Water-based self-suspending composite support material, and preparation method and application thereof

Abstract

The application discloses a water-based self-suspension composite support material and a preparation method and application thereof, and belongs to the technical field of oil exploitation. The composite support material comprises aggregate and gel coated on the surface of the aggregate; the aggregate is quartz sand or ceramic granule, and the aggregate is subjected to surface treatment by amination before being coated; the gel comprises 10-20 parts of prepolymer A, 40-50 parts of acrylamide, 20-30 parts of acrylonitrile, 15-25 parts of 4-methacrylamidoglycollic acid, 1-5 parts of carbonamide, 5-15 parts of sodium hydroxide, 0.02-0.08 parts of EDTA-2Na, 1-3 parts of a crosslinking agent, 1-10 parts of a first initiator and 0.01-0.1 parts of sodium formate. The gel material on the surface of the support material can reduce adhesion even when being damp, thereby avoiding the existence of agglomerates, can be quickly and uniformly dispersed when being added into water, avoids causing plugging of formation pores or cracks and improves the continuity of fracturing construction.

Description

Technical Field

[0001] This application relates to a water-based self-suspended composite propping material, its preparation method, and its application, belonging to the field of petroleum extraction technology, specifically to the field of fracturing proppant technology in petroleum extraction. Background Technology

[0002] The core principle of traditional water-based fracturing technology is as follows: add viscosifiers, crosslinking agents, breaker agents and other additives to clean water to prepare a high-viscosity base fluid; then mix the base fluid with quartz sand to form a fracturing fluid; inject the fracturing fluid into the formation and leave it for a certain period of time, the breaker agent will undergo a breaking reaction, and the quartz sand will remain in the formation as a supporting skeleton to form artificial fractures with high conductivity, thereby reducing the seepage resistance of crude oil and increasing the production of oil wells.

[0003] However, this traditional method has significant technical drawbacks: First, the base fluid and quartz sand must be uniformly mixed before fracturing operations can be carried out, which not only makes the preparation process cumbersome but also limits the amount of fracturing fluid used. Second, the presence of a large number of additives in the base fluid restricts the proppant carrying capacity of the fracturing fluid, making it difficult to prepare a high proppant carrying capacity water-based fracturing fluid with a proppant carrying ratio of more than 60%, thus failing to meet the requirements of efficient fracturing.

[0004] To address the aforementioned technical challenges, existing research proposes a novel self-supporting water-based fracturing method: a self-supporting material is prepared by coating and modifying quartz sand or ceramsite with a gel-like substance. This material, once immersed in water, effectively inhibits particle settling, achieving a self-suspension effect for the quartz sand or ceramsite. This technology allows for immediate preparation and use of fracturing fluid, overcoming dosage limitations, simplifying the preparation process, significantly improving proppant laying efficiency and conductivity, and enhancing proppant carrying capacity and fracturing effect. For example, CN120082343A discloses a water-based suspension proppant that uses polyacrylamide gel to coat aggregate, enabling stable suspension of the proppant in water, reducing frictional resistance during proppant migration and damage to the substrate.

[0005] However, the novel self-supporting water-based fracturing method prepared by CN120082343A still has a key unresolved problem: Because it uses a gel-like substance as the coating material, this material is susceptible to moisture absorption and adhesion due to environmental humidity. The resulting agglomerated self-supporting material, when introduced into water, is difficult to disperse uniformly, leading to uneven distribution of the self-supporting material in the fracturing fluid and the formation of localized concentrated areas. This phenomenon can easily cause blockage of formation pores or fractures, severely affecting the continuity of fracturing operations and hindering the industrial application of the technology. Summary of the Invention

[0006] To address the aforementioned issues, a water-based self-suspended composite support material is provided. The gel material on the surface of this support material can reduce adhesion even when it is damp, thereby avoiding the presence of agglomerates. When added to water, it can disperse quickly and evenly, preventing blockage of formation pores or fractures and improving the continuity of fracturing operations.

[0007] According to one aspect of this application, a water-based self-suspended composite support material is provided, comprising aggregate and a gel coating the surface of the aggregate;

[0008] The aggregate is quartz sand or ceramsite, and the aggregate undergoes an amination surface treatment before coating.

[0009] The gel comprises 10-20 parts of prepolymer A, 40-50 parts of acrylamide, 20-30 parts of acrylonitrile, 15-25 parts of 4-methylacrylamidosalicylic acid, 1-5 parts of carbamide, 5-15 parts of sodium hydroxide, 0.02-0.08 parts of EDTA-2Na, 1-3 parts of crosslinking agent, 1-10 parts of first initiator, and 0.01-0.1 parts of sodium formate;

[0010] The preparation method of the prepolymer A is as follows:

[0011] S1: Phytic acid and polyethylene glycol diglycidyl ether are reacted to obtain intermediate A;

[0012] S2: Intermediate A and allyl glycidyl ether are reacted to obtain intermediate B;

[0013] S3: The intermediate B and acrylic acid are polymerized under the action of a second initiator, and then post-treated to obtain the prepolymer A.

[0014] The gel in this application incorporates acrylonitrile for copolymer modification, which offers the following advantages:

[0015] 1. It can significantly improve the salt resistance and temperature resistance of composite support materials:

[0016] Acrylonitrile molecules contain a strongly polar cyano group (-CN), which can enhance the charge repulsion effect of gel molecular chains, weaken the destructive effect of metal ions on the gel network in high-salt environments, avoid the swelling failure of traditional acrylamide gels due to salt ion erosion, and ensure the stability of the coating structure in high-salt reservoirs. In addition, the cyano group has a rigid structure, which can increase the thermal resistance of gel molecular chains and improve the overall thermal stability of the gel. This allows the modified gel to be adapted to high-temperature reservoir conditions above 70°C, solving the problem of easy degradation, flocculation and precipitation of traditional acrylamide gels at high temperatures.

[0017] 2. Effectively improves dispersibility and anti-blocking properties:

[0018] When combined with prepolymer A, it can precisely control the hydrophilic-hydrophobic balance of the gel surface, reduce the hydrogen bonding between gel molecules, and reduce the tendency to stick together in humid environments. Even if the self-supporting material comes into contact with moisture during storage or transportation, it is not easy to form agglomerates. After being put into water, it can quickly and evenly disperse, thereby avoiding the risk of blockage of formation pores and fractures from the source and ensuring the continuity of fracturing.

[0019] 3. Enhance the coating strength of the gel on the aggregate:

[0020] The copolymerization reaction of acrylonitrile and acrylamide can form a denser three-dimensional network structure. This structure has stronger adhesion to the quartz sand and is less prone to coating peeling in the high-shear environment of fracturing fluid pumping. This ensures that the self-supporting material maintains good self-sustaining performance throughout the construction process and can play a long-term supporting role in the formation.

[0021] In addition to acrylonitrile, prepolymer A is added to the gel of this application for copolymerization. The addition of prepolymer A has the following advantages:

[0022] 1. Reduce the moisture absorption of composite support materials to prevent aggregation:

[0023] Prepolymer A, with phytic acid as its matrix structure, has a relatively large volume and, after copolymerization, acts as a rigid group uniformly distributed within the gel network. During the initial stage at room temperature, the volume effect of phytic acid outweighs the effect of its hydrophilic groups. At this point, the steric hindrance effect can be utilized to form a physical barrier within the three-dimensional gel network, limiting the permeation rate of water molecules from the air into the gel, thereby reducing the gel's moisture absorption rate. Furthermore, even under the same humid conditions at room temperature, it can reduce adhesion between the composite support materials, preventing large clumps of the composite support materials from forming.

[0024] 2. Improve dispersibility in water:

[0025] On the one hand, the matrix structure of phytic acid can reduce its penetration of water molecules in the air, thereby reducing the moisture absorption and aggregation of the composite support material, and thus enabling the composite support material to disperse quickly in water. On the other hand, the structure of phytic acid contains a large number of hydrophilic groups. When the composite support material is added to water, under the action of a large number of water molecules, the effect of the hydrophilic groups of phytic acid is greater than the volume effect of phytic acid, thereby enabling the composite support material to absorb water and achieve suspension dispersion in water, and also improving its dispersibility in water.

[0026] 3. Improve the bonding strength with aggregates:

[0027] The reaction of polyethylene glycol diglycidyl ether in step S1 results in intermediate A having an epoxy group at its end, which is retained in steps S2 and S3. When this type of gel is coated with aggregate that has undergone amination surface treatment, chemical bonding can occur between the aggregate and the gel, thereby improving the bonding strength between the gel and the aggregate, and thus improving the high-temperature stability of the composite self-supporting material.

[0028] 4. Good biodegradability and environmental compatibility:

[0029] Phytic acid is a natural biomass derivative, and polyethylene glycol segments are biodegradable. The organic matter remaining in the flowback fluid after fracturing of the composite self-supporting material prepared by this prepolymer A is easily degraded by microorganisms, reducing the risk of pollution to the formation and the environment, which is in line with the development trend of environmentally friendly fracturing materials.

[0030] In the preparation of prepolymer A, in step S1, the phosphate group of phytic acid undergoes a ring-opening reaction with one epoxy group of polyethylene glycol diglycidyl ether, forming intermediate A with hydroxyl groups and terminal epoxy groups. Due to steric hindrance, only one epoxy group of polyethylene glycol diglycidyl ether can participate in the reaction with phytic acid, while the other epoxy group cannot participate. Therefore, the terminal epoxy group of intermediate A can react with the amino groups on the surface of the aggregate to form a chemical bond. This application introduces ester bonds and hydroxyl groups into intermediate A through step S1, which enhances the hydrophilicity and flexibility of the gel molecular chain, ensuring good dispersibility of the composite support material in water-based fracturing fluid and preventing agglomeration. Furthermore, the flexibility of the polyethylene glycol segments can alleviate the damage of formation stress to the gel coating layer, while the rigid structure and crosslinking sites of phytic acid can improve the compressive strength of the gel coating layer, enabling the composite self-supporting material to maintain its conductivity under closure pressure and improve oil recovery. The introduction of double bonds by allyl glycidyl ether in step S2 enables it to polymerize with acrylic acid in step S3 to form a prepolymer, thereby obtaining a polymer formed with acrylamide, acrylonitrile, etc., which forms the final gel material under the action of a crosslinking agent.

[0031] Optionally, the reaction temperature for steps S1 and S2 is 30-50℃ and the reaction time is 6-8h, and the reaction temperature for step S3 is 60-70℃ and the reaction time is 5-6h.

[0032] Optionally, the molar ratio of phytic acid and polyethylene glycol diglycidyl ether in step S1 is 1:(2-4).

[0033] The molar ratio of the two substances mentioned above affects the type and number of terminal groups in intermediate A, which in turn affects the dispersibility, temperature resistance, salt resistance, and fracturing ability of the composite support material. If the amount of polyethylene glycol diglycidyl ether is too small, the number of terminal phosphate groups in intermediate A will be large. When placed at room temperature, the moisture absorption of the gel in the composite support material will be enhanced, which will increase the probability of aggregation of the composite support material and thus reduce its dispersibility in water. Since polyethylene glycol diglycidyl ether also introduces ether bonds as hydrophilic groups, if the amount of polyethylene glycol diglycidyl ether is too large, it will not have a significant impact on the moisture absorption at room temperature, but it will reduce the salt resistance of the composite support material, making it unsuitable for the exploitation of high-salinity oil fields.

[0034] Optionally, in step S2, the molar ratio of allyl glycidyl ether to phytic acid is (1-1.2):1.

[0035] With this molar ratio setting, intermediate B contains only one double bond group. Therefore, intermediate B only reacts as a chain growth reactive group and cannot act as a crosslinking agent to crosslink the gel. This allows for control over the crosslinking points of the gel's three-dimensional network structure and improves the self-suspension performance of the composite support material.

[0036] Optionally, in step S3, the molar ratio of acrylic acid to allyl glycidyl ether is (3-4):1.

[0037] This prepolymer A is obtained by prepolymerizing intermediate B and acrylic acid. Acrylic acid has low steric hindrance, while intermediate B has high steric hindrance. By limiting the above molar ratio, the proportion of intermediate B units in prepolymer A can be controlled, thereby controlling the proportion of phytic acid structure in prepolymer A, thus achieving a balance between low moisture absorption and low adhesion under ambient temperature and dispersibility and suspension under aqueous conditions.

[0038] Optionally, the weight ratio of the prepolymer A to the acrylonitrile is 1:1.5.

[0039] This application found that, under the same room temperature conditions, different weight ratios of prepolymer A and acrylonitrile affect the water absorption of the gel, resulting in different adhesion patterns even at the same water absorption rate. The aforementioned weight ratio achieves the lowest water absorption and the weakest adhesion after water absorption.

[0040] Optionally, the first initiator is selected from thermal initiators and / or photoinitiators, and the second initiator is selected from thermal initiators and / or photoinitiators.

[0041] Preferably, both the first initiator and the second initiator are selected from at least one of ammonium persulfate and azobisisobutyronitrile.

[0042] Optionally, the aggregate undergoes an amination surface treatment before coating, specifically as follows:

[0043] The aggregate is activated, then completely immersed in a 10wt%-20wt% N-aminoethyl-3-aminopropyltriethoxysilane solution, ultrasonically treated at 50-60℃ for 2-5 hours, and then washed and dried to obtain the final product.

[0044] This application describes an amination treatment of aggregates that introduces amino groups onto the aggregate surface, enabling them to react with the epoxy groups introduced by polyethylene glycol diglycidyl ether in prepolymer A. This achieves chemical bonding between the gel and the aggregate. The N-aminoethyl-3-aminopropyltriethoxysilane contains two reactive amino groups, further increasing the binding sites with the gel and thus improving the density of the gel's encapsulation of the aggregate. The concentration of the N-aminoethyl-3-aminopropyltriethoxysilane solution affects the number of amino groups on the aggregate surface. If the concentration is too low, the bonding between the aggregate and the gel weakens; if the concentration is too high, it does not significantly improve the bonding strength but instead increases production costs.

[0045] Optionally, the drying temperature after ultrasonic treatment is 60-80℃ and the time is 4-6 hours.

[0046] Optionally, the activation process is as follows:

[0047] Carbon dioxide is continuously introduced into the water to maintain the water at a carbon dioxide saturation level. The washed aggregate is placed in the water and activated for 2-3 hours under stirring. After drying, the aggregate is obtained.

[0048] The aggregates in this application are activated and then subjected to amination treatment. This activation method can activate the groups on the surface of the aggregates, improve the amination surface treatment effect, reduce the impurity content, improve the cleanliness of the aggregate surface, and facilitate the coating of the aggregates. In addition, the hydrophilicity of the aggregate surface is enhanced after activation treatment, which can make the aggregates disperse quickly in the gel and improve the uniformity of the gel coating the aggregates.

[0049] Optionally, the drying temperature after activation treatment is 60-80℃ and the time is 4-6h.

[0050] Optionally, the quartz sand has a particle size of 40-80 mesh, and the ceramsite has a particle size of 20-40 mesh.

[0051] Optionally, the crosslinking agent is a crosslinking agent containing bisacrylamide groups.

[0052] Preferably, the crosslinking agent is N,N-methylenebisacrylamide.

[0053] According to a second aspect of this application, a method for preparing the water-based self-suspended composite support material as described in any one of the above claims is provided, comprising the following steps:

[0054] (1) The aggregate was subjected to an amination surface treatment and prepolymer A was prepared;

[0055] (2) Sodium hydroxide, carbamide, EDTA-2Na, acrylamide, acrylonitrile and the first initiator are added to water, heated and reacted for 2-4 hours, then prepolymer A, 4-methylacrylamide salicylic acid and crosslinking agent are added and reacted for at least 4 hours, and finally sodium formate is added to stop the reaction to obtain a coating gel.

[0056] (3) Immerse the aggregate completely in the coating gel, stir and coat at 90-100℃ and evaporate the water, then stop heating and ventilate to cool to room temperature to obtain the final product.

[0057] Optionally, the reaction temperature in step (2) is 60-70℃.

[0058] According to a third aspect of this application, the application of the water-based self-suspended composite support material described in any of the above claims, or the water-based self-suspended composite support material prepared by the above preparation method, in fracturing is provided.

[0059] The beneficial effects of this application include, but are not limited to:

[0060] 1. According to the water-based self-suspended composite support material of this application, the gel is prepared by acrylamide, acrylonitrile, 4-methylacrylamide salicylic acid and prepolymer A. It can reduce adhesion even after the gel material is moist and absorbs water, thereby improving the dispersion uniformity of the support material in water. It can achieve good dispersion even under high sand carrying ratio, avoid formation blockage and improve construction continuity.

[0061] 2. According to the water-based self-suspended composite support material of this application, the prepolymer A is obtained by using intermediate B with phytic acid structure as matrix and acrylic acid. This can reduce the water absorption of the composite support material at room temperature and ensure the dispersibility of the composite support material in water, thereby improving the fracturing effect.

[0062] 3. According to the water-based self-suspended composite support material of this application, the addition of prepolymer A and acrylonitrile can reduce the moisture adhesion of the gel, avoid the aggregation of the composite support material in the placement state, fundamentally avoid the risk of blockage of formation pores and fractures, and ensure the continuity of fracturing.

[0063] 4. The water-based self-suspended composite support material according to this application can maintain good dispersibility and self-suspension during high-pressure injection into the formation, avoid particle agglomeration, effectively improve fracturing efficiency, improve fracturing effect, reduce energy consumption, and improve economic benefits. Attached Figure Description

[0064] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0065] Figure 1 This is an image showing the appearance of the water-based self-suspended composite support material prepared in Example 3 of this application.

[0066] Figure 2 The image shows the water-based self-suspending composite support material prepared in Example 3 of this application self-suspending under the test method of Test Example 2.

[0067] Figure 3 The image shows the self-suspending of the water-based self-suspending composite support material prepared for Example 1 of this application under the test method of Test Example 2. Detailed Implementation

[0068] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0069] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0070] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art. This application found that intermediate A prepared from prepolymer A is soluble in water. Although allyl glycidyl ether is slightly soluble in water, it needs to be dissolved in a non-aqueous solvent before the reaction can produce intermediate B. However, the intermediate B obtained is soluble in water. The reason for this is that intermediate B has phytic acid as its matrix structure and contains a large number of hydrophilic groups, thus intermediate B is soluble in water.

[0071] In the following examples and comparative examples, the first and second initiators used are both ammonium persulfate, the crosslinking agent is N,N-methylenebisacrylamide, the particle size of the quartz sand is 40 mesh, and the particle size of the ceramsite is 20 mesh.

[0072] Example 1

[0073] This embodiment relates to a water-based self-suspended composite support material and its preparation method. The composite support material includes aggregate and gel coated on the surface of the aggregate. The aggregate is quartz sand or ceramsite. The aggregate is subjected to an amination surface treatment before coating.

[0074] Its preparation method is as follows:

[0075] (1) The aggregate was subjected to an amination surface treatment and prepolymer A was prepared;

[0076] (2) Add 5 parts of sodium hydroxide, 1 part of carbamide, 0.02 parts of EDTA-2Na, 40 parts of acrylamide, 20 parts of acrylonitrile, and 1 part of the first initiator to 40 parts of water, heat to 60°C and react for 4 hours. Then add 10 parts of prepolymer A, 15 parts of 4-methylacrylamido-salicylic acid and 1 part of crosslinking agent and react at the same temperature for another 4 hours. Finally, add 0.01 parts of sodium formate to stop the reaction and obtain a coating gel.

[0077] (3) Immerse the aggregate completely in the coating gel, stir and coat at 100°C and evaporate the water, then stop heating and ventilate to cool to room temperature to obtain the final product.

[0078] The preparation method of prepolymer A is as follows:

[0079] S1: Phytic acid and polyethylene glycol diglycidyl ether in a molar ratio of 1:2 were added to water and reacted at 30°C for 6 hours. Water was removed by rotary evaporation to obtain intermediate A.

[0080] S2: Intermediate A and allyl glycidyl ether were added to a mixed solvent of water and ethanol in a volume ratio of 1:1 and reacted at 50°C for 6 hours. The mixed solvent was removed by rotary evaporation and the mixture was washed three times with anhydrous ethanol to obtain intermediate B. The molar ratio of allyl glycidyl ether to phytic acid was 1:1.

[0081] S3: Add intermediate B and acrylic acid to water, add a second initiator accounting for 1 wt% of the reactants, polymerize at 70°C for 5-6 hours, filter and remove water by rotary evaporation to obtain prepolymer A, the molar ratio of acrylic acid and allyl glycidyl ether is 4:1.

[0082] The aggregate undergoes an amination surface treatment before coating, specifically as follows:

[0083] Carbon dioxide is continuously introduced into the water to maintain the water at a carbon dioxide saturation state. The washed aggregate is placed in the water and activated under stirring for 2 hours. It is then dried at 60°C for 6 hours to obtain activated aggregate. The activated aggregate is then completely immersed in a 20wt% N-aminoethyl-3-aminopropyltriethoxysilane solution, ultrasonically treated at 60°C for 2 hours, washed with pure water, and dried at 60°C for 4 hours to obtain the final product.

[0084] Example 2

[0085] This embodiment relates to a water-based self-suspended composite support material and its preparation method. The composite support material includes aggregate and gel coated on the surface of the aggregate. The aggregate is quartz sand or ceramsite. The aggregate is subjected to an amination surface treatment before coating.

[0086] Its preparation method is as follows:

[0087] (1) The aggregate was subjected to an amination surface treatment and prepolymer A was prepared;

[0088] (2) Add 15 parts of sodium hydroxide, 5 parts of carbamide, 0.08 parts of EDTA-2Na, 50 parts of acrylamide, 30 parts of acrylonitrile, and 10 parts of the first initiator to 65 parts of water, heat to 60-70℃ and react for 2-4 hours. Then add 20 parts of prepolymer A, 25 parts of 4-methylacrylamido-salicylic acid and 3 parts of crosslinking agent and react at the same temperature for 6 hours. Finally, add 0.1 parts of sodium formate to stop the reaction and obtain a coating gel.

[0089] (3) Immerse the aggregate completely in the coating gel, stir and coat at 90°C and evaporate the water, then stop heating and ventilate to cool to room temperature to obtain the final product.

[0090] The preparation method of prepolymer A is as follows:

[0091] S1: Phytic acid and polyethylene glycol diglycidyl ether in a molar ratio of 1:4 were added to water and reacted at 50°C for 8 hours. Water was removed by rotary evaporation to obtain intermediate A.

[0092] S2: Intermediate A and allyl glycidyl ether were added to a mixed solvent of water and ethanol in a volume ratio of 1:1 and reacted at 30°C for 8 hours. The mixed solvent was removed by rotary evaporation and the mixture was washed three times with anhydrous ethanol to obtain intermediate B. The molar ratio of allyl glycidyl ether to phytic acid was 1.2:1.

[0093] S3: Add intermediate B and acrylic acid to water, add a second initiator accounting for 1 wt% of the reactants, polymerize at 60°C for 6 hours, filter and remove water by rotary evaporation to obtain prepolymer A, with a molar ratio of acrylic acid to allyl glycidyl ether of 3:1.

[0094] The aggregate undergoes an amination surface treatment before coating, specifically as follows:

[0095] Carbon dioxide is continuously introduced into the water to maintain the carbon dioxide saturation state. The washed aggregate is placed in the water and activated under stirring for 3 hours. It is then dried at 80°C for 4 hours to obtain activated aggregate. The activated aggregate is then completely immersed in a 10wt% N-aminoethyl-3-aminopropyltriethoxysilane solution, ultrasonically treated at 50°C for 5 hours, washed with pure water, and dried at 80°C for 4 hours to obtain the final product.

[0096] Example 3

[0097] This embodiment relates to a water-based self-suspended composite support material and its preparation method. The composite support material includes aggregate and gel coated on the surface of the aggregate. The aggregate is quartz sand or ceramsite. The aggregate is subjected to an amination surface treatment before coating.

[0098] Its preparation method is as follows:

[0099] (1) The aggregate was subjected to an amination surface treatment and prepolymer A was prepared;

[0100] (2) Add 10 parts of sodium hydroxide, 4 parts of carbamide, 0.05 parts of EDTA-2Na, 45 parts of acrylamide, 21 parts of acrylonitrile, and 5 parts of the first initiator to 60 parts of water, heat to 65°C and react for 4 hours. Then add 14 parts of prepolymer A, 20 parts of 4-methylacrylamido-salicylic acid and 2 parts of crosslinking agent and react at the same temperature for 5 hours. Finally, add 0.08 parts of sodium formate to stop the reaction and obtain a coating gel.

[0101] (3) Completely immerse the aggregate in the coating gel, stir and coat at 90°C and evaporate the water, then stop heating and ventilate to cool to room temperature. See the appearance diagram below. Figure 1 That is, you get it.

[0102] The preparation method of prepolymer A is as follows:

[0103] S1: Phytic acid and polyethylene glycol diglycidyl ether in a molar ratio of 1:4 were added to water and reacted at 40°C for 8 hours. Water was removed by rotary evaporation to obtain intermediate A.

[0104] S2: Intermediate A and allyl glycidyl ether were added to a mixed solvent of water and ethanol in a volume ratio of 1:1 and reacted at 40°C for 7 h. The mixed solvent was removed by rotary evaporation and the mixture was washed three times with anhydrous ethanol to obtain intermediate B. The molar ratio of allyl glycidyl ether to phytic acid was 1.1:1.

[0105] S3: Add intermediate B and acrylic acid to water, add a second initiator accounting for 1 wt% of the reactants, polymerize at 65°C for 6 hours, filter and remove water by rotary evaporation to obtain prepolymer A, the molar ratio of acrylic acid and allyl glycidyl ether is 3:1.

[0106] The aggregate undergoes an amination surface treatment before coating, specifically as follows:

[0107] Carbon dioxide is continuously introduced into the water to maintain the carbon dioxide saturation state. The washed aggregate is placed in the water and activated under stirring for 2.5 hours. After drying at 70°C for 5 hours, the activated aggregate is obtained. The activated aggregate is then completely immersed in a 15wt% N-aminoethyl-3-aminopropyltriethoxysilane solution and ultrasonically treated at 55°C for 2-5 hours. After washing with pure water, it is dried at 70°C for 5 hours to obtain the final product.

[0108] Example 4

[0109] The difference between this embodiment and embodiment 3 is that the molar ratio of phytic acid and polyethylene glycol diglycidyl ether in step S1 is 1:1.

[0110] Example 5

[0111] The difference between this embodiment and embodiment 3 is that the molar ratio of phytic acid and polyethylene glycol diglycidyl ether in step S1 is 1:5.

[0112] Example 6

[0113] The difference between this embodiment and embodiment 3 is that the molar ratio of allyl glycidyl ether to phytic acid in step S2 is 2:1.

[0114] Example 7

[0115] The difference between this embodiment and embodiment 3 is that the molar ratio of acrylic acid and allyl glycidyl ether in step S3 is 5:1.

[0116] Example 8

[0117] The difference between this embodiment and Embodiment 3 is that the weight of prepolymer A is 16 parts.

[0118] Example 9

[0119] The difference between this embodiment and Embodiment 3 is that the aggregate was not activated; instead, it was directly and completely immersed in an N-aminoethyl-3-aminopropyltriethoxysilane solution to obtain an amination-treated aggregate.

[0120] Comparative Example 1

[0121] The difference between this comparative example and Example 3 is that step S1 is omitted, and intermediate B is obtained directly by reacting phytic acid and allyl glycidyl ether.

[0122] Comparative Example 2

[0123] The difference between this comparative example and Example 3 is that no acrylic acid is used in step S3, and only intermediate B is polymerized to obtain prepolymer A.

[0124] Comparative Example 3

[0125] The difference between this comparative example and Example 3 is that prepolymer A is not added.

[0126] Comparative Example 4

[0127] The difference between this comparative example and Example 3 is that no acrylonitrile is added.

[0128] Comparative Example 5

[0129] The difference between this comparative example and Example 3 is that the same amount of allyl glycidyl ether and acrylic acid were polymerized under the second initiator to obtain prepolymer A, that is, prepolymer A of this comparative example does not contain phytic acid structure.

[0130] Test Example 1: Room Temperature Water Absorption and Adhesion Test

[0131] The composite support materials prepared in the above embodiments and comparative examples were placed in the same temperature (20℃) and northern winter humidity (40%) environment for 10 days, and their water absorption rate was tested. The test results are shown in Table 1. Water absorption rate = [(weight after placement - weight before placement) / weight before placement] × 100%.

[0132] The composite support materials prepared in the above embodiments and comparative examples were tested for adhesion grade under the same water absorption rate of 2%. The test results are shown in Table 1. The adhesion grade is specifically graded as follows:

[0133] Non-adhesive: refers to the amount of adhesion of the composite support material being less than 1%;

[0134] Mild adhesion: refers to the amount of adhesion of the composite support material in the range of 1%-5%;

[0135] Moderate adhesion: refers to the amount of adhesion of the composite support material in the range of 6%-10%;

[0136] Severe adhesion refers to a bonding rate of more than 10% in the composite support material.

[0137] Adhesion amount = (weight of adhered composite support material / weight of all composite support material) × 100%.

[0138] Table 1

[0139]

[0140] Test Example 2: Propionate Support Effect Test

[0141] The composite proppant materials prepared in the above examples and comparative examples were tested for bulk density, pressure bearing capacity, suspension time, etc., according to the "SY / T5108-2025 Recommended Methods for Performance Indicators and Tests of Fracturing Proppants". The results are shown in Table 2 below. Figure 2 This is an image of the water-based self-suspended composite support material prepared in Example 3 after self-suspending for 8 hours. Figure 3 Images of the water-based self-suspended composite support material prepared in Example 1 after 8 hours of self-suspension. Figure 2 , Figure 3 The results show that the water-based self-suspended support material can be stably suspended in water, exhibiting good suspension and dispersion properties.

[0142] Table 2

[0143]

[0144] Test Example 3: Residual Glue After Destruction Test

[0145] The composite support materials prepared in the above examples and comparative examples were added to water at 0.3 wt%, and 1 wt‰ ammonium persulfate was added. After gelation, the gel was broken at 60°C. The viscosity and residue content after gelation were tested, and the results are shown in Table 3 below.

[0146] Table 3

[0147]

[0148] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A water-based self-suspended composite support material with good dispersibility, characterized in that, It includes aggregate and gel coating the surface of the aggregate; The aggregate is quartz sand or ceramsite, and the aggregate undergoes an amination surface treatment before coating. The gel comprises 10-20 parts of prepolymer A, 40-50 parts of acrylamide, 20-30 parts of acrylonitrile, 15-25 parts of 4-methylacrylamidosalicylic acid, 1-5 parts of carbamide, 5-15 parts of sodium hydroxide, 0.02-0.08 parts of EDTA-2Na, 1-3 parts of crosslinking agent, 1-10 parts of initiator, and 0.01-0.1 parts of sodium formate; The preparation method of the prepolymer A is as follows: S1: Phytic acid and polyethylene glycol diglycidyl ether are reacted to obtain intermediate A, with the molar ratio of phytic acid to polyethylene glycol diglycidyl ether being 1:(2-4). S2: Intermediate A and allyl glycidyl ether are reacted to obtain intermediate B, wherein the molar ratio of allyl glycidyl ether to phytic acid is (1-1.2):1; S3: The intermediate B and acrylic acid are polymerized under the action of an initiator and then post-treated to obtain the prepolymer A. The molar ratio of acrylic acid to allyl glycidyl ether is (3-4):1, and the weight ratio of prepolymer A to acrylonitrile is 1:1.

5.

2. The water-based self-suspended composite support material with good dispersibility according to claim 1, characterized in that, The aggregate undergoes an amination surface treatment prior to coating, specifically as follows: The aggregate is activated, then completely immersed in a 10wt%-20wt% N-aminoethyl-3-aminopropyltriethoxysilane solution, ultrasonically treated at 50-60℃ for 2-5 hours, and then washed and dried to obtain the final product.

3. The water-based self-suspended composite support material with good dispersibility according to claim 2, characterized in that, The activation process is as follows: Carbon dioxide is continuously introduced into the water to maintain the water at a carbon dioxide saturation level. The washed aggregate is placed in the water and activated for 2-3 hours under stirring. After drying, the aggregate is obtained.

4. The water-based self-suspended composite support material with good dispersibility according to claim 1, characterized in that, The crosslinking agent is a crosslinking agent containing bisacrylamide groups.

5. A method for preparing the water-based self-suspended composite support material with good dispersibility according to any one of claims 1-4, characterized in that, Includes the following steps: (1) The aggregate was subjected to an amination surface treatment and prepolymer A was prepared; (2) Sodium hydroxide, carbamide, EDTA-2Na, acrylamide, acrylonitrile and initiator are added to water, heated and reacted for 2-4 hours, then prepolymer A, 4-methylacrylamide salicylic acid and crosslinking agent are added and reacted for at least 4 hours, and finally sodium formate is added to stop the reaction to obtain coating gel. (3) Immerse the aggregate completely in the coating gel, stir and coat at 90-100℃ and evaporate the water, then stop heating and ventilate to cool to room temperature to obtain the final product.

6. The application of the well-dispersible water-based self-suspended composite support material according to any one of claims 1-4, or the well-dispersible water-based self-suspended composite support material prepared by the preparation method according to claim 5, in fracturing.

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