A nanometer-micrometer plugging agent, a preparation method and application thereof

Abstract

A nanometer-micrometer plugging agent, comprising starch solid particles and a polymer, the polymer comprising structural units derived from monomer A, monomer B, monomer C and monomer D, wherein monomer A is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride; monomer B is selected from one or more of monomers having the structure shown in formula (I); monomer C is selected from one or more of monomers selected from the structure shown in formula (II); and monomer D is divinyl benzene. The nanometer-micrometer plugging agent of the present application is prepared by Pickering emulsion polymerization, with solid particles adsorbed on the surface of the dispersed phase droplets, preventing the aggregation between the liquid, the obtained oil / water dispersed phase has higher stability, is not easily affected by the external environment, and avoids the foaming problem of surfactants.

Description

TECHNICAL FIELD

[0001] The present application relates to a plugging agent, in particular to a nanometer-micrometer plugging agent and a preparation method and application thereof. BACKGROUND

[0002] In the process of shale gas exploitation, using water-based drilling fluid technology is an important development direction, which has the advantages of green environmental protection and low cost. However, when water-based drilling fluid is used in shale formation, it will face a big problem of wellbore instability: the main component of shale is clay particles less than 6 μm, so it is easy to absorb water and swell, thus causing wellbore collapse. On the other hand, shale contains a large number of naturally developed nanometer-micrometer pores, and has a low porosity and an ultra-low permeability. Due to the ultra-low permeability, the pore pressure in the near-wellbore zone of shale will increase under the action of pressure transmission. Therefore, it is a key for shale gas water-based drilling fluid technology to develop nanometer-micrometer plugging agents with excellent performance, to strengthen the plugging of nanometer-micrometer pores in shale formation by water-based drilling fluid, to effectively reduce the invasion of free water into shale formation, and to weaken the pressure transmission effect.

[0003] The inventors found that a lot of work has been done on nanometer-micrometer plugging agents for drilling fluid, and the plugging agents reported in the literature mainly include nanometer silicon dioxide and some polymer nanoparticles. The nanometer silicon dioxide is easy to self-aggregate, and it is difficult to maintain its original nanometer-micrometer size in the drilling fluid system. In addition, the stability of the polymer nanoparticles is relatively high, and they are generally prepared by emulsion polymerization method, and the products usually exist in the form of emulsion, such as polystyrene-methyl methacrylate (St-MMA) nanoemulsion and polystyrene-butyl acrylate nanoemulsion. The inventors also found that the use of surfactants as emulsifiers can easily cause foaming problems of drilling fluid. SUMMARY

[0004] In order to overcome the problems existing in the prior art, the present application provides a nanometer-micrometer plugging agent and a preparation method and application thereof. For example, one of the purposes of the present application is to provide a nanometer-micrometer plugging agent, which is prepared by Pickering emulsion polymerization, so that solid particles are adsorbed on the surface of the dispersed phase droplets to prevent the aggregation between the liquids, and the obtained oil / water dispersed phase has higher stability and is not easily affected by the external environment, and the foaming problem of surfactants is avoided.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a nanometer-micrometer plugging agent, which comprises starch solid particles and a polymer, and the polymer comprises structural units derived from monomer A, monomer B, monomer C and monomer D. Wherein the monomer A is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride;

[0006] The monomer B is selected from one or more of the monomers having the structure shown in formula (I);

[0007]

[0008] Monomer C is selected from one or more of monomers having the structure shown in Formula (II);

[0009]

[0010] Monomer D is divinyl benzene, and in Formula (I), R1and R2are the same or different, each independently selected from hydrogen, C1-C5 linear alkyl, C3-C5 branched alkyl, or C3-C5 cyclic alkyl, preferably hydrogen or C1-C5 linear alkyl, more preferably hydrogen, methyl, or ethyl;

[0011] In Formula (II), R3and R4are the same or different, each independently selected from hydrogen, C1-C5 linear alkyl, C3-C5 branched alkyl, or C3-C5 cyclic alkyl, preferably hydrogen or C1-C5 linear alkyl, more preferably hydrogen, methyl, or ethyl.

[0012] According to the present application, monomer B can be selected from one or more of styrene and a-methyl styrene; and monomer C can be selected from one or more of methyl acrylate, methyl methacrylate, and ethyl acrylate.

[0013] In some embodiments of the present application, the nanometer-micro plugging agent contains 1-20 parts by weight of structural units derived from monomer A, preferably 5-10 parts by weight; 5-20 parts by weight of structural units derived from monomer B, preferably 10-15 parts by weight; 5-20 parts by weight of structural units derived from monomer C, preferably 10-15 parts by weight; and 0.1-1 parts by weight of structural units derived from monomer D, preferably 2-6 parts by weight.

[0014] In some embodiments of the present application, the starch solid particles are starch solid particles formed by hydrolysis of the amorphous region of starch.

[0015] According to the present application, the amorphous region of starch refers to the amorphous region of starch under a microscope, which is not described in detail in the present application.

[0016] In some embodiments of the present application, the starch solid particles formed by hydrolysis of the amorphous region of starch are contacted with the polymer formed by polymerization of monomer A, monomer B, monomer C, and monomer D to form an emulsion containing the nanometer-micro plugging agent. The emulsion can be dried to form the nanometer-micro plugging agent in a solid state.

[0017] In some embodiments of the present application, the method for preparing the starch solid particles comprises the steps of:

[0018] The system containing substance E, starch and strong alkaline solution is reacted to obtain the reactant I containing the starch solid particles.

[0019] In some embodiments of the present application, the substance E is selected from one or more of thiourea and urea, preferably thiourea.

[0020] In some embodiments of the present application, the strong alkaline solution is prepared by dissolving inorganic alkaline substance in solvent; preferably, the solvent is water; the inorganic alkaline substance is selected from one or more of potassium hydroxide and sodium hydroxide, preferably potassium hydroxide; preferably, in the strong alkaline solution, the content of solvent is 100 parts by weight; the content of inorganic alkaline substance is 1-10 parts by weight, preferably 4-6 parts by weight.

[0021] In some embodiments of the present application, the starch is corn starch or potato starch, preferably corn starch.

[0022] In some embodiments of the present application, the content of the substance E is 1-10 parts by weight, preferably 2-4 parts by weight; the content of starch is 10-30 parts by weight, preferably 15-25 parts by weight.

[0023] In some embodiments of the present application, the reaction conditions include temperature of 0-5°C and time of 2-5h.

[0024] According to the present application, there is no material loss during the preparation process, and the ratio of starch solid particles to polymer in the prepared nanometer and micrometer plugging agent is close to the ratio of raw materials. Similarly, the amount of the strong alkaline solution is close to the amount of raw materials (inorganic alkaline substance and solvent) added.

[0025] In some embodiments of the present application, the preparation method of the starch solid particles can include the steps of:

[0026] 1) adding water in a reaction container, and after adding inorganic alkaline substance and dissolving sufficiently, cooling to 0-5°C;

[0027] 2) adding substance E and starch, and maintaining the temperature at 0-5°C and stirring for 2-5h to obtain a solution containing starch solid particles.

[0028] In some embodiments of the present application, the particle size of the nanometer and micrometer plugging agent is 10-1000nm, preferably 50-500nm.

[0029] In some embodiments of the present application, the particle size of the nanometer and micrometer plugging agent can be measured by Malvern light scattering particle size analyzer, which is not described in detail here.

[0030] In the present application, 10nm-1000nm is the particle size range of the prepared nanometer-micron plugging agent, that is, the particle size of the prepared nanometer-micron plugging agent is in the range of 10nm-1000nm, preferably 50nm-500nm.

[0031] According to the present application, the nanometer-micron plugging agent is a random copolymer cross-linked microsphere obtained by Pickering emulsion polymerization.

[0032] The second aspect of the present application provides a preparation method of the nanometer-micron plugging agent according to the first aspect of the present application, comprising the steps of:

[0033] S1. reacting a system comprising substance E, starch and a strong alkaline solution to obtain a reactant I containing solid particles of the starch;

[0034] S2. mixing the reactant I and monomer A to obtain a mixed system;

[0035] S3. reacting a reaction system comprising the mixed system, monomer B, monomer C and monomer D under the action of an initiator to obtain a reactant II containing the nanometer-micron plugging agent.

[0036] In some embodiments of the present application, the preparation method of the nanometer-micron plugging agent can further comprise the step of: S4. drying the reactant II to obtain the nanometer-micron plugging agent.

[0037] The present application does not have special requirements for the method and conditions of drying, and preferably, spray drying can be used.

[0038] In some embodiments of the present application, in step S1, the substance E is selected from one or more of thiourea and urea, preferably thiourea.

[0039] In some embodiments of the present application, in step S1, the strong alkaline solution is prepared by dissolving an inorganic alkaline substance in a solvent; preferably, the solvent is water; the inorganic alkaline substance is selected from one or more of potassium hydroxide and sodium hydroxide, preferably potassium hydroxide; preferably, in the strong alkaline solution, the content of the solvent is 100 parts by weight; the content of the inorganic alkaline substance is 1-10 parts by weight, preferably 4-6 parts by weight.

[0040] In some embodiments of the present application, in step S1, the starch is corn starch or potato starch, preferably corn starch.

[0041] In some embodiments of the present application, in step S1, the amount of substance E added is 1-10 parts by weight, preferably 2-4 parts by weight; the amount of starch added is 10-30 parts by weight, preferably 15-25 parts by weight, in terms of mass fraction.

[0042] In some embodiments of the present application, in step S1, the reaction conditions include a temperature of 0-5°C and a time of 2-5 hours.

[0043] In some embodiments of the present application, in step S2, monomer A is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride.

[0044] In some embodiments of the present application, in step S2, the temperature at which the reactant I and monomer A are mixed is 0-5°C.

[0045] In some embodiments of the present application, in step S3, monomer B is selected from one or more of monomers having the structure shown in formula (I);

[0046]

[0047] monomer C is selected from one or more of monomers having the structure shown in formula (II);

[0048]

[0049] monomer D is divinylbenzene;

[0050] In formula (I), R1and R2are the same or different and each is independently selected from hydrogen, C1-C5 linear alkyl, C3-C5 branched alkyl or C3-C5 cyclic alkyl, preferably hydrogen or C1-C5 linear alkyl, more preferably hydrogen, methyl or ethyl;

[0051] In formula (II), R3and R4are the same or different and each is independently selected from hydrogen, C1-C5 linear alkyl, C3-C5 branched alkyl or C3-C5 cyclic alkyl, preferably hydrogen or C1-C5 linear alkyl, more preferably hydrogen, methyl or ethyl.

[0052] In some embodiments of the present application, in step S3, the initiator is selected from one of peroxide initiators, preferably one or more of hydrogen peroxide, ammonium persulfate and potassium persulfate, more preferably hydrogen peroxide; preferably, the amount of the initiator added is 1-10 parts by weight, preferably 2-6 parts by weight, in terms of mass fraction.

[0053] In some embodiments of the present application, hydrogen peroxide can be preferably commercially available hydrogen peroxide with a mass concentration of 30%.

[0054] In some embodiments of the present application, in step S3, the reaction conditions include a temperature of 50-80°C and a time of 2-5 hours; preferably, the temperature is 60-70°C and the time is 3-4 hours.

[0055] In some embodiments of the present application, the preparation method of the nanometer-micron plugging agent comprises the following steps:

[0056] 1) adding water into a reaction container, dissolving the inorganic alkaline substance, and cooling to 0-5℃;

[0057] 2) sequentially adding substance E and starch, and stirring for 2-5h while maintaining the temperature at 0-5℃;

[0058] 3) adding monomer A and mixing uniformly while maintaining the temperature at 0-5℃;

[0059] 4) adding monomer B, monomer C and monomer D, and stirring uniformly at room temperature;

[0060] 5) adding initiator, stirring thoroughly, and reacting for 2-5h at 50-80℃ to obtain the reaction product containing the nanometer-micron plugging agent.

[0061] According to the present application, monomer B, monomer C and monomer D can be sequentially added in step 4).

[0062] The third aspect of the present application provides an application of the nanometer-micron plugging agent as described in the first aspect of the present application or the nanometer-micron plugging agent prepared in the second aspect of the present application in drilling fluid, in particular as a plugging agent.

[0063] In some embodiments of the present application, the content of the nanometer-micron plugging agent in the drilling fluid is 0.5-5wt%.

[0064] Compared with the prior art, the present application includes at least one of the following beneficial effects:

[0065] 1) The nanometer-micron plugging agent of the present application is prepared by Pickering emulsion polymerization, and the starch solid particles are adsorbed on the surface of the dispersed phase droplets to prevent the aggregation between the liquids, so that the obtained oil / water dispersed phase has higher stability and is not easily affected by the external environment;

[0066] 2) The nanometer-micron plugging agent of the present application does not use surfactant, thereby avoiding the foaming problem of the surfactant;

[0067] 3) In the present application, the starch solid particles used to stabilize the Pickering emulsion are mostly in nanometer-micron scale, which not only plays a stabilizing role but also strengthens the plugging performance of the polymer nanoemulsion;

[0068] 4) In the nanometer-micron plugging agent of the present application, monomer A, monomer B, monomer C and monomer D are polymerized into a polymer and starch solid particles, which not only ensures the good dispersibility of the nanometer-micron plugging agent in the drilling fluid, but also avoids the foaming problem caused by the introduction of surfactant and strengthens the plugging performance of the drilling fluid. DETAILED DESCRIPTION

[0069] The present application is described in detail below by way of examples, but the scope of the present application is not limited to the following description.

[0070] When the specific conditions are not mentioned in the examples, the routine conditions or the conditions recommended by the manufacturers are used. When the reagents or instruments are not mentioned by the manufacturers, the routine products available on the market are used.

[0071] Example 1

[0072] In a reaction vessel, 100 g of water was added, 10 g of potassium hydroxide was added, and after being completely dissolved, it was cooled to 0°C, 6 g of thiourea, 20 g of starch were sequentially added, and stirring was maintained at 0°C for 3 h. Then, 10 g of acrylic acid was added, and after being mixed uniformly, 10 g of styrene, 10 g of methyl methacrylate, and 0.2 g of divinylbenzene were sequentially added, and after being sufficiently stirred at room temperature, 5 g of hydrogen peroxide was added, and after being sufficiently stirred, it was heated at 80°C for 2 h, and then, by spray drying, a nanometer-micrometer blocking agent A1 having a particle size of 20 nm to 600 nm was obtained.

[0073] Example 2

[0074] In a reaction vessel, 100 g of water was added, 9 g of potassium hydroxide was added, and after being completely dissolved, it was cooled to 5°C, 4 g of thiourea, 15 g of starch were sequentially added, and stirring was maintained at 5°C for 4 h. Then, 12 g of acrylic acid was added, and after being mixed uniformly, 15 g of styrene, 15 g of methyl methacrylate, and 0.3 g of divinylbenzene were sequentially added, and after being sufficiently stirred at room temperature, 3 g of hydrogen peroxide was added, and after being sufficiently stirred, it was heated at 70°C for 3 h, and then, by spray drying, a nanometer-micrometer blocking agent A2 having a particle size of 50 nm to 800 nm was obtained.

[0075] Example 3

[0076] In a reaction vessel, 100 g of water was added, 8 g of potassium hydroxide was added, and after being completely dissolved, it was cooled to 0°C, 6 g of thiourea, 30 g of starch were sequentially added, and stirring was maintained at 0°C for 3 h. Then, 15 g of acrylic acid was added, and after being mixed uniformly, 12 g of styrene, 12 g of methyl methacrylate, and 0.5 g of divinylbenzene were sequentially added, and after being sufficiently stirred at room temperature, 8 g of hydrogen peroxide was added, and after being sufficiently stirred, it was heated at 60°C for 5 h, and then, by spray drying, a nanometer-micrometer blocking agent A3 having a particle size of 80 nm to 1000 nm was obtained.

[0077] Example 4

[0078] In a reaction vessel, 100 g of water was added, 5 g of potassium hydroxide was added, and after being fully dissolved, it was cooled to 5°C, 5 g of thiourea, 10 g of starch were added in turn, and the temperature was maintained at 5°C and stirred for 5 h. Then 8 g of acrylic acid was added, and after being mixed uniformly, 8 g of styrene, 8 g of methyl methacrylate, and 0.2 g of divinylbenzene were added in turn, and they were fully stirred and mixed at room temperature. Then 3 g of hydrogen peroxide was added, and after being fully stirred, it was heated at 70°C for 3 h, and then it was obtained by spray drying to obtain a nanometer-micron plugging agent A3 with a particle size of 60 nm to 900 nm.

[0079] Example 5

[0080] Example 5 is basically the same as Example 1, except that α-methylstyrene is used instead of styrene in Example 1. Under the same conditions, a nanometer-micron plugging agent A5 is prepared.

[0081] Example 6

[0082] Example 6 is basically the same as Example 2, except that methyl acrylate is used instead of methyl methacrylate in Example 2. Under the same conditions, a nanometer-micron plugging agent A6 is prepared.

[0083] Example 7

[0084] Example 7 is basically the same as Example 4, except that urea is used instead of thiourea in Example 4. Under the same conditions, a nanometer-micron plugging agent A7 is prepared.

[0085] Comparative Example 1

[0086] A micron plugging agent was prepared in the manner of Example 1 of CN105670580A to obtain a comparative example B1.

[0087] Comparative Example 2

[0088] A micron plugging agent was prepared in the manner of Example 1 of CN111499790A to obtain a comparative example B2.

[0089] Test Example

[0090] The nanometer-micron plugging agents prepared by the methods of Examples A1-A7 and Comparative Examples B1-B2 above were formulated into a drilling fluid system according to the following formula.

[0091] Base mud formula: 2% evaluation soil + 0.5% low-viscosity carboxymethyl cellulose + 0.5% low-viscosity anionic cellulose + 2% sulfonated phenolic resin + 2% lignite resin + 1% ultra-fine calcium carbonate (2500 mesh) + 6% potassium chloride + 0.5% potassium hydroxide.

[0092] The nanometer-micrometer plugging agent in Examples A1-A7 and Comparative Examples B1-B2 was added in the base paste at 1% respectively to prepare drilling fluid systems, and a blank control drilling fluid system (KB) without the nanometer-micrometer plugging agent was set. After hot rolling aging at 120°C for 16 h, the high temperature and high pressure (HTHP) filtration amount at 120°C was determined by a high temperature and high pressure filter instrument.

[0093] The measurement results are shown in Table 1:

[0094]

[0095]

[0096] As shown in Table 1, compared with the blank control drilling fluid system (KB) without the nanometer-micrometer plugging agent and Comparative Examples B1-B2, the HTHP filtration amount of the drilling fluid system with the nanometer-micrometer plugging agent of Examples A1-A7 was relatively low. The addition of the nanometer-micrometer plugging agent in the drilling fluid components had an important influence on the plugging performance of the drilling fluid.

[0097] It should be noted that the above-described examples are only used to explain the present application and do not constitute any limitation on the present application. The present application is described by referring to typical examples, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The present application can be modified within the scope of the claims, and the present application can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and examples, it does not mean that the present application is limited to the specific examples disclosed therein, on the contrary, the present application can be extended to all other methods and applications with the same function.

Claims

1. A nano-micron plugging agent comprising starch solid particles and a polymer, wherein the polymer comprises structural units derived from monomer A, monomer B, monomer C and monomer D. in, Monomer A is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride; Monomer B is selected from one or more monomers having a structure represented by formula (I); Formula (I) Monomer C is selected from one or more monomers having a structure represented by formula (II); Formula (II) Monomer D is divinylbenzene; In formula (I), R1 and R2 are the same or different and are each independently selected from hydrogen, C1~C5 straight-chain alkyl, C3~C5 branched-chain alkyl or C3~C5 cycloalkyl; In formula (II), R3 and R4 are the same or different and are each independently selected from hydrogen, C1~C5 straight-chain alkyl, C3~C5 branched-chain alkyl or C3~C5 cycloalkyl; In the polymer, the content of the structural unit derived from monomer A is 1 to 20 parts by weight; the content of the structural unit derived from monomer B is 5 to 20 parts by weight; the content of the structural unit derived from monomer C is 5 to 20 parts by weight; and the content of the structural unit derived from monomer D is 0.1 to 1 part by weight; The preparation method of the nano-micron plugging agent comprises the steps of: 1) Add water to the reaction vessel, add inorganic alkaline substances and dissolve them fully, then cool to 0-5°C; 2) adding substance E and starch in sequence, maintaining the temperature at 0-5°C and stirring for 2-5 hours to obtain a reactant I containing the starch solid particles, wherein substance E is selected from one or more of thiourea and urea; 3) Add monomer A and mix well, maintaining the temperature at 0~5℃; 4) Add monomer B, monomer C and monomer D and stir thoroughly at room temperature; 5) Add initiator, stir thoroughly, and react at 50-80°C for 2-5 hours to obtain a reactant containing the nano-micron plugging agent; The particle size of the nano-micron plugging agent is 10nm~1000nm.

2. The nano-micron plugging agent according to claim 1, characterized in that: In formula (I), R1 and R2 are the same or different and are each independently selected from hydrogen or a C1-C5 straight-chain alkyl group.

3. The nano-micron plugging agent according to claim 2, characterized in that: In formula (I), R1 and R2 are the same or different and are each independently selected from hydrogen, methyl or ethyl.

4. The nano-micron plugging agent according to claim 1, characterized in that: In formula (II), R3 and R4 are the same or different and are independently selected from hydrogen or a C1-C5 straight-chain alkyl group.

5. The nano-micron plugging agent according to claim 4, characterized in that: In formula (II), R3 and R4 are the same or different and are each independently selected from hydrogen, methyl or ethyl.

6. The nano-micron plugging agent according to claim 1, characterized in that: In the polymer, the content of the structural unit derived from monomer A is 5 to 10 parts by weight; and / or the content of the structural unit derived from monomer B is 10 to 15 parts by weight; and / or the content of the structural unit derived from monomer C is 10 to 15 parts by weight; and the content of the structural unit derived from monomer D is 2 to 6 parts by weight.

7. The nano-micron plugging agent according to claim 1, characterized in that: The substance E is thiourea; and / or The inorganic alkaline substance is selected from one or more of potassium hydroxide and sodium hydroxide; and / or The starch is corn starch or potato starch; and / or In the system, the content of substance E is 1 to 10 parts by weight; the content of starch is 10 to 30 parts by weight.

8. The nano-micron plugging agent according to claim 1, characterized in that: The inorganic alkaline substance is potassium hydroxide; and / or The starch is corn starch; and / or In the system of step 2), the content of substance E is 2 to 4 parts by weight; and the content of starch is 15 to 25 parts by weight.

9. The nano-micron plugging agent according to claim 8, characterized in that: In step 1), the content of water is 100 parts by weight; the content of the inorganic alkaline substance is 1 to 10 parts by weight.

10. The nano-micron plugging agent according to claim 9, characterized in that: In step 1), the content of water is 100 parts by weight; the content of the inorganic alkaline substance is 4 to 6 parts by weight.

11. The nano-micron plugging agent according to any one of claims 1 to 10, characterized in that: The particle size of the nano-micron plugging agent is 50nm~500nm.

12. A method for preparing the nano-micron plugging agent according to any one of claims 1 to 11, comprising the steps of: 1) Add water to the reaction vessel, add inorganic alkaline substances and dissolve them fully, then cool to 0-5°C; 2) adding substance E and starch in sequence, maintaining the temperature at 0-5°C and stirring for 2-5 hours to obtain a reactant I containing the starch solid particles, wherein substance E is selected from one or more of thiourea and urea; 3) Add monomer A and mix well, maintaining the temperature at 0~5℃; 4) Add monomer B, monomer C and monomer D and stir thoroughly at room temperature; 5) Add an initiator, stir thoroughly, and react at 50-80° C. for 2-5 hours to obtain a reactant containing the nano-micron plugging agent.

13. The method for preparing the nano-micron plugging agent according to claim 12, characterized in that: The initiator is selected from one of the peroxide initiators; and / or The reaction conditions include: temperature of 60° C. to 70° C. and time of 3 to 4 hours.

14. The method for preparing the nano-micron plugging agent according to claim 13, characterized in that: The initiator is selected from one or more of hydrogen peroxide, ammonium persulfate and potassium persulfate.

15. The method for preparing the nano-micron plugging agent according to claim 14, characterized in that: The initiator is hydrogen peroxide.

16. The method for preparing the nano-micron plugging agent according to claim 13, characterized in that: The amount of the initiator added is 1 to 10 parts by weight.

17. The method for preparing the nano-micron plugging agent according to claim 16, characterized in that: The amount of the initiator added is 2 to 6 parts by weight.

18. The method for preparing the nano-micron plugging agent according to any one of claims 12 to 17, characterized in that: In parts by mass, the amount of monomer A added is 1 to 20 parts by weight; the amount of monomer B added is 5 to 20 parts by weight; the amount of monomer C added is 5 to 20 parts by weight; and the amount of monomer D added is 0.1 to 1 part by weight.

19. The method for preparing the nano-micron plugging agent according to claim 18, characterized in that: In parts by mass, the amount of monomer A added is 5 to 10 parts by weight; the amount of monomer B added is 10 to 15 parts by weight; the amount of monomer C added is 10 to 15 parts by weight; and the amount of monomer D added is 2 to 6 parts by weight.

20. Use of the nano-micrometer plugging agent according to any one of claims 1 to 11 or the nano-micrometer plugging agent prepared by the preparation method according to any one of claims 12 to 19 in drilling fluid.

21. The use of the nano-micro plugging agent in drilling fluid according to claim 20, characterized in that: The application is the application of nano-micron plugging agent as a plugging agent.

22. Use of the nano-micro plugging agent in drilling fluid according to claim 20 or 21, characterized in that: In the drilling fluid, the content of the nano-micron plugging agent is 0.5-5wt%.

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