Well drilling plugging agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of petroleum drilling engineering, and particularly discloses a drilling plugging agent as well as a preparation method and application thereof. According to the plugging agent, nano silicon dioxide and graphene oxide serve as a composite matrix, and the well drilling plugging agent with excellent dispersion stability, compact plugging performance, temperature resistance, salt resistance and reservoir friendliness is obtained through silane coupling agent graft modification and polymer copolymerization composite modification. The technical defects that an existing nano plugging agent is prone to agglomeration, poor in compatibility with drilling fluid, insufficient in extreme working condition resistance and the like are overcome, the preparation process is simple and controllable, the cost is relatively low, the plugging agent can be added into water-based or oil-based drilling fluid according to the mass ratio of 0.5-5%, the plugging agent is suitable for shale, deep high-temperature high-pressure high-salt complex stratums and the like, a compact plugging layer can be formed, and the plugging effect is good. Shale micro-cracks and deep stratum large cracks are effectively blocked, and the problems that a traditional blocking agent is prone to agglomeration, poor in extreme working condition resistance and the like are solved.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid treatment agents in oil drilling engineering, specifically to a drilling plugging agent and its preparation method and application. This drilling fluid plugging agent is suitable for drilling plugging and protection in complex formations such as shale, deep high-temperature and high-pressure formations, and high-salt formations. Background Technology

[0002] As oil and gas exploration and development expands into deeper, ultra-deeper, and unconventional resources (shale gas, tight oil and gas), drilling projects face increasingly complex geological conditions, leading to frequent problems such as wellbore instability and drilling fluid loss, which severely restrict drilling efficiency and reservoir recovery. Shale formations are characterized by low porosity and permeability, well-developed microfractures (fracture width 5-300 nm), and high clay mineral content, making them prone to hydration expansion and collapse during drilling. Deep formations, on the other hand, face extreme conditions such as high temperature (120-260℃), high pressure (70-100 MPa), and high salinity (salinity 10-30%), placing stringent requirements on the performance of drilling plugging agents.

[0003] The core function of drilling plugging agents is to seal formation loss channels, such as pores, fractures, and caverns, prevent drilling fluid filtrate from entering, maintain stable wellbore pressure, and protect the reservoir from contamination. Traditional plugging agents, such as calcium carbonate, quartz sand, and sulfonated asphalt, suffer from drawbacks such as large particle size, inability to match the nanoscale microfractures in shale formations, poor dispersibility, easy agglomeration, and insufficient temperature and salt resistance, resulting in poor plugging effects in complex formations. Nanomaterials, due to their small size effect and high specific surface area, can penetrate microfractures that traditional plugging agents cannot reach, forming a tight-sealed plugging layer, making them a research hotspot in drilling plugging agents. Currently, commonly used nanomaterials include nano-silica, graphene oxide, and nano-calcium carbonate.

[0004] Nano-silica has advantages such as wide availability, low price, high thermal stability, and easy surface modification. In drilling fluids, it forms a plugging layer through physical filling and chemical cross-linking. However, nano-silica is rich in silanol groups (-OH), resulting in high surface energy. This makes it prone to aggregation in aqueous or drilling fluid systems, leading to increased particle size, loss of nano-effect, and reduced plugging effectiveness. To address this issue, existing technologies often use silane coupling agents (such as KH-570 and KH-550) to modify its surface, reducing the number of hydroxyl groups and improving dispersion stability. For example, CN120988215A discloses a nano-plugging agent for drilling fluids, prepared by reacting a core plugging agent and a shell plugging agent. The core plugging agent is prepared by reacting nano-silica, γ-methacryloyloxypropyltrimethoxysilane, and a first component of vinylphosphonic acid, possessing secondary plugging capability. The shell plugging agent is prepared by reacting a second component of vinylphosphonic acid, styrene, and 2-dodecen-1-ylsuccinic anhydride, exhibiting flexibility. The nano-plugging agent combines rigid support with flexible deformation capability, significantly improving the high-temperature stability and compressive strength of the plugging layer and enhancing the chemical bonding force between the plugging agent and the rock. The hydrolyzable methoxy groups retained in the core layer provide secondary plugging functionality, extending the effective period of the plugging. CN118027918A discloses a high-temperature resistant modified mesoporous silica nano-plugging agent, using amino-containing silane coupling agents, enamine compounds, diene-containing ether compounds, and amino-containing benzenesulfonic acid compounds as raw materials. This plugging agent can be directly added to water-based drilling fluids with minimal impact on the rheological properties of the water-based drilling fluid; when the addition amount is 1.0%, the plugging rate reaches 91.67%. CN110982495A discloses a modified nano-silica plugging agent, the preparation method of which includes: (1) contacting nano-silica with a mixture containing acrylic acid and polybutyl methacrylate and ultrasonically dispersing it to obtain an oil phase solution; (2) contacting water, polyethylene glycol octylphenyl ether and sodium bicarbonate and emulsifying them to obtain a first emulsion solution; (3) subjecting the oil phase solution and the first emulsion solution to a second emulsion treatment to obtain a second emulsion solution; (4) contacting the second emulsion solution with a water-soluble initiator under nitrogen protection, and centrifuging and drying the product obtained after contact. This plugging agent can enter the formation pores of mudstone and limestone interlayers and plug them, has good pressure bearing capacity, can prevent pressure transmission and enlargement of pores, and can meet the needs of oil and gas extraction in mudstone and shale.

[0005] Graphene oxide (GO), as a two-dimensional nanomaterial, has an extremely high specific surface area (2630 m²). 2 With a tensile strength of ≈130 GPa and a permeability as low as 10 g / g, the sheet structure can form a dense barrier layer through stacking and overlapping. -18 m 2The graphene oxide exhibits excellent performance in microfracture sealing. Furthermore, the surface of graphene oxide is rich in oxygen-containing functional groups such as hydroxyl, carboxyl, and epoxy groups, making it readily react with other materials and possessing great modification potential. For example, CN111808581B discloses a chitosan-graphene oxide nano-hydrogel plugging agent. This plugging agent is a chitosan-graphene oxide nano-hydrogel, and the raw materials for synthesizing the chitosan-graphene oxide nano-hydrogel include chitosan, clay minerals, graphene oxide, and konjac oxide. The chitosan-graphene oxide nano-hydrogel of this invention, as a nano-plugging agent, has a particle size distribution approximately between 20-45 nm, effectively sealing micro and nano-sized pores in shale wellbores, thereby effectively stabilizing the wellbore and preventing collapse. The water-based drilling fluid used in this invention exhibits good rheological, stability, and plugging properties under shale formation conditions. CN114015421B discloses a fully adaptable modified nano-graphene plugging anti-collapse drilling fluid. The preparation method involves: first contacting nano-graphene with mixed acid to obtain a mixed solution; then, under ice bath conditions, adding potassium chlorate dropwise to the mixed solution for modification treatment to obtain modified nano-graphene; finally, contacting the modified nano-graphene with water to obtain a modified nano-graphene slurry. This drilling fluid can achieve comprehensive plugging of micro- and nano-pores in basalt wellbore walls. CN114656945A discloses a novel functionalized graphene oxide plugging agent. The raw materials for synthesizing this plugging agent include graphene oxide, styrene, nonylphenol polyoxyethylene ether, sodium dodecyl sulfate, persulfate, acrylate compounds, acrylic compounds, and aminosilane compounds. This functionalized graphene oxide plugging agent has a particle size distribution between 60-1200 nm, which can effectively seal nanopores in shale formations, thereby effectively stabilizing the wellbore and preventing collapse. The plugging agent of this invention has little impact on the performance of drilling fluid, which is beneficial to reducing drilling fluid filtration loss. However, graphene oxide has problems such as high preparation cost, limited large-scale application, easy agglomeration under high salinity and high temperature, and the need to optimize its compatibility with traditional drilling fluid systems. In environments with salinity >25% and temperature >200℃, the surface electrostatic repulsion is weakened, and the layers are prone to agglomeration through van der Waals forces, affecting the plugging efficiency.

[0006] Although nano-silica and graphene oxide have shown good application prospects in drilling plugging agents, single nanomaterials still have the following defects: (1) Single nano-silica: insufficient plugging density, especially limited effect on micro-cracks with a width of <100nm; in deep high-temperature and high-pressure formations, the mechanical strength and shear resistance of the plugging layer need to be improved; (2) Single graphene oxide: too high cost, difficult to apply on a large scale; dispersion stability depends on complex modification, and it is easy to adsorb and agglomerate when mixed with inorganic particles (such as barite and bentonite); (3) Existing composite modification technology: mostly focuses on the surface modification of single nanomaterials, lacks research on synergistic composite modification of two or more nanomaterials, and fails to give full play to the complementary advantages of different nanomaterials; the long-term stability of the modified material under extreme working conditions is insufficient; the compatibility optimization with the drilling fluid system is insufficient, and some modifiers will affect the rheology of the drilling fluid.

[0007] Current plugging agents still have many shortcomings, especially in sealing nanoscale fractures, where their plugging effect urgently needs further improvement. Therefore, there is an urgent need to develop a drilling plugging agent that can be applied to complex formations such as shale, deep high-temperature and high-pressure formations, and high-salinity formations to solve problems such as wellbore stability and reservoir contamination. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a drilling plugging agent, which is composed of a composite matrix, an organic modifier, and auxiliary additives. The composite matrix is ​​a mixture of nano-silica and graphene oxide in a mass ratio of 5-20:1. The organic modifier is a compound system of silane coupling agent and unsaturated monomer. This plugging agent combines the advantages of low cost and high filler content of nano-silica with the high density and high mechanical strength of graphene oxide. The organic modification solves the problem of easy agglomeration of nanoparticles, improves temperature and salt resistance and compatibility with drilling fluid, and can effectively meet the drilling plugging needs of complex formations, thus having significant industrial application value.

[0009] To achieve the above objectives, the first aspect of this invention provides a drilling plugging agent, comprising a composite matrix, an organic modifier, and auxiliary additives. The components, by mass percentage, are: 60-85% composite matrix, 10-30% organic modifier, and 1-10% auxiliary additives. The composite matrix is ​​a mixture of nano-silica and graphene oxide in a mass ratio of 5-20:1, preferably 8-15:1. The organic modifier is a compound system of a silane coupling agent and an unsaturated monomer, wherein the mass ratio of the silane coupling agent to the unsaturated monomer is 1:2-5. The auxiliary additives include 0.3-3 wt% dispersant, 0.2-2 wt% antioxidant, and 0.5-5 wt% crosslinking agent. By precisely controlling the proportions of the composite matrix, organic modifier, and auxiliary additives, synergistic effects among the components can be achieved.

[0010] Preferably, the nano-silica has a particle size of 20-200 nm and a specific surface area of ​​100-400 m². 2 / g; the graphene oxide sheet thickness is 0.8-2nm, and the lateral dimension is 0.5-5μm. The composite matrix is ​​a mixture of nano-silica and graphene oxide in a mass ratio of 5-20:1, combined with nano-silica with a particle size of 20-200nm and a lateral dimension of 100-400μm. 2 The optimized parameters of / g specific surface area and 0.8-2nm graphene oxide sheet thickness significantly improve the specific surface area and interfacial interaction capability of the substrate.

[0011] Preferably, the nano-silica has a particle size of 50-150 nm and a specific surface area of ​​200-300 m². 2 / g; the thickness of the graphene oxide sheets is 0.8-2nm, and the lateral dimension is 0.5-5μm. Nano-silica, as a low-cost filler, can enter microcracks to form a bridging framework, filling the gaps between graphene oxide sheets and improving the density of the sealing layer. If the particle size is too large, it cannot enter the nanoscale microcracks; if the particle size is too small, it is prone to agglomeration and the cost increases. The two-dimensional sheet structure of graphene oxide can overlap to form a dense barrier film, preventing the intrusion of drilling fluid filtrate; its mechanical strength can enhance the shear resistance and pressure bearing capacity of the sealing layer. If the lateral dimension is too large, it is difficult to disperse in drilling fluid. In this composite matrix, the particle filling of nano-silica and the sheet film formation of graphene oxide combine to form a "particle-sheet" composite sealing structure. Compared with single nanomaterials, the porosity of the sealing layer is reduced by 30-50%, the permeability is reduced by more than an order of magnitude, and the pressure bearing strength is increased by 40-60%.

[0012] Preferably, the silane coupling agent is selected from one or more of KH-570 (3-methacryloyloxypropyltrimethoxysilane), KH-550 (3-aminopropyltriethoxysilane), and KH-560 (3-epoxypropoxypropyltrimethoxysilane). The hydrolysis product (silanol group) of the silane coupling agent can undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the composite matrix to form Si-O-Si covalent bonds, reducing the number of surface hydroxyl groups, lowering the surface energy, and inhibiting agglomeration. At the same time, the organic functional groups (such as double bonds and amino groups) of the silane coupling agent can undergo copolymerization reactions with unsaturated monomers to introduce flexible segments, improve the flexibility of the plugging agent and its compatibility with drilling fluid. The unsaturated monomer is selected from one or more of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and N-vinylpyrrolidone (NVP). The organic modifier is compounded with the unsaturated monomer at a ratio of 1:2-5, preferably 1:3-4. The surface properties of the composite matrix are improved through chemical grafting modification, and a strong chemical bond is formed with the composite matrix, which enhances the film density of the blocking agent and further improves the dispersion stability and temperature and salt resistance.

[0013] Preferably, the dispersant is one of polycarboxylate salts or naphthalene sulfonate formaldehyde condensates; the antioxidant is a hindered phenolic antioxidant, such as octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], butylated hydroxyanisole, triazine-inhibiting phenol, etc.; the crosslinking agent is one of N,N'-methylenebisacrylamide or ethylene glycol dimethacrylate. The dispersant further inhibits the aggregation of the composite matrix through electrostatic repulsion and steric hindrance, improving the dispersion stability in drilling fluid; the antioxidant prevents the oxidative degradation of polymer chains during modification, improving the long-term storage stability and temperature resistance of the plugging agent; the crosslinking agent enables unsaturated monomers to form a crosslinked polymer network on the surface of the composite matrix, enhancing the mechanical strength and shear resistance of the plugging layer. Specific types of auxiliary additives further optimize the dispersion stability, anti-aging properties, and crosslinking strength of the system, laying a core foundation for efficient plugging.

[0014] A second aspect of this invention provides a method for preparing a drilling plugging agent, comprising the following steps: (1) Preparation of composite matrix: Nano-silica and graphene oxide are added to deionized water at a mass ratio of 5-20:1, ultrasonically dispersed at an ultrasonic power of 300-500W for 30-60min, then stirred at 60-80℃ for 2-4h, centrifuged and vacuum dried at 60-80℃ for 12-24h to obtain silica-graphene composite matrix; (2) Pretreatment: The composite matrix obtained in step (1) is added to a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 3:1, the pH is adjusted to 4-6, and ultrasonic dispersion is performed for 20-30 min to obtain a composite matrix dispersion. This treatment further ensures that the composite matrix is ​​uniformly dispersed and avoids agglomeration.

[0015] (3) Organic modification: Add organic modifier to the composite matrix dispersion, wherein the amount of silane coupling agent is 2-17% of the mass of the composite matrix and the amount of unsaturated monomer is 8-42% of the mass of the composite matrix. After stirring evenly, add auxiliary additives, heat to 60-80℃ under nitrogen protection, add 0.5-2% of the mass of unsaturated monomer initiator, and react for 4-8 hours; (4) Post-processing: After the reaction is completed, the product is washed until neutral, centrifuged, and vacuum dried at 60-80℃ for 12-24h. Then it is ground through a 200-mesh sieve to obtain a silicon oxide-graphene composite organic modified drilling plugging agent.

[0016] Preferably, the initiator in step (3) is selected from one of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile; the stirring rate of the reaction is 300-500 r / min.

[0017] Preferably, the hydrolysis time of the silane coupling agent in step (3) is 1-2 hours, and the hydrolysis temperature is 40-60°C; the copolymerization reaction temperature of the unsaturated monomer is 65-75°C, and the reaction time is 3-6 hours. The directional hydrolysis of the silane coupling agent and the copolymerization reaction of the unsaturated monomer ensure the sufficiency of organic modification and the stability of the reaction.

[0018] A third aspect of this invention provides an application of a drilling plugging agent, wherein the plugging agent is added to a drilling fluid system at 0.5-5% of the drilling fluid mass, stirred evenly, and then used for drilling operations; the drilling fluid system includes water-based drilling fluid and oil-based drilling fluid. This drilling fluid is suitable for shale, sandstone, carbonate rock, and other formations, and is particularly suitable for deep, high-temperature, high-pressure formations (temperature 120-260℃, pressure 70-100MPa), high-salinity formations (salinity 10-30%), and formations with well-developed microfractures (fracture width 5-300nm).

[0019] Preferably, when the plugging agent is used in a water-based drilling fluid, the drilling fluid formulation includes: 4-8 wt% bentonite, 0.2-0.5 wt% sodium carbonate, 2-5 wt% potassium chloride, 0.3-1 wt% xanthan gum, 0.5-2 wt% filtration loss reducer, 0.5-5 wt% plugging agent, and the balance being water; when used in an oil-based drilling fluid, the drilling fluid formulation includes: 3-5 wt% emulsifier, 1-2 wt% organic clay, 2-4 wt% filtration loss reducer, 0.5-5 wt% plugging agent, and a density adjusted to 1.2-1.8 g / cm³. 3 The remainder is white oil, and the rest is barite.

[0020] Preferably, the plugging agent can form a tight sealing layer in the drilling fluid, with an API filtration loss of ≤15mL, a filtration loss of ≤25mL at 180℃ and 3.5MPa high temperature and pressure, a core plugging rate of ≥85%, a temperature resistance of up to 260℃, a salt resistance of up to 30%, and a reservoir permeability recovery rate of ≥90%. It can quickly form a tight sealing layer in micro-fractured formations, effectively preventing drilling fluid from invading the formation and avoiding downhole accidents such as wellbore instability and leakage. In addition, it can maintain structural integrity and plugging performance even in extreme environments, solving the problem of easy decomposition and plugging failure of plugging agents under high temperature and high salt conditions.

[0021] The beneficial effects of this invention include: 1. By combining nano-silica (low cost, high filling capacity) with graphene oxide (high density, high mechanical strength), a synergistic effect of physical filling and chemical film formation is formed. Nano-silica fills the gaps between cracks, and graphene oxide sheets overlap to form a film, improving the density and mechanical stability of the sealing layer. 2. A composite modification process using silane coupling agents and polymer monomers is adopted. The silane coupling agent reduces the hydroxyl content on the surface of the composite matrix and improves dispersibility; the polymer monomers (such as AM and AMPS) are grafted and copolymerized to introduce temperature- and salt-resistant functional groups, thereby enhancing the compatibility of the plugging agent with the drilling fluid and its ability to withstand extreme working conditions. 3. This plugging agent exhibits excellent adaptability to various operating conditions and can be widely applied to a variety of conventional formations such as shale, sandstone, and carbonate rocks. It is particularly effective in complex and extreme scenarios such as deep, high-temperature, and high-pressure formations (temperature 120-260℃, pressure 70-100MPa), high-salinity formations (salinity 10-30%), and formations with well-developed microfractures (fracture width 5-300nm), filling the gap in the performance of traditional plugging agents under extreme conditions. Furthermore, it boasts excellent compatibility, allowing direct addition to both water-based and oil-based drilling fluid systems at a mass ratio of 0.5-5%. The solution also provides targeted drilling fluid formulations (e.g., water-based fluids containing bentonite and xanthan gum, and oil-based fluids containing emulsifiers and organic clay), further reducing the difficulty of field application and broadening its application scope, effectively meeting the drilling plugging needs of complex formations. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein. The reagents used herein may be commercially available related products, and performance testing standards refer to industry or national standards.

[0024] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0025] The features and performance of this application will be further described in detail below with reference to embodiments: All performance tests for the embodiments and comparative examples in this section were performed in accordance with the following standards: 1. API filtration loss: Tested according to GB / T 16783.1-2025 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids" at normal temperature and pressure; oil-based drilling fluids are tested according to SY / T 5692-2016 "Test Methods for Performance of Oil-based Drilling Fluids". 2. High temperature and high pressure filtration loss: According to SY / T 5621-2018 "Evaluation method for filtration loss reducers for drilling fluids", the test conditions are 180℃, 3.5MPa, constant temperature and pressure for 30min; 3. Core plugging rate: Artificial shale cores were used (porosity 15±2%, permeability 10×10⁻⁶). -3 μm 2 ±2×10 -3 μm 2 (containing 50-300nm microcracks), under constant temperature and pressure of 180℃ and 70MPa for 12h, the change rate of core permeability before and after plugging was calculated (plugging rate = (permeability before plugging - permeability after plugging) / permeability before plugging × 100%). 4. Temperature resistance verification: After the plugging agent is added to the drilling fluid, it is aged at 260℃ for 16 hours. After cooling to room temperature, the API filtration loss and core plugging rate are tested. 5. Salt tolerance verification: Add 30% NaCl (mass fraction) to the drilling fluid, soak for 24 hours, and then test the API filtration loss and core plugging rate; 6. Reservoir permeability recovery rate: In accordance with SY / T 6540-2002 "Evaluation Method of Reservoir Sensitivity Flow Test", natural sandstone cores were used to test the permeability recovery of the cores after treatment with plugging agent; 7. Application compatibility: The amount of plugging agent added is uniformly 2% of the mass of the corresponding drilling fluid system. The stirring rate is 500 r / min, and the stirring time is 30 min before the performance test is carried out.

[0026] Example 1 A drilling plugging agent, comprising: 75.0g of a composite matrix, including nano-silica (particle size 50-150nm, specific surface area 200-300m²). 2The composition includes 66.7g of graphene oxide (sheet thickness 0.8-2nm, lateral dimension 0.5-5μm), with a mass ratio of 8:1; 20.0g of organic modifier (accounting for 20%), including 5.0g of silane coupling agent KH-570 and 15.0g of unsaturated monomer AMPS, with a mass ratio of 1:3; and 5.0g of auxiliary additives (accounting for 5%), including 1.5g (1.5wt%) of dispersant polycarboxylate, 1.0g (1.0wt%) of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 2.5g (2.5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0027] The preparation method includes the following steps: 1. Preparation of composite matrix: 66.7g of nano-silica and 8.3g of graphene oxide were added to 500mL of deionized water and ultrasonically dispersed for 40min at 300W. Then the temperature was raised to 70℃ and the reaction was stirred for 3h. After centrifugation, the matrix was vacuum dried at 70℃ for 18h to obtain the silica-graphene composite matrix. 2. Pretreatment: Add 75.0g of the composite matrix to 200mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 5, and ultrasonically disperse for 25min to obtain a composite matrix dispersion. 3. Organic modification: Add 5.0g KH-570 to the dispersion and hydrolyze at 45℃ for 1.5h; add 15.0g AMPS and 5.0g auxiliary additives, stir at 400r / min; purge with nitrogen, heat to 70℃, add 0.15g ammonium persulfate initiator, and copolymerize for 5h; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 70℃ for 18h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0028] The plugging agent was used in a water-based drilling fluid, which had the following formulation: 6 wt% bentonite, 0.3 wt% sodium carbonate, 3 wt% potassium chloride, 0.5 wt% xanthan gum, 1 wt% filtration reducer, 2 wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss of 8 mL; filtration loss of 15 mL at 180℃ and 3.5MPa high temperature and high pressure; core plugging rate of 92%; API filtration loss of 12 mL and plugging rate of 88% after aging at 260℃; API filtration loss of 10 mL and plugging rate of 90% in a 30% salinity environment; reservoir permeability recovery rate of 93%.

[0029] Example 2: A drilling plugging agent, comprising: 85.0g of a composite matrix, including nano-silica (particle size 20-200nm, specific surface area 100-400m²). 2 The composition includes 79.7g of graphene oxide (sheet thickness 0.8-1nm, lateral dimension 1-5μm) in a mass ratio of 15:1; 12.0g of organic modifier (12%), including 2.4g of silane coupling agent KH-550 and 9.6g of unsaturated monomer AM in a mass ratio of 1:4; and 3.0g of auxiliary additives (3%), including 0.9g (0.9wt%) of dispersant naphthalene sulfonate formaldehyde condensate, 0.6g (0.6wt%) of antioxidant butylated hydroxyanisole, and 1.5g (1.5wt%) of crosslinking agent ethylene glycol dimethacrylate.

[0030] The preparation method includes the following steps: 1. Preparation of composite matrix: Nano-silica and graphene oxide were added to 500 mL of deionized water and ultrasonically dispersed for 30 min at an ultrasonic power of 500 W; then the temperature was raised to 60 °C and the reaction was stirred for 4 h; after centrifugation, the matrix was vacuum dried at 70 °C for 18 h to obtain the silica-graphene composite matrix. 2. Pretreatment: Add the composite matrix to 200 mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 4, and ultrasonically disperse for 20 min to obtain a composite matrix dispersion. 3. Organic modification: Add KH-550 to the dispersion and hydrolyze at 40℃ for 2 hours; add AM and auxiliary additives, stir at 400 r / min; purge with nitrogen for protection, heat to 65℃, add 0.09 g of potassium persulfate initiator, and copolymerize for 6 hours; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 60℃ for 24h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0031] This plugging agent was used in an oil-based drilling fluid. The drilling fluid formulation consisted of: 4 wt% emulsifier, 1.5 wt% organic clay, 3 wt% filtration reducer, 2 wt% plugging agent, and a density adjuster of 1.5 g / cm³. 3 Barite, balance white oil; The results of the tests on the plugging agent are as follows: API filtration loss of 7 mL; filtration loss of 14 mL at 180℃ and 3.5 MPa high temperature and high pressure; core plugging rate of 95%; API filtration loss of 10 mL and plugging rate of 91% after aging at 260℃; API filtration loss of 8 mL and plugging rate of 92% in a 30% salinity environment; reservoir permeability recovery rate of 94%.

[0032] Example 3: A drilling plugging agent, comprising: 60.0g of a composite matrix, including nano-silica (particle size 20-50nm, specific surface area 300-400m²). 2 The composition includes 57.1g of graphene oxide (sheet thickness 0.8-2nm, lateral dimension 0.5-5μm) in a mass ratio of 20:1; 30.0g of organic modifier (30%), including 6.0g of silane coupling agent KH-560 and 24.0g of unsaturated monomer N-vinylpyrrolidone in a mass ratio of 1:4; and 10.0g of auxiliary additives (10%), including 3g (3wt%) of dispersant polycarboxylate, 2.0g (2wt%) of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 5g (5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0033] The preparation method includes the following steps: 1. Preparation of composite matrix: Nano-silica and graphene oxide were added to 500 mL of deionized water and ultrasonically dispersed for 60 min at an ultrasonic power of 400 W; then the temperature was raised to 80 °C and the reaction was stirred for 2 h; after centrifugation, the mixture was vacuum dried at 70 °C for 18 h to obtain the silica-graphene composite matrix. 2. Pretreatment: Add the composite matrix to 200 mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 6, and ultrasonically disperse for 30 min to obtain a composite matrix dispersion. 3. Organic modification: Add KH-560 to the dispersion and hydrolyze at 60℃ for 1h; add N-vinylpyrrolidone and auxiliary additives, stir at 400r / min; purge with nitrogen, heat to 75℃, add 0.48g of initiator azobisisobutyronitrile, and copolymerize for 3h. 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 80℃ for 12h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0034] This plugging agent is used in water-based drilling fluids for well plugging in deep, high-temperature and high-pressure formations (260℃, 100MPa) and high-salt formations (salinity 30%). The water-based drilling fluid formula is: 8wt% bentonite, 0.5wt% sodium carbonate, 5wt% potassium chloride, 1wt% xanthan gum, 2wt% filtration reducer, 5wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss of 9 mL; filtration loss of 16 mL at 180℃ and 3.5 MPa high temperature and high pressure; core plugging rate of 94%; API filtration loss of 13 mL and plugging rate of 90% after aging at 260℃; API filtration loss of 11 mL and plugging rate of 92% in a 30% salinity environment; reservoir permeability recovery rate of 95%.

[0035] Example 4: A drilling plugging agent, comprising: 70.0g of a composite matrix, including nano-silica (particle size 20-100nm, specific surface area 100-200m²). 2 The composition includes 58.3g of graphene oxide (sheet thickness 1-1.5nm, lateral dimension 1-3μm) in a mass ratio of 5:1; 25g of organic modifier (25%), including 6.25g of silane coupling agent KH-570 and 18.75g of unsaturated monomer AMPS in a mass ratio of 1:3; and 5g of auxiliary additives (5%), including 1.5g (1.5wt%) of dispersant polycarboxylate, 1.0g (1.0wt%) of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 2.5g (2.5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0036] The preparation method is the same as in Example 1.

[0037] The plugging agent was used in a water-based drilling fluid, the formulation of which was the same as in Example 1; The results of the tests on the plugging agent are as follows: API filtration loss 10 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 18 mL; core plugging rate 91%; API filtration loss after aging at 260℃ 14 mL, plugging rate 87%; API filtration loss in a 30% salinity environment 12 mL, plugging rate 89%; reservoir permeability recovery rate 92%.

[0038] Comparative Example 1 A drilling plugging agent uses single-component nano-silica as the matrix, with the following composition: nano-silica (particle size 50-150nm, specific surface area 200-300m²). 2 75.0g ( / g); 20.0g (20%) of organic modifier, including 5.0g of silane coupling agent KH-570 and 15.0g of unsaturated monomer AMPS, in a mass ratio of 1:3; 5.0g (5%) of auxiliary additives, including 1.5g (1.5wt%) of dispersant polycarboxylate, 1.0g (1.0wt%) of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 2.5g (2.5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0039] The preparation method includes the following steps: 1. Add nano-silica to 500 mL of deionized water, sonicate at 300 W for 40 min; then heat to 70 °C and stir for 3 h; after centrifugation, dry under vacuum at 70 °C for 18 h to obtain powder; 2. Pretreatment: Add the powder obtained in step 1 to 200 mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 5, and ultrasonically disperse for 25 min to obtain a dispersion. 3. Organic modification: Add 5.0g KH-570 to the dispersion and hydrolyze at 45℃ for 1.5h; add 15.0g AMPS and 5.0g auxiliary additives, stir at 400r / min; purge with nitrogen, heat to 70℃, add 0.15g ammonium persulfate initiator, and copolymerize for 5h; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 70℃ for 18h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0040] The plugging agent was used in a water-based drilling fluid, which had the following formulation: 6 wt% bentonite, 0.3 wt% sodium carbonate, 3 wt% potassium chloride, 0.5 wt% xanthan gum, 1 wt% filtration reducer, 2 wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss 23 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 38 mL; core plugging rate 65%; API filtration loss after aging at 260℃ 35 mL, plugging rate 52%; API filtration loss in a 30% salinity environment 30 mL, plugging rate 58%; reservoir permeability recovery rate 76%.

[0041] Comparative Example 2 A drilling plugging agent uses single graphene oxide as the matrix, and its components are as follows: 75.0g of graphene oxide (sheet thickness 0.8-2nm, lateral size 0.5-5μm); 20.0g of organic modifier (accounting for 20%), including 5.0g of silane coupling agent KH-570 and 15.0g of unsaturated monomer AMPS, in a mass ratio of 1:3; and 5.0g of auxiliary additives (accounting for 5%), including 1.5g (1.5wt%) of dispersant polycarboxylate, 1.0g (1.0wt%) of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 2.5g (2.5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0042] The preparation method includes the following steps: 1. Preparation of composite matrix: Graphene oxide was added to 500 mL of deionized water and ultrasonically dispersed for 40 min at 300 W; then the temperature was raised to 70 °C and the reaction was stirred for 3 h; after centrifugation, the matrix was vacuum dried at 70 °C for 18 h to obtain the graphene matrix; 2. Pretreatment: Add the graphene matrix to 200 mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 5, and ultrasonically disperse for 25 min to obtain a dispersion. 3. Organic modification: Add 5.0g KH-570 to the dispersion and hydrolyze at 45℃ for 1.5h; add 15.0g AMPS and 5.0g auxiliary additives, stir at 400r / min; purge with nitrogen, heat to 70℃, add 0.15g ammonium persulfate initiator, and copolymerize for 5h; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 70℃ for 18h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0043] The plugging agent was used in a water-based drilling fluid, which had the following formulation: 6 wt% bentonite, 0.3 wt% sodium carbonate, 3 wt% potassium chloride, 0.5 wt% xanthan gum, 1 wt% filtration reducer, 2 wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss 15 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 28 mL; core plugging rate 78%; API filtration loss after aging at 260℃ 25 mL, plugging rate 67%; API filtration loss in a 30% salinity environment 22 mL, plugging rate 72%; reservoir permeability recovery rate 81%.

[0044] Comparative Example 3 A drilling plugging agent, differing from Example 1 in that the mass ratio of nano-silica to graphene oxide in the composite matrix is ​​25:1, i.e., the nano-silica in the composite matrix (particle size 50-150nm, specific surface area 200-300m²) 2 The following ingredients were used: 72.1 g of graphene oxide (sheet thickness 0.8-2 nm, lateral dimension 0.5-5 μm), 2.9 g of graphene oxide (sheet thickness 0.8-2 nm, lateral dimension 0.5-5 μm), and the remaining dosages, preparation methods, and drilling fluid formulations were the same as in Example 1.

[0045] The results of the tests on the plugging agent are as follows: API filtration loss 18 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 32 mL; core plugging rate 75%; API filtration loss after aging at 260℃ 28 mL, plugging rate 65%; API filtration loss in a 30% salinity environment 25 mL, plugging rate 70%; reservoir permeability recovery rate 82%.

[0046] Comparative Example 4 A drilling plugging agent, comprising: 75.0g of a composite matrix, including nano-silica (particle size 50-150nm, specific surface area 200-300m²). 2The composition includes 66.7g of graphene oxide (sheet thickness 0.8-2nm, lateral dimension 0.5-5μm), with a mass ratio of 8:1; and 25.0g of auxiliary additives, including 7.5g of dispersant polycarboxylate, 5g of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 12.5g of crosslinking agent N,N'-methylenebisacrylamide.

[0047] The preparation method includes the following steps: 1. Preparation of composite matrix: Nano-silica and graphene oxide were added to 500 mL of deionized water and ultrasonically dispersed for 40 min at an ultrasonic power of 300 W; then the temperature was raised to 70 °C and the reaction was stirred for 3 h; after centrifugation, the matrix was vacuum dried at 70 °C for 18 h to obtain the silica-graphene composite matrix. 2. Pretreatment: Add 75.0g of the composite matrix to 200mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 5, and ultrasonically disperse for 25min to obtain a composite matrix dispersion. 3. Add auxiliary additives to the dispersion, stir at 400 r / min; purge with nitrogen for protection, heat to 70℃, add 0.15 g of initiator ammonium persulfate, and react for 5 h; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 70℃ for 18h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0048] The plugging agent was used in a water-based drilling fluid, which had the following formulation: 6 wt% bentonite, 0.3 wt% sodium carbonate, 3 wt% potassium chloride, 0.5 wt% xanthan gum, 1 wt% filtration reducer, 2 wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss 35 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 55 mL; core plugging rate 43%; API filtration loss after aging at 260℃ 60 mL, plugging rate 31%; nanoparticles completely agglomerate in a 30% salinity environment, with no plugging effect; reservoir permeability recovery rate 62%.

[0049] Comparative Example 5 A drilling plugging agent, differing from Example 1 in that the organic modifier is replaced with a single silane coupling agent, specifically comprising: 75.0g of a composite matrix, including nano-silica (particle size 50-150nm, specific surface area 200-300m²). 2The composition includes 66.7g of graphene oxide (sheet thickness 0.8-2nm, lateral dimension 0.5-5μm) in a mass ratio of 8:1; 20g of organic modifier silane coupling agent KH-570; and 5.0g of auxiliary additives (5%), including 1.5g (1.5wt%) of dispersant polycarboxylate, 1.0g (1.0wt%) of antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, and 2.5g (2.5wt%) of crosslinking agent N,N'-methylenebisacrylamide.

[0050] The preparation method includes the following steps: 1. Preparation of composite matrix: Nano-silica and graphene oxide were added to 500 mL of deionized water and ultrasonically dispersed for 40 min at an ultrasonic power of 300 W; then the temperature was raised to 70 °C and the reaction was stirred for 3 h; after centrifugation, the matrix was vacuum dried at 70 °C for 18 h to obtain the silica-graphene composite matrix. 2. Pretreatment: Add 75.0g of the composite matrix to 200mL of anhydrous ethanol-deionized water mixed solution with a volume ratio of 3:1, adjust the pH to 5, and ultrasonically disperse for 25min to obtain a composite matrix dispersion. 3. Organic modification: Add 20.0g KH-570 to the dispersion, hydrolyze at 45℃ for 1.5h, purge with nitrogen for protection, raise the temperature to 70℃, and keep at that temperature for 5h; 4. Post-processing: After the reaction is complete, wash the product with deionized water until pH=7, centrifuge, dry under vacuum at 70℃ for 18h, grind and pass through a 200-mesh sieve to obtain the drilling plugging agent product.

[0051] The plugging agent was used in a water-based drilling fluid, which had the following formulation: 6 wt% bentonite, 0.3 wt% sodium carbonate, 3 wt% potassium chloride, 0.5 wt% xanthan gum, 1 wt% filtration reducer, 2 wt% plugging agent, and the balance being water. The results of the tests on the plugging agent are as follows: API filtration loss 25 mL; filtration loss at 180℃ and 3.5MPa high temperature and high pressure 42 mL; core plugging rate 70%; API filtration loss after aging at 260℃ 38 mL, plugging rate 52%; API filtration loss in a 30% salinity environment 36 mL, plugging rate 61%; reservoir permeability recovery rate 76%.

[0052] The above provides a detailed description of a drilling plugging agent, its preparation method, and its application. As can be seen from Examples 1-4 and Comparative Examples 1-2, the high filling capacity of nano-silica can bridge microcracks and fill the gaps between graphene oxide sheets. The high density of graphene oxide sheets can overlap to form a barrier film. The two work together to reduce the porosity of the plugging layer by 30-50%. However, single nano-silica cannot form a dense barrier layer, and single graphene oxide is easily deformed due to the lack of particle support between sheets and has a high cost, making it unsuitable for large-scale application.

[0053] In Comparative Example 3, with a composite matrix ratio of 25:1, the core plugging rate was only 75%, the API filtration loss was 18 mL, and the high-temperature, high-pressure filtration loss was 32 mL, all failing to meet the performance indicators for drilling fluid plugging. The reason is that the proportion of graphene oxide was too low, failing to form a continuous, tight plugging film, and the gaps filled by nano-silica could not be effectively covered, resulting in the failure of the synergistic effect.

[0054] In Comparative Example 4, lacking an organic modifier, the core plugging rate was only 45%, API filtration loss was 35 mL, and high-temperature, high-pressure filtration loss was 55 mL. Furthermore, in a 30% salinity environment, the nanoparticles completely agglomerated, showing no plugging effect. In contrast, Examples 1-4, even in a 30% high-salt environment, maintained a core plugging rate ≥89% and API filtration loss ≤12 mL. This demonstrates that the organic modifier can reduce surface energy by forming Si-O-Si covalent bonds with the hydroxyl groups on the composite matrix surface through silane coupling agents. Simultaneously, the unsaturated monomer graft copolymerization introduces salt-resistant functional groups, inhibiting agglomeration. Without modification, the strong interactions of the hydroxyl groups on the nanoparticle surface lead to easy agglomeration and loss of the nano-effect.

[0055] Comparative Example 5, modified with a single silane coupling agent, achieved a core plugging rate of 70%, an API filtration loss of 25 mL, and a high-temperature, high-pressure filtration loss of 42 mL. This significantly differs from Example 1, demonstrating that the silane coupling agent only improves dispersibility and cannot introduce temperature- and salt-resistant functional groups. In contrast, the combination of unsaturated monomers (such as AMPS and NVP) with silane coupling agents can copolymerize to form a cross-linked polymer network, enhancing both dispersion stability and the temperature and salt resistance of the plugging layer. However, if the proportion of silane coupling agent is too low, it cannot sufficiently reduce the hydroxyl content on the composite matrix surface, also leading to decreased dispersibility.

[0056] This invention addresses the limitations of traditional plugging agents in terms of narrow compatibility and difficult field application by utilizing a composite matrix, compound modifiers, and auxiliary additives in a synergistic manner, combined with flexible dosages of 0.5-5% and targeted drilling fluid formulations. Example 3, targeting formations at 260℃, 100MPa high temperature and pressure, and 30% high salinity, achieved a core plugging rate of 94%, maintaining 90% even after aging at 260℃, with a reservoir permeability recovery rate of 95%. In contrast, Comparative Examples 1-2 showed only 52-68% plugging rate after aging at 260℃, with significant performance degradation in high-salt environments. This demonstrates that the invention effectively fills the performance gap of traditional plugging agents under extreme conditions. Examples 1, 2, and 4 all achieved API filtration loss ≤10mL and core plugging rate ≥91%. Furthermore, the plugging agent can be directly added to two mainstream drilling fluid systems at a dosage of 0.5-5%, and the customized formulation further reduces compatibility difficulties, overcoming the limitation of traditional plugging agents being only applicable to a single drilling fluid or a single formation. The reservoir permeability recovery rates of Examples 1-4 were all ≥92%, which was much higher than that of the comparative examples, proving that the plugging agent had little pollution to the reservoir; and through the synergistic effect of antioxidants and dispersants, the performance was stable under long-term storage and extreme working conditions, which met the environmental protection and safety requirements of oil drilling.

[0057] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drilling plugging agent, comprising a composite matrix, an organic modifier, and auxiliary additives, wherein the components, by mass percentage, are: composite matrix 60-85%, organic modifier 10-30%, and auxiliary additives 1-10%, characterized in that, The composite matrix is ​​a mixture of nano-silica and graphene oxide in a mass ratio of 5-20:1; the organic modifier is a compound system of silane coupling agent and unsaturated monomer, wherein the mass ratio of silane coupling agent to unsaturated monomer is 1:2-5; the auxiliary additives include 0.3-3wt% dispersant, 0.2-2wt% antioxidant, and 0.5-5wt% crosslinking agent.

2. The drilling plugging agent according to claim 1, characterized in that, The nano-silica has a particle size of 20-200 nm and a specific surface area of ​​100-400 m². 2 / g; the thickness of the graphene oxide sheets is 0.8-2nm, and the lateral dimension is 0.5-5μm.

3. The drilling plugging agent according to claim 1, characterized in that, The silane coupling agent is selected from one or more of KH-570, KH-550, and KH-560; the unsaturated monomer is selected from one or more of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and N-vinylpyrrolidone.

4. The drilling plugging agent according to claim 1, characterized in that, The dispersant is one of polycarboxylate salts and naphthalene sulfonate formaldehyde condensate; the antioxidant is a hindered phenolic antioxidant; and the crosslinking agent is one of N,N'-methylenebisacrylamide and ethylene glycol dimethacrylate.

5. A method for preparing a drilling plugging agent as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of composite matrix: Nano-silica and graphene oxide are added to deionized water at a mass ratio of 5-20:1, ultrasonically dispersed for 30-60 min, and then stirred at 60-80℃ for 2-4 h. After centrifugation and vacuum drying, silica-graphene composite matrix is ​​obtained. (2) Pretreatment: Add the composite matrix obtained in step (1) to a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 3:1, adjust the pH to 4-6, and ultrasonically disperse for 20-30 min to obtain a composite matrix dispersion. (3) Organic modification: Add organic modifier to the composite matrix dispersion, wherein the amount of silane coupling agent is 2-17% of the mass of the composite matrix and the amount of unsaturated monomer is 8-42% of the mass of the composite matrix. After stirring evenly, add auxiliary additives, heat to 60-80℃ under nitrogen protection, add 0.5-2% of the mass of unsaturated monomer initiator, and react for 4-8 hours; (4) Post-processing: After the reaction is completed, the product is washed until neutral, centrifuged, and vacuum dried at 60-80℃ for 12-24h. Then it is ground through a 200-mesh sieve to obtain a silicon oxide-graphene composite organic modified drilling plugging agent.

6. The preparation method according to claim 5, characterized in that, The initiator in step (3) is selected from one of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile; the stirring rate of the reaction is 300-500 r / min.

7. The preparation method according to claim 5, characterized in that, The hydrolysis time of the silane coupling agent in step (3) is 1-2 h, and the hydrolysis temperature is 40-60 °C; the copolymerization reaction temperature of the unsaturated monomer is 65-75 °C, and the reaction time is 3-6 h.

8. An application of a drilling plugging agent as described in any one of claims 1-4, characterized in that, The plugging agent is added to the drilling fluid system at 0.5-5% of the drilling fluid mass, stirred evenly, and then used for drilling operations; the drilling fluid system includes water-based drilling fluid and oil-based drilling fluid.

9. The application according to claim 8, characterized in that, When the plugging agent is used in water-based drilling fluids, the fluid formulation includes: 4-8 wt% bentonite, 0.2-0.5 wt% sodium carbonate, 2-5 wt% potassium chloride, 0.3-1 wt% xanthan gum, 0.5-2 wt% filtration reducer, 0.5-5 wt% plugging agent, and the balance being water; when used in oil-based drilling fluids, the formulation includes: 3-5 wt% emulsifier, 1-2 wt% organic clay, 2-4 wt% filtration reducer, 0.5-5 wt% plugging agent, and a density adjusted to 1.2-1.8 g / cm³. 3 The remainder is white oil, and the rest is barite.

10. The application according to claim 8, characterized in that, The plugging agent can form a tight plugging layer in the drilling fluid, with an API filtration loss of ≤15mL, a filtration loss of ≤25mL at 180℃ and 3.5MPa high temperature and high pressure, a core plugging rate of ≥85%, a temperature resistance of up to 260℃, a salt resistance of up to 30%, and a reservoir permeability recovery rate of ≥90%.