A method for modifying leak-proof material

Abstract

The present invention relates to the field of oil drilling materials, and in particular to a method for modifying a plugging agent material for drilling fluid leakage. The method is to modify the plugging material by coating the plugging material with graphene oxide and polymer self-assembly under the action of pressure difference. A thin film is formed on the plugging material mainly through the principle of self-assembly, thereby improving the hydrophobicity, temperature resistance, oil resistance and mechanical properties of the original plugging material, making it have better dispersibility in the drilling fluid, less prone to swelling problems, maintaining good compression elasticity, and having better matching with cracks, which is conducive to deep crack repair. At the same time, the shape of the crack can be restored after repair, which is conducive to the implementation of bridging and forming a network. It has a good plugging effect on various types of leakage, can better improve the plugging success rate, avoid the occurrence of repeated leakage, and has a good plugging effect on fracture-hole type leakage.

Description

Technical Field

[0001] The invention relates to the field of petroleum drilling materials, in particular to a plugging agent for oil-based drilling fluid leakage. Background Art

[0002] Lost circulation occurs when various working fluids leak into the formation due to pressure differentials during downhole operations such as drilling, cementing, completion, testing, or workover. Once lost circulation occurs, it not only delays drilling time, causes loss of drilling fluid, damages oil and gas formations, interferes with geological logging, and increases drilling costs, but can also lead to a series of complex situations such as stuck pipe, blowouts, and well collapse, and can even cause the wellbore to be scrapped, resulting in significant economic losses.

[0003] With a deeper understanding of the causes of various well leaks, the research and development of plugging materials is also advancing. When lost circulation occurs, the blend ratio of granular, flaky, and fibrous plugging materials is generally adjusted according to the pore size and location of the leaking zone, and appropriate inert materials are added to enhance the plugging effect. Commonly used granular plugging materials include walnut shells, rubber pellets, diatomaceous earth, and asphalt; fibrous materials include sawdust, cotton fiber, and flax fiber; and sheet materials include mica flakes and rice husks. Artificial fractures caused by rapid drilling speeds or rapid run-down can be sealed by utilizing the non-solidifying properties of soft and hard plugging materials, which form a non-flowing, viscous substance. These materials primarily include diesel bentonite slurry, shear-thickening fluid, barite plugs, and lime milk. These types of plugging materials can address partial and return losses caused by pores and cracks, but they are not effective in addressing complex leaks. Therefore, various new plugging agents such as chemical plugging agents, high water loss plugging agents, mixed plugging slurries, etc. have emerged, providing effective means to deal with various types of well leakage and improve the success rate of well leakage treatment.

[0004] With the continuous advancement of technology, various targeted plugging materials have been developed, including high-fluid loss plugging materials, chemical plugging materials, and mixed plugging slurries. After high-fluid loss plugging material slurry enters the leakage zone, it rapidly loses water due to the pressure differential created by the drilling fluid column and the bottom pressure, forming a filter cake that blocks the leakage path. These materials primarily include permeable materials, fibrous materials, diatomaceous earth, and porous inert materials. Chemical plugging materials utilize the static forces, intermolecular forces, and chemical bonds of polymers at the interface to form a bond at the interface, thereby plugging leaks. These materials include gel plugging agents, resin plugging agents, and expansive plugging agents. Mixed plugging slurries are primarily based on specialty cements and mixed cement slurries, with various admixtures added to enhance the early strength and stability of the cement paste, resulting in a higher pressure-bearing capacity. These types of plugging materials are effective in plugging both permeability and fracture-related leaks. However, with the improvement of drilling technology requirements, malignant leakage such as cavitation often occurs, and these conventional plugging materials cannot effectively play a plugging role.

[0005] At present, the plugging materials commonly used in leak-proof construction are mostly bridging plugging materials and chemical gel plugging materials. Chemical plugging mainly achieves its plugging effect through the chemical reaction of polymers, including cross-linking reaction, curing reaction and other methods. Chemical plugging has a good plugging effect on serious leaks, but the chemical plugging reaction is relatively fierce, the construction is complex, and the risk is relatively high. Bridging plugging materials have a simple construction process and low cost, and are most commonly used on site. However, some materials have poor temperature resistance and are prone to decomposition and failure at high temperatures, resulting in repeated leakage in the leaking layer. At the same time, these materials have problems such as sealing the door and cannot be soaked for a long time, and the plugging effect is sometimes not ideal.

[0006] Over the past two decades, researchers have discovered numerous methods for preparing ultrathin films through in-depth exploration. In particular, significant progress has been made in the field of layer-by-layer self-assembly, as this method has proven highly effective in the innovative design and application of ultrathin films with specialized functional properties. For example, invention patent 200710042997.7 proposes a nano-layered calcium carbonate biomimetic composite material. This material is formed by the reaction of low-molecular-weight organic matter with calcium chloride and sodium carbonate, guiding calcite to form a nano-thin layered structure. This layered structure then assembles into a multilayered structure of nano-thin layers. These studies have significantly advanced the biomimetic synthesis of biomineralized materials, but biomimetic materials with natural calcium carbonate structures have yet to be grown, or the methods and material properties require further improvement.

[0007] Some researchers use sponge as a skeleton material with high crack matching properties. For example, invention patent 201410164250.9, "A pressure-bearing plugging agent for oil and gas well drilling and its preparation and application," proposes a pressure-bearing plugging agent for oil and gas well drilling, which is composed of a mixture of elastic sponge fiber, oil well cement, ground slag, calcareous soil, mica powder and clean water, and can be used for pressure-bearing plugging in oil and gas well drilling.

[0008] At present, sponge materials are prone to swelling in oil-based drilling fluids, resulting in loss of elasticity and a significant reduction in plugging effect. Therefore, it is necessary to modify the sponge to improve its hydrophobicity and temperature and oil resistance. Summary of the Invention

[0009] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for modifying a leak-blocking material, wherein the method comprises the following steps: under the action of a pressure differential, graphene oxide and a polymer are self-assembled and coated on the surface of the leak-blocking material to modify the leak-blocking material. The method mainly forms a thin film on the leak-blocking bridging material through the principle of self-assembly, thereby improving the hydrophobicity, temperature resistance, oil resistance and mechanical properties of the original leak-blocking bridging material, making the material have good dispersibility in drilling fluid, not prone to swelling problems, maintaining good compression elasticity, making it better compatible with cracks, facilitating penetration into deep cracks, and at the same time, restoring the shape of the cracks after penetration, facilitating the implementation of bridging network, having a good leak-blocking effect for various types of leaks, being able to better improve the leak-blocking success rate, avoiding the occurrence of repeated leaks, and having a good leak-blocking effect for crack-hole type leaks.

[0010] The method for modifying a plugging material described herein involves coating the plugging material surface with graphene oxide and a polymer self-assembly under a pressure differential to modify the plugging bridging material. The modified plugging material exhibits enhanced hydrophobicity, temperature and oil resistance, and mechanical properties. It exhibits good dispersibility in drilling fluid, is less susceptible to swelling in oil, and maintains good compressive elasticity, thereby enhancing plugging effectiveness.

[0011] The principle of modified membrane formation is the dynamic LbL method, which can force the polyanion membrane-forming liquid and the polycation membrane-forming liquid to be alternately and dynamically filtered on the surface of the base membrane under a certain pressure. The polyions and polyion complexes are retained by the surface of the support membrane, and the flaky material particles are forced to complete self-assembly quickly in a short period of time to form a structurally ordered deposition layer, which is a composite membrane.

[0012] The specific plan is as follows:

[0013] A method for modifying a plugging material comprises the steps of using graphene oxide and anionic polymer to self-assemble into a film on the surface of the plugging material.

[0014] Optionally, the modification method comprises the following steps:

[0015] (1) Add graphene oxide to deionized water, stir, let stand, and take the supernatant to obtain a graphene oxide solution

[0016] (2) adding the anionic polymer in small amounts and multiple times to deionized water, stirring and dissolving to obtain an anionic polymer solution;

[0017] (3) mixing the graphene oxide solution with the anionic polymer solution to obtain a mixed solution;

[0018] (4) Add plugging materials to the mixed liquid, pressurize, filter out, and dry.

[0019] Optionally, in step (1), the mass ratio of graphene oxide to deionized water is 1-2:100-500.

[0020] Optionally, in step (1), the stirring rate is 1000-2000 rpm and the time is 6-8 hours.

[0021] Optionally, in step (1), the standing time is 16 to 24 hours.

[0022] Optionally, in step (2), the mass ratio of the anionic polymer to deionized water is 0.05-0.8:50-100.

[0023] Optionally, in step (2), the stirring rate is 1000-2000 rpm and the time is 1-5 h.

[0024] Optionally, in step (3), the mass ratio of the graphene oxide solution to the anionic polymer solution is 1:1 to 1:4.

[0025] Optionally, in step (4), the ratio of the mass of the plugging material to the volume of the mixed liquid is (0.1-0.4) g:1 ml, and the plugging material needs to be immersed in the mixed liquid.

[0026] Optionally, in step (4), the pressure after pressurization is 2 to 3 MPa.

[0027] Optionally, in step (4), the filtration time is 5 to 20 minutes.

[0028] Optionally, in step (4), the drying is carried out under natural conditions for 24 to 36 hours.

[0029] Optionally, the plugging material is a granular solid material.

[0030] Optionally, the particle size of the plugging material is 0.5 to 5 mm.

[0031] Optionally, the plugging material is selected from at least one of polyurethane sponge, walnut shells, and rubber particles.

[0032] Optionally, the anionic polymer is selected from at least one of polyacrylic acid and anionic polyacrylamide.

[0033] The present invention also provides a plugging material prepared by the modification method, wherein the surface of the plugging material has a self-assembled composite film layer of graphene oxide and anionic polymer.

[0034] The present invention also provides an application of the plugging material prepared by the modification method in preventing leakage of oilfield drilling fluid.

[0035] As a specific embodiment of the present invention, a method for modifying a plugging material comprises the following steps:

[0036] (1) Preparation of GO (graphene oxide) solution: Weigh 1–2 g of GO solid powder and add 100–500 g of deionized water to the mixing cup of a high-speed blender. Stir at high speed. Add the previously weighed 1–2 g of GO in small amounts to the deionized water over a period of 6–8 h. After stirring, let the GO solution stand for 16–24 h and collect the supernatant.

[0037] (2) Preparation of polymer solution: Weigh 0.05-0.8 g of polymer and add it in small amounts several times to a stirring cup containing 50-100 g of deionized water, and stir at high speed using a high-speed stirrer until it is completely dissolved, thereby obtaining a polymer solution.

[0038] (3) Preparation of mixed solution: The prepared GO solution was mixed with the polymer solution to obtain a mixed solution.

[0039] (4) Self-assembly of graphene oxide and polymer on the surface of plugging material: Take 100 ml of the mixed liquid and pour it into the slurry cup of the drilling fluid high temperature and high pressure filter loss meter (drilling fluid performance testing instrument), then add the plugging material, and then pressurize it to 2-3 MPa, filter it for 5-20 minutes, take out the plugging material, and dry it naturally for 24-36 hours.

[0040] In the above specific embodiment, the plugging material is a granular solid material such as polyurethane sponge, walnut shell, rubber particles, quartz, rock chips, etc. After self-assembly, graphene oxide and polymer will form a thin film on the surface of the particles, which is coated on the surface of the plugging material. The coating layer has good hydrophobic effect.

[0041] In the above specific embodiment, the polymer is an anionic polyelectrolyte such as hydrolyzed polyacrylic acid, hydrolyzed polyacrylamide, etc.

[0042] Furthermore, the high-temperature and high-pressure filter loss instrument in the above specific embodiment can be equivalent to a mechanism that can generate a pressure difference and cause filter loss.

[0043] The present invention has the following beneficial effects:

[0044] (1) The plugging material prepared by the method of the present invention has good temperature resistance and will not fail at high temperatures, thus avoiding the occurrence of repeated leakage.

[0045] (2) The plugging material prepared by the method of the present invention has a composite film formed on its surface. The composite film has hydrophobicity, oil resistance and a certain mechanical strength, is easy to disperse in the oil-based drilling fluid, and does not affect the rheological properties of the drilling fluid. This solves the shortcoming that conventional plugging materials cannot be dispersed in the oil-based drilling fluid, resulting in unsatisfactory plugging effect.

[0046] (3) The plugging material prepared by the method of the present invention has good oil resistance, is not easy to swell, can maintain elasticity in oil-based drilling fluid, has good compatibility with cracks, and is conducive to deep cracks. At the same time, it can restore its shape after cracking, which is conducive to the implementation of bridging and forming a network. It has a good plugging effect on various types of leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The contact angle measurement results of the composite film on the surface of the modified plugging material in Example 3 are shown.

[0048] Figure 2 This is a scanning electron microscope image of the cross-section of the composite membrane on the surface of the modified plugging material in Example 2. DETAILED DESCRIPTION

[0049] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0050] The graphene oxide used in each embodiment of the present invention was purchased from Jining Lit Nanotechnology Co., Ltd., model LN-GP;

[0051] Polyacrylic acid was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0052] Polyacrylamide was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0053] The drilling fluid high-temperature and high-pressure filter loss meter is from Qingdao Haitong Yuanda Instrument Co., Ltd., model GGS42.

[0054] Example 1

[0055] (1) Preparation of GO (graphene oxide) solution: Weigh 1 g of GO solid powder and add 100 g of deionized water to the mixing cup of a high-speed blender. Stir at high speed. Add the previously weighed 1 g of GO in small portions to the deionized water and stir at 1200 rpm for 6 h. After stirring, let the GO solution stand for 24 h, and collect the supernatant to obtain the GO solution.

[0056] (2) Preparation of polymer solution: 0.05 g of polyacrylic acid was weighed and added in small amounts to a stirring cup containing 50 g of deionized water. The mixture was stirred at 1800 rpm for 5 h using a high-speed stirrer until the mixture was completely dissolved, thereby obtaining a polymer solution.

[0057] (3) Preparation of mixed solution: Mix the prepared GO solution with the polymer solution to obtain a mixed solution.

[0058] (4) Self-assembly of graphene oxide and polymer on the surface of plugging material: 100 ml of the mixed solution was poured into the slurry cup of the drilling fluid high temperature and high pressure loss meter, and 20 g of walnut shell particles with a particle size of 5 mm was added. Then the pressure was increased to 2 MPa and the filter was lost for 20 minutes. The walnut shell particles were taken out and dried naturally for 36 hours.

[0059] Example 2

[0060] (1) Preparation of GO (graphene oxide) solution: Weigh 2 g of GO solid powder and add 500 g of deionized water to the mixing cup of a high-speed blender. Stir at high speed. Add the previously weighed 2 g of GO in small portions to the deionized water and stir at 1200 rpm for 8 h. After stirring, let the GO solution stand for 24 h, and collect the supernatant to obtain the GO solution.

[0061] (2) Preparation of polymer solution: 0.8 g of polyacrylamide was weighed and added in small amounts to a stirring cup containing 100 g of deionized water. The mixture was stirred at 1800 rpm using a high-speed stirrer until the polymer was completely dissolved, thereby obtaining a polymer solution.

[0062] (3) Preparation of mixed solution: Mix the prepared GO solution with the polymer solution to obtain a mixed solution.

[0063] (4) Self-assembly of graphene oxide and polymer on the surface of plugging material: 100 ml of the mixed solution was poured into the slurry cup of the drilling fluid high temperature and high pressure loss meter, and then 10 g of 5 mm polyurethane sponge particles were added. Then, the pressure was increased to 3 MPa and the loss was measured for 5 min. The polyurethane sponge particles were taken out and dried naturally for 24 h.

[0064] Depend on Figure 2 Scanning electron microscope images show that a structurally ordered deposition layer, namely a composite film layer, is formed on the surface of the plugging material.

[0065] Example 3

[0066] (1) Preparation of GO (graphene oxide) solution: Weigh 1.5 g of GO solid powder and add 250 g of deionized water to the mixing cup of a high-speed blender. Stir at high speed. Add the previously weighed 1.5 g of GO in small portions to the deionized water and stir at 1200 rpm for 6 h. After stirring, let the GO solution stand for 24 h, and collect the supernatant to obtain the GO solution.

[0067] (2) Preparation of polymer solution: 0.4 g of polyacrylamide was weighed and added in small amounts to a stirring cup containing 80 g of deionized water. The mixture was stirred at 1800 rpm using a high-speed stirrer until the mixture was completely dissolved, thereby obtaining a polymer solution.

[0068] (3) Preparation of mixed solution: Mix the prepared GO solution with the polymer solution to obtain a mixed solution.

[0069] (4) Self-assembly of graphene oxide and polymer on the surface of plugging material: Take 100 ml of the mixed solution and pour it into the slurry cup of the drilling fluid high temperature and high pressure loss meter, then add 40 g of 5 mm rubber particles, then pressurize to 2.5 MPa, filter for 10 minutes, take out the rubber particles, and dry them naturally for 30 hours.

[0070] Comparative Example 1

[0071] (1) Preparation of GO (graphene oxide) solution: Weigh 2 g of GO solid powder and add 500 g of deionized water to the mixing cup of a high-speed blender. Stir at high speed. Add the previously weighed 2 g of GO in small portions to the deionized water and stir at 1200 rpm for 8 h. After stirring, let the GO solution stand for 24 h, and collect the supernatant to obtain the GO solution.

[0072] (2) Film formation of graphene oxide on the surface of plugging material: 100 ml of GO solution was poured into the slurry cup of the drilling fluid high-temperature and high-pressure loss meter, and 10 g of 5 mm polyurethane sponge particles were added. Then, the pressure was increased to 3 MPa and the loss was measured for 5 min. The polyurethane sponge particles were taken out and dried naturally for 24 h.

[0073] Comparative Example 2

[0074] (1) Preparation of polymer solution: 0.8 g of polyacrylamide was weighed and added in small amounts to a stirring cup containing 100 g of deionized water. The mixture was stirred at 1800 rpm using a high-speed stirrer until the polymer was completely dissolved, thereby obtaining a polymer solution.

[0075] (2) Film formation of polymer on the surface of plugging material: Take 100 ml of polymer solution and pour it into the slurry cup of drilling fluid high temperature and high pressure loss meter, then add 10 g of 5 mm polyurethane sponge particles, then pressurize to 3 MPa, filter for 5 minutes, take out the polyurethane sponge particles, and dry them naturally for 24 hours.

[0076] Comparative Example 3

[0077] Take 100 ml of clean water and pour it into the slurry cup of the drilling fluid high-temperature and high-pressure filter loss instrument, then add 10 g of 5 mm polyurethane sponge particles, then pressurize to 3 MPa, filter for 5 minutes, take out the polyurethane sponge particles, and dry them naturally for 24 hours.

[0078] Performance evaluation and testing

[0079] 1. Temperature resistance test

[0080] The plugging material to be tested is heated in a high-temperature roller heating furnace, and then a high-temperature resistance evaluation experiment is conducted based on the mass retention rate.

[0081]

[0082] Wherein, α is the mass retention rate, %; M1 is the mass of the material before hot rolling, g; M2 is the mass of the material after hot rolling, g.

[0083] Table 1. Mass retention after 16h hot rolling at 120℃

[0084] Serial number Plugging materials prepared in different embodiments Quality retention rate% 1 Example 1 95.2 2 Example 2 94.6 3 Example 3 95.8 4 Comparative Example 1 92.5 5 Comparative Example 2 91.5 6 Comparative Example 3 91.0

[0085] The test results show that the mass retention rate of the plugging materials prepared in the examples after high-temperature hot rolling is greater than that of the plugging materials prepared in the comparative examples, indicating that the plugging materials prepared by the modification method of the present invention have better temperature resistance than the plugging materials not prepared by the preparation method of the present invention.

[0086] 2. Oil resistance test

[0087]

[0088] Wherein, β is the tensile strength retention rate, %; P1 is the tensile strength of the material before immersion, kPa; P2 is the tensile strength of the material after immersion, kPa.

[0089] Table 2. Tensile strength retention after immersion in diesel for 16 hours at 100°C

[0090] Serial number Leakage-proof skeleton materials prepared in different embodiments Tensile strength retention rate% 1 Example 1 82.5 2 Example 2 79.6 3 Example 3 85.1 4 Comparative Example 1 55.7 5 Comparative Example 2 51.3 6 Comparative Example 3 50.2

[0091] The test results show that the tensile strength retention rate of the plugging materials prepared in the examples after being soaked in diesel is greater than that of the plugging materials prepared in the comparative examples, indicating that the plugging materials prepared by the modification method of the present invention have better oil resistance than the plugging materials not prepared by the preparation method of the present invention.

[0092] 3. Mechanical properties test

[0093] The tensile strength of the elastic mesh plugging material was tested with reference to the national industry standard GB / T 6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials".

[0094] Table 3. Tensile strength test results

[0095] Serial number Leakage-proof skeleton materials prepared in different embodiments Tensile strength / MPa 1 Example 1 4.1 2 Example 2 3.9 3 Example 3 4.6 4 Comparative Example 1 2.9 5 Comparative Example 2 3.3 6 Comparative Example 3 2.0

[0096] The test results show that the tensile strength of the plugging materials prepared in the examples is greater than that of the plugging materials prepared in the comparative examples, indicating that the mechanical properties of the plugging materials prepared by the modification method of the present invention are better than those of the plugging materials not prepared by the preparation method of the present invention.

[0097] 4. Hydrophobicity test of composite film on the surface of plugging material

[0098] The contact angle of water droplets on the surface of the composite film of the plugging material was measured using a HARKE-SPCA contact angle meter (Beijing HARKE Test Instrument Factory) to test and evaluate the hydrophobicity of the composite film on the surface of the plugging material in Example 3. According to the modification method of the present invention, solid particles with relatively flat surfaces were modified. After the composite film was formed on the surface, the contact angle of water droplets on the surface was measured using a contact angle meter. The specific results are shown in the attached Figure 1 .

[0099] from Figure 1 In the figure, it can be seen that the water droplets are obviously hydrophobic on the surface of the composite membrane.

[0100] 5. Effect of modified plugging materials on drilling fluid rheology

[0101] The rheological changes before and after adding plugging materials into oil-based drilling fluid were tested.

[0102] Oil-based drilling fluid formula: base oil + CaCl2 (25%) + 2% to 3% emulsifier + 1% to 3% wetting agent + 2% to 3% organic soil + 2% CaO + barite.

[0103] Table 4. Changes in drilling fluid rheological properties

[0104] AV (mPa·s) PV (mPa·s) YP(Pa) Before adding plugging material 39 32 13 After plugging material is added 42 33 14

[0105] It can be seen that after adding the plugging material of Example 3, the apparent viscosity and plastic viscosity of the drilling fluid do not change much and are within a reasonable range, indicating that the modified plugging material has little effect on the rheological properties of the drilling fluid.

[0106] 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.

[0107] 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 method for modifying a plugging material, characterized in that: The method comprises adopting graphene oxide and anionic polymer to self-assemble into a film on the surface of the plugging material; the anionic polymer is selected from at least one of polyacrylic acid and anionic polyacrylamide.

2. The modification method according to claim 1, characterized in that The steps of the modification method include: (1) adding graphene oxide to deionized water, stirring, allowing to stand, and collecting the supernatant to obtain a graphene oxide solution; (2) Add the anionic polymer in small amounts and multiple times to deionized water, stir, and dissolve to obtain an anionic polymer solution; (3) mixing the graphene oxide solution with the anionic polymer solution to obtain a mixed solution; (4) Add plugging materials to the mixed liquid, pressurize, filter out, and dry.

3. The modification method according to claim 2, characterized in that In step (1), the mass ratio of graphene oxide to deionized water is 1-2:100-500; And / or, in step (1), the stirring rate is 1000-2000 rpm and the time is 6-8 hours; And / or, in step (1), the standing time is 16 to 24 hours.

4. The modification method according to claim 2, characterized in that In step (2), the mass ratio of the anionic polymer to deionized water is 0.05-0.8:50-100; And / or, in step (2), the stirring rate is 1000-2000 rpm and the time is 1-5 hours.

5. The modification method according to claim 2, characterized in that In step (3), the mass ratio of the graphene oxide solution to the anionic polymer solution is 1:1 to 1:

4.

6. The modification method according to claim 2, characterized in that: In step (4), the ratio of the mass of the plugging material to the volume of the mixed liquid is (0.1-0.4) g:1 ml; And / or, in step (4), the pressure after pressurization is 2-3 MPa; And / or, in step (4), the filtration time is 5 to 20 minutes; And / or, in step (4), the drying is carried out under natural conditions for 24 to 36 hours.

7. The modification method according to any one of claims 1 to 6, characterized in that The plugging material is a granular solid material; And / or, the particle size of the plugging material is 0.5-5 mm; And / or, the plugging material is selected from at least one of polyurethane sponge, walnut shells, and rubber particles.

8. A plugging material obtained by the modification method according to any one of claims 1 to 7, characterized in that: The surface of the plugging material is provided with a graphene oxide and anionic polymer self-assembled composite film layer.

9. Use of the plugging material obtained by the modification method according to any one of claims 1 to 7 in preventing leakage of oilfield drilling fluid.

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