A self-suspending proppant based on nanocellulose composite coating and a method of making

Abstract

The present application relates to the technical field of oilfield fracturing mining, in particular to a kind of self-suspension proppant based on nanocellulose composite coating and preparation method.The proppant is composed of 0.1%-0.3% reticular viscoelastic reinforcing agent, 0.4%-2% associated polymer, and 0.5%-2% nanocellulose composite coating adhered to 96%-98.5% core proppant.The composite coating can firmly adhere the two to the surface of the proppant, and after water is encountered, the reticular viscoelastic reinforcing agent and the associated polymer dissolve rapidly and produce a synergistic effect, while the nanocellulose enhances the elasticity of the associated network structure after dissolving in water, enabling the proppant to self-suspend in high-temperature high-salinity water for a long time, simplifying the fracturing construction process.Compared with traditional proppants, the suspension time is increased by 10-20 times, and the polymer usage is reduced by 3-5 times.The coating can be used for existing film-coated proppants, giving them self-suspension capability, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of oilfield fracturing technology, and more specifically, to a self-suspending proppant based on a nanocellulose composite coating and its preparation method. Background Technology

[0002] With the continuous development of oil and gas exploration and development technologies, unconventional oil and gas is playing an increasingly important role in global oil and gas production. Hydraulic fracturing, as a major production enhancement method in unconventional oil and gas extraction, relies on proppant to support hydraulic fractures, forming sand-filled fractures with high conductivity in the reservoir. Currently, traditional proppants tend to settle rapidly in water, requiring high-viscosity fracturing fluid systems and high pumping rates to achieve long-term suspension. On the one hand, this fracturing fluid system relies on plant gums or synthetic polymers for thickening; after the gum breaks down, a large amount of insoluble matter remains, clogging fracture pores and causing a decrease in fracture conductivity of over 30%. On the other hand, the fluid preparation process is complex and prone to failure in high-temperature and high-salt environments, resulting in insufficient sand suspension stability.

[0003] Invention patents CN119307250A and CN107033871B disclose "a self-suspending proppant for low-water fracturing", CN119684995A and CN106147746B respectively, CN107033871B respectively. All of these patents use silane coupling agents to treat the surface of the proppant. However, silane coupling agents are insoluble in water, which may lead to a decrease in the conductivity of the fracture.

[0004] Invention patent CN104946233B discloses "a self-suspending proppant for natural water fracturing", invention patent CN116814237B discloses "a multifunctional composite proppant and its preparation method", and invention patent CN104944840A discloses "a preparation method of a self-suspending proppant for natural water fracturing". These invention patents all use conventional resin materials as binders, but conventional resin materials are insoluble in water, which may cause blockage of the fracture throat.

[0005] Patent CN108165251B discloses a "self-suspending proppant with salt water resistance for hydraulic fracturing," which uses a binder to attach a masking agent and a water-soluble polymer to the surface of the proppant, relying on the chelating effect of the masking agent to improve its salt resistance. However, this proppant requires a high amount of masking agent and cannot effectively improve the salt resistance of the proppant. Patent CN120248211A discloses a "seawater-based polymer-coated self-suspending proppant and its preparation method and application," which includes: soaking the proppant in a silane coupling agent and drying it to obtain a pretreated proppant; dissolving acrylamide, a hydrophobic monomer, a betaine monomer, and sodium styrene sulfonate in a solvent, adding the pretreated proppant, and performing a copolymerization reaction to obtain a self-suspending proppant. This proppant exhibits excellent temperature and salt resistance, but the copolymerization reaction is uncontrollable. The surfactant and proppant need to be compounded on-site according to strict ratios to achieve synergistic effects. Patent CN119529817A discloses "a self-suspending proppant and its preparation method and application," which requires on-site compounding and a high amount of thickener to achieve high viscosity in the suspended proppant solution. Patent CN108424762B discloses "a self-suspending proppant for hydraulic fracturing and its preparation method," which requires a high concentration of thickener to achieve self-sustaining capability, making it uneconomical for large-scale hydraulic fracturing.

[0006] In conclusion, based on existing technologies, obtaining a self-suspension proppant that can achieve self-suspension capability, has a simple preparation process, and exhibits temperature and salt resistance and low reservoir damage, along with its preparation method, still has significant practical implications. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a self-suspension proppant based on a nanocellulose composite coating and its preparation method. This self-suspension proppant exhibits good suspension capacity and biodegradability, and maintains good suspension capacity even in water with high temperature and mineralization.

[0008] The technical solution of this invention is as follows:

[0009] In a first aspect, the present invention provides a self-suspension proppant based on a nanocellulose composite coating, wherein the self-suspension proppant is composed of 0.1%-0.3% of a network viscoelastic reinforcing agent and 0.4%-2% of an associative polymer adhered to a core proppant by a 0.5%-2% nanocellulose composite coating.

[0010] The network viscoelasticity reinforcing agent is at least one of sodium lignosulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium α-alkenylsulfonate;

[0011] The nanocellulose composite coating is composed of a mixed aqueous solution of polyvinyl alcohol and TEMPO oxidized nanocellulose;

[0012] The core support agent is at least one of the following: quartz sand, ceramsite, crushed nutshell particles, hollow glass microspheres, metal particles, and pre-coated support agent.

[0013] The structural formula of the associative polymer is shown below:

[0014]

[0015] In the formula, by mass percentage, a is 57%-62%; b is 17%-36%; m is 3%-12%; n is 2%-7%; o is 0.5%-3%; p is 0.5%-2%; R1 is hydrophobic functional monomer 1; R2 is hydrophobic functional monomer 2.

[0016] Furthermore, the preparation of the nanocellulose composite coating includes:

[0017] Polyvinyl alcohol powder was added to deionized water and stirred to obtain a polyvinyl alcohol aqueous solution. TEMPO oxidized nanocellulose was added to the polyvinyl alcohol aqueous solution and mixed evenly to obtain a nanocellulose composite coating.

[0018] Furthermore, the mass ratio of polyvinyl alcohol powder to TEMPO oxidized nanocellulose is 10:(2-5).

[0019] Furthermore, the degree of alcoholysis of polyvinyl alcohol is 86.5 mol%-89 mol%; the solid content of TEMPO oxidized nanocellulose is 1%-4%.

[0020] Furthermore, the stirring rate of the polyvinyl alcohol powder added to deionized water is 600-800 r / min; the concentration of the polyvinyl alcohol aqueous solution is 5wt%-15wt%.

[0021] Furthermore, the pre-coated support agent is at least one of epoxy resin coating support agent, phenolic resin coating support agent, polyurethane resin coating support agent, and modified resin coating support agent.

[0022] Furthermore, the long-chain structure of hydrophobic monomer 1 is a C8-C 16 It has a straight-chain alkyl structure.

[0023] Secondly, based on the same inventive concept, the present invention provides a method for preparing a self-suspending proppant as described in any of the first aspects, the method comprising the following steps:

[0024] The nanocellulose composite coating is sprayed onto the core support and stirred evenly for 1-2 minutes. Then, the network viscoelasticity enhancer and the associative polymer are added and stirred evenly to obtain the self-suspending support.

[0025] Furthermore, the particle size of the network viscoelasticity enhancer and the associative polymer is 120 / 140 mesh.

[0026] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0027] 1. The self-suspending proppant of this invention, through the dissolution of its surface network viscoelastic enhancer and associative polymer in water, directly imparts excellent viscoelasticity to the proppant-carrying fluid, enabling the core proppant to maintain a long-term fully suspended state and ensuring its migration to the distal end of the fracture. This characteristic eliminates the need for conventional methods that rely on adding thickeners to adjust the proppant-carrying fluid properties, thus simplifying fracturing operations and reducing operating costs.

[0028] 2. This invention obtains a nanocellulose composite coating by uniformly dispersing polyvinyl alcohol (PVA) and TEMPO oxidized nanocellulose in an aqueous solution. Since PVA itself has insufficient bonding strength, the introduction of TEMPO oxidized nanocellulose allows it to form an interpenetrating hydrogen bond network with PVA, improving the mechanical bonding strength and temperature resistance of the composite coating. Simultaneously, the nanofibers in the composite coating may enter the coating layer of the film support during the curing process, further enhancing the adhesion to the film support and the compatibility with bonding materials. The bonding with the network viscoelastic reinforcing agent and associative polymer is mainly through physical adhesion and hydrogen bonding. Furthermore, PVA and TEMPO oxidized nanocellulose are characterized by rapid dissolution in water and good biodegradability, which helps the coating release the network viscoelastic reinforcing agent and associative polymer in a timely manner in an aqueous environment, with minimal damage to the reservoir.

[0029] 3. This invention prepares a self-suspending proppant by introducing a physical composite structure of nanocellulose composite coating, network viscoelastic enhancer, and associative polymer layer. The physical composite structure in this self-suspending proppant can be coated onto the surface of quartz sand, ceramsite, and resin-coated proppants, enabling them to possess good self-suspending capabilities without affecting their inherent functions.

[0030] 4. Through systematic screening, this invention has discovered a synergistic effect between the above-mentioned network viscoelastic reinforcing agent and the associative polymer. The network viscoelastic reinforcing agent promotes the association between molecules of the associative polymer by forming mixed micelles with hydrophobic monomers, resulting in the generation of more hydrophobic microdomains, making the network structure more compact, and improving the suspension ability of the proppant in the sand-carrying liquid.

[0031] 5. In this invention, both the network viscoelastic reinforcing agent and the associative polymer adhere to the proppant. Without the need for compounding the network viscoelastic reinforcing agent and strict on-site ratio control, the synergistic effect between the network viscoelastic reinforcing agent and the associative polymer can be achieved. After dissolving in water, it further increases its viscoelasticity, giving the proppant excellent suspension properties.

[0032] 6. In this invention, TEMPO oxidized nanocellulose has high hydrophilicity and nanoscale fiber structure. When the composite coating comes into contact with water, the nanocellulose will disperse into the aqueous phase as a nano-reinforcing filler, interspersed in the associative network of the associative polymer. The carboxyl groups on its surface will form hydrogen bonds with the hydrophilic groups of the associative polymer, thereby improving the elasticity of the associative network structure and thus improving the self-suspension ability of the proppant.

[0033] 7. In this invention, the amount of nanocellulose composite coating used is only 0.5%-2% of the mass of the proppant. The prepared proppant has low water content and does not require drying treatment, thus saving costs and simplifying the processing technology, making it suitable for large-scale production. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of the self-suspending proppant provided in an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of the preparation process of the self-suspending proppant provided in the embodiments of the present invention;

[0038] Figure 3 This is a scanning electron microscope image of the core support in Embodiment 1 of the present invention;

[0039] Figure 4 This is a scanning electron microscope image of the self-suspending proppant in Embodiment 1 of the present invention;

[0040] Figure 5 This is a schematic diagram of the proppant suspension state when placed in clear water according to Embodiment 1 of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0044] In the following examples and comparative examples, the associative polymers used in the examples use the structures of hydrophobic functional monomer 1 and hydrophobic functional monomer 2 disclosed in Chinese invention patent publication number CN120309799B.

[0045] It should be noted that the structures of hydrophobic functional monomer 1 and hydrophobic functional monomer 2 are existing technologies, and the structures disclosed in the referenced documents can be fully applied to the technical solutions of this invention to achieve the technical effects required by this invention. They will not be affected by the slight differences in the structure of the associative polymer. Therefore, the specific structures of hydrophobic functional monomer 1 and hydrophobic functional monomer 2 will not be described in this article.

[0046] Please refer to Figure 1 and Figure 2 Based on the basic theoretical concept of this invention, the following embodiments and comparative examples are provided.

[0047] Example 1

[0048] This embodiment 1 provides a method for preparing a self-suspending support based on a nanocellulose composite coating, comprising the following steps:

[0049] S1. By mass, 10 parts of polyvinyl alcohol powder are added to 100 parts of deionized water and stirred evenly to obtain a polyvinyl alcohol aqueous solution; under high-speed stirring at 600 r / min, 3.5 parts of TEMPO oxidized nanocellulose are slowly added to the polyvinyl alcohol aqueous solution and stirred for 5 min to make it evenly dispersed in the polyvinyl alcohol aqueous solution to obtain a nanocellulose composite coating solution.

[0050] S2. Spray 1 part of the nanocellulose composite coating solution prepared in S1 onto 100 parts of 40 / 70 mesh quartz sand and stir evenly. After stirring for 2 minutes, add 0.18 parts of sodium α-olefin sulfonate and 0.8 parts of associative polymer powder, and continue stirring evenly to obtain a self-suspending support based on nanocellulose composite coating.

[0051] In the associative polymer, R1 is hydrophobic functional monomer 1, which is 2-acrylamidotriethoxydimethyldodecylammonium chloride, and its structural formula is:

[0052] ;

[0053] R2 is hydrophobic functional monomer 2, which is sodium 2-acrylamidododecyl sulfonate with the following structural formula:

[0054] .

[0055] The scanning electron microscope image of the core support used in this embodiment is shown below. Figure 3 As shown; a scanning electron microscope image of the prepared self-suspending proppant is shown below. Figure 4 As shown; by Figure 3 and Figure 4 The comparison can be observed Figure 4 The presence of associative polymers adhering to the proppant indicates successful preparation of the self-suspending proppant.

[0056] Example 2

[0057] Example 2 provides a method for preparing a self-suspending support based on a nanocellulose composite coating. The only difference from Example 1 is that the amount of associative polymer powder added is 0.6 parts, and the hydrophobic functional monomer 1 is ethyl acrylate dimethyl dodecyl ammonium chloride, with the following structural formula:

[0058]

[0059] Hydrophobic functional monomer 2 is sodium 2-acrylamidododecyl disulfonate, and its structural formula is:

[0060]

[0061] Example 3

[0062] Example 3 provides a method for preparing a self-suspending support based on a nanocellulose composite coating. The only difference from Example 1 is that the amount of associative polymer powder added is 1 part, and the hydrophobic functional monomer 1 is ethyl acrylate dimethyl hexadecyl ammonium chloride, with the following structural formula:

[0063]

[0064] Example 4

[0065] Example 4 provides a method for preparing a self-suspending proppant based on a nanocellulose composite coating. The only difference from Example 1 is that the quartz sand in the core proppant is replaced with a 40 / 70 mesh epoxy resin coated proppant.

[0066] Example 5

[0067] Example 5 provides a method for preparing a self-suspending proppant based on a nanocellulose composite coating. The only difference from Example 1 is that the quartz sand in the core proppant is replaced with 40 / 70 mesh hollow glass microspheres, and the amount of sodium α-olefin sulfonate added is 0.15 parts.

[0068] Example 6

[0069] Example 6 provides a method for preparing a self-suspending proppant based on a nanocellulose composite coating. The only difference from Example 1 is that the quartz sand in the core proppant is replaced with 40 / 70 mesh crushed nutshell particles, and the amount of sodium α-olefin sulfonate added is 0.25 parts.

[0070] Example 7

[0071] Example 7 provides a method for preparing a self-suspending support based on a nanocellulose composite coating. The only difference from Example 1 is that 0.18 parts of sodium α-olefin sulfonate are replaced with 0.18 parts of sodium fatty alcohol polyoxyethylene ether sulfate.

[0072] Example 8

[0073] Example 8 provides a method for preparing a self-suspending proppant based on a nanocellulose composite coating. The only difference from Example 1 is that 0.18 parts of sodium α-olefin sulfonate are replaced with 0.18 parts of sodium lignin sulfonate.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a self-suspending proppant. The only difference from Example 1 is that sodium α-olefin sulfonate is not added, in order to verify the effect of not adding a network viscoelasticity enhancer on the technical effect.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a self-suspending proppant. The only difference from Example 1 is that TEMPO-oxidized cellulose nanoparticles were not added, in order to verify the impact of not adding TEMPO-oxidized cellulose nanoparticles on the technical effect.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing a self-suspending proppant. The only difference from Example 1 is that no associative polymer is added, in order to verify the impact of not adding the associative polymer on the technical effect.

[0080] To better understand the present invention, the self-suspending proppants obtained in Examples 1-8 and Comparative Examples 1-3 were tested using the following methods:

[0081] Test Example 1

[0082] This test example examines the suspension performance of the self-suspending proppants obtained in the above embodiments and comparative examples. The test method is as follows:

[0083] The self-suspended proppant obtained in the above examples and comparative examples was added to a 250mL beaker with 150mL of water at a sand ratio of 20%, and mechanical stirring was started at 600r / min. The proppant was then added to the water within 10s, and stirring was continued for 5min to obtain the sand-carrying solution. The solution was then allowed to stand at 25℃ or 90℃, and the distribution of the proppant in the water was observed. The suspension time was recorded as the time required for the proppant to completely settle. Figure 5 As shown, Figure 5 The figure shows the static suspension state of the self-suspending proppant prepared in Example 1 in clear water. As can be seen from the figure, the proppant achieves a complete suspension state in clear water, indicating the excellent static suspension performance of the self-suspending proppant. The test results are shown in Table 1, using the figure as the test standard.

[0084]

[0085] As shown in the table, in Examples 1-8 above, under the condition of preparing the sand-carrying solution with clean water, when the amount of associative polymer in the proppant reaches 0.8 parts, a full suspension state of more than 80 hours can be achieved. Comparing Example 1 and Comparative Example 1, since Comparative Example 1 did not add sodium α-olefin sulfonate, its self-suspension time was much shorter than that of Example 1, indicating that there is a synergistic effect between the network viscoelastic reinforcing agent and the associative polymer, which can improve the static suspension ability of the proppant and is the key factor to achieve long-term full suspension of the proppant in clean water; while Comparative Example 3 did not add the associative polymer, resulting in almost no self-suspension ability, indicating that the network viscoelastic reinforcing agent is only an additive to improve the viscosity of the polymer and does not have the ability to suspend the proppant itself; comparing Example 1 and Comparative Example 2, since Comparative Example 2 did not add TEMPO oxidized nanocellulose, its suspension time decreased by more than 40 hours, indicating that TEMPO oxidized nanocellulose, as a nano-reinforcing filler, has a synergistic effect on the associative polymer, which is beneficial to maintaining the suspension time of the proppant.

[0086] The self-suspended proppant obtained in the above examples and comparative examples was added to a 250 mL beaker with 150 mL of standard saline solution (the saline solution had a salinity of 35000 mg / L) at a sand ratio of 20%. Mechanical stirring was started at 600 rpm, and the proppant was added to water within 10 seconds. The mixture was stirred for 5 minutes to obtain a sand-carrying solution. The solution was allowed to stand at 25°C, and the distribution of the proppant in the water was observed. The time required for the proppant to completely settle was recorded as the suspension time. The test results are shown in Table 2.

[0087]

[0088] As can be seen from Examples 1-8 above, high-salinity brine reduces the suspension capacity of the proppant, but increasing the amount of polymer can still achieve a long-term self-suspension state of the proppant. This indicates that the self-suspension proppant prepared by the present invention has the ability to resist high temperature and high salt, has good suspension effect, supports longer fracture length, and helps to improve oil and gas recovery rate.

[0089] Test Example 2

[0090] This test example examines the bonding performance of the self-suspending proppants obtained in the above embodiments and comparative examples. The test method is as follows:

[0091] The self-suspending proppants obtained in the above examples and comparative examples were sieved using a 70-mesh sieve at room temperature several days after the preparation of the self-suspending proppants. The mass of the network viscoelastic reinforcing agent and associative polymer powder that fell off the proppants was also weighed. The test results are shown in Table 3.

[0092]

[0093] As can be seen from Examples 1-8 above, the mass of powder falling off the self-suspending proppant is consistently controlled at around 0.02g, and remains almost unchanged over time, indicating that the self-suspending proppant exhibits good stability. Furthermore, the nanocellulose composite coating provides excellent adhesion between the network viscoelastic reinforcing agent and the associative polymer powder, ensuring their firm attachment to the core proppant. As can be seen from Examples 1 and Comparative Example 2 above, with the same amount of powder added, the proppant without nanocellulose produces more powder falling off, indicating that the nanocellulose composite coating offers improved bonding strength compared to the polyvinyl alcohol aqueous solution.

[0094] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0095] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A self-suspending proppant based on nanocellulose composite coating, characterized in that, The self-suspending proppant is composed of 0.1%-0.3% of a reticulated viscoelastic reinforcing agent and 0.4%-2% of an associated polymer adhered to 96%-98.5% of a core proppant by a 0.5%-2% nanocellulose composite coating; The reticulated viscoelastic reinforcing agent is at least one of sodium lignosulfonate, sodium fatty alcohol polyoxyethylene ether sulfate and sodium alpha-alkenyl sulfonate; The nanocellulose composite coating is composed of a mixed aqueous solution of polyvinyl alcohol and TEMPO-oxidized nanocellulose; The core proppant is at least one of quartz sand, ceramsite, crushed nutshell particles, hollow glass microbeads, metal particles and pre-coated film proppant. The structural formula of the associated polymer is as follows: ； In the formula, a is 57%-62%, b is 17%-36%, m is 3%-12%, n is 2%-7%, o is 0.5%-3%, p is 0.5%-2%, R1 is a hydrophobic functional monomer 1, and R2 is a hydrophobic functional monomer 2, all in terms of mass percentage. The hydrophobic functional monomer 1 is one of 2-acrylamide triethoxy dimethyl dodecyl ammonium chloride, ethyl acrylate dimethyl dodecyl ammonium chloride and ethyl acrylate dimethyl hexadecyl ammonium chloride; and the hydrophobic functional monomer 2 is one of 2-acrylamide dodecyl sodium sulfonate and 2-acrylamide dodecyl disodium sulfonate.

2. The self-suspending proppant of claim 1, wherein, The preparation of the nanocellulose composite coating comprises: The polyvinyl alcohol powder is added to deionized water for stirring to obtain a polyvinyl alcohol aqueous solution, and the TEMPO-oxidized nanocellulose is added to the polyvinyl alcohol aqueous solution for mixing to obtain the nanocellulose composite coating.

3. The self suspending proppant of claim 2, wherein In the formula, a is 57%-62%, b is 17%-36%, m is 3%-12%, n is 2%-7%, o is 0.5%-3%, p is 0.5%-2%, R1 is a hydrophobic functional monomer 1, and R2 is a hydrophobic functional monomer 2, all in terms of mass percentage. The polyvinyl alcohol powder and the TEMPO-oxidized nanocellulose have a mass ratio of 10: (2-5).

4. The self suspending proppant of claim 2, wherein, The polyvinyl alcohol has an alcoholysis degree of 86.5 mol%-89 mol%, and the TEMPO-oxidized nanocellulose has a solid content of 1%-4%.

5. The self suspending proppant of claim 2, wherein, The stirring rate of the polyvinyl alcohol powder added to deionized water for stirring is 600-800 r / min, and the concentration of the polyvinyl alcohol aqueous solution is 5 wt%-15 wt%.

6. The self suspending proppant of claim 1, wherein, The pre-coated film proppant is at least one of an epoxy resin coated film proppant, a phenolic resin coated film proppant, a polyurethane resin coated film proppant and a modified resin coated film proppant.

7. A method of making a self-suspending proppant as claimed in any one of claims 1-6, characterized by, The preparation method of the self-suspending proppant comprises the following steps: The nanocellulose composite coating is sprayed onto the core proppant and uniformly stirred for 1-2 min, and the reticulated viscoelastic reinforcing agent and the associated polymer are added and uniformly stirred to obtain the self-suspending proppant.

8. The method of claim 7, wherein, The particle size of the reticulated viscoelastic reinforcing agent and the associated polymer is 120 / 140 mesh.

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