Diazotization anaerobic gel breaker for removing polyacrylamide micelles in stratum and preparation method thereof

Abstract

The invention discloses a diazotization anaerobic gel breaker for removing polyacrylamide micelles in strata and a preparation method of the diazotization anaerobic gel breaker, and relates to the technical field of oil exploitation. The diazotization anaerobic gel breaker for removing the polyacrylamide micelles in the stratum comprises an intermediate I and a mature body I, the intermediate I is a mixed solution of phenylhydrazine, carbamide, distilled water, acetone cyanohydrin and concentrated sulfuric acid, and the mature body I is a mixed solution of the intermediate I, hydrobromic acid and hydrogen peroxide. In the invention, the obtained diazotized anaerobic gel breaker has a diazo structure, and the diazo structure starts to decompose free radicals and release nitrogen under an acidic condition. The released free radicals have an oxidation effect and can gradually dissolve polyacrylamide micelles from outside to inside, the released nitrogen can tear the micelles from the inside, and meanwhile, the release of the nitrogen can increase the internal pressure of a crack space, so that the emission of the cracked micelles is facilitated, and the method has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a diazotized oxygen-free gel breaker for removing formation polyacrylamide micelles and a preparation method thereof. Background Art

[0002] In oilfield fracturing operations, the widespread use of polyacrylamide fracturing fluids has brought significant production-increasing effects to improve oil and gas recovery. However, long-chain polyacrylamide molecules are very likely to form high-viscosity, high-strength micelles in the formation. The formation of such micelles mainly comes from the entanglement and gelation reaction between its molecules, which will be further enhanced in the high temperature and high pressure environment of the formation, resulting in serious blockage of formation pores or pipelines. The retention of micelles in the oilfield formation not only affects the fluidity of oil and gas, but also causes a decrease in reservoir permeability and even hinders subsequent production operations. Therefore, gel breaking technology has become an urgent problem to be solved in oilfield development.

[0003] The purpose of gel breaking is to eliminate the residue of fracturing fluid in the formation or pipeline and restore the permeability of the reservoir. At present, common gel breaking methods include the use of oxidants, enzyme degradation technology and physical replacement. Oxidants, such as hydrogen peroxide, persulfate, etc., break the long chain structure of polyacrylamide through oxidation, thereby reducing its molecular weight and viscosity. Hydrogen peroxide decomposes to produce oxygen under formation conditions, and the generation of free radicals will cause the breakage of polyacrylamide molecular chains. However, hydrogen peroxide decomposes rapidly under high temperature or unstable conditions, and the oxygen release rate is difficult to control, which can easily lead to explosion risks and pose a potential threat to the safety of oilfield field operations. In addition, oxidants may produce by-products in the formation, affecting the oilfield environment and increasing the complexity of subsequent treatment. Summary of the invention

[0004] The object of the present invention is to provide a diazotized oxygen-free gel breaker for removing formation polyacrylamide micelles and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] The present invention provides a diazotized oxygen-free gel breaker for removing formation polyacrylamide micelles, comprising an intermediate I and a mature body I, wherein the intermediate I is a mixed solution of phenylhydrazine, carbonamide, distilled water, acetone cyanohydrin and concentrated sulfuric acid.

[0007] The mature form I is a mixed solution of intermediate I, hydrobromic acid and hydrogen peroxide.

[0008] The present invention also provides a method for preparing a diazotized oxygen-free gel breaker for removing formation polyacrylamide micelles, comprising the following steps:

[0009] S1. First, add phenylhydrazine and carbonamide into distilled water and mix well. At temperature T1, react for time t1. Then, slowly add acetone cyanohydrin dropwise. At temperature T2, react for time t2. Then, lower the system temperature to T3. Finally, slowly add concentrated sulfuric acid for reaction time t3 to obtain intermediate I.

[0010] S2: slowly drop hydrobromic acid and hydrogen peroxide into the intermediate I in sequence, and control the reaction time at temperature T4 to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0011] As a preferred embodiment of the present invention, in S1, the mass ratio of phenylhydrazine, carbonic acid amide and distilled water is 1:(1-2):(10-20), the reaction temperature T1 is 80-115°C, and the reaction time t1 is 3-5h.

[0012] As a preferred embodiment of the present invention, in S1, the masses of acetone cyanohydrin and concentrated sulfuric acid are (1 to 1.2) times and (0.5 to 1.5) times that of phenylhydrazine, respectively, the reaction temperature T2 is 20 to 30° C., and the reaction time t2 is 4 to 6 hours.

[0013] As a preferred embodiment of the present invention, in S1, the reaction temperature T3 is 0 to 10°C, and the reaction time t3 is 2 to 3 hours.

[0014] As a preferred embodiment of the present invention, in S2, the masses of the hydrobromic acid and hydrogen peroxide are (0.02-0.05) times and (0.3-0.5) times that of phenylhydrazine; the reaction temperature T4 is 15-40°C, and the reaction time t4 is 2-4h.

[0015] As a preferred embodiment of the present invention, the application method of the diazotized oxygen-free breaker for removing polyacrylamide micelles in formations is to inject the breaker and the catalyst alternately into the slugs.

[0016] Wherein, the catalyst is a mixture of formic acid and fruit acid, the mixing mass ratio of the formic acid and the fruit acid is 1:1, and the mass ratio of the breaker and the catalyst is 1:1.2.

[0017] Compared with the prior art, the present invention proposes a new debonding method based on diazotization reaction, which utilizes diazotization reaction under acidic conditions to degrade the long chain of polyacrylamide, forming a dual effect of physical tearing and chemical degradation of micelles. Under acidic conditions, the diazotization reaction will generate free radicals, which act on the long chain of the polymer to trigger an oxidative degradation reaction, causing the long chain to break, thereby weakening its viscosity and reducing its residue in the formation. In addition, nitrogen will be released during the diazotization reaction. This harmless gas generates pressure inside the polyacrylamide micelle, which has the effect of tearing the micelle structure. Compared with the hydrogen peroxide debonding method that produces oxygen, nitrogen is more stable and safer, and is not easy to cause explosion risks. It is suitable for use under high temperature and high pressure formation conditions. This method not only has high safety, but also can effectively reduce the molecular weight of polyacrylamide, causing it to lose the ability to form micelles, restore the permeability of the formation, and reduce the complexity of subsequent operations. Through the dual mechanisms of free radical chain scission and nitrogen tearing of micelles, this diazotization degumming method is expected to become a new safe, environmentally friendly and efficient degumming method, providing an innovative solution to the problem of oilfield fracturing fluid blockage.

[0018] One or more of the above technical solutions have the following beneficial effects:

[0019] 1. First, phenylhydrazine, carbon amide and acetone cyanohydrin are reacted, and then concentrated sulfuric acid is used for hydrolysis, and then reacted with hydrobromic acid and hydrogen peroxide to obtain a diazonium salt breaker. Under acidic conditions, free radicals are generated and nitrogen is released. The dual degradation mechanism of free radical chain breaking and nitrogen tearing is used to efficiently destroy the micelle structure. First, the generation of free radicals directly acts on the long-chain structure of polyacrylamide, and the long chain is broken through the oxidation reaction, thereby reducing its molecular weight, significantly reducing the viscosity of the micelle, and gradually losing its ability to form micelles; secondly, the nitrogen generated during the diazotization reaction forms tiny bubbles inside the micelle, generating physical pressure to tear the micelle network and further destroy its structure. In contrast, nitrogen is a non-toxic, non-explosive inert gas that is not only stable, but also does not produce byproducts that are harmful to the environment during the degradation process, thereby ensuring the environmental friendliness of the entire breaking process. The dual degradation mechanism solves the safety and adaptability problems of traditional oxidant and enzyme degradation methods, and is suitable for complex formation environments with high temperature and high pressure in oil fields;

[0020] 2. It avoids the release of oxygen by traditional oxidants such as hydrogen peroxide in high-temperature formations. Oxygen is difficult to control under high-pressure conditions, which may cause the risk of explosion, thus achieving a higher degumming efficiency and greatly reducing operational safety issues. The dual effects of free radicals and nitrogen produced by diazotization can not only quickly and effectively degummed, but also avoid the generation of explosive oxygen, and is suitable for use under harsh conditions in oil fields. This technology provides a safe, economical, and environmentally friendly innovative solution to the problem of blockage of oil field fracturing fluids, which not only ensures the safety of oil field operations, but also provides technical support for the future sustainable development of oil fields. In addition, the degumming agent provided by the present invention solves the problems of on-site liquid preparation and cumbersome construction, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 is the general structural formula of the breaker in the diazotization anaerobic breaking method for formation polyacrylamide micelles of the present invention;

[0023] Figure 2 It is a diagram of the micelle destruction process in the diazotization anaerobic gel breaking method for formation polyacrylamide micelles of the present invention;

[0024] Figure 3 The infrared spectrum of the diazotized oxygen-free breaker for formation polyacrylamide micelles of the present invention;

[0025] Figure 4 This is a graph showing the performance test results of the gel breaker prepared in Example 3 of the present invention;

[0026] Figure 5 This is a graph showing the performance test results of the gel breaker prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0029] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0030] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0031] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0034] See also Figure 1-5 The present invention discloses a preparation method of a diazotized anaerobic breaker for removing formation polyacrylamide micelles, including a diazotized anaerobic breaker for removing formation polyacrylamide micelles and a preparation method thereof, comprising the following steps:

[0035] S1: Add phenylhydrazine and carbonamide into distilled water and mix evenly. React at 80-115°C for 3-5 hours. Then slowly add acetone cyanohydrin dropwise. React at 20-30°C for 4-6 hours. Then lower the system temperature to 0-10°C. Finally, slowly add concentrated sulfuric acid. React for 2-3 hours to obtain intermediate I.

[0036] S2: slowly drop hydrobromic acid and hydrogen peroxide into the intermediate I in sequence, and control the reaction time at a temperature of 15 to 40° C. for 2 to 4 hours to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0037] As an optional solution, in step S1, the mass ratio of phenylhydrazine, carbonic acid amide and distilled water is 1:(1-2):(10-20);

[0038] As an optional solution, in step S1, the mass of acetone cyanohydrin and concentrated sulfuric acid is (1 to 1.2) times and (0.5 to 1.5) times that of phenylhydrazine;

[0039] As an optional solution, in step S2, the mass of hydrobromic acid and hydrogen peroxide is (0.02-0.05) times and (0.3-0.5) times that of phenylhydrazine;

[0040] Example 1

[0041] S1: Add 10 g of phenylhydrazine and 15 g of carbonamide into 150 g of distilled water and mix well. Incubate at 90 °C for 4 h, then slowly drop 5 g of acetone cyanohydrin. After 5 h of reaction at 25 °C, lower the system temperature to 5 °C, and finally slowly add 5 g of concentrated sulfuric acid. The reaction time is 2.5 h to obtain intermediate I.

[0042] S2: Slowly drop 0.3 g of hydrobromic acid and 4 g of hydrogen peroxide into the intermediate I in sequence, and control the reaction time at 30°C to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0043] Example 2

[0044] S1: Add 9.8 g of phenylhydrazine and 13.5 g of carbonamide into 140 g of distilled water and mix well. Incubate the mixture at 80 °C for 3.5 h. Then slowly add 4.8 g of acetone cyanohydrin. Incubate the mixture at 20 °C for 5.5 h. Then lower the system temperature to 7 °C. Finally, slowly add 6 g of concentrated sulfuric acid. Incubate the mixture for 2 h to obtain intermediate I.

[0045] S2: Slowly drop 0.4 g of hydrobromic acid and 3.5 g of hydrogen peroxide into the intermediate I in sequence, and control the reaction time at 25°C for 3 hours to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0046] Example 3

[0047] S1: Add 10.5 g of phenylhydrazine and 16 g of carbonamide into 160 g of distilled water and mix well. React at 95 °C for 4 h. Then slowly add 5.2 g of acetone cyanohydrin. After reacting at 28 °C for 4 h, lower the system temperature to 3 °C. Finally, slowly add 5.5 g of concentrated sulfuric acid. React for 3 h to obtain intermediate I.

[0048] S2: Slowly drop 0.2 g of hydrobromic acid and 4 g of hydrogen peroxide into the intermediate I in sequence, control the reaction time at 35°C for 2.5 h, and finally obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles after cooling, washing and drying.

[0049] Example 4

[0050] S1: Add 9.6 g of phenylhydrazine and 18 g of carbonamide into 175 g of distilled water and mix well. Incubate the mixture at 115 °C for 4.5 h. Then slowly add 4.5 g of acetone cyanohydrin. After 6 h of reaction at 30 °C, lower the system temperature to 0 °C. Finally, slowly add 5 g of concentrated sulfuric acid. The reaction time is 2.5 h to obtain intermediate I.

[0051] S2: Slowly drop 0.3 g of hydrobromic acid and 3.8 g of hydrogen peroxide into the intermediate I in sequence, and control the reaction time at 25°C for 3 hours to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0052] Example 5

[0053] S1: Add 10.2 g of phenylhydrazine and 14 g of carbonamide to 155 g of distilled water and mix well. Incubate the mixture at 100 °C for 3 h. Then slowly drop 5 g of acetone cyanohydrin. After 5 h of reaction at 25 °C, lower the system temperature to 8 °C. Finally, slowly add 7 g of concentrated sulfuric acid. The reaction time is 2.5 h to obtain intermediate I.

[0054] S2: Slowly drop 0.25 g of hydrobromic acid and 3.6 g of hydrogen peroxide into the intermediate I in sequence, and control the reaction time at 18°C ​​for 4 hours to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0055] Example 6

[0056] S1: Add 10.2 g of phenylhydrazine and 19 g of carbonamide into 170 g of distilled water and mix well. Incubate the mixture at 105 °C for 5 h. Then slowly add 4.7 g of acetone cyanohydrin. Incubate the mixture at 20 °C for 4.2 h. Then lower the system temperature to 4 °C. Finally, slowly add 6.5 g of concentrated sulfuric acid. Incubate the mixture for 2.5 h to obtain intermediate I.

[0057] S2: Slowly drop 0.35 g of hydrobromic acid and 4.5 g of hydrogen peroxide into the intermediate I in sequence, and control the reaction time at 232°C for 3.5 h to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

[0058] Characterization and Testing:

[0059] Taking Example 3 as an example, the diazotized oxygen-free gel breaker prepared in Example was characterized by infrared spectroscopy. The results are as follows: Figure 3 shown.

[0060] Figure 3 The infrared spectrum of the diazotized oxygen-free breaker prepared by the present invention. First, in the region of 3000-3500cm-1, obvious absorption peaks can be seen, which usually correspond to the stretching vibration of OH or NH. A significant absorption peak is observed in the region of 1600-1700cm-1, which usually represents the C=C stretching vibration of the aromatic ring, which is consistent with the characteristics of the aromatic ring structure of the azo compound. In addition, the absorption peak in the region of 1400-1500cm-1 may be the characteristic absorption peak of the N=N azo group, which is a characteristic feature of this type of compound. In the region of 1000-1300cm-1, there are also some absorption peaks, which may correspond to the stretching vibration of CN or other characteristic absorption of the aromatic ring. Finally, in the low wave number region of 500-900cm-1, the bending vibration of aromatic CH can be observed, which is a common characteristic absorption region of aromatic compounds. In summary, the position and intensity of the main absorption peaks in the infrared spectrum are consistent with the structural characteristics of azo compounds, and it can be inferred that the diazotized oxygen-free breaker has been successfully synthesized.

[0061] In order to characterize the debonding effect of a diazotized oxygen-free debonding agent for removing polyacrylamide micelles in formations, this study evaluated its performance by recording the cleavage of micelles in the debonding agent solution. At the same time, the cleavage of micelles will produce small molecules of polyacrylamide, which are dissolved in the debonding agent solution, thereby increasing the viscosity of the solution. Therefore, the viscosity change of the debonding agent solution is measured by a rheometer as a supplementary indicator of the debonding effect. Taking Example 3 as an example, the performance test of the diazotized oxygen-free debonding agent prepared in this example was carried out.

[0062] Test method: First, prepare polyacrylamide micelles with a solid content of 5%, place 100g of micelles in a beaker, and record their initial height. Subsequently, add 100g, 200g and 300g of breaker solution to the beaker respectively, and then add catalyst solution respectively, where the catalysts are formic acid and acetic acid; the mass ratio of the two weak acids is 1:1; the mass ratio of the breaker to the catalyst is 1:1.2. The breaker effect is characterized by recording the change in the height of the micelles at different times. At the same time, measure the viscosity of the breaker solution at each time point. For detailed experimental results, see Figure 4 and Figure 5 .

[0063] Figure 4 The figure shows the gel breaking of the micelles with different proportions of gel breakers at different times. Figure 4 It can be seen that under the action of different doses of breaker, the height of the micelle tends to decrease gradually over time. This change reflects the dual effects of free radical chain scission and nitrogen tearing in the breaking mechanism. This trend of gradually decreasing height is the embodiment of the dual breaking mechanism, that is, the breaking mechanism of free radical chain scission and nitrogen tearing micelles becomes more significant with the increase of dose.

[0064] Figure 5 The viscosity of the breaker solution changes after adding different proportions of breaker at different times. Figure 5 It can be seen that under the action of different doses of degumming agent, the viscosity of the solution gradually increases with time. This is because as time goes by, the larger the dose of degumming agent, the more free radicals and nitrogen are generated, resulting in a more thorough destruction of the micelle structure, and the more polyacrylamide segments are released in the solution, so the rate of viscosity increase is also faster. The trend of viscosity increase over time verifies the dual effect in the degumming mechanism, that is, the combined effect of free radical chain scission and nitrogen tearing leads to the gradual degradation of micelles. The larger the dose, the more obvious the degumming effect, resulting in a greater increase in viscosity.

[0065] The preparation method of a diazotized oxygen-free breaker for removing polyacrylamide micelles in formations provided by the present invention utilizes the free radicals and nitrogen generated by the breaker to accelerate the breakage of the long chain of polyacrylamide and the disintegration of micelles, thereby restoring the permeability of the formation, thereby effectively removing the blockage problem. This is sufficient to prove that the dual action mechanism of the breaker provides an efficient and safe solution for unblocking oilfield formations, which helps to improve oilfield production efficiency. At the same time, it has cost advantages, its preparation raw materials are low-cost, the reaction process is simple and easy to control, and it is suitable for large-scale production.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementation schemes of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention.

Claims

1. A diazotized anaerobic breaker for removing polyacrylamide micelles in formations, characterized in that: The method comprises an intermediate I and a mature body I, wherein the intermediate I is a mixed solution of phenylhydrazine, carbonic acid amide, distilled water, acetone cyanohydrin and concentrated sulfuric acid. The mature form I is a mixed solution of intermediate I, hydrobromic acid and hydrogen peroxide.

2. A method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles, comprising the diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 1, characterized in that: The following steps are involved: S1. First, add phenylhydrazine and carbonamide into distilled water and mix them evenly. At temperature T1, react for time t1. Then, slowly add acetone cyanohydrin dropwise. At temperature T2, react for time t2. Then, lower the system temperature to T3. Finally, slowly add concentrated sulfuric acid for reaction time t3 to obtain intermediate I. S2: slowly drop hydrobromic acid and hydrogen peroxide into the intermediate I in sequence, and control the reaction time at temperature T4 to obtain a mature body I. The mature body I is finally cooled, washed, and dried to obtain a diazotized anaerobic breaker for removing formation polyacrylamide micelles.

3. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: In S1, the mass ratio of phenylhydrazine, carbonic acid amide and distilled water is 1:(1-2):(10-20), the reaction temperature T1 is 80-115° C., and the reaction time t1 is 3-5 h.

4. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: In S1, the masses of acetone cyanohydrin and concentrated sulfuric acid are (1-1.2) times and (0.5-1.5) times that of phenylhydrazine, respectively, the reaction temperature T2 is 20-30° C., and the reaction time t2 is 4-6 hours.

5. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: In S1, the reaction temperature T3 is 0-10°C, and the reaction time t3 is 2-3h.

6. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: In S2, the masses of the hydrobromic acid and hydrogen peroxide are (0.02-0.05) times and (0.3-0.5) times that of phenylhydrazine; the reaction temperature T4 is 15-40°C, and the reaction time t4 is 2-4h.

7. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: The general structural formula of the diazotized oxygen-free breaker for removing formation polyacrylamide micelles is:

8. The method for preparing a diazotized anaerobic breaker for removing formation polyacrylamide micelles according to claim 2, characterized in that: The application method of the diazotized oxygen-free breaker for removing polyacrylamide micelles in formations is to inject the breaker and the catalyst alternately into the slugs. Wherein, the catalyst is a mixture of formic acid and fruit acid, the mixing mass ratio of the formic acid and the fruit acid is 1:1, and the mass ratio of the breaker and the catalyst is 1:1.2.

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