Worm-like supramolecular associated micelle, hydrophobic associated copolymer and preparation method of wormlike supramolecular associated micelle and hydrophobic associated copolymer

Abstract

The present invention relates to the technical field of oilfield chemistry, and provides a wormlike supramolecular associated micelle, a hydrophobic associated copolymer and a preparation method thereof, the wormlike supramolecular associated micelle comprises a soft template, a hydrophobic functional monomer 1, a hydrophobic functional monomer 2 and a polarity regulator, the soft template is a long-chain molecular polymer and has an active functional group, and the polarity regulator is a hydrophobic functional monomer 2. The hydrophobic functional monomer 1 is an anionic-nonionic surfactant with polymerizable double bonds, the hydrophobic functional monomer 2 is a cationic-nonionic surfactant with polymerizable double bonds, and the polarity regulator is a micromolecular organic compound. The problems of poor resistance reduction, sand carrying capacity and the like of the fracturing fluid in the construction process due to dissociation of a polymer molecular network structure and sudden reduction of rheological property and viscoelasticity are solved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, in particular to a worm-like supramolecular associated micelle, a hydrophobic associated copolymer and a preparation method thereof. Background Art

[0002] Hydrophobic associating polyacrylamide is widely used as a fracturing fluid thickener due to its excellent thickening performance, temperature resistance and salt resistance. Compared with conventional linear polyacrylamide, which thickens with high molecular weight and high concentration, hydrophobic associating polymers rely on the associative micelles between hydrophobic monomers to form a dynamic cross-linked network, which can achieve better fluid thickening and sand carrying performance. One of its important characteristics is that by adjusting the hydrophobic monomer structure, the thickening and rheological properties of the liquid can be optimized, thereby improving the efficiency of fracturing operations and saving material costs.

[0003] Existing studies believe that the larger the microdomain size of hydrophobic associating polymers, the more molecular chains they connect, the denser the cross-linked network they form, and the higher the viscoelasticity and structural strength they show in the macroscopic form. However, the existing technology mainly relies on a single hydrophobic effect to design hydrophobic monomers, and the constructed microdomain system still has obvious shortcomings: (1) Poor morphological stability: Under high temperature or high salt environment, the hydrophobic microdomains rupture due to increased thermal motion or compression of the solvation layer, resulting in the disintegration of the cross-linked network and a sharp drop in viscoelasticity; (2) Imbalance in performance regulation: Although increasing the microdomain size can improve the initial thickening ability, it will sacrifice dynamic reversibility (too high dissociation barrier), reduce fluid shear thinning, and even cause the polymer chains to fail to fully stretch in water, resulting in poor thickening ability; (3) "Shielding effect" of salt ions: The hydrophobic associative effect is further amplified in a high mineralization environment, causing the hydrophobic microdomains to over-aggregate due to electrostatic shielding. This disordered aggregation will destroy the dynamic balance of the microdomains, reduce the network uniformity, and aggravate the dissociation of the network structure.

[0004] Through the synergistic effect of multiple supramolecular forces (such as hydrogen bonding, π-π stacking, and ion-dipole effects), larger-scale and more stable hydrophobic associating micelles can be constructed, further forming a polymer network structure with both topological entanglement and "quasi-covalent bond" stability. The Chinese invention patent with patent number CN107474817A proposes a supramolecular self-assembly fracturing fluid, which uses worm-like micelles formed by viscoelastic surfactants and supramolecular polymer hydrophobic side chains to self-assemble and enhance the polymer associating network, but the worm-like micelles are separate components and do not involve copolymerization of micelles and polymers. The constructed supramolecular associating polymer does not regulate the morphology of the hydrophobic associating micelles. There is no technology in the prior art to achieve the copolymerization of worm-like micelles formed by polymerizable monomers with acrylamide monomers, making it difficult to achieve the best use effect and having certain disadvantages. Summary of the invention

[0005] The first object of the present invention is to provide a method for preparing worm-like supramolecular associated micelles, which uses a polarity regulator to control the intermolecular interaction energy and enables the assembly behavior to form spontaneously.

[0006] The second object of the present invention is to provide a worm-like supramolecular associated micelle, which uses the soft template method and supramolecular forces such as electrostatic force, hydrogen bond force, hydrophobic force and stacking action of rigid rings between molecules to enable the polymerizable hydrophobic monomer to self-assemble into a stable worm-like associated micelle.

[0007] The third object of the present invention is to provide a method for preparing a hydrophobic associating copolymer based on worm-like supramolecular associated micelles, and a thickening agent for a fracturing fluid of a hydrophobic associating copolymer constructed based on worm-like supramolecular associated micelles, so as to solve the problem that when a fracturing fluid using a hydrophobic associating polymer as a thickening agent is under high temperature and high salt conditions, the molecular network structure of the polymer dissociates, and the rheology and viscoelasticity drop suddenly, resulting in insufficient drag reduction and sand-carrying capacity of the fracturing fluid during the construction process. The fourth object of the present invention is to provide a hydrophobic associating copolymer based on worm-like supramolecular associated micelles. In the prior art, in order to enhance the associating strength of the polymer, technical means such as increasing the size of the associated micelle, surfactant synergistically enhancing the aggregation of the hydrophobic associating structure, and worm-like micelles enhancing the connection of hydrophobic microdomains between polymer chains are adopted. To achieve better use effects, the morphology and size of the associated micelle are regulated to obtain a worm-like associated micelle, which is beneficial to the formation of a polymer containing a worm-like hydrophobic associating structure during the synthesis stage of the polymer.

[0008] To solve the above technical problems, the technical solution adopted in the present application is as follows: In the first aspect, an embodiment of the present application provides a method for preparing worm-like supramolecular associated micelles, including the following steps: S1. By mass, 0.1-0.8 parts of a soft template and 0.2-5 parts of a polarity regulator are mixed and added to 80-100 parts of ultrapure water, and stirred to obtain a homogeneous solution; S2. The hydrophobic functional monomer 1 and the hydrophobic functional monomer 2 are mixed in a mass ratio of x∶(1 - x), where the mixing parameter x satisfies 0 < x < 1, to obtain a mixture; S3. 0.1-10 parts of the mixture are added to the homogeneous solution, and stirred at a constant temperature of 25-90 °C for 2-4 h to obtain worm-like supramolecular associated micelles.

[0009] In the present application, the main solvent environment for the self-assembly behavior of the hydrophobic functional monomer and the soft template is water, and by adding a certain amount of polarity regulator, the molecular chain of the soft template is stretched and the self-assembly behavior between molecules is promoted.

[0010] Based on the principle of supramolecular forces, this application proposes a method for constructing worm-like hydrophobic associative micelles by using two hydrophobic functional monomers relying on a soft template. That is, in the solution phase, with a long-chain soft template as the "core", the hydrophobic functional monomers self-assemble and adsorb on the outer layer of the template through supramolecular forces to form a "shell". At the same time, the hydrophobic functional monomers also closely arrange on the soft template through supramolecular forces, thereby forming a more stable "shell".

[0011] In some embodiments of the present invention, the above-mentioned soft template is a type of polymer with a certain molecular chain length, which has reactive functional groups and can produce supramolecular forces with hydrophobic functional monomers to cause a self-assembly effect.

[0012] In some embodiments of the present invention, the above-mentioned soft template is one or more of a single polymer of polyether, a multi-component copolymer, and a sequential block copolymer. Its monomers include, for example, ethylene oxide, propylene oxide, epichlorohydrin, butylene oxide, etc., and are not limited to other similar substances containing epoxy functional groups.

[0013] In some embodiments of the present invention, the above-mentioned soft template can be a single monomer polymer or a multi-component monomer copolymer containing benzene ring and heterocyclic functional groups. The monomers include, for example, N-vinylpyrrolidone, styrene, p-hydroxystyrene, and are not limited to other polymerizable monomer substances containing benzene ring or heterocyclic structures.

[0014] In some embodiments of the present invention, the above-mentioned soft template can be other polymers with reactive functional groups, including but not limited to long-chain substances such as polyethyleneimine, polyamino acid, polyacrylamide, or quaternary ammonium salt cationic surfactants.

[0015] In some embodiments of the present invention, for better use effects, the above-mentioned different types of soft templates can be compounded and used in different proportions by two or more substances.

[0016] In some embodiments of the present invention, the above-mentioned polarity regulators include but are not limited to alkyl alcohols, alcohol ethers, water-soluble organic salts, and small molecule surfactants.

[0017] In some embodiments of the present invention, the above-mentioned alkyl alcohols include but are not limited to ethanol, n-propanol, glycerol, etc.

[0018] In some embodiments of the present invention, the above-mentioned alcohol ethers include but are not limited to diethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, etc.

[0019] In some embodiments of the present invention, the above-mentioned water-soluble organic salts include but are not limited to sodium salicylate, sodium benzoate, sodium citrate, etc.

[0020] In some embodiments of the present invention, the above-mentioned small molecule surfactants include, but are not limited to, sodium dodecyl sulfate, dodecyl hydroxypropyl betaine, dodecyl amine oxide, etc.

[0021] In some embodiments of the present invention, through the combination of the above substances, under further regulation, a worm-like supramolecular hydrophobic association micelle formed by self-assembly relying on a soft template can be constructed.

[0022] In some embodiments of the present invention, the above-mentioned hydrophobic functional monomer 1 is an anionic-nonionic surfactant having a polymerizable double bond, and its structural formula is shown in Formula 1: Formula 1, In Formula 1, R 1 is at least one of -COO - -, -SO 3 - -, -SO 4 - -, -PO 4 - ; R 2 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; n is 2-16.

[0023] In some embodiments of the present invention, the above-mentioned hydrophobic functional monomer 2 is a cationic-nonionic surfactant having a polymerizable double bond, and its structural formula is shown in Formula 2: Formula 2, In Formula 2, R 3 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; m is 10-16.

[0024] Second, the embodiments of the present application provide a worm-like supramolecular association micelle, which is composed of a soft template, a hydrophobic functional monomer 1, a hydrophobic functional monomer 2 and a polarity regulator. The soft template is a long-chain molecular polymer and has active functional groups. The hydrophobic functional monomer 1 is an anionic-nonionic surfactant having a polymerizable double bond, and the hydrophobic functional monomer 2 is a cationic-nonionic surfactant having a polymerizable double bond. The polarity regulator is a small molecule organic compound. It takes the long-chain soft template as the "core", and the hydrophobic functional monomers are self-assembled and adsorbed on the outer layer of the template through supramolecular forces to form a "shell". At the same time, the hydrophobic functional monomers are also closely arranged on the soft template through supramolecular forces, thereby forming a more stable "shell" and promoting its self-assembly behavior.

[0025] Third aspect, an embodiment of the present application provides a preparation method of a hydrophobically associating copolymer based on worm-like supramolecular associated micelles, including the following steps: I. Prepare an aqueous solution of acrylamide, sodium acrylate, and 2-acrylamido-2-methylpropanesulfonic acid with a fixed mass number to obtain a monomer solution; II. Add the worm-like supramolecular associated micelles to the monomer solution, fix the mass ratio of the total monomers to water at 30:70, add a molecular weight regulator accounting for 0.002-0.03% of the total monomer mass, add a first-stage initiator accounting for 0.02-0.05% of the total monomer mass, add a second-stage initiator accounting for 0.05-0.08% of the total monomer mass, control the reaction temperature not to exceed 90 °C during the reaction process, which is more conducive to maintaining the stability of the worm micelles, keep warm and stand still for 2-4 h until the reaction is completed to obtain a copolymer block, and the copolymer block is the copolymer.

[0026] In some embodiments of the present invention, the above-mentioned molecular weight regulator includes but is not limited to sodium formate, sodium acetate, isopropyl alcohol, sodium hypophosphite, and urea, etc.

[0027] In some embodiments of the present invention, the above-mentioned first-stage initiator includes sodium formaldehyde sulfoxylate and ammonium persulfate, and the second-stage initiator is azobisisobutyronitrile.

[0028] In some embodiments of the present invention, at the beginning of the polymerization reaction, to ensure that the worm micelles in the reaction process are not damaged by thermodynamic factors, the reaction process should be kept stable, and rapid heat release caused by too fast reaction should be avoided, and the highest temperature inside the product should be controlled not to exceed 90 °C.

[0029] Fourth aspect, an embodiment of the present application provides a hydrophobically associating copolymer based on worm-like supramolecular associated micelles. The copolymer is composed of acrylamide, sodium acrylate, 2-acrylamido-2-methylpropanesulfonate, hydrophobic functional monomer 1, and hydrophobic functional monomer 2, and its structural formula is as shown in Formula 3: Formula 3 In Formula 3, R 1 is at least one of -COO - -, -SO 3 - -, -SO 4 - -, -PO 4 - ; R 2 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine, and corresponding heterocyclic derivatives; R 3is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; m is 10 - 16; n is 2 - 16; for each monomer by mass number, a is 24000 - 36000; b is 4200 - 8400; c satisfies 0 < c ≤ 4200; d satisfies 0 < d ≤ 1800; e satisfies 0 < e ≤ 1800.

[0030] In some embodiments of the present invention, the weight - average molecular weight of the above - mentioned copolymer is 3×10 6 - 8×10 6 .

[0031] In some embodiments of the present invention, after granulating, drying and pulverizing the hydrophobic associating copolymer rubber block, a copolymer powder is obtained, and the copolymer powder is the thickening agent for the fracturing fluid.

[0032] The present application also provides a thickened fracturing fluid based on a worm - like supramolecular associating micelle copolymer. After mixing and stirring the thickening agent for the fracturing fluid and the solvent in proportion, a thickened fluid with obvious rheological properties and visco - elasticity can be obtained.

[0033] In some embodiments of the present invention, the above - mentioned solvent can be fresh water or brine with a salinity of 0 - 10 5 mg / L.

[0034] In some embodiments of the present invention, the cations contained in the above - mentioned brine include, but are not limited to, Na + , K + , Ca 2+ , Mg 2 + , Cu 2+ , Fe 2+ , Fe 3+ , Pb 2+ and Cr 2+ etc.

[0035] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: The present application uses a long - chain polymer as a soft template, and utilizes supramolecular forces to realize the self - assembly of hydrophobic functional monomers on the soft template to form stable worm - like micelles. Further, the polymerization of multiple monomers is completed in the aqueous phase to construct a polymer molecular network with a higher degree of associative cross - linking, so that the fracturing fluid macroscopically exhibits excellent rheological properties and visco - elasticity, and can still relatively completely maintain its original performance under extreme conditions such as high salt or high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0037] Figure 1 TEM characterization of the solution obtained in step S2 of Embodiment 1 of the present invention; Figure 2 Particle size characterization of different solutions of the embodiments of the present invention; Figure 3 SEM characterization of the fracturing fluid at a concentration of 0.2% in Embodiment 1 of the present invention; Figure 4 High-temperature rheological test chart of the fracturing fluid in Embodiment 1 of the present invention; Figure 5 Schematic diagram of the technical route of the embodiments of the present invention. Detailed implementation manners

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0039] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0040] Compared with the existing publicly disclosed technical solutions, the uniqueness of this application lies in: 1. This application proposes a micellar polymerization method for regulating the formation of worm-like micelles to synthesize a new type of hydrophobically associating polymer. The existing technology mainly uses small-scale spherical micelle copolymerization or does not regulate micelles for the aqueous-phase synthesis of hydrophobic monomers. Regulating the hydrophobic monomers into worm-like shapes is beneficial to the formation of a polymer network with a high degree of associative crosslinking.

[0041] 2. This application proposes a method for regulating soft-template worm-like micelles. To achieve the formation of worm-like micelles by surfactants in dilute solutions, this application proposes a method for constructing worm-like micelles with a polymer chain-type soft template, and at the same time, a solution polarity regulation method is supplemented to promote the combination between small molecules and macromolecules.

[0042] 3. This application adopts fine molecular structure design and specifically utilizes supramolecular forces such as ionic bonds, hydrogen bonds, hydrophobic interactions, and conjugated π bonds between soft template polymer chains, hydrophobic functional monomer 1, and hydrophobic functional monomer 2, achieving tight binding between hydrophobic functional monomers and between hydrophobic functional monomers and the template, providing thermodynamic and kinetic stability for worm-like micelles.

[0043] 4. This application proposes a thickening agent for fracturing fluid of a worm-like supramolecular associative micelle copolymer. Different from conventional hydrophobically associating polymers and the form of constructing worm-like micelles with surfactants and completing self-assembly with polymer solutions, this thickening agent innovatively incorporates worm-like micelles in the form of polymerizable hydrophobic microdomains into the polymer molecular chain, forming a hydrophobically associating polymer network with large-scale hydrophobic microdomains. The corresponding fracturing fluid exhibits excellent performance, being outstanding in thickening, sand carrying, temperature resistance, and salt tolerance.

[0044] As Figure 5 shown, based on the basic theoretical route concept of the present invention, a preparation method of a thickening agent for fracturing fluid of a worm-like supramolecular associative micelle copolymer is proposed, including the following steps: S1. Weigh a specified mass of the polymer soft template and the polarity regulator, mix and add them to a specified mass of clear water, and stir to form a homogeneous solution; S2. Weigh a specified mass of hydrophobic functional monomer 1 and hydrophobic functional monomer 2, add them to the homogeneous solution prepared in S1 above, and stir for 2 - 4 h to obtain a self-assembled worm-like micelle solution; S3. Add monomers such as acrylamide, sodium acrylate, and 2-acrylamido-2-methylpropanesulfonic acid sodium contained in the copolymer structure to the self-assembled worm-like micelle solution prepared in S2 according to the specified mass, and mix and dissolve to obtain a monomer solution; S4. Add a specified mass of molecular weight regulator and initiator to the monomer solution prepared in S3, carry out a heat preservation reaction, and after 2 - 4 hours, the reaction is completed to obtain a rubber block; S5. Granulate and dry the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water or salt water at a certain concentration to obtain the target fracturing fluid.

[0045] The features and properties of the present invention will be further described in detail below in conjunction with examples.

[0046] It should be noted that among the medicaments involved in these examples, hydrophobic functional monomer 1, hydrophobic functional monomer 2, and part of the soft template polymers constructed by monomer combination or ratio optimization are prepared by professional methods, and the rest are all conventional commercially available chemical raw materials.

[0047] Example 1 S1. Weigh 0.26 g of the soft template K30 polyvinylpyrrolidone and 3 g of the polar regulator diethylene glycol butyl ether, and add them to 30.9 g of clear water and stir to form a homogeneous solution; S2. Weigh 0.18 g of hydrophobic functional monomer 1 (N-ethylpyrrolidone laurate-N-ethylsulfonate-N-ethyl acrylate triethanolamine, as shown in Formula 4) and 0.13 g of hydrophobic functional monomer 2 (1-acrylamide-2-methylaminopyrrol dodecyl quaternary ammonium, as shown in Formula 5), and add them to the solution prepared in S1 above. After stirring for 3 h, a self-assembled worm-like micelle solution is obtained. Formula 4 and Formula 5 are as follows: Formula 4 Formula 5; S3. Add 10.3 g of acrylamide, 3.9 g of sodium acrylate, and 1.6 g of 2-acrylamido-2-methylpropanesulfonic acid monomer to the solution prepared in S2, and mix and dissolve to obtain a monomer solution; S4. Add 0.002 g of the molecular weight regulator sodium hypophosphite and 0.014 g of the initiator (the first stage: 0.006 g of ammonium persulfate, 0.003 g of sodium formaldehyde sulfoxylate; the second stage: 0.005 g of azobisisobutyronitrile) to the monomer mixed solution prepared in S3, control the temperature at 90 °C and react. After 3 h, the reaction is completed to obtain a rubber block; S5. Granulate, dry, and pulverize the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water to obtain the target fracturing fluid.

[0048] Example 2 S1. Weigh 0.18 g of the soft template K30 polyvinylpyrrolidone, 3 g of the polar regulator diethylene glycol butyl ether, and 1.2 g of sodium salicylate, and add them to 29.9 g of clear water and stir to form a homogeneous solution; S2. Weigh 0.3 g of hydrophobic functional monomer 1 (N-ethylpyrrolidone laurate-N-ethylsulfonate-N-ethyl acrylate triethanolamine, as shown in Formula 4), and add it to the solution prepared in S1 above. After stirring for 3 h, a self-assembled worm-like micelle solution is obtained. Formula 4 is as follows: Formula 4; S3. Add 10.3 g of acrylamide, 3.9 g of sodium acrylate, and 1.6 g of 2-acrylamido-2-methylpropanesulfonic acid monomer to the solution prepared in S2, and mix and dissolve to obtain a monomer solution; S4. Add 0.002 g of the molecular weight regulator sodium hypophosphite and 0.014 g of the initiator (the first stage: 0.006 g of ammonium persulfate, 0.003 g of sodium formaldehyde sulfoxylate; the second stage: 0.005 g of azobisisobutyronitrile) to the monomer mixed solution prepared in S3, control the temperature at 90 °C and react. After 3 h, the reaction is completed to obtain a rubber block; S5. Granulate, dry, and pulverize the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water to obtain the target fracturing fluid.

[0049] Example 3 S1. Weigh 0.22 g of the soft template polyvinylpyrrolidone-co-styrene (9 parts of vinylpyrrolidone and 1 part of styrene), 0.4 g of the polar regulator dodecyl hydroxypropyl betaine, and 1.5 g of sodium salicylate. Mix and add them to 32.0 g of clear water, and stir to form a homogeneous solution. S2. Weigh 0.3 g of the hydrophobic functional monomer 1 (N-ethylsulfonate-N-ethyl acrylate triethanolamine of N-phenylacetic acid ethyl ester, as shown in Formula 6), add it to the solution prepared in S1 above, and stir for 3 h to obtain a self-assembled worm-like micelle solution. Formula 6: Formula 6; S3. Add 10.3 g of acrylamide, 3.9 g of sodium acrylate, and 1.6 g of 2-acrylamido-2-methylpropanesulfonic acid monomer to the solution prepared in S2, and mix and dissolve to obtain a monomer solution. S4. Add 0.002 g of the molecular weight regulator sodium hypophosphite and 0.014 g of the initiator (first stage: 0.006 g of ammonium persulfate, 0.003 g of sodium formaldehyde sulfoxylate; second stage: 0.005 g of azobisisobutyronitrile) to the monomer mixed solution prepared in S3, control the temperature at 90 °C and react. After 3 h, the reaction is completed to obtain a rubber block. S5. Granulate, dry, and pulverize the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water to obtain the target fracturing fluid.

[0050] Example 4 This Example 4 is basically the same as Example 1, except that the polymer is dissolved in brine with a salinity of 10000 mg / L. By mass ratio, the salt ratio of each component is NaCl (2): KCl (5.5): CaCl 2 (0.55): MgCl 2 (0.45): FeCl 3 (0.1).

[0051] Comparative Example 1 In this Comparative Example 1, to reflect the superior effects brought by the measures for worm-like micelle regulation of the monomer, based on Example 1, only the monomers were simply mixed in the solution, and then polymerized to form a conventional hydrophobically associating polymer without micelle regulation. The following steps were set: S1. Add 0.18 g of hydrophobic functional monomer 1 (ethyl N - pyrrolyl laurate - N - ethylsulfonate - N - ethyl acrylate triethanolamine, as shown in Formula 4), 0.13 g of hydrophobic functional monomer 2 (1 - acrylamide - 2 - methylamine pyrrole dodecyl quaternary ammonium, as shown in Formula 5), 10.3 g of acrylamide, 3.9 g of sodium acrylate, and 1.6 g of 2 - acrylamido - 2 - methylpropanesulfonic acid sodium into 33.9 g of clear water. After mixing and dissolving, a monomer solution is obtained. Formula 4 and Formula 5 are as follows: Formula 4, Formula 5; S2. Add 0.002 g of molecular weight regulator sodium hypophosphite and 0.014 g of initiator (in the first stage: 0.006 g of ammonium persulfate, 0.003 g of sodium formaldehyde sulfoxylate; in the second stage: 0.005 g of azobisisobutyronitrile) to the monomer mixed solution prepared in S1, and carry out a heat - preservation reaction. After 3 hours, the reaction is completed to obtain a rubber block; S3. Granulate, dry, and crush the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water to obtain the target fracturing fluid.

[0052] Comparative Example 2 In this Comparative Example 2, in order to verify the effect of the supramolecular force between binary monomers on the formation of stable worm - like micelles, on the basis of Example 1, the structure of one of the functional monomers was changed so that multiple supramolecular forces could not be obtained. Further, a monomer micelle solution was prepared and a polymer was synthesized in the same method. The following steps were set: S1. Weigh 0.26 g of soft template K30 polyvinylpyrrolidone and 3 g of polar regulator diethylene glycol butyl ether, mix and add them into 30.9 g of clear water, and stir to form a homogeneous solution; S2. Weigh 0.18 g of cetyl dimethyl allyl ammonium chloride and 0.13 g of sodium styrenesulfonate, add them to the solution prepared in S1, and stir for 3 h to obtain a micelle solution; S3. Add 10.3 g of acrylamide, 3.9 g of sodium acrylate, and 1.6 g of 2 - acrylamido - 2 - methylpropanesulfonic acid sodium monomers to the solution prepared in S2, and mix and dissolve to obtain a monomer solution; S4. Add 0.002 g of molecular weight regulator sodium hypophosphite and 0.014 g of initiator (in the first stage: 0.006 g of ammonium persulfate, 0.003 g of sodium formaldehyde sulfoxylate; in the second stage: 0.005 g of azobisisobutyronitrile) to the monomer mixed solution prepared in S3, control the temperature at 90 °C for reaction. After 3 hours, the reaction is completed to obtain a rubber block; S5. Granulate, dry, and crush the rubber block to obtain a white powder, which is the target thickening agent. Dissolve it in clear water to obtain the target fracturing fluid.

[0053] Performance Test The solution obtained in step S2 of Example 1 was characterized by TEM, and the results are as Figure 1 shown. It can be observed that worm-like micelles with different lengths are present and exhibit an interlaced network form, indicating that the micelles are interlaced and distributed with the polymer as a template. The particle size distribution test results of the solution in step S3 of Example 1, the solution in step S3 of Example 2, and the solution in step S1 of Comparative Example 1 are as Figure 2 shown. The median particle size distribution of Example 1 and Example 2 is around 200 nm, with a relatively large scale, while the median particle size of the micelles in Comparative Example 1 is 30 nm, belonging to the scale of conventional spherical micelles.

[0054] The viscosities of the fracturing fluids obtained in each example and comparative example were tested using a HAAKE MARS Ⅲ rheometer. The proppant was mixed evenly with the fracturing fluid and allowed to stand still to observe the settlement of the proppant to judge the sand-carrying performance. The results are shown in Table 1: Table 1 Test results of fracturing fluid performance

[0055] As can be seen from Table 1, after polymerizing the hydrophobic functional monomer in the form of self-assembled worm-like associated micelles in Examples 1-3, the corresponding fracturing fluid obtained excellent thickening ability and at the same time had the sand-carrying ability that 40 / 70 mesh quartz sand did not settle within 2 hours at a concentration of 0.2%. Comparative Example 1 corresponded to a conventional hydrophobic associating polymer, and the particle size of its hydrophobic monomer micelles was much smaller than that of the self-assembled worm micelles ( Figure 2 ). Therefore, the zero-shear viscosity and apparent viscosity of the corresponding fracturing fluid at a concentration of 0.2% were also much lower than those of the fracturing fluid containing worm-like associated micelles. On the other hand, it can also be found that due to the presence of worm-like associated micelles, the fracturing fluid obtained in Example 1 presented a tight and stable network structure (as Figure 3 shown). However, the fracturing fluids in Comparative Example 1 and Comparative Example 2 without constructing a worm-like associated structure did not have such a tight network structure, resulting in the difficulty of the fracturing fluid to suspend the proppant and a rapid decline. The high-temperature rheological test of the fracturing fluid in Example 1 (as Figure 4 shown) was carried out. At a polymer concentration of 0.3%, the fracturing fluid was continuously sheared at 130 °C for 60 min, and its viscosity still remained at about 35 mPa·s, showing excellent temperature resistance.

[0056] A thickening agent for a fracturing fluid of a worm-like supramolecular associated micelle copolymer proposed in this application enables hydrophobic monomers to self-assemble and arrange on the soft template of the polymer chain to form worm-like micelles through supramolecular forces. The micelles can further polymerize with acrylamide monomers in the aqueous phase to form a hydrophobic associating polymer containing worm-like micelles. The fracturing fluid prepared from the polymer obtained in this way has a tight microstructure, thus possessing the ability to fully suspend sand-carrying and excellent temperature and salt resistance.

[0057] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing worm-like supramolecular associated micelles, characterized in that: The following steps are involved: S1. By mass, 0.1-0.8 parts of a soft template and 0.2-5 parts of a polarity regulator are mixed and added to 80-100 parts of ultrapure water, and stirred to obtain a homogeneous solution, wherein the soft template is a single polymer, a multi-polymer and a sequential block copolymer of a polyether; S2. The hydrophobic functional monomer 1 and the hydrophobic functional monomer 2 are mixed in a mass ratio of x: (1-x), wherein the mixing parameter x satisfies 0<x<1, to obtain a mixture, wherein the hydrophobic functional monomer 1 is an anionic nonionic surfactant having a polymerizable double bond, and the hydrophobic functional monomer 2 is a cationic nonionic surfactant having a polymerizable double bond; S3. Add 0.1-10 parts of the mixture to the homogeneous solution in step S1, and stir at a constant temperature of 25-90° C. for 2-4 hours to obtain worm-like supramolecular associated micelles.

2. The method for preparing a worm-like supramolecular associated micelle according to claim 1, characterized in that: The soft template is a single monomer polymer or a multi-monomer mixed polymer containing a benzene ring or a heterocyclic functional group.

3. The method for preparing a worm-like supramolecular associated micelle according to claim 1, characterized in that: The polarity regulator is one or more of alkyl alcohols, alcohol ethers, water-soluble organic salts and small molecule surfactants.

4. The method for preparing a worm-like supramolecular associated micelle according to claim 1, characterized in that: The structural formula of the hydrophobic functional monomer 1 is shown in Formula 1: Formula 1, In formula 1, R1 is -COO - 、-SO3 - 、-SO4 - ,-PO4 - At least one of; R2 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; n is 2-16.

5. The method for preparing a worm-like supramolecular associated micelle according to claim 1, characterized in that: The structural formula of the hydrophobic functional monomer 2 is shown in Formula 2: Formula 2, In Formula 2, R3 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; and m is 10-16.

6. A worm-like supramolecular associated micelle prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing a hydrophobic associating copolymer based on worm-like supramolecular associating micelles, characterized in that: The following steps are involved: I. preparing a fixed mass number of acrylamide, sodium acrylate, and 2-acrylamide-2-methylpropane sulfonic acid into an aqueous solution to obtain a monomer solution; II. Add the worm-like supramolecular associated micelles to the monomer solution, fix the mass ratio of the total monomer mass to water at 30:70, add 0.002-0.03% of the total monomer mass of a molecular weight regulator, add 0.02-0.05% of the total monomer mass of a first-stage initiator, add 0.05-0.08% of the total monomer mass of a second-stage initiator, control the reaction temperature to be no higher than 90°C, keep it warm and stand for 2-4 hours until the reaction is completed, and obtain a copolymer block, which is the hydrophobic associating copolymer.

8. The method for preparing a hydrophobic associating copolymer based on worm-like supramolecular associating micelles according to claim 7, characterized in that: The molecular weight regulator is one or more of sodium formate, sodium acetate, isopropyl alcohol, sodium hypophosphite and urea; the first-stage initiator includes sodium formaldehyde sulfoxylate and ammonium persulfate; and the second-stage initiator is azobisisobutyronitrile.

9. A hydrophobic associating copolymer of worm-like supramolecular associating micelles prepared by the preparation method according to any one of claims 7 to 8, characterized in that: The weight average molecular weight of the hydrophobically associating copolymer is 3×10 6 - 8×10 6 The hydrophobic associating copolymer molecule is composed of acrylamide, sodium acrylate, sodium 2-acrylamide-2-methylpropane sulfonate, the hydrophobic functional monomer 1 and the hydrophobic functional monomer 2, and its structural formula is shown in Formula 3: Formula 3, In formula 3, R1 is -COO - 、-SO3 - 、-SO4 - ,-PO4 - at least one of; R2 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; R3 is at least one of benzene, benzene derivatives, pyridine, pyrrole, pyrimidine and corresponding heterocyclic derivatives; m is 10-16; n is 2-16; each monomer is calculated by mass number, a is 24000-36000; b is 4200-8400; c satisfies 0<c≤4200; d satisfies 0<d≤1800; e satisfies 0<e≤1800.

Images