin cross-linking agent has excellent temperature resistance and salt tolerance.

Description

Technical Field

[0001] This invention relates to the field of oilfield engineering technology, and in particular to polymer microspheres and their preparation methods, composite profile control agents, and water shut-off and profile control methods. Background Technology

[0002] Polymer microspheres are polymerized from resin monomers using a pre-crosslinking method. This overcomes the uncontrollable gel strength issues caused by the surface-based preparation and underground crosslinking of gel-type plugging agents. Furthermore, the production process can utilize online injection, minimizing restrictions on well site conditions. The injection process is simple, convenient, and widely applicable. During application, the polymer microspheres hydrate and expand, accumulating and bridging within the formation to seal formation pores. Due to their small initial particle size (typically nanometer to micrometer scale) and sub-millimeter scale after expansion, they possess excellent deep-seated transport capabilities, enabling waterflow control in deep oil reservoirs.

[0003] To improve the temperature and salt resistance of polymer microspheres, related technologies typically utilize inorganic nanoparticles such as silica to modify the polymer microspheres. However, this approach has limited effectiveness in improving the temperature and salt resistance of profile control agents and suffers from drawbacks such as complex preparation processes and low product yield.

[0004] Therefore, it is essential to provide a profile control agent with excellent temperature and salt resistance. Summary of the Invention

[0005] In view of this, the present invention provides a polymer microsphere and its preparation method, a composite profile control agent, and a water-blocking profile control method, which can solve the technical problems existing in related technologies.

[0006] Specifically, the following technical solutions are included:

[0007] A polymer microsphere comprising a core and a shell covering the core;

[0008] The core is prepared by a crosslinking reaction of a first monomer composition and a first crosslinking agent. The first monomer composition includes acrylamide, acrylic acid, and at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate. The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide and tetraallyl ammonium chloride.

[0009] The outer shell is prepared by a crosslinking reaction of a second monomer composition and a second crosslinking agent. The second monomer composition includes at least one of acrylamide, acrylic acid, methyl methacrylate, and butyl acrylate. The second crosslinking agent is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol diacrylate.

[0010] In some possible implementations, the mass ratio of the first monomer composition to the first crosslinking agent is 4 to 45:1;

[0011] In the first monomer composition, the acrylamide is 50%-70% by mass, the acrylic acid is 10%-30% by mass, and at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate is 2%-10% by mass.

[0012] In some possible implementations, the mass ratio of the second monomer composition to the second crosslinking agent is 10 to 80:1;

[0013] In the second monomer composition, the acrylamide is 50%-70% by mass, the acrylic acid is 10%-30% by mass, and at least one of methyl methacrylate and butyl acrylate is 2%-10% by mass.

[0014] In some possible implementations, the core has a particle size in the nanometer range, and the outer shell has a particle size in the micrometer range.

[0015] On the other hand, a method for preparing polymer microspheres is provided, wherein the polymer microspheres are as described in any of the above descriptions;

[0016] The preparation method of the polymer microspheres is as follows:

[0017] A first aqueous solution is prepared using a first monomer composition, a first crosslinking agent, and water; a second aqueous solution is prepared using a second monomer composition, a second crosslinking agent, and water; a third aqueous solution is prepared by dispersing an initiator in water; and an oil phase solution is prepared by dispersing an emulsifier in solvent oil.

[0018] A portion of the first aqueous phase solution and a portion of the third aqueous phase solution are added to the oil phase solution, and the reaction is carried out for a first set time.

[0019] The remaining first aqueous solution, second aqueous solution, and remaining third aqueous solution are added to the reaction system, and the reaction is continued for a second set time to prepare the polymer microspheres.

[0020] In some possible implementations, adding a portion of the first aqueous phase solution and a portion of the third aqueous phase solution to the oil phase solution, and reacting for a first predetermined time, includes:

[0021] Add a portion of the first aqueous phase solution to the oil phase solution, stir for 20-60 minutes, introduce nitrogen gas, heat to 40°C-60°C, then add a portion of the third aqueous phase solution to the oil phase solution, and react for 30-60 minutes.

[0022] In some possible implementations, the step of continuing to add the remaining first aqueous phase solution, the second aqueous phase solution, and the remaining third aqueous phase solution to the reaction system, and continuing the reaction for a second predetermined time to prepare the polymer microspheres includes:

[0023] The remaining first aqueous phase solution and second aqueous phase solution are added to the reaction system. After reacting for 10-20 minutes, the remaining third aqueous phase solution is added to the reaction system. After reacting for 3-6 hours, the mixture is cooled and discharged to obtain the polymer microspheres.

[0024] In some possible implementations, the first monomer composition accounts for 20%-45% of the mass percentage of the first aqueous phase solution, and the first crosslinking agent accounts for 1%-5% of the mass percentage of the first aqueous phase solution;

[0025] The second monomer composition accounts for 20%-45% of the mass percentage of the second aqueous solution, and the second crosslinking agent accounts for 0.5%-2% of the mass percentage of the second aqueous solution.

[0026] In another aspect, a composite profile control agent is provided, the composite profile control agent comprising any of the polymer microspheres, phenolic resin crosslinking agent and water described above;

[0027] The concentration of the polymer microspheres is 1000 mg / L-5000 mg / L;

[0028] The mass concentration of the phenolic resin crosslinking agent is 500 mg / L-4000 mg / L.

[0029] On the other hand, a water-blocking and profile control method is provided, wherein the water-blocking and profile control method uses the above-mentioned composite profile control agent.

[0030] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0031] The polymer microspheres provided in this invention employ a core-shell structure. The core portion is formed by the cross-linking reaction of a stable first cross-linking agent with a first monomer composition to form a dense three-dimensional network structure, while the outer shell portion is formed by the cross-linking reaction of an unstable second cross-linking agent with a second monomer composition to form a looser three-dimensional network structure. Based on the composition of its core and shell, the polymer microspheres remain stable at room temperature and do not exhibit reactivity. In application, the polymer microspheres can combine with a phenolic resin cross-linking agent to form a composite profile control agent and react in the formation environment. Specifically, the unstable second cross-linking agent in the outer shell of the polymer microspheres gradually decomposes, releasing the long-chain polymer structure and exposing reactive groups. These reactive groups can cross-link with the phenolic resin cross-linking agent to form a large-volume network aggregate, effectively sealing large pores in the formation. Simultaneously, this network aggregate exhibits viscoelasticity, allowing it to deform under pressure and pass through pores, achieving a migration-blocking-breakthrough-re-migration effect. The composite profile control agent formed by the polymer microspheres and phenolic resin crosslinking agent has excellent temperature and salt resistance. Studies have shown that the agglomerate formation time is 5h-20d under the temperature conditions of 70℃-130℃, the salinity of the water used for preparation can reach up to 100000mg / L, the agglomerate performance is stable, and the high temperature aging time is >180d. The results of physical model experiments and field applications show that the composite profile control agent can achieve deep migration and ensure its sealing effect in high temperature and high salt environment. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The production relationship curve of the polymer microsphere-based composite profile control agent provided in Example 5 applied to a well group.

[0034] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise defined, all technical terms used in the embodiments of this invention have the same meaning as commonly understood by one of ordinary skill in the art. In the embodiments of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "a plurality of" refers to two or more, unless otherwise expressly defined.

[0037] On one hand, embodiments of the present invention provide a polymer microsphere comprising a core and a shell covering the core. The core is prepared by a crosslinking reaction of a first monomer composition and a first crosslinking agent. The first monomer composition comprises at least one of acrylamide, acrylic acid, and N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate. The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide and tetraallyl ammonium chloride. The shell is prepared by a crosslinking reaction of a second monomer composition and a second crosslinking agent. The second monomer composition comprises at least one of acrylamide, acrylic acid, and methyl methacrylate and butyl acrylate. The second crosslinking agent is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol diacrylate.

[0038] The polymer microspheres provided in this invention employ a core-shell structure. The core portion is formed by the cross-linking reaction of a stable first cross-linking agent with a first monomer composition to form a dense three-dimensional network structure, while the outer shell portion is formed by the cross-linking reaction of an unstable second cross-linking agent with a second monomer composition to form a looser three-dimensional network structure. Based on the composition of its core and shell, the polymer microspheres remain stable at room temperature and do not exhibit reactivity. In application, the polymer microspheres can combine with a phenolic resin cross-linking agent to form a composite profile control agent and react in the formation environment. Specifically, the unstable second cross-linking agent in the outer shell of the polymer microspheres gradually decomposes, releasing the long-chain polymer structure and exposing reactive groups. These reactive groups can cross-link with the phenolic resin cross-linking agent to form a large-volume network aggregate, effectively sealing large pores in the formation. Simultaneously, this network aggregate exhibits viscoelasticity, allowing it to deform under pressure and pass through pores, achieving a migration-blocking-breakthrough-re-migration effect. The composite profile control agent formed by the polymer microspheres and phenolic resin crosslinking agent has excellent temperature and salt resistance. Studies have shown that the agglomerate formation time is 5h-20d under the temperature conditions of 70℃-130℃, the salinity of the water used for preparation can reach up to 100000mg / L, the agglomerate performance is stable, and the high temperature aging time is >180d. The results of physical model experiments and field applications show that the composite profile control agent can achieve deep migration and ensure its sealing effect in high temperature and high salt environment.

[0039] In the polymer microspheres, the first monomer composition includes acrylamide, acrylic acid, and at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate. That is, in addition to acrylamide and acrylic acid, it may also include at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate. The first crosslinking agent is selected from N,N'-methylenebisacrylamide or tetraallyl ammonium chloride, and may also be selected from a mixture of N,N'-methylenebisacrylamide and tetraallyl ammonium chloride.

[0040] In this embodiment of the invention, the mass ratio of the first monomer composition to the first crosslinking agent is 4 to 45:1, and may further be 5 to 40:1, 10 to 30:1, 10 to 20:1, 10 to 35:1, etc.

[0041] In the first monomer composition, the mass percentage of acrylamide is 50%-70%, including but not limited to: 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, etc. The mass percentage of acrylic acid is 10%-30%, including but not limited to: 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc. The mass percentage of at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate is 2%-10%, including but not limited to: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0042] When the proportions of the components in the core of the polymer microspheres are within the above-mentioned range, it is more beneficial to optimize the stable core structure of the polymer microspheres and to improve the profile control effect of the polymer microspheres.

[0043] In the polymer microspheres, the second monomer composition includes at least one of acrylamide, acrylic acid, and methyl methacrylate and butyl acrylate; that is, in addition to acrylamide and acrylic acid, it may also include at least one of methyl methacrylate and butyl acrylate. The second crosslinking agent is selected from any one, any two, or any three of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol diacrylate.

[0044] In this embodiment of the invention, the mass ratio of the second monomer composition to the second crosslinking agent is 10-80:1, and may further be 10-70:1, 10-60:1, 10-50:1, 10-40:1, 10-30:1, 10-20:1, etc.

[0045] In the second monomer composition, the mass percentage of acrylamide is 50%-70%, including but not limited to: 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, etc. The mass percentage of acrylic acid is 10%-30%, including but not limited to: 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc. The mass percentage of at least one of methyl methacrylate and butyl acrylate is 2%-10%, including but not limited to: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0046] When the proportions of the components in the outer shell of the polymer microspheres are within the above-mentioned range, it is more beneficial to optimize the unstable outer shell structure of the polymer microspheres and to improve the profile control effect of the polymer microspheres.

[0047] In some examples, the polymer microspheres provided in the embodiments of the present invention have a core particle size of nanometers and a shell particle size of micrometers, resulting in a small size that facilitates storage. Furthermore, after the polymer microspheres undergo a cross-linking reaction with a phenolic resin cross-linking agent to form aggregates, the aggregates have macroscopic millimeter-centimeter dimensions, enabling effective sealing of large pores in the formation.

[0048] In some examples, the polymer microspheres provided in the embodiments of the present invention exist in the form of microsphere emulsions, that is, the polymer microspheres exist in the oil phase solution, and the aqueous solvent in the product system can be removed after the reaction is completed.

[0049] On the other hand, embodiments of the present invention also provide a method for preparing polymer microspheres, wherein the polymer microspheres are as described in any of the above descriptions. The method for preparing the polymer microspheres includes the following steps:

[0050] Step 1: Prepare a first aqueous solution using a first monomer composition, a first crosslinking agent, and water; prepare a second aqueous solution using a second monomer composition, a second crosslinking agent, and water; prepare a third aqueous solution by dispersing an initiator in water; and prepare an oil phase solution by dispersing an emulsifier in solvent oil.

[0051] Step 2: Add part of the first aqueous phase solution and part of the third aqueous phase solution to the oil phase solution, and react for a set time.

[0052] Step 3: Continue to add the remaining first aqueous phase solution, second aqueous phase solution, and remaining third aqueous phase solution to the reaction system, and continue the reaction for a second set time to prepare polymer microspheres.

[0053] Step 1 prepares the reaction raw material solutions for the reaction. Step 2 initially forms a partial core of the polymer microspheres. Step 3 further forms the remaining core based on the formed partial core, and then coats the formed core to form a shell. Thus, based on the polymer microsphere preparation method of the embodiments of the present invention, an emulsion of polymer microspheres with the desired structure is obtained, or individual polymer microspheres are further separated.

[0054] For step 1, the preparation of a first aqueous solution using a first monomer composition, a first crosslinking agent and water includes: dissolving the first monomer composition and the first crosslinking agent in water, stirring evenly and adjusting the pH value to neutral to weakly alkaline to obtain the first aqueous solution.

[0055] A second aqueous solution is prepared using a second monomer composition, a second crosslinking agent, and water, comprising: dissolving the second monomer composition and the second crosslinking agent in water, stirring until homogeneous, and adjusting the pH value to neutral to weakly alkaline to obtain the second aqueous solution.

[0056] The initiator is dissolved and dispersed in water, and the mixture is stirred until homogeneous to prepare the third aqueous phase solution. Potassium persulfate can be used as the initiator to promote the crosslinking reaction. The mass percentage of potassium persulfate is 0.05%-0.2% of the total mass of the first and second monomer compositions.

[0057] An emulsifier is dispersed in a solvent oil to prepare an oil-phase solution. Some suitable solvent oils may be white oil or paraffin oil. Exemplarily, the volume of the oil-phase solution is 60%-80% of the total volume of the first aqueous phase solution, the second aqueous phase solution, the third aqueous phase solution, and the oil-phase solution. The emulsifier is at least one from the TWEEN series or the SPAN series, and the mass concentration of the emulsifier is 5%-15% of the total mass of the first aqueous phase solution, the second aqueous phase solution, the third aqueous phase solution, and the oil-phase solution.

[0058] The first monomer composition comprises 20%-45% of the first aqueous phase solution by mass, including but not limited to: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, etc. The first crosslinking agent comprises 1%-5% of the first aqueous phase solution by mass, including but not limited to: 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. Furthermore, the mass percentages of each monomer in the first monomer composition are described above in the polymer microsphere formulation and will not be repeated here.

[0059] The second monomer composition accounts for 20%-45% of the mass percentage of the second aqueous phase solution, including but not limited to: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, etc. The second crosslinking agent accounts for 0.5%-2% of the mass percentage of the second aqueous phase solution, including but not limited to: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc. In addition, the mass percentage of each monomer in the second monomer composition can be found in the relevant description in the polymer microsphere scheme above, and will not be repeated here.

[0060] The mass percentage of potassium persulfate is 0.05%-0.2% of the total mass of monomers in the first and second aqueous phase solutions.

[0061] For step 2, a portion of the first aqueous phase solution and a portion of the third aqueous phase solution are added to the oil phase solution, and the reaction is carried out for a first set time, including: adding a portion of the first aqueous phase solution to the oil phase solution, stirring for 20 min-60 min, introducing nitrogen gas, heating to 40℃-60℃, and then adding a portion of the third aqueous phase solution to the oil phase solution, and reacting for 30 min-60 min.

[0062] By performing the above operations, a stable first crosslinking agent undergoes a crosslinking reaction with the monomers in the first monomer composition, thereby achieving the formation of a partial core. For example, the content of the first aqueous phase solution added in step 2 is 30%-70% of the total amount of the first aqueous phase solution, and correspondingly, the content of the third aqueous phase solution added is 30%-70% of the total amount of the third aqueous phase solution.

[0063] For step 3, the remaining first aqueous phase solution, second aqueous phase solution, and remaining third aqueous phase solution are added to the reaction system, and the reaction is continued for a second set time to prepare polymer microspheres. This includes: adding the remaining first aqueous phase solution and second aqueous phase solution to the reaction system, reacting for 10 min-20 min, adding the remaining third aqueous phase solution to the reaction system, reacting for 3 h-6 h, and then cooling and discharging the material to prepare polymer microspheres.

[0064] By performing the above operations, the remaining stable first crosslinking agent is crosslinked with the monomer in the first monomer composition to form the core of the remaining portion, and the unstable second crosslinking agent is crosslinked with the monomer in the second monomer composition to form the shell and cover the outside of the core.

[0065] In another aspect, embodiments of the present invention also provide a composite profile control agent, which comprises any of the polymer microspheres, phenolic resin crosslinking agent, and water described above. The concentration of the polymer microspheres is 1000 mg / L-5000 mg / L; the mass concentration of the phenolic resin crosslinking agent is 500 mg / L-4000 mg / L.

[0066] In the composite profile control agent, the concentration of polymer microspheres includes, but is not limited to, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4500 mg / L, and 5000 mg / L. The concentration of phenolic resin crosslinking agent includes, but is not limited to, 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, and 4000 mg / L.

[0067] For example, the water involved in the composite profile control agent can be oilfield reinjection water, and the active ingredients are also applicable to oilfield reinjection water with high salinity, which can achieve energy saving while obtaining excellent profile control effect.

[0068] The composite profile control agent provided in this invention is based on the use of the aforementioned reactive polymer microspheres, which synergistically interact with a phenolic resin crosslinking agent. This results in excellent temperature and salt resistance. The polymer microspheres are stable at room temperature and do not exhibit reactivity. In application, the polymer microspheres combine with the phenolic resin crosslinking agent to form the composite profile control agent and react in the formation environment. Specifically, the unstable second crosslinking agent within the outer shell of the polymer microspheres gradually decomposes, releasing the long-chain polymer structure and exposing reactive groups. These reactive groups crosslink with the phenolic resin crosslinking agent, forming a large-volume network aggregate that effectively seals large pores in the formation. Simultaneously, this network aggregate exhibits viscoelasticity, allowing it to deform under pressure and pass through pores, achieving a migration-sealing-breakthrough-re-migration effect.

[0069] The composite profile control agent provided in this invention exhibits excellent temperature and salt resistance, making it suitable for profile control and flooding operations in high-temperature, high-salinity reservoirs. Studies have shown that under conditions of 70℃-130℃, the formation time of aggregates is 5h-20d, the salinity of the water used for preparation can reach up to 100,000mg / L, the aggregates exhibit stable performance, and the high-temperature aging time is >180d. Model experiments and field applications demonstrate that the composite profile control agent can achieve deep migration and ensure its plugging effect in high-temperature, high-salinity environments.

[0070] In another aspect, embodiments of the present invention also provide a water-blocking and profile control method, which employs the aforementioned composite profile control agent.

[0071] The composite profile control agent provided in this embodiment of the invention can be used for water shut-off and profile control operations through online injection. It can be injected one-to-one at the wellhead or one-to-one or one-to-many via the water distribution room.

[0072] Exemplary embodiments of the present invention will now be described in more detail. While exemplary embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0073] Example 1

[0074] Example 1 provides a polymer microsphere, which is prepared by the following method:

[0075] Step 1: Dissolve 9g acrylamide, 4g acrylic acid, 0.8g N-vinylpyrrolidone (NVP), and 0.6g of the stabilizing crosslinking agent N,N'-methylenebisacrylamide in 22mL of water, stir well, and adjust the pH to 7-8 to obtain the first aqueous phase solution.

[0076] Step 2: Dissolve 7.2g acrylamide, 3g acrylic acid, 0.9g methyl methacrylate, and 0.15g of unstable crosslinking agent polyethylene glycol diacrylate in 18mL of water, stir well, and adjust the pH to 7-8 to obtain the second aqueous phase solution.

[0077] Step 3: Dissolve 0.05g of potassium persulfate in 3mL of water and stir until homogeneous to obtain a third aqueous phase solution.

[0078] Step 4: Disperse 8g of a mixture of emulsifiers SPAN80 and TWEEN60 (mass ratio 1:1) evenly in 60mL of white oil to obtain an oil phase solution.

[0079] Step 5: Place the oil phase solution in the reaction vessel, and add a portion of the first aqueous phase solution (accounting for 60% of the total volume of the first aqueous phase solution) dropwise while stirring. After stirring and emulsifying for 30 minutes, purge with nitrogen for 30 minutes. After heating to 40°C, add a portion of the third aqueous phase solution (accounting for 60% of the total volume of the third aqueous phase solution) dropwise, and then continue the reaction for 30 minutes.

[0080] Step 6: Add the remaining first aqueous phase solution and second aqueous phase solution dropwise to the reaction system. After reacting for 20 minutes, add the remaining third aqueous phase solution dropwise, and then continue the reaction for 4 hours. After the reaction is completed, cool to room temperature and discharge to obtain an emulsion containing reactive polymer microspheres.

[0081] The emulsion containing reactive polymer microspheres has a solid content of 35%, and the initial median particle size of the polymer microspheres is 14.8 μm, which is a micron-sized emulsion.

[0082] Example 2

[0083] Example 2 provides a polymer microsphere, which is prepared by the following method:

[0084] Step 1: Dissolve 6g acrylamide, 2g acrylic acid, 0.6g 2-acrylamido-2-methylpropanesulfonic acid, and 0.2g crosslinking agent tetraallyl ammonium chloride in 20mL of water, stir well, and adjust the pH to 7-8 to obtain the first aqueous phase solution.

[0085] Step 2: Dissolve 3g acrylamide, 1g acrylic acid, 0.4g methyl methacrylate, and 0.08g unstable crosslinking agent polyethylene glycol dimethacrylate in 10mL of water, stir well, and adjust the pH to 7-8 to obtain the second aqueous phase solution.

[0086] Step 3: Dissolve 0.015g of potassium persulfate in 3mL of water and stir until homogeneous to obtain a third aqueous phase solution.

[0087] Step 4: Disperse 15g of a mixture of emulsifiers SPAN80 and TWEEN80 (mass ratio 1:1) evenly in 70mL of paraffin oil to obtain an oil phase solution.

[0088] Step 5: Place the oil phase solution in a reaction vessel, and add a portion of the first aqueous phase solution (accounting for 50% of the total volume of the first aqueous phase solution) dropwise while stirring. After stirring and emulsifying for 30 minutes, purge with nitrogen for 30 minutes. After heating to 60°C, add a portion of the third aqueous phase solution (accounting for 50% of the total volume of the third aqueous phase solution) dropwise, and then continue the reaction for 60 minutes.

[0089] Step 6: Add the remaining first aqueous phase solution and second aqueous phase solution dropwise to the reaction system. After reacting for 20 minutes, add the remaining third aqueous phase solution dropwise, and then continue the reaction for 4 hours. After the reaction is completed, cool to room temperature and discharge to obtain an emulsion containing reactive polymer microspheres.

[0090] The emulsion containing reactive polymer microspheres has a solid content of 25% and an initial median particle size of 0.9 μm, classifying it as a nanoscale emulsion.

[0091] Example 3

[0092] Example 3 provides a series of composite profile control agents, which include the polymer microspheres obtained in Example 1, phenolic resin crosslinking agent, and oilfield reinjection water. The concentration of the polymer microspheres is 3000 mg / L; the concentration of the phenolic resin crosslinking agent is 3000 mg / L, and the balance is oilfield reinjection water.

[0093] Different composite profile control agents were formulated for oilfield reinjection water with different salinity, and the elastic modulus of the aggregates formed at different times was tested. The relevant parameters are shown in Table 1 below.

[0094] Table 1

[0095] Reinjection water salinity, mg / L 6122 11900 33970 89423 100017 5d aggregate elastic modulus, MPa 1.1 2.3 7.6 12.8 18.3 20d aggregate elastic modulus, MPa 1.4 2.9 8.2 12 16.5 60d aggregate elastic modulus, MPa 1.5 2.4 9.1 14.5 10.3 90d aggregate elastic modulus, MPa 1.0 1.6 6.4 10.6 2.7 180 Cohesive modulus, MPa 0.8 0.9 2.4 1.2 0.6

[0096] As shown in Table 1, the composite profile control agent prepared with reinjection water of different mineralization degrees still has high strength when observed up to 180 days, indicating that the composite profile control agent has excellent profile control performance.

[0097] Example 4

[0098] Example 4 provides a series of composite profile control agents, including the polymer microspheres obtained in Example 2, phenolic resin crosslinking agent and oilfield reinjection water. For oilfield reinjection water with specific salinity, different concentrations of composite profile control agents were prepared, and the elastic modulus of the aggregates formed at different times and temperatures was tested. The relevant parameters are shown in Table 2 below.

[0099] Table 2

[0100]

[0101] As shown in Table 2, the composite profile control agents with different concentrations of active ingredients can all form aggregates at temperatures ranging from 70℃ to 130℃. The aggregate formation time varies from 5h to 20d, and the aggregates all have a certain strength, which can ensure the sealing effect. This indicates that the composite profile control agent has excellent profile control performance.

[0102] Example 5

[0103] Example 5 provides a composite profile control agent comprising the polymer microspheres obtained in Example 1, a phenolic resin crosslinking agent, and oilfield reinjection water. The concentration of the polymer microspheres is 3000 mg / L; the concentration of the phenolic resin crosslinking agent is 2000 mg / L, and the remainder is oilfield reinjection water.

[0104] Based on the composite profile control agent provided in Example 5, plugging and profile control operations were carried out on a well group in the North China Oilfield. The production relationship curves after the specific well group operation are shown in the appendix. Figure 1 After the plugging and adjustment were implemented, the ramp-up pressure of the water injection well was 3MPa, and the daily oil production of the corresponding oil well increased from 15.1t to 22.8t, with a peak daily increase of 7.7t. The overall water cut of the well group decreased from 62.9% to 46.1%.

[0105] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polymer microsphere, characterized in that, The polymer microspheres comprise: a core and a shell covering the outside of the core; The core is prepared by a crosslinking reaction of a first monomer composition and a first crosslinking agent. The first monomer composition includes acrylamide, acrylic acid, and at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate. The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide and tetraallyl ammonium chloride. The outer shell is prepared by a crosslinking reaction of a second monomer composition and a second crosslinking agent. The second monomer composition includes at least one of acrylamide, acrylic acid, methyl methacrylate, and butyl acrylate. The second crosslinking agent is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol diacrylate.

2. The polymer microspheres according to claim 1, characterized in that, The mass ratio of the first monomer composition to the first crosslinking agent is 4 to 45:1; In the first monomer composition, the acrylamide is 50%-70% by mass, the acrylic acid is 10%-30% by mass, and at least one of N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and sodium styrene sulfonate is 2%-10% by mass.

3. The polymer microspheres according to claim 1, characterized in that, The mass ratio of the second monomer composition to the second crosslinking agent is 10 to 80:1; In the second monomer composition, the acrylamide is 50%-70% by mass, the acrylic acid is 10%-30% by mass, and at least one of methyl methacrylate and butyl acrylate is 2%-10% by mass.

4. The polymer microspheres according to any one of claims 1-3, characterized in that, The core has a particle size in the nanometer range, and the outer shell has a particle size in the micrometer range.

5. A method for preparing polymer microspheres, characterized in that, The polymer microspheres are as described in any one of claims 1-4; The preparation method of the polymer microspheres is as follows: A first aqueous solution is prepared using a first monomer composition, a first crosslinking agent, and water; a second aqueous solution is prepared using a second monomer composition, a second crosslinking agent, and water; a third aqueous solution is prepared by dispersing an initiator in water; and an oil phase solution is prepared by dispersing an emulsifier in solvent oil. A portion of the first aqueous phase solution and a portion of the third aqueous phase solution are added to the oil phase solution, and the reaction is carried out for a first set time. The remaining first aqueous solution, second aqueous solution, and remaining third aqueous solution are added to the reaction system, and the reaction is continued for a second set time to prepare the polymer microspheres.

6. The method for preparing polymer microspheres according to claim 5, characterized in that, The step of adding a portion of the first aqueous phase solution and a portion of the third aqueous phase solution to the oil phase solution and reacting for a first set time includes: Add a portion of the first aqueous phase solution to the oil phase solution, stir for 20-60 minutes, introduce nitrogen gas, heat to 40°C-60°C, then add a portion of the third aqueous phase solution to the oil phase solution, and react for 30-60 minutes.

7. The method for preparing polymer microspheres according to claim 5, characterized in that, The process involves adding the remaining first aqueous phase solution, the second aqueous phase solution, and the remaining third aqueous phase solution to the reaction system, and continuing the reaction for a second predetermined time to prepare the polymer microspheres, comprising: The remaining first aqueous phase solution and second aqueous phase solution are added to the reaction system. After reacting for 10-20 minutes, the remaining third aqueous phase solution is added to the reaction system. After reacting for 3-6 hours, the mixture is cooled and discharged to obtain the polymer microspheres.

8. The method for preparing polymer microspheres according to any one of claims 5-7, characterized in that, The first monomer composition accounts for 20%-45% of the mass percentage of the first aqueous solution, and the first crosslinking agent accounts for 1%-5% of the mass percentage of the first aqueous solution; The second monomer composition accounts for 20%-45% of the mass percentage of the second aqueous solution, and the second crosslinking agent accounts for 0.5%-2% of the mass percentage of the second aqueous solution.

9. A composite profile control agent, characterized in that, The composite profile control agent comprises the polymer microspheres, phenolic resin crosslinking agent, and water as described in any one of claims 1-4; The concentration of the polymer microspheres is 1000 mg / L-5000 mg / L; The mass concentration of the phenolic resin crosslinking agent is 500 mg / L-4000 mg / L.

10. A method for water shut-off and profile control, characterized in that, The water-blocking and profile control method uses the composite profile control agent described in claim 9.

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