A thickener for deep well fracturing and its preparation method and application

Abstract

The present invention provides a thickener for deep-well fracturing and a preparation method thereof. The invention employs an inverse emulsion polymerization method to prepare a thickener for deep-well fracturing by adding a water-soluble monomer to an emulsion stabilizer to form an aqueous phase and an emulsifier and a dispersant to form an oil phase. The thickener has a rapid dissolution rate and does not require pre-mixing, making it suitable for large-scale on-site fracturing. It also meets the requirements of high-well temperature, deep-well fracturing, and other construction requirements. This overcomes the drawback of conventional emulsion thickener fracturing fluid systems, which are inherently heat-resistant and require the use of crosslinking agents to enhance their heat resistance. This reduces product costs to a certain extent, and the on-site construction process is simple, meeting the requirements of large-scale continuous operations.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas extraction, and particularly relates to a thickener for deep well fracturing, a preparation method and an application thereof. Background Art

[0002] With the continuous advancement of exploration technology, deep well oil and gas resources are increasingly being discovered. As drilling continues to deepen and reservoir temperatures rise during exploration and development, higher requirements are being placed on existing polymer fracturing fluids. Polymer fracturing fluids experience a continuous decrease in viscosity at high temperatures, which in turn affects their sand-carrying and rheological properties. Poor sand-carrying capacity can easily lead to sand plugging and poor fracture creation, compromising fracturing effectiveness and reducing reservoir production. For some oil and gas resources with higher reservoir temperatures, existing polyacrylamide emulsion thickeners cannot meet the temperature resistance requirements. Powder-based thickeners, however, dissolve slowly and cannot meet the requirements for continuous mixing.

[0003] Therefore, researching a thickener for deep well fracturing is of great significance to the development of deep well oil and gas fields. Summary of the Invention

[0004] In order to solve the above problems in the prior art, the present invention provides a thickener for deep well fracturing, a preparation method thereof, and an application thereof.

[0005] In a first aspect, the present invention provides a thickener for deep well fracturing, which comprises a polymer having a structural formula as shown in Formula 1:

[0006]

[0007] Among them, o is 0.08-0.19 mol, p is 0.13-0.34 mol, and q is 0.01-0.04 mol.

[0008] As a specific embodiment of the present invention, the raw materials for its preparation include, by mass:

[0009]

[0010] As a specific embodiment of the present invention, the water-soluble monomer is a mixture of acrylamide (AM), acrylic acid (AA) and 2-acrylamido-2-phenylethanesulfonic acid in a mass ratio of (5-5.6):(3-3.3):(1.1-2).

[0011] As a specific embodiment of the present invention, the emulsion stabilizer is polyethylene glycol stearate, preferably at least one selected from PEG400MS, PEG400DS, and PEG6000DS.

[0012] As a specific embodiment of the present invention, the oxidizing agent is one of ammonium persulfate and potassium persulfate, and the reducing agent is one of sodium bisulfite and sodium metabisulfite. The oxidizing agent and reducing agent form a redox initiation system, that is, an initiator.

[0013] As a specific embodiment of the present invention, the dispersant is at least one of liquid paraffin, kerosene, 3# white oil, 5# white oil, and 7# white oil.

[0014] As a specific embodiment of the present invention, the emulsifier is optionally one of an HLB value less than 5 and an HLB value greater than 5, preferably mixed in a mass ratio of (2-5):1, more preferably, mixed in a mass ratio of 3:1. Generally, emulsifiers with an HLB value less than 5 include Span85, Span80, and Span60; emulsifiers with an HLB value greater than 5 include Tween80 and OP-10.

[0015] As a specific embodiment of the present invention, the phase inversion agent is at least one of the nonionic surfactants OP-10, TX-10, Tween80, Span80, and FC-4430.

[0016] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0017] In a second aspect, the present invention provides a method for preparing the thickener for deep well fracturing, comprising the following steps:

[0018] S1: mixing a water-soluble monomer, an emulsion stabilizer, an oxidant and water to obtain an aqueous phase mixture;

[0019] S2: mixing the emulsifier and the dispersant to obtain an oil phase mixture;

[0020] S3: mixing the aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 to obtain a water-in-oil pre-emulsion;

[0021] S4: adding a reducing agent to the water-in-oil emulsion obtained in step S3 to initiate a polymerization reaction, and adding a phase inversion agent after the polymerization reaction to obtain the thickener for deep well fracturing.

[0022] As a specific embodiment of the present invention, in step S1, the pH value of the aqueous phase mixture is 6-8, and the pH value is preferably adjusted to 6-8 with an aqueous sodium hydroxide solution;

[0023] As a specific embodiment of the present invention, in step S1 and step S2, the mixing method is preferably magnetic stirring, the stirring rate is 800 to 1200 r / min, and the stirring time is 5 to 20 min;

[0024] As a specific embodiment of the present invention, in step S3, the mixing method is high-speed stirring, the stirring rate is 8000-10000 r / min, and the stirring time is 5-10 min;

[0025] As a specific embodiment of the present invention, in step S4, the polymerization reaction conditions are a temperature of 35-45° C. and a reaction time of 4-5 h.

[0026] In a third aspect, the present invention provides application of the thickener for deep well fracturing in the field of fracturing fluid.

[0027] As a specific embodiment of the present invention, the mass fraction ratio of the thickener for deep well fracturing in water is 1%-3%.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The thickener for deep well fracturing of the present invention introduces polyethylene glycol stearate, an emulsion stabilizer, to improve the stability of the emulsion. The functional monomer 2-acrylamido-2-phenylethanesulfonic acid is used, and the two cooperate to produce a synergistic effect. This is because the addition of polyethylene glycol stearate introduces a physical network structure into the chemically cross-linked network structure of the reaction system, thereby improving the high-temperature resistance of the polymer emulsion as a thickener.

[0030] 2. The thickener for deep well fracturing of the present invention can be seen in the examples. At 160°C, 170s -1 After 1 hour of shearing, the final viscosity can reach 62.79mPa·s, which is 25.6% higher than the industry standard requirement of no less than 50mPa·s.

[0031] 3. The thickener for deep well fracturing of the present invention does not require the addition of any high-temperature cross-linking agent, which not only reduces the use cost but also simplifies the construction process and can meet the large-scale continuous fracturing construction requirements of deep wells and other reservoirs with high well temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a dissolution curve of the thickener prepared in Example 4 of the present invention;

[0033] Figure 2a This is a graph showing the 120°C heat and shear resistance curve of the thickener prepared in Example 4 of the present invention;

[0034] Figure 2b This is a graph showing the 160°C heat and shear resistance curve of the thickener prepared in Example 4 of the present invention;

[0035] Figure 3 This is a 120°C heat and shear resistance curve of the thickener of comparative sample 1 obtained in comparative example 1;

[0036] Figure 4 This is a 120°C heat and shear resistance curve of the thickener of comparative sample 2 obtained in comparative example 2. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0038] In each embodiment of the present invention, the specific information of the reagents used is as follows:

[0039] Acrylamide (AM), industrial grade, Shaanxi Changhai Oilfield Additives Co., Ltd.;

[0040] Acrylic acid (AA), industrial grade, Shaanxi Changhai Oilfield Additives Co., Ltd.;

[0041] 2-Acrylamido-2-phenylethanesulfonic acid, industrial grade, Shaanxi Changhai Oilfield Additives Co., Ltd.;

[0042] PEG400MS, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province;

[0043] PEG400DS, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province;

[0044] PEG6000DS, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province;

[0045] Ammonium persulfate, analytical grade, Tianjin Oubok Chemical Co., Ltd.;

[0046] Potassium persulfate, analytical grade, Tianjin Oubokai Chemical Co., Ltd.;

[0047] Sodium bisulfite, analytical grade, Tianjin Oubok Chemical Co., Ltd.;

[0048] Sodium metabisulfite, analytical grade, Tianjin Oubok Chemical Co., Ltd.;

[0049] Liquid paraffin, industrial grade, Shaanxi Runtai Chemical Co., Ltd.;

[0050] Kerosene, industrial grade, Shaanxi Runtai Chemical Co., Ltd.;

[0051] 3# white oil, industrial grade, Shaanxi Runtai Chemical Co., Ltd.;

[0052] 5# white oil, industrial grade, Shaanxi Runtai Chemical Co., Ltd.;

[0053] 7# white oil, industrial grade, Shaanxi Runtai Chemical Co., Ltd.;

[0054] Span85, industrial grade, Haian Petrochemical Plant, Jiangsu Province;

[0055] Span80, industrial grade, Haian Petrochemical Plant, Jiangsu Province;

[0056] Span60, industrial grade, Haian Petrochemical Plant, Jiangsu Province;

[0057] Tween80, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province;

[0058] OP-10, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province;

[0059] TX-10, industrial grade, Jinan Runhui Chemical Co., Ltd.;

[0060] FC-4430, industrial grade, Hai'an Petrochemical Plant, Jiangsu Province.

[0061] Example 1

[0062] This embodiment provides a thickener for deep well fracturing and a preparation method thereof, the specific details of which are as follows:

[0063] S1: Dissolve 6 parts by weight of acrylic acid, 10 parts by weight of acrylamide, and 4 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid in 30 parts of water under magnetic stirring. Dissolve 2 parts by weight of PEG400MS in 15 parts of water. Mix the two thoroughly, then add 1.5 parts by weight of ammonium persulfate. Adjust the pH to 6.5 with aqueous NaOH. After cooling to room temperature, an aqueous mixture is obtained.

[0064] S2: 2 parts by weight of a mixture of Span 85 and Tween 80 (wherein the mass ratio of Span 85 to Tween 80 is 3:1) and 25 parts by weight of kerosene are mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0065] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 8000 r / min for 5 minutes to obtain a water-in-oil pre-emulsion.

[0066] S4: Slowly add 1.5 parts by weight of sodium bisulfite to the water-in-oil pre-emulsion in a flask equipped with a stirred tank, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 45°C for 5 hours, add 3 parts by weight of a phase inversion agent OP-10 to obtain a thickener for deep well fracturing.

[0067] Example 2

[0068] This embodiment provides a thickener for deep well fracturing and a preparation method thereof, the specific details of which are as follows:

[0069] S1: 7.5 parts by weight of acrylic acid, 12.5 parts by weight of acrylamide, and 2.5 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid were dissolved in 30 parts by weight of water under magnetic stirring, and 2.5 parts by weight of PEG6000DS were dissolved in 12 parts by weight of water. After the two parts were mixed evenly, 1 part by weight of potassium persulfate was added, and the pH value was adjusted to 7.0 with a NaOH aqueous solution. After cooling to room temperature, an aqueous mixture was obtained.

[0070] S2: 3 parts by weight of a mixture of Span85 and OP-10 (wherein the mass ratio of Span85 to OP-10 is 3:1) and 25 parts by weight of 3# white oil were mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0071] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 10,000 rpm for 5 minutes to obtain a water-in-oil pre-emulsion.

[0072] S4: Slowly add 1 part by weight of sodium bisulfite to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirring kettle, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 35° C. for 4 hours, 3 parts by weight of a phase inversion agent FC-4430 are added to obtain a thickener for deep well fracturing.

[0073] Example 3

[0074] This embodiment provides a thickener for deep well fracturing and a preparation method thereof, the specific details of which are as follows:

[0075] S1: 9 parts by weight of acrylic acid, 15 parts by weight of acrylamide, and 3 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid were dissolved in 20 parts by weight of water under magnetic stirring. 1.5 parts by weight of PEG400MS and 1.5 parts of PEG400DS were dissolved in 13 parts by weight of water. The two were mixed and then 2 parts of ammonium persulfate were added. The pH value was then adjusted to 8 with an aqueous NaOH solution. After cooling to room temperature, an aqueous mixture was obtained.

[0076] S2: 4 parts by weight of a mixture of Span80 and OP-10 (wherein the mass ratio of Span80 to OP-10 is 3:1) and 27 parts by weight of 5# white oil are mixed uniformly under the action of magnetic stirring to obtain an oil phase for later use.

[0077] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 9000 r / min for 8 minutes to obtain a water-in-oil pre-emulsion.

[0078] S4: 1.5 parts by weight of sodium metabisulfite was slowly added to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirred tank, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 40° C. for 4.5 hours, 2.5 parts by weight of a phase inversion agent TX-10 was added to obtain a thickener for deep well fracturing.

[0079] Example 4

[0080] This embodiment provides a thickener for deep well fracturing and a preparation method thereof, the specific details of which are as follows:

[0081] S1: 10.5 parts by weight of acrylic acid, 17.5 parts by weight of acrylamide, and 3.5 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid were dissolved in 20 parts by weight of water under magnetic stirring. 2 parts by weight of PEG400DS and 1.5 parts by weight of PEG6000DS were dissolved in 10 parts by weight of water. The two were mixed and then 1 part by weight of potassium persulfate was added. The pH value was then adjusted to 6.5 with an aqueous NaOH solution. After cooling to room temperature, an aqueous mixture was obtained.

[0082] S2: 3 parts by weight of a mixture of Span 80 and Tween 80 (wherein the mass ratio of Span 80 to Tween 80 is 3:1) and 27 parts of 7# white oil are mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0083] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 10,000 r / min for 10 minutes to obtain a water-in-oil pre-emulsion.

[0084] S4: Slowly add 1 part by weight of sodium metabisulfite to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirred tank, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 45° C. for 5 hours, 3 parts by weight of a phase inversion agent OP-10 are added to obtain a thickener for deep well fracturing.

[0085] Example 5

[0086] This embodiment provides a thickener for deep well fracturing and a preparation method thereof, the specific details of which are as follows:

[0087] S1: 12 parts by weight of acrylic acid, 20 parts by weight of acrylamide, and 4 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid were dissolved in 20 parts by weight of water under magnetic stirring, and 4 parts by weight of PEG6000DS were dissolved in 12 parts by weight of water. After the aqueous phase was mixed uniformly, 2 parts by weight of ammonium persulfate was added, and the pH value was adjusted to 8.0 with a NaOH aqueous solution. After cooling to room temperature, an aqueous phase mixture was obtained.

[0088] S2: 2 parts by weight of a mixture of Span 60 and Tween 80 (wherein the mass ratio of Span 60 to Tween 80 is 3:1) and 20 parts by weight of 5# white oil are mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0089] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 8000 r / min for 6 minutes to obtain a water-in-oil pre-emulsion.

[0090] S4: Slowly add 1 part by weight of sodium metabisulfite to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirred tank, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 35° C. for 4 hours, 3 parts by weight of a mixture of phase inversion agents OP-10 and TX-10 (mass ratio of 1:1) are added to obtain a thickener for deep well fracturing.

[0091] Comparative Example 1

[0092] S1: 10.5 parts by weight of acrylic acid, 17.5 parts by weight of acrylamide, and 3.5 parts by weight of 2-acrylamido-2-phenylethanesulfonic acid were dissolved in 30 parts by weight of water under magnetic stirring, 1 part by weight of potassium persulfate was added, and the pH value was adjusted to 6.5 with an aqueous NaOH solution. After cooling to room temperature, an aqueous phase mixture was obtained.

[0093] S2: 3 parts by weight of a mixture of Span 80 and Tween 80 (wherein the mass ratio of Span 80 to Tween 80 is 3:1) and 27 parts by weight of 7# white oil are mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0094] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 10,000 r / min for 10 minutes to obtain a water-in-oil pre-emulsion.

[0095] S4: 1 part by weight of sodium metabisulfite was slowly added to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirred tank, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 45° C. for 5 h, 3 parts by weight of a phase inversion agent OP-10 was added to obtain comparative sample 1.

[0096] Comparative Example 2

[0097] S1: 10.5 parts by weight of acrylic acid and 17.5 parts by weight of acrylamide were dissolved in 20 parts by weight of water under magnetic stirring, and 2 parts by weight of PEG400DS and 1.5 parts by weight of PEG6000DS were dissolved in 10 parts of water. The two were mixed and then 1 part by weight of potassium persulfate was added. The pH value was then adjusted to 6.5 with an aqueous NaOH solution. After cooling to room temperature, an aqueous mixture was obtained.

[0098] S2: 3 parts by weight of Span80-Tween80 (mass ratio 3:1) and 27 parts by weight of 7# white oil were mixed uniformly under the action of magnetic stirring to obtain an oil phase mixture.

[0099] S3: The aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 are mixed, and stirred at a high speed of 10,000 r / min for 10 minutes to obtain a water-in-oil pre-emulsion.

[0100] S4: 1 part by weight of sodium metabisulfite was slowly added to the water-in-oil pre-emulsion obtained in step S3 in a flask equipped with a stirring kettle, a thermometer, and a nitrogen inlet to initiate a polymerization reaction. After reacting at 45° C. for 5 h, 3 parts by weight of a phase inversion agent OP-10 was added to prepare comparative sample 2.

[0101] Test Example 1

[0102] Gel breaking performance test

[0103] The prepared 1 wt% emulsion of the thickener for deep well fracturing was broken with 0.05% ammonium persulfate at 90° C. for 2 h to study the gel breaking performance of the thickener for deep well fracturing.

[0104] After the fracturing fluid thickener was broken with 0.05% ammonium persulfate at 90°C for 2 hours, its gel breaking performance met the technical requirements according to SY / T6376-2008 General Technical Conditions for Fracturing Fluids, as shown in Table 1:

[0105] Table 1 Test results of gel breaking performance of thickener for deep well fracturing

[0106]

[0107] Among the above-mentioned embodiments 1 to 5, embodiment 4 is the best implementation case.

[0108] Test Example 2

[0109] Solubility test

[0110] The thickener for deep well fracturing prepared in Example 4 was prepared into a 1 wt% aqueous solution, and the apparent viscosity of the solution was measured every 10 seconds using a six-speed viscometer to obtain a time-viscosity curve of its dissolution.

[0111] The thickener has a fast dissolution speed and good thickening performance. When the dissolution time is 30s, its apparent viscosity can reach 150mPa·s and the viscosity release rate can reach 95%. Figure 1 As shown, it can meet the continuous mixing requirements of the construction site.

[0112] Test Example 3

[0113] Heat and shear resistance test

[0114] The 1 wt% aqueous solution of the thickener for deep well fracturing prepared in Example 4 was subjected to shear resistance tests using a HAAKE MARS rheometer under different high temperature conditions. The shear rate was 170 s-1 and the shearing time was 1 hour to study the temperature and shear resistance of the thickener for deep well fracturing.

[0115] The fracturing fluid was heated at 120℃ for 170s -1 After 1 hour of shearing, the final viscosity is 85.83mPa·s, 160℃, 170s -1 After 1 hour of shearing, the final viscosity is 62.79 mPa·s. Figure 2a and Figure 2b As shown, they can meet the industry's requirement of no less than 50mPa·s.

[0116] The same method was used to test the heat and shear resistance of comparative sample 1 and comparative sample 2 at 120℃. -1 ,After 1 hour of shearing, the final viscosity is 41mPa·s, which is lower than the industry index, such as Figure 3 As shown. Comparative sample 2 at 120℃, 170s -1 ,After 1 hour of shearing, the final viscosity is 32mPa·s, which is lower than the industry index, such as Figure 4 shown.

[0117] In summary, the thickener for deep well fracturing of the present invention introduces the emulsion stabilizer polyethylene glycol stearate to improve the stability of the emulsion, and adopts the functional monomer 2-acrylamido-2-phenylethanesulfonic acid, and the two cooperate to produce a synergistic effect. This is because the addition of polyethylene glycol stearate introduces a physical network structure into the chemically cross-linked network structure of the reaction system, thereby improving the high temperature resistance of the polymer emulsion as a thickener. At 150°C, after shearing for 1 hour at 170s-1, the final viscosity can reach 62.79mPa·s, which is 25.6% higher than the industry standard requirement of not less than 50mPa·s, and no high-temperature cross-linking agent needs to be added, which not only reduces the cost of use, but also simplifies the construction process and can meet the large-scale continuous fracturing construction requirements of reservoirs with higher well temperatures such as deep wells.

[0118] Any numerical value mentioned in the present invention includes all values ​​that increase by one unit each time from the lowest value to the highest value if there is only a gap of two units between any minimum value and any maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is stated to be 50-90, it is meant in this specification to specifically list values ​​such as 51-89, 52-88... and 69-71 and 70-71. For non-integer values, it is appropriate to consider units of 0.1, 0.01, 0.001 or 0.0001. These are just some special examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed lowest value and the listed highest value are considered to have been disclosed.

[0119] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A thickener for deep well fracturing, characterized in that: Based on 100 parts by mass, the raw materials for its preparation include: The water-soluble monomer is a mixture of acrylamide (AM), acrylic acid (AA) and 2-acrylamido-2-phenylethanesulfonic acid in a mass ratio of (5-5.6): (3-3.3): (1.1-2); The emulsion stabilizer is polyethylene glycol stearate.

2. The thickener for deep well fracturing according to claim 1, characterized in that: The emulsion stabilizer is selected from at least one of PEG400MS, PEG400DS, and PEG6000DS.

3. The thickener for deep well fracturing according to claim 1, characterized in that: The oxidizing agent is one of ammonium persulfate and potassium persulfate, and the reducing agent is one of sodium bisulfite and sodium metabisulfite.

4. The thickener for deep well fracturing according to any one of claims 1 to 3, characterized in that: The dispersant is at least one of liquid paraffin, kerosene, 3# white oil, 5# white oil, and 7# white oil; and / or, The emulsifier is a mixture of an emulsifier having an HLB value of less than 5 and an emulsifier having an HLB value of greater than 5; and / or, The phase inversion agent is at least one of the nonionic surfactants OP-10, TX-10, Tween80, Span80, and FC-4430.

5. The thickener for deep well fracturing according to claim 4, characterized in that: The mass ratio of emulsifier with HLB value less than 5 and emulsifier with HLB value greater than 5 is (2~5):

1.

6. The thickener for deep well fracturing according to claim 5, characterized in that: The mass ratio of the emulsifier with an HLB value less than 5 to the emulsifier with an HLB value greater than 5 is 3:

1.

7. A method for preparing a thickener for deep well fracturing according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: mixing a water-soluble monomer, an emulsion stabilizer, an oxidant and water to obtain an aqueous phase mixture; S2: mixing the emulsifier and the dispersant to obtain an oil phase mixture; S3: mixing the aqueous phase mixture obtained in step S1 and the oil phase mixture obtained in step S2 to obtain a water-in-oil pre-emulsion; S4: adding a reducing agent to the water-in-oil pre-emulsion obtained in step S3 to initiate a polymerization reaction, and adding a phase inversion agent after the polymerization reaction to obtain the thickener for deep well fracturing; Wherein, the water-soluble monomers are acrylamide (AM), acrylic acid (AA) and 2-acrylamido-2-phenylethanesulfonic acid.

8. The preparation method according to claim 7, characterized in that In step S1, the pH value of the aqueous phase mixture is 6-8; And / or, in step S1 and step S2, the mixing method is independently magnetic stirring.

9. The preparation method according to claim 8, characterized in that Adjust its pH value to 6-8 with sodium hydroxide aqueous solution; And / or, in step S1 and step S2, the stirring rate is 800-1200 r / min, and the stirring time is 5-20 min.

10. The preparation method according to any one of claims 7 to 9, characterized in that: In step S3, the mixing method is high-speed stirring, the stirring rate is 8000-10000 r / min, and the stirring time is 5-10 min; And / or, in step S4, the polymerization reaction conditions are a temperature of 35-45° C. and a reaction time of 4-5 h.

11. Use of the thickener for deep well fracturing according to any one of claims 1 to 6 or the thickener for deep well fracturing prepared by the preparation method according to any one of claims 7 to 10 in the field of fracturing fluids.

12. The use according to claim 11, characterized in that The mass fraction ratio of the thickener for deep well fracturing in water is 1%-3%.

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