Fracturing fluid and preparation method thereof

Abstract

The invention relates to the technical field of oil and gas field development, in particular to fracturing fluid and a preparation method thereof.The fracturing fluid is prepared from, by mass, 1.0%-1.2% of polymer thickening agents, 0.3%-0.5% of oil displacement agents, 0.02%-0.05% of gel breakers, 0.5%-1.0% of anti-swelling agents and the balance water; the polymer thickening agent is a pentabasic polymer, and reaction monomers of the polymer thickening agent comprise acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride and ethyl acrylic acid. The fracturing fluid provided by the invention is a polymer fracturing fluid system and has good temperature resistance; the pentabasic polymer thickening agent can have good compatibility with an oil washing agent, a fracturing fluid system has the advantages of dialysis replacement, forced oil washing and the like, the purposes of high sand carrying performance, low filtration loss, low surface and interface tension, high oil displacement effect and high flowback rate are achieved on the premise that the temperature resistance and the sand carrying performance of the fracturing fluid are guaranteed, the fracturing yield increasing effect is improved, and the fracturing cost is reduced. The method plays an important role in popularization of a novel efficient fracturing fluid system and efficient yield increase.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a fracturing fluid and its preparation method. Background Technology

[0002] As development progresses, fracturing has become a crucial measure to increase single-well production in old oilfields and achieve profitable production in new areas, making fracturing fluids paramount. Plant-based fracturing fluids are the most widely used, possessing excellent proppant-carrying capacity, but their high residue content after breaking down the gel can significantly damage the reservoir. Clean fracturing fluids have almost zero residue content and cause minimal reservoir damage, but their temperature resistance and proppant-carrying capacity are weaker. Polymer fracturing fluids have low residue content and good temperature resistance, but their proppant-carrying capacity is relatively weak. For low-permeability reservoirs, characterized by low reservoir permeability, low formation pressure, and high pore capillary pressure, the remaining oil is dispersed and difficult to migrate. Since conventional fracturing fluids primarily function to create fractures and carry proppant, their relatively high interfacial tension means that even after fracturing, although supported fractures are formed, crude oil cannot migrate effectively, resulting in unsatisfactory production increases.

[0003] Existing fracturing fluid systems that function as both fracturing fluid and oil displacement agent are clean fracturing fluid systems. Although they have the functions of dialysis displacement and forced oil washing, their temperature resistance is poor. Existing polymer fracturing fluid systems function to create fractures and carry proppant. The polymer thickeners are mostly binary, ternary, and quaternary polymers, mainly temperature- and salt-resistant polymers. Polymer fracturing fluids do not have the functions of dialysis displacement and forced oil washing. Summary of the Invention

[0004] Based on this, the present invention proposes a fracturing fluid and its preparation method, which has advantages such as dialysis displacement and forced oil washing. Under the premise of ensuring the temperature resistance and sand carrying capacity of the fracturing fluid, it achieves the goals of high sand carrying capacity, low filtration loss, low interfacial tension, high oil displacement effect and flowback rate, thereby further improving the production enhancement effect of fracturing stimulation.

[0005] According to a first aspect of the present invention, a fracturing fluid is provided, comprising, by mass fraction percentage: 1.0-1.2% polymer thickener, 0.3-0.5% oil displacement agent, 0.02-0.05% breaker, 0.5-1.0% anti-swelling agent, and the remainder being water;

[0006] The polymer thickener is a pentagonal polymer, and the reactive monomers of the polymer thickener include: acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid.

[0007] According to an embodiment of the present invention, the polymer thickener comprises, by mass percentage, the following components: 20-25% acrylamide, 5-10% methyl acrylate, 8-10% 2-acrylamide-2-methylpropanesulfonic acid, 5-8% divinyl ammonium chloride, 2-5% ethyl acrylic acid, with the remainder being water; and 0.02-0.03% azodicyano acid by mass percentage of the total reactant monomers.

[0008] According to an embodiment of the present invention, the mass ratio of acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid in the reactive monomers of the polymer thickener is 1-1.25: 0.25-0.5: 0.4-0.5: 0.25-0.4: 0.1-0.25.

[0009] According to an embodiment of the present invention, the anti-swelling agent is one or a mixture of quaternary ammonium salt and polyoxyethylene amine in any proportion.

[0010] According to an embodiment of the present invention, the de-gluing agent is one of ammonium persulfate, potassium persulfate, sodium persulfate, or a mixture of two in any proportion.

[0011] According to embodiments of the present invention, the oil displacement agent is one or a mixture of alkoxysulfonate, alkoxysulfate salt, and alkoxycarboxylate salt in any proportion.

[0012] According to a second aspect of the present invention, a method for preparing the above-described fracturing fluid is provided, comprising the following steps:

[0013] While stirring, the polymer thickener powder, oil displacement agent, degumming agent, and anti-swelling agent are added to the water in the following mass ratios, stirring continuously until the reagents are dissolved to obtain a semi-finished product.

[0014] The pH value of the semi-finished product is adjusted to 6-8 using a pH adjuster to obtain the fracturing fluid.

[0015] According to an embodiment of the present invention, the pH adjuster is a sodium bicarbonate buffer system.

[0016] According to an embodiment of the present invention, the polymer thickener powder is prepared by the following steps:

[0017] Solution A is prepared by dissolving the reactants acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid in water.

[0018] Add the solution A to the reaction vessel, set the reaction temperature to 20-30℃, and purge with nitrogen gas for 3-5 minutes;

[0019] Add 0.02-0.03% (by total mass) of azodicyanate to solution A, and react to obtain a solid polymer thickener.

[0020] The polymer thickener solid is dehydrated, dried, and pulverized to obtain polymer thickener powder.

[0021] According to an embodiment of the present invention, the addition of 0.02-0.03% by total mass of azodicyanate to solution A to obtain a polymer thickener solid comprises:

[0022] Add 0.02-0.03% (by total mass) of azodicyano acid to solution A;

[0023] Introduce nitrogen gas, raise the pressure in the reactor to 0.5-1 MPa, then stop introducing nitrogen gas and react for 20-30 minutes.

[0024] Increase the reaction temperature to 80-90℃ and continue the reaction until the system pressure remains stable for 30 minutes without decreasing.

[0025] After the reaction is carried out under reduced pressure for 20-30 minutes, nitrogen gas is continuously introduced into the reaction vessel until the product cools to room temperature, and the reaction yields a solid polymer thickener.

[0026] As can be seen from the above technical solutions, the fracturing fluid and its preparation method provided by the present invention have the following beneficial effects:

[0027] This invention provides a fracturing fluid system, which is a polymer fracturing fluid system with good temperature resistance. The five-component polymer thickener provided by this invention has good compatibility with the wash oil agent. The fracturing fluid system has advantages such as dialysis displacement and forced wash oil. Under the premise of ensuring the temperature resistance and sand carrying capacity of the fracturing fluid, it achieves the goals of high sand carrying capacity, low filtration loss, low interfacial tension, high oil displacement effect and flowback rate, thereby improving the fracturing production increase effect. It plays an important role in promoting new high-efficiency fracturing fluid systems and increasing production efficiency. Attached Figure Description

[0028] Figure 1 This is a rheological curve diagram of Embodiment 1 of the present invention;

[0029] Figure 2 This is a static suspended sand diagram of Embodiment 1 of the present invention;

[0030] Figure 3 This is a rheological curve diagram of Embodiment 2 of the present invention;

[0031] Figure 4 This is a static suspended sand diagram of Embodiment 2 of the present invention;

[0032] Figure 5 This is a rheological curve diagram of Embodiment 3 of the present invention;

[0033] Figure 6 This is a static suspended sand diagram of Embodiment 3 of the present invention;

[0034] Figure 7 This is a rheological curve diagram of Embodiment 4 of the present invention;

[0035] Figure 8 This is a static suspended sand diagram of Embodiment 4 of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0037] In a first aspect, the present invention provides a fracturing fluid comprising, by mass fraction percentage: 1.0-1.2% polymer thickener, 0.3-0.5% oil displacement agent, 0.02-0.05% breaker, 0.5-1.0% anti-swelling agent, and the remainder being water;

[0038] The polymer thickener is a five-component polymer, and the reactive monomers of the polymer thickener include: acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid.

[0039] According to embodiments of the present invention, the polymer thickener comprises, by weight percentage, the following components: 20-25% acrylamide, 5-10% methyl acrylate, 8-10% 2-acrylamido-2-methylpropanesulfonic acid, 5-8% divinyl ammonium chloride, 2-5% ethyl acrylic acid, and the remainder being water; and

[0040] The total mass percentage of the reactant monomers is 0.02-0.03% azodicyano acid.

[0041] According to an embodiment of the present invention, the mass ratio of acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid in the reactive monomers of the polymer thickener is 1-1.25: 0.25-0.5: 0.4-0.5: 0.25-0.4: 0.1-0.25.

[0042] According to embodiments of the present invention, the anti-swelling agent is one or a mixture of quaternary ammonium salt and polyoxyethylene amine in any proportion.

[0043] According to an embodiment of the present invention, the degreasing agent is one of ammonium persulfate, potassium persulfate, sodium persulfate, or a mixture of two of them in any proportion.

[0044] According to embodiments of the present invention, the oil displacement agent is one or a mixture of alkoxysulfonate, alkoxysulfate salt, and alkoxycarboxylate salt in any proportion.

[0045] A second aspect of the present invention provides a method for preparing the above-mentioned fracturing fluid, comprising the following steps:

[0046] While stirring, the polymer thickener powder, oil displacement agent, degumming agent, and anti-swelling agent are added to the water in the following mass ratios, stirring continuously until the reagents are dissolved to obtain a semi-finished product.

[0047] The pH value of the semi-finished product is adjusted to 6-8 using a pH adjuster to obtain fracturing fluid.

[0048] According to an embodiment of the present invention, the pH adjuster is a sodium bicarbonate buffer system.

[0049] According to an embodiment of the present invention, the polymer thickener powder is prepared by the following steps:

[0050] Solution A is prepared by dissolving the reactants acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl ammonium chloride, and ethyl acrylic acid in water.

[0051] Add solution A to the reaction vessel, set the reaction temperature to 20-30℃, and purge with nitrogen gas for 3-5 minutes;

[0052] Add 0.02-0.03% (by total mass) of azodicyanate to solution A to obtain a solid polymer thickener.

[0053] The polymer thickener solid is dehydrated, dried, and pulverized to obtain polymer thickener powder.

[0054] According to an embodiment of the present invention, 0.02-0.03% by mass of azodicyanate is added to solution A, and the reaction yields a polymer thickener solid, comprising:

[0055] Add 0.02-0.03% (by total mass) of azodicyano acid to solution A;

[0056] Introduce nitrogen gas, raise the pressure in the reactor to 0.5-1 MPa, then stop introducing nitrogen gas and react for 20-30 minutes.

[0057] Increase the reaction temperature to 80-90℃ and continue the reaction until the system pressure remains stable for 30 minutes without decreasing.

[0058] After the reaction is carried out under reduced pressure for 20-30 minutes, nitrogen gas is continuously introduced into the reaction vessel until the product cools to room temperature, and the reaction yields a solid polymer thickener.

[0059] The technical solution of the present invention will be described in detail below through preferred embodiments. It should be noted that the specific embodiments in the following text are for illustrative purposes only and are not intended to limit the present invention.

[0060] Example 1

[0061] Preparation of polymer thickener: 23% acrylamide, 8% methyl acrylate, 9% 2-acrylamide-2-methylpropanesulfonic acid, 6% divinyl ammonium chloride, 3% ethyl acrylic acid, 0.02% azodicyanate by mass of total monomers, and the remainder is water.

[0062] Weigh out 23% acrylamide, 8% methyl acrylate, 9% 2-acrylamide-2-methylpropanesulfonic acid, 6% divinyl ammonium chloride, and 3% ethyl acrylic acid, dissolve them in water to obtain solution A, and record the total mass of the reactants as m1;

[0063] Solution A was added to the reactor, the reaction temperature was set to 25℃, nitrogen gas was purged for 5 minutes, and 0.02% azodicyanate (i.e., 0.02% ml azodicyanate) was added according to the total mass of the monomers. Nitrogen gas was continued to be purged, the reactor pressure was increased to 0.5 MPa, the nitrogen gas was stopped, the reaction was allowed to proceed for 25 minutes, the reaction temperature was increased to 85℃, the reaction was continued until the system pressure remained unchanged for 30 minutes, the reaction was allowed to proceed under reduced pressure for 25 minutes, and then nitrogen gas was continuously purged into the reaction vessel until the product cooled to room temperature, thus obtaining a solid polymer thickener.

[0064] Fracturing fluid preparation: Prepare the solution according to the following mass percentages: add 1.0% of the above-prepared polymer thickener, 0.5% sodium alkoxysulfonate, and 0.7% polyoxyethylene amine sequentially to water while stirring until the reagents are completely dissolved. Adjust the pH to 7 to obtain a multi-functional fracturing fluid system with an 80% washout rate and a temperature resistance of 130℃. Figure 1 As shown, at a temperature of 130℃, for 170 seconds... -1 Under shearing conditions for 60 minutes, the viscosity of the system after shearing was 75 mPa·s, which is greater than 50 mPa·s, indicating good temperature resistance. Figure 2 As shown, with an experimental sand ratio of 25% and 20 / 40 mesh ceramsite selected, no sand shedding occurred after standing for 10 minutes, indicating good static sand-carrying capacity of the fracturing fluid. This fracturing fluid system exhibits good sand-carrying capacity, temperature and shear resistance, and excellent oil-washing function.

[0065] Example 2

[0066] Preparation of polymer thickener: The reactants were selected with a mass fraction of 25% acrylamide, 9% methyl acrylate, 10% 2-acrylamide-2-methylpropanesulfonic acid, 7% divinyl ammonium chloride, 5% ethyl acrylic acid, 0.03% azodicyano acid (by mass of total monomers), and the remainder being water.

[0067] Weigh out 25% acrylamide, 9% methyl acrylate, 10% 2-acrylamide-2-methylpropanesulfonic acid, 7% divinyl ammonium chloride, and 5% ethyl acrylic acid, and dissolve them in water to obtain solution A;

[0068] Solution A was added to the reactor, the reaction temperature was set to 25°C, nitrogen gas was purged for 5 minutes, azodicyanate (0.03% of the total mass of the monomers) was added, nitrogen gas was continued to be purged, the reactor pressure was increased to 1 MPa, the nitrogen gas was stopped, the reaction was allowed to proceed for 30 minutes, the reaction temperature was increased to 90°C, the reaction was allowed to continue until the system pressure remained unchanged for 30 minutes, the reaction was allowed to proceed under reduced pressure for 30 minutes, and then nitrogen gas was continuously purged into the reaction vessel until the product cooled to room temperature, thus obtaining a solid polymer thickener.

[0069] Fracturing fluid preparation: Prepare the solution according to the following mass percentages: add 1.1% of the above-prepared polymer thickener, 0.4% sodium alkoxysulfonate, and 0.6% polyoxyethylene amine sequentially to water while stirring until the reagents are completely dissolved. Adjust the pH to 7 to obtain a multi-functional fracturing fluid system with a washout rate of 78% and a temperature resistance of 160℃. Figure 3 As shown, at a temperature of 160℃, for 170 seconds... -1 Under shearing conditions for 60 minutes, the viscosity of the system after shearing was 53 mPa·s, which is greater than 50 mPa·s, indicating good temperature resistance. Figure 4 As shown, with an experimental sand ratio of 25% and 20 / 40 mesh ceramsite selected, no sand shedding occurred after standing for 10 minutes, indicating good static sand-carrying capacity of the fracturing fluid. This fracturing fluid system exhibits good sand-carrying capacity, temperature and shear resistance, and excellent oil-washing function.

[0070] Example 3

[0071] Preparation of polymer thickener: 21% acrylamide, 6% methyl acrylate, 8% 2-acrylamide-2-methylpropanesulfonic acid, 5% divinyl ammonium chloride, 2% ethyl acrylic acid, 0.03% azodicyanate by mass of total monomers, and the remainder is water.

[0072] Weigh out 213% acrylamide, 6% methyl acrylate, 8% 2-acrylamide-2-methylpropanesulfonic acid, 5% divinyl ammonium chloride, and 2% ethyl acrylic acid, dissolve them in water to obtain solution A, and denote the total mass of the reactants as m1;

[0073] Solution A was added to the reactor, the reaction temperature was set to 20℃, nitrogen gas was purged for 5 min, and 0.03% azodicyanate (i.e., 0.03% ml azodicyanate) of the total mass of the monomers was added. Nitrogen gas was continued to be purged, the reactor pressure was increased to 0.7 MPa, the nitrogen gas was stopped, the reaction was allowed to proceed for 27 min, the reaction temperature was increased to 87℃, the reaction was continued until the system pressure remained unchanged for 30 min, the reaction was allowed to proceed under reduced pressure for 28 min, and then nitrogen gas was continuously purged into the reaction vessel until the product cooled to room temperature, thus obtaining a solid polymer thickener.

[0074] Fracturing fluid preparation: Prepare the solution according to the following mass percentages: add 1.2% of the above-prepared polymer thickener, 0.5% sodium alkoxysulfonate, and 0.8% polyoxyethylene amine sequentially to water while stirring until the reagents are completely dissolved. Adjust the pH to 7 to obtain a multi-functional fracturing fluid system with an oil washout rate of 81% and a temperature resistance of 130℃. Figure 5 As shown, at a temperature of 130℃, for 170 seconds... -1 Under shearing conditions for 60 minutes, the viscosity of the system after shearing was 81 mPa·s, which is greater than 50 mPa·s, indicating good temperature resistance. Figure 6 As shown, with an experimental sand ratio of 25% and 20 / 40 mesh ceramsite selected, no sand shedding occurred after standing for 10 minutes, indicating good static sand-carrying capacity of the fracturing fluid. This fracturing fluid system exhibits good sand-carrying capacity, temperature and shear resistance, and excellent oil-washing function.

[0075] Example 4

[0076] Preparation of polymer thickener: The reactants selected were 24% acrylamide, 5% methyl acrylate, 8% 2-acrylamide-2-methylpropanesulfonic acid, 5% divinyl ammonium chloride, 2% ethyl acrylic acid, 0.025% azodicyano acid (by mass of total monomers), and the remainder was water.

[0077] Weigh out 24% acrylamide, 5% methyl acrylate, 8% 2-acrylamide-2-methylpropanesulfonic acid, 5% divinyl ammonium chloride, and 2% ethyl acrylic acid, and dissolve them in water to obtain solution A;

[0078] Solution A was added to the reactor, the reaction temperature was set to 30℃, nitrogen gas was purged for 3 minutes, azodicyanate was added at a mass of 0.025% of the total monomers, nitrogen gas was continued to be purged, the reactor pressure was increased to 0.9 MPa, the nitrogen gas was stopped, the reaction was allowed to proceed for 20 minutes, the reaction temperature was increased to 85℃, the reaction was allowed to continue until the system pressure remained unchanged for 30 minutes, the reaction was allowed to proceed under reduced pressure for 20 minutes, and then nitrogen gas was continuously purged into the reaction vessel until the product cooled to room temperature, thus obtaining a solid polymer thickener.

[0079] Fracturing fluid preparation: Prepare the solution according to the following mass percentages: add 1.0% of the above-prepared polymer thickener, 0.3% sodium alkoxysulfonate, and 0.8% polyoxyethylene amine sequentially to water while stirring until the reagents are completely dissolved. Adjust the pH to 7 to obtain a multi-functional fracturing fluid system with a washout rate of 77% and a temperature resistance of 110℃. Figure 7 As shown, at a temperature of 110℃, for 170 seconds... -1 Under shearing conditions for 60 minutes, the viscosity of the system after shearing was 117 mPa·s, which is greater than 50 mPa·s, indicating good temperature resistance. Figure 8As shown, with an experimental sand ratio of 25% and 20 / 40 mesh ceramsite selected, no sand shedding occurred after standing for 10 minutes, indicating good static sand-carrying capacity of the fracturing fluid. This fracturing fluid system exhibits good sand-carrying capacity, temperature and shear resistance, and excellent oil-washing function.

[0080] Comparative Example 1

[0081] The common polymer fracturing fluid system 1 is a common polyacrylamide polymer fracturing fluid system (ALCH-5).

[0082] Comparative Example 2

[0083] The conventional polymer fracturing fluid system 2 is a conventional polyacrylamide polymer fracturing fluid system (ALCH-6).

[0084] Experimental Example 1

[0085] The fracturing fluids prepared in Comparative Example 1 and Examples 1, 3, and 4 were compared, and the results are shown in Table 1.

[0086] Table 1 Comparison of Fracturing Fluid Performance

[0087]

[0088]

[0089] Table 1 compares the performance of the conventional polymer fracturing fluid system 1 in Comparative Example 1 and the fracturing fluid system prepared by the present invention. The fracturing fluid system provided by the present invention has better anti-swelling performance, drag reduction performance and oil washing performance than the conventional fracturing system, meets the technical requirements of water turbine fracturing fluid, and has a much higher compatibility with oil displacement agent than the conventional polymer fracturing fluid system, with a viscosity retention rate of more than 90%.

[0090] Experimental Example 2

[0091] The fracturing fluids prepared in Comparative Example 2 and Example 2 were compared, and the results are shown in Table 2.

[0092] Table 2 Comparison of Fracturing Fluid Performance

[0093]

[0094] In Comparative Example 2, the performance comparison between the ordinary polymer fracturing fluid system 2 and the fracturing fluid system prepared by the present invention is shown in Table 2. The fracturing fluid system provided by the present invention has better anti-swelling performance, drag reduction performance, and oil washing performance than the conventional fracturing system. It has good temperature resistance, meets the technical requirements of water turbine fracturing fluid, and has a much higher compatibility with oil displacement agent than the ordinary polymer fracturing fluid system. The viscosity retention rate is greater than 90%.

[0095] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fracturing fluid, characterized by, According to the percentage of mass fraction, it comprises: polymer thickening agent 1.0-1.2%, oil displacement agent 0.3-0.5%, gel breaker 0.02-0.05%, anti-swelling agent 0.5-1.0%, and the rest is water; The polymer thickening agent is a five-membered polymer, and the reaction monomers of the polymer thickening agent comprise: acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl chloride ammonium and ethyl acrylic acid.

2. The fracturing fluid of claim 1, wherein, The polymer thickening agent comprises the following components according to the percentage of mass: acrylamide 20-25%, methyl acrylate 5-10%, 2-acrylamide-2-methylpropanesulfonic acid 8-10%, divinyl chloride ammonium 5-8%, ethyl acrylic acid 2-5%, and the rest is water; and the total mass percentage of reaction monomers is 0.02-0.03% of azodicarbonic acid.

3. The fracturing fluid of claim 1, wherein, The mass ratio of acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl chloride ammonium, and ethyl acrylic acid in the reaction monomers of the polymer thickening agent is 1-1.25:0.25-0.5:0.4-0.5:0.25-0.4:0.1-0.

25.

4. The fracturing fluid of claim 1, wherein, The anti-swelling agent is one or any proportion mixture of quaternary ammonium salt and polyoxyalkylene amine.

5. The fracturing fluid of claim 1, wherein, The gel breaker is one or a mixture of any proportion of ammonium persulfate, potassium persulfate and sodium persulfate.

6. The fracturing fluid of claim 1, wherein, The oil displacement agent is one or any proportion mixture of alkoxy sulfonate, alkoxy sulfate and alkoxy carboxylate.

7. A method of preparing the fracturing fluid according to any one of claims 1 to 6, characterized in that, It comprises the following steps: Under stirring, the polymer thickening agent powder, oil displacement agent, gel breaker and anti-swelling agent are sequentially added into water according to the mass ratio, and stirred until the reagents are dissolved to obtain a semi-finished product; The PH value of the semi-finished product is adjusted to 6-8 by using a PH regulator to obtain the fracturing fluid.

8. The method of claim 7, wherein, The PH regulator is a sodium bicarbonate buffer system.

9. The preparation method according to claim 7, characterized in that, The polymer thickening agent powder is prepared by the following steps: The reaction monomers acrylamide, methyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, divinyl chloride ammonium and ethyl acrylic acid are dissolved in water to obtain solution A; The solution A is added into a reaction kettle, and the reaction temperature is set to 20-30℃, and nitrogen is blown for 3-5min; 0.02-0.03% of azodicarbonic acid of the total mass of the reaction monomers is added into the solution A, and the polymer thickening agent solid is obtained by reaction. The polymer thickening agent solid is dehydrated, dried and crushed to obtain the polymer thickening agent powder.

10. The method of claim 9, wherein, The addition of 0.02-0.03% of azodicarbonic acid of the total mass of the reaction monomers into the solution A to obtain the polymer thickening agent solid comprises: 0.02-0.03% of azodicarbonic acid of the total mass of the reaction monomers is added into the solution A; Nitrogen is blown, the pressure of the reaction kettle is increased to 0.5-1MPa, then the nitrogen blowing is stopped, and the reaction is carried out for 20-30min; The reaction temperature is increased to 80-90℃, and the reaction is continued until the system pressure remains unchanged for 30min; After the reaction under reduced pressure for 20-30min, nitrogen is continuously blown into the reaction container until the product is cooled to room temperature, and the polymer thickening agent solid is obtained by reaction.

Images