Water plugging profile control agent and preparation method thereof

Abstract

This invention relates to a water-blocking and profile control agent and its preparation method, belonging to the technical field of oilfield chemical products. The water-blocking and profile control agent is prepared via reverse emulsion polymerization. The raw materials include an aqueous phase solution, an oil phase solution, and an initiator. The aqueous phase solution contains acrylamide, anionic monomers, cationic monomers, temperature- and salt-resistant monomers, a crosslinking agent, silane coupling agent-modified carbon nanotubes, a reinforcing agent, modified tannic acid, and water. The oil phase solution contains base oil and an emulsifier. This invention, by adding silane coupling agent-modified carbon nanotubes, a reinforcing agent, and modified tannic acid to reverse emulsion polymerization, produces a water-blocking and profile control agent with good injectability, high strength after water absorption and swelling, and controllable swelling time. Furthermore, it can achieve secondary crosslinking under high temperature and high salt conditions. This not only allows it to match oil layers with different permeability and heterogeneous formations but also effectively adapts to the plugging of deep wells at higher pressures and depths, resulting in superior plugging performance.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical products technology, and in particular to a water shut-off and profile control agent and its preparation method. Background Technology

[0002] Currently, most water-injection oilfields in my country have entered the high water-cut extraction stage. To extend the development life of oilfields and improve reservoir recovery, it is essential to monitor the dynamics of water production in oil wells in real time during production and to take timely and effective water control measures. Water shut-off and profile control technology, as a conventional water control method, can increase formation pressure and improve the injected water sweep efficiency in oil-bearing formations, thereby enhancing crude oil recovery.

[0003] Polymer microsphere-type water-blocking and profile control agents can gradually absorb water and swell during deep migration, deforming and remaining at the pores, or passing through the pore throat under external pressure, recovering their deformation and continuing to move forward, thereby achieving deep plugging and profile control. However, the polymer microspheres used in existing deep profile control technologies are mostly acrylamide polymers, which have poor shear resistance and mechanical strength in the swollen state, and are easily sheared and broken during flow migration, resulting in reduced plugging effectiveness. Chinese Patent 202211237355.3 discloses an amphoteric water-blocking and profile control agent and its preparation method, but the plugging effect of the amphoteric water-blocking and profile control agent prepared by this patent needs further improvement.

[0004] Therefore, there is an urgent need to develop a water shut-off and profile control agent that retains excellent shear resistance and high mechanical strength after swelling, and has a better sealing effect, so as to improve the adaptability of existing technologies in water control and profile control in high water-cut reservoirs. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a water shut-off and profile control agent and its preparation method. The water shut-off and profile control agent prepared in this invention has good injectability, high strength after water absorption and swelling, and controllable swelling time. Furthermore, it can achieve secondary cross-linking under high temperature and high salinity conditions. It can not only match oil layers with different permeability and heterogeneous formations, but also adapt well to the plugging of deep well channels with higher pressure and greater depth, resulting in a superior plugging effect.

[0006] The present invention provides a water-blocking and profile control agent in a first aspect, wherein the water-blocking and profile control agent is prepared by reverse emulsion polymerization, and the raw materials for preparation include an aqueous phase solution, an oil phase solution and an initiator; the aqueous phase solution includes acrylamide, anionic monomer, cationic monomer, temperature-resistant and salt-resistant monomer, crosslinking agent, silane coupling agent modified carbon nanotubes, reinforcing agent, modified tannic acid and water; the oil phase solution includes base oil and emulsifier.

[0007] Preferably, the modified tannic acid is obtained by a ring-opening addition reaction of tannic acid and unsaturated glycidyl ester. More preferably, the unsaturated glycidyl ester is glycidyl methacrylate. More preferably, the molar ratio of the unsaturated glycidyl ester to the tannic acid is (3~5):1.

[0008] Preferably, the silane coupling agent modified carbon nanotube is a 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotube.

[0009] Preferably, the reinforcing agent is polyvinyl alcohol or polyvinyl alcohol-grafted polyacrylamide.

[0010] Preferably, the anionic monomer is at least one of α-allyl sulfonic acid, vinyl sulfonic acid, vinylbenzene sulfonic acid, allyl sulfonic acid, itaconic acid, or allylbenzene sulfonic acid; the cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, octadecyltrimethylbenzylallylammonium bromide, or dimethylethylallylammonium chloride; the temperature- and salt-resistant monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, sodium 3-acrylamido-3-methylbutyrate, p-styrenepropanesulfonic acid, or 4-vinylpyridine; and the crosslinking agent is N,N-methylenebisacrylamide, N, At least one of N-methylenebismethylacrylamide or N,N'-m-phenylenebismaleimide; the base oil is at least one of aliphatic hydrocarbons, aromatic hydrocarbons or alicyclic compounds, or the base oil is kerosene and / or white oil; the emulsifier comprises Span, Tween, and alkylphenol polyoxyethylene ether; and / or the initiator comprises an azo initiator and a redox initiator, preferably, the azo initiator is a water-soluble azo initiator and / or an oil-soluble azo initiator, preferably, the mass ratio of the azo initiator, the oxidant in the redox initiator to the acrylamide is (1.01~1.02):(0.01~0.12):(100~150).

[0011] Preferably, the aqueous phase solution contains the following components by weight: 100-150 parts acrylamide, 15-25 parts anionic monomer, 18-25 parts cationic monomer, 15-30 parts temperature- and salt-resistant monomer, 1-2 parts crosslinking agent, 0.005-0.85 parts silane coupling agent modified carbon nanotubes, 0.5-12 parts reinforcing agent, 0.2-15 parts modified tannic acid, and 150-200 parts water; the oil phase solution contains the following components by weight: 325-335 parts base oil and 122-128 parts emulsifier.

[0012] Preferably, the aqueous solution further comprises a metal complexing agent and / or a molecular weight regulator, and / or the raw materials for preparation further comprise a phase inversion agent; preferably, the metal complexing agent is at least one of disodium ethylenediaminetetraacetate, sodium alginate, or diethyltriaminepentaacetic acid, and the molecular weight regulator is at least one of isopropanol, isobutanol, tert-butanol, pentaerythritol, thiol, sodium metaphosphate, or sodium formate; preferably, the mass ratio of the metal complexing agent, the molecular weight regulator, and the acrylamide is (0.3~2):(0.3~2):(100~150); preferably, the phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, or octylphenol polyoxyethylene ether; preferably, the mass ratio of the phase inversion agent to the acrylamide is (10~20):(100~150).

[0013] The present invention provides a second aspect of a method for preparing the water-blocking and profile control agent described in the first aspect, the method comprising the following steps:

[0014] (1) Acrylamide, anionic monomer, cationic monomer, temperature-resistant and salt-resistant monomer, crosslinking agent, silane coupling agent modified carbon nanotube, reinforcing agent and modified tannic acid are added to water and mixed to obtain an aqueous solution;

[0015] (2) Mix the base oil and emulsifier to obtain an oil phase solution;

[0016] (3) The aqueous solution is added to the oil solution and stirred to emulsify, thereby obtaining a reverse emulsion;

[0017] (4) The reverse emulsion is subjected to polymerization reaction under the action of an initiator to obtain the water-blocking profile control agent.

[0018] Preferably, in step (1), a metal complexing agent and / or a molecular weight regulator are added to the aqueous solution; in step (1), the pH value of the aqueous solution is adjusted to 6.0~6.2; and / or in step (4), after initiating the polymerization reaction, a step of adding a phase inversion agent to obtain the water-blocking profile control agent is also included.

[0019] In a third aspect, the present invention provides a water-blocking and profile control agent prepared by the preparation method described in the second aspect of the present invention.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] (1) In this invention, water-blocking and profile control agent is prepared by reverse emulsion polymerization. In the process of preparing water-blocking and profile control agent by reverse emulsion polymerization, silane coupling agent modified carbon nanotubes are introduced as nano core particles (nano reinforcing particles). Compared with methacryloyloxy silane surface modification of nano calcium carbonate, nano silica or nano silicon nitride, the use of silane coupling agent modified carbon nanotubes can not only improve the microstructure and mechanical stability of water-blocking and profile control agent, but also achieve a higher deep plugging effect and a more durable water control and profile control effect in application. It not only improves shear resistance and swelling retention rate, but also enhances the deformation recovery ability of microspheres at the pore throat. This allows the water-blocking and profile control agent of this invention to be more uniformly and deeply distributed in the high-permeability channel after injection into the reservoir, forming a stable plug, which is conducive to improving the sweep efficiency of injected water, reducing ineffective water channeling, and significantly improving the oil recovery rate of the reservoir.

[0022] (2) The addition of modified tannic acid to the water-blocking and profile control agent prepared in this invention has a very high gain effect: a. Tannic acid has a very three-dimensional molecular structure, which contains abundant phenolic hydroxyl groups, carboxyl groups, ester groups and heterocyclic structures, and has multiple crosslinking sites; b. After modification, the molecular groups of tannic acid have 1 to 3 polymerizable double bond structures, which can serve as molecular radiation centers and increase the strength of the molecular structure; c. Due to the presence of the tannic acid structure, under high temperature / high calcium and magnesium ion conditions, the water-blocking and profile control agent can be crosslinked again, the gel strength can be improved again, and the sealing effect in high temperature and high salt environment is more significant.

[0023] (3) In some preferred technical solutions, polyvinyl alcohol (PVA) is introduced as a reinforcing agent in the process of preparing water-blocking and profile control agent by reverse emulsion polymerization. This not only improves the strength and shear resistance of the water-blocking and profile control agent, but also optimizes its swelling characteristics. Under high temperature conditions, it can increase the gel strength of the swollen molecules, thereby improving the plugging and profile control effect in deep reservoirs.

[0024] (4) In the process of preparing the water-blocking and profile control agent, the present invention also introduces a temperature-resistant and salt-resistant monomer. The rigid side chains and / or cyclic groups in the temperature-resistant and salt-resistant monomer enable the water-blocking and profile control agent in the present invention to better protect the main chain under high temperature conditions, avoid the main chain from being degraded by heat, and significantly improve the temperature resistance of the water-blocking and profile control agent.

[0025] (5) The water-blocking and profile control agent prepared in this invention is an amphoteric polymer, which enables the water-blocking and profile control agent in this invention to have an anti-polyelectrolyte effect, thus giving the water-blocking and profile control agent good salt resistance. The preparation method of this invention is simple, and the performance indicators of the final water-blocking and profile control agent product can be controlled by the preparation method. The prepared product has stable performance and is suitable for large-scale industrial production. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. 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.

[0027] The present invention provides a water-blocking and profile control agent in a first aspect, wherein the water-blocking and profile control agent is prepared by reverse emulsion polymerization, and the raw materials for preparation include an aqueous phase solution, an oil phase solution and an initiator; the aqueous phase solution includes acrylamide, anionic monomer, cationic monomer, temperature-resistant and salt-resistant monomer, crosslinking agent, silane coupling agent modified carbon nanotubes, reinforcing agent, modified tannic acid and water; the oil phase solution includes base oil and emulsifier.

[0028] This invention provides a water-blocking and profile control agent with excellent temperature and salt resistance, high strength after swelling, and superior sealing performance. The agent is prepared by adding silane coupling agent-modified carbon nanotubes, reinforcing agents, and modified tannic acid during the reverse emulsion polymerization process. Compared with traditional water-blocking and profile control agents, this agent exhibits better sealing efficiency and strength at the same dosage. Furthermore, this agent is suitable for sealing channels at higher pressures and greater depths, and is better suited to various reservoir conditions.

[0029] In this invention, a water-blocking and profile control agent is prepared via reverse emulsion polymerization. During this process, silane coupling agent-modified carbon nanotubes are introduced as the nano-core particles. Compared to methacryloyloxy silane-modified nano-calcium carbonate, nano-silica, or nano-silicon nitride, the use of silane coupling agent-modified carbon nanotubes not only improves the microstructure and mechanical stability of the water-blocking and profile control agent, but also achieves a higher depth-sealing effect and a more durable water-controlling and profile control effect. It not only enhances shear resistance and swelling retention rate, but also strengthens the deformation recovery ability of the microspheres at the pore throat. This allows the water-blocking and profile control agent of this invention to be more uniformly and deeply distributed in high-permeability channels after injection into the reservoir, forming a stable seal. This, in turn, helps to improve the sweep efficiency of injected water, reduce ineffective water channeling, and significantly improve the oil recovery rate.

[0030] The addition of modified tannic acid to the water-blocking and profile control agent prepared in this invention has a very high gain effect: a) Tannic acid has a very three-dimensional molecular structure containing abundant active groups, such as abundant phenolic hydroxyl groups, carboxyl groups, ester groups, and / or heterocyclic structures, and possesses multiple crosslinking sites; b) After modification, the tannic acid molecular groups have 1-3 polymerizable double bond structures, which can serve as molecular radiation centers, increasing the molecular structural strength. Modified tannic acid can participate in copolymerization as a functional monomer in reverse emulsion polymerization, enhancing molecular stability and gel strength. It can also react with reinforcing agents during heating. For example, polyvinyl alcohol (PVA) undergoes a cross-linking reaction, enhancing the gel strength after molecular dissolution; c. Modified tannic acid, due to its own reducing properties, can also enhance the product molecules' tolerance to high temperatures; due to the existence of the tannic acid structure, under high temperature / high calcium and magnesium ion conditions, the water-blocking and profile control agent can be cross-linked again, and the gel strength can be improved again. The sealing effect in high temperature and high salt environment is more significant. That is, due to its special molecular structure, tannic acid can undergo secondary cross-linking in high temperature environment when the calcium and magnesium ion concentration increases to a certain condition, thereby further improving the gel strength of the product (water-blocking and profile control agent) and enhancing the sealing performance of the product.

[0031] According to some preferred embodiments, the modified tannic acid is obtained by a ring-opening addition reaction of tannic acid and unsaturated glycidyl ester. Preferably, the unsaturated glycidyl ester is glycidyl methacrylate. Preferably, the molar ratio of the unsaturated glycidyl ester to the tannic acid is (3~5):1 (e.g., 3:1, 3.5:1, 4:1, 4.5:1 or 5:1).

[0032] In this invention, during the preparation of a water-blocking and profile control agent via reverse emulsion polymerization, modified tannic acid, obtained by ring-opening addition reaction of tannic acid and unsaturated glycidyl ester, is used. Compared to directly adding unmodified tannic acid, this significantly improves the performance of the water-blocking and profile control agent. This is because the modified tannic acid molecule introduces polymerizable unsaturated groups, which can form covalent bonds with acrylamide monomers during polymerization, uniformly embedding themselves inside the polymer microspheres, significantly improving the structural stability, shear resistance, and sealing effect of the microspheres. The modified tannic acid achieves a balance between molecular polarity and lipophilicity, maintaining good dispersion with both the oil and aqueous phases in the reverse emulsion, thus distributing more uniformly within the polymer microsphere structure during polymerization. In contrast, unmodified tannic acid relies solely on hydrogen bonding or physical adsorption to interact with the polymer microspheres, resulting in weaker binding strength and stability, uneven distribution, and limited enhancement effect.

[0033] According to some specific embodiments, the modified tannic acid is obtained by a ring-opening addition reaction of tannic acid and unsaturated glycidyl ester; the specific operation is as follows: tannic acid, catalyst, solvent and unsaturated glycidyl ester are mixed and subjected to a ring-opening addition reaction to obtain the modified tannic acid; the molar ratio of the unsaturated glycidyl ester to the tannic acid is 3~5:1; preferably, the unsaturated glycidyl ester is glycidyl methacrylate; preferably, the catalyst is triphenylphosphine, and the amount of the catalyst is 8~15% of the mass of the tannic acid (e.g., 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%); preferably, the solvent is at least one of N,N-dimethylformamide and dimethyl sulfoxide; and / or the temperature of the ring-opening addition reaction is 90~115℃ (e.g. 90℃, 100℃, 105℃, 110℃ or 115℃).

[0034] According to some preferred embodiments, the silane coupling agent modified carbon nanotubes are 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes. The 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes of this invention are modified carbon nanotubes using 3-(methacryloyloxy)propyltrimethoxysilane as a silane coupling agent. The source of the silane coupling agent is not specifically limited; commercially available products or those prepared using existing technologies are acceptable. For example, the preparation of the 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes in this invention includes: acid treatment of single-walled carbon nanotubes with concentrated nitric acid, followed by adjusting the pH of the system to 7 to obtain pretreated carbon nanotubes; then, glacial acetic acid, pretreated carbon nanotubes, and 3-(methacryloyloxy)propyltrimethoxysilane are sequentially added to water for modification. Specifically, this invention... The 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes described herein can be prepared by the following method: 100 mg of single-walled carbon nanotubes (SWCNTs) are added to 60 mL of concentrated nitric acid (e.g., concentrated nitric acid with a mass fraction of 65-69%), and refluxed at 90 °C for 6 h to obtain an acid-treated carbon nanotube dispersion (acid-treated SWCNT dispersion); the acid-treated SWCNT dispersion is washed with deionized water until pH=7, then filtered and dried to obtain pretreated carbon nanotubes; then 20 g of glacial acetic acid, 3 g of pretreated carbon nanotubes, and 10-15 g of 3-(methacryloyloxy)propyltrimethoxysilane are added sequentially to 100 g of water, and the mixture is vigorously shaken at 75 °C for 30 min, then filtered and dried to obtain 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes (nanocore particles).

[0035] According to some preferred embodiments, the reinforcing agent is polyvinyl alcohol (PVA). In this invention, it is preferred that polyvinyl alcohol (PVA) be introduced as a reinforcing agent during the preparation of water-blocking and profile control agent by reverse emulsion polymerization. This not only improves the strength and shear resistance of the water-blocking and profile control agent, but also optimizes its swelling characteristics. Under high temperature conditions, it can increase the gel strength of the swollen molecules, thereby improving the plugging and profile control effect in deep reservoirs. The possible reason is that PVA molecular chains contain hydroxyl groups, which can form hydrogen bonds with acrylamide polymer segments, enhancing the internal network structure of polymer microspheres, thereby improving the mechanical strength and shear resistance of the microspheres in the swollen state.

[0036] According to some preferred embodiments, the reinforcing agent is polyvinyl alcohol-grafted polyacrylamide; the preparation of the polyvinyl alcohol-grafted polyacrylamide is as follows: polyvinyl alcohol is heated and dissolved in deionized water to prepare a polyvinyl alcohol aqueous solution with a mass fraction of 3-6%; then acrylamide monomer, N,N-methylenebisacrylamide crosslinking agent, functional monomer, co-solvent, and surfactant are added to the polyvinyl alcohol aqueous solution and mixed to obtain a mixed system; then the temperature and pH of the mixed system are adjusted to 0-5℃ and 7-7.2, respectively, and nitrogen is purged for 20-40 min to remove oxygen; then ammonium persulfate initiator is added under nitrogen protection, and the reaction is maintained at 80-90℃ for 0.5-4 h; then the product is removed from the solution, washed, and dried to constant weight to obtain polyvinyl alcohol-grafted polyacrylamide; wherein, the functional monomer is formed by reacting N-vinylimidazolium (also known as: 1-vinyl-1H-imidazolium) with epichlorohydrin; the functional monomer... The preparation of the monomer is as follows: N-vinylimidazolium and epichlorohydrin are thoroughly mixed at a mass ratio of 1:(0.8~1.2), stirred and refluxed under nitrogen for 12~36 h, washed with diethyl ether and vacuum dried for 4~6 h to obtain the functional monomer; the co-solvent is nonylphenol polyoxyethylene ether, the surfactant is sodium dodecylbenzenesulfonate and / or sodium dodecyl sulfate, the amount of acrylamide monomer is 0.8~1.2 times the mass of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution, and the mass ratio of acrylamide monomer, N,N-methylenebisacrylamide, the functional monomer, the co-solvent, the surfactant and the initiator is 10:(0.2~0.3):(2~4):(0.01~0.05):(0.01~0.05):(0.001~0.003); under this dosage ratio, the grafting rate of polyvinyl alcohol grafted polyacrylamide is in the range of 4~10%.

[0037] In this invention, the polyvinyl alcohol-grafted polyacrylamide prepared above is preferably used as a reinforcing agent. It is formed by copolymerizing polyvinyl alcohol with acrylamide containing functional monomers. Compared with polyvinyl alcohol and ordinary polyvinyl alcohol-grafted polyacrylamide, the sealing effect of the water-blocking and profile control agent is significantly improved. The reinforcing agent preferably used in this invention has better strength and flexibility, can be more tightly embedded in the cross-linked structure, and can act as a "molecular spring" in the polymer network structure, significantly improving the strength, toughness and shear resistance of the gel. It can effectively improve the shear resistance and structural stability of the water-blocking and profile control agent in the complex high temperature and high salinity environment of the reservoir, ensuring excellent sealing effect and water-blocking effect durability. The introduction of functional monomers in the polyvinyl alcohol-grafted polyacrylamide of this invention can improve the adhesion ability of the profile control agent in the reservoir pores, thereby forming a more stable plugging layer, and at the same time, it is beneficial to enhance the mechanical strength and pressure resistance of the plugging layer.

[0038] According to some preferred embodiments, the anionic monomer is at least one of α-allyl sulfonic acid, vinyl sulfonic acid, vinylbenzene sulfonic acid, allyl sulfonic acid, itaconic acid, or allylbenzene sulfonic acid; the anionic monomer in this invention is a sulfonic acid anionic monomer, and the anionic monomer in this invention includes, but is not limited to, sulfonic acid anionic monomers, and may also be sulfonates of the above-mentioned anionic monomers, for example, sodium α-allyl sulfonate, potassium α-allyl sulfonate, or ammonium α-allyl sulfonate, etc.; the cationic monomer is methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, octadecyltrimethylammonium chloride, etc. The polymer contains at least one of benzyl allyl ammonium bromide or dimethyl ethyl allyl ammonium chloride; the cationic monomer is an ammonium salt cationic monomer. In this invention, by controlling the content of anionic monomers and cationic monomers and the content of other monomers within a reasonable range, the polymer molecular chain of the water-blocking and profile control agent prepared in this invention contains an equal number of positively and negatively charged groups, making it an electrically neutral amphoteric polymer. This polymer can exhibit a significant anti-polyelectrolyte effect, thereby ensuring that the hydration and swelling of the polymer microspheres formed in this invention are not affected by salinity within a certain salinity range, thus improving the salt resistance of the polymer microspheres. In some preferred embodiments, the cationic monomer is, for example, octadecyltrimethylbenzylallylammonium bromide. This invention does not specifically limit the source of octadecyltrimethylbenzylallylammonium bromide; it can be a directly purchased product or a product synthesized by existing methods. For example, in this invention, referring to existing preparation methods, the preparation of octadecyltrimethylbenzylallylammonium bromide includes: reacting octadecyldimethyl tertiary amine with benzyl chloride to obtain an intermediate, wherein the molar ratio of octadecyldimethyl tertiary amine to benzyl chloride is 1:(1.05~1.1), the reaction temperature is 75-85℃, and the reaction time is 4-8 hours. Then, the intermediate is reacted with allyl bromide to obtain octadecyltrimethylbenzylallylammonium bromide, wherein the molar ratio of the intermediate to the allyl bromide is 1:(1.1~1.2), the reaction temperature is 60-70℃, and the reaction time is 6~12 hours; specifically, the first step: in a flask equipped with a stirrer, thermometer, reflux condenser, and constant pressure dropping funnel, octadecyldimethyl tertiary amine and an appropriate amount of isopropanol (solvent) are added, and the mixture is heated in a water bath until it is completely dissolved (about 60-70℃). Under vigorous stirring, benzyl chloride is slowly added dropwise (the molar ratio is usually octadecyldimethyl tertiary amine: benzyl chloride = 1:1.05~1).1. Add a slight excess of benzyl chloride to ensure complete reaction of the tertiary amine; after the addition is complete, heat to 75-85℃ and continue stirring and reflux for 4-8 hours; the reaction progress can be monitored by thin-layer chromatography (TLC) or titration; after the reaction is complete, stop heating, cool to about 60℃, add an appropriate amount of acetone or diethyl ether to promote the precipitation of the product, filter, wash the solid several times with a small amount of acetone to obtain a white or slightly yellow waxy solid, vacuum dry to obtain the intermediate product; second step: in a dry flask equipped with a stirrer, thermometer, reflux condenser (with drying tube) and constant pressure dropping funnel, add the intermediate obtained in the first step and anhydrous acetonitrile (or DMF), heat and stir to dissolve, add allyl bromide (molar ratio of intermediate: allyl bromide = 1:1.1~1) 2) Dissolve in a small amount of anhydrous acetonitrile solvent and slowly add dropwise to the reaction flask through a dropping funnel. This step of the reaction is exothermic, and the temperature needs to be controlled at 50-60℃. After the addition is complete, raise the temperature to 60-70℃ and continue stirring for 6-12 hours. Due to the reduced reactivity of the quaternary ammonium salt, the second quaternization requires a longer reaction time and an excess of allyl bromide. After the reaction is complete, cool to room temperature. Pour the reaction solution into a large amount of anhydrous diethyl ether or acetone, stir, and precipitate the quaternary ammonium salt product. Filter and wash the precipitate repeatedly with a large amount of anhydrous diethyl ether to remove unreacted raw materials and solvent. Finally, place the obtained white solid product in a vacuum drying oven and dry thoroughly at 40-50℃ to obtain the final product, which is octadecyltrimethylbenzylallylammonium bromide.

[0039] According to some preferred embodiments, the temperature- and salt-resistant monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, sodium 3-acrylamido-3-methylbutyrate, p-styrenepropanesulfonic acid, or 4-vinylpyridine. The present invention also introduces the temperature- and salt-resistant monomer into the polymerization reaction. Because the temperature- and salt-resistant monomer contains rigid side chains and / or cyclic groups, these groups can better protect the polymer molecular backbone under high temperature and high salt conditions, preventing degradation of the polymer molecular backbone, thereby further improving the temperature and salt resistance of the polymer microspheres. The crosslinking agent is at least one of N,N-methylenebisacrylamide, N,N-methylenebismethylacrylamide, or N,N'-m-phenylenebismaleimide.

[0040] According to some preferred embodiments, the base oil is at least one of aliphatic hydrocarbons, aromatic hydrocarbons, or alicyclic compounds, or the base oil is at least one of kerosene or white oil; preferably, the aliphatic hydrocarbon is at least one of butane, pentane, octane, heptane, or hexane; preferably, the aromatic hydrocarbon is at least one of benzene, toluene, ethylbenzene, xylene, or cumene; preferably, the alicyclic compound is at least one of cyclopentane, cyclohexane, methylcyclohexane, or cyclooctane; it should be noted that, in this invention, at least one means any one or more of them mixed in any proportion to obtain a mixture.

[0041] According to some preferred embodiments, the emulsifier comprises Span, Tween, and alkylphenol polyoxyethylene ether; in some specific embodiments, the emulsifier comprises the following components by weight: 59-61 parts of Span (e.g., 59, 60, or 61 parts), 59-61 parts of Tween (e.g., 59, 60, or 61 parts), and 4-6 parts of alkylphenol polyoxyethylene ether (e.g., 4, 5, or 6 parts); in this invention, Span is preferably Span 80, Tween is preferably Tween 80, and alkylphenol polyoxyethylene ether is preferably octylphenol polyoxyethylene ether (OP-10).

[0042] According to some preferred embodiments, the initiator comprises an azo initiator and a redox initiator. The presence of this initiator enables the water-in-oil system formed by emulsifying the aqueous and oil phase solutions in this invention to form polymer microspheres via reverse emulsion polymerization. Preferably, the azo initiator is a water-soluble azo initiator and / or an oil-soluble azo initiator; the water-soluble azo initiator is azobisisobutyramidine hydrochloride and / or azobisisobutyramidine imidazoline hydrochloride; the oil-soluble azo initiator is azobisisobutyronitrile and / or azobisisoheptanenitrile; and the oxidant in the redox initiator is persulfate, hydrogen peroxide, or tert-butylpersulfate. The azo initiator comprises one or more of hydrogen peroxide, cumene hydrogen peroxide, dicumene peroxide, di-tert-butyl peroxide, and tert-butyl peroxide; the reducing agent in the redox initiator is at least one of sulfite, metabisulfite, hydroxylamine, thiourea, and ascorbic acid; preferably, the mass ratio of the azo initiator, the oxidant in the redox initiator, and the acrylamide is (1.01~1.02):(0.01~0.12):(100~150); specifically, the mass ratio of the water-soluble azo initiator to the oil-soluble azo initiator in the azo initiator is (0.01~0.02):(1~2).

[0043] According to some preferred embodiments, the contents of each component in the aqueous solution, by weight, are as follows: acrylamide 100-150 parts (e.g., 100, 110, 120, 130, 140, or 150 parts), anionic monomer 15-25 parts (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 parts), cationic monomer 18-25 parts (e.g., 18, 19, 20, 21, 22, 23, 24, or 25 parts), 15-30 parts (e.g., 15, 18, 20, 22, 25, 28, or 30 parts) of temperature- and salt-resistant monomer, 1-2 parts (e.g., 1, 1.2, 1.4, 1.5, 1.6, 1.8, or 2 parts) of crosslinking agent, and 0 parts of silane coupling agent-modified carbon nanotubes. 0.005 to 0.85 parts (e.g., 0.005 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or 0.85 parts), preferably 0.5 to 0.8 parts (e.g., 0.5 parts, 0.6 parts, 0.7 parts, or 0.8 parts), and 0.5 to 12 parts (e.g., 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, etc.). 10, 11, or 12 parts) preferably 3 to 8 parts (e.g., 3, 4, 5, 6, 7, or 8 parts), modified tannic acid 0.2 to 15 parts (e.g., 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts) preferably 1.5 to 3.5 parts (e.g., 1.5, 2, 2.5, 3, or 3).5 parts), water 150-200 parts (e.g., 150, 160, 170, 180, 190, or 200 parts); by weight, the content of each component in the oil phase solution is as follows: base oil 325-335 parts (e.g., 325, 328, 330, 332, or 335 parts) and emulsifier 122-128 parts (e.g., 122, 124, 125, 127, or 128 parts); Furthermore, experiments of this invention have confirmed that it is preferable to control the content of each component in the oil phase solution and the aqueous phase solution within the above ranges. For example, if the content of the temperature-resistant and salt-resistant monomer... Below the aforementioned range, it is not conducive to effectively improving the temperature and salt resistance of polymer microspheres. While a higher content of temperature and salt resistant monomers can enhance the properties to some extent, excessive amounts may lead to molecular chain transfer during reverse polymerization, resulting in a smaller molecular weight and ultimately negatively impacting the water-blocking and profile control effects of the polymer microspheres. Conversely, when the content of cationic or anionic monomers is below the aforementioned range, it is not conducive to the generation of the anti-polyelectrolyte effect, or the anti-polyelectrolyte effect is not significant, which is detrimental to the polymer's salt resistance. Furthermore, when the content of cationic or anionic monomers is below the aforementioned range, it is not conducive to the generation of the anti-polyelectrolyte effect, or the anti-polyelectrolyte effect is not obvious, thus negatively affecting the polymer's salt resistance. If the content of anionic monomers exceeds the above range, the polymer molecular chain length may be insufficient, resulting in a low swelling rate, which is not conducive to sealing and thus leads to excessively high construction costs. For example, in the preparation process of the water-blocking and profile control agent, if the amount of reinforcing agent is too large, it will cause a significant increase in the viscosity of the system, affecting the dispersibility and injection performance of the emulsion and reducing the uniform coverage effect of the water-blocking and profile control agent; if the amount is too small, the reinforcing effect will be insufficient, and it will not be able to effectively improve the mechanical strength and durability of the water-blocking and profile control agent, reducing the sealing effect; if the amount of modified tannic acid is too large, it may cause excessive cross-linking of the system or the formation of excessively large agglomerates, resulting in poor flowability of the water-blocking and profile control agent and difficulty in injection. The following factors affect the profile control effect: Insufficient dosage will prevent the active ingredients from fully promoting cross-linking and anti-oxidation, reducing the stability and durability of the plugging layer; excessive use of silane coupling agent-modified carbon nanotubes will cause agglomeration of carbon nanotubes, leading to uneven dispersion, reducing the stability and fluidity of the system, and affecting the uniform formation of the plugging layer; insufficient dosage will not effectively improve the mechanical properties and high-temperature and salt resistance of the polymer, weakening the plugging strength and environmental adaptability of the profile control agent. Therefore, it is preferable to control the content of the above components within the above range in this invention, which is more conducive to preparing a water-blocking profile control agent with excellent shear resistance, high strength after swelling, and better plugging effect. In this invention, unless otherwise specified, "parts" refers to "parts by weight". In specific embodiments and comparative examples, the unit of parts by weight can be uniformly "g" or "kg" or other weight units.

[0044] According to some preferred embodiments, the aqueous solution further comprises a metal complexing agent and / or a molecular weight regulator, and / or the preparation raw materials further comprise a phase inversion agent; preferably, the metal complexing agent is at least one selected from disodium ethylenediaminetetraacetate, sodium alginate, or diethyltriaminepentaacetic acid, and the molecular weight regulator is at least one selected from isopropanol, isobutanol, tert-butanol, pentaerythritol, thiol, sodium metaphosphate, or sodium formate; preferably, the mass ratio of the metal complexing agent, the molecular weight regulator, and the acrylamide is (0.3...). ~2): (0.3~2): (100~150); preferably, the phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether, and preferably, the mass ratio of the phase inversion agent to the acrylamide is (10~20): (100~150) (for example, it can be 10:100, 15:100, 20:100, 10:120, 15:120, 20:120, 10:150, 15:150 or 20:150).

[0045] The present invention provides a second aspect of a method for preparing the water-blocking and profile control agent described in the first aspect, the method comprising the following steps:

[0046] (1) Acrylamide, anionic monomer, cationic monomer, temperature-resistant and salt-resistant monomer, crosslinking agent, silane coupling agent modified carbon nanotubes, reinforcing agent and modified tannic acid are added to water and mixed to obtain an aqueous solution; in this invention, preferably, the pH value of the aqueous solution is adjusted to 6.0~6.2; in this invention, preferably, a pH adjuster is added to the aqueous solution to adjust its pH value to the above range. This invention does not specifically limit the type and amount of pH adjuster. Those skilled in the art can conventionally select according to needs. For example, conventional pH adjusters such as acetic acid and / or sodium hydroxide (e.g., sodium hydroxide aqueous solution) can be selected without adding new monomers that can participate in the reaction; in this invention, by adjusting the pH of the aqueous solution Within a suitable range, not only can the reaction rate of the polymerization reaction of the present invention be guaranteed to be within a suitable range, but also the molecular weight of the polymer microspheres formed in the present invention can be guaranteed to be within a suitable range. When the pH value of the mixed solution is lower than the above range, the reaction rate of the polymerization reaction will be too fast, and the molecular weight of the polymer will be reduced, which will lead to a decrease in the water absorption and swelling ratio of the polymer microspheres, and ultimately have an adverse effect on the sealing effect of the polymer microspheres. When the pH value of the mixed solution is higher than the above range, not only will the reaction rate of the polymerization reaction be reduced, but cross-linking will also occur between the molecular chains, which will also have an adverse effect on the sealing effect of the polymer microspheres. Preferably, in step (1), the mixing temperature is 16~22℃ when mixing.

[0047] (2) Mix the base oil and emulsifier to obtain an oil phase solution;

[0048] (3) The aqueous solution is added to the oil solution and stirred and emulsified to obtain a reverse emulsion; In this invention, preferably, the stirring speed of the emulsification is 300~500 r / min (for example, it can be 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min), and the stirring time of the emulsification is 30~60 min (for example, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min); It should be noted that the stirring speed of each component in step (1) and step (2) of this invention and the stirring speed of the polymerization reaction in step (4) can also be the above-mentioned speed; (4) The reverse emulsion is subjected to polymerization reaction under the action of an initiator to obtain the water-blocking profile control agent; In this invention, Preferably, after initiating the polymerization reaction in step (4), the step of adding a phase inversion agent to obtain the water-blocking and profile control agent is also included; in this invention, the polymerization reaction is carried out in an inert atmosphere, which is nitrogen and / or argon; preferably, the reverse emulsion obtained in step (3) is purged with nitrogen to remove oxygen for 20-40 minutes before initiating the polymerization reaction; the initiation temperature of the polymerization reaction is 22-23°C. After initiating the polymerization reaction at 22-23°C, the temperature of the reaction system will naturally rise to the peak temperature. After the temperature of the reaction system remains unchanged, it is considered that the reaction is over; in order to ensure that the reaction is more complete, after the reaction is over, for example, it can continue to be kept at this temperature for 4 hours, and then it is cooled to room temperature (e.g., 15-35°C) and then the phase inversion agent is added and stirred for more than 45 minutes to ensure that the phase inversion agent plays a full role, so that a stable water-blocking and profile control agent can be obtained.

[0049] According to some preferred embodiments, in step (4), the initiator comprises an azo initiator and a redox initiator (composed of an oxidant and a reductant), wherein the azo initiator is a water-soluble azo initiator and an oil-soluble azo initiator; the oil-soluble azo initiator is added to the oil phase solution obtained in step (2), and the water-soluble azo initiator and the oxidant in the redox initiator are added to the aqueous phase solution obtained in step (1); the reductant in the redox initiator is added to the solution obtained in step (3). The reducing agent is added dropwise to the obtained reverse emulsion in the form of an aqueous solution of the reducing agent, wherein the mass concentration (mass fraction) of the aqueous solution of the reducing agent is 1-5% (e.g., 1%, 2%, 3%, 4% or 5%), and the dropwise flow rate is 5-10 mL / h (e.g., 5 mL / h, 6 mL / h, 7 mL / h, 8 mL / h, 9 mL / h or 10 mL / h); the mass ratio of the reducing agent to the oxidizing agent is (0.8-1.2):1.

[0050] According to some preferred embodiments, in step (1), a metal complexing agent and / or a molecular weight regulator are also added to the aqueous solution, preferably adjusting the pH of the aqueous solution to 6.0~6.2.

[0051] According to some preferred embodiments, in step (4), after initiating the polymerization reaction, a phase inversion agent is added to obtain the water-blocking profile control agent.

[0052] In a third aspect, the present invention provides a water-blocking and profile control agent prepared by the preparation method described in the second aspect of the present invention.

[0053] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0054] In Examples 1-5 and Comparative Examples 1 and 4 of the present invention, the modified tannic acid was prepared as follows: 2g of tannic acid and 0.2g of triphenylphosphine catalyst (TPP) were added to a 100mL three-necked flask and dissolved in 9g of DMF (N,N-dimethylformamide). The mixture was mechanically stirred and heated to 95°C. 0.5g of glycidyl methacrylate was added dropwise to the mixture. After the epoxy value of the system reached a stable state, the mixture was purified to obtain modified tannic acid.

[0055] In Examples 1-5 and Comparative Examples 2-4 of the present invention, the preparation of the 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes was as follows: 100 mg of single-walled carbon nanotubes (SWCNTs) were added to 60 mL of concentrated nitric acid and refluxed at 90 °C for 6 h to obtain an acid-treated carbon nanotube dispersion (an acid-treated SWCNT dispersion); the acid-treated SWCNT dispersion was washed with deionized water until pH=7, then filtered and dried to obtain pretreated carbon nanotubes; then 20 g of glacial acetic acid, 3 g of pretreated carbon nanotubes, and 12 g of 3-(methacryloyloxy)propyltrimethoxysilane were sequentially added to 100 g of water, and the mixture was vigorously shaken at 75 °C for 30 min, then filtered and dried to obtain 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes.

[0056] Example 1

[0057] ① At 20℃, combine 100g acrylamide, 20g anionic monomer (sodium α-allyl sulfonate), 20g cationic monomer (octadecyltrimethylbenzylallylammonium bromide), 17g heat-resistant and salt-resistant monomer (15g sodium 3-acrylamido-3-methylbutyrate and 2g N-vinylpyrrolidone), 1g crosslinking agent (N,N-methylenebisacrylamide), and 0.8g... 3-(methacryloyloxy)propyltrimethoxysilane-modified carbon nanotubes, 3g of reinforcing agent (polyvinyl alcohol), and 1.5g of modified tannic acid were added to 150g of deionized water and stirred at 350r / min to obtain a mixed solution. The pH of the mixed solution was adjusted to 6.1. 0.5g of metal complexing agent (disodium ethylenediaminetetraacetate), 0.5g of molecular weight regulator (isopropanol), 0.02g of water-soluble azo initiator (azobisisobutyramidine hydrochloride), and 0.01g of oxidant (sodium persulfate) were added to the above mixed solution and stirred at 350r / min to obtain an aqueous solution.

[0058] ② Add 330g of base oil (white oil) to a three-necked flask equipped with a thermometer, stirrer and nitrogen gas tube. Add 125g of emulsifier (60g of Span 80, 60g of Tween 80, 5g of OP-10) and 1g of oil-soluble azo initiator (azobisisobutyronitrile) to the base oil and stir at 350r / min to obtain an oil phase solution.

[0059] ③ At a speed of 350 r / min, the aqueous phase solution is slowly added to the oil phase solution. After stirring and emulsifying for 40 min, a clear, pale yellow liquid is obtained, which is the reverse emulsion.

[0060] ④ Purge the reverse emulsion with nitrogen for 30 min to remove oxygen, and control the temperature at 22℃. Add a 3% (w / w) reducing agent aqueous solution (sodium sulfite aqueous solution, total sodium sulfite amount is 0.01 g) dropwise to the reverse emulsion system at a rate of 8 mL / h. The temperature of the reaction system is continuously increased until the temperature of the reaction system remains basically constant, and the system is kept at this peak temperature for 4 h. After the system is cooled to room temperature (25℃), add 15 g of phase inversion agent (nonylphenol polyoxyethylene ether) and stir for 45 min to obtain the water-blocking profile control agent.

[0061] Example 2

[0062] ① At 16℃, 120g of acrylamide, 15g of anionic monomer (allylbenzenesulfonic acid), 18g of cationic monomer (octadecyltrimethylbenzylallylammonium bromide), 19.8g of temperature- and salt-resistant monomer (18g of 2-acrylamido-2-methylpropanesulfonic acid and 1.8g of N-vinylpyrrolidone), 1g of crosslinking agent (N,N-methylenebisacrylamide), and 0.6g of... 3-(methacryloyloxy)propyltrimethoxysilane-modified carbon nanotubes, 5g of reinforcing agent (polyvinyl alcohol), and 3.5g of modified tannic acid were added to 170g of deionized water and stirred at 350r / min to obtain a mixed solution. The pH of the mixed solution was adjusted to 6.0. 0.5g of metal complexing agent (sodium alginate), 0.5g of molecular weight regulator (tert-butanol), 0.02g of water-soluble azo initiator (azobisisobutyrazoline hydrochloride), and 0.1g of oxidant (hydrogen peroxide) were added to the above mixed solution and stirred at 400r / min to obtain an aqueous solution.

[0063] ② Add 330g of base oil (kerosene) to a three-necked flask equipped with a thermometer, stirrer and nitrogen gas tube. Then add 125g of emulsifier (60g of Span 80, 60g of Tween 80 and 5g of OP-10) and 1g of oil-soluble azo initiator (azobisisobutyronitrile) to the base oil in sequence and stir at 350r / min to obtain an oil phase solution.

[0064] ③ At a speed of 300 r / min, the aqueous phase solution is slowly added to the oil phase solution. After stirring and emulsifying for 60 min, a clear, pale yellow liquid is obtained, which is the reverse emulsion.

[0065] ④ Purge nitrogen gas into the reverse emulsion for 30 min, control the temperature at 22.5℃, and add a 1% (w / w) reducing agent aqueous solution (ascorbic acid aqueous solution, total ascorbic acid amount is 0.1g) dropwise to the reverse emulsion system at a rate of 5mL / h. The temperature of the reaction system is continuously increased until the temperature of the reaction system remains basically constant, and the system is kept at this peak temperature for 4h. After the system is cooled to room temperature (25℃), 15g of phase inversion agent (nonylphenol polyoxyethylene ether) is added and stirred for 45min to obtain the water-blocking profile control agent.

[0066] Example 3

[0067] ① At 22℃, combine 100g acrylamide, 25g anionic monomer (sodium α-allyl sulfonate), 25g cationic monomer (acryloyloxyethyl dimethyl benzyl ammonium chloride), 27g heat-resistant and salt-resistant monomer (12g 2-acrylamido-2-methylpropanesulfonic acid and 15g 4-vinylpyridine), 1.2g crosslinking agent (N,N-methylenebisacrylamide), and 0.8g... 3-(methacryloyloxy)propyltrimethoxysilane-modified carbon nanotubes, 8g of reinforcing agent (polyvinyl alcohol), and 2.5g of modified tannic acid were added to 200g of deionized water and stirred at 500r / min to obtain a mixed solution. The pH of the mixed solution was adjusted to 6.2. 0.5g of metal complexing agent (diethyltriaminepentaacetic acid), 0.5g of molecular weight regulator (sodium formate), 0.02g of water-soluble azo initiator (azobisisobutyramidine hydrochloride), and 0.1g of oxidant (sodium persulfate) were added to the above mixed solution and stirred at 450r / min to obtain an aqueous solution.

[0068] ② Add 330g of base oil (white oil) to a three-necked flask equipped with a thermometer, stirrer and nitrogen gas tube. Then add 125g of emulsifier (60g of Span 80, 60g of Tween 80 and 5g of OP-10) and 1g of oil-soluble azo initiator (azobisisobutyronitrile) to the base oil in sequence and stir at 450r / min to obtain an oil phase solution.

[0069] ③ At a speed of 500 r / min, the aqueous phase solution is slowly added to the oil phase solution. After stirring and emulsifying for 30 min, a clear, pale yellow liquid is obtained, which is the reverse emulsion.

[0070] ④ Purge nitrogen gas into the reverse emulsion for 30 min, control the temperature at 23℃, and add a 1% (w / w) reducing agent aqueous solution (sodium sulfite aqueous solution, total sodium sulfite amount 0.1g) dropwise to the reverse emulsion system at a rate of 10mL / h. The temperature of the reaction system is continuously increased until the temperature of the reaction system remains basically constant, and the system is kept at this peak temperature for 4h. After the system is cooled to room temperature (25℃), 15g of phase inversion agent (nonylphenol polyoxyethylene ether) is added and stirred for 45min to obtain the water-blocking profile control agent.

[0071] Example 4

[0072] Example 4 is basically the same as Example 1, except that:

[0073] The reinforcing agent used in this embodiment is polyvinyl alcohol-grafted polyacrylamide. The preparation of the polyvinyl alcohol-grafted polyacrylamide is as follows: polyvinyl alcohol is added to deionized water and heated to dissolve it in the deionized water (dissolving at 80°C), preparing a 4% (w / w) polyvinyl alcohol aqueous solution. Then, acrylamide monomer, N,N-methylenebisacrylamide crosslinking agent, functional monomer, co-solvent, and surfactant are added to the polyvinyl alcohol aqueous solution and mixed to obtain a mixed system. The temperature and pH of the mixed system are then adjusted to 5°C and 7.1, respectively. After purging with nitrogen for 40 minutes to remove oxygen, ammonium persulfate initiator is added under nitrogen protection, and the reaction is maintained at 80°C for 2 hours. The product is then removed from the solution, washed, and dried to constant weight to obtain the polyvinyl alcohol-grafted polyacrylamide. The compound is a polyacrylamide; wherein the functional monomer is formed by reacting N-vinylimidazole with epichlorohydrin; the preparation of the functional monomer is as follows: N-vinylimidazole and epichlorohydrin are thoroughly mixed at a mass ratio of 1:1, stirred and refluxed under nitrogen for 24 hours, washed with diethyl ether and vacuum dried for 6 hours to obtain the functional monomer; the co-solvent is nonylphenol polyoxyethylene ether, the surfactant is sodium dodecylbenzenesulfonate, the amount of acrylamide monomer is 1 times the mass of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution, and the mass ratio of acrylamide monomer, N,N-methylenebisacrylamide, the functional monomer, the co-solvent, the surfactant, and the initiator is 10:0.25:3:0.02:0.02:0.002.

[0074] Example 5

[0075] Example 5 is basically the same as Example 1, except that:

[0076] The reinforcing agent used in this embodiment is polyvinyl alcohol-grafted polyacrylamide. The preparation of the polyvinyl alcohol-grafted polyacrylamide is as follows: polyvinyl alcohol is added to deionized water and heated to dissolve the polyvinyl alcohol in the deionized water (dissolved by heating at 80°C) to prepare a polyvinyl alcohol aqueous solution with a mass fraction of 4%. Then, acrylamide monomer and N,N-methylenebisacrylamide crosslinking agent are added to the polyvinyl alcohol aqueous solution and mixed to obtain a mixed system. Then, the temperature and pH of the mixed system are adjusted to 5°C and 7.1, respectively. After purging with nitrogen for 40 min, ammonium persulfate initiator is added under nitrogen protection, and the reaction is kept at 80°C for 2 h. Then, the product is taken out of the solution, washed, and dried to constant weight to obtain polyvinyl alcohol-grafted polyacrylamide. The amount of acrylamide monomer used is 1 times the mass of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution, and the mass ratio of acrylamide monomer, N,N-methylenebisacrylamide, and initiator is 10:0.25:0.002.

[0077] Comparative Example 1

[0078] Comparative Example 1 is basically the same as Example 1, except that:

[0079] In this comparative example, 3-(methacryloyloxy)propyltrimethoxysilane surface-modified silicon nitride nanoparticles were used to replace 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes in the experiment. The preparation of the 3-(methacryloyloxy)propyltrimethoxysilane surface-modified silicon nitride nanoparticles was as follows: 20g of glacial acetic acid, 3g of silicon nitride nanoparticles and 12g of 3-(methacryloyloxy)propyltrimethoxysilane were added sequentially to 100g of water, and the mixture was vigorously shaken at 75°C for 30min, then filtered and dried to obtain 3-(methacryloyloxy)propyltrimethoxysilane surface-modified silicon nitride nanoparticles.

[0080] Comparative Example 2

[0081] Comparative Example 2 is basically the same as Example 1, except that:

[0082] In this comparative example, no modified tannic acid was added during the preparation of the water-blocking and profile control agent.

[0083] Comparative Example 3

[0084] Comparative Example 3 is basically the same as Example 1, except that:

[0085] In this comparative example, tannic acid was used to replace modified tannic acid in the experiment.

[0086] Comparative Example 4

[0087] Comparative Example 4 is basically the same as Example 1, except that:

[0088] In this comparative example, no reinforcing agent (polyvinyl alcohol) was added during the preparation of the water-blocking and profile control agent.

[0089] The performance of the water-blocking and profile control agents prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was tested. The specific test methods are as follows, and the test results are shown in Tables 1 and 2:

[0090] (1) Initial particle size test: 0.1g of the water-blocking and profile control agent (hereinafter referred to as sample) in the examples and comparative examples was added to 100mL of n-hexane, and the sample was dispersed evenly by ultrasonic vibration for 30min. Then, the initial particle size was directly tested by dynamic light scattering instrument. The results are shown in Table 1.

[0091] Water absorption particle size test: 1.0 g of sample was added to 1000 mL of deionized water at a stirring speed of 200 r / min. After stirring at a constant speed for 5 min, the sample was allowed to stand at 25 ℃ for 7 days. Then, the particle size after water absorption was directly tested using a dynamic light scattering instrument. The results are shown in Table 1.

[0092] Expansion ratio = water-absorbing particle size / initial particle size;

[0093] (2) Temperature and salt resistance test: 1.0 g of sample was added to 1000 mL of mineralized water with a mineralization of 100000 mg / L at a stirring speed of 200 r / min. After stirring at a constant speed for 5 min, the sample was allowed to stand at 180℃ for 7 days. After cooling to room temperature, the particle size was tested and recorded using a dynamic light scattering instrument. The results are shown in Table 1.

[0094] (3) Test method for residual resistance coefficient and plugging rate: First, saturate injection (injection rate 0.5 mL / min) of simulated water from Changqing Oilfield into the sand-filled pipe (3.8 cm × 3.0 cm) and measure the permeability K0 of the sand-filled pipe. Then, inject brine (simulated water from Changqing Oilfield) into the sand-filled pipe at a constant flow rate until the pressure readings at the inlet and outlet ends are completely stable. Record the pressure difference at this time as ΔP1. This pressure difference reflects the flow resistance of the brine in the sand-filled pipe before the chemical agent is injected. Switch the injection source to an input source containing plugging agent (polymer brine solution) and inject polymer brine solution (prepared with simulated water from Changqing Oilfield, polymer concentration 0.3 wt%) into the sand-filled pipe at the same input flow rate. During this process, the pressure difference will rise sharply. Record the change and then measure the permeability K1 of the sand-filled pipe after the polymer microspheres are injected. After the pressure differential stabilizes, switch the input source back to brine and continue the above steps for water drive, continuously injecting brine. The pressure differential will gradually decrease from its high point, eventually reaching a new stable value, recorded as ΔP2. The purpose of this step is to wash out the flowable chemical agent, leaving only the portion that is adsorbed / retained / captured in the pore throat, causing permanent blockage. The pressure differential measured at this point reflects the residual resistance caused by the chemical agent. Calculate the residual resistance coefficient RRF and the plugging rate D.

[0095] The residual drag coefficient is calculated as follows:

[0096]

[0097] The blockage rate is calculated as follows:

[0098]

[0099] Tests were conducted under different PV conditions, including 1.0PV, 5.0PV, and 10.0PV, with injection volumes corresponding to 1, 5, and 10 times the pore volume of the sand-filled pipe, respectively. By adjusting the volume of injected chemical agent, the effects of the chemical agent on the residual resistance coefficient and plugging rate under different PV conditions were studied, and the results are shown in Table 2.

[0100] Table 1

[0101]

[0102] Table 2

[0103]

[0104] As shown in Tables 1 and 2, the water-blocking and profile control agent prepared in this invention has a regular spherical nanostructure. After absorbing water and swelling, the particle size increases, and the expansion ratio can reach 5.2~5.8, which can achieve a good sealing effect. Moreover, the water-blocking and profile control agent in this invention is zwitterionic, so its water absorption and swelling are not affected by salinity and temperature under certain salinity and temperature, and it has good temperature and salt resistance. Furthermore, the water-blocking and profile control agent in this invention has good sealing strength and migration toughness after absorbing water and swelling. The sealing efficiency at 1.0PV, 5.0PV and 10.0PV can reach more than 93.47%, more than 96.92% and more than 93.72%, respectively. The water-blocking and profile control agent in this invention can effectively overcome the problems of compression deformation and fragmentation during migration and insufficient sealing strength at the destination layer, and can achieve effective sealing of seepage channels and improve oil recovery.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-blocking and profile control agent, characterized in that: The water-blocking and profile control agent is prepared by reverse emulsion polymerization. The raw materials include an aqueous solution, an oil solution, and an initiator. The aqueous solution includes acrylamide, anionic monomers, cationic monomers, temperature-resistant and salt-resistant monomers, crosslinking agents, silane coupling agents modified carbon nanotubes, reinforcing agents, modified tannic acid, and water. The oil solution includes base oil and emulsifier. The anionic monomer is at least one of α-allylsulfonic acid, vinylsulfonic acid, vinylbenzenesulfonic acid, allylsulfonic acid, itaconic acid, or allylbenzenesulfonic acid. The cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, octadecyltrimethylbenzylallylammonium bromide, or dimethylethylallylammonium chloride; The temperature- and salt-resistant monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, sodium 3-acrylamido-3-methylbutyrate, p-styrenepropanesulfonic acid, or 4-vinylpyridine. The crosslinking agent is at least one of N,N-methylenebisacrylamide, N,N-methylenebismethylacrylamide or N,N'-m-phenylenebismaleimide; The silane coupling agent modified carbon nanotubes are 3-(methacryloyloxy)propyltrimethoxysilane surface-modified carbon nanotubes. The reinforcing agent is polyvinyl alcohol or polyvinyl alcohol-grafted polyacrylamide; The modified tannic acid is obtained by a ring-opening addition reaction of tannic acid and unsaturated glycidyl ester; The base oil is at least one of aliphatic hydrocarbons, aromatic hydrocarbons or alicyclic compounds, or the base oil is kerosene and / or white oil; The emulsifier includes Span, Tween, and alkylphenol polyoxyethylene ether; The aqueous solution comprises the following components by weight: 100-150 parts acrylamide, 15-25 parts anionic monomer, 18-25 parts cationic monomer, 15-30 parts temperature- and salt-resistant monomer, 1-2 parts crosslinking agent, 0.005-0.85 parts silane coupling agent modified carbon nanotubes, 0.5-12 parts reinforcing agent, 0.2-15 parts modified tannic acid, and 150-200 parts water. The oil phase solution contains the following components in parts by weight: 325-335 parts base oil and 122-128 parts emulsifier.

2. The water-blocking and profile control agent according to claim 1, characterized in that: The unsaturated glycidyl ester is glycidyl methacrylate.

3. The water-blocking and profile control agent according to claim 1, characterized in that: The molar ratio of the unsaturated glycidyl ester to the tannic acid is (3~5):

1.

4. The water-blocking and profile control agent according to claim 1, characterized in that: The initiator includes azo initiators and redox initiators.

5. The water-blocking and profile control agent according to claim 4, characterized in that: The azo initiator is a water-soluble azo initiator and / or an oil-soluble azo initiator.

6. The water-blocking and profile control agent according to claim 4, characterized in that: The mass ratio of the azo initiator, the oxidant in the redox initiator, and the acrylamide is (1.01~1.02):(0.01~0.12):(100~150).

7. The water-blocking and profile control agent according to claim 1, characterized in that: The aqueous solution further comprises a metal complexing agent and a molecular weight regulator, and / or the raw materials for preparation further comprise a phase inversion agent.

8. The water-blocking and profile control agent according to claim 7, characterized in that: The metal complexing agent is at least one of disodium ethylenediaminetetraacetate, sodium alginate, or diethyltriaminepentaacetic acid, and the molecular weight regulator is at least one of isopropanol, isobutanol, tert-butanol, pentaerythritol, thiol, sodium metaphosphate, or sodium formate.

9. The water-blocking and profile control agent according to claim 7, characterized in that: The mass ratio of the metal complexing agent, the molecular weight regulator, and the acrylamide is (0.3~2):(0.3~2):(100~150).

10. The water-blocking and profile control agent according to claim 7, characterized in that: The phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, or octylphenol polyoxyethylene ether.

11. The water-blocking and profile control agent according to claim 7, characterized in that: The mass ratio of the phase-transforming agent to the acrylamide is (10~20):(100~150).

12. A method for preparing the water shutoff profile control agent according to any one of claims 1 to 11, characterized in that, The preparation method includes the following steps: (1) Acrylamide, anionic monomer, cationic monomer, temperature-resistant and salt-resistant monomer, crosslinking agent, silane coupling agent modified carbon nanotube, reinforcing agent and modified tannic acid are added to water and mixed to obtain an aqueous solution; (2) Mix the base oil and emulsifier to obtain an oil phase solution; (3) The aqueous solution is added to the oil solution and stirred to emulsify, thereby obtaining a reverse emulsion; (4) The reverse emulsion is subjected to polymerization reaction under the action of an initiator to obtain the water-blocking profile control agent.

13. The preparation method according to claim 12, characterized in that: In step (1), a metal complexing agent and a molecular weight regulator are also added to the aqueous solution; In step (1), the pH of the aqueous solution is adjusted to 6.0~6.2; and / or In step (4), after initiating the polymerization reaction, a phase inversion agent is added to obtain the water-blocking profile control agent.

14. A water-blocking and profile control agent prepared by the preparation method according to claim 12 or 13.

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