Double-network fracturing fluid thickening agent with high salt resistance and shear resistance and preparation method thereof

Abstract

The invention discloses a high-salt-resistant and shear-resistant dual-network fracturing fluid thickening agent and a preparation method thereof, and relates to the technical field of oilfield chemistry and fine chemistry, a nonionic monomer and a cross-linking agent are subjected to cross-linking polymerization under the action of an initiator to form a first network structure, and a flexible polymer filled in the first network structure is utilized to form a second network structure. Wherein the flexible polymer is alkylphenol polyoxyethylene ether. A flexible connecting segment in an alkylphenol polyoxyethylene ether structure still retains the function of serving as a sacrificial bond, and can absorb the damage of high shear and high temperature to a rigid network structure, so that the system still has good tolerance performance under the condition of no metal crosslinking. Meanwhile, due to the existence of a benzene ring in an alkylphenol polyoxyethylene ether structure, a pi-pi accumulation effect can be increased on the original basis, and an intermolecular acting force is enhanced, so that the tolerance of a dual-network structure is further improved. The dual-network fracturing fluid thickening agent is simple to prepare and excellent in performance, and has better practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield chemistry and fine chemistry, in particular to a high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for oil and gas and the continuous improvement of oil and gas exploration and development level, low-porosity and low-permeability reservoirs have become the main target and technical research object of exploration and development. Hydraulic fracturing technology is an important technical measure for increasing production of oil and gas wells and injection of water injection wells. With the large-scale development of low-permeability oil and gas reservoirs in China, the performance research of fracturing fluid is becoming more and more important. The performance of fracturing fluid not only directly affects the success rate of fracturing operation, but also has a great influence on the fracturing effect. When developing low-permeability oil and gas fields by using fracturing technology, if sea water or oilfield produced water is used to prepare fracturing fluid, the cost can be greatly reduced, but sea water or oilfield produced water has high salinity, so it is urgent to develop a fracturing fluid system suitable for high salinity environment. Thickening agent is one of the most basic additives in fracturing fluid, and its thickening ability, thermal stability and shear stability are the main indicators for evaluating its quality, and are also one of the most important factors affecting the performance of fracturing fluid and the fracturing effect.

[0003] The inventor's prior patent CN109438618A discloses a temperature-resistant and salt-resistant double-network structure fracturing fluid thickening agent and a preparation method thereof. The temperature-resistant and salt-resistant double-network structure fracturing fluid thickening agent is formed by reacting a non-ionic monomer and a crosslinking agent to form a first network structure, and a salt-resistant monomer filled in the first network structure to form a second network structure. The fracturing fluid thickening agent exhibits excellent temperature-resistant and shear-resistant performance. Under a salinity of up to 300000ppm, it can still maintain its viscosity preferably. Under the condition of 120℃, 170s -1 of shear for 1h, the viscosity is reduced by about 50% compared with 10min, and finally stabilized at 200mPa·s. In CN112574735A, a functional polymer polyvinyl ester substance is used to replace the salt-resistant monomer, which effectively improves the temperature-resistant performance of the fracturing fluid thickening agent. In the past research, it is found that there is still great potential for the double-network structure fracturing fluid thickening agent, and it is imperative to continuously improve it to develop a new generation of products with more excellent performance. SUMMARY

[0004] The purpose of the present application is to provide a high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent, which has a novel structure and excellent performance, and exhibits better salt-resistant and shear-resistant performance compared with the prior art.

[0005] Another object of the present application is to provide a preparation method of the high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent, which is simple and convenient to operate and can be used to quickly and efficiently prepare the high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent.

[0006] Embodiments of the present application are implemented as follows: The high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent comprises a first network structure formed by cross-linking polymerization of non-ionic monomers and a cross-linking agent under the action of an initiator, and a second network structure composed of flexible polymers filled in the first grid structure; wherein the non-ionic monomers are at least one of acrylamide and modified acrylamide, and the flexible polymers are alkyl phenol polyoxyethylene ether.

[0007] The preparation method of the double-network fracturing fluid thickening agent comprises the following steps: The non-ionic monomers, the flexible polymers, and the cross-linking agent are mixed under an inert atmosphere to obtain a raw material mixture; The raw material mixture is mixed with the initiator, and cross-linking polymerization reaction is carried out under an inert atmosphere.

[0008] The beneficial effects of the embodiments of the present application are as follows: The embodiments of the present application provide a high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent and a preparation method thereof, which forms a first network structure by cross-linking polymerization of non-ionic monomers and a cross-linking agent under the action of an initiator, and forms a second network structure by filling flexible polymers in the first grid structure. The non-ionic monomers are at least one of acrylamide and modified acrylamide, and the flexible polymers are alkyl phenol polyoxyethylene ether. The flexible segment in the structure of alkyl phenol polyoxyethylene ether still retains the function of being a "sacrificial bond", which can absorb the damage of high shear and high temperature to the rigid network structure, so that the system can still have good resistance performance without metal cross-linking. At the same time, due to the presence of benzene rings in the structure of alkyl phenol polyoxyethylene ether, the π-π stacking effect can be increased on the basis of the original, and the intermolecular force can be strengthened, so that the resistance of the double-network structure is further improved. The double-network fracturing fluid thickening agent is simple to prepare, has excellent performance, and has good practical value. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0010] Figure 1The results of the influence of monovalent potassium ions on the viscosity of the fracturing fluid thickening agent provided in Test Example 1 of the present application, wherein the ordinate represents viscosity (unit: mPa·s) and the abscissa represents salinity (unit: ×10 4 ppm); Figure 2 The results of the influence of divalent calcium ions on the viscosity of the fracturing fluid thickening agent provided in Test Example 1 of the present application, wherein the ordinate represents viscosity (unit: mPa·s) and the abscissa represents salinity (unit: ×10 4 ppm). DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the reagents or instruments used are not specified by the manufacturers, they are all conventional products that can be obtained by market purchase.

[0012] The high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent, the preparation method and the application thereof will be described in detail below.

[0013] The high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent comprises a first network structure formed by cross-linking polymerization of non-ionic monomers and a cross-linking agent under the action of an initiator, and a second network structure composed of a flexible polymer filled in the first network structure; wherein the non-ionic monomer is at least one of acrylamide and modified acrylamide, and the flexible polymer is an alkyl phenol polyoxyethylene ether.

[0014] The flexible segment in the structure of the alkyl phenol polyoxyethylene ether still retains the function of a "sacrificial bond", which can absorb the damage of high shear and high temperature to the rigid network structure, so that the system can still have good tolerance performance without metal cross-linking. At the same time, due to the presence of benzene rings in the structure of the alkyl phenol polyoxyethylene ether, the π-π stacking effect can be increased on the basis of the original, and the intermolecular force is strengthened, so that the tolerance of the double-network structure is further improved.

[0015] Alternatively, the alkyl phenol polyoxyethylene ether comprises at least one of nonyl phenol polyoxyethylene ether, octyl phenol polyoxyethylene ether and dodecyl phenol polyoxyethylene ether. These alkyl phenol polyoxyethylene ethers are all mature products that can be directly obtained in the market, and the raw material sources are more extensive.

[0016] Further, the modified acrylamide includes N-aryl acrylamide. The N-aryl acrylamide is a product in which the N-H bond on the amino group of acrylamide is replaced by an aryl compound, including a phenyl group and a substituted phenyl group, which is a product in which the hydrogen on the benzene ring is replaced by an alkyl group, an alkoxy group, a hydroxyl group, an amino group, a nitro group, a halogen, or the like, and can be a monosubstituted product or a polysubstituted product. Alternatively, the modified acrylamide is at least one of N-phenyl acrylamide, N-(4-aminophenyl) acrylamide, N-(2-aminophenyl) acrylamide, 3-nitro-N-acrylaniline, N-(2-chlorophenyl) acrylamide, N-(4-chlorophenyl) acrylamide, and N-(p-tolyl) acrylamide, all of which are commercially available raw materials and are more widely available. By introducing a benzene ring into the modified acrylamide, a benzene ring can also exist in the first network structure, so that the flexible compound in the second network structure can also be subjected to π-π stacking, further strengthening the intermolecular force.

[0017] Further, as the content of the benzene ring increases, the viscosity of the entire system increases after the intermolecular force is strengthened, and during the crosslinking reaction, a mixture of acrylamide and modified acrylamide can be used as a non-ionic monomer to copolymerize to form the first network structure. The viscosity range of the entire system can be adjusted by adjusting the ratio between acrylamide and modified acrylamide.

[0018] Alternatively, the crosslinking agent is N,N'-methylenebisacrylamide. The crosslinking agent can form a covalent bridge between the polymer chains to form a network structure. The initiator is at least one of ammonium persulfate, potassium persulfate, and sodium percarbonate. The initiator is used to initiate the free radical reaction.

[0019] The embodiment of the present application also provides a preparation method of the above-mentioned double-network fracturing fluid thickening agent, which comprises: S1. Mixing the non-ionic monomer, the flexible polymer, and the crosslinking agent in an inert atmosphere to obtain a raw material mixture.

[0020] S2. Mixing the raw material mixture with the initiator and performing a crosslinking polymerization reaction in an inert atmosphere.

[0021] Further, the inert atmosphere can be obtained by using nitrogen, helium, argon, or the like. The inert gas is directly introduced into the reaction container to remove oxygen.

[0022] Optionally, the concentration of the nonionic monomer in the dual-network fracturing fluid thickening agent is 2.5wt%-5wt%. When the concentration of the nonionic monomer is low, the degree of polymerization is low or even no polymerization occurs; when the concentration of the nonionic monomer is too high, the system forms a solid gel with poor fluidity. The inventors have found through tests that when the concentration is in the range of 2.5wt%-5wt%, the viscosity, fluidity, solubility and other comprehensive properties of the product are better.

[0023] Further, the mass ratio of the nonionic monomer, the flexible polymer, the crosslinking agent and the initiator is 1:(0.05-0.1):(0.0002-0.0005):(0.025-0.05). The crosslinking agent has a great influence on the viscosity of the system by crosslinking the linear polymer chain segments to form a network structure. When the amount of the crosslinking agent is too small, the network structure formed is sparse and unstable; when the amount of the crosslinking agent is too large, the network structure is tightly entangled, resulting in loss of fluidity of the system and complete solidification. The flexible polymer is used to form a second network structure. When the amount of the flexible polymer is too small, the dual-network structure is difficult to form, resulting in poor stability of the dual-network structure and low viscosity; when the amount of the flexible polymer is too large, the density of the flexible network segments entangled on the rigid structure is too high, resulting in that the molecular chains of the system cannot freely extend. Through condition screening, when the ratio is in the above range, the viscosity of the product formed is moderate and the overall performance is better.

[0024] Optionally, the temperature for mixing the nonionic monomer, the flexible polymer and the crosslinking agent is 80-90℃, the mixing time is 1-3h, and after mixing is completed, the mixture is cooled to room temperature for use. Under this condition, the substances can be fully dispersed and mixed more uniformly.

[0025] Further, the crosslinking polymerization reaction is carried out at 30-50℃ for 20-30h. The free radical polymerization reaction is an exothermic reaction, and low temperature is conducive to obtaining high-viscosity polymers with high molecular weight, but the decomposition rate and conversion rate of the initiator are low, and low-viscosity polymers or even no polymerization occurs; and when the temperature is too high, the free radical chain coupling termination of the initiator is accelerated, and the viscosity of the system is reduced. Under the above temperature and reaction time, the reaction effect is better.

[0026] The features and properties of the application are further described in detail below in combination with examples.

[0027] Example 1

[0028] This example provides a high-salt-resistant and shear-resistant dual-network fracturing fluid thickening agent, and a preparation method thereof is as follows: S1. Add deionized water and nonylphenol polyoxyethylene ether into a reaction kettle in sequence, heat to 90℃, stir for 2h to dissolve, and then cool to room temperature; add N-phenylacrylamide, stir for 5min, and then add N,N'-methylenebisacrylamide, stir for 5min, and then introduce nitrogen into the reaction kettle.

[0029] S2. Stop introducing nitrogen after 1h, add potassium persulfate, stir for 2min, heat to 30℃, and then continue to react for 30h under nitrogen atmosphere to obtain the double network fracturing fluid thickening agent.

[0030] The concentration of N-phenylacrylamide is 2.5wt%, and the mass ratio of N-phenylacrylamide, nonylphenol polyoxyethylene ether, N,N'-methylenebisacrylamide and potassium persulfate is 1:0.05:0.0003:0.04.

[0031] Example 2

[0032] The embodiment provides a high-salt-resistant and shear-resistant double network fracturing fluid thickening agent, and a preparation method thereof. S1. Add deionized water and nonylphenol polyoxyethylene ether into a reaction kettle in sequence, heat to 90℃, stir for 2h to dissolve, and then cool to room temperature; add N-phenylacrylamide, stir for 5min, and then add N,N'-methylenebisacrylamide, stir for 5min, and then introduce nitrogen into the reaction kettle.

[0033] S2. Stop introducing nitrogen after 1h, add potassium persulfate, stir for 2min, heat to 30℃, and then continue to react for 30h under nitrogen atmosphere to obtain the double network fracturing fluid thickening agent.

[0034] The concentration of N-phenylacrylamide is 2.5wt%, and the mass ratio of N-phenylacrylamide, nonylphenol polyoxyethylene ether, N,N'-methylenebisacrylamide and potassium persulfate is 1:0.05:0.0003:0.04.

[0035] Example 3

[0036] The embodiment provides a high-salt-resistant and shear-resistant double network fracturing fluid thickening agent, and a preparation method thereof. S1. Add deionized water and nonylphenol polyoxyethylene ether into a reaction kettle in sequence, heat to 90℃, stir for 2h to dissolve, and then cool to room temperature; add N-phenylacrylamide, stir for 5min, and then add N,N'-methylenebisacrylamide, stir for 5min, and then introduce nitrogen into the reaction kettle.

[0037] S2. Stop introducing nitrogen after 1h, add potassium persulfate, stir for 2min, heat to 30℃, and then continue to react for 30h under nitrogen atmosphere to obtain the double network fracturing fluid thickening agent.

[0038] The concentration of N-(2-chlorophenyl) acrylamide is 4wt%, and the mass ratio of N-(2-chlorophenyl) acrylamide, octylphenol polyoxyethylene ether, N,N'-methylene bisacrylamide, and ammonium persulfate is 1:0.05:0.0002:0.025.

[0039] Example 4

[0040] The embodiment provides a high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent, and a preparation method thereof. S1. Deionized water and octylphenol polyoxyethylene ether are sequentially added to a reaction kettle, heated to 80 DEG C, and stirred for 1h for dissolution, and then cooled to room temperature; N-(2-chlorophenyl) acrylamide is added, stirred for 5min, and then N,N'-methylene bisacrylamide is added, stirred for 5min, and nitrogen is introduced into the reaction kettle.

[0041] S2. After 1h, the nitrogen introduction is stopped, ammonium persulfate is added and stirred for 2min, the temperature is increased to 40 DEG C, and the reaction is continued for 24h under a nitrogen atmosphere, to obtain the double-network fracturing fluid thickening agent.

[0042] The concentration of N-(2-chlorophenyl) acrylamide is 4wt%, and the mass ratio of N-(2-chlorophenyl) acrylamide, octylphenol polyoxyethylene ether, N,N'-methylene bisacrylamide, and ammonium persulfate is 1:0.05:0.0002:0.025.

[0043] Example 5

[0044] The embodiment provides a high-salt-resistant and shear-resistant double-network fracturing fluid thickening agent, and a preparation method thereof. S1. Deionized water and octylphenol polyoxyethylene ether are sequentially added to a reaction kettle, heated to 80 DEG C, and stirred for 1h for dissolution, and then cooled to room temperature; N-(2-chlorophenyl) acrylamide is added, stirred for 5min, and then N,N'-methylene bisacrylamide is added, stirred for 5min, and nitrogen is introduced into the reaction kettle.

[0045] S2. After 1h, the nitrogen introduction is stopped, ammonium persulfate is added and stirred for 2min, the temperature is increased to 40 DEG C, and the reaction is continued for 24h under a nitrogen atmosphere, to obtain the double-network fracturing fluid thickening agent.

[0046] The concentration of N-(2-chlorophenyl) acrylamide is 4wt%, and the mass ratio of N-(2-chlorophenyl) acrylamide, octylphenol polyoxyethylene ether, N,N'-methylene bisacrylamide, and ammonium persulfate is 1:0.05:0.0002:0.025.

[0047] Comparative Example 1 This comparative example provides a dual-network fracturing fluid thickener, the preparation method of which is basically the same as that of Example 1, except that dodecylphenol polyoxyethylene ether is replaced with an equal amount of isotridecyl alcohol polyoxyethylene ether.

[0048] Comparative Example 2 This comparative example provides a dual-network fracturing fluid thickener, the preparation method of which is basically the same as that of Example 1, except that dodecylphenol polyoxyethylene ether is replaced with an equal amount of polyvinyl alcohol formate.

[0049] Comparative Example 3 This comparative example provides a fracturing fluid thickener, the preparation method of which is basically the same as that of Example 1, except that dodecylphenol polyoxyethylene ether is not added.

[0050] Experimental Example 1 This experiment used the fracturing fluid thickeners provided in Examples 1, 2, and 5, as well as Comparative Examples 1-3, diluted with monovalent potassium ion brine to a nonionic monomer concentration of 0.84 wt%. The viscosity of each sample was then tested under different salinity conditions. The test results are as follows: Figure 1 As shown.

[0051] Depend on Figure 1 It can be seen that Comparative Example 1 and Comparative Example 2, which use flexible polymers without benzene rings to form the second network structure, have similar viscosities. Within the range of potassium ion salinity of 0–300,000 ppm, the viscosity fluctuates mainly within the range of 52–58 mPa·s, indicating that potassium ions have little impact on them. However, within the range of 300,000–450,000 ppm, the viscosity of both fracturing fluid thickeners shows a significant decrease. This indicates that as the dual network structure adsorbs more potassium ions, the adsorption amount gradually exceeds its upper limit, and the dual network structure collapses to some extent.

[0052] In contrast, the alkylphenol polyoxyethylene ether used in Example 1 of this invention can enhance the intermolecular forces through π-π stacking. The enhanced intermolecular forces result in a higher initial viscosity of Example 1, reaching 62.1 mPa·s, at the same nonionic monomer concentration. Furthermore, Example 1 has a higher upper limit, with the viscosity only showing a significant decreasing trend when the potassium ion mineralization reaches above 400,000 ppm.

[0053] Based on Example 1, Example 2 also introduces a benzene ring structure into the structure of the nonionic monomer, resulting in stronger intermolecular forces. Not only did the initial viscosity reach 72.3 mPa·s, but even with a potassium ion mineralization of up to 450,000 ppm, the viscosity did not show a significant decreasing trend.

[0054] Example 5 used two nonionic monomers copolymerized to form the first network structure. It can be seen that its initial viscosity is between that of Example 1 and Example 2, and it also exhibits good salt resistance. This demonstrates that it is possible to adjust the viscosity by changing the benzene ring content in the nonionic monomers.

[0055] Comparative Example 3 provides a single-network fracturing fluid thickener without flexible polymers, which shows an overall decreasing viscosity in the range of 0~450000ppm of salinity, decreasing from the initial 38.0mPa·s to 20.5mPa·s, but has poor salt resistance.

[0056] Experimental Example 2 This experiment used the fracturing fluid thickeners provided in Examples 1, 2, and 5, as well as Comparative Examples 1-3, diluted with divalent calcium ion brine to a nonionic monomer concentration of 0.84 wt%. The viscosity of each sample was then tested under different salinity conditions. The test results are as follows: Figure 2 As shown.

[0057] from Figure 2 As can be seen, the viscosity change caused by divalent calcium ions is very similar to that caused by monovalent potassium ions. The fracturing fluid thickeners provided in Comparative Examples 1 and 2 also showed a significant decreasing viscosity when the salinity reached above 300,000 ppm. However, the embodiments of the present invention successfully increased the salt tolerance limit of the fracturing fluid thickener to above 450,000 ppm by introducing π-π stacking effect.

[0058] Unlike Example 1, the viscosity of the fracturing fluid thickener with a dual-network structure exhibited a sharp increase from its initial viscosity when the calcium ion salinity was 100,000 ppm, with an increase of approximately 40% to 50%. As the salinity continued to increase, the viscosity then returned to a value close to the initial viscosity. This phenomenon was not observed in the fracturing fluid thickener with a single-network structure (Comparative Example 3).

[0059] Experimental Example 3 This experiment used the fracturing fluid thickeners provided in Examples 1, 2, and 5, as well as Comparative Examples 1-3, at 25°C for 170 seconds. -1 The viscosity after shearing for 5 min was taken as the initial viscosity, and the viscosity after continuous shearing for 120 min at 160℃ was taken as the final viscosity. The ratio of the final viscosity to the initial viscosity was used as the viscosity retention rate for viscosity comparison. The comparison results are shown in Table 1.

[0060] Table 1. Comparison of viscosity retention rates Initial viscosity / mPa s Final viscosity / mPa s Viscosity retention Example 1 212 153 72.2% Example 2 224 165 73.7% Example 5 246 186 75.6% Comparative Example 1 175 125 71.4% Comparative Example 2 190 132 69.5% Comparative Example 3 138 31 22.5% As can be seen from Table 1, due to the influence of π-π stacking, the intermolecular force of the embodiments of the present application is enhanced, so the initial viscosity of Examples 1, 2 and 5 is significantly improved compared with the comparative examples, and the viscosity increases with the increase of the amount of benzene ring introduced.

[0061] Similarly, due to the strengthening of the intermolecular force, the fracturing fluid thickening agent provided by the embodiments of the present application exhibits stronger high-temperature shear resistance, and the viscosity retention rate can reach 72.2% or more, and the viscosity retention rate further increases with the increase of the amount of benzene ring introduced, and the highest is 75.6%.

[0062] Comparative Example 1 and Comparative Example 2 use flexible polymers without benzene rings, wherein the initial viscosity of Comparative Example 1 is reduced to 175 mPa·s, and the viscosity retention rate is reduced to 71.4%. The initial viscosity of Comparative Example 2 is reduced to 190 mPa·s, and the viscosity retention rate is reduced to 69.5%. Although both still have certain high-temperature shear resistance, their initial viscosity and viscosity retention rate cannot reach the level of the embodiments of the present application. In addition, the high-temperature shear resistance of the single network system of Comparative Example 3 is completely incomparable with the double network, and the viscosity retention rate is only 22.5%. Again, it is confirmed that the double network fracturing fluid thickening agent is significantly better than the single network system.

[0063] In summary, the embodiments of the present application provide a high-salt-resistant and shear-resistant double network fracturing fluid thickening agent and a preparation method thereof, which forms a first network structure by cross-linking polymerization of a non-ionic monomer and a cross-linking agent under the action of an initiator, and a second network structure composed of a flexible polymer filled in the first grid structure. The non-ionic monomer is at least one of acrylamide and modified acrylamide, and the flexible polymer is an alkyl phenol polyoxyethylene ether. The flexible segment in the structure of the alkyl phenol polyoxyethylene ether still retains the function of being a "sacrificial bond" and can absorb the damage of high shear and high temperature to the rigid network structure, so that the system can still have good resistance performance without metal cross-linking. At the same time, due to the presence of benzene rings in the structure of the alkyl phenol polyoxyethylene ether, the π-π stacking effect can be increased on the basis of the original, the intermolecular force is strengthened, and the resistance of the double network structure is further improved. The double network fracturing fluid thickening agent is simple to prepare, has excellent performance, and has better practical value.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high salt-tolerant and shear-tolerant dual-network fracturing fluid viscosifier, characterized in that, The first network structure is formed by cross-linking and polymerization of non-ionic monomers and cross-linking agents under the action of an initiator, and the second network structure is formed by a flexible polymer filled in the first network structure; wherein the non-ionic monomers are at least one of acrylamide and modified acrylamide, and the flexible polymer is an alkyl phenol polyoxyethylene ether; The concentration of the non-ionic monomers in the double-network fracturing fluid thickening agent is 2.5wt%-5wt%, and the mass ratio of the non-ionic monomers to the flexible polymer is 1:(0.05-0.1).

2. The dual network frac fluid viscosifier of claim 1, wherein, The alkyl phenol polyoxyethylene ether includes at least one of nonyl phenol polyoxyethylene ether, octyl phenol polyoxyethylene ether, and dodecyl phenol polyoxyethylene ether.

3. The dual network frac fluid viscosifier of claim 1, wherein, The modified acrylamide includes N-aryl acrylamide.

4. The dual network frac fluid viscosifier of claim 1, wherein, The cross-linking agent is N,N'-methylene bisacrylamide.

5. The dual network frac fluid viscosifier of claim 1, wherein, The initiator is at least one of ammonium persulfate, potassium persulfate, and sodium percarbonate.

6. A method of preparing the dual-network fracturing fluid viscosifier according to any one of claims 1 to 5, characterized in that, The method comprises: Mixing the non-ionic monomers, the flexible polymer, and the cross-linking agent in an inert atmosphere to obtain a raw material mixture; Mixing the raw material mixture with the initiator and performing cross-linking polymerization reaction in an inert atmosphere.

7. The production method according to claim 6, characterized by, The mass ratio of the non-ionic monomers, the cross-linking agent, and the initiator is 1:(0.0002-0.0005):(0.025-0.05).

8. The method of claim 7, wherein, The mixing temperature of the non-ionic monomers, the flexible polymer, and the cross-linking agent is 80-90℃, the mixing time is 1-3h, and after the mixing is completed, the mixture is cooled to room temperature for use.

9. The production method according to claim 8, characterized by, The cross-linking polymerization reaction is performed at 30-50℃, and the reaction time is 20-30h.

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