A method for the preparation of pre-crosslinked gel particles with a dual network structure, products and uses thereof

Abstract

The present application relates to the technical field of oilfield chemistry, high-temperature and high-salinity reservoir profile control and water plugging, and particularly relates to a preparation method of pre-crosslinked gel particles with a double-network structure, a product and application thereof. The present application comprises the following steps: dissolving monomers in water, then adding a crosslinking agent to obtain a mixed solution; adding an initiator to the mixed solution to react, to obtain CBCH hydrogel; completely immersing the CBCH hydrogel in a tannic acid solution to obtain CBDCH hydrogel, then drying and grinding, to obtain pre-crosslinked gel particles with a double-network structure. The preparation process of the pre-crosslinked gel particles with a double-network structure is simpler, and the pre-crosslinked gel particles have excellent temperature resistance and salt resistance. The gel swelling rate is 10.29 under the conditions of a 10% NaCl (10*10 4 mg / L) solution and a temperature of 120 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical fields of oilfield chemistry and high-temperature and high-salt oil reservoir profile control and water plugging, and in particular to a preparation method, product and application of pre-crosslinked gel particles with a double network structure. Background Art

[0002] As oil fields develop, long-term waterflooding leads to the formation of dominant high-permeability channels within the reservoir, gradually increasing the water-to-oil ratio and increasing subsequent processing and separation costs. Furthermore, waterflooding can lead to uneven fluid distribution within the reservoir, resulting in inefficient or even ineffective waterflooding and reduced oil recovery efficiency. Pre-crosslinked gel particles absorb water and swell within the reservoir, effectively blocking high-permeability areas and encouraging water flow to low-permeability zones, thereby increasing crude oil recovery.

[0003] Pre-cross-linked gel particles are a three-dimensional cross-linked polymer network system synthesized indoors. They can be injected into oil reservoirs to plug high-permeability channels, thereby improving water flooding efficiency and recovery rates. However, with the gradual deepening of exploration and development, reservoir conditions continue to deteriorate, and high-temperature and high-salt oil reservoirs continue to increase. Traditional pre-cross-linked gel particles lack heat and salt resistance, which affects the plugging efficiency and makes it difficult to achieve the expected profile control and water plugging effects. Summary of the Invention

[0004] Based on the above content, the present invention provides a preparation method, product and application of pre-crosslinked gel particles with a double network structure to overcome the problems of insufficient mechanical properties and inability to withstand high temperature and high salt environments in existing pre-crosslinked gel particles.

[0005] To achieve the above object, the present invention provides the following solutions: One of the technical solutions of the present invention is a method for preparing pre-crosslinked gel particles having a double network structure, comprising the following steps:

[0006] The monomer is dissolved in water, and then a cross-linking agent is added to obtain a mixed solution;

[0007] adding an initiator to the mixed solution to react and obtain a CBCH hydrogel;

[0008] The CBCH hydrogel is completely immersed in a tannic acid solution to obtain a CBDCH hydrogel, and then dried and ground to obtain the pre-crosslinked gel particles having a double network structure;

[0009] The monomers are acrylamide, N,N-dimethylacrylamide, acrylic acid and sodium p-styrene sulfonate.

[0010] The second technical solution of the present invention is a pre-crosslinked gel particle with a double network structure prepared according to the preparation method.

[0011] The third technical solution of the present invention is the application of the pre-crosslinked gel particles with a double network structure in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

[0012] A fourth technical solution of the present invention is a profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, the raw materials of which include the pre-crosslinked gel particles with a double network structure.

[0013] The present invention discloses the following technical effects:

[0014] The pre-crosslinked gel particles of the present invention have a unique double network structure and excellent mechanical properties.

[0015] The preparation process of the pre-crosslinked gel particles with a double network structure is simpler, and the particles have excellent temperature and salt resistance. 4 The gel swelling ratio was 10.29 under the conditions of (a) 200 mg / L) solution and temperature of 120℃.

[0016] After the pre-crosslinked gel particles with a double network structure of the present invention are injected into the formation as a profile control and water plugging agent, the pre-crosslinked gel particles can block water in the hyperpermeable area, improve the heterogeneity of the formation, increase the water flooding swept area, and thus achieve the effect of improving the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the process flow for preparing pre-crosslinked gel particles with a double network structure in Example 2.

[0019] Figure 2 SEM images of CBCH hydrogel (a-1, a-2, a-3, a-4) and CBDCH hydrogel (b-1, b-2, b-3, b-4) in Example 2 and the corresponding EDX Mapping images.

[0020] Figure 3 FT-IR images of CBCH and CBDCH hydrogels prepared in Example 2.

[0021] Figure 4 Rheological properties of CBCH hydrogel and CBDCH hydrogel in Example 2; wherein, (a) the strain scanning range is 0.01% to 1000%; and (b) the frequency scanning range is 0.1 Hz to 10 Hz.

[0022] Figure 5 The uniaxial compression properties of the CBCH hydrogel and CBDCH hydrogel in Example 2; wherein, (a) the compressive stress-strain curve; (b) the corresponding toughness and compression modulus of the CBCH hydrogel and CBDCH hydrogel.

[0023] Figure 6 This is the plugging performance of the CBDCH gel particles in Example 2. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] A first aspect of the present invention provides a method for preparing pre-crosslinked gel particles having a double network structure, comprising the following steps:

[0030] The monomer is dissolved in water, and then a cross-linking agent is added to obtain a mixed solution;

[0031] The initiator is added to the mixed solution to react, to obtain CBCH hydrogel;

[0032] The CBCH hydrogel is completely immersed in a tannic acid solution to obtain CBDCH hydrogel, which is then dried and ground to obtain the pre-crosslinked gel particles with a double network structure.

[0033] The monomers are acrylamide, N,N-dimethyl acrylamide, acrylic acid and sodium p-styrene sulfonate.

[0034] In a preferred embodiment of the present application, the mass ratio of acrylamide, N,N-dimethyl acrylamide, acrylic acid and sodium p-styrene sulfonate is 4:4:3:1; and the addition amount of the monomers is 20wt%-30wt% of the water. Among them, acrylamide and N,N-dimethyl acrylamide serve as the main crosslinking monomers, which help to adjust the mechanical strength, stability and hydrophilicity of the gel, respectively. Acrylic acid as a hydrophilic monomer can significantly improve the swelling performance of the gel through the dissociation effect of its carboxyl group. Sodium p-styrene sulfonate significantly enhances the thermal stability and temperature and salt resistance of the gel in complex reservoir environments through its rigid benzene ring group and salt resistance. Its sulfonic acid group dissociates in aqueous solution to produce negative charges, giving the gel good ion exchange capacity and strong charge density, thereby improving its performance under extreme conditions, especially under high temperature and high salt conditions. In the design of monomer ratio, too high a proportion of crosslinking monomers may lead to too high a crosslinking density of the gel, thereby affecting the swelling performance and mechanical strength of the gel, and may also increase the brittleness of the gel, reducing its toughness; while too low a proportion of monomers may lead to loose structure of the gel, reducing its mechanical strength and stability, and may even affect the formation of the double network structure, failing to effectively achieve the desired multifunctionality. Therefore, reasonable optimization design of monomer types and proportions is a key factor to ensure the stability of the double network structure and excellent comprehensive performance of the gel particles.

[0035] In summary, the types and proportions of monomers not only affect the structural characteristics and physical properties of the gel, but also determine the performance of the gel in a specific environment. The reasonable design of monomer ratio and monomer content proposed in the present application can effectively balance the swelling, mechanical properties and environmental resistance of the gel. By precisely controlling the proportion of each monomer, the crosslinking density of the gel can be optimized, thereby realizing the ideal double network structure and ensuring excellent comprehensive performance of the gel under different environmental conditions.

[0036] In a preferred embodiment of the present invention, the crosslinking agent is methacrylated chitosan; the initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutylimidazoline hydrochloride; the added amount of the crosslinking agent is 1 wt% of the mixed solution; the added amount of the initiator is 1 wt% of the mixed solution.

[0037] In the present invention, the green crosslinking agent methacrylated chitosan (ChMA) is used to replace the traditional crosslinking agent MBA. First, ChMA reacts with the monomer to form a hydrogel network with a chemically crosslinked structure, and then is immersed in a tannic acid (TA) solution. By forming a large number of hydrogen bonds with the hydrogel molecular chains, the hydrogel is further endowed with a reversible physical crosslinked dynamic network. This double-network structure hydrogel has excellent mechanical properties. The dynamic physical crosslinked network can be effectively de-crosslinked under the action of external force to dissipate energy, and can be quickly restored by restoring the reversible crosslinked bonds after the pressure disappears. At the same time, the chemical crosslinked network ensures the structural integrity of the hydrogel. This pre-crosslinked gel particle plugging agent with a double network structure has good stability and excellent strength under high temperature and high salinity conditions. It can be better applied to high temperature and high salinity oil reservoir profile control and water plugging.

[0038] In a preferred embodiment of the present invention, the step of introducing nitrogen into the mixed solution to remove oxygen in the mixed solution is further included before adding the initiator into the mixed solution; the reaction temperature is 45-65° C., and the reaction time is 4-6 hours.

[0039] In a preferred embodiment of the present invention, the solvent of the tannic acid solution is water; the concentration of the tannic acid solution is 0.05-0.2 mmol / L; and the immersion time is 8-12 hours.

[0040] The second aspect of the present invention provides pre-crosslinked gel particles having a double network structure prepared according to the preparation method.

[0041] The third aspect of the present invention provides the use of the pre-crosslinked gel particles with a double network structure in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

[0042] A fourth aspect of the present invention provides a profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, the raw materials of which include the pre-crosslinked gel particles having a double network structure.

[0043] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0044] The methacrylated chitosan (ChMA) used in the examples of the present invention was homemade in the laboratory. The preparation steps of methacrylated chitosan are as follows:

[0045] First, 3% (w / v) chitosan powder was dissolved in 3% (v / v) acetic acid solution at room temperature (RT) overnight. Methacrylic anhydride was added to the mixed solution in a mass ratio of 4:1 to chitosan, and the mixture was reacted at room temperature for 4 hours under the action of a magnetic stirrer. After the reaction was completed, the reaction mixture was further purified with deionized water using a cellulose dialysis membrane (molecular weight cut-off of 14 kDa), and the resulting mixture was freeze-dried in a vacuum freeze dryer to obtain ChMA, which was then stored in a refrigerator for later use. ChMA obtained by other means, such as purchase, is also applicable to the present invention.

[0046] The test methods involved in the present invention are as follows: the swelling rate test refers to the GB / T 1033.1-2008 standard, the rheological property test refers to the ISO 11443:2006 standard, and the uniaxial compression property test refers to the GB / T 1041-2008 standard.

[0047] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] A method for preparing pre-crosslinked gel particles with a double network structure, comprising the following steps:

[0050] (1) 4 g of acrylamide, 4 g of N,N-dimethylacrylamide, 3 g of acrylic acid, and 1 g of sodium p-styrenesulfonate were dissolved in 48 mL of deionized water and stirred with a magnetic stirrer until completely dissolved. 0.12 g of methacrylated chitosan (a green crosslinker) was then added to the solution, and nitrogen was injected for 15 min to remove oxygen from the solution to obtain a mixed solution.

[0051] (2) 0.12 g of potassium persulfate was added to the mixed solution, stirred to completely dissolve it, and then the mixture was poured into a glass bottle and transferred to a 45°C forced air drying oven for reaction for 4 h to obtain a ChMA-crosslinked hydrogel (CBCH hydrogel).

[0052] (3) The prepared CBCH was cut into uniform disc-shaped samples and then soaked in a 0.05 mmol / L tannic acid solution overnight (8-12 hours, the CBCH gel must be completely immersed in the tannic acid solution) to prepare a ChMA-based double-crosslinked hydrogel (CBDCH hydrogel). After drying at 60°C for 12 hours, the sample was crushed and ground through a 100-mesh sieve to obtain pre-crosslinked gel particles with a double network structure.

[0053] The CBDCH hydrogel prepared in this example was heated to 10% NaCl (10×10 4The swelling kinetics of CBDCH hydrogel at 80°C and different salinity solutions (10% NaCl, 20% NaCl, 25% NaCl, 10% MgCl2+10% CaCl2, 22×10 4 mg / L of formation water; the formation contains various inorganic salts, so the mineralization of the formation water is very high, 22×10 4 mg / L in formation water 4 mg / L represents the concentration of various inorganic salt ions in formation water), and their swelling ratios are 3.34, 2.28, 1.13, 1.04 and 0.91 respectively.

[0054] Example 2

[0055] A method for preparing pre-crosslinked gel particles with a double network structure, comprising the following steps:

[0056] (1) Same as step (1) in Example 1.

[0057] (2) 0.12 g of potassium persulfate was added to the mixed solution, stirred to completely dissolve it, and then the mixture was poured into a glass bottle and transferred to a blast drying oven at 55°C for 4 h to obtain a ChMA-crosslinked hydrogel (CBCH hydrogel).

[0058] (3) The prepared CBCH gel sample was cut into uniform disc-shaped samples and then immersed in a 0.05 mmol / L tannic acid solution overnight to prepare a ChMA-based double-crosslinked hydrogel (CBDCH hydrogel). The sample was dried at 60°C for 12 h and then crushed and ground through a 100-mesh sieve to obtain pre-crosslinked gel particles with a double network structure.

[0059] The process flow diagram of preparing pre-crosslinked gel particles with a double network structure in this embodiment is as follows: Figure 1 shown.

[0060] Figure 2 is the SEM image of CBCH hydrogel and CBDCH hydrogel; Figure 2 It can be seen that the CBCH gel presents an ordered porous structure, which is derived from the uniform three-dimensional network formed by the crosslinker ChMA and the monomer under the action of the initiator. Figure 2 a-4) shows that C, N, O, and S elements are evenly distributed in the gel, verifying the uniformity of the cross-linked network. Figure 2Figure b shows that TA modification results in a tighter gel network with smaller, denser pores in CBDCH. Compared to CBCH, the C, N, and O content in CBDCH increases significantly and becomes more evenly distributed. These results indicate that TA enhances interpolymer chain entanglement through hydrogen bonding, promoting the formation of a robust dual-crosslinked network.

[0061] Figure 3 FT-IR images of CBCH hydrogel and CBDCH hydrogel; Figure 3 It can be seen that in the FTIR spectrum of CBCH, 1664 cm -1 is C=O stretching vibration, 1254cm -1 and 1450cm -1 CO bending vibration and -OH stretching vibration, 1120 cm -1 The FTIR spectrum of CBDCH overlaps with that of TA, indicating that TA is successfully integrated into the CBCH network. In particular, the phenolic hydroxyl group (3350 cm -1 ) forms hydrogen bonds with functional groups such as amide and carboxyl groups in CBCH, causing the relevant vibration peaks to shift to lower wavenumbers.

[0062] Figure 4 is the rheological properties of CBCH hydrogel and CBDCH hydrogel (Linear viscoelastic region in the figure represents the linear viscoelastic region); Figure 4 It can be seen that when the strain is less than 10%, the modulus of CBCH and CBDCH samples remains stable, and the elastic modulus (G′) is always higher than the viscous modulus (G″), showing solid-like behavior and forming a cross-linked three-dimensional network. Figure 4 As shown in (b), the elastic modulus of CBDCH (G′≈12000Pa) is significantly higher than that of CBCH (G′≈7000Pa), an increase of 71.4%, indicating that CBDCH has higher deformation capacity and shear strength.

[0063] Figure 5 is the uniaxial compression performance of CBCH hydrogel and CBDCH hydrogel (Compression Modulus represents compression modulus, and Toughness represents toughness); Figure 5 As can be seen, the compressive strength of the CBCH hydrogel at 90% strain is 0.075 MPa, while that of CBDCH is 0.124 MPa, 1.65 times that of CBCH. The enhanced mechanical properties of CBDCH are attributed to the non-covalent cross-linked network formed between TA and the hydrophilic monomer, which creates a double cross-linked structure and increases the cross-linking density and compressive resistance of the gel. Figure 5(b) shows that the compression modulus and toughness of CBDCH hydrogel are 6.87 KPa and 1.63 MJ·m -3 , which are 1.55 times and 1.46 times that of CBCH, respectively. The results show that the double-crosslinked structure of CBDCH improves mechanical strength and water absorption capacity, helps to effectively disperse external forces, avoid rupture, and thus improve plugging efficiency.

[0064] The CBDCH hydrogel prepared in this example was heated to 10% NaCl (10×10 4 The swelling kinetics of CBDCH hydrogel at 80°C and different salinity solutions (10% NaCl, 20% NaCl, 25% NaCl, 10% MgCl2 + 10% CaCl2 and 22×10 4 mg / L formation water), and their swelling ratios were 5.75, 3.53, 1.60, 1.41 and 1.26, respectively.

[0065] Example 3

[0066] The only difference from Example 2 is that the reaction temperature in step (2) is 65° C.; the remaining steps and parameters are the same as those in Example 2.

[0067] The CBDCH hydrogel prepared in this example was heated to 10% NaCl (10×10 4 The swelling dynamics of CBDCH hydrogel at 80℃ and different salinity solutions (10% NaCl, 20% NaCl, 25% NaCl, 10% MgCl2+10% CaCl2, 22×10 4 mg / L formation water), and their swelling ratios were 3.86, 1.69, 1.36, 1.11 and 0.97, respectively.

[0068] Example 4

[0069] The only difference from Example 2 is that the concentration of the tannic acid solution in step (3) is 0.1 mmol / L; the remaining steps and parameters are the same as those in Example 2.

[0070] The CBDCH hydrogel prepared in this example was heated to 10% NaCl (10×10 4The swelling dynamics of CBDCH hydrogel at 80℃ and different salinity solutions (10% NaCl, 20% NaCl, 25% NaCl, 10% MgCl2+10% CaCl2, 22×10 4 mg / L formation water), and their swelling ratios were 2.65, 0.66, 0.73, 1.18 and 1.69, respectively.

[0071] Example 5

[0072] The only difference from Example 2 is that potassium persulfate in step (2) is replaced by azobisisobutylimidazoline hydrochloride, and the concentration of the tannic acid solution in step (3) is 0.1 mmol / L; the remaining steps and parameters are the same as those in Example 2.

[0073] The CBDCH hydrogel prepared in this example was heated to 10% NaCl (10×10 4 The swelling kinetics of CBDCH hydrogel at 80°C and different salinity solutions (10% NaCl, 20% NaCl, 25% NaCl, 10% MgCl2+10% CaCl2, 22×10 4 mg / L formation water), and their swelling ratios were 2.19, 0.45, 0.59, 0.97 and 1.68, respectively.

[0074] Plugging performance test:

[0075] The experiment used a natural rock core with a diameter of 2.49 cm and a length of 4.98 cm for fracture design, and a rough fracture surface was created using the Brazilian splitting test. To create a 0.5 mm crack in the core and prevent closure, stainless steel plates were clamped on both sides of the core, and a hole was drilled at the entrance to improve injection capacity. The experimental steps are as follows:

[0076] (1) Place the crushed core in a holder and load the surrounding pressure to maintain 3 MPa higher than the injection pressure. Inject 2% NaCl solution at a rate of 0.5 mL / min until the injection pressure and flow rate are stable. Calculate the permeability before plugging (K) using Darcy's law. b ).

[0077] (2) Inject 2% gel particle solution (carried by guar gum) at the same injection rate until the injection pressure stabilizes and particles are observed to flow out of the outlet. The core temperature is raised to 80°C and aged for 24 hours.

[0078] (3) Re-inject 2% NaCl solution at a rate of 0.5 mL / min until the pressure and flow rate are stable, and calculate the permeability after plugging (K a ) again. The plugging effect of the hydrogel particles is evaluated by the breakthrough pressure gradient and the plugging efficiency (E).

[0079] E = (K b - K a ) / K b x 100 (1)

[0080] The plugging performance of the CBDCH gel particles in Example 2 was tested, and the results are shown in Table 2. Figure 6 To evaluate the plugging effect of the reservoir fractures, a 0.5 mm steel plate was added to the natural core to simulate the fracture, and the fracture was filled with 100 mesh CBDCH gel particles. Figure 6 It is shown that the fracture leads to high permeability and stable pressure change when the 2 wt% NaCl solution is injected for the first time. After the injection of the CBDCH gel particles, the injection pressure rises rapidly to a maximum value (180 psi / ft), and then decreases and stabilizes at 157 psi / ft as the particles flow out. The core temperature is raised to 80°C, and the gel particles further swell. After the second injection of the NaCl solution, the breakthrough pressure gradient is 261 psi / ft, and the stable pressure gradient is 206 psi / ft. The plugging efficiency after the injection of the CBDCH is 95.4%, and the plugging rate increases to 96.7% after the second injection of the NaCl solution. The results show that the CBDCH gel particles can effectively plug the high permeability layer and swell at high temperature to form a stable plugging.

[0081] The above-described examples are only to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preparing pre-crosslinked gel particles having a double network structure, characterized in that: The following steps are involved: The monomer is dissolved in water, and then a cross-linking agent is added to obtain a mixed solution; adding an initiator to the mixed solution to react and obtain a CBCH hydrogel; The CBCH hydrogel is completely immersed in a tannic acid solution to obtain a CBDCH hydrogel, and then dried and ground to obtain the pre-crosslinked gel particles having a double network structure; The monomers are acrylamide, N, N-dimethylacrylamide, acrylic acid and sodium p-styrene sulfonate; The amount of the monomer added is 20wt%-30wt% of the water; The cross-linking agent is methacrylated chitosan; The added amount of the cross-linking agent is 1 wt % of the mixed solution.

2. The preparation method according to claim 1, characterized in that The mass ratios of acrylamide, N, N-dimethylacrylamide, acrylic acid and sodium p-styrenesulfonate are 4:4:3:1 respectively.

3. The preparation method according to claim 1, characterized in that The initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutylimidazoline hydrochloride; and the added amount of the initiator is 1 wt % of the mixed solution.

4. The preparation method according to claim 1, characterized in that Before adding the initiator to the mixed solution, the method further comprises introducing nitrogen into the mixed solution to remove oxygen in the mixed solution; the reaction temperature is 45-65° C., and the reaction time is 4-6 h.

5. The preparation method according to claim 1, characterized in that The solvent of the tannic acid solution is water; the concentration of the tannic acid solution is 0.05-0.2 mmol / L; and the immersion time is 8-12 h.

6. Pre-crosslinked gel particles having a double network structure prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the pre-crosslinked gel particles with a double network structure as claimed in claim 6 in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

8. A profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, characterized in that: The raw materials include the pre-crosslinked gel particles with a double network structure as claimed in claim 6.

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