Water plugging gel as well as preparation method and application thereof

Abstract

The invention belongs to the field of polymer hydrogel, and particularly relates to water plugging gel and a preparation method and application thereof.The water plugging gel is prepared from 110 parts of acrylamide monomer, 5-35 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 part of cross-linking agent, 0.15 part of initiator, 2-6 parts of functional additive dry weight and water, and the final water plugging gel is 400 parts through the addition amount of water. The tannic acid can provide multiple key sites and multiple interactions, such as hydrogen bonds, ionic bonds, coordination bonds, and hydrophobic interactions. TA is added into a polymer solution of the hydrogel, the physical property of the hydrogel can be enhanced through interaction with functional groups of TA, tannic acid and acrylamide serve as base materials, the price is low, water solubility is good, the use concentration is low, nitrogen protection is not needed in the reaction process, and good field adaptability is achieved.

Description

Technical Field

[0001] The invention belongs to the field of polymer hydrogels, and particularly relates to a water-blocking gel and a preparation method and application thereof. Background Art

[0002] Currently, 60% of my country's newly added oil and gas reserves come from deep formations. Deep carbonate reservoirs are the primary frontier for increasing crude oil reserves and production. However, due to the variable channel scales (micrometers to meters), complex oil-water relationships, enormous water energy, and extremely high temperatures, salinity, calcium and magnesium ion content, depth, and pressure, effective water management is crucial for efficient reservoir development. Traditional expandable granular products are typically made from monomers such as polyacrylamide, polymerized with a crosslinker and initiator, dried, and pulverized. After absorbing fluid from the formation, their volume expands dozens to hundreds of times, achieving the desired water blocking effect.

[0003] In the existing technology, some studies have attempted to introduce dynamic covalent bonds (such as hydrogen bonds and ionic bonds) to achieve limited self-repair. However, there are problems such as low strength after water absorption and expansion, easy breakage due to shearing during long-distance transportation, insufficient temperature and salt resistance, and single functionality. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a water-blocking gel and a preparation method and application thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A water-blocking gel comprises the following components by weight: 110 parts of acrylamide monomer, 5-35 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 parts of a cross-linking agent, 0.15 parts of an initiator, 2-6 parts by dry weight of a functional additive, and water. The amount of water added is such that the final weight of the water-blocking gel is 400 parts.

[0006] Preferably, the composition comprises the following components by weight: 110 parts of acrylamide monomer, 10-15 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 parts of crosslinking agent, 0.15 parts of initiator, 2-3 parts by dry weight of functional additives and water. The amount of water added is such that the final weight of the water-blocking gel is 400 parts.

[0007] 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, phenylboric acid and modified phenylboric acid.

[0008] The modified boron nitride comprises aldehyde-based cellulose nanofiber and amino-based boron nitride.

[0009] The mass ratio of the absolute dry mass of the aldehyde-based cellulose nanofibers to the amino boron nitride is (1-5):1.

[0010] The modified boron nitride is prepared by the following method: aldehyde cellulose nanofibers and amino boron nitride are placed in a container and stirred until the amino boron nitride powder is wrapped by the aldehyde cellulose nanofibers, deionized water is added and dispersed to obtain an aldehyde cellulose-amino boron nitride DACNF-AFBN dispersion as the functional additive.

[0011] The mass ratio of the functional additive to the acrylamide monomer is 30:110.

[0012] The acrylamide monomer is at least one of acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, hydroxymethyl acrylamide 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; The cross-linking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylene bismaleimide, and pentaerythritol triacrylate; Preferably, the cross-linking agent is a mixture of N,N'-methylenebisacrylamide and polyethylene glycol (400) diacrylate, preferably, the ratio of the two is 1:1; The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoin ether, and acetophenone derivatives; preferably azobisisobutyramidine.

[0013] The present invention also includes a method for preparing the water-blocking gel, comprising the following steps: weighing the components and mixing them, stirring until dissolved, and heating to a polymerization temperature to react to obtain the water-blocking gel.

[0014] The present invention also includes an application of the water plugging gel, which is applied to water plugging in oil fields.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Tannic acid (TA) is a weakly acidic polyphenolic compound. The presence of five pyrogallol and five catechol groups in tannic acid provides multiple bonding sites and various interactions, such as hydrogen, ionic, coordination, and hydrophobic bonds. Adding TA to the polymer solution of the hydrogel enhances the hydrogel's physical properties through interactions with TA's functional groups. Tannic acid and acrylamide are used as the base material, offering low cost, good water solubility, and low working concentration. Nitrogen protection is not required during the reaction, making the hydrogel highly adaptable to field applications.

[0016] Cellulose nanofibers, a preferred form of the material, are made from renewable natural fibers. These ultra-fine fibers range in length from a few hundred nanometers to tens of microns, with diameters of 0.1-100 nm. They exhibit 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. When combined as a functional additive in a hydrogel, these two components maintain excellent heat dissipation and stability at temperatures of 130°C. Furthermore, they combine with tannic acid to form a three-dimensional cross-linked network within the system, resulting in efficient self-healing capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the infrared chromatogram of the tannic acid-based water-blocking gel prepared in Example 1; Figure 2 The tensile strain stress curves of the tannic acid-based water-blocking gels with different contents prepared in Example 1 are shown; Figure 3 80% compressive strain stress curves of tannic acid-based water-blocking gels with different contents prepared in Example 1; Figure 4 The tensile strain stress curves of the water-blocking gel with different functional additives prepared in Example 3; Figure 5 80% compressive strain stress curves of the water-blocking gels with different functional additives prepared in Example 3; Figure 6 TG schematic diagram of the water-blocking gel with different functional additives prepared in Example 3; Figure 7 Schematic diagram of DTG water-blocking gel with different functional additives prepared in Example 3; Figure 8 The re-crosslinking conversion rate of the water-blocking gel with different functional additives prepared in Example 3 after aging at 130°C for 30 days in homemade brine (mineralization of 200,000 mg / L, calcium ions and magnesium ions of 10,000 mg / L). DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and the best embodiments.

[0019] Materials used in this application were purchased from commercial sources and models: Cellulose aldehyde (CNF) was provided by Tianjin Mujingling Biotechnology Co., Ltd. (Tianjin, China). Tannic acid (TA) was purchased from Ningbo Dingyuan Food Technology Co., Ltd., and acrylamide (AM), N,N-dimethylacrylamide (DMA), N,N'-methylenebisacrylamide (MBA), and polyethylene glycol (400) diacrylate (PEG400DA) were 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 MCC New Materials Co., Ltd. Nanozirconium sol, nanosilica sol, and nanotitanium dioxide sol were purchased from Dezhou Jinghuo Technology Glass Co., Ltd. Phenylboric acid and 3-aminophenylboronic acid were purchased from Shanghai Haohong Biomedicine Technology Co., Ltd. The photoinitiator azobisisobutylamidine was purchased from Shanghai Yinchang New Materials Co., Ltd.

[0020] Example 1: A method for preparing a tannic acid-based self-repairable water-blocking gel, comprising the following steps: weighing 0 g, 5 g, 10 g, 15 g, 20 g, 25 g, 30 g, and 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 azobisisobutylamidine, and water, respectively, adding water in an amount such that the total amount of the water-blocking gel is 400 g, mixing, stirring to dissolve, and adjusting the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel; Performance evaluation of tannic acid-based self-healing hydrogel: Preparation and mechanical determination of tannic acid-based self-healing hydrogel: The infrared spectrum (TA-gel) of the tannic acid-based self-healing hydrogel (15 g tannic acid) prepared in Example 1 is as follows: Figure 1 As shown, the results demonstrated that tannic acid had been successfully incorporated into the hydrogel.

[0021] The mechanical properties of the self-repairing hydrogels with different tannic acid content prepared in Example 1 were tested. Figure 2 The tensile strain stress curves of the tannic acid-based water-blocking gels with different contents prepared in Example 1 are shown; Figure 3 The 80% compressive strain stress curves of the tannic acid-based water-blocking gels with different contents prepared in Example 1 are shown in Table 1. Table 1

[0022] Table 1 shows that when 15 g of TA was added, the maximum tensile strain reached 98.82 kPa, 1.16 times that of the control (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, falling from 98.82 kPa (15 g TA) to 57.94 kPa (35 g TA). This is likely due to the fact that an appropriate amount of TA can form hydrogen bonds with polymer chains, strengthening the forces between the molecular chains and thereby enhancing the tensile strength of the gel. The compressive strength of hydrogels containing TA is generally lower than that of hydrogels without TA. Furthermore, increasing TA loading resulted in a decrease in compressive strength, from 1789.62 kPa (0 g TA) to 89.15 kPa (30 g TA). The 5% and 15% TA samples still exhibited higher compressive strengths (2180.92 kPa and 253.67 kPa) than the other samples (except 0 g TA).

[0023] The acrylamide monomer is at least one of acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, hydroxymethyl acrylamide 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; The cross-linking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylene bismaleimide, and pentaerythritol triacrylate; Preferably, the cross-linking agent is a mixture of N,N'-methylenebisacrylamide and polyethylene glycol (400) diacrylate, preferably, the ratio of the two is 1:1; The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoin ether, and acetophenone derivatives; preferably azobisisobutyramidine.

[0024] Example 2: Preparation of Functional Additives: 1 g, 2 g, 3 g, 4 g, and 5 g of aldehyde-based cellulose nanofibers and 1 g of aminoboron nitride were weighed in a container, respectively, and stirred until the aminoboron nitride powder was coated with the aldehyde-based cellulose nanofibers. Deionized water was then added and dispersed to obtain 30 g of a series of aldehyde-based cellulose-aminoboron nitride DACNF-AFBN dispersions (dry weights of 2 g, 3 g, 4 g, 5 g, and 6 g, respectively). The "-" indicates the formation of a new chemical bond (Schiff base bond -N—C-).

[0025] 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, and 30 g of the series of DACNF-AFBN prepared in Example 2, 0.15 g of initiator azobisisobutylamidine and water were weighed, and the amount of water added was such that the total amount of the water-blocking gel was 400 g. The mixture was mixed, stirred and dissolved, and the reaction temperature was adjusted to 85°C to obtain a tannic acid-based self-repairable water-blocking gel; The tannic acid-based self-repairable hydrogel prepared in Example 3 was subjected to mechanical property tests. Figure 4 The tensile strain-stress curves of water-blocking gels with different functional additives; Figure 5 The 80% compressive strain stress curves of water blocking gels with different functional additives are shown in Table 2. Table 2

[0026] Table 2 shows that hydrogels with functional additives exhibit greater tensile strength than those without. This is due to a Schiff base reaction between cellulose and amino-boron nitride, forming imine bonds (-C--N-). The tensile strain of hydrogels with functional additives is significantly lower than that of hydrogels without additives (TA gel, 1269%). This is likely due to the inherent strength of amino-boron nitride, which effectively hinders matrix deformation, resulting in reduced strain capacity. When the DACNF:AFBN ratio is 5:1, the hydrogel loses some toughness, but its tensile strength reaches 373.33 kPa, 211% of the 1:1 ratio (180.97 kPa). 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 improving its tensile strength.

[0027] The compressive strength of the hydrogel gradually increases with increasing ratios of the functional additives. The highest compressive strength (1570.61 kPa) was achieved 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 the amino-boron nitride can be evenly dispersed throughout the monomer, preventing aggregation and effectively reducing the number of voids in the hydrogel. This reduces the pore size of the hydrogel, leading to increased compressive strength.

[0028] The tannic acid-based self-repairable hydrogel prepared in Example 3 was subjected to thermogravimetric analysis. Figure 6-7 As shown: Figure 6Thermogravimetric analysis (TG) curves show that the initial decomposition temperatures of the hydrogels with functional additives are similar, and the hydrogel with DACNF:AFBN=5:1 has the highest residual weight percentage at higher temperatures among the hydrogels with other ratios. This indicates that the higher the ratio of functional additives, the easier it is to form a cross-linked network mainly composed of hydrogen bonds and chemical bonds, and the more mass it can maintain at high temperatures, and the better the thermal stability. Figure 7 Compared to the unadditive hydrogel (TA gel, 395°C), the addition of functional additives can increase the maximum peak temperature (>400°C). This is because: 1) aminoboron nitride is inherently thermally stable; and 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 segments, requiring higher temperatures to induce drastic thermal degradation of the molecular segments, leading to an increase in the maximum peak temperature. Furthermore, the maximum decomposition temperature (~405°C) of all hydrogels containing functional additives is essentially the same, indicating that a cross-linking reaction occurs between the added functional additive and the polymer, improving the thermal stability of the hydrogel.

[0029] The tannic acid-based self-repairing hydrogel prepared in Example 3 was subjected to a 30-day aging test. Figure 8 As shown in the figure, the results show that after 30 days of aging, the self-healing conversion rate of hydrogels with different ratios varies to some extent, but the overall values are relatively close. This shows that within the tested ratio range, the amount of functional additives has no significant effect on the self-healing conversion rate of hydrogels.

[0030] 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 in an amount that makes the total amount of water-blocking gel 400 g. Mix and stir to dissolve. Adjust the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel.

[0031] Example 5: Preparation of the Functional Additive DACNF@BN: 5 g of aldehyde-encapsulated cellulose nanofibers and 1 g of boron nitride (BN) were weighed and placed in a container. Stirring was performed until the BN powder was encapsulated by the aldehyde-encapsulated cellulose nanofibers. Deionized water was then added and dispersed to obtain 30 g of a 6 g dry weight DACNF@BN dispersion of aldehyde-encapsulated aminoboron nitride. The "@" indicates physical encapsulation; no new chemical bonds were formed.

[0032] The obtained DACNF@BN was used to prepare water-blocking gel; 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 DACNF@BN, 0.15 g 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 and stirred to dissolve. The reaction temperature was adjusted to 85 °C to obtain a tannic acid-based self-repairable water-blocking gel.

[0033] Example 6: 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-silica sol (dry weight 3 g), 0.15 g of initiator azobisisobutylamidine and water. Add water in an amount that makes the total amount of water-blocking gel 400 g. Mix and stir to dissolve. Adjust the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel.

[0034] 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 in an amount that makes the total amount of water-blocking gel 400 g. Mix and stir to dissolve. Adjust the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel.

[0035] Example 8: 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 phenylboric acid, 0.15 g of initiator azobisisobutylamidine and water. Add water in an amount that makes the total amount of water-blocking gel 400 g. Mix and stir to dissolve. Adjust the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel.

[0036] 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 in an amount that makes the total amount of water-blocking gel 400 g. Mix and stir to dissolve. Adjust the reaction temperature to 85°C to obtain a tannic acid-based self-repairable water-blocking gel.

[0037] The tannic acid-based self-repairable hydrogel freshly prepared in Example 3-9 was subjected to mechanical property testing, and the results are shown in Table 3; Table 3

[0038] The tannic acid-based self-healing hydrogel prepared in Example 3-9 was dried and ground into powder, then passed through a 40-mesh sieve to obtain preformed gel particles. 7 g of preformed gel particles and 100 ml of 20% saline (10,000 mg / L each of calcium and magnesium ions) were weighed into a reaction kettle and placed in a 130°C oven. After 7 days, the self-healing gel was removed and subjected to an 80% compression test. The results are shown in Figure 4 below. Table 4

[0039] It can be seen that the mechanical properties of the hydrogels with added functional additives have been improved. After 7 days in a high-temperature and high-salt environment, the self-healing gel with added functional additives did not collapse internally and still had good compressive strength. Its application in water-plugging gels is of great significance to improving the success rate of crack water plugging.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A water blocking gel, characterized in that: The invention comprises the following components by weight: 110 parts of acrylamide monomer, 5-35 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 parts of a crosslinking agent, 0.15 parts of an initiator, 2-6 parts by dry weight of a functional additive and water. The amount of water added is such that the water-blocking gel finally reaches 400 parts.

2. The water blocking gel according to claim 1, characterized in that The invention comprises the following components by weight: 110 parts of acrylamide monomer, 15 parts of tannic acid, 5 parts of polyvinyl alcohol, 0.2 parts of a crosslinking agent, 0.15 parts of an initiator, 2-3 parts by dry weight of a functional additive and water. The amount of water added is such that the water-blocking gel finally reaches 400 parts.

3. The water blocking gel according to claim 1, characterized in that The functional additive is one or a mixture of boron nitride, modified boron nitride, nano zirconium sol, nano silicon dioxide sol, nano titanium dioxide sol, phenylboric acid and modified phenylboric acid.

4. The water blocking gel according to claim 3, characterized in that The modified boron nitride comprises aldehyde-based cellulose nanofiber and amino-based boron nitride.

5. The water blocking gel according to claim 4, characterized in that The mass ratio of the absolute dry mass of the aldehyde-based cellulose nanofibers to the amino boron nitride is (1-5):

1.

6. The water blocking gel according to claim 4, characterized in that The modified boron nitride is prepared by the following method: aldehyde cellulose nanofibers and amino boron nitride are placed in a container and stirred until the amino boron nitride powder is wrapped 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.

7. The water blocking gel according to claim 1, characterized in that The acrylamide monomer is at least one of acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, hydroxymethyl acrylamide and dimethylaminoethyl methacrylate; The cross-linking agent is at least one of p-vinylbenzene, N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, N,N'-m-phenylene bismaleimide, and pentaerythritol triacrylate; The initiator is at least one of potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisobutyramidine, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thioxanthone, benzophenone, benzoin ether and acetophenone derivatives.

8. A method for preparing the water blocking gel according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: weighing various components, mixing them, stirring until dissolved, heating to a polymerization temperature to react and obtain a water-blocking gel.

9. Use of the water blocking gel according to any one of claims 1 to 7, characterized in that: Used for water plugging in oil fields.

Images