Hydroponic gels, their preparation methods and applications

Abstract

This invention belongs to the field of polymer hydrogels, specifically relating to a hydroblocking gel, its preparation method, and its application. The hydroblocking gel comprises 110 parts of acrylamide monomer, 5-35 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 parts of crosslinking agent, 0.15 parts of initiator, 2-6 parts of functional additives (dry weight), and water. The amount of water added makes the final hydroblocking gel 400 parts. Tannic acid can provide multiple bonding sites and various interactions, such as hydrogen bonds, ionic bonds, coordination bonds, and hydrophobic interactions. Adding TA to the polymer solution of the hydrogel enhances the physical properties of the hydrogel through interactions with its functional groups. Using tannic acid and acrylamide as base materials, the method is inexpensive, has good water solubility, requires low concentrations, does not require nitrogen protection during the reaction, and has good on-site adaptability.

Description

Technical Field

[0001] This invention belongs to the field of polymer hydrogels, specifically relating to a hydrogel with a blocking effect, its preparation method, and its application. Background Technology

[0002] Currently, 60% of my country's newly added oil and gas reserves come from deep formations, with deep carbonate oil and gas reservoirs being the main battleground for increasing crude oil reserves and production. However, due to the variable channel scale (micrometers to meters), complex oil-water relationships, enormous water energy, and the "five extremely high" characteristics of temperature, salinity, calcium and magnesium ion content, depth, and pressure in deep carbonate oil and gas reservoirs, effective water control is crucial for the efficient development of these reservoirs. Traditional expanded particle products are generally made from monomers such as polyacrylamide through polymerization, drying, and pulverization under the action of crosslinking agents and initiators. After absorbing liquid in the formation, they expand in volume by tens to hundreds of times, achieving the purpose of water shut-off.

[0003] In existing technologies, some studies have attempted to introduce dynamic covalent bonds (such as hydrogen bonds and ionic bonds) to achieve limited self-healing, but these technologies suffer from problems such as low strength after water absorption and swelling, easy breakage under shear during long-distance transport, insufficient temperature and salt resistance, and limited functionality. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydroblocking gel, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A water-blocking gel comprises the following components in parts by weight: 110 parts acrylamide monomer, 5-35 parts tannic acid, 5 parts polyvinyl alcohol, 0.2 parts crosslinking agent, 0.15 parts initiator, 2-6 parts functional additives (dry weight), and water, wherein the amount of water added makes the final water-blocking gel 400 parts.

[0007] Preferably, the composition includes the following components by weight: 110 parts acrylamide monomer, 10-15 parts tannic acid, 5 parts polyvinyl alcohol, 0.2 parts crosslinking agent, 0.15 parts initiator, 2-3 parts functional additives (dry weight), and water, wherein the amount of water added makes the final hydroblocking gel 400 parts.

[0008] Preferably, the functional additive is one or a mixture of boron nitride, modified boron nitride, nano zirconium sol, nano silica sol, nano titanium dioxide sol, phenylboronic acid, and modified phenylboronic acid.

[0009] The modified boron nitride comprises aldehyde-based cellulose nanofibers in the form of amino boron nitride.

[0010] The dry weight ratio of the aldehyde-based cellulose nanofibers to the amino boron nitride is (1-5):1.

[0011] The modified boron nitride is prepared as follows: aldehyde cellulose nanofibers and amino boron nitride are placed in a container and stirred until the amino boron nitride powder is coated with aldehyde cellulose nanofibers. Deionized water is added and the mixture is dispersed to obtain an aldehyde cellulose-amino boron nitride DACNF-AFBN dispersion, which serves as the functional additive.

[0012] The mass ratio of the functional additive to the acrylamide monomer is 30:110.

[0013] The acrylamide monomers mentioned are at least one selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hydroxymethylacrylamide, and dimethylaminoethyl methacrylate.

[0014] Preferably, the acrylamide monomer is a mixture of acrylamide and N,N-dimethylacrylamide; preferably, the ratio of the two is 10:1.

[0015] The crosslinking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylenebismaleimide, and pentaerythritol triacrylate;

[0016] Preferably, the crosslinking agent is a mixture of N,N'-methylenebisacrylamide and polyethylene glycol (400) diacrylate, and preferably, the ratio of the two is 1:1;

[0017] The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoyl ether, and acetophenone derivatives; preferably azobisisobutyramidine.

[0018] The present invention also includes a method for preparing the aforementioned water-blocking gel, comprising the following steps: weighing each component and mixing them, stirring until dissolved, and heating to the polymerization temperature to react and obtain the water-blocking gel.

[0019] The present invention also includes an application of the aforementioned water-blocking gel, applied to water plugging in oil fields.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] Tannic acid (TA) is a weakly acidic polyphenol compound. It contains five pyrogallol and five catechol groups, providing multiple bonding sites and various interactions, such as hydrogen bonds, ionic bonds, coordinate bonds, and hydrophobic interactions. Adding TA to the polymer solution of a hydrogel enhances its physical properties through interactions with its functional groups. Using tannic acid and acrylamide as base materials offers advantages such as low cost, good water solubility, low concentration requirements, and no need for nitrogen protection during the reaction, making it suitable for on-site application.

[0022] As a preferred form, cellulose nanofibers are prepared from renewable natural fibers, ranging in length from hundreds of nanometers to tens of micrometers and in diameter from 0.1 to 100 nm. They possess high modulus, a large specific surface area, excellent mechanical properties, and a large aspect ratio. Aminoboron nitride provides ultra-high temperature stability and shear resistance. Combining these two as a functional additive in hydrogels allows them to maintain excellent heat dissipation characteristics and stability at 130°C for extended periods. Simultaneously, by combining with tannic acid, they form a three-dimensional cross-linked network within the system, exhibiting highly efficient self-healing capabilities. Attached Figure Description

[0023] Figure 1 The infrared chromatogram of the tannic acid-based hydroblocking gel prepared in Example 1 is shown below.

[0024] Figure 2 The tensile strain-stress curves of hydroblocking gels with different contents of tannic acid prepared in Example 1 are shown.

[0025] Figure 3 The 80% compressive strain-stress curves of the tannic acid-based hydroblocking gels with different contents prepared in Example 1 are shown.

[0026] Figure 4 The tensile strain-stress curves of the water-blocking gels with different functional additives prepared in Example 3 are shown.

[0027] Figure 5 The 80% compressive strain-stress curves of the water-blocking gels with different functional additives prepared in Example 3 are shown.

[0028] Figure 6 This is a schematic diagram of the TG of the water-blocking gels with different functional additives prepared in Example 3;

[0029] Figure 7 A schematic diagram of the DTG of the water-blocking gels with different functional additives prepared in Example 3;

[0030] Figure 8The recrosslinking conversion rate of the water-blocking gels with different functional additives prepared in Example 3 was determined by aging at 130°C for 30 days in self-made brine (mineralization of 200,000 mg / L, calcium and magnesium ions of 10,000 mg / L each). Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0032] The commercially available sources and types of materials used in this application are as follows: Aldehyde cellulose CNF was provided by Tianjin Wood Elf Biotechnology Co., Ltd. (Tianjin, China). Tannic acid (TA) was purchased from Ningbo Dingyuan Food Technology Co., Ltd. Acrylamide (AM), N,N-dimethylacrylamide (DMA), N,N'-methylenediacrylamide (MBA), and polyethylene glycol (400) diacrylate (PEG400DA) were all purchased from Sinopharm. Polyvinyl alcohol (PVA, alcohol-soluble 2488) was purchased from Shanghai Chenqi Chemical Technology Co., Ltd. Boron nitride and aminoboron nitride were purchased from Shanghai Zhongye New Materials Co., Ltd. Nano-zirconium sol, nano-silica sol, and nano-titanium dioxide sol were purchased from Dezhou Jinghuo Technology Glass Co., Ltd. Benzylboronic acid and 3-aminophenylboronic acid were purchased from Shanghai Haohong Biomedical Technology Co., Ltd. The photoinitiator azobisisobutylamidine was purchased from Shanghai Yinchang New Materials Co., Ltd.

[0033] Example 1: A method for preparing a tannic acid-based self-healing hydro-blocking gel, comprising the following steps: weighing 0 g, 5 g, 10 g, 15 g, 20 g, 25 g, 30 g, 35 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 10 g of N,N-dimethylacrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 0.15 g of initiator azobisisobutyramidine, and water, adding water to make the total amount of hydro-blocking gel 400 g, mixing, stirring to dissolve, adjusting the reaction temperature to 85°C, and obtaining a tannic acid-based self-healing hydro-blocking gel;

[0034] Performance evaluation of tannic acid-based self-healing hydrogels:

[0035] Preparation and mechanical properties of tannic acid-based self-healing hydrogels: The infrared spectrum (TA-gel) of the tannic acid-based self-healing hydrogel (15g tannic acid) prepared in Example 1 is shown below. Figure 1 As shown, the results prove that tannic acid has been successfully added to the hydrogel.

[0036] The mechanical properties of the self-healing hydrogels with different contents of tannic acid groups prepared in Example 1 were tested. Figure 2The tensile strain-stress curves of hydroblocking gels with different contents of tannic acid prepared in Example 1 are shown. Figure 3 The 80% compressive strain-stress curves of the tannic acid-based hydroblocking gels with different contents prepared in Example 1 are shown in Table 1.

[0037] Table 1

[0038]

[0039] As shown in Table 1, the maximum tensile strain of 98.82 kPa was achieved when the TA addition was 15 g, which is 1.16 times that of the control group (0 g TA, 85.43 kPa). When higher TA loadings (20 g TA and 35 g TA) were used, the tensile strength began to decrease, from 98.82 kPa (15 g TA) to 57.94 kPa (35 g TA). This is likely because an appropriate amount of TA can form hydrogen bonds with the polymer chains, enhancing the forces between the molecular chains and thus increasing the tensile strength of the gel. The compressive strength of hydrogels with added TA is generally lower than that of hydrogels without added TA. Furthermore, increasing the TA loading led to a decrease in compressive strength, from 1789.62 kPa (0 g TA) to 89.15 kPa (30 g TA). 5% TA and 15% TA still exhibited higher compressive strengths than other samples (except 0 g TA) (2180.92 kPa and 253.67 kPa).

[0040] The acrylamide monomer is at least one selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hydroxymethylacrylamide, and dimethylaminoethyl methacrylate; preferably, the acrylamide monomer is a mixture of acrylamide and N,N-dimethylacrylamide; preferably, the ratio of the two is 10:1.

[0041] The crosslinking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylenebismaleimide, and pentaerythritol triacrylate;

[0042] Preferably, the crosslinking agent is a mixture of N,N'-methylenebisacrylamide and polyethylene glycol (400) diacrylate, and preferably, the ratio of the two is 1:1;

[0043] The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoyl ether, and acetophenone derivatives; preferably azobisisobutyramidine.

[0044] Example 2: Preparation of functional additives: Aldehyde cellulose nanofibers with oven-dry weights of 1 g, 2 g, 3 g, 4 g, and 5 g, and 1 g of aminoboron nitride were weighed into containers and stirred until the aminoboron nitride powder was coated with the aldehyde cellulose nanofibers. Deionized water was added and the mixture was dispersed to obtain 30 g of a series of aldehyde cellulose nanofibers with aminoboron nitride DACNF-AFBN dispersions (dry weights of 2 g, 3 g, 4 g, 5 g, and 6 g, respectively). Here, "-" represents the formation of a new chemical bond (Schiff base bond -N—C-).

[0045] Example 3: The series of DACNF-AFBN obtained in Example 2 was used to prepare a water-blocking gel; 15 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 10 g of N,N-dimethylacrylamide, 30 g of the series of DACNF-AFBN prepared in Example 2, 0.15 g of the initiator azobisisobutyramidine, and water were weighed. The amount of water added was such that the total amount of water-blocking gel was 400 g. The mixture was stirred and dissolved, and the reaction temperature was adjusted to 85°C to obtain a tannic acid-based self-healing water-blocking gel.

[0046] The tannic acid-based self-healing hydrogel prepared in Example 3 was subjected to mechanical property testing. Figure 4 Tensile strain-stress curves of water-blocking gels with different functional additives; Figure 5 The 80% compressive strain-stress curves of the hydroblocking gels with different functional additives are shown in Table 2.

[0047] Table 2

[0048]

[0049] Table 2 shows that the hydrogel with added functional additives has better tensile strength than the hydrogel without additives. This is because cellulose and aminoboron nitride undergo a Schiff base reaction, forming imine bonds (-C--N-). The hydrogel with added functional additives has significantly worse tensile strain than the hydrogel without additives (TA gel, 1269%). This may be because aminoboron nitride itself has high strength and can effectively hinder matrix deformation, thus reducing strain capacity. When DACNF:AFBN = 5:1, the hydrogel's toughness is somewhat reduced, but its tensile strength is 211% (373.33 kPa) of the 1:1 (180.97 kPa) hydrogel. This is because the hydroxyl and carboxyl groups in the hydrogel matrix form more hydrogen bonds with the amino groups in the matrix, enabling the hydrogel to withstand greater external forces and increasing tensile strength.

[0050] The compressive strength of the hydrogel gradually increased with the increase of the proportion of functional additives. The highest compressive strength (1570.61 kPa) was observed when the ratio of DACNF:AFBN was 5:1, approximately 4.13 times that of the control group (TA gel, 384.16 kPa). This is because aminoboron nitride can be uniformly dispersed in the monomers, avoiding its aggregation and effectively reducing the number of voids in the hydrogel. The smaller pore size of the hydrogel leads to increased compressive strength.

[0051] Thermogravimetric analysis was performed on the tannic acid-based self-healing hydrogel prepared in Example 3. Figure 6-7 As shown: Figure 6 The thermogravimetric analysis (TG) curves show that the initial decomposition temperatures of the hydrogels with added functional additives are not significantly different. However, the hydrogel with a DACNF:AFBN ratio of 5:1 exhibits the highest percentage of remaining weight at higher temperatures compared to other ratios. This indicates that a higher proportion of functional additives facilitates the formation of a cross-linked network primarily composed of hydrogen and chemical bonds, resulting in greater mass retention and better thermal stability at high temperatures. (The TG curves show...) Figure 7 Compared to hydrogels without additives (TA gel, 395℃), the addition of functional additives can increase the maximum peak temperature (>400℃). This is because: 1) aminoboron nitride itself has thermal stability; 2) the functional additive DACNF-AFBN can form hydrogen bonds, van der Waals forces, and other interactions with groups in the hydrogel. These interactions restrict the movement of molecular chain segments, requiring higher temperatures for drastic thermal degradation, thus increasing the maximum peak temperature. Furthermore, the maximum decomposition temperatures (~405℃) of all hydrogels with added functional additives are essentially the same, indicating that a cross-linking reaction occurs between the added functional additives and the polymer, which can improve the thermal stability of the hydrogel.

[0052] The tannic acid-based self-healing hydrogel prepared in Example 3 was subjected to a 30-day aging test, such as... Figure 8 As shown, the results indicate that the self-healing conversion rate of hydrogels with different proportions varies after 30 days of aging, but the overall values ​​are relatively similar. This suggests that within the tested proportion range, the amount of functional additives has no significant effect on the self-healing conversion rate of the hydrogel.

[0053] Example 4: Weigh 15 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 10 g of N,N-dimethylacrylamide, 30 g of nano-zirconium sol (dry weight 3 g), 0.15 g of initiator azobisisobutylamidine, and water. Add water to make the total amount of water-blocking gel 400 g. Mix, stir to dissolve, and adjust the reaction temperature to 85°C to obtain tannic acid-based self-healing water-blocking gel.

[0054] Example 5: Preparation of the functional additive DACNF@BN: 5 g of aldehyde-based cellulose nanofibers and 1 g of boron nitride were weighed into a container and stirred until the boron nitride powder was coated with the aldehyde-based cellulose nanofibers. Deionized water was added and the mixture was dispersed to obtain 30 g of a series of aldehyde-based cellulose-coated aminoboron nitride DACNF@BN dispersions (dry weight 6 g). Here, "@" represents physical coating without the formation of new chemical bonds.

[0055] The obtained DACNF@BN was used to prepare a water-blocking gel. 15 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 10 g of N,N-dimethylacrylamide, 30 g of DACNF@BN, 0.15 g of initiator azobisisobutylamidine and water were weighed. The amount of water added was such that the total amount of water-blocking gel was 400 g. The mixture was mixed, stirred and dissolved, and the reaction temperature was adjusted to 85℃ to obtain a tannic acid-based self-healing water-blocking gel.

[0056] Example 6: Weigh 15 g tannic acid, 5 g polyvinyl alcohol, 100 g acrylamide, 0.1 g N,N'-methylenebisacrylamide, 0.1 g polyethylene glycol (400) diacrylate, 10 g N,N-dimethylacrylamide, 30 g nano silica sol (dry weight 3 g), 0.15 g initiator azobisisobutylamidine, and water. Add water to make the total amount of water-blocking gel 400 g. Mix, stir to dissolve, and adjust the reaction temperature to 85°C to obtain tannic acid-based self-healing water-blocking gel.

[0057] Example 7: Weigh 15 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 10 g of N,N-dimethylacrylamide, 30 g of nano titanium dioxide sol (dry weight 3 g), 0.15 g of initiator azobisisobutylamidine, and water. Add water to make the total amount of water-blocking gel 400 g. Mix, stir to dissolve, and adjust the reaction temperature to 85°C to obtain tannic acid-based self-healing water-blocking gel.

[0058] Example 8: Weigh 15 g tannic acid, 5 g polyvinyl alcohol, 100 g acrylamide, 0.1 g N,N'-methylenebisacrylamide, 0.1 g polyethylene glycol (400) diacrylate, 10 g N,N-dimethylacrylamide, 3 g phenylboronic acid, 0.15 g initiator azobisisobutylamidine, and water. Add water to make the total amount of water-blocking gel 400 g. Mix, stir to dissolve, and adjust the reaction temperature to 85°C to obtain tannic acid-based self-healing water-blocking gel.

[0059] Example 9: Weigh 15 g of tannic acid, 5 g of polyvinyl alcohol, 100 g of acrylamide, 0.1 g of N,N'-methylenebisacrylamide, 0.1 g of polyethylene glycol (400) diacrylate, 10 g of N,N-dimethylacrylamide, 3 g of 3-aminophenylboronic acid, 0.15 g of initiator azobisisobutylamidine, and water. Add water to make the total amount of water-blocking gel 400 g. Mix, stir to dissolve, and adjust the reaction temperature to 85°C to obtain tannic acid-based self-healing water-blocking gel.

[0060] The mechanical properties of the freshly prepared tannic acid-based self-healing hydrogels in Examples 3-9 were tested, and the results are shown in Table 3.

[0061] Table 3

[0062]

[0063] The tannic acid-based self-healing hydrogels prepared in Examples 3-9 were dried, ground into powder, and passed through a 40-mesh sieve to obtain pre-gel particles. 7 g of the pre-gel particles and 100 ml of 20% saline solution (calcium and magnesium ions, 10000 mg / L each) were weighed into a reaction vessel and placed in a 130℃ oven for 7 days. The self-healing gels were then subjected to an 80% compression test, and the results are shown in Figure 4.

[0064] Table 4

[0065]

[0066] It can be seen that the mechanical properties of hydrogels with added functional additives are improved. After 7 days of high temperature and high salt environment, the self-healing gel with added functional additives does not collapse and still has good compressive strength. Its application in water-blocking gels is of great significance to improving the success rate of crack water blocking.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hydroblocking gel, characterized in that, The product comprises the following components by weight: 110 parts acrylamide monomer, 5-35 parts tannic acid, 5 parts polyvinyl alcohol, 0.2 parts crosslinking agent, 0.15 parts initiator, 2-6 parts functional additives by dry weight, and water, wherein the amount of water added makes the final amount of the water-blocking gel 400 parts. The functional additives mentioned are one or a mixture of boron nitride, modified boron nitride, nano zirconium sol, nano silica sol, nano titanium dioxide sol, and phenylboronic acid; The crosslinking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylenebismaleimide, and pentaerythritol triacrylate; The modified boron nitride is prepared as follows: aldehyde cellulose nanofibers and amino boron nitride are placed in a container and stirred until the amino boron nitride powder is coated by the aldehyde cellulose nanofibers. Deionized water is added and dispersed to obtain an aldehyde cellulose-amino boron nitride DACNF-AFBN dispersion, which is the modified boron nitride. The dry weight ratio of the aldehyde-based cellulose nanofibers to the amino boron nitride is (1-5):

1.

2. The hydroponic gel according to claim 1, characterized in that, The product comprises the following components by weight: 110 parts acrylamide monomer, 15 parts tannic acid, 5 parts polyvinyl alcohol, 0.2 parts crosslinking agent, 0.15 parts initiator, 2-3 parts functional additives (dry weight), and water, wherein the amount of water added makes the final hydroblocking gel 400 parts.

3. The hydroponic gel according to claim 1, characterized in that, The acrylamide monomers mentioned are at least one selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hydroxymethylacrylamide, and dimethylaminoethyl methacrylate. The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoyl ether, and acetophenone derivatives.

4. A method for preparing the hydroblocking gel according to any one of claims 1-3, characterized in that, The process includes the following steps: weighing each component and mixing them, stirring until dissolved, and heating to the polymerization temperature to react and obtain the water-blocking gel.

5. An application of the water-blocking gel according to any one of claims 1-3, characterized in that, It is used for water shut-off in oil fields.

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