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

Abstract

The invention relates to a preparation method and application of a composite leakage-proof agent while drilling, and belongs to the technical field of petroleum drilling engineering. The composite leakage-proof agent while drilling is prepared from the following components in percentage by mass: 20-45% of nano composite particles, 15-35% of a multi-stage fiber reinforced network material, 10-20% of an intelligent response blocking agent, 5-10% of a high-temperature-resistant additive, 1-5% of a dispersing agent and the balance of deionized water, wherein the sum of the contents of all the components is 100%. According to the composite leak-proof agent while drilling provided by the invention, the temperature-sensitive resin with a core-shell structure is introduced, so that a three-dimensional synergistic mechanism of nano-composite particle filling-multistage fiber network bridging-intelligent response curing is realized, and efficient and environment-friendly plugging of an ultrahigh-temperature and high-pressure stratum is realized. The success rate of one-time plugging is increased from 45% to 92%, the average operation time is shortened by 60%, and an efficient solution is provided for deep and ultra-deep drilling.

Description

Technical Field

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

[0002] Well loss is a major technical problem in oil drilling engineering. According to statistics, the incidence rate of well loss in global drilling operations is as high as 20%-25%. Among them, in deep (4500-6000m) and ultra-deep (>6000m) drilling, high temperature (150-250°C), high pressure (80-150MPa) and complex fracture networks (coexistence of nano-millimeter multi-scales) pose severe challenges to lost circulation materials: the thermal degradation of conventional bridging materials at high temperatures leads to a decrease in plugging strength, a stable structure is formed under the scouring of drilling fluid circulation, there is a lack of evaluation means and quantitative characterization methods, and the success rate of on-site application is low.

[0003] Chinese Patent Document CN117343699A provides a lost circulation plugging gel composite fiber, which is composed of ultrafine plant fibers (30 - 50 parts), a composite wetting agent (0.5 - 4 parts), a flow pattern regulator (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 is to achieve multi-stage plugging of cracks through the adhesion between the three-dimensional network structure of plant fibers and gel particles. Experimental data shows that the fluid loss control amount of this material in a 40 - 60 mesh sand bed is reduced by 20% compared with traditional materials, the plugging depth reaches 1 cm under a pressure of 3.5 MPa, and the sand bed shows no tendency to loosen, which is applicable to lost circulation zones with a temperature not higher than 150°C. Chinese Patent Document CN116445138A proposes a composite lost circulation plugging agent composed of diatomite (40 - 60 parts), hydrophobic nano-silica (10 - 20 parts), oleophilic flaky molybdenum disulfide (10 - 15 parts), and oleophilic calcium carbonate (15 - 30 parts). Its innovation lies in the synergistic effect of nano-composite particles and flaky materials: hydrophobic nano-silica (particle size 20 - 50 nm) fills pores, and flaky molybdenum disulfide (thickness 1 - 3 μm) forms a lubricating film on the crack surface to reduce fluid penetration. Laboratory experiments show that this material can increase the dynamic plastic ratio of drilling fluid by 30% and reduce the fluid loss amount to less than 5 mL. Chinese Patent Document CN117264170A designs a self-healing gel lost circulation plugging material based on polyurethane prepolymer, which forms a dynamic network structure through the cross-linking reaction of isocyanate and polyol. When the material is damaged by shear or pressure, the active groups at the fracture can be re-crosslinked to achieve autonomous repair of cracks. Experiments show that under the conditions of 120°C and 10 MPa, the crack repair rate of this material reaches 85%, and the compressive strength after repair recovers to 90% of the original value. Chinese Patent Document CN202410185695A proposes a method for quantitatively evaluating the melting degree at high temperature and high pressure based on gray value analysis, which visually captures the melting process of thermosensitive resins (such as ABS, LDPF) in an aqueous phase environment at 150°C and 20 MPa through a visualization chamber. Chinese Patent Document CN202410186221A develops a composite system of thermosensitive resin and bridging particles, and quantifies the melting degree through the change in the proportion of particle boundary area. Experiments show that when the temperature rises from 120°C to 150°C, the proportion of the particle boundary area of the resin decreases from 70% to 30%, corresponding to the transition of the melting degree from elementary to advanced. When this system is applied in Well Keshen 905 in the Tarim Oilfield (well depth 7850 m, temperature 165°C), the pressure-bearing capacity of the plugging layer increases from 6 MPa to 15 MPa.

[0004] However, although the above patents have made progress in material design and evaluation methods, there are still problems such as the unclear multi-factor coupling mechanism and insufficient exploration of the multi-material composite mechanism. For the complex geological conditions such as high temperature, high pressure, and high salinity in deep and ultra-deep formations, there is a lack of efficient lost circulation prevention materials during drilling. Therefore, developing an environmentally friendly lost circulation preventive agent with the synergistic effect of "nano-scale filling - micro-scale bridging - high-temperature curing enhancement" has become a technical problem that urgently needs to be solved in deep and ultra-deep drilling. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, especially the problems of poor stability, poor gradation, and reservoir pollution risk of existing lost circulation materials in harsh environments such as high temperature and high pressure in deep and ultra-deep formations, the present invention provides a preparation method and application of a composite lost circulation preventive agent during drilling.

[0006] The composite lost circulation preventive agent of the present invention can achieve the 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: through the core-shell structure design of nano-composite particles, the lost circulation preventive agent maintains good fluidity during drilling, avoiding the risk of drill pipe sticking caused by premature curing, while reducing the circulating 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 a high-strength consolidated body is formed in the lost layer by the lost circulation slurry, and the strength retention rate is > 85% after aging at 220 °C for 168 h, and the stability is more than twice that of traditional materials; by adjusting the proportion of the temperature-sensitive resin and the dosage of the intelligent response plugging agent, the curing time and plugging strength can be flexibly controlled to adapt to the lost circulation requirements of different formation temperatures (120 - 220 °C) and fracture sizes (0.01 mm - 3.0 mm), significantly improving the construction safety and lost circulation success rate. At the same time, the proportion of biodegradable materials exceeds 40%, effectively reducing the reservoir pollution risk and meeting the requirements of efficient and environmentally friendly operations in deep and ultra-deep drilling.

[0007] The technical solution of the present invention is as follows: A composite lost circulation preventive agent during drilling, characterized in that it is prepared from the following components by mass percentage: 20 - 45% of nano-composite particles, 15 - 35% of multi-stage fiber-reinforced network materials, 10 - 20% of intelligent response plugging agents, 5 - 10% of high-temperature resistant additives, 1 - 5% of dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano-composite particles are a combination of nano-silica and temperature-sensitive resins; the temperature-sensitive resins are one or a combination of two or more of melamine-formaldehyde resin, phenolic resin, urea-formaldehyde resin, and polyethersulfone resin; The multi-stage fiber-reinforced network materials are a combination of carbon fiber, basalt fiber, and plant fiber; The intelligent response plugging agent is a combination of pH-responsive polymer microspheres and temperature-responsive polymer microspheres; the pH-responsive polymer microspheres are one or a combination of two of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; the temperature-responsive polymer microspheres are one or a combination of two of poly(N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres; The high-temperature resistant additive is one or a combination of two of organosilicon-modified montmorillonite and nano-titanium dioxide; The dispersant is a combination of a small molecule anionic dispersant and a non-ionic polymer dispersant; the small molecule anionic dispersant is one or a combination of two or more of ammonium polycarboxylate, sodium lignosulfonate, and sodium dodecylbenzenesulfonate; the non-ionic polymer dispersant is one or a combination of two or more of sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose.

[0008] Preferably according to the present invention, the composite lost circulation prevention agent while drilling is prepared from the following components by mass percentage: 25-40% of nano-composite particles, 20-25% of multi-stage fiber reinforced network materials, 10-15% of intelligent response plugging agent, 5-8% of high-temperature resistant additive, 3-5% of dispersant, and the balance is deionized water, and the total content of each component is 100%.

[0009] Preferably according to the present invention, the composite lost circulation prevention agent while drilling is prepared from the following components by mass percentage: 40% of nano-composite particles, 25% of multi-stage fiber reinforced network materials, 15% of intelligent response plugging agent, 5% of high-temperature resistant additive, 3% of dispersant, and the balance is deionized water, and the total content of each component is 100%.

[0010] The nano-composite particles of the present invention have the synergistic effect of nano-scale filling and high-temperature curing, and at the same time have good high-temperature and high-pressure resistance performance.

[0011] Preferably according to the present invention, 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 surface hydroxylation treatment; The hydrophobic nano-silica is nano-silica modified with organosilane; The surface-modified nano-silica is nano-silica modified with silane coupling agent, titanate coupling agent, or 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, pitch-based carbon fiber, and viscose-based carbon fiber; The basalt fiber is one or a combination of two of continuous basalt fiber and chopped basalt fiber; The plant fiber is one or a combination of two or more of cotton fiber, sisal fiber, and wood fiber; The mass ratio of the pH-responsive polymer microspheres to the temperature-responsive polymer microspheres is (1 to 2):1; The mass ratio of the organosilicon-modified montmorillonite to the nano-titanium dioxide is (1 to 4):(1 to 3); The organosilicon-modified montmorillonite is one or a combination of two of methyltrimethoxysilane-modified montmorillonite and phenyltriethoxysilane-modified montmorillonite; The mass ratio of the small molecule anionic dispersant to the non-ionic polymer dispersant is (1 to 3):(1 to 5).

[0012] According to the preference of the present invention, the nano composite particles are a combination of silane coupling agent-modified nano-silica and polyethersulfone resin, and the mass ratio of the silane coupling agent-modified nano-silica to the polyethersulfone resin is 2:3 or 1:4; The multi-stage fiber reinforced network material is a combination of polyacrylonitrile-based carbon fiber, chopped basalt fiber, and cotton fiber, and the mass ratio of the polyacrylonitrile-based carbon fiber, chopped basalt fiber, and cotton fiber is 3:2:1, and the fiber lengths are 2 to 5 mm, 1 to 3 mm, and 0.5 to 2 mm respectively; The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres and poly(N-isopropylacrylamide) microspheres, and the mass ratio of the acrylic acid / acrylamide copolymer microspheres to the poly(N-isopropylacrylamide) microspheres is 2:1; the swelling rate of the acrylic acid / acrylamide copolymer microspheres is ≥500% when pH > 9, and the response threshold pH = 9 ± 0.5, and the volume shrinkage rate of the poly(N-isopropylacrylamide) microspheres is ≤10% when the temperature > 180°C; The high temperature resistant additive is a combination of methyltrimethoxysilane-modified montmorillonite and nano-titanium dioxide, and the mass ratio of the methyltrimethoxysilane-modified montmorillonite to the nano-titanium dioxide is 3:1 or 4:3; its layer spacing ≥2.5 nm, and the thermal weight loss rate (220°C) < 5%; The dispersant is a combination of sodium dodecylbenzenesulfonate and sodium polyacrylate, and the mass ratio of the sodium dodecylbenzenesulfonate to the sodium polyacrylate is 2:3, which can ensure that the dispersion uniformity error of each component in the drilling fluid is ≤5%.

[0013] Through the optimization of the multi-component ratio of the composite raw material of the present invention, the synergistic effect of "nanoscale filling - fiber network bridging - intelligent response curing" is realized, enabling the plugging efficiency of the leak prevention agent under high temperature and high pressure to be increased by more than 40% compared with traditional materials, and having excellent reservoir adaptability and environmental protection characteristics.

[0014] The preparation method of the above-mentioned composite while-drilling leak prevention agent includes the following steps: (1) Preparation of nano-composite particles: Weigh nano-silica and temperature-sensitive resin according to the ratio, add them to a high-speed shear mixer and mix evenly, and then form a core-shell structure through spray drying to obtain nano-composite particles; (2) Construction of multi-level fiber-reinforced network material: Disperse carbon fiber, basalt fiber and plant fiber in deionized water according to the ratio to obtain a fiber dispersion; then the fiber dispersion is ultrasonically treated and freeze-dried to form a three-dimensional porous framework to obtain a multi-level fiber-reinforced network material; (3) Synthesis of intelligent response plugging agent: Mix pH-responsive polymer microspheres and temperature-responsive polymer microspheres evenly according to the ratio to obtain an intelligent response plugging agent; (4) According to the ratio, add the nano-composite particles, multi-level fiber-reinforced network material, intelligent response plugging agent, high-temperature resistant additive, dispersant and deionized water to a planetary mixer, mix evenly, and control the water content ≤ 5% to obtain a composite while-drilling leak prevention agent.

[0015] Preferably according to the present invention, in step (1), the rotation speed of the high-speed shear mixer is 10,000 - 15,000 revolutions per minute, the mixing time is 30 - 60 minutes, the inlet air temperature for spray drying is 200 - 220 °C, and the atomization pressure is 0.3 - 0.5 MPa.

[0016] More preferably, the rotation speed of the high-speed shear mixer is 12,000 revolutions per minute, the inlet air temperature for spray drying is 210 °C, core-shell particles with an average particle size of 100 - 200 nm are prepared, and the coating rate of nano-silica ≥ 95%.

[0017] 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 < 10 Pa, and the time is 24 - 48 hours.

[0018] More preferably, the ultrasonic treatment power is 600 W, the freeze-drying temperature is -50 °C, a fiber framework with a porosity of 50 - 60% is formed, and the error of the fiber interweaving density ≤ 5%.

[0019] Preferably according to the present invention, in step (4), the rotation speed of the planetary mixer is 500 - 800 revolutions per minute, the mixing time is 20 - 40 minutes, and the particle size distribution D90 of the composite while-drilling leak prevention agent ≤ 500 μm.

[0020] More preferably, the rotation speed is 600 revolutions per minute and the mixing time is 30 minutes to ensure that the dispersion uniformity error of each component is ≤ 3%.

[0021] Preferably according to the present invention, in steps (1) to (4), the deionized water used has a conductivity ≤ 10 μS / cm and the raw material purity ≥ 98% to ensure the stability of the reaction system.

[0022] According to the present invention, the application of the above composite lost circulation preventive agent while drilling is applied to lost circulation prevention while drilling or slugging lost circulation prevention.

[0023] Preferably according to the present invention, the application method is specifically as follows: Direct injection while drilling: When the drilling fluid loss rate > 5 m³ / h, prepare a lost circulation prevention slurry with a density of 1.8 - 2.2 g / cm³ according to the ratio of composite lost circulation preventive agent while drilling: water = 1: (2 - 3); then pump the lost circulation prevention slurry through the drill pipe at a displacement of 2 - 3 m³ / min, and use the nano-composite particles to fill the micro-pores and the multi-stage fiber reinforced network to bridge the large cracks to achieve rapid lost circulation prevention; Or, a collaborative plugging process: For cracks with a width > 2 mm, prepare a lost circulation prevention slurry with a density of 1.8 - 2.2 g / cm³ according to the ratio of composite lost circulation preventive agent while drilling: water = 1: (2 - 3); then first inject inert bridging particles with a particle size of 2 - 5 mm (such as corncobs) to form a framework, and then inject the lost circulation prevention slurry. The temperature-sensitive resin cures at high temperature (> 180 °C) to bond the bridging particles to form an integral plugging layer with a compressive strength ≥ 15 MPa.

[0024] The technical features and beneficial effects of the present invention are as follows: 1. The composite lost circulation preventive agent while drilling provided by the present invention introduces a core-shell structure temperature-sensitive resin, realizing a three-dimensional collaborative mechanism of "nano-composite particle filling - multi-stage fiber network bridging - intelligent response curing" to achieve efficient and environmentally friendly plugging in ultra-high temperature and high-pressure formations. This technology has completed on-site tests in the Moxi block of the Sichuan Basin (well depth 6500 m, temperature 150 °C). The single lost circulation prevention success rate has increased from 45% to 92%, and the average operation time has been shortened by 60%, providing an efficient solution for deep and ultra-deep well drilling.

[0025] 2. The composite lost circulation preventive agent while drilling provided by the present invention has a multi-stage collaborative plugging mechanism. Among them, nano-silica fills nano-scale pores (< 100 nm), the multi-stage fiber network quickly bridges millimeter-scale cracks (1 - 3 mm), and the intelligent response plugging agent responds to the formation environment to dynamically adjust the plugging structure, achieving full coverage of cracks from 0.01 to 3.0 mm. The leakage rate can be reduced to below 0.5 mL / min, and the plugging efficiency is increased by 40% compared with traditional materials.

[0026] 3. The composite lost circulation preventive agent provided by the present invention has ultra-high temperature and high pressure adaptability. The thermosensitive resin and organosilicon-modified montmorillonite in it act synergistically, so that after the lost circulation preventive agent is aged for 168 h under the conditions of 220 °C and 100 MPa, the compressive strength retention rate > 85%, and the mass loss rate < 3%, breaking through the bottleneck that traditional materials fail above 200 °C.

[0027] 4. The composite lost circulation preventive agent provided by the present invention can accurately control the curing time. By adjusting the proportion of the thermosensitive resin and the dosage of the intelligent response plugging agent, the curing time (2 - 6 hours) can be flexibly controlled to ensure that the lost circulation prevention slurry maintains a low viscosity (≤50 mPa·s) during the pumping process, avoiding the risk of drill sticking, and at the same time quickly forming a high-strength consolidated body at the formation temperature.

[0028] 5. The composite lost circulation preventive agent provided by the present invention has the advantages of environmental protection and reservoir protection. The proportion of biodegradable materials such as plant fibers and pH-responsive microspheres in it exceeds 40%, the heavy metal content is lower than 0.1 ppm, and the biodegradation rate ≥ 65%, meeting the green drilling standard and significantly reducing the risk of reservoir pollution.

[0029] 6. The composite lost circulation preventive agent provided by the present invention is efficient and convenient for construction. It can take effect by being injected while drilling, without stopping the drill to adjust the formula. The single-well lost circulation plugging operation time 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 the operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a thermogravimetric analysis diagram of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; In the figure, A is acrylic acid / acrylamide copolymer microspheres, and B is methacrylic acid / maleic anhydride copolymer microspheres.

[0031] Figure 2 It is a thermogravimetric analysis diagram of poly(N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres; In the figure, A is poly(N-isopropylacrylamide) microspheres and B is thermosensitive chitosan microspheres.

[0032] Figure 3 It is an infrared spectrum diagram of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; In the figure, A is acrylic acid / acrylamide copolymer microspheres, and B is methacrylic acid / maleic anhydride copolymer microspheres.

[0033] Figure 4 It is an infrared spectrum diagram of poly(N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres; In the figure, A is poly(N-isopropylacrylamide) microspheres and B is thermosensitive chitosan microspheres.

[0034] Figure 5 It is a physical photo of the composite lost circulation prevention agent described in Example 1. Detailed implementation manners

[0035] The present invention will be further described below in conjunction with specific embodiments, but not limited thereto. All raw materials used in the embodiments are conventional raw materials and can be obtained commercially; the methods are all prior arts unless otherwise specified.

[0036] In the present invention, the pH-responsive polymer microspheres are prepared according to the following method: Mix liquid paraffin and cyclohexane, add emulsifiers Span80 and Tween80, stir evenly at 300 - 500 r / min, and then heat up to 45 - 55 °C to obtain the oil phase, and keep it at a constant temperature for standby; Among them, the volume ratio of liquid paraffin to cyclohexane is 4:1; the addition amount of Span80 is 0.82% of the mass of liquid paraffin; the mass ratio of Span80 to Tween80 is 2:1; Dissolve the pH-responsive monomer, comonomer, and crosslinking agent in deionized water in sequence, adjust the pH to neutral with NaOH solution, then add the initiator solution, and continuously stir until completely dissolved to obtain the aqueous phase; Among them, 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 comonomer; the crosslinking agent is N,N'-methylenebisacrylamide (MBA), and the addition amount is 0.1 - 1% of the total mass of the pH-responsive monomer and comonomer; Drop the aqueous phase into the oil phase at a dropping rate of 1 - 2 mL / min slowly, and at the same time start high-speed stirring, and maintain the stirring speed at 800 - 1000 r / min to form a stable emulsion system; after the emulsion is formed, heat up to 55 - 65 °C, keep warm and react for 3 - 5 hours, and always maintain the stirring rate during the reaction process to ensure full reaction; after the reaction is completed, add ethanol or acetone for demulsification, obtain microspheres by centrifugal separation, then wash the microspheres with deionized water and ethanol alternately for 3 - 5 times to remove the residual emulsifier and unreacted monomers, and finally obtain the pH-responsive polymer microspheres by vacuum drying or freeze drying.

[0037] According to this method, when acrylic acid is used as the pH-responsive monomer and acrylamide is used as the comonomer, acrylic acid / acrylamide 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, methacrylic acid / maleic anhydride copolymer microspheres are prepared.

[0038] Poly(N-isopropylacrylamide) microspheres with thermosensitive properties are prepared according to the following method: First, dissolve the temperature-responsive monomer N-isopropylacrylamide (NIPAM) and the crosslinking agent N,N'-methylenebisacrylamide (MBA) in deionized water to prepare a monomer solution with a mass fraction of 10-20%. After stirring evenly, add the initiator solution and react in a constant temperature water bath at 40-60 °C for 3-6 hours. After the reaction, cool to room temperature, collect the microspheres by centrifugation, wash them alternately with deionized water and ethanol 3-5 times, and finally dry them to constant weight in a vacuum at 40-50 °C to obtain poly(N-isopropylacrylamide) microspheres with thermosensitive properties.

[0039] 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 composition of ammonium persulfate (APS) and sodium bisulfite, and the addition amount is 0.5-1% of the mass of N-isopropylacrylamide (NIPAM).

[0040] Thermosensitive chitosan microspheres are prepared according to the following method: First, add Span80 to liquid paraffin and stir evenly, then slowly drop the chitosan acetate solution to form a W / O emulsion under high-speed stirring at 800-1200 r / min; then drop the glutaraldehyde solution and carry out a cross-linking reaction at room temperature for 2-4 hours. After the reaction, add anhydrous ethanol to demulsify, and collect the microspheres by centrifugation; wash them alternately with anhydrous ethanol and deionized water 3-5 times, and finally dry them to constant weight in a vacuum at 40-50 °C to obtain thermosensitive chitosan microspheres with amino groups on the surface; Among them, the mass concentration of the chitosan acetate solution is 1-3%, and the dosage is 10-20% of the volume of liquid paraffin; the volume concentration of the glutaraldehyde solution is 2-5%, and the dosage is 10-30% of the volume of liquid paraffin; the amount of Span80 is 1-3% of the volume of liquid paraffin.

[0041] The thermogravimetric analysis diagrams of the above acrylic / acrylamide copolymer microspheres, methacrylic acid / maleic anhydride copolymer microspheres, poly(N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres are as Figures 1 - 2 shown, and the infrared spectra are as Figures 3 - 4 shown.

[0042] It can be seen from Figures 1 - 4 that pH-responsive polymer microspheres (acrylic / acrylamide copolymer microspheres, methacrylic acid / maleic anhydride copolymer microspheres) and temperature-responsive polymer microspheres (poly(N-isopropylacrylamide) microspheres and thermosensitive chitosan microspheres) are successfully prepared.

[0043] Example 1 A composite lost circulation preventive agent while drilling is prepared from the following components by mass percentage: 40% nano-composite particles, 25% multi-level fiber reinforced network material, 15% intelligent response plugging agent, 5% high temperature resistant additive, 3% dispersant, and the balance is deionized water. The sum of the contents of each component is 100%; The nano-composite particles are a combination of silane coupling agent modified nano-silica and polyethersulfone resin. The mass ratio of silane coupling agent modified nano-silica to polyethersulfone resin is 2:3; The multi-level fiber reinforced network material is a combination of polyacrylonitrile-based carbon fiber, chopped basalt fiber and cotton fiber. The mass ratio of polyacrylonitrile-based carbon fiber, chopped basalt fiber to cotton fiber is 3:2:1, and the fiber lengths are 3mm, 2mm and 1mm respectively; The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres (pH-responsive) and poly(N-isopropylacrylamide) microspheres (temperature-responsive). 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. The mass ratio of methyltrimethoxysilane modified montmorillonite to nano-titanium dioxide is 3:1; The dispersant is a combination of sodium dodecylbenzenesulfonate and sodium polyacrylate. The mass ratio of sodium dodecylbenzenesulfonate to sodium polyacrylate is 2:3.

[0044] The preparation method of the above composite anti-leakage agent while drilling is as follows: (1) Preparation of nano-composite particles: Weigh surface modified nano-silica and polyethersulfone resin according to the ratio, add them to a high-speed shear machine, mix at 12,000 revolutions per minute for 45 minutes, and form a core-shell structure through spray drying to obtain nano-composite particles; Among them, the parameters of spray drying are: inlet air temperature 210°C, atomization pressure 0.4MPa; (2) Construction of multi-level fiber reinforced network material: Disperse carbon fiber, basalt fiber and plant fiber according to the ratio in deionized water to obtain a fiber dispersion with a mass concentration of 8%; then the fiber dispersion is ultrasonically treated and freeze-dried to form a three-dimensional porous skeleton to obtain a multi-level fiber reinforced network material; Among them, the parameters of ultrasonic treatment are: power 600W, time 15 minutes; the parameters of freeze-drying are: temperature -50°C, pressure <10Pa, time 36 hours; (3) Synthesis of intelligent response plugging agent: Mix pH-responsive polymer microspheres and temperature-responsive polymer microspheres according to the ratio to obtain an intelligent response plugging agent; (4)According to the ratio, add nano-composite particles, multi-level fiber reinforced network materials, intelligent response plugging agents, high-temperature resistance aids, dispersants and deionized water into a planetary mixer, mix at 600 revolutions per minute for 30 minutes, and dry until the moisture content ≤ 5% to obtain a composite lost circulation prevention agent during drilling, denoted as sample A1.

[0045] The physical photo of the composite lost circulation prevention agent during drilling prepared in this example is as Figure 5 shown.

[0046] As Figure 5 can be seen, the composite lost circulation prevention agent during drilling described in this example is successfully prepared and is in the form of white powder.

[0047] Example 2 A composite lost circulation prevention agent during drilling is prepared from the following components by mass fraction: 30% nano-composite particles, 30% multi-level fiber reinforced network materials, 20% intelligent response plugging agents, 8% high-temperature resistance aids, 4% dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano-composite particles are a combination of organosilane-modified nano-silica and phenolic resin, and the mass ratio of organosilane-modified nano-silica to phenolic resin is 1:2; The multi-level fiber reinforced network materials are a combination of pitch-based carbon fiber, continuous basalt fiber and sisal fiber, and the mass ratio of pitch-based carbon fiber, continuous basalt fiber to sisal fiber is 2:3:2, and the fiber lengths are 4mm, 2.5mm and 1.5mm respectively; The intelligent response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH-responsive) and thermosensitive chitosan microspheres (temperature-responsive), and the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres is 1:1; The high-temperature resistance aid 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; The dispersant is a combination of sodium lignosulfonate and hydroxypropyl methylcellulose, and the mass ratio of sodium lignosulfonate to hydroxypropyl methylcellulose is 1:2.

[0048] The preparation method of the above composite lost circulation prevention agent during drilling is as described in Example 1, denoted as sample A2.

[0049] Example 3 A composite lost circulation prevention agent during drilling is prepared from the following components by mass fraction: 45% nano-composite particles, 20% multi-level fiber reinforced network materials, 10% intelligent response plugging agents, 10% high-temperature resistance aids, 2% dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano-composite particles are a combination of surface-hydroxylated nano-silica and melamine-formaldehyde resin, and the mass ratio of surface-hydroxylated nano-silica to melamine-formaldehyde resin is 3:4; The multi-level fiber reinforced network material is a combination of viscose-based carbon fiber, chopped basalt fiber and wood fiber, and the mass ratio of viscose-based carbon fiber, chopped basalt fiber to wood fiber is 4:1:1, and the fiber lengths are 2 mm, 1.5 mm and 1 mm respectively; The intelligent response plugging agent is acrylic / acrylamide copolymer microspheres (pH-responsive type); The high temperature resistant additive is methyltrimethoxysilane modified montmorillonite; The dispersant is a combination of sodium dodecylbenzenesulfonate and polyvinylpyrrolidone, and the mass ratio of sodium dodecylbenzenesulfonate to polyvinylpyrrolidone is 1:1; The preparation method of the above composite lost circulation control agent while drilling is as described in Example 1, denoted as sample A3.

[0050] Example 4 A composite lost circulation control agent while drilling is prepared from the following components by mass fraction: Nano-composite particles 25%, multi-level fiber reinforced network material 35%, intelligent response plugging agent 18%, high temperature resistant additive 5%, dispersant 5%, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano-composite 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 1:4; The multi-level fiber reinforced network material is a combination of polyacrylonitrile-based carbon fiber, continuous basalt fiber and cotton fiber, and the mass ratio of polyacrylonitrile-based carbon fiber, continuous basalt fiber to cotton fiber is 1:2:3, and the fiber lengths are 4 mm, 2 mm and 1 mm respectively; The intelligent response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH-responsive type) and thermosensitive chitosan microspheres (temperature-responsive type), and the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres is 3:2; 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; 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; The preparation method of the above composite lost circulation control agent while drilling is as described in Example 1, denoted as sample A4.

[0051] Example 5 A composite lost circulation prevention agent while drilling is prepared from the following components by mass fraction: 35% of nano-composite particles, 28% of multi-stage fiber reinforced network material, 16% of intelligent response plugging agent, 7% of high temperature resistant additive, 4% of dispersant, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano-composite particles are a combination of titanate coupling agent modified nano-silica and phenolic resin, and the mass ratio of titanate coupling agent modified nano-silica to phenolic resin is 2:5; The multi-stage fiber reinforced network material is a combination of pitch-based carbon fiber, chopped basalt fiber and sisal fiber, and the mass ratio of pitch-based carbon fiber, chopped basalt fiber and sisal fiber is 3:3:2, and the fiber lengths are 2 mm, 1 mm and 2 mm respectively; The intelligent response plugging agent is a combination of methacrylic acid / maleic anhydride copolymer microspheres (pH-responsive type) and thermosensitive chitosan microspheres (temperature-responsive type), and the mass ratio of methacrylic acid / maleic anhydride copolymer microspheres to thermosensitive chitosan microspheres is 3:2; 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; The dispersant is a combination of sodium lignosulfonate and sodium polyacrylate, and the mass ratio of sodium lignosulfonate to sodium polyacrylate is 2:5; The preparation method of the above composite lost circulation prevention agent while drilling is as described in Example 1, denoted as sample A5.

[0052] Comparative Example 1 A composite lost circulation prevention agent while drilling, the specific components are as described in Example 1, the difference is that: no nano-composite particles are added; The specific raw material composition is as follows: 45% of multi-stage fiber reinforced network material, 15% of intelligent response plugging agent, 5% of high temperature resistant additive, 3% of dispersant, and the balance is deionized water, and the sum of the contents of each component is 100%; The preparation method is carried out according to Example 1, and the obtained product is denoted as B1.

[0053] Comparative Example 2 A composite lost circulation prevention agent while drilling, the specific components are as described in Example 1, the difference is that: no multi-stage fiber reinforced network material is added; The specific raw material composition is as follows: 40% of nano-composite particles, 30% of intelligent response plugging agent, 5% of high temperature resistant additive, 3% of dispersant, and the balance is deionized water, and the sum of the contents of each component is 100%; The preparation method is carried out according to Example 1, and the obtained product is denoted as B2.

[0054] Comparative Example 3 A composite lost circulation preventive agent while drilling, with specific components as described in Example 1, the difference is that: the intelligent response plugging agent only uses a single temperature-responsive polymer microsphere and does not add pH-responsive microspheres (acrylic / acrylamide copolymer microspheres); Specifically, it is prepared from the following components by mass fraction: 40% of nano-composite particles, 25% of multi-stage fiber reinforced network materials, 15% of intelligent response plugging agent (only poly-N-isopropylacrylamide microspheres), 5% of high-temperature resistant additives, 3% of dispersant, and the balance is deionized water, and the sum of the contents of each component is 100%; The preparation method is carried out according to Example 1, and the obtained product is denoted as B3.

[0055] Comparative Example 4 A composite lost circulation preventive agent while drilling, with specific components as described in Example 1, the difference is that: the high-temperature resistant additive only uses nano-titanium dioxide and does not add organosilicon-modified montmorillonite; Specifically, it is prepared from the following components by mass fraction: 40% of nano-composite particles, 25% of multi-stage fiber reinforced network materials, 15% of intelligent response plugging agent, 5% of high-temperature resistant additives (only nano-titanium dioxide), 3% of dispersant, and the balance is deionized water, and the sum of the contents of each component is 100%; The preparation method is carried out according to Example 1, and the obtained product is denoted as B4.

[0056] Comparative Example 5 A composite lost circulation preventive agent while drilling, with specific components as described in Example 1, the difference is that: the dispersant only uses sodium dodecylbenzenesulfonate, that is, only uses a small molecule anionic dispersant and does not use a non-ionic polymer dispersant; The specific raw material composition is as follows: 40% of nano-composite particles, 25% of multi-stage fiber reinforced network materials, 15% of intelligent response plugging agent, 5% of high-temperature resistant additives, 3% of dispersant (only sodium dodecylbenzenesulfonate), and the balance is deionized water, and the sum of the contents of each component is 100%; The preparation method is carried out according to Example 1, and the obtained product is denoted as B5.

[0057] Test Example 1. Plugging efficiency and pressure-bearing capacity test Test method: Using a high-temperature and high-pressure fracture simulation device (temperature 220 °C, pressure 100 MPa), set a 3.0 mm wide crack, and record the leakage amount and pressure-bearing capacity after injecting the composite lost circulation preventive agents obtained in Examples 1 to 5 and the composite lost circulation preventive agents obtained in Comparative Examples 1 to 5. Taking the leakage amount < 1 mL / min and remaining unchanged for 30 minutes as the effective plugging standard, the time for the test sample to form a plugging layer and the final compressive strength are shown in Table 1.

[0058] Table 1. Test results of the filtration loss and pressure-bearing capacity of the composite lost circulation preventive agent under high temperature and high pressure

[0059] The test results obtained from Table 1 are as follows: For A1 in Example 1: leakage rate 0.6 mL / min, pressure resistance 15.2 MPa, plugging time 35 minutes.

[0060] For B1 (nano composite particles) in Comparative Example 1: leakage rate 5.8 mL / min, pressure resistance 8.5 MPa, plugging time 120 minutes (ineffective plugging).

[0061] For B2 (multi-level fiber reinforced network material) in Comparative Example 2: leakage rate 3.2 mL / min, pressure resistance 10.3 MPa, plugging time 60 minutes (leakage at the crack edge).

[0062] 2. High-temperature stability test Test method: The composite lost circulation control agents obtained from Examples 1 to 5 and the composite lost circulation control agents obtained from 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.

[0063] Table 2. High-temperature stability test results of composite lost circulation control agents under high temperature and high pressure

[0064] The test results obtained from Table 2 are as follows: For A1 in Example 1: mass loss 2.3%, compressive strength retention rate 86%.

[0065] For B4 (single high-temperature resistant additive) in Comparative Example 4: mass loss 8.7%, compressive strength retention rate 62%.

[0066] 3. Biodegradation rate test Test method: According to "Methods for Monitoring and Analysis of Water and Wastewater" (Fourth Edition), the composite lost circulation control agents obtained from Examples 1 to 5 and the composite lost circulation control agents obtained from Comparative Examples 1 to 5 were placed in activated sludge culture medium (30 °C, 120 rpm), and the COD removal rate was measured after 28 days of cultivation, and the biodegradation rate was calculated as shown in Table 3.

[0067] Table 3. Biodegradation rate test results of composite lost circulation control agents

[0068] The test results obtained from Table 3 are as follows: For A1 in Example 1: biodegradation rate 68%.

[0069] For B5 (single dispersant) in Comparative Example 5: biodegradation rate 52%.

[0070] 4. Intelligent response performance test Test method: Simulate the alkaline formation environment (pH = 10) and high temperature (180 °C) conditions, and observe the swelling rate and curing time of the composite lost circulation prevention agents obtained in Examples 1-5 and the composite lost circulation prevention agents obtained in Comparative Examples 1-5. The results are shown in Table 4.

[0071] Table 4 Test results of the intelligent response performance of the composite lost circulation prevention agent in a high-temperature alkaline environment

[0072] The test results obtained from Table 4 are as follows: For A1 in Example 1: The swelling rate of the pH-responsive microspheres is 550%, and the curing time of the thermosensitive resin is 4 hours.

[0073] For B3 in Comparative Example 3 (single intelligent response plugging agent): The swelling rate is 300% (only triggered by temperature), and the curing time is 6 hours (without pH synergy) Based on the data results in Tables 1-4, it can be seen that the composite lost circulation prevention agent provided by the present invention (A1 in Example 1) can achieve efficient and environmentally friendly plugging in ultra-high temperature and high-pressure formations. The lost circulation volume can be reduced to less than 0.5 mL / min, and it has ultra-high temperature and high-pressure adaptability. The absence of nano-composite particles (B1 in Comparative Example 1) leads to the failure of micro-porosity plugging and a significant increase in the lost circulation volume; the absence of the multi-stage fiber-reinforced network material (B2 in Comparative Example 2) reduces the bridging efficiency of large fractures and the pressure-bearing capacity by 40%; the absence of the synergistic effect of the intelligent response plugging agent (B3 in Comparative Example 3) leads to a decrease in the response speed and plugging integrity. The absence of organosilicon-modified montmorillonite (B4 in Comparative Example 4) significantly attenuates the high-temperature resistance, demonstrating its key role in maintaining the stability of the cured structure. The simplification of the dispersant compounding system (B5 in Comparative Example 5) leads to a decrease in the biodegradation rate, verifying the synergistic advantages of the multi-component environmental protection components.

[0074] By comparison, it can be seen that through the multi-component ratio and process optimization in each embodiment of the present invention, the plugging efficiency, high-temperature stability, and environmental performance of the lost circulation prevention agent have been significantly improved. However, due to the absence or singularity of the key components in the comparative examples, the performance has not reached the expected effect of the invention, further proving the scientificity and innovation of the technical solution.

[0075] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A composite lost circulation prevention agent while drilling, characterized in that, It is prepared from the following components by mass percentage: 20 - 45% of nano - composite particles, 15 - 35% of multi - level fiber - reinforced network materials, 10 - 20% of intelligent response plugging agents, 5 - 10% of high - temperature resistance aids, 1 - 5% of dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%; The nano - composite particles are a combination of nano - silica and thermosensitive resin; the thermosensitive 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 materials are a combination of carbon fiber, basalt fiber, and plant fiber; The intelligent response plugging agent is a combination of pH - responsive polymer microspheres and temperature - responsive polymer microspheres; the pH - responsive polymer microspheres are one or a combination of two of acrylic acid / acrylamide copolymer microspheres and methacrylic acid / maleic anhydride copolymer microspheres; the temperature - responsive polymer microspheres are one or a combination of two of poly(N - isopropylacrylamide) microspheres and thermosensitive chitosan microspheres; The high - temperature resistance aids are one or a combination of two of organosilicon - modified montmorillonite and nano - titanium dioxide; The dispersants are a combination of small - molecule anionic dispersants and non - ionic polymer dispersants; the small - molecule anionic dispersants are one or a combination of two or more of ammonium polycarboxylate, sodium lignosulfonate, and sodium dodecylbenzenesulfonate; the non - ionic polymer dispersants are one or a combination of two or more of sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose.

2. The composite lost circulation prevention agent according to claim 1, characterized in that, The composite lost - circulation prevention agent while drilling is prepared from the following components by mass percentage: 25 - 40% of nano - composite particles, 20 - 25% of multi - level fiber - reinforced network materials, 10 - 15% of intelligent response plugging agents, 5 - 8% of high - temperature resistance aids, 3 - 5% of dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%.

3. The composite lost circulation prevention agent according to claim 1, characterized in that The composite lost - circulation prevention agent while drilling is prepared from the following components by mass percentage: 40% of nano - composite particles, 25% of multi - level fiber - reinforced network materials, 15% of intelligent response plugging agents, 5% of high - temperature resistance aids, 3% of dispersants, and the balance is deionized water, and the sum of the contents of each component is 100%.

4. The composite lost circulation prevention agent according to claim 1, wherein, The mass ratio of the nano - silica to 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 surface hydroxylation treatment; The hydrophobic nano - silica is organosilane - modified nano - silica; The surface - modified nano - silica is nano - silica modified by silane coupling agent, titanate coupling agent, or 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, pitch - based carbon fiber, and viscose - based carbon fiber; The basalt fiber is one or a combination of two of continuous basalt fiber and chopped basalt fiber; The plant fiber is one or a combination of two or more of cotton fiber, sisal fiber, and wood fiber; The mass ratio of the pH-responsive polymer microspheres to the temperature-responsive polymer microspheres is (1~2):1; The mass ratio of the organosilicon-modified montmorillonite to the nano-titanium dioxide is (1~4):(1~3); The organosilicon-modified montmorillonite is one or a combination of two of methyltrimethoxysilane-modified montmorillonite and phenyltriethoxysilane-modified montmorillonite; The mass ratio of the small molecule anionic dispersant to the nonionic polymer dispersant is (1~3):(1~5).

5. The composite lost circulation prevention agent according to claim 4, characterized in that, The nano composite particles are a combination of silane coupling agent-modified nano-silica and polyethersulfone resin, and the mass ratio of the silane coupling agent-modified nano-silica to the polyethersulfone resin is 2:3 or 1:4; The multi-stage fiber reinforced network material is a combination of polyacrylonitrile-based carbon fiber, chopped basalt fiber, and cotton fiber. The mass ratio of the polyacrylonitrile-based carbon fiber, chopped basalt fiber, and cotton fiber is 3:2:1, and the fiber lengths are 2~5mm, 1~3mm, and 0.5~2mm respectively; The intelligent response plugging agent is a combination of acrylic acid / acrylamide copolymer microspheres and poly-N-isopropylacrylamide microspheres, and the mass ratio of the acrylic acid / acrylamide copolymer microspheres to the 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 the methyltrimethoxysilane-modified montmorillonite to the nano-titanium dioxide is 3:1 or 4:3; The dispersant is a combination of sodium dodecylbenzenesulfonate and sodium polyacrylate, and the mass ratio of the sodium dodecylbenzenesulfonate to the sodium polyacrylate is 2:

3.

6. The preparation method of the composite lost circulation prevention agent according to any one of claims 1 to 4, characterized in that, It includes the following steps: (1) Preparation of nano composite particles: Weigh nano-silica and temperature-sensitive resin according to the ratio, add them to a high-speed shear mixer and mix evenly, and form a core-shell structure by spray drying to obtain nano composite particles; (2) Construction of multi-stage fiber reinforced network material: Disperse carbon fiber, basalt fiber, and plant fiber in deionized water according to the ratio to obtain a fiber dispersion; then the fiber dispersion is ultrasonically treated and freeze-dried to form a three-dimensional porous framework to obtain a multi-stage fiber reinforced network material; (3) Synthesis of intelligent response plugging agent: Mix the pH-responsive polymer microspheres and the temperature-responsive polymer microspheres evenly according to the ratio to obtain an intelligent response plugging agent; (4) According to the ratio, add the nano composite particles, multi-stage fiber reinforced network material, intelligent response plugging agent, high temperature resistant additive, dispersant, and deionized water to a planetary mixer, mix evenly, and control the moisture content ≤5% to obtain a composite while-drilling leak prevention agent.

7. The preparation method of the composite drilling fluid loss prevention agent according to claim 5, wherein, In step (1), the rotation speed of the high-speed shear mixer is 10000~15000 revolutions per minute, the mixing time is 30~60 minutes, the inlet air temperature of spray drying is 200~220°C, and the atomization pressure is 0.3~0.5MPa; In step (2), the mass concentration of the fiber dispersion liquid 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; In step (4), the rotation speed of the planetary mixer is 500-800 revolutions per minute, the mixing time is 20-40 minutes, and the particle size distribution D90 of the composite lost circulation prevention agent while drilling is ≤500 μm.

8. Use of the composite lost circulation prevention agent according to any one of claims 1 to 5, characterized in that, It is applied to lost circulation prevention while drilling or slug lost circulation prevention.

9. The application of the composite lost circulation prevention agent according to claim 8, characterized in that, The specific application method is as follows: Direct injection while drilling: When the drilling fluid loss rate > 5 m³ / h, a lost circulation prevention slurry with a density of 1.8-2.2 g / cm³ is prepared according to the ratio of the composite lost circulation prevention agent while drilling: water = 1: (2-3); then the lost circulation prevention slurry is pumped through the drill pipe at a displacement of 2-3 m³ / min, and the nano-composite particles are used to fill the micro-pores and the multi-stage fiber-reinforced network bridges the large cracks to achieve rapid lost circulation prevention; Or, a collaborative plugging process: For cracks with a width > 2 mm, a lost circulation prevention slurry with a density of 1.8-2.2 g / cm³ is prepared according to the ratio of the composite lost circulation prevention agent while drilling: water = 1: (2-3); then inert bridging particles with a particle size of 2-5 mm are first injected to form a skeleton, and then the lost circulation prevention slurry is injected. The temperature-sensitive resin is cured at a high temperature (>180 °C) to bond the bridging particles to form an integral plugging layer with a compressive strength ≥15 MPa.

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