Self-permeating water-based profile control nanomaterial and preparation method therefor, and plugging method for reservoir fracture

Abstract

A self-permeating water-based profile control nanomaterial and a preparation method therefor, and a plugging method for a reservoir fracture. The self-permeating water-based profile control nanomaterial has a core-shell structure, wherein the shell is an amphiphilic mesoporous magnesium oxide nanosheet, and the core is a multi-component copolyester. The amphiphilic mesoporous magnesium oxide nanosheet has an asymmetric structure of which one surface is hydrophilic and the other surface is lipophilic. The particle size of the self-permeating water-based profile control nanomaterial is 100-550 nm, and the thickness of the amphiphilic mesoporous magnesium oxide nanosheet is 10-100 nm. The self-permeating water-based profile control nanomaterial provided by the present invention solves the problems of inter-well channeling caused by a fracture in a low-permeability reservoir, the inability to effectively circulate subsequent water injection, and a reduced recovery factor.

Description

A self-permeable water-absorbing nanomaterial for reservoir regulation and control, its preparation method, and a method for sealing reservoir fractures.

[0001] Cross-reference information

[0002] This application claims priority to Chinese Patent Application No. 202411908206.4, filed on December 23, 2024, entitled "A self-permeable water-absorbing nano-modulation and driving material and its preparation method and a method for sealing fractures in permeable reservoirs", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the field of low-permeability reservoir technology, specifically relating to a self-permeable water-absorbing nanomaterial for regulating and driving the reservoir, its preparation method, and a method for sealing reservoir fractures. Background Technology

[0004] In recent years, with the development of oil and gas exploration and development technologies, the application of profile control materials in the petroleum industry has gradually attracted attention. For example, CN118126256A discloses a profile control agent for low-permeability reservoirs and its preparation method. This method can prepare silicon-containing polymers with controllable molecular weight through the polymerization reaction of different monomers in organic solvents. CN115710330B discloses a method for preparing polymer microspheres / graphene oxide emulsions for profile control. By introducing GO, the sealing performance of polyacrylamide microsphere emulsions on pore throats is improved, and the emulsification ability of crude oil is enhanced to meet the requirements of deep profile control. CN117821042A discloses a multi-level expanded pre-crosslinked gel particle with controllable density for deep profile control and its preparation method. The strength of the pre-crosslinked gel particle is improved by toughening agents, and the density of the gel particle is controllable by controlling the amount of modified inorganic lightweight additives.

[0005] However, the modulators prepared by the above methods have problems such as unstable chemical properties. Therefore, it is urgent to study a nano-modulator material suitable for high-temperature, high-salinity, and low-permeability reservoirs. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a self-permeable water-absorbing nanomaterial for reservoir regulation and control, its preparation method, and a method for sealing reservoir fractures. By preparing a self-permeable water-absorbing nanomaterial with a core-shell structure, the material exhibits stable chemical properties and can fill fractures when used with permeate, achieving a good selective sealing effect and improving oil recovery.

[0007] To achieve the above objectives, the present invention provides a self-permeable water-absorbing nanomaterial for regulating and driving the flow of water. The self-permeable water-absorbing nanomaterial for regulating and driving the flow of water has a core-shell structure, wherein the shell is an amphiphilic mesoporous magnesium oxide nanosheet and the core is a multi-component copolyester; the amphiphilic mesoporous magnesium oxide nanosheet has an asymmetric structure with one side being hydrophilic and the other side being oleophilic.

[0008] The particle size of the self-permeable water-absorbing nanomaterial is 100-550 nm, and the thickness of the amphiphilic mesoporous magnesium oxide nanosheets is 10-100 nm.

[0009] According to a specific embodiment of the present invention, preferably, the viscosity of the self-permeable water-absorbing nanomaterial is 1.0-5.5 mPa·s.

[0010] According to a specific embodiment of the present invention, preferably, the specific surface area of ​​the self-permeable water-absorbing nanomaterial is 4-260 m². 2 / g.

[0011] According to a specific embodiment of the present invention, preferably, the molecular structural formula of the multi-component copolyester is as follows:

[0012] According to a specific embodiment of the present invention, preferably, the degree of polymerization of the multi-component copolyester is 50-250 and the molecular weight is 5000-30000.

[0013] According to a specific embodiment of the present invention, preferably, the multi-component copolyester is obtained by mixing an alcohol monomer, terephthalic acid, an initiator, and water to obtain a mixed solution, and then heating the mixed solution to induce an esterification reaction; in the mixed solution, based on the mass of the mixed solution as 100%, the amount of alcohol monomer added is 0.5wt%-2.5wt%, the amount of terephthalic acid added is 1wt%-2wt%, and the amount of initiator added is 0.1wt%-0.5wt%.

[0014] According to a specific embodiment of the present invention, preferably, the mixed solution further contains 0.4wt%-0.8wt% of an oil-in-water emulsifier; the preparation step of the multi-component copolyester further includes: mixing the amphiphilic mesoporous magnesium oxide nanosheet dispersion with the mixed solution, and under the action of the oil-in-water emulsifier, causing the esterification reaction to occur inside the amphiphilic mesoporous magnesium oxide nanosheets to form a multi-component copolyester core; more preferably, the volume ratio of the amphiphilic mesoporous magnesium oxide nanosheet dispersion to the mixed solution is (0.8-1.2):(0.8-1.5); in the amphiphilic mesoporous magnesium oxide nanosheet dispersion, the concentration of the amphiphilic mesoporous magnesium oxide nanosheets is 0.0001-0.0005 g / mL.

[0015] According to a specific embodiment of the present invention, preferably, the alcohol monomer includes one or more of triethylene glycol, ethylene glycol, vinyl alcohol, styrene alcohol, and 1,3-dienol; more preferably, the alcohol monomer is triethylene glycol and ethylene glycol, and the amount of triethylene glycol added is 0.5wt%-1.0wt% and the amount of ethylene glycol added is 0.5wt%-1.5wt% based on the mass of the mixed solution as 100%.

[0016] According to a specific embodiment of the present invention, preferably, the oil-in-water emulsifier includes one or more of sodium dodecyl sulfate, Span series surfactants, and Tween series surfactants.

[0017] According to a specific embodiment of the present invention, preferably, the esterification reaction temperature is 60-70°C and the esterification reaction time is 3-6 hours.

[0018] This invention also provides a method for preparing a self-permeable water-absorbing nanomaterial, wherein the preparation method includes:

[0019] (1) Add alcohol monomers, terephthalic acid, oil-in-water emulsifier and initiator to water and mix to obtain a mixed solution;

[0020] (2) The amphiphilic mesoporous magnesium oxide nanosheet dispersion is mixed with the mixed solution to obtain an emulsion; in the emulsion, the amphiphilic mesoporous magnesium oxide nanosheets are located on the surface of the emulsion droplets, while alcohol monomers, terephthalic acid, oil-in-water emulsifiers and initiators are coated in the core of the emulsion droplets;

[0021] (3) Heating causes the core to undergo an esterification reaction to form a multi-component copolyester; cooling after the reaction is complete yields a self-permeable water-absorbing nanomaterial with a core-shell structure; wherein the shell is an amphiphilic mesoporous magnesium oxide nanosheet and the core is a multi-component copolyester.

[0022] The amphiphilic mesoporous magnesium oxide nanosheets have an asymmetric structure with one side hydrophilic and the other side oleophilic; the concentration of the amphiphilic mesoporous magnesium oxide nanosheets in the dispersion is 0.0001-0.0005 g / mL; in the mixed solution, based on the mass of the mixed solution as 100%, the amount of alcohol monomer added is 0.5wt%-2.5wt%, the amount of terephthalic acid added is 1wt%-2wt%, the amount of oil-in-water emulsifier added is 0.4wt%-0.8wt%, and the amount of initiator added is 0.1wt%-0.5wt%; the volume ratio of the amphiphilic mesoporous magnesium oxide nanosheet dispersion to the mixed solution is (0.8-1.2):(0.8-1.5).

[0023] According to a specific embodiment of the present invention, preferably, the esterification reaction temperature is 60-70°C and the esterification reaction time is 3-6 hours.

[0024] According to a specific embodiment of the present invention, preferably, the oil-in-water emulsifier includes one or more of sodium dodecyl sulfate, Span series surfactants, and Tween series surfactants.

[0025] According to a specific embodiment of the present invention, preferably, the alcohol monomer includes one or more of triethylene glycol, ethylene glycol, vinyl alcohol, styrene alcohol, and 1,3-dienol.

[0026] According to a specific embodiment of the present invention, preferably, based on the mass of the mixed solution as 100%, the alcohol monomers are triethylene glycol and ethylene glycol, wherein the amount of triethylene glycol added is 0.5wt%-1.0wt% and the amount of ethylene glycol added is 0.5wt%-1.5wt%.

[0027] In some specific embodiments, preferably, the amphiphilic mesoporous magnesium oxide nanosheet dispersion is obtained by mixing amphiphilic mesoporous magnesium oxide nanosheet powder with water and a dispersant.

[0028] In some specific embodiments, preferably, the amount of dispersant added is 0.2wt%-0.4wt% based on 100% of the mass of the amphiphilic mesoporous magnesium oxide nanosheet dispersion.

[0029] In some specific embodiments, the dispersant preferably comprises lecithin and / or polyoxyethylene fatty alcohol ether.

[0030] In some specific embodiments, preferably, the method for preparing the amphiphilic mesoporous magnesium oxide nanosheets includes the following steps:

[0031] (a) Mix the aqueous solution of mesoporous magnesium oxide nanosheets with water, sodium chloride and paraffin, heat and stir for the first time to carry out the reaction, and filter to obtain paraffin microspheres coated with mesoporous magnesium oxide nanosheets.

[0032] (b) The paraffin microspheres coated with mesoporous magnesium oxide nanosheets were dispersed in an ethanol solution of organic amine. After a second stirring and washing, the paraffin was dissolved in chloroform and centrifuged to obtain amphiphilic mesoporous magnesium oxide nanosheets. After washing and freeze-drying, amphiphilic mesoporous magnesium oxide nanosheet powder was obtained for later use.

[0033] In the above preparation method, the paraffin microspheres coated with mesoporous magnesium oxide nanosheets obtained by direct filtration have multiple layers of mesoporous magnesium oxide nanosheets on their surface. After rinsing, the extra adsorbed mesoporous magnesium oxide nanosheets on the outer layer can be washed away, resulting in paraffin microspheres coated with a single layer of mesoporous magnesium oxide nanosheets. Preferably, the rinsing step includes rinsing with NaOH solution with a pH of 8-11 (e.g., 9.5), deionized water, and ethanol in sequence.

[0034] In the above preparation method, preferably, the product is washed multiple times with ethanol and / or deionized water before freeze-drying.

[0035] In the above preparation method, preferably, the mixing ratio of the mesoporous magnesium oxide nanosheet aqueous solution, deionized water, sodium chloride and paraffin is (90-100mL):(90-110mL):(4-6g):(60-75g).

[0036] In the above preparation method, preferably, the concentration of the mesoporous magnesium oxide nanosheet aqueous solution is 1-5 mg·mL. -1 .

[0037] In the above preparation method, preferably, the organic amine includes one or more of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

[0038] In some specific implementations, sodium chloride acts as an ionic strength modifier, which helps to regulate the ionic environment of the solution, affecting the dispersibility of mesoporous magnesium oxide nanosheets and their stability in aqueous solution. In addition, sodium chloride can also promote the formation of paraffin microspheres by changing the surface charge of mesoporous magnesium oxide.

[0039] In the above preparation method, preferably, the temperature of the first stirring is 60-70℃, the stirring speed is 8000-10000rpm, and the stirring time is 20-30min.

[0040] In the above preparation method, preferably, the second stirring condition is to stir and react at 30-50°C for 8-16 hours.

[0041] In some specific embodiments, preferably, the method for preparing the mesoporous magnesium oxide nanosheets includes the following steps:

[0042] (I) Magnesium oxide powder was obtained by wet precipitation using a precipitant, a protective agent and soluble magnesium salt, and then sintered.

[0043] (II) The magnesium oxide powder is dispersed in water and then subjected to distillation and high-temperature calcination to obtain mesoporous magnesium oxide nanosheets.

[0044] In the above preparation method, preferably, the sintering temperature is 400-800℃ and the sintering time is 2-5h.

[0045] In the above preparation method, preferably, the distillation treatment time is 2-3 hours.

[0046] In the above preparation method, preferably, the high-temperature calcination treatment temperature is 400-800℃ and the high-temperature calcination treatment time is 2.5-3h.

[0047] In the above preparation method, preferably, the pore size of the mesoporous magnesium oxide nanosheets is 10-50 nm.

[0048] In the above preparation method, preferably, the preparation method of the precursor Mg5(OH)2(CO3)4·4H2O is as follows: a soluble magnesium salt solution (e.g., Mg(NO3)2·6H2O solution) with a concentration of 0.2M-1.0M is mixed with a protective agent solution (e.g., polyethylene glycol solution) with a concentration of 0.1-1g / mL, and then a precipitant solution (e.g., ammonium carbonate solution) with a concentration of 1-4M is added dropwise. The mixture is stirred vigorously for 5-10 hours to obtain a milky white precipitate. The precipitate is then centrifuged, filtered, and dried to obtain the precursor Mg5(OH)2(CO3)4·4H2O.

[0049] In the above preparation method, preferably, the volume ratio of the soluble magnesium salt solution, the protective agent solution, and the precipitant solution is (6-8):(1-1.5):(8-12).

[0050] In some specific implementations, the self-permeable water-absorbing nano-modulation and driving materials provided by the present invention can be prepared using the above-described method for preparing self-permeable water-absorbing nano-modulation and driving materials, but are not limited to the above-described self-permeable water-absorbing nano-modulation and driving materials.

[0051] The present invention also provides a self-permeable water-absorbing nanomaterial for regulating and driving water flow, which is prepared by the above-described preparation method.

[0052] According to a specific embodiment of the present invention, preferably, the self-permeable water-absorbing nanomaterial comprises a multi-component copolyester core and an amphiphilic mesoporous magnesium oxide nanosheet shell; the thickness of the shell is 10-100 nm.

[0053] According to a specific embodiment of the present invention, preferably, the viscosity of the self-permeable water-absorbing nanomaterial is 1.0-5.5 mPa·s.

[0054] According to a specific embodiment of the present invention, preferably, the particle size of the self-permeable water-absorbing nanomaterial is 100-550 nm, and the specific surface area is 4-260 m². 2 / g, more preferably 4.36-240m 2 / g.

[0055] In this invention, mesoporous magnesium oxide nanosheets are first prepared, and then modified so that one side of the mesoporous magnesium oxide nanosheets is hydrophilic and the other side is modified with organic amines to make it lipophilic. Then, amphiphilic mesoporous magnesium oxide nanosheets, dispersants, alcohol monomers, terephthalic acid, oil-in-water emulsifiers, initiators and other agents are mixed evenly in a certain proportion and then esterified to form a self-permeable water-absorbing nanomaterial with a "core-shell structure". This material includes an oil-soluble multi-component copolyester core and a water-soluble shell (amphiphilic mesoporous magnesium oxide nanosheets) that is coated around the core.

[0056] The present invention also provides a method for sealing reservoir fractures, wherein the sealing method includes: injecting an absorbent fluid into the reservoir fractures for sealing; the absorbent fluid includes the above-mentioned self-absorbing water-based nano-modulation material and water; and the concentration of the self-absorbing water-based nano-modulation material in the absorbent fluid is 0.1%-0.5%.

[0057] In some specific embodiments, preferably, the sealing method is a sealing method for fractures in a permeable reservoir, specifically including: injecting an absorbent fluid into the fractures in the permeable reservoir for sealing; the absorbent fluid includes the above-mentioned self-absorbing water-based nano-modulation material and water; in the absorbent fluid, the concentration of the self-absorbing water-based nano-modulation material is 0.1%-0.5%.

[0058] According to a specific embodiment of the present invention, preferably, the temperature of the percolating liquid is controlled to be 50-350°C during the sealing process.

[0059] According to a specific embodiment of the present invention, preferably, the mineralization of the percolating fluid is controlled to be 100,000-200,000 mg / L during the sealing process.

[0060] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0061] (1) After the oil-soluble core of the self-permeable water-absorbing nano-modified flooding material provided by this invention is released, it can self-aggregate and block water in the water flow channel and emulsify and wash oil in the oil flow channel. Therefore, regardless of whether it encounters water or oil, the material can intelligently regulate its own behavior to achieve the effect of blocking water or washing oil, thereby achieving the purpose of intelligent deep flooding. Furthermore, by controlling the monomer concentration of the water-soluble shell and the process parameters of the polymerization process during its synthesis, the viscosity and shell thickness of the flooding material can be controlled, thereby achieving the controllable release of the core. Thus, the problems of inter-well flow, ineffective circulation of subsequent water injection, and reduced recovery rate caused by fractures in low-permeability reservoirs are solved.

[0062] (2) The reservoir fracture plugging method provided by this invention has advanced intelligent control technology, which can precisely control the injection, distribution and activation of the modulating and driving materials to achieve the best plugging effect. Through this intelligent control, a uniform and stable plugging body can be formed inside the reservoir, thereby improving the heterogeneity of the reservoir, improving the oil-water separation effect and increasing the recovery rate.

[0063] (3) The self-permeable water-absorbing nanomaterial provided by this invention has extremely high specific surface area and activity, stable chemical properties, and good temperature and salt resistance. It can fill cracks at the microscale to form a stable plug and prevent oil-water cross-flow. In addition, the particle size of the self-permeable water-absorbing nanomaterial provided by this invention is at the nanoscale, and the small particle size is more conducive to entering the micropores of the cracks. Furthermore, the addition of inorganic / organic nanomaterials increases the active sites of the self-permeable water-absorbing nanomaterial, which is beneficial to modification; by introducing alcohol chains into the core, the applicability of crude oil can be broadened; by using hydrophilic groups for grafting, the hydrophilicity of mesoporous magnesium oxide nanosheets can be improved, which is conducive to rapid wetting of rocks; the prepared amphiphilic mesoporous magnesium oxide nanosheets can adsorb surfactants in dispersants to form stable colloidal particles, improving oil washing performance and selective plugging performance. Attached Figure Description

[0064] Figure 1 is a microscopic photograph of the mesoporous magnesium oxide nanosheets prepared in Example 1.

[0065] Figure 2 is a schematic diagram of the structure of the self-permeable water-based nano-modulation material of the present invention (a), and a schematic diagram of the core release process when used for permeation liquid (b, c).

[0066] Figure 3 shows scanning electron microscope (SEM) images of the self-permeable water-absorbing nanomaterial prepared in Example 1 before core release (a), near core release (b), and complete core release (c) when it is used in the permeate.

[0067] Figure 4 shows a TEM image (a) of the core material of the self-permeable water-absorbing nano-modulation material prepared in Example 1 and a TEM image (b) of the multi-component copolyester prepared in Comparative Example 1.

[0068] Figure 5 shows the dispersion state of the self-permeable water-absorbing nanomaterial prepared in Example 1 in water before releasing its core.

[0069] Figure 6 shows the dispersion state of the self-permeable water-absorbing nanomaterial prepared in Example 1 in water after releasing its core.

[0070] Figure 7 is a microscopic image of the self-permeable water-absorbing nanomaterial prepared in Example 1 dispersed in water.

[0071] Figure 8 shows the contact angle test results of the self-permeable water-absorbing nanomaterial prepared in Example 1.

[0072] Figure 9 shows a microscopic image of the multi-component copolyester (core) prepared in Comparative Example 1 dispersed in kerosene.

[0073] Figure 10 shows the contact angle test results of the multi-component copolyester (core) prepared in Comparative Example 1.

[0074] Figure 11 shows the thermogravimetric curves of the amphiphilic mesoporous magnesium oxide nanosheets (shell), the self-permeable water-absorbing nanomaterial (core-shell), and the multi-component copolyester (core) prepared in Example 1.

[0075] Figure 12 shows the particle size curves of the amphiphilic mesoporous magnesium oxide nanosheets (shell material) and self-permeable water-absorbing nanomaterials (core-shell material) prepared in Example 1 in water with different mineralization.

[0076] Figure 13 shows the particle size curves of the amphiphilic mesoporous magnesium oxide nanosheets (shell material) and self-permeable water-absorbing nanomaterials (core-shell material) prepared in Example 1 in water at different temperatures.

[0077] Figure 14 shows the water-blocking experiment process of the self-permeable water-absorbing nano-modulation material prepared in Example 1.

[0078] Figure 15 shows the oil plugging experiment process of the self-permeable water-absorbing nano-modulation and driving material prepared in Example 1.

[0079] Figure 16 shows the water displacement experiment results of the self-permeable water-absorbing nanomaterial prepared in Example 1 on a 40mD permeable core.

[0080] Figure 17 shows the water displacement experiment results of the self-permeable water-absorbing nanomaterial prepared in Example 1 on an 8mD permeable core.

[0081] Figure 18 shows the molecular weight curve of the multi-component copolyester in Example 1.

[0082] Figure 19 shows the 1H NMR spectrum of the multi-component copolyester in Example 1.

[0083] Figure 20 shows the carbon NMR spectrum of the multi-component copolyester in Example 1. Detailed Implementation

[0084] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0085] Example 1:

[0086] This embodiment provides a method for preparing a self-permeable water-absorbing nanomaterial, which specifically includes the following steps:

[0087] The preparation of S1, mesoporous magnesium oxide nanosheets, specifically includes:

[0088] S101. The precursor Mg5(OH)2(CO3)4·4H2O was synthesized by wet precipitation method. The specific process is as follows:

[0089] Using (NH4)2CO3 (ammonium carbonate) as a precipitant and polyethylene glycol as a protective agent, 800 mL of a 0.6 M (mol / L) Mg(NO3)2·6H2O solution was mixed with 100 mL of a 0.55 g / mL polyethylene glycol solution to obtain a transparent solution A. Then, 1000 mL of a 2.5 M (NH4)2CO3 solution was added dropwise to the transparent solution A at a rate of 12 drops / min, and the mixture was stirred vigorously for 7.5 h at a stirring rate of 500 r / min to obtain a milky white precipitate.

[0090] The reaction equations for Mg(NO3)2·6H2O and (NH4)2CO3 are shown in equation (1):

[0091] S102. The milky white precipitate is a white precursor Mg5(OH)2(CO3)4·4H2O powder, which is dried at 80℃ after centrifugation; the dried precursor Mg5(OH)2(CO3)4·4H2O powder is sintered at 600℃ for 3.5h to obtain blocky magnesium oxide powder; wherein, the main reaction equation of this process can be expressed as equation (2): Mg5(OH)2(CO3)4·4H2O→5MgO+4CO2+5H2O Equation (2);

[0092] S103. Mix 20g of magnesium oxide powder with 200mL of deionized water, ultrasonically disperse for 10 minutes, then distill in a reflux apparatus for 3 hours, and then calcine at 600℃ for 3 hours to remove moisture, thus preparing mesoporous magnesium oxide nanosheets.

[0093] The mesoporous magnesium oxide nanosheets prepared in this embodiment are shown in Figure 1. As can be clearly seen from Figure 1, the mesoporous magnesium oxide nanosheets are sheet-like and have a porous structure with a pore size of 10-50 nm.

[0094] S2, modification of mesoporous magnesium oxide nanosheets, specifically includes:

[0095] S201. Mesoporous magnesium oxide nanosheets were prepared to a concentration of 3 mg·mL using a cell disruptor and ultrasound. -1A mesoporous magnesium oxide nanosheet aqueous solution was prepared. Then, 100 mL of the mesoporous magnesium oxide nanosheet aqueous solution was mixed with 100 mL of deionized water, 5 g of sodium chloride and 70 g of paraffin and heated to 70 °C. The mixture was stirred at 8000 rpm for 30 min with a high-speed stirrer and then cooled to room temperature. After filtration, paraffin microspheres coated with multilayer mesoporous magnesium oxide nanosheets were obtained. The microspheres were then washed with NaOH solution (pH = 9.5), deionized water and ethanol in sequence to remove the extra adsorbed mesoporous magnesium oxide nanosheets on the outer layer, resulting in paraffin microspheres coated with a single layer of mesoporous magnesium oxide nanosheets.

[0096] S202. The paraffin microspheres coated with the monolayer mesoporous magnesium oxide nanosheets are dispersed in an ethanol solution of organic amine and stirred at 40°C for 12 hours. After the reaction is complete, the mixture is filtered, washed three times with ethanol to remove residual organic amine, and then the paraffin is dissolved in chloroform. The mixture is then centrifuged to obtain modified mesoporous magnesium oxide nanosheets, namely amphiphilic mesoporous magnesium oxide nanosheets.

[0097] The organic amine is dodecylamine; the amphiphilic mesoporous magnesium oxide nanosheets are hydrophilic on one side and lipophilic on the other.

[0098] S203. The amphiphilic mesoporous magnesium oxide nanosheets are washed multiple times with ethanol and deionized water, dispersed in deionized water by ultrasonic treatment, and then freeze-dried to obtain amphiphilic mesoporous magnesium oxide nanosheet powder.

[0099] S3. Preparation of self-permeable water-absorbing nanomaterials for regulating water flow, specifically including:

[0100] S301. Take 0.03g of the above-prepared amphiphilic mesoporous magnesium oxide nanosheet powder and place it in 100mL of deionized water. Then add 0.2% lecithin (dispersant) and sonicate for 30 minutes to obtain a uniform amphiphilic mesoporous magnesium oxide nanosheet dispersion.

[0101] S302. Add triethylene glycol, ethylene glycol, terephthalic acid, sodium dodecyl sulfate (oil-in-water emulsifier), and concentrated sulfuric acid (initiator) to deionized water and mix thoroughly to obtain a mixed solution.

[0102] Based on the mass of the mixed solution as 100%, the amount of triethylene glycol added in the mixed solution is 0.75 wt%, the amount of ethylene glycol added is 1 wt%, the amount of terephthalic acid added is 1.5 wt%, the amount of sodium dodecyl sulfate added is 0.5 wt%, and the amount of concentrated sulfuric acid (concentration of 8 wt%) added is 0.1 wt%.

[0103] S303. Mix 50 mL of amphiphilic mesoporous magnesium oxide nanosheet dispersion with 50 mL of mixed solution and stir until homogeneous to obtain an emulsion. Under the action of the emulsifier, the amphiphilic mesoporous magnesium oxide nanosheets are adsorbed on the surface of the emulsion droplets, and the lipophilic groups extend inward. The core of the emulsion droplets consists of triethylene glycol, ethylene glycol, terephthalic acid, and an initiator.

[0104] Then, the system was gradually heated to 65°C to induce esterification of the core, forming a multi-component copolyester. The reaction lasted for 4.5 hours. After the reaction was completed, the system was cooled to room temperature to obtain a self-permeable water-absorbing nanomaterial with a "core-shell" structure.

[0105] At room temperature, the particle size of this self-permeable water-absorbing nanomaterial is 350-400 nm, the shell thickness is 10-50 nm, and the specific surface area is 210-240 m². 2 / g, viscosity is 1.5-4.5mPa·s.

[0106] The molecular structure of the multi-component copolyester core prepared in this embodiment is shown in formula (3), and the molecular weight curve is shown in Figure 18. Its molecular weight is around 10,000.

[0107] The proton NMR spectrum and carbon NMR spectrum of the multi-component copolyester core prepared in this embodiment are shown in Figure 19 and Figure 20, respectively.

[0108] Example 2:

[0109] This embodiment provides a method for preparing a self-permeable water-absorbing nanomaterial, which specifically includes the following steps:

[0110] The preparation of S1, mesoporous magnesium oxide nanosheets, specifically includes:

[0111] S101. The precursor Mg5(OH)2(CO3)4·4H2O was synthesized by wet precipitation method. The specific process is as follows:

[0112] Using (NH4)2CO3 (ammonium carbonate) as a precipitant and polyethylene glycol as a protective agent, 800 mL of a 0.2 M (mol / L) Mg(NO3)2·6H2O solution was mixed with 100 mL of a 0.1 g / mL polyethylene glycol solution to obtain a transparent solution A; then 1000 mL of a 1 M (NH4)2CO3 solution was added dropwise to the transparent solution A, and the mixture was stirred vigorously for 5 h to obtain a milky white precipitate.

[0113] S102. The milky white precipitate is a white precursor Mg5(OH)2(CO3)4·4H2O powder, which is dried at 70°C after centrifugation. The dried precursor Mg5(OH)2(CO3)4·4H2O powder is sintered at 400°C for 5 hours to obtain magnesium oxide powder.

[0114] S103. Mix 20g of magnesium oxide powder with 200mL of deionized water, ultrasonically disperse for 10 minutes, then distill in a reflux apparatus for 3 hours, and then calcine at 400℃ for 3 hours to remove moisture, thus preparing mesoporous magnesium oxide nanosheets with a pore size of 10-50nm.

[0115] S2, modification of mesoporous magnesium oxide nanosheets, specifically includes:

[0116] S201. Using a cell disruptor and ultrasound, mesoporous magnesium oxide nanosheets were prepared to a concentration of 1 mg·mL⁻¹. -1 A mesoporous magnesium oxide nanosheet aqueous solution was prepared. Then, 100 mL of the mesoporous magnesium oxide nanosheet aqueous solution was mixed with 100 mL of deionized water, 5 g of sodium chloride and 70 g of paraffin and heated to 70 °C. The mixture was stirred at 8000 rpm for 30 min with a high-speed stirrer and then cooled to room temperature. After filtration, paraffin microspheres coated with multilayer mesoporous magnesium oxide nanosheets were obtained. The microspheres were then washed with NaOH solution (pH = 9.5), deionized water and ethanol in sequence to remove the extra adsorbed mesoporous magnesium oxide nanosheets on the outer layer, resulting in paraffin microspheres coated with a single layer of mesoporous magnesium oxide nanosheets.

[0117] S202. The paraffin microspheres coated with the monolayer mesoporous magnesium oxide nanosheets are dispersed in an ethanol solution of organic amine and stirred at 30°C for 16 hours. After the reaction is complete, the mixture is filtered, washed three times with ethanol to remove residual organic amine, and then the paraffin is dissolved in chloroform. The mixture is then centrifuged to obtain modified mesoporous magnesium oxide nanosheets, namely amphiphilic mesoporous magnesium oxide nanosheets.

[0118] The organic amine is a mixture of tetradecanamine and hexadecamine in a mass ratio of 1:1; the amphiphilic mesoporous magnesium oxide nanosheets are hydrophilic on one side and lipophilic on the other.

[0119] S203. The amphiphilic mesoporous magnesium oxide nanosheets are washed multiple times with ethanol and deionized water, dispersed in deionized water by ultrasonic treatment, and then freeze-dried to obtain amphiphilic mesoporous magnesium oxide nanosheet powder.

[0120] S3. Preparation of self-permeable water-absorbing nanomaterials for regulating water flow, specifically including:

[0121] S301. Take 0.01g of the above-prepared amphiphilic mesoporous magnesium oxide nanosheet powder and place it in 100mL of deionized water. Then add 0.2% lecithin (dispersant) and sonicate for 30 minutes to obtain a uniform amphiphilic mesoporous magnesium oxide nanosheet dispersion.

[0122] S302. Add triethylene glycol, ethylene glycol, terephthalic acid, sodium dodecyl sulfate (oil-in-water emulsifier), and concentrated sulfuric acid (initiator) to deionized water and mix thoroughly to obtain a mixed solution.

[0123] Based on the mass of the mixed solution as 100%, the amount of triethylene glycol added in the mixed solution is 0.5 wt%, the amount of ethylene glycol added is 0.5 wt%, the amount of terephthalic acid added is 1 wt%, the amount of sodium dodecyl sulfate added is 0.5 wt%, and the amount of concentrated sulfuric acid (concentration of 5 wt%) added is 0.1 wt%.

[0124] S303. Mix 50 mL of amphiphilic mesoporous magnesium oxide nanosheet dispersion with 50 mL of mixed solution and stir until homogeneous to obtain an emulsion. Under the action of the emulsifier, the amphiphilic mesoporous magnesium oxide nanosheets are adsorbed on the surface of the emulsion droplets, and the lipophilic groups extend inward. The core of the emulsion droplets contains triethylene glycol, ethylene glycol, terephthalic acid, and an initiator.

[0125] Then, the system was gradually heated to 60°C to induce esterification of the core, forming a multi-component copolyester. The reaction lasted for 6 hours. After the reaction was completed, the system was cooled to room temperature to obtain a self-permeable water-absorbing nanomaterial with a "core-shell" structure.

[0126] At room temperature, the particle size of this self-permeable water-absorbing nanomaterial is 100-200 nm, the shell thickness is 30-60 nm, and the specific surface area is 12-240 m². 2 / g, viscosity is 1.0-2.5mPa·s.

[0127] Example 3:

[0128] This embodiment provides a method for preparing a self-permeable water-absorbing nanomaterial, which specifically includes the following steps:

[0129] The preparation of S1, mesoporous magnesium oxide nanosheets, specifically includes:

[0130] S101. The precursor Mg5(OH)2(CO3)4·4H2O was synthesized by wet precipitation method. The specific process is as follows:

[0131] Using (NH4)2CO3 (ammonium carbonate) as a precipitant and polyethylene glycol as a protective agent, 800 mL of a 1.0 M (mol / L) Mg(NO3)2·6H2O solution was mixed with 100 mL of a 1 g / mL polyethylene glycol solution to obtain a transparent solution A; then 1000 mL of a 4 M (NH4)2CO3 solution was added dropwise to the transparent solution A, and the mixture was stirred vigorously for 10 h to obtain a milky white precipitate.

[0132] S102. The milky white precipitate is a white precursor Mg5(OH)2(CO3)4·4H2O powder, which is dried at 90°C after centrifugation; the dried precursor Mg5(OH)2(CO3)4·4H2O powder is sintered at 800°C for 2 hours to obtain magnesium oxide powder.

[0133] S103. Mix 20g of magnesium oxide powder with 200mL of deionized water, ultrasonically disperse for 10 minutes, then distill in a reflux apparatus for 3 hours, and then calcine at 800℃ for 3 hours to remove moisture, thus preparing mesoporous magnesium oxide nanosheets with a pore size of 10-50nm.

[0134] S2, modification of mesoporous magnesium oxide nanosheets, specifically includes:

[0135] S201. Mesoporous magnesium oxide nanosheets were prepared to a concentration of 5 mg·mL using a cell disruptor and ultrasound. -1 A mesoporous magnesium oxide nanosheet aqueous solution was prepared. Then, 100 mL of the mesoporous magnesium oxide nanosheet aqueous solution was mixed with 100 mL of deionized water, 5 g of sodium chloride and 70 g of paraffin and heated to 70 °C. The mixture was stirred at 8000 rpm for 30 min with a high-speed stirrer and then cooled to room temperature. After filtration, paraffin microspheres coated with multilayer mesoporous magnesium oxide nanosheets were obtained. The microspheres were then washed with NaOH solution (pH = 9.5), deionized water and ethanol in sequence to remove the extra adsorbed mesoporous magnesium oxide nanosheets on the outer layer, resulting in paraffin microspheres coated with a single layer of mesoporous magnesium oxide nanosheets.

[0136] S202. The paraffin microspheres coated with the monolayer mesoporous magnesium oxide nanosheets are dispersed in an ethanol solution of organic amine and stirred at 50°C for 8 hours. After the reaction is complete, the mixture is filtered, washed three times with ethanol to remove residual organic amine, and then the paraffin is dissolved in chloroform. After centrifugation, the modified mesoporous magnesium oxide nanosheets, namely amphiphilic mesoporous magnesium oxide nanosheets, are obtained.

[0137] The organic amine is a mixture of dodecylamine, tetradecylamine and octadecylamine in a mass ratio of 1:1:1; the amphiphilic mesoporous magnesium oxide nanosheets have hydrophilic properties on one side and lipophilic properties on the other side.

[0138] S203. The amphiphilic mesoporous magnesium oxide nanosheets are washed multiple times with ethanol and deionized water, dispersed in deionized water by ultrasonic treatment, and then freeze-dried to obtain amphiphilic mesoporous magnesium oxide nanosheet powder.

[0139] S3. Preparation of self-permeable water-absorbing nanomaterials for regulating water flow, specifically including:

[0140] S301. Take 0.05g of the above-prepared amphiphilic mesoporous magnesium oxide nanosheet powder and place it in 100mL of deionized water. Then add 0.2% by mass of polyoxyethylene fatty alcohol ether (dispersant) and sonicate for 30 minutes to obtain a uniform amphiphilic mesoporous magnesium oxide nanosheet dispersion.

[0141] S302. Add triethylene glycol, ethylene glycol, terephthalic acid, sodium dodecyl sulfate (oil-in-water emulsifier), and concentrated sulfuric acid (initiator) to deionized water and mix thoroughly to obtain a mixed solution.

[0142] Based on the mass of the mixed solution as 100%, the amount of triethylene glycol added in the mixed solution is 1.0 wt%, the amount of ethylene glycol added is 1.5 wt%, the amount of terephthalic acid added is 2 wt%, the amount of sodium dodecyl sulfate added is 0.5 wt%, and the amount of concentrated sulfuric acid (concentration of 8 wt%) added is 0.1 wt%.

[0143] S303. Mix 50 mL of amphiphilic mesoporous magnesium oxide nanosheet dispersion with 50 mL of mixed solution and stir until homogeneous to obtain an emulsion. Under the action of the emulsifier, the amphiphilic mesoporous magnesium oxide nanosheets are adsorbed on the surface of the emulsion droplets, and the lipophilic groups extend inward. The core of the emulsion droplets contains triethylene glycol, ethylene glycol, terephthalic acid, and an initiator.

[0144] Then, the system was gradually heated to 70°C to induce esterification of the core, forming a multi-component copolyester. The reaction lasted for 3 hours. After the reaction was completed, the system was cooled to room temperature to obtain a self-permeable water-absorbing nanomaterial with a "core-shell" structure.

[0145] At room temperature, the particle size of this self-permeable water-absorbing nanomaterial is 200-450 nm, the shell thickness is 75-100 nm, and the specific surface area is 5.33-12 m². 2 / g, viscosity is 3.5-5.5mPa·s.

[0146] Example 4:

[0147] This embodiment provides a method for preparing a self-permeable water-absorbing nanomaterial, which specifically includes the following steps:

[0148] The preparation of S1, mesoporous magnesium oxide nanosheets, specifically includes:

[0149] S101. The precursor Mg5(OH)2(CO3)4·4H2O was synthesized by wet precipitation method. The specific process is as follows:

[0150] Using (NH4)2CO3 (ammonium carbonate) as a precipitant and polyethylene glycol as a protective agent, 800 mL of a 0.8 M (mol / L) Mg(NO3)2·6H2O solution was mixed with 100 mL of a 0.4 g / mL polyethylene glycol solution to obtain a transparent solution A; then 1000 mL of a 3 M (NH4)2CO3 solution was added dropwise to the transparent solution A, and the mixture was stirred vigorously for 8.5 h to obtain a milky white precipitate.

[0151] S102. The milky white precipitate is a white precursor Mg5(OH)2(CO3)4·4H2O powder, which is dried at 85°C after centrifugation. The dried precursor Mg5(OH)2(CO3)4·4H2O powder is sintered at 600°C for 3 hours to obtain magnesium oxide powder.

[0152] S103. Mix 20g of magnesium oxide powder with 200mL of deionized water, ultrasonically disperse for 10 minutes, then distill in a reflux apparatus for 3 hours, and then calcine at 500℃ for 3 hours to remove moisture, thus preparing mesoporous magnesium oxide nanosheets with a pore size of 20-50nm.

[0153] S2, modification of mesoporous magnesium oxide nanosheets, specifically includes:

[0154] S201. Using a cell disruptor and ultrasound, mesoporous magnesium oxide nanosheets were prepared to a concentration of 4 mg·mL⁻¹. -1 A mesoporous magnesium oxide nanosheet aqueous solution was prepared. Then, 100 mL of the mesoporous magnesium oxide nanosheet aqueous solution was mixed with 100 mL of deionized water, 5 g of sodium chloride and 70 g of paraffin and heated to 70 °C. The mixture was stirred at 8000 rpm for 30 min with a high-speed stirrer and then cooled to room temperature. After filtration, paraffin microspheres coated with multilayer mesoporous magnesium oxide nanosheets were obtained. The microspheres were then washed with NaOH solution (pH = 9.5), deionized water and ethanol in sequence to remove the extra adsorbed mesoporous magnesium oxide nanosheets on the outer layer, resulting in paraffin microspheres coated with a single layer of mesoporous magnesium oxide nanosheets.

[0155] S202. The paraffin microspheres coated with the monolayer mesoporous magnesium oxide nanosheets are dispersed in an ethanol solution of organic amine and stirred at 40°C for 10 hours. After the reaction is complete, the mixture is filtered, washed three times with ethanol to remove residual organic amine, and then the paraffin is dissolved in chloroform. The mixture is then centrifuged to obtain modified mesoporous magnesium oxide nanosheets, namely amphiphilic mesoporous magnesium oxide nanosheets.

[0156] The organic amine is tetradecylamine; the amphiphilic mesoporous magnesium oxide nanosheets have hydrophilic properties on one side and lipophilic properties on the other.

[0157] S203. The amphiphilic mesoporous magnesium oxide nanosheets are washed multiple times with ethanol and deionized water, dispersed in deionized water by ultrasonic treatment, and then freeze-dried to obtain amphiphilic mesoporous magnesium oxide nanosheet powder.

[0158] S3. Preparation of self-permeable water-absorbing nanomaterials for regulating water flow, specifically including:

[0159] S301. Take 0.04g of the above-prepared amphiphilic mesoporous magnesium oxide nanosheet powder and place it in 100mL of deionized water. Then add 0.2% lecithin (dispersant) and sonicate for 30 minutes to obtain a uniform amphiphilic mesoporous magnesium oxide nanosheet dispersion.

[0160] S302. Add triethylene glycol, ethylene glycol, terephthalic acid, sodium dodecyl sulfate (oil-in-water emulsifier), and concentrated sulfuric acid (initiator) to deionized water and mix thoroughly to obtain a mixed solution.

[0161] Based on the mass of the mixed solution as 100%, the amount of triethylene glycol added in the mixed solution is 0.6 wt%, the amount of ethylene glycol added is 1.2 wt%, the amount of terephthalic acid added is 1.8 wt%, the amount of sodium dodecyl sulfate added is 0.5 wt%, and the amount of concentrated sulfuric acid (concentration of 10 wt%) added is 0.1 wt%.

[0162] S303. Mix 50 mL of amphiphilic mesoporous magnesium oxide nanosheet dispersion with 50 mL of mixed solution and stir until homogeneous to obtain an emulsion. Under the action of the emulsifier, the amphiphilic mesoporous magnesium oxide nanosheets are adsorbed on the surface of the emulsion droplets, and the lipophilic groups extend inward. The core of the emulsion droplets contains triethylene glycol, ethylene glycol, terephthalic acid, and an initiator.

[0163] Then, the system was gradually heated to 65°C to induce esterification of the core, forming a multi-component copolyester. The reaction lasted for 5 hours. After the reaction was completed, the system was cooled to room temperature to obtain a self-permeable water-absorbing nanomaterial with a "core-shell" structure.

[0164] At room temperature, the particle size of this self-permeable water-absorbing nanomaterial is 150-550 nm, the shell thickness is 40-80 nm, and the specific surface area is 4.36-16 m². 2 / g, viscosity is 1.8-3.9mPa·s.

[0165] Comparative Example 1:

[0166] This comparative example only prepared a multi-component copolyester, and the preparation method was similar to the core preparation method in Example 1, specifically including the following steps:

[0167] Triethylene glycol, ethylene glycol, terephthalic acid, sodium dodecyl sulfate (oil-in-water emulsifier), and concentrated sulfuric acid (initiator) were added to deionized water and mixed thoroughly to obtain a mixed solution. Under stirring, the solution was heated to 65°C to induce an esterification reaction, which lasted for 4.5 hours, to obtain a multi-component copolyester (referred to as the core material).

[0168] Specifically, based on the mass of the mixed solution as 100%, the amount of triethylene glycol added in the mixed solution is 0.75 wt%, the amount of ethylene glycol added is 1 wt%, the amount of terephthalic acid added is 1.5 wt%, the amount of sodium dodecyl sulfate added is 0.5 wt%, and the amount of concentrated sulfuric acid (concentration of 8 wt%) added is 0.1 wt%.

[0169] The structure and morphological changes of the intelligent self-permeable water-absorbing nanomaterial prepared in this invention are investigated below:

[0170] Figure 2 schematically illustrates the structure and core release process of the self-permeable water-absorbing nanomaterial. Figure 2(a) is a schematic diagram of the structure of the self-permeable water-absorbing smart nanomaterial with a "core-shell" structure prepared in Example 1. In Figure 2(a), the yellow particles on the outer surface represent hydrophilic groups, and the light blue outer shell is amphiphilic mesoporous magnesium oxide nanosheets. In Figure 2(b), the brown particles in the core are multi-component copolyester particles. This indicates that during migration in the porous reservoir medium, under the action of shear force, the outer nanosheets of the self-permeable water-absorbing smart nanomaterial prepared in Example 1 are gradually peeled off (i.e., the outer shell begins to dissolve), and the multi-component copolyester particles in the core begin to be released. Figure 2(c) shows a schematic diagram of the self-permeable water-absorbing smart nanomaterial prepared in Example 1 having completely released the multi-component copolyester particles in water.

[0171] Figure 3 is a scanning electron microscope (SEM) image of the core release process of the self-permeable water-absorbing nanomaterial in Example 1 when used in the permeate. The self-permeable water-absorbing nanomaterial provided by this invention exists in three states under use: encapsulated state, critical release state, and complete release state. In Figure 3(a), the image before release shows that the outer shell is continuous and has not dissolved. Specifically, the core material is well encapsulated by the outer shell material. Although the outer shell surface has a layered feel, it is relatively smooth and there is no obvious granular core material precipitation. Figure 3(b) is the image near release, showing that the outer shell has dissolved. Specifically, the outer shell surface has obvious unevenness and a granular feel. This is because the thickness of the outer shell material has decreased or broken, causing the core material to begin to be released. Figure 3(c) is the image of complete core release, showing that the core particles have agglomerated. Specifically, the core material is clearly present on the outer shell surface, the particles are strong, and the oil-soluble core material agglomerates on the surface of the core and shell materials.

[0172] Figure 4(a) is a TEM image of the core material of the self-permeable water-absorbing nanomaterial in Example 1 after the core is released, and Figure 4(b) is a TEM image of the multi-component copolyester directly prepared in Comparative Example 1. As can be seen from Figure 4, the core material released by the self-permeable water-absorbing nanomaterial in Example 1 has the same size as the multi-component copolyester prepared in Comparative Example 1.

[0173] The dispersion of the intelligent self-permeable water-absorbing nanomaterial prepared in this invention in water and kerosene is investigated below:

[0174] The dispersion state of the self-permeable water-absorbing nanomaterial prepared in Example 1 in water before releasing the core is shown in Figure 5, and the dispersion state in water after releasing the core is shown in Figure 6. It can be seen from Figure 5 that the self-permeable water-absorbing nanomaterial is uniformly dispersed in water before releasing the core; it can be seen from Figure 6 that the released core oil phase aggregates.

[0175] After releasing the core, the self-permeable water-absorbing nanomaterial prepared in Example 1 was dissolved in kerosene and water. The dispersion of the amphiphilic mesoporous magnesium oxide nanosheets with the outer shell structure after core release was observed in the kerosene and aqueous phases. The results showed that after the core was released, the kerosene was clear and transparent, while the water was turbid. This indicates that the released core can aggregate and block in water, while exhibiting good dispersibility in the oil phase.

[0176] Figure 7 is a micrograph showing the dispersion of the self-permeable water-absorbing nanomaterial prepared in Example 1 in water. As can be seen from Figure 7, the self-permeable water-absorbing nanomaterial is uniformly dispersed in water before releasing the core. Further contact angle testing of the self-permeable water-absorbing nanomaterial was conducted, as shown in Figure 8. The measured contact angle was 49.9°, indicating that the outer shell is hydrophilic.

[0177] Figure 9 shows a micrograph of the dispersion of the multi-component copolyester (core material) prepared in Comparative Example 1 in kerosene, indicating that the multi-component copolyester (core) prepared in Comparative Example 1 disperses well in kerosene but cannot disperse in water. Further contact angle testing of the multi-component copolyester (core material) was performed, as shown in Figure 10, and the measured contact angle was 122°, indicating that the core is oleophilic.

[0178] The properties of the intelligent self-permeable water-absorbing nanomaterial prepared in this invention are investigated below:

[0179] Test Example 1: Temperature Resistance Evaluation

[0180] The temperature resistance of the core-shell structure is a key performance indicator for the application of the self-permeable water-absorbing nanomaterials with a core-shell structure provided in this invention to the development of low-permeability oil reservoirs. By analyzing the performance of the core-shell structure material under high-temperature conditions, we can gain a deeper understanding of its stability and reliability in practical applications.

[0181] Based on this, the same mass of the self-permeable water-absorbing nanomaterial with core-shell structure from Example 1 (represented as core-shell in Figure 11), the multi-component copolyester prepared in Comparative Example 1 (represented as core in Figure 11), and the amphiphilic mesoporous magnesium oxide nanosheet powder prepared in step S203 of Example 1 (represented as shell in Figure 11) were subjected to thermogravimetric analysis. The experimental results are shown in Figure 11.

[0182] As shown in Figure 11, the temperature resistance of the core-shell structured self-permeable water-absorbing nanomaterial (core-shell) decreases at 275℃, the temperature resistance of the amphiphilic mesoporous magnesium oxide nanosheets (outer shell) begins to decrease at 246℃, and the temperature resistance of the multi-component copolyester (core) decreases at 346℃. These results indicate that the self-permeable water-absorbing nanomaterial prepared in this invention does indeed possess good temperature resistance within a certain temperature range.

[0183] However, the performance of core-shell structured self-permeable water-absorbing nanomaterials for regulating water flow may be affected by rising temperatures, especially when exceeding their temperature resistance range. This can lead to changes in the core-shell structure, thereby affecting its stability and reliability in oilfield production environments. Therefore, proper control and management of temperature factors are necessary to ensure stable performance in practical applications. The introduction of the core improved the temperature resistance, increasing it from 246℃ to 275℃. This indicates that the introduction of the core not only enhances the overall temperature resistance of the core-shell particles but also improves their stability in high-temperature environments. However, it is important to note that exceeding the temperature range may lead to a decline in the performance of the core-shell structure material, or even structural damage. Therefore, strict temperature control is required in practical applications to ensure that the core-shell structure material can achieve its optimal performance, thereby realizing effective regulation and flow in low-permeability reservoir development.

[0184] Test Example 2: The effect of mineralization on the core release of self-permeable water-absorbing nanomaterials

[0185] The self-permeable water-absorbing nanomaterial for regulating and driving the flow (core-shell material in Figure 12) prepared in Example 1 and the amphiphilic mesoporous magnesium oxide nanosheet powder prepared in step S203 of Example 1 (shell material in Figure 12) were dissolved in water with different salinities. Four gradients of 10,000, 50,000, 100,000, and 200,000 mg / L were set according to the actual situation of oilfield application scenarios. The expansion ratio of the two materials under different conditions can be seen by measuring the particle size with a Zeta potentiometer, and a curve is plotted based on the data, as shown in Figure 12.

[0186] Since the core is a hydrophobic and oleophilic multi-component copolyester particle, its release significantly affects the particle size. Therefore, using particle size as a criterion is of great significance in studying the impact of core-shell structured materials after release. Analyzing the effect of mineralization on particle size allows for a more comprehensive understanding of the performance variation patterns of self-permeable water-absorbing nanomaterials and their potential effects in practical applications. As shown in Figure 12, the effect of mineralization on particle size is significant. With increasing mineralization, the particle size of both the outer shell and core-shell materials tends to increase. This trend is particularly pronounced when the mineralization reaches above 100,000 mg / L, indicating that mineralization has a significant impact on the particle size of the core-shell structure. Furthermore, when the mineralization is 200,000 mg / L, the particle size of the outer shell material is approximately 200 nm (referring to the thickness of the outer shell material), while the particle size of the core-shell material reaches approximately 650 nm. This indicates that with increasing mineralization, the particle size of the core-shell structured material also increases, which may be related to changes in the internal structure of the material and intermolecular interactions during the release process.

[0187] Test Example 3: The Effect of Temperature on Core Release of Self-Permeating Water-Absorbing Nanomaterials

[0188] The self-permeable water-absorbing nanomaterial for regulating and driving the flow (core-shell material in Figure 13) prepared in Example 1 and the amphiphilic mesoporous magnesium oxide nanosheet powder prepared in step S203 of Example 1 (shell material in Figure 13) were dissolved in water at different temperatures. According to the actual situation of oilfield application scenarios, three temperature gradients of 20℃, 50℃ and 80℃ were set. The expansion ratio of the two materials under different temperature conditions can be seen by measuring the particle size with a Zeta potentiometer, and a curve is plotted based on the data, as shown in Figure 13.

[0189] As shown in Figure 13, temperature also has a significant effect on particle size. Experimental results indicate that the particle size of the core-shell structured material increases with increasing temperature, and the rate of increase is relatively rapid. In particular, when the temperature reaches 80℃, the particle size of the core-shell material can reach approximately 800 nm. This suggests that increasing temperature induces changes in the core-shell structured material, leading to an increase in particle size. This change may be closely related to factors such as increased thermal motion of molecules within the material and changes in intermolecular forces.

[0190] Therefore, as shown in Test Examples 2 and 3, mineralization and temperature have a significant impact on the particle size of the core-shell structured material after release. Increased mineralization leads to an increase in the particle size of the core-shell material, while increased temperature also promotes an increase in the particle size.

[0191] Test Example 4: The Effect of Concentration of Self-Permeating Water-Absorbing Nanomaterials on Tension

[0192] The self-permeable water-based nano-modulation material prepared in Example 1 was mixed with deionized water to prepare permeation solutions of four concentrations: 0.1%, 0.2%, 0.3%, and 0.4%. The surface tension and interfacial tension of the four concentration permeation solutions were then measured, and the data are shown in Table 1 below.

[0193] Table 1. Surface tension and interfacial tension data for four concentrations of percolating solutions

[0194] As shown in Table 1, with the increase of the concentration of the self-percolating water-based nano-modulation material in the percolating solution, the surface tension and interfacial tension of the oil and water both decrease. Among them, the interfacial tension of the percolating solution with concentrations of 0.3% and 0.4% reaches about 0.01 mN / m, showing good adsorption performance. This indicates that the self-percolating water-based nano-modulation material can play a role in reducing tension.

[0195] Test Example 5: Comparison and Evaluation of Immersion Effect

[0196] The self-absorbing water-based nanomaterial prepared in Example 1 was mixed with deionized water to prepare an absorptive solution with a concentration of 0.3% (labeled as LP-30). This solution was compared with a 0.3% solution of sodium dodecyl sulfate surfactant (labeled as SC-30) and simulated mineralized water. The absorptive performance was tested at 90°C. The test results are shown in Table 2 below.

[0197] Table 2. Immersion effect data of different immersion solutions

[0198] As shown in Table 2, compared with commonly used surfactants such as sodium dodecyl sulfate solution and simulated mineralized water, the permeation liquid made from self-permeable water-based nanomaterials exhibits significantly superior permeation performance. This superiority is not only reflected in the reduction of the surface contact angle, but also in the decrease in water separation rate, the increase in oil washing rate, and the significant increase in permeation efficiency. These combined characteristics suggest that this permeation liquid may have wider applicability and higher performance levels in practical applications.

[0199] First, the properties associated with reduced contact angle likely stem from the increased affinity of the permeate prepared in this invention to the oil-water interface. A reduced contact angle generally implies a decrease in surface tension, which facilitates better interaction between the permeate and the oil-water interface, enhancing its activity near the interface and thus promoting the separation of the oil-water mixture.

[0200] Secondly, the characteristics of reducing water separation rate and increasing oil washing efficiency mean that this percolator has significant advantages in treating water-bearing reservoirs. The reduction in water separation rate may stem from the efficient separation of the aqueous phase by the percolator, resulting in more thorough removal of water during the separation process, thereby reducing the interference of water on the oil purification process.

[0201] The improved washing efficiency indicates that the permeate removes water while minimizing oil loss, thus improving oil recovery rate and quality. Furthermore, the significant increase in permeate rate means that this permeate has higher efficiency and faster penetration speed when injected into oil reservoirs or used to treat oil-water systems. The increased permeate rate may stem from optimized active components or structural characteristics of the permeate itself within the oil-water system, allowing for better diffusion and penetration within the reservoir, thereby improving the speed and efficiency of oil-water separation.

[0202] Test Example 6: Selective Blocking Performance

[0203] Water shut-off experiment: The self-permeable water-absorbing nano-modified displacement material prepared in Example 1 was mixed with deionized water to prepare a permeation solution with a concentration of 0.3% (labeled as LP-30). Then, 6.5 PV of simulated formation water was injected, followed by 1.5 PV of permeation solution. Subsequently, three reverse displacement oil experiments were conducted at a temperature of 150°C. The changes in injection pressure under different conditions were recorded, as shown in Figure 14. The experimental results are recorded in Table 3.

[0204] Oil plugging experiment: The self-permeable water-based nano-modulation material prepared in Example 1 was mixed with deionized water to prepare a permeation solution with a concentration of 0.3% (labeled as LP-30). First, a water drive experiment of 2PV was carried out, then 9PV of oil phase was injected, followed by 1PV of system, and finally reversed from the oil phase to carry out reverse drive. The change of injection pressure was observed, as shown in Figure 15. The experimental results are recorded in Table 3.

[0205] Table 3. Sealing effect data of water blocking and oil blocking experiments

[0206] According to the data in Table 3, for oil and water plugging experiments at the same concentration, the three-stage plugging method showed the most significant water plugging effect. Specifically, in the water flow channel, the plugging rate exceeded 80%, and after a period of time, its plugging effect showed greater resistance to erosion. This means that the three-stage plugging method exhibited excellent water plugging performance in the water channel, effectively preventing water flow and withstanding certain erosion and disturbance during actual operation. However, in the oil flow channel, the plugging rate was only 13.5%. This indicates that the three-stage plugging method exhibits different selective plugging characteristics in the water and oil channels. Despite its outstanding performance in the water channel, the plugging effect in the oil channel was relatively poor. Based on the different characteristics of the water and oil channels, it can be seen that the three-stage plugging method has a certain selective plugging capability. This allows for more precise and effective plugging operations in different reservoirs or oil-water systems.

[0207] Test Example 7: Evaluation of Oil Displacement Effect at Different Permeability Rates

[0208] Sandstone cores, 10 cm long and 2.5 cm in diameter, with permeabilities of 40 mD and 8 mD, were used as experimental subjects. First, the dry weight of the cores was weighed, and vacuum extraction was performed to simulate formation water, calculating the core pore volume. Then, a saturated oil experiment was conducted, and the saturated oil volume was recorded. Further, a water displacement experiment was conducted at 70°C, using two different concentrations (0.3% and 0.4%) of percolating fluid. Water displacement was performed once at a rate of 0.5 mL / min until water was completely displaced from the outlet. Then, water was injected into the system at a rate of 0.2 mL / min; subsequent water displacement was performed at a rate of 0.5 mL / min. Pressure changes were recorded, and the cumulative recovery rate and stage water cut were calculated. The results are shown in Figures 16 and 17, and the relevant data are summarized in Table 4.

[0209] Table 4. Oil displacement effect data of the two percolating solutions

[0210] In Table 4, LP-30 represents a 0.3% percolation solution prepared by adding deionized water to the self-percolation water-based nano-modulation material prepared in Example 1; LP-40 represents a 0.4% percolation solution prepared by adding deionized water to the self-percolation water-based nano-modulation material prepared in Example 1.

[0211] As shown in Table 4, Figures 16 and 17, under the 40 mD condition, LP-30 increased the recovery rate by 10.7 percentage points, while the plugging rate also reached 77.6%. Furthermore, under the 8 mD condition, the recovery rate increased significantly by 13.43 percentage points, and the plugging rate exceeded 90%. This indicates that the permeate provided by this invention exhibits good plugging and recovery effects under different porosity conditions.

[0212] In addition, water-blocking experiments and oil displacement effects were conducted on the permeation solutions prepared from the self-permeable water-absorbing nanomaterials in Examples 2-4, and the results are as follows:

[0213] The self-permeable water-absorbing nano-modulation material prepared in Example 2 was used to make a 0.3% permeate solution and a water-blocking experiment was conducted as shown in Figure 14. The blocking rate for the first, second, and third times all reached more than 80%, and the recovery rate could be increased by 15 percentage points.

[0214] The self-permeable water-absorbing nano-modulation material prepared in Example 3 was used to make a 0.1% permeate solution and a water-blocking experiment was conducted as shown in Figure 14. The blocking rate for the first, second, and third times all reached more than 80%, and the recovery rate could be increased by 10 percentage points.

[0215] The self-permeable water-absorbing nano-modulation material prepared in Example 4 was used to make a 0.5% permeate solution and a water-blocking experiment was conducted as shown in Figure 14. The blocking rate for the first, second, and third times all reached more than 80%, and the recovery rate could be increased by 15 percentage points.

[0216] In summary, the self-permeable water-absorbing nanomaterial for enhanced oil recovery provided by this invention has a "core-shell structure," wherein the core is a multi-component copolyester, and the outer shell is an amphiphilic mesoporous magnesium oxide nanosheet with both hydrophilic and oleophilic properties. When the core-shell structured material migrates in a porous medium, it is subjected to formation shear, and the outer shell gradually detaches from the surface and enters the dispersion medium. When the core-shell structure ruptures in a high-water-content fracture, the multi-component copolyester in the core aggregates to act as a sealant, thereby causing the detached and dispersed amphiphilic-oleophilic mesoporous magnesium oxide nanosheets to enter the reservoir matrix. They then reduce interfacial tension by adsorbing at the oil-water interface or alter the wettability of the rock surface, thus exerting a wedge-shaped permeation effect to strip away the oil film on the rock surface, ultimately achieving the enhanced oil recovery effect of nanofluids.

Claims

1. A self-permeable water-absorbing nanomaterial for regulating water flow, wherein, This self-permeable water-absorbing nanomaterial has a core-shell structure, with the shell being amphiphilic mesoporous magnesium oxide nanosheets and the core being a multi-component copolyester; the amphiphilic mesoporous magnesium oxide nanosheets have an asymmetric structure with one side being hydrophilic and the other side being oleophilic. The particle size of the self-permeable water-absorbing nanomaterial is 100-550 nm, and the thickness of the amphiphilic mesoporous magnesium oxide nanosheets is 10-100 nm.

2. The self-permeable water-absorbing nanomaterial according to claim 1, wherein, The viscosity of the self-permeable water-absorbing nanomaterial is 1.0-5.5 mPa·s.

3. The self-permeable water-absorbing nanomaterial according to claim 1, wherein, The specific surface area of the self-imbibing water-based nano profile control material is 4-260 m 2 / g.

4. The self-permeable water-absorbing nanomaterial according to claim 1, wherein, The molecular structural formula of the multi-component copolyester is as follows:

5. The self-permeable water-absorbing nanomaterial according to claim 1 or 4, wherein, The degree of polymerization of the multi-component copolyester is 50-250, and the molecular weight is 5000-30000.

6. The self-permeable water-absorbing nanomaterial according to any one of claims 1, 4-5, wherein, The multi-component copolyester is obtained by mixing alcohol monomers, terephthalic acid, initiator and water to obtain a mixed solution, and then heating the mixed solution to cause an esterification reaction. In the mixed solution, based on the mass of the mixed solution as 100%, the amount of alcohol monomer added is 0.5wt%-2.5wt%, the amount of terephthalic acid added is 1wt%-2wt%, and the amount of initiator added is 0.1wt%-0.5wt%.

7. The self-permeable water-absorbing nanomaterial according to claim 6, wherein, The mixed solution also contains 0.4wt%-0.8wt% of an oil-in-water emulsifier; the preparation steps of the multi-component copolyester further include: mixing the amphiphilic mesoporous magnesium oxide nanosheet dispersion with the mixed solution, and under the action of the oil-in-water emulsifier, causing the esterification reaction to occur inside the amphiphilic mesoporous magnesium oxide nanosheets to form a multi-component copolyester core.

8. The self-permeable water-absorbing nanomaterial according to claim 6, wherein, The alcohol monomers include one or more of triethylene glycol, ethylene glycol, vinyl alcohol, styrene alcohol, and 1,3-dienol.

9. The self-permeable water-absorbing nanomaterial according to claim 7, wherein, The oil-in-water emulsifier includes one or more of sodium dodecyl sulfate, Span series surfactants, and Tween series surfactants.

10. The self-permeable water-absorbing nanomaterial according to claim 6, wherein, The esterification reaction is carried out at a temperature of 60-70℃ for 3-6 hours.

11. A method for preparing a self-permeable water-absorbing nanomaterial, wherein, The preparation method includes: (1) Add alcohol monomers, terephthalic acid, oil-in-water emulsifier and initiator to water and mix to obtain a mixed solution; (2) The amphiphilic mesoporous magnesium oxide nanosheet dispersion is mixed with the mixed solution to obtain an emulsion; in the emulsion, the amphiphilic mesoporous magnesium oxide nanosheets are located on the surface of the emulsion droplets, while alcohol monomers, terephthalic acid, oil-in-water emulsifiers and initiators are coated in the core of the emulsion droplets; (3) Heating causes the core to undergo an esterification reaction to form a multi-component copolyester. Cooling yields a self-permeable water-absorbing nanomaterial with a core-shell structure; wherein the shell is an amphiphilic mesoporous magnesium oxide nanosheet and the core is a multi-component copolyester. The amphiphilic mesoporous magnesium oxide nanosheets have an asymmetric structure with one side being hydrophilic and the other side being oleophilic; the concentration of the amphiphilic mesoporous magnesium oxide nanosheets in the dispersion is 0.0001-0.0005 g / mL. In the mixed solution, based on the mass of the mixed solution as 100%, the amount of alcohol monomer added is 0.5wt%-2.5wt%, the amount of terephthalic acid added is 1wt%-2wt%, the amount of oil-in-water emulsifier added is 0.4wt%-0.8wt%, and the amount of initiator added is 0.1wt%-0.5wt%. The volume ratio of the amphiphilic mesoporous magnesium oxide nanosheet dispersion to the mixed solution is (0.8-1.2):(0.8-1.5).

12. The preparation method according to claim 11, wherein, The esterification reaction is carried out at a temperature of 60-70℃ for 3-6 hours.

13. The preparation method according to claim 11, wherein, The oil-in-water emulsifier includes one or more of sodium dodecyl sulfate, Span series surfactants, and Tween series surfactants.

14. The preparation method according to claim 11, wherein, The alcohol monomers include one or more of triethylene glycol, ethylene glycol, vinyl alcohol, styrene alcohol, and 1,3-dienol.

15. The preparation method according to claim 14, wherein, The alcohol monomers are triethylene glycol and ethylene glycol. Based on the mass of the mixed solution as 100%, the amount of triethylene glycol added is 0.5wt%-1.0wt%, and the amount of ethylene glycol added is 0.5wt%-1.5wt%.

16. The preparation method according to claim 11, wherein, The preparation method of the amphiphilic mesoporous magnesium oxide nanosheets includes the following steps: (a) Mix the aqueous solution of mesoporous magnesium oxide nanosheets with water, sodium chloride and paraffin, heat and stir for the first time to carry out the reaction, and filter to obtain paraffin microspheres coated with mesoporous magnesium oxide nanosheets. (b) The paraffin microspheres coated with mesoporous magnesium oxide nanosheets were dispersed in an ethanol solution of organic amine. After a second stirring and washing, the paraffin was dissolved in chloroform and centrifuged to obtain amphiphilic mesoporous magnesium oxide nanosheets. After washing and freeze-drying, amphiphilic mesoporous magnesium oxide nanosheet powder was obtained for later use.

17. The preparation method according to claim 16, wherein, The mixing ratio of the mesoporous magnesium oxide nanosheet aqueous solution, deionized water, sodium chloride and paraffin is (90-100mL):(90-110mL):(4-6g):(60-75g); And / or, the concentration of the aqueous solution of the mesoporous magnesium oxide nanosheets is 1-5 mg·mL. -1 .

18. The preparation method according to claim 16, wherein, The organic amines include one or more of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

19. The preparation method according to claim 16, wherein, The method for preparing the mesoporous magnesium oxide nanosheets includes the following steps: (I) Magnesium oxide powder was obtained by wet precipitation using a precipitant, a protective agent and soluble magnesium salt, and then sintered. (II) The magnesium oxide powder is dispersed in water and then subjected to distillation and high-temperature calcination to obtain mesoporous magnesium oxide nanosheets.

20. The preparation method according to claim 19, wherein, The preparation method of the precursor Mg5(OH)2(CO3)4·4H2O is as follows: a soluble magnesium salt solution with a concentration of 0.2M-1.0M is mixed with a protective agent solution with a concentration of 0.1-1g / mL, and then a precipitant solution with a concentration of 1-4M is added dropwise. The mixture is stirred vigorously for 5-10 hours to obtain a precipitate. The precipitate is then centrifuged, filtered, and dried to obtain the precursor Mg5(OH)2(CO3)4·4H2O. And / or, the volume ratio of the soluble magnesium salt solution, the protective agent solution, and the precipitant solution is (6-8):(1-1.5):(8-12).

21. A self-permeable water-absorbing nanomaterial for regulating water flow, which is prepared by the preparation method according to any one of claims 11-20.

22. The self-permeable water-absorbing nanomaterial according to claim 21, wherein, This self-permeable water-based nanomaterial comprises a multi-component copolyester core and an amphiphilic mesoporous magnesium oxide nanosheet shell. The thickness of the outer shell is 10-100 nm.

23. The self-permeable water-absorbing nanomaterial according to claim 21, wherein, The viscosity of the self-permeable water-absorbing nanomaterial is 1.0-5.5 mPa·s.

24. The self-permeable water-absorbing nanomaterial according to claim 21, wherein, The self-permeable water-absorbing nanomaterial has a particle size of 100-550 nm and a specific surface area of ​​4-260 m². 2 / g.

25. A method for sealing reservoir fractures, wherein, The sealing method involves injecting permeate into reservoir fractures to seal them; The percolating liquid comprises the self-percolating water-based nanomaterial according to any one of claims 1-10, 21-24 and water; in the percolating liquid, the concentration of the self-percolating water-based nanomaterial is 0.1%-0.5%.

26. The sealing method according to claim 25, wherein, The temperature of the percolating liquid is controlled at 50-350°C during the sealing process.

27. The sealing method according to claim 25, wherein, During the sealing process, the mineralization of the percolating fluid is controlled to be 100,000-200,000 mg / L.

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