Preparation method and application of composite drilling-while-drilling leak-proof agent

Abstract

The present invention relates to a preparation method and application of a composite while-drilling leak-proof agent, and belongs to the field of oil drilling engineering technology. The composite while-drilling leak-proof agent is prepared from the following components in percentage by mass: 20-45% nano-composite particles, 15-35% multi-stage fiber-reinforced network materials, 10-20% intelligent response plugging agent, 5-10% high-temperature resistant additive, 1-5% dispersant, and the balance is deionized water, and the total content of each component is 100%. The composite while-drilling leak-proof agent provided by the present invention introduces a core-shell structured thermosensitive resin to realize a three-dimensional synergistic mechanism of "nano-composite particle filling-multi-stage fiber network bridging-intelligent response curing", thereby realizing efficient and environmentally friendly plugging of ultra-high temperature and high-pressure formations. The success rate of single plugging is increased from 45% to 92%, and the average operation time is shortened by 60%, providing an efficient solution for deep and ultra-deep drilling.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a composite leak-proofing agent while drilling, and specifically provides a composite leak-proofing agent while drilling suitable for high-temperature and high-pressure formations and a preparation method thereof, belonging to the technical field of petroleum drilling engineering. Background Art

[0002] Lost circulation is a major technical challenge in oil drilling. Statistics show that the incidence of lost circulation in global drilling operations is as high as 20%-25%. Drilling in deep (4500-6000m) and ultra-deep (>6000m) formations, characterized by high temperatures (150-250°C), high pressures (80-150MPa), and complex fracture networks (with nano- and millimeter-scale fractures) presents significant challenges for plugging materials. Conventional bridging materials thermally degrade at high temperatures, resulting in a loss of plugging strength. These materials then form stable structures under the influence of circulating drilling fluid. This lack of evaluation and quantitative characterization methods has resulted in a low success rate in field applications.

[0003] Chinese patent document CN117343699A discloses a gel composite fiber for plugging lost-while-drilling (LWD) leaks. It consists of 30-50 parts of ultrafine plant fibers, a composite wetting agent (0.5-4 parts), a flow pattern modifier (0.5-4 parts), a liquid sand consolidator (1-5 parts), calcium carbonate (20-40 parts), and a composite special gel (10-30 parts). Its core design leverages the adhesion between the three-dimensional network structure of the plant fibers and the gel particles, achieving multi-stage sealing of cracks. Experimental data shows that this material reduces fluid loss by 20% compared to traditional materials in a 40-60 mesh sand bed. At a pressure of 3.5 MPa, the plugging depth reaches 1 cm, and the sand bed exhibits no tendency to loosen. It is suitable for leaky formations with temperatures up to 150°C. Chinese patent document CN116445138A proposes a composite plugging agent composed of diatomaceous earth (40-60 parts), hydrophobic nano-silica (10-20 parts), oleophilic flake molybdenum disulfide (10-15 parts), and oleophilic calcium carbonate (15-30 parts). Its innovation lies in the synergistic effect of the nanocomposite particles and the flake materials: the hydrophobic nano-silica (particle size 20-50 nm) fills the pores, while the flake molybdenum disulfide (thickness 1-3 μm) forms a lubricating film on the crack surface, reducing fluid permeation. Laboratory experiments have shown that this material can increase the dynamic-to-plastic ratio of drilling fluid by 30% and reduce fluid loss to less than 5 mL. Chinese patent document CN117264170A describes a self-healing gel plugging material based on a polyurethane prepolymer. This material forms a dynamic network structure through a cross-linking reaction between isocyanate and polyol. When the material is damaged by shear or pressure, the active groups at the fractures can re-crosslink, enabling self-healing of the cracks. Experiments show that this material achieves an 85% crack repair rate at 120°C and 10 MPa, and the compressive strength recovers to 90% of its original value after repair. Chinese patent document CN202410185695A proposes a method for quantitatively evaluating the degree of high-temperature, high-pressure melting based on grayscale analysis. This method uses a visualization chamber to capture real-time images of the melting process of temperature-sensitive resins (such as ABS and LDPF) in an aqueous environment at 150°C and 20 MPa. Chinese patent document CN202410186221A develops a composite system of temperature-sensitive resin and bridging particles, quantifying the degree of melting by measuring the change in the particle boundary area ratio. Experiments show that as the temperature increases from 120°C to 150°C, the resin particle boundary area ratio decreases from 70% to 30%, corresponding to the transition from primary to advanced melting. Application of this system in the Keshen 905 well in the Tarim Oilfield (7,850 m deep, 165°C) increased the pressure bearing capacity of the plugging layer from 6 MPa to 15 MPa.

[0004] However, while the aforementioned patents have made progress in material design and evaluation methods, they still face challenges such as a lack of clarity regarding the multi-factor coupling mechanism and insufficient exploration of multi-material composite mechanisms. Furthermore, for complex geological conditions such as high temperature, high pressure, and high salinity in deep and ultra-deep formations, there is a lack of effective, leak-proof materials for drilling. Therefore, developing an environmentally friendly leak-proof agent that combines the synergistic effects of "nano-scale filling, micro-scale bridging, and high-temperature curing enhancement" has become a technical challenge that urgently needs to be overcome in deep and ultra-deep drilling. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, especially the problems of poor stability, poor gradation and reservoir pollution risk of existing plugging materials in harsh environments of high temperature and high pressure such as deep and ultra-deep layers, the present invention provides a preparation method and application of a composite while-drilling leak-proof agent.

[0006] The composite leak-proof agent while drilling of the present invention can realize controllable curing and efficient plugging of the resin base material through the synergistic mechanism of "nano filling-temperature sensitive curing-multi-stage bridging" under high temperature and high pressure conditions: the core-shell structure design of the nano-composite particles enables the leak-proof agent to maintain good fluidity during the drilling process, avoiding the risk of pipe sticking due to premature curing, while reducing the circulation resistance of the drilling fluid and improving the pumping efficiency; the synergistic effect of the multi-stage fiber reinforced network material and the intelligent response plugging agent ensures that the leak-proof slurry forms a high-strength consolidated body in the leaking layer, and at 220 After aging for 168 hours at high temperature of ℃, the strength retention rate is >85%, and the stability is more than 2 times that of traditional materials. By adjusting the proportion of temperature-sensitive resin and the amount of intelligent response plugging agent, the curing time and plugging strength can be flexibly controlled to adapt to the plugging needs of different formation temperatures (120-220℃) and crack sizes (0.01mm-3.0mm), significantly improving construction safety and plugging success rate. At the same time, biodegradable materials account for more than 40%, effectively reducing the risk of reservoir pollution and meeting the efficient and environmentally friendly operation requirements of deep and ultra-deep drilling.

[0007] The technical solutions of the present invention are as follows:

[0008] A composite leak-proofing agent while drilling, characterized in that it is prepared from the following components in percentage by mass: 20-45% nanocomposite particles, 15-35% multi-stage fiber-reinforced network material, 10-20% intelligent response plugging agent, 5-10% high-temperature resistant additive, 1-5% dispersant, and the balance being deionized water, with the total content of each component being 100%;

[0009] The nanocomposite particles are a combination of nano-silicon dioxide and a temperature-sensitive resin; the temperature-sensitive resin is one or a combination of two or more of melamine-formaldehyde resin, phenolic resin, urea-formaldehyde resin, and polyethersulfone resin;

[0010] The multi-level fiber-reinforced network material is a combination of carbon fiber, basalt fiber and plant fiber;

[0011] The smart response plugging agent is a combination of pH-responsive polymer microspheres and temperature-responsive polymer microspheres; the pH-responsive polymer microspheres are a combination of one or two of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; the temperature-responsive polymer microspheres are a combination of one or two of poly (N-isopropylacrylamide) microspheres and temperature-sensitive chitosan microspheres;

[0012] The high temperature resistant additive is one or a combination of organosilicon modified montmorillonite and nano titanium dioxide;

[0013] The dispersant is a combination of a small molecule anionic dispersant and a nonionic polymer dispersant; the small molecule anionic dispersant is one or a combination of two or more of polycarboxylic acid ammonium salt, sodium lignin sulfonate, and sodium dodecylbenzene sulfonate; the nonionic polymer dispersant is one or a combination of two or more of sodium polyacrylate, polyvinyl pyrrolidone, and hydroxypropyl methylcellulose.

[0014] Preferably, according to the present invention, the composite leak-proof agent while drilling is prepared from the following components in percentage by mass: 25-40% nano-composite particles, 20-25% multi-stage fiber-reinforced network material, 10-15% intelligent response plugging agent, 5-8% high temperature resistant additive, 3-5% dispersant, and the balance is deionized water, and the total content of each component is 100%.

[0015] Preferably, according to the present invention, the composite leak-while-drilling preventive agent is prepared from the following components in the following mass percentages: 40% nano-composite particles, 25% multi-stage fiber-reinforced network material, 15% intelligent response plugging agent, 5% high-temperature resistant additive, 3% dispersant, and the balance is deionized water, and the total content of each component is 100%.

[0016] The nanocomposite particles of the present invention have the synergistic effect of nano-scale filling and high-temperature curing, and also have good heat and high-pressure resistance.

[0017] According to the preferred embodiment of the present invention, the mass ratio of the nano-silica and the temperature-sensitive resin is (1-3): (2-5);

[0018] The nano-silica is one or a combination of two or more of hydrophilic nano-silica, hydrophobic nano-silica, and surface-modified nano-silica;

[0019] The hydrophilic nano-silica is nano-silica with a hydroxylated surface.

[0020] The hydrophobic nano-silica is organosilane-modified nano-silica;

[0021] The surface-modified nano-silica is nano-silica modified by a silane coupling agent, nano-silica modified by a titanate coupling agent, or nano-silica modified by an aluminate coupling agent;

[0022] The mass ratio of the carbon fiber, basalt fiber and plant fiber is (2-4): (1-3): (1-2);

[0023] The carbon fiber is one or a combination of two or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, and viscose-based carbon fiber;

[0024] The basalt fiber is one of continuous basalt fiber and chopped basalt fiber, or a combination of the two;

[0025] The plant fiber is one or a combination of two or more of cotton fiber, sisal fiber and wood fiber;

[0026] The mass ratio of the pH-responsive polymer microspheres to the temperature-responsive polymer microspheres is (1-2):1;

[0027] The mass ratio of the organosilicon-modified montmorillonite and nano-titanium dioxide is (1-4): (1-3);

[0028] The organosilicon-modified montmorillonite is one or a combination of methyltrimethoxysilane-modified montmorillonite and phenyltriethoxysilane-modified montmorillonite;

[0029] The mass ratio of the small molecule anionic dispersant to the nonionic polymer dispersant is (1-3): (1-5).

[0030] According to the preferred embodiment of the present invention, the nanocomposite particles are a combination of silane coupling agent modified nano-silica and polyethersulfone resin, and the mass ratio of silane coupling agent modified nano-silica to polyethersulfone resin is 2:3 or 1:4;

[0031] The multi-stage fiber-reinforced network material is a combination of polyacrylonitrile-based carbon fibers, chopped basalt fibers, and cotton fibers, wherein the mass ratio of the polyacrylonitrile-based carbon fibers, the chopped basalt fibers, and the cotton fibers is 3:2:1, and the fiber lengths are 2-5 mm, 1-3 mm, and 0.5-2 mm, respectively;

[0032] The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres and poly (N-isopropylacrylamide) microspheres, with a mass ratio of 2:1. The acrylic acid / acrylamide copolymer microspheres have a swelling rate of ≥500% when the pH is greater than 9, a response threshold pH of 9±0.5, and a volume shrinkage of ≤10% when the temperature is greater than 180°C.

[0033] The high temperature resistant additive is a combination of methyltrimethoxysilane modified montmorillonite and nano-titanium dioxide, wherein the mass ratio of methyltrimethoxysilane modified montmorillonite to nano-titanium dioxide is 3:1 or 4:3; the interlayer spacing is ≥2.5nm, and the thermal weight loss rate (220°C) is <5%;

[0034] The dispersant is a combination of sodium dodecylbenzene sulfonate and sodium polyacrylate, and the mass ratio of sodium dodecylbenzene sulfonate to sodium polyacrylate is 2:3, which can ensure that the dispersion uniformity error of each component in the drilling fluid is ≤5%.

[0035] The composite raw material of the present invention achieves the synergistic effect of "nanoscale filling-fiber network bridging-intelligent response curing" through multi-component ratio optimization, which makes the sealing efficiency of the leak-proof agent under high temperature and high pressure more than 40% compared with traditional materials, and has excellent reservoir adaptability and environmental protection characteristics.

[0036] The preparation method of the composite leak-while-drilling agent comprises the following steps:

[0037] (1) Preparation of nanocomposite particles: Nano-silica and thermosensitive resin are weighed according to the ratio, added to a high-speed shearing machine and mixed evenly, and spray-dried to form a core-shell structure to obtain nanocomposite particles;

[0038] (2) Construction of multi-level fiber-reinforced network materials: Carbon fibers, basalt fibers, and plant fibers are dispersed in deionized water according to the ratio to obtain a fiber dispersion; the fiber dispersion is then subjected to ultrasonic treatment and freeze-dried to form a three-dimensional porous skeleton to obtain a multi-level fiber-reinforced network material;

[0039] (3) Synthesis of smart response plugging agent: pH-responsive polymer microspheres and temperature-responsive polymer microspheres are mixed evenly according to the ratio to obtain smart response plugging agent;

[0040] (4) According to the proportion, nanocomposite particles, multi-level fiber reinforced network material, intelligent response plugging agent, high temperature resistant additive, dispersant and deionized water are added into a planetary mixer and mixed evenly, and the water content is controlled to be ≤5% to obtain a composite while-drilling leak-proof agent.

[0041] Preferably, according to the present invention, in step (1), the speed of the high-speed shearing machine is 10,000 to 15,000 rpm, the mixing time is 30 to 60 minutes, the spray drying air inlet temperature is 200 to 220° C., and the atomization pressure is 0.3 to 0.5 MPa.

[0042] Further preferably, the speed of the high-speed shearing machine is 12,000 rpm, the inlet air temperature of the spray drying is 210° C., and core-shell particles with an average particle size of 100-200 nm are obtained, and the nano-silica coverage rate is ≥95%.

[0043] Preferably, according to the present invention, in step (2), the mass concentration of the fiber dispersion is 5-10%, the ultrasonic treatment power is 500-800 W, the time is 10-20 minutes, the freeze-drying temperature is -50 to -40°C, the vacuum drying pressure is <10 Pa, and the time is 24-48 hours.

[0044] More preferably, the ultrasonic treatment power is 600W, the freeze-drying temperature is -50°C, a fiber skeleton with a porosity of 50-60% is formed, and the fiber interlacing density error is ≤5%.

[0045] Preferably, according to the present invention, in step (4), the planetary mixer has a rotation speed of 500-800 rpm, a mixing time of 20-40 minutes, and a particle size distribution D90 of the composite while-drilling leak-proofing agent is ≤500 μm.

[0046] Further preferably, the rotation speed is 600 rpm and the mixing time is 30 minutes, ensuring that the dispersion uniformity error of each component is ≤3%.

[0047] Preferably, according to the present invention, in steps (1) to (4), the conductivity of the deionized water used is ≤10 μS / cm, and the purity of the raw materials is ≥98%, so as to ensure the stability of the reaction system.

[0048] According to the present invention, the composite leak-proofing agent while drilling is used for leak-proofing while drilling or slugging.

[0049] According to the preferred embodiment of the present invention, the application method is as follows:

[0050] Direct injection while drilling: When the drilling fluid loss rate is greater than 5m³ / h, a leak-proof slurry with a density of 1.8-2.2g / cm³ is prepared at a ratio of 1:(2-3) of composite leak-proof agent while drilling to water. The leak-proof slurry is then pumped through the drill pipe at a rate of 2-3m³ / min. Nanocomposite particles fill micropores and a multi-stage fiber-reinforced network bridges large cracks, achieving rapid plugging.

[0051] Alternatively, a collaborative plugging process is used: for cracks with a width greater than 2mm, a leak-proof slurry with a density of 1.8-2.2g / cm³ is prepared at a ratio of composite leak-proof agent while drilling to water of 1:(2-3). Inert bridging particles (such as corn cobs) with a particle size of 2-5mm are then injected to form a skeleton, followed by the leak-proof slurry. The bridging particles are bonded by thermosensitive resin curing at high temperature (>180°C) to form an overall plugging layer with a compressive strength of ≥15MPa.

[0052] The technical features and beneficial effects of the present invention are as follows:

[0053] The composite leak-while-drilling (LWD) sealant provided by this invention incorporates a core-shell thermosensitive resin, achieving a three-dimensional synergistic mechanism of "nanocomposite particle filling, multi-level fiber network bridging, and intelligent responsive curing," enabling efficient and environmentally friendly plugging of ultra-high-temperature, high-pressure formations. This technology has completed field trials in the Moxi block of the Sichuan Basin (well depth 6,500m, temperature 150°C), increasing the single-shot plugging success rate from 45% to 92% and reducing average operation time by 60%, providing a highly effective solution for deep and ultra-deep drilling.

[0054] 2. The composite leak-down preventer provided by the present invention has a multi-stage coordinated plugging mechanism, in which nano-silica fills nano-scale pores (<100nm), and a multi-stage fiber network quickly bridges millimeter-scale cracks (1~3mm). The intelligent response plugging agent dynamically adjusts the plugging structure in response to the formation environment, achieving full coverage of 0.01~3.0mm cracks. The leakage can be reduced to below 0.5mL / min, which is 40% higher than the plugging efficiency of traditional materials.

[0055] 3. The composite drilling-while-drilling leak-proof agent provided by the present invention has adaptability to ultra-high temperature and high pressure. The temperature-sensitive resin and silicone-modified montmorillonite therein work synergistically, so that after aging the leak-proof agent at 220°C and 100MPa for 168 hours, the compressive strength retention rate is greater than 85% and the mass loss rate is less than 3%, breaking through the bottleneck of traditional materials failing at temperatures above 200°C.

[0056] 4. The composite leak-proofing agent provided by the present invention can precisely control the curing time. By adjusting the proportion of temperature-sensitive resin and the amount of intelligent response plugging agent, the curing time can be flexibly controlled (2 to 6 hours), ensuring that the leak-proof slurry maintains a low viscosity (≤50 mPa·s) during the pumping process, avoiding the risk of drill sticking, and quickly forming a high-strength consolidated body at the formation temperature.

[0057] 5. The composite leak-down preventer provided by the present invention has the advantages of environmental protection and reservoir protection. The biodegradable materials such as plant fibers and pH-responsive microspheres account for more than 40%, the heavy metal content is less than 0.1ppm, and the biodegradation rate is ≥65%. It meets the green drilling standards and significantly reduces the risk of reservoir pollution.

[0058] 6. The composite leak-proofing agent provided by the present invention is efficient and convenient to construct. It can take effect as soon as it is injected while drilling, without stopping drilling to adjust the formula. The plugging operation time of a single well is shortened by more than 50%. Combined with the gradient pumping process, it can achieve one-time efficient plugging of complex fractured formations, greatly reducing operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Thermogravimetric analysis diagrams of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres;

[0060] In the figure, A is acrylic acid / acrylamide copolymer microspheres, and B is methacrylic acid / maleic anhydride copolymer microspheres.

[0061] Figure 2 Thermogravimetric analysis diagrams of poly (N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres;

[0062] In the figure, A is poly (N-isopropylacrylamide) microspheres and B is temperature-sensitive chitosan microspheres.

[0063] Figure 3 IR spectra of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres;

[0064] In the figure, A is acrylic acid / acrylamide copolymer microspheres, and B is methacrylic acid / maleic anhydride copolymer microspheres.

[0065] Figure 4 The infrared spectra of poly (N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres are shown in Figure 1.

[0066] In the figure, A is poly (N-isopropylacrylamide) microspheres and B is temperature-sensitive chitosan microspheres.

[0067] Figure 5 This is a physical photo of the composite while-drilling leak-proof agent described in Example 1. DETAILED DESCRIPTION

[0068] The present invention will be further described below with reference to specific examples, but is not limited thereto. The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all prior art unless otherwise specified.

[0069] In the present invention, pH-responsive polymer microspheres are prepared according to the following method:

[0070] Mix liquid paraffin and cyclohexane, add emulsifiers Span80 and Tween80, stir evenly at 300-500 r / min, then heat to 45-55°C to obtain the oil phase, and keep constant temperature for later use;

[0071] The volume ratio of liquid paraffin to cyclohexane is 4:1; the amount of Span80 added is 0.82% of the mass of liquid paraffin; the mass ratio of Span80 to Tween80 is 2:1;

[0072] The pH-responsive monomer, comonomer, and cross-linker are sequentially dissolved in deionized water, and the pH is adjusted to neutral with NaOH solution. Then, the initiator solution is added and stirred continuously until completely dissolved to obtain an aqueous phase.

[0073] The mass ratio of the pH-responsive monomer to the comonomer is (3-5): (5-7); the initiator is a mixture of ammonium persulfate and sodium bisulfite, and the addition amount is 0.5-2% of the total mass of the pH-responsive monomer and the comonomer; the cross-linker is N,N'-methylenebisacrylamide (MBA), and the addition amount is 0.1-1% of the total mass of the pH-responsive monomer and the comonomer;

[0074] The aqueous phase is slowly dripped into the oil phase at a dripping rate of 1-2 mL / min, while high-speed stirring is started and maintained at 800-1000 r / min to form a stable emulsion system; after the emulsion is formed, the temperature is raised to 55-65°C and kept warm for 3-5 hours. The stirring rate is always maintained during the reaction to ensure that the reaction proceeds fully; after the reaction is completed, ethanol or acetone is added to break the emulsion, and microspheres are obtained by centrifugation. The microspheres are then washed alternately with deionized water and ethanol for 3-5 times to remove residual emulsifier and unreacted monomers, and finally vacuum dried or freeze-dried to obtain pH-responsive polymer microspheres.

[0075] According to this method, acrylic acid / acrylamide copolymer microspheres are prepared when acrylic acid is used as the pH-responsive monomer and acrylamide is used as the comonomer. Methacrylic acid / maleic anhydride copolymer microspheres are prepared when maleic anhydride is used as the pH-responsive monomer and 2-acrylamido-2-methylpropanesulfonic acid is used as the comonomer.

[0076] Poly (N-isopropylacrylamide) microspheres with temperature-sensitive properties were prepared as follows:

[0077] First, the temperature-responsive monomer N-isopropylacrylamide (NIPAM) and the cross-linker N,N'-methylenebisacrylamide (MBA) were dissolved in deionized water to prepare a monomer solution with a mass fraction of 10-20%. After stirring evenly, the initiator solution was added and the mixture was reacted in a constant temperature water bath at 40-60°C for 3-6 hours. After the reaction was completed, the mixture was cooled to room temperature and the microspheres were collected by centrifugation. The microspheres were washed alternately with deionized water and ethanol for 3-5 times and finally dried in a vacuum at 40-50°C to constant weight to obtain poly (N-isopropylacrylamide) microspheres with temperature-sensitive properties.

[0078] Among them, the addition amount of N,N'-methylenebisacrylamide (MBA) is 0.5~2% of the mass of N-isopropylacrylamide (NIPAM); the initiator is a combination of ammonium sulfate (APS) and sodium bisulfite, and the addition amount is 0.5~1% of the mass of N-isopropylacrylamide (NIPAM).

[0079] Thermosensitive chitosan microspheres were prepared as follows:

[0080] Span80 was first added to liquid paraffin and stirred evenly. Then, chitosan acetic acid solution was slowly added dropwise to form a W / O emulsion under high-speed stirring at 800-1200 r / min. Glutaraldehyde solution was then added dropwise to allow cross-linking reaction to occur at room temperature for 2-4 hours. After the reaction, anhydrous ethanol was added to break the emulsion, and the microspheres were collected by centrifugation. The microspheres were then washed alternately with anhydrous ethanol and deionized water for 3-5 times, and finally dried in vacuo at 40-50°C to constant weight to obtain temperature-sensitive chitosan microspheres with amino groups on the surface.

[0081] Among them, the mass concentration of chitosan acetate solution is 1~3%, and the dosage is 10~20% of the volume of liquid paraffin; the volume concentration of glutaraldehyde solution is 2~5%, and the dosage is 10~30% of the volume of liquid paraffin; and the volume concentration of Span80 is 1~3% of the volume of liquid paraffin.

[0082] The thermogravimetric analysis of the above acrylic acid / acrylamide copolymer microspheres, methacrylic acid / maleic anhydride copolymer microspheres, poly N-isopropylacrylamide microspheres and temperature-sensitive chitosan microspheres is shown in FIG. Figures 1 and 2 As shown, the infrared spectrum is as Figures 3 and 4 shown.

[0083] Depend on Figures 1 to 4 It can be seen that pH-responsive polymer microspheres (acrylic acid / acrylamide copolymer microspheres, methacrylic acid / maleic anhydride copolymer microspheres) and temperature-responsive polymer microspheres (poly (N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres) were successfully prepared.

[0084] Example 1

[0085] A composite leak-proofing agent while drilling is prepared from the following components in percentage by mass:

[0086] Nanocomposite particles 40%, multi-level fiber reinforced network material 25%, intelligent response plugging agent 15%, high temperature resistant additive 5%, dispersant 3%, the balance is deionized water, the total content of each component is 100%;

[0087] The nanocomposite particles are a combination of silane coupling agent modified nano-silica and polyethersulfone resin, with the mass ratio of silane coupling agent modified nano-silica to polyethersulfone resin being 2:3;

[0088] The multi-stage fiber-reinforced network material is a combination of polyacrylonitrile-based carbon fibers, chopped basalt fibers, and cotton fibers, wherein the mass ratio of the polyacrylonitrile-based carbon fibers, the chopped basalt fibers, and the cotton fibers is 3:2:1, and the fiber lengths are 3 mm, 2 mm, and 1 mm, respectively;

[0089] The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres (pH responsive) and poly (N-isopropylacrylamide) microspheres (temperature responsive), with the mass ratio of acrylic acid / acrylamide copolymer microspheres to poly (N-isopropylacrylamide) microspheres being 2:1.

[0090] The high temperature resistant additive is a combination of methyltrimethoxysilane modified montmorillonite and nano-titanium dioxide, and the mass ratio of methyltrimethoxysilane modified montmorillonite to nano-titanium dioxide is 3:1;

[0091] The dispersant is a combination of sodium dodecylbenzene sulfonate and sodium polyacrylate, and the mass ratio of sodium dodecylbenzene sulfonate to sodium polyacrylate is 2:3.

[0092] The preparation method of the composite leak-while-drilling agent comprises the following steps:

[0093] (1) Preparation of nanocomposite particles: Surface-modified nanosilica and polyethersulfone resin were weighed according to the ratio, added to a high-speed shearing machine, mixed at 12,000 rpm for 45 minutes, and spray-dried to form a core-shell structure to obtain nanocomposite particles;

[0094] The spray drying parameters are as follows: inlet air temperature 210°C, atomization pressure 0.4 MPa;

[0095] (2) Construction of multi-level fiber-reinforced network material: Carbon fiber, basalt fiber and plant fiber are dispersed in deionized water according to a certain ratio to obtain a fiber dispersion with a mass concentration of 8%. The fiber dispersion is then subjected to ultrasonic treatment and freeze-dried to form a three-dimensional porous skeleton to obtain a multi-level fiber-reinforced network material.

[0096] The parameters for ultrasonic treatment were: power 600W, time 15 minutes; the parameters for freeze drying were: temperature -50°C, pressure <10Pa, time 36 hours;

[0097] (3) Synthesis of smart response plugging agent: pH-responsive polymer microspheres and temperature-responsive polymer microspheres are mixed in a certain ratio to obtain smart response plugging agent;

[0098] (4) According to the proportion, nanocomposite particles, multi-level fiber reinforced network material, intelligent response plugging agent, high temperature resistant additive, dispersant and deionized water were added to a planetary mixer, mixed at 600 rpm for 30 minutes, and dried to a moisture content of ≤5% to obtain a composite while-drilling leak-proof agent, which was recorded as sample A1.

[0099] The actual photo of the composite leak-proof agent while drilling prepared in this embodiment is as follows: Figure 5 shown.

[0100] Depend on Figure 5It can be seen that the composite leak-proofing agent while drilling described in this embodiment was successfully prepared and was in the form of white powder.

[0101] Example 2

[0102] A composite leak-proofing agent while drilling is prepared from the following components in mass fractions:

[0103] Nanocomposite particles 30%, multi-level fiber reinforced network material 30%, intelligent response plugging agent 20%, high temperature resistant additive 8%, dispersant 4%, the balance is deionized water, the total content of each component is 100%;

[0104] The nanocomposite particles are a combination of organosilane-modified nanosilica and phenolic resin, with the mass ratio of organosilane-modified nanosilica to phenolic resin being 1:2.

[0105] The multi-stage fiber-reinforced network material is a combination of pitch-based carbon fibers, continuous basalt fibers, and sisal fibers, wherein the mass ratio of the pitch-based carbon fibers, continuous basalt fibers, and sisal fibers is 2:3:2, and the fiber lengths are 4 mm, 2.5 mm, and 1.5 mm, respectively;

[0106] The smart response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH responsive) and thermosensitive chitosan microspheres (temperature responsive), with the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres being 1:1;

[0107] The high temperature resistant additive is a combination of phenyltriethoxysilane modified montmorillonite and nano titanium dioxide, and the mass ratio of phenyltriethoxysilane modified montmorillonite to nano titanium dioxide is 2:1;

[0108] The dispersant is a combination of sodium lignin sulfonate and hydroxypropyl methylcellulose, and the mass ratio of sodium lignin sulfonate to hydroxypropyl methylcellulose is 1:2.

[0109] The preparation method of the composite leak-while-drilling preventer is as described in Example 1, and is recorded as Sample A2.

[0110] Example 3

[0111] A composite leak-proofing agent while drilling is prepared from the following components in mass fractions:

[0112] Nanocomposite particles 45%, multi-level fiber reinforced network material 20%, intelligent response plugging agent 10%, high temperature resistant additive 10%, dispersant 2%, the balance is deionized water, the total content of each component is 100%;

[0113] The nanocomposite particles are a combination of surface hydroxylated nano-silica and melamine-formaldehyde resin, wherein the mass ratio of the surface hydroxylated nano-silica to the melamine-formaldehyde resin is 3:4;

[0114] The multi-stage fiber-reinforced network material is a combination of viscose-based carbon fibers, chopped basalt fibers, and wood fibers, wherein the mass ratio of the viscose-based carbon fibers, the chopped basalt fibers, and the wood fibers is 4:1:1, and the fiber lengths are 2 mm, 1.5 mm, and 1 mm, respectively;

[0115] The intelligent response plugging agent is acrylic acid / acrylamide copolymer microspheres (pH response type);

[0116] The high temperature resistant additive is methyltrimethoxysilane modified montmorillonite;

[0117] The dispersant is a combination of sodium dodecylbenzenesulfonate and polyvinylpyrrolidone, and the mass ratio of sodium dodecylbenzenesulfonate to polyvinylpyrrolidone is 1:1;

[0118] The preparation method of the composite leak-while-drilling preventer is as described in Example 1, and is recorded as Sample A3.

[0119] Example 4

[0120] A composite leak-proofing agent while drilling is prepared from the following components in mass fractions:

[0121] Nanocomposite particles 25%, multi-level fiber reinforced network material 35%, intelligent response plugging agent 18%, high temperature resistant additive 5%, dispersant 5%, the balance is deionized water, the total content of each component is 100%;

[0122] The nanocomposite particles are a combination of silane coupling agent modified nano-silica and polyethersulfone resin, with the mass ratio of silane coupling agent modified nano-silica to polyethersulfone resin being 1:4;

[0123] The multi-stage fiber-reinforced network material is a combination of polyacrylonitrile-based carbon fibers, continuous basalt fibers, and cotton fibers, wherein the mass ratio of the polyacrylonitrile-based carbon fibers, the continuous basalt fibers, and the cotton fibers is 1:2:3, and the fiber lengths are 4 mm, 2 mm, and 1 mm, respectively;

[0124] The smart response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH responsive) and thermosensitive chitosan microspheres (temperature responsive), with the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres being 3:2;

[0125] The high temperature resistant additive is a combination of nano titanium dioxide and phenyltriethoxysilane modified montmorillonite, and the mass ratio of nano titanium dioxide to phenyltriethoxysilane modified montmorillonite is 1:2;

[0126] The dispersant is a combination of polycarboxylic acid ammonium salt and hydroxypropyl methylcellulose, and the mass ratio of polycarboxylic acid ammonium salt to hydroxypropyl methylcellulose is 3:2;

[0127] The preparation method of the composite leak-while-drilling preventer is as described in Example 1, and is recorded as sample A4.

[0128] Example 5

[0129] A composite leak-proofing agent while drilling is prepared from the following components in mass fractions:

[0130] Nanocomposite particles 35%, multi-level fiber reinforced network material 28%, intelligent response plugging agent 16%, high temperature resistant additive 7%, dispersant 4%, the balance is deionized water, the total content of each component is 100%;

[0131] The nanocomposite particles are a combination of nano-silica modified by a titanate coupling agent and phenolic resin, wherein the mass ratio of nano-silica modified by a titanate coupling agent to phenolic resin is 2:5;

[0132] The multi-stage fiber-reinforced network material is a combination of asphalt-based carbon fibers, chopped basalt fibers, and sisal fibers, wherein the mass ratio of the asphalt-based carbon fibers, the chopped basalt fibers, and the sisal fibers is 3:3:2, and the fiber lengths are 2 mm, 1 mm, and 2 mm, respectively;

[0133] The smart response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH responsive) and thermosensitive chitosan microspheres (temperature responsive), with the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres being 3:2;

[0134] The high temperature resistant additive is a combination of methyltrimethoxysilane modified montmorillonite and nano-titanium dioxide, and the mass ratio of methyltrimethoxysilane modified montmorillonite to nano-titanium dioxide is 4:3;

[0135] The dispersant is a combination of sodium lignin sulfonate and sodium polyacrylate, and the mass ratio of sodium lignin sulfonate to sodium polyacrylate is 2:5;

[0136] The preparation method of the composite leak-while-drilling preventer is as described in Example 1, and is recorded as Sample A5.

[0137] Comparative Example 1

[0138] A composite leak-proofing agent while drilling, the specific components of which are as described in Example 1, except that: nanocomposite particles are not added;

[0139] The specific raw material composition is as follows: multi-level fiber reinforced network material 45%, intelligent response plugging agent 15%, high temperature resistant additive 5%, dispersant 3%, and the balance is deionized water. The total content of each component is 100%;

[0140] The preparation method was carried out according to Example 1, and the obtained product was recorded as B1.

[0141] Comparative Example 2

[0142] A composite leak-proofing agent while drilling, the specific components of which are as described in Example 1, except that the multi-stage fiber-reinforced network material is not added;

[0143] The specific raw material composition is as follows: nanocomposite particles 40%, intelligent response plugging agent 30%, high temperature resistant additive 5%, dispersant 3%, and the balance is deionized water. The total content of each component is 100%;

[0144] The preparation method was carried out according to Example 1, and the obtained product was recorded as B2.

[0145] Comparative Example 3

[0146] A composite leak-proofing agent while drilling, the specific components of which are as described in Example 1, except that the intelligent response plugging agent uses only single temperature-responsive polymer microspheres and does not add pH-responsive microspheres (acrylic acid / acrylamide copolymer microspheres);

[0147] Specifically, it is prepared from the following components by mass fraction: 40% nanocomposite particles, 25% multi-level fiber-reinforced network material, 15% smart response plugging agent (only poly (N-isopropylacrylamide) microspheres), 5% high temperature resistant additive, 3% dispersant, and the balance is deionized water. The total content of each component is 100%.

[0148] The preparation method was carried out according to Example 1, and the obtained product was recorded as B3.

[0149] Comparative Example 4

[0150] A composite leak-proofing agent while drilling, the specific components of which are as described in Example 1, except that the high-temperature resistant additive is only nano-titanium dioxide, and no organosilicon-modified montmorillonite is added;

[0151] Specifically, it is prepared from the following components by mass fraction: 40% nanocomposite particles, 25% multi-level fiber reinforced network material, 15% intelligent response plugging agent, 5% high temperature resistant additive (only nano titanium dioxide), 3% dispersant, and the balance is deionized water. The total content of each component is 100%.

[0152] The preparation method was carried out according to Example 1, and the obtained product was recorded as B4.

[0153] Comparative Example 5

[0154] A composite leak-proofing agent while drilling, the specific components of which are as described in Example 1, except that only sodium dodecylbenzenesulfonate, that is, only a small molecule anionic dispersant is used as the dispersant, and no non-ionic polymer dispersant is used;

[0155] The specific raw material composition is as follows: nanocomposite particles 40%, multi-level fiber reinforced network material 25%, intelligent response plugging agent 15%, high temperature resistant additive 5%, dispersant 3% (only sodium dodecylbenzene sulfonate), the balance is deionized water, and the total content of each component is 100%;

[0156] The preparation method was carried out according to Example 1, and the obtained product was recorded as B5.

[0157] Test example

[0158] 1. Plugging efficiency and pressure bearing capacity test

[0159] Testing method: Using a high-temperature, high-pressure fracture simulator (220°C, 100 MPa), a 3.0 mm wide fracture was created. The composite leak-through-drilling agents obtained in Examples 1-5 and the composite leak-through-drilling agents obtained in Comparative Examples 1-5 were injected, and the leakage loss and pressure bearing capacity were recorded. Effective plugging was defined as a leakage loss of less than 1 mL / min with no change for 30 minutes. The time it took for the test samples to form a plugging layer and the ultimate compressive strength are shown in Table 1.

[0160] Table 1. Test results of filtration loss and pressure bearing capacity of composite leak-proof agent under high temperature and high pressure

[0161]

[0162] The test results obtained from Table 1 are as follows: A1 of Example 1: leakage 0.6 mL / min, pressure 15.2 MPa, and plugging time 35 minutes.

[0163] Comparative Example 1 B1 (nanocomposite particles): leakage 5.8 mL / min, pressure 8.5 MPa, plugging time 120 minutes (not achieving effective plugging).

[0164] Comparative Example 2 B2 (multi-level fiber reinforced network material): leakage rate 3.2 mL / min, pressure bearing capacity 10.3 MPa, sealing time 60 minutes (leakage at the crack edge).

[0165] 2. High temperature stability test

[0166] Test method: The composite leakage-while-drilling preventers obtained in Examples 1 to 5 and the composite leakage-while-drilling preventers obtained in Comparative Examples 1 to 5 were aged at 220° C. for 168 hours, and the mass loss rate and compressive strength retention rate were measured, as shown in Table 2.

[0167] Table 2. High temperature stability test results of composite leak-proof agent under high temperature and high pressure

[0168]

[0169] The test results obtained from Table 2 are: A1 of Example 1: mass loss 2.3%, compressive strength retention rate 86%.

[0170] Comparative Example 4 B4 (single high temperature resistant additive): mass loss 8.7%, compressive strength retention rate 62%.

[0171] 3. Biodegradation rate test

[0172] Test method: According to the "Water and Wastewater Monitoring and Analysis Methods" (4th edition), the composite leakage-while-drilling preventers obtained in Examples 1 to 5 and the composite leakage-while-drilling preventers obtained in Comparative Examples 1 to 5 were placed in activated sludge culture medium (30°C, 120 rpm). After 28 days of culture, the COD removal rate was measured and the biodegradation rate was calculated. The results are shown in Table 3.

[0173] Table 3. Test results of biodegradation rate of composite leak-proof agent while drilling

[0174]

[0175] The test results obtained from Table 3 are: A1 of Example 1: biodegradation rate 68%.

[0176] Comparative Example 5 B5 (single dispersant): biodegradation rate 52%.

[0177] 4. Intelligent response performance test

[0178] Test method: Under simulated formation alkaline environment (pH=10) and high temperature (180°C) conditions, the swelling rate and curing time of the composite leak-through-while-drilling preventive agents obtained in Examples 1 to 5 and the composite leak-through-while-drilling preventive agents obtained in Comparative Examples 1 to 5 were observed. The results are shown in Table 4.

[0179] Table 4 Test results of intelligent response performance of composite while-drilling leak-proof agent under high temperature alkaline environment

[0180]

[0181] The test results obtained from Table 4 are as follows: A1 of Example 1: the pH-responsive microspheres have a swelling rate of 550%, and the temperature-sensitive resin has a curing time of 4 hours.

[0182] Comparative Example 3 B3 (single intelligent response plugging agent): swelling rate 300% (temperature trigger only), curing time 6 hours (no pH synergy)

[0183] Comprehensively analyzing the data in Tables 1-4, we can see that the composite leak-through-drilling agent (A1 in Example 1) provided by the present invention can achieve efficient and environmentally friendly plugging of ultra-high temperature and high pressure formations, reducing leakage to below 0.5 mL / min, demonstrating its adaptability to ultra-high temperature and high pressure. However, the absence of nanocomposite particles (B1 in Comparative Example 1) leads to failure in micropore plugging and a significant increase in leakage. The absence of the multi-stage fiber-reinforced network material (B2 in Comparative Example 2) reduces the efficiency of large fracture bridging and a 40% decrease in pressure-bearing capacity. The absence of the synergistic effect of the intelligent response plugging agent (B3 in Comparative Example 3) leads to decreased response speed and plugging integrity. The absence of the organosilicon-modified montmorillonite (B4 in Comparative Example 4) significantly reduces high-temperature resistance, demonstrating its key role in maintaining the stability of the cured structure. The simplification of the dispersant compound system (B5 in Comparative Example 5) leads to a reduced biodegradation rate, validating the synergistic advantages of the multiple environmentally friendly components.

[0184] By comparison, it can be seen that the embodiments of the present invention significantly improve the sealing efficiency, high-temperature stability and environmental protection performance of the leak-proof agent through multi-component ratio and process optimization, while the comparative examples fail to achieve the expected results of the invention due to the lack or singleness of key components, further proving the scientificity and innovation of the technical solution.

[0185] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite leak-proofing agent while drilling, characterized in that: It is prepared from the following components in percentage by mass: 20-45% of nanocomposite particles, 15-35% of multi-level fiber-reinforced network materials, 10-20% of intelligent response plugging agent, 5-10% of high temperature resistance additive, 1-5% of dispersant, and the balance is deionized water, with the total content of each component being 100%; The nanocomposite particles are a combination of nano-silicon dioxide and a temperature-sensitive resin; the temperature-sensitive resin is one or a combination of two or more of melamine-formaldehyde resin, phenolic resin, urea-formaldehyde resin, and polyethersulfone resin; The multi-level fiber-reinforced network material is a combination of carbon fiber, basalt fiber and plant fiber; The smart response plugging agent is a combination of pH-responsive polymer microspheres and temperature-responsive polymer microspheres; the pH-responsive polymer microspheres are a combination of one or two of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; the temperature-responsive polymer microspheres are a combination of one or two of poly (N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres; the mass ratio of the pH-responsive polymer microspheres to the temperature-responsive polymer microspheres is (1-2):1; The high temperature resistant additive is a combination of organosilicon-modified montmorillonite and nano-titanium dioxide; the organosilicon-modified montmorillonite is a combination of one or two of methyltrimethoxysilane-modified montmorillonite and phenyltriethoxysilane-modified montmorillonite; the mass ratio of the organosilicon-modified montmorillonite to nano-titanium dioxide is (1-4): (1-3); The dispersant is a combination of a small molecule anionic dispersant and a nonionic polymer dispersant; the small molecule anionic dispersant is one or a combination of two or more of polycarboxylate ammonium salt, sodium lignin sulfonate, and sodium dodecylbenzene sulfonate; the nonionic polymer dispersant is one or a combination of two or more of sodium polyacrylate, polyvinyl pyrrolidone, and hydroxypropyl methylcellulose; the mass ratio of the small molecule anionic dispersant to the nonionic polymer dispersant is (1-3): (1-5).

2. The composite leak-proofing agent while drilling according to claim 1, characterized in that: The composite leak-proofing agent while drilling is prepared from the following components in the following mass percentages: 25-40% nanocomposite particles, 20-25% multi-stage fiber-reinforced network material, 10-15% intelligent response plugging agent, 5-8% high-temperature resistant additive, 3-5% dispersant, and the balance being deionized water. The total content of each component is 100%.

3. The composite leak-proofing agent while drilling according to claim 1, characterized in that: The composite leak-proofing agent while drilling is prepared from the following components in the following mass percentages: 40% nanocomposite particles, 25% multi-stage fiber-reinforced network material, 15% intelligent response plugging agent, 5% high-temperature resistant additive, 3% dispersant, and the balance is deionized water. The total content of each component is 100%.

4. The composite leak-proofing agent while drilling according to claim 1, characterized in that: The mass ratio of the nano-silica and the thermosensitive resin is (1-3): (2-5); The nano-silica is one or a combination of two or more of hydrophilic nano-silica, hydrophobic nano-silica, and surface-modified nano-silica; The hydrophilic nano-silica is nano-silica with a hydroxylated surface. The hydrophobic nano-silica is organosilane-modified nano-silica; The surface-modified nano-silica is nano-silica modified by a silane coupling agent, nano-silica modified by a titanate coupling agent, or nano-silica modified by an aluminate coupling agent; The mass ratio of the carbon fiber, basalt fiber and plant fiber is (2-4): (1-3): (1-2); The carbon fiber is one or a combination of two or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, and viscose-based carbon fiber; The basalt fiber is one of continuous basalt fiber and chopped basalt fiber, or a combination of the two; The plant fiber is one or a combination of two or more of cotton fiber, sisal fiber and wood fiber; The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres and poly N-isopropylacrylamide microspheres, and the mass ratio of acrylic acid / acrylamide copolymer microspheres to poly N-isopropylacrylamide microspheres is 2:1; The high temperature resistant additive is a combination of methyltrimethoxysilane modified montmorillonite and nano-titanium dioxide, and the mass ratio of methyltrimethoxysilane modified montmorillonite to nano-titanium dioxide is 3:1 or 4:3; The dispersant is a combination of sodium dodecylbenzene sulfonate and sodium polyacrylate, and the mass ratio of sodium dodecylbenzene sulfonate to sodium polyacrylate is 2:

3.

5. The composite leak-proofing agent while drilling according to claim 4, characterized in that: The nanocomposite particles are a combination of silane coupling agent modified nano-silica and polyethersulfone resin, and the mass ratio of silane coupling agent modified nano-silica to polyethersulfone resin is 2:3 or 1:4; The multi-stage fiber-reinforced network material is a combination of polyacrylonitrile-based carbon fibers, chopped basalt fibers, and cotton fibers. The mass ratio of the polyacrylonitrile-based carbon fibers, chopped basalt fibers, and cotton fibers is 3:2:1, and the fiber lengths are 2-5 mm, 1-3 mm, and 0.5-2 mm, respectively.

6. The method for preparing the composite leak-while-drilling preventive agent according to any one of claims 1 to 5, characterized in that: The steps are as follows: (1) Preparation of nanocomposite particles: Nano-silica and thermosensitive resin are weighed according to the ratio, added to a high-speed shearing machine and mixed evenly, and spray-dried to form a core-shell structure to obtain nanocomposite particles; (2) Construction of multi-level fiber-reinforced network materials: Carbon fibers, basalt fibers, and plant fibers are dispersed in deionized water according to the ratio to obtain a fiber dispersion; the fiber dispersion is then subjected to ultrasonic treatment and freeze-dried to form a three-dimensional porous skeleton to obtain a multi-level fiber-reinforced network material; (3) Synthesis of smart response plugging agent: pH-responsive polymer microspheres and temperature-responsive polymer microspheres are mixed evenly according to the ratio to obtain the smart response plugging agent; (4) According to the proportion, nanocomposite particles, multi-level fiber reinforced network material, intelligent response plugging agent, high temperature resistant additive, dispersant and deionized water are added into a planetary mixer and mixed evenly, and the water content is controlled to be ≤5% to obtain a composite while-drilling leak-proof agent.

7. The method for preparing the composite leak-while-drilling agent according to claim 6, wherein: In step (1), the speed of the high-speed shearing machine is 10,000 to 15,000 rpm, the mixing time is 30 to 60 minutes, the spray drying air inlet temperature is 200 to 220°C, and the atomization pressure is 0.3 to 0.5 MPa; In step (2), the mass concentration of the fiber dispersion is 5-10%, the ultrasonic treatment power is 500-800W, the time is 10-20 minutes, the freeze drying temperature is -50 to -40°C, the vacuum drying pressure is less than 10Pa, and the time is 24-48 hours; In step (4), the planetary mixer has a rotation speed of 500 to 800 rpm, a mixing time of 20 to 40 minutes, and a particle size distribution of the composite while-drilling leak-proofing agent D90 ≤ 500 μm.

8. The use of the composite leak-while-drilling agent according to any one of claims 1 to 5, characterized in that: Applicable to plugging while drilling or slug plugging.

9. The use of the composite leak-proofing agent while drilling as claimed in claim 8, characterized in that: The application method is as follows: Direct injection while drilling: When the drilling fluid loss rate is greater than 5m³ / h, a leak-proof slurry with a density of 1.8-2.2g / cm³ is prepared at a ratio of 1:(2-3) of composite leak-proof agent while drilling to water. The leak-proof slurry is then pumped through the drill pipe at a rate of 2-3m³ / min. Nanocomposite particles fill micropores and a multi-stage fiber-reinforced network bridges large cracks, achieving rapid plugging. Alternatively, a collaborative plugging process is used: for cracks with a width greater than 2mm, a leak-proof slurry with a density of 1.8-2.2g / cm³ is prepared at a ratio of composite leak-proof agent while drilling to water of 1:(2-3). Inert bridging particles with a particle size of 2-5mm are then injected to form a skeleton, followed by the leak-proof slurry. The bridging particles are bonded by thermosensitive resin curing at high temperature (>180°C) to form an overall plugging layer with a compressive strength of ≥15MPa.

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