Multi-network interpenetrating gel microsphere with temperature-controlled delayed expansion and preparation method thereof

Abstract

The invention relates to the technical field of oil-gas field development reservoir transformation, and discloses a multi-network interpenetrating gel microsphere with temperature-controlled delayed expansion, which comprises a triple network gel structure formed by polymerizing double-network gel and a polymerizable, crosslinkable and temperature-controlled hydrolyzable macromolecular monomer, the macromonomer is polyethylene glycol disuccinate hydroxyethyl diacrylate or polyethylene glycol disuccinate hydroxyethyl dimethylacrylate, and has the following structural general formula: in the formula, R is H or CH3, and n is equal to 2-10. According to the multi-network interpenetrating gel microsphere with the temperature-controlled delayed expansion, disclosed by the invention, double-network gel particles are formed through in-situ reconstruction in a high-temperature environment at the deep part of a stratum for the first time, and the advantages of high strength, high toughness and high deformability of the double-network gel particles are fully exerted; the key problems that traditional expansion gel particles are fragile under pressure and poor in plugging and transporting capacity are solved, efficient oil field deep water plugging and profile control are expected to be achieved, and the high application value is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of reservoir reconstruction in oil and gas field development, and particularly relates to a multi-network interpenetrating gel microsphere with temperature-controlled delayed expansion and a preparation method thereof. BACKGROUND

[0002] At present, most of the oil fields at home and abroad have entered the middle and late stages of development and are in the high and ultra-high water cut development stages. The injected water forms inefficient and ineffective circulation in the high permeability layer, and a large amount of remaining oil in the reservoir is difficult to be produced due to being stored in the low permeability layer, which seriously restricts the displacement effect of water flooding and chemical flooding. The research and development of high-efficiency fluid flow diversion technology has become the key to improve this situation.

[0003] In the prior art, pre-crosslinked gel particles are prepared by ground polymerization, drying, granulation and other processes based on hydrophilic monomers such as acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and crosslinking agents. The pre-crosslinked gel particles are widely used as profile control and water plugging materials due to their water-swelling properties, and are used to plug the channeling channels of the formation, improve the interlayer contradiction and expand the swept volume of water flooding. However, the conventional pre-crosslinked gel particles have significant defects: the water absorption rate is too fast, the swelling is rapid during injection, and the particles are prone to accumulate in the near-wellbore zone, making it difficult to enter the deep part of the reservoir, and the profile control radius is limited; and the mechanical strength of the particles after water absorption and swelling is low, and the toughness is insufficient, and the particles are prone to breakage after being sheared and extruded by the formation pressure, resulting in low migration and plugging capacity, and the deep and efficient profile control cannot be achieved.

[0004] Compared with traditional hydrogels, double-network hydrogels have more excellent mechanical strength and toughness, and the tensile fracture stress can reach 1-10 MPa and the strain can reach 1000-2000%, which provides a new direction for the research and development of deep profile control and plugging materials. However, the traditional double-network hydrogel still has obvious deficiencies: it lacks slow swelling performance, and the gel particles formed by the traditional double-network hydrogel still face the problems of rapid water absorption and swelling, and easy accumulation in the near-wellbore zone when used for profile control and water plugging, which further leads to a sharp rise in injection pressure and even plugging of the work string; and the preparation of the traditional double-network hydrogel requires first preparing a single-network hydrogel, then swelling and initiating polymerization in a second network pre-polymer, which is a step-by-step incremental network structure preparation process that cannot construct a double-network gel in a formation environment, which seriously restricts its application in deep water plugging and profile control in oil fields.

[0005] Therefore, it is urgent to develop a new type of profile control and water plugging material that can adapt to the deep environment of oil fields, has a controllable swelling rate, excellent mechanical properties and strong migration and plugging capacity, in order to break through the bottleneck of the existing technology and meet the actual needs of efficient deep profile control and water plugging. SUMMARY

[0006] The present application aims to provide a multiple network interpenetrating gel microsphere with temperature-controlled delayed expansion and a preparation method thereof to overcome the uncontrollable expansion problem and injection problem of deep formation of a double network hydrogel.

[0007] To achieve the above-mentioned purpose, the present application discloses a multiple network interpenetrating gel microsphere with temperature-controlled delayed expansion, comprising a double network gel and a triple network gel structure formed by polymerization of a polymerizable, cross-linkable and temperature-controlled hydrolyzable macromonomer.

[0008] The macromonomer is polyethylene glycol disuccinate dihydroxyethyl acrylate or polyethylene glycol disuccinate dimethyl hydroxyethyl methacrylate, having the following general structure:

[0009]

[0010] wherein R is H or CH3, and n=2-10, preferably n=5.

[0011] Further, the macromonomer is prepared by the following method: one of hydroxyethyl acrylate and hydroxyethyl methacrylate is used as raw material together with polyethylene glycol disuccinate, dissolved in an organic solvent, and reacted by esterification at room temperature for 12-24 hours in the presence of catalyst dicyclohexyl carbodiimide (DCC) and dimethyl amino pyridine (DMAP), and then filtered, rotary evaporated, precipitated and dried.

[0012] Further, the molar ratio of one of hydroxyethyl acrylate and hydroxyethyl methacrylate to polyethylene glycol disuccinate is 2-3:1; the number average molecular weight of the polyethylene glycol disuccinate is 300-660, and the number of -CH2CH2O- repeating units is 2-10, preferably the number of -CH2CH2O- units is 5; the organic solvent is dichloromethane, chloroform, 1,4-dioxane, dimethyl sulfoxide, tetrahydrofuran or N,N'-dimethyl formamide; the molar ratio of the catalyst dicyclohexyl carbodiimide to dimethyl amino pyridine is 5-10:1, and the molar ratio of dicyclohexyl carbodiimide to polyethylene glycol disuccinate is 3-5:1; the solvent used for precipitation is diethyl ether, petroleum ether, n-hexane or cyclohexane.

[0013] Further, the present application discloses a preparation method of the multiple network interpenetrating gel microsphere with temperature-controlled delayed expansion, comprising the following steps:

[0014] S1, preparing a double network gel matrix: accurately weighing monomer 2-acrylamido-2-methylpropanesulfonic acid (AMPS), cross-linking agent N,N'-methylene bisacrylamide (MBA) and water-soluble initiator, dissolving them in distilled water to form a first layer network pre-polymer, wherein the concentration of 2-acrylamido-2-methylpropanesulfonic acid is 1-2 mol·L -1, the amount of N,N'-methylenebisacrylamide and initiator is 2-4 mol% and 0.1-0.3 mol% of monomer 2-acrylamido-2-methylpropanesulfonic acid respectively; after nitrogen deoxidization, the polymerization is initiated by ultraviolet light or heat to obtain poly 2-acrylamido-2-methylpropanesulfonic acid (PAMPS) single network hydrogel;

[0015] Then, monomer acrylamide (AM), crosslinking agent N,N'-methylenebisacrylamide and water-soluble initiator are accurately weighed and dissolved in distilled water to form a second layer network pre-polymer, wherein the concentration of acrylamide is 2-4 mol·L -1 , the amount of crosslinking agent N,N'-methylenebisacrylamide and initiator is 0.1-0.3 mol% of monomer acrylamide;

[0016] Then, the prepared poly 2-acrylamido-2-methylpropanesulfonic acid single network hydrogel is placed in the prepared second layer network pre-polymer solution, and after swelling at room temperature for 24 h, the polymerization is initiated by ultraviolet light or heat after nitrogen deoxidization, to obtain a double network gel matrix formed by polymerization of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid;

[0017] S2, preparing a triple network gel: the double network gel block is dried in an oven or freeze-dried in a freeze dryer, and then the dehydrated polymer sample is soaked in an excess of a pre-polymerized, cross-linkable and temperature-controllable hydrolyzed macromonomer solution until swelling equilibrium is reached. The swollen gel block is taken out and placed in a transparent airtight container, and after nitrogen deoxidization, the macromonomer is polymerized by ultraviolet light at room temperature to prepare a triple network gel;

[0018] S3, drying and crushing the triple network gel prepared in S2 to obtain a multi-network interpenetrating gel microsphere with temperature-controllable delayed expansion.

[0019] Further, the pre-polymerized solution of macromonomer in step S2 is a solution formed by dissolving macromonomer and water-soluble initiator in water; the concentration of macromonomer is 10-30%, and the water-soluble initiator accounts for 0.5-2% of the total mass of macromonomer; the mass ratio of macromonomer to double network gel block is 5-10:1.

[0020] Further, the water-soluble initiator is one or more of thermal initiator azobisdimethylamidinum hydrochloride, ammonium persulfate, potassium persulfate or photoinitiator Irgacure 2959.

[0021] Further, the ultraviolet light polymerization temperature is room temperature, and the polymerization time is 2-6 h; the thermal polymerization temperature is 40-80℃, and the polymerization time is 4-24 h.

[0022] Further, the application further discloses application of the multiple network interpenetrating gel microspheres with temperature-controlled delayed expansion in preparation of oilfield profile control and water plugging materials.

[0023] The application has the following advantages and positive effects:

[0024] (1) The double network gel and the polymerizable, cross-linkable and temperature-controllable hydrolytic macromonomer are prepared from raw materials which are all commercial products.

[0025] (2) The multiple network interpenetrating gel microspheres with temperature-controlled delayed expansion are prepared by a simple process.

[0026] (3) The multiple network interpenetrating gel microspheres with temperature-controlled delayed expansion are reconstructed in-situ into double network gel particles in deep formation under high temperature, so that the advantages of high strength, high toughness and high deformability of the double network gel particles are fully exerted, the migration and plugging capacity of the gel particles in deep formation are expected to be significantly improved, the key problems of the traditional swelling gel particles, such as easy breakage under pressure and poor plugging and migration capacity, are solved, efficient water plugging and profile control in deep formation is expected to be realized, and the multiple network interpenetrating gel microspheres have great application value.

[0027] The technical scheme of the application will be further described in detail through examples. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A knot drawing of a linear sample of the double network gel prepared in the example 1 of the application is shown in the figure;

[0029] Figure 2 A weight lifting drawing of the linear sample of the double network gel prepared in the example 1 of the application is shown in the figure;

[0030] Figure 3 A tensile deformation drawing of a dumbbell sample of the double network gel prepared in the example 1 of the application is shown in the figure;

[0031] Figure 4 An infrared spectrum drawing of the polymerizable, cross-linkable and temperature-controllable hydrolytic macromonomer and polyethylene glycol (PEG) prepared in the example 1 of the application is shown in the figure; 1 HNMR nuclear magnetic resonance spectrum;

[0032] Figure 5 An infrared spectrum drawing of the polymerizable, cross-linkable and temperature-controllable hydrolytic macromonomer and polyethylene glycol (PEG) prepared in the example 1 of the application is shown in the figure;

[0033] Figure 6 The photos of the swelling morphology of the multiple network interpenetrating gel pieces prepared in Example 2 of the present application with temperature-controlled delayed swelling in water at 25℃, 60℃ and 90℃ after hydrolytic reconstitution for different times;

[0034] Figure 7 The swelling behavior of the multiple network interpenetrating gel pieces prepared in Example 2 of the present application with temperature-controlled delayed swelling in water at 25℃, 60℃ and 90℃ after hydrolytic reconstitution;

[0035] Figure 8 The mechanical properties of the double network gel prepared in Example 2 of the present application and the mechanical properties of the multiple network interpenetrating gel prepared with temperature-controlled delayed swelling after hydrolytic reconstitution at 90℃. DETAILED DESCRIPTION

[0036] The technical solutions of the present application are further described below through examples.

[0037] In order to facilitate the understanding of the content of the present application, the present application now lists the following examples. The examples are only to help understand the present application and should not be regarded as specific limitations of the present application. Because the present application can also be described and explained by other solutions without departing from the technical features of the present application, all changes within the scope of the present application or within the equivalent scope of the present application should belong to the protection scope of the present application.

[0038] Example 1

[0039] 1.1 Preparation of double network gel matrix:

[0040] The monomers AMPS (10.3625 g, 0.05 mol), crosslinking agent MBA (0.154 g, 0.001 mol), and initiator azobisdimethylamid hydrochloride (0.0136 g, 0.0005 mol) were weighed and dissolved in 50 mL of distilled water. After nitrogen replacement to remove oxygen, polymerization was carried out at 60℃ for 24 h to obtain a PAMPS single network hydrogel. Subsequently, the monomers AM (142.16 g, 2 mol), crosslinking agent MBA (0.30836 g, 0.002 mol), and initiator azobisdimethylamid hydrochloride (0.5424 g, 0.002 mol) were accurately weighed and dissolved in 1000 mL of distilled water. After mixing uniformly, the prepared PAMPS gel pieces were placed in the prepared solution, and the solution was fully swollen at room temperature for 24 h. After nitrogen replacement to remove oxygen, thermal initiation polymerization was carried out in an oven at 80℃ for 12 h to obtain a double network gel formed by AM and AMPS.

[0041] The prepared double network gel was cut into linear or dumbbell-shaped, as shown in Figure 1 , Figure 2 and Figure 3 . Figure 1This demonstrates that the linear sample of the dual-network gel can be knotted and stretched without any damage, indicating that the gel has excellent toughness. Figure 2 The results showed that the linear sample of the dual-network gel could lift a 200g weight, indicating that the gel has excellent mechanical strength. Figure 3 The stretching process of a dumbbell-shaped sample of a dual-network gel is shown, which demonstrates that the gel has excellent stretchability and high deformability.

[0042] 1.2 Preparation of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers:

[0043] Polyethylene glycol disuccinate (6.56 g, 10 mmol) with 10 ethylene glycol units was placed in a 100 mL reaction flask. Dicyclohexylcarbodiimide (DCC) (10.3 g, 50 mmol) and dimethylaminopyridine (DMAP) (1.2 g, 10 mmol) were also added to the flask, and the mixture was dissolved in 50.0 mL of dichloromethane under a nitrogen atmosphere. Subsequently, hydroxyethyl methacrylate (HEMA) (2.6 g, 20 mmol) was added to the flask, and the mixture was stirred at room temperature for 24 h. After the reaction was complete, the byproduct dicyclohexylurea was removed by filtration. The filtrate was collected, concentrated by rotary evaporation, and then added dropwise to ice-cold diethyl ether for precipitation. The product was obtained by vacuum drying.

[0044] The obtained polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomer products were characterized by NMR. 1 HNMR (500M, D2O) such as Figure 4 As shown, the characteristic peaks of the proton NMR spectra of double bonds, methyl groups, and methylene groups in temperature-controlled hydrolyzed macromonomers, as well as those of methylene groups in succinate esters and polyethylene glycol units, are observed in... Figure 6 Both observations confirm that the prepared crosslinking agent contains double bonds, and the temperature-controlled hydrolysis macromonomer of polyethylene glycol was successfully prepared. The obtained polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomer and polyethylene glycol (PEG) were characterized using infrared spectroscopy, as shown in the infrared spectra. Figure 5 As shown, the infrared spectrum of the macromonomer is basically consistent with that of PEG, but with an additional 2929 cm⁻¹. -1 The absorption peak at 1717 cm⁻¹ is the stretching vibration absorption peak of -CH₃. -1 The newly added absorption peak is the stretching vibration absorption peak of -C=O; 1642 cm⁻¹ -1 The absorption peak at 1525 cm⁻¹ is the stretching vibration absorption peak of -C=C. -1 The absorption peak at this location corresponds to the deformation vibration of -CH3. The characteristic infrared peaks of methyl, methylene, carbonyl, double bonds, and carbon-oxygen bonds in polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers are located at... Figure 5 Both observations further confirm that temperature-controlled hydrolysis of macromolecular monomers containing double bonds, carbon groups, and polyethylene glycol has been successfully prepared.

[0045] 1.3 Preparation of multi-network interpenetrating gels and microspheres with temperature-controlled delayed expansion:

[0046] The double-network gel block from step 1.1 was dried in an oven to constant weight. Then, about 2g of the dried sample block was cut off for later use. Subsequently, 10g of the macromonomer and 0.05g of the photoinitiator Irgacure 2959 prepared in step 1.2 were dissolved in 100mL of distilled water. After complete dissolution, the 2g of the dried sample block was placed in the macromolecular prepolymer solution to swell and reach equilibrium. The swollen gel block was then placed in a transparent, sealed container and purged with nitrogen to remove oxygen. Subsequently, the macromonomer was polymerized at room temperature using ultraviolet light for 6 hours to obtain a triple-network gel. This gel was dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

[0047] Example 2

[0048] 2.1 Preparation of the dual-network gel matrix:

[0049] The monomer AMPS (10.3625 g, 0.05 mol), crosslinking agent MBA (0.46 g, 0.003 mol), and initiator azobisisobutylamidine hydrochloride (0.03 g, 0.0015 mol) were weighed and dissolved in 50 mL of distilled water. After nitrogen purging and oxygen removal, polymerization was carried out at 40 °C for 24 h to obtain a PAMPS single-network hydrogel. Subsequently, the monomer AM (284.3 g, 4 mol), crosslinking agent MBA (0.92 g, 0.006 mol), and initiator azobisisobutylamidine hydrochloride (1.6 g, 0.006 mol) were accurately weighed and dissolved in 1000 mL of distilled water. After mixing evenly, the prepared PAMPS gel block was placed in the prepared solution and allowed to swell fully at room temperature for 24 h. After nitrogen purging and oxygen removal, thermal polymerization was carried out in an oven at 80 °C for 4 h to obtain a double-network hydrogel formed by acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0050] 2.2 Preparation of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers:

[0051] Polyethylene glycol disuccinate (4.36 g, 10 mmol) with five ethylene glycol units was placed in a 100 mL reaction flask. Dicyclohexylcarbodiimide (DCC) (7.8 g, 30 mmol) and dimethylaminopyridine (DMAP) (0.36 g, 3 mmol) were also added to the flask, and the mixture was dissolved in 50.0 mL of chloroform under a nitrogen atmosphere. Subsequently, hydroxyethyl acrylate (EMA) (2.32 g, 20 mmol) was added to the flask, and the mixture was stirred at room temperature for 24 h. After the reaction was complete, the byproduct dicyclohexylurea was removed by filtration. The filtrate was collected, concentrated by rotary evaporation, and then added dropwise to ice-cold petroleum ether for precipitation. The product was obtained by vacuum drying.

[0052] 2.3 Preparation of multi-network interpenetrating gels and microspheres with temperature-controlled delayed expansion:

[0053] The double-network gel block from step 2.1 was dried in an oven to constant weight. Then, about 2g of the dried sample block was cut off for later use. Subsequently, 20g of the macromonomer and 0.4g of the photoinitiator Irgacure 2959 prepared in step 2.2 were dissolved in 100mL of distilled water. After complete dissolution, the 2g of the dried sample block was placed in the macromolecular prepolymer solution to swell and reach equilibrium. The swollen gel block was then removed and placed in a transparent, sealed container filled with nitrogen to remove oxygen. Subsequently, the macromonomer was polymerized at room temperature using ultraviolet light for 2 hours to obtain a triple-network gel. This gel was dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

[0054] The prepared multi-network interpenetrating gel blocks with temperature-controlled delayed expansion were placed in water at 25℃, 60℃, and 90℃ and kept sealed for a period of time. The temperature-controlled hydrolysis and expansion process of the multi-network interpenetrating gel blocks with temperature-controlled delayed expansion at 25℃, 60℃, and 90℃ was observed. Figure 6 As shown, from Figure 6 It can be seen that the prepared gel blocks remain stable and do not swell at room temperature (25℃), while at 60℃ and 90℃, the prepared multi-network interpenetrating gel blocks gradually hydrolyze and swell. At 60℃, the hydrolysis and swelling increased by approximately 6–7 times in 10 days, and at 90℃, the hydrolysis and swelling increased by approximately 10–12 times in 10 days. The prepared multi-network interpenetrating gel blocks were placed in water at 25℃, 60℃, and 90℃ to study the relationship between their swelling performance and time. Figure 7 As shown, by Figure 7 It can be seen that the gel can remain stable at room temperature, but it will hydrolyze and reconstruct and slowly expand at high temperature. The expansion is faster at higher temperatures, which further confirms that the prepared multi-network interpenetrating gel has temperature-controlled delayed expansion properties.

[0055] The mechanical properties of the dual-network gel prepared in section 2.1 and the mechanical properties of the multi-network interpenetrating gel with temperature-controlled delayed expansion prepared in this example after hydrolysis and reconstruction at 90°C were tested. Figure 8 As shown, by Figure 8 It is known that the dual-network hydrogel has high strength, up to 1.2 MPa, and the hydrolysis-reconstruction gel at 90℃ still maintains good mechanical properties, up to 0.5 MPa. These results indicate that the multi-network interpenetrating gel with temperature-controlled delayed expansion prepared in this embodiment forms a dual-network gel with high strength and high toughness through hydrolysis-reconstruction at 90℃.

[0056] Example 3

[0057] 3.1 Preparation of the dual-network gel matrix:

[0058] Weigh the monomer AMPS (20.72 g, 0.1 mol), crosslinking agent MBA (0.46 g, 0.003 mol), and photoinitiator Irgacure 2959 (0.0224 g, 0.001 mol), dissolve them in 50 mL of distilled water, and polymerize at 60 °C for 24 h after nitrogen purging to remove oxygen, to obtain PAMPS single-network hydrogel. Subsequently, monomer AM (142.16 g, 2 mol), crosslinking agent MBA (0.30836 g, 0.002 mol), and photoinitiator Irgacure2959 initiator (0.448 g, 0.002 mol) were accurately weighed and dissolved in 1000 mL of distilled water. After mixing evenly, the prepared PAMPS gel block was placed in the prepared solution and allowed to swell fully at room temperature for 24 h. After nitrogen purging to remove oxygen, the gel was subjected to UV-initiated polymerization at room temperature for 6 h to obtain a double-network gel formed by acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0059] 3.2 Preparation of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers:

[0060] Polyethylene glycol disuccinate (4.36 g, 10 mmol) with five ethylene glycol units was placed in a 100 mL reaction flask. Dicyclohexylcarbodiimide (DCC) (8.24 g, 40 mmol) and dimethylaminopyridine (DMAP) (0.96 g, 8 mmol) were also added to the flask, and 50.0 mL of 1,4-dioxane was added under a nitrogen atmosphere for dissolution. Subsequently, hydroxyethyl acrylate (EMA) (3.48 g, 30 mmol) was added to the flask, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the byproduct dicyclohexylurea was removed by filtration. The filtrate was collected, concentrated by rotary evaporation, and then added dropwise to ice-cold n-hexane for precipitation. The product was obtained by vacuum drying.

[0061] 3.3 Preparation of multi-network interpenetrating gels and microspheres with temperature-controlled delayed expansion:

[0062] The double-network gel block from step 3.1 was dried in an oven to constant weight. Then, about 2g of the dried sample block was cut off for later use. Subsequently, 16g of the macromonomer and 0.1g of the photoinitiator Irgacure 2959 prepared in step 3.2 were dissolved in 100mL of distilled water. After complete dissolution, the 2g of the dried sample block was placed in the macromolecular prepolymer solution to swell and reach equilibrium. The swollen gel block was then removed and placed in a transparent, sealed container filled with nitrogen to remove oxygen. Subsequently, the macromonomer was polymerized at room temperature using ultraviolet light for 4 hours to obtain a triple-network gel. This gel was dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

[0063] Example 4

[0064] 4.1 Preparation of the dual-network gel matrix:

[0065] Weigh 10.3625 g (0.05 mol) of monomer AMPS, 0.154 g (0.001 mol) of crosslinking agent MBA, and 0.0114 g (0.0005 mol) of initiator ammonium persulfate, dissolve them in 50 mL of distilled water, and polymerize at 80 °C for 6 h after nitrogen purging and oxygen removal to obtain a PAMPS single-network hydrogel. Subsequently, accurately weigh 142.16 g (2 mol) of monomer AM, 0.30836 g (0.002 mol) of crosslinking agent MBA, and 0.456 g (0.002 mol) of initiator ammonium persulfate, dissolve them in 1000 mL of distilled water, mix thoroughly, and place the prepared PAMPS gel block into the prepared solution. Allow it to swell fully at room temperature for 24 h, then purge with nitrogen and oxygen removal before thermally initiating polymerization at 40 °C for 24 h to obtain a double-network hydrogel formed by acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0066] 4.2 Preparation of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers:

[0067] Polyethylene glycol disuccinate (3.04 g, 10 mmol) with two ethylene glycol units was placed in a 100 mL reaction flask. Dicyclohexylcarbodiimide (DCC) (8.24 g, 40 mmol) and dimethylaminopyridine (DMAP) (0.96 g, 8 mmol) were also added to the flask, and the mixture was dissolved in 50.0 mL of dimethyl sulfoxide under a nitrogen atmosphere. Subsequently, hydroxyethyl methacrylate (EMA) (3.9 g, 30 mmol) was added to the flask, and the mixture was stirred at room temperature for 20 h. After the reaction was complete, the byproduct dicyclohexylurea was removed by filtration. The filtrate was collected, concentrated by rotary evaporation, and then added dropwise to cyclohexane for precipitation. The product was obtained by vacuum drying.

[0068] 4.3 Preparation of multi-network interpenetrating gels and microspheres with temperature-controlled delayed expansion:

[0069] The double-network gel block from step 4.1 was dried in an oven to constant weight. Then, about 2g of the dried sample block was cut off for later use. Subsequently, 15g of the macromonomer and 0.15g of the photoinitiator Irgacure 2959 prepared in step 4.2 were dissolved in 100mL of distilled water. After complete dissolution, the 2g of the dried sample block was placed in the macromolecular prepolymer solution to swell and reach equilibrium. The swollen gel block was then removed and placed in a transparent, sealed container filled with nitrogen to remove oxygen. Subsequently, the macromonomer was polymerized at room temperature using ultraviolet light for 4 hours to obtain a triple-network gel. This gel was dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

[0070] Example 5

[0071] 5.1 Preparation of the dual-network gel matrix:

[0072] Weigh 10.3625 g (0.05 mol) of monomer AMPS, 0.154 g (0.001 mol) of crosslinking agent MBA, and 0.0135 g (0.0005 mol) of initiator potassium persulfate, dissolve them in 50 mL of distilled water, and polymerize at 80 °C for 6 h after nitrogen purging and oxygen removal to obtain PAMPS single-network hydrogel. Subsequently, accurately weigh 142.16 g (2 mol) of monomer AM, 0.30836 g (0.002 mol) of crosslinking agent MBA, and 0.54 g (0.002 mol) of initiator potassium persulfate, dissolve them in 1000 mL of distilled water, mix thoroughly, and place the prepared PAMPS gel block into the prepared solution. Allow it to swell fully at room temperature for 24 h, then deoxygenate under nitrogen purging and thermally initiate polymerization at 60 °C for 16 h to obtain a double-network hydrogel formed by acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0073] 5.2 Preparation of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers:

[0074] Polyethylene glycol disuccinate (4.36 g, 10 mmol) with five ethylene glycol units was placed in a 100 mL reaction flask. Dicyclohexylcarbodiimide (DCC) (8.24 g, 40 mmol) and dimethylaminopyridine (DMAP) (0.96 g, 8 mmol) were also added to the flask, and the mixture was dissolved in 50.0 mL of tetrahydrofuran under a nitrogen atmosphere. Subsequently, hydroxyethyl methacrylate (EMA) (3.9 g, 30 mmol) was added to the flask, and the mixture was stirred at room temperature for 20 h. After the reaction was complete, the byproduct dicyclohexylurea was removed by filtration. The filtrate was collected, concentrated by rotary evaporation, and then added dropwise to cyclohexane for precipitation. The product was obtained by vacuum drying.

[0075] 5.3 Preparation of multi-network interpenetrating gels and microspheres with temperature-controlled delayed expansion:

[0076] The double-network gel block from step 5.1 was dried in an oven to constant weight. Then, about 2g of the dried sample block was cut off for later use. Subsequently, 20g of the macromonomer and 0.2g of the photoinitiator Irgacure 2959 prepared in step 5.2 were dissolved in 100mL of distilled water. After complete dissolution, the 2g of the dried sample block was placed in the macromolecular prepolymer solution to swell and reach equilibrium. The swollen gel block was then removed and placed in a transparent, sealed container filled with nitrogen to remove oxygen. Subsequently, the macromonomer was polymerized at room temperature using ultraviolet light for 4 hours to obtain a triple-network gel. This gel was dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

[0077] Therefore, the multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion disclosed in this invention have for the first time achieved in-situ reconstruction of double-network gel particles in a high-temperature environment deep in the formation. This fully leverages the advantages of high strength, high toughness, and high deformability of double-network gel particles, solving the key problems of traditional expanding gel particles being easily broken under pressure and having poor sealing and migration capabilities. It is expected to achieve efficient deep water shut-off and profile control in oilfields and has great application value.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-network interpenetrating gel microsphere with temperature-controlled delayed expansion, characterized in that, Including a triple network gel structure formed by the polymerization of a dual network gel and polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromolecular monomers; Polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomers are polyethylene glycol disuccinate diacrylate or polyethylene glycol disuccinate dimethacrylate, which have the following general structural formula: Where R is H or CH3, and n = 2 to 10.

2. The multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion according to claim 1, characterized in that, The macromonomer is prepared by the following method: using one of hydroxyethyl acrylate and hydroxyethyl methacrylate and polyethylene glycol disuccinate as raw materials, dissolved in an organic solvent, and subjected to esterification reaction at room temperature for 12-24 hours in the presence of catalysts dicyclohexylcarbodiimide and dimethylaminopyridine, followed by filtration, rotary evaporation, precipitation, and drying.

3. The multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion according to claim 2, characterized in that, The molar ratio of one of hydroxyethyl acrylate and hydroxyethyl methacrylate to polyethylene glycol disuccinate is 2–3:1; the number average molecular weight of the polyethylene glycol disuccinate is 300–660, corresponding to 2–10 repeating units of -CH2CH2O-; the organic solvent is dichloromethane, chloroform, 1,4-dioxane, dimethyl sulfoxide, tetrahydrofuran, or N,N'-dimethylformamide; the molar ratio of the catalyst dicyclohexylcarbodiimide to dimethylaminopyridine is 5–10:1, and the molar ratio of dicyclohexylcarbodiimide to polyethylene glycol disuccinate is 3–5:1; the solvent used for precipitation is diethyl ether, petroleum ether, n-hexane, or cyclohexane.

4. The method for preparing a multi-network interpenetrating gel microsphere with temperature-controlled delayed expansion as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of the dual-network gel: Accurately weigh the monomer 2-acrylamido-2-methylpropanesulfonic acid, the crosslinking agent N,N'-methylenebisacrylamide, and the water-soluble initiator, and dissolve them in distilled water to form the first layer of network prepolymer, wherein the concentration of 2-acrylamido-2-methylpropanesulfonic acid is 1-2 mol·L⁻¹. -1 The amounts of N,N'-methylenebisacrylamide and initiator were 2-4 mol% and 0.1-0.3 mol% of the monomer 2-acrylamido-2-methylpropanesulfonic acid, respectively; after nitrogen purging and deoxygenation, poly-2-acrylamido-2-methylpropanesulfonic acid mono-network hydrogel was obtained by UV-initiated or thermally-initiated polymerization. Subsequently, the monomer acrylamide, the crosslinking agent N,N'-methylenebisacrylamide, and the water-soluble initiator were accurately weighed and dissolved in distilled water to form a second-layer network prepolymer, wherein the concentration of acrylamide was 2–4 mol·L⁻¹. -1 The amounts of crosslinking agent N,N'-methylenebisacrylamide and initiator are both 0.1–0.3 mol% of the monomeric acrylamide. Subsequently, the prepared poly(2-acrylamido-2-methylpropanesulfonic acid) single-network hydrogel was placed in the prepared second-layer network prepolymer solution. After swelling at room temperature for 24 hours, nitrogen was used to remove oxygen, and polymerization was initiated by ultraviolet light or heat to obtain a double-network gel matrix formed by the polymerization of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. S2. Preparation of triple network gel: The double network gel block is dried in an oven or freeze-dried in a freeze dryer. Then, the dehydrated polymer block is immersed in an excess of polymerizable, crosslinkable, and temperature-controlled hydrolyzable macromonomer prepolymer solution until swelling equilibrium is reached. The swollen gel block is then placed in a transparent, sealed container, purged with nitrogen to remove oxygen, and the macromonomer is polymerized at room temperature using ultraviolet light to prepare the triple network gel. S3. The triple network gel obtained in S2 is dried and pulverized to obtain multi-network interpenetrating gel microspheres with temperature-controlled delayed expansion.

5. The preparation method according to claim 4, characterized in that, In step S2, the prepolymer solution of the macromonomer is a solution formed by dissolving the macromonomer and the water-soluble initiator in water; wherein the concentration of the macromonomer is 10-30%, the water-soluble initiator accounts for 0.5-2% of the total mass of the macromonomer, and the mass ratio of the macromonomer to the double network gel block is 5-10:

1.

6. The preparation method according to claim 4, characterized in that, The water-soluble initiator is one or more of the following: thermal initiator azobisisobutylammonium hydrochloride, ammonium persulfate, potassium persulfate, or photoinitiator Irgacure 2959.

7. The preparation method according to claim 4, characterized in that, The ultraviolet light-initiated polymerization temperature is room temperature, and the polymerization time is 2-6 hours; the thermally initiated polymerization temperature is 40-80°C, and the polymerization time is 4-24 hours.

8. The application of the temperature-controlled delayed expansion multi-network interpenetrating gel microspheres as described in claim 1 in the preparation of oilfield profile control and water shut-off materials, characterized in that, The microspheres expand slowly at room temperature due to the cross-linking and binding of molecular chains, and have high injectability. When the formation temperature is >60℃, the third cross-linked network undergoes hydrolysis and expansion, and can be reconstructed in situ to form high-strength, high-toughness, and high-deformability double-network gel plugging particles, which are suitable for deep water shut-off and profile control in oilfields.

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