Resin precoated sand well wall reinforcer capable of resisting high temperature of 260 DEG C and preparation method and application of resin precoated sand well wall reinforcer

Abstract

The invention provides a high-temperature 260 DEG C resistant resin precoated sand well wall reinforcer as well as a preparation method and application thereof. The SiO2-PES-LCP well wall reinforcer microspheres are prepared by adopting a silane coupling agent to perform modification treatment on nano SiO2 particles and then performing in-situ coating on the modified SiO2 particles by utilizing two high-temperature-resistant thermoplastic resins, namely polyether sulfone and a liquid crystal polymer. Through the synergistic effect of a polyether sulfone and liquid crystal polymer blending system and the modified nano SiO2 particles, the glass-transition temperature of a resin system is adjusted, the bonding strength of a coating and the surface of a rock core is remarkably improved, it is ensured that the plugging strengthening effect can still be stably achieved under the high-temperature condition of 260 DEG C, and the sealing performance of the rock core is improved. Therefore, the problem that the well wall strengthening performance of the existing well wall strengthening agent in a deep stratum is insufficient is effectively solved.

Description

Technical Field

[0001] The invention relates to a high-temperature resistant 260°C resin-coated sand well wall strengthener and a preparation method and application thereof, belonging to the technical field of well wall strengtheners for drilling fluids in petroleum exploration and development. Background Art

[0002] Deep and ultra-deep oil and gas exploration has become a crucial area of ​​oil and gas production. With increasing depth, formation temperatures gradually increase, particularly at well depths exceeding 8,000 meters, where temperatures typically reach 180°C to 260°C or even higher. Under the influence of high temperatures, high pressures, and complex stresses, wellbore stability issues are becoming increasingly prominent, seriously impacting the safety and efficiency of drilling operations. Particularly in complex, brittle formations such as shale, carbonate, and dolomite, the presence of numerous closed or open microcracks and bedding planes, coupled with strong capillary action, allows drilling fluid filtrate to easily intrude into the formation under the influence of positive pressure differentials and capillary pressure, further propagating fractures and inducing cracks to develop along bedding planes. This can ultimately lead to wellbore cracking, block shedding, and even collapse. In severe cases, this can cause complex accidents such as stuck pipe and wellbore instability.

[0003] To avoid these problems, wellbore reinforcement agents are often used to effectively seal fractures, preventing drilling fluid filtrate from further penetrating into the formation. However, conventional drilling fluid plugging agents, such as asphalt or common polymer plugging agents, suffer from low softening points and susceptibility to degradation at high temperatures. While nanomaterials offer theoretical advantages for pore plugging, they generally suffer from poor dispersion stability at high temperatures, prone to agglomeration failure, and insufficient adhesion to the formation interface. These drawbacks are particularly pronounced under high-temperature conditions, making long-term, stable plugging difficult.

[0004] Chinese patent document CN109207131A proposes a method of strengthening the wellbore wall by polymerizing olefin monomers and cross-linking agents to generate a polymer gel. However, when the formation temperature exceeds 150°C, the strength of the gel material often decreases significantly, seriously affecting its stabilization effect.

[0005] The epoxy resin-type cemented wellbore reinforcement disclosed in Chinese patent document CN109423263A has certain bonding and curing strength under conventional formation conditions. However, during ultra-deep drilling, when the formation temperature exceeds 200°C or even higher, the cured epoxy resin plugging agent exhibits increased brittleness and a significant decrease in toughness. Under the continuous collision between the drill pipe and the wellbore wall, cracks or debris are easily generated, causing the wellbore wall to become unstable again.

[0006] At present, existing wellbore reinforcement agents have the following disadvantages: (1) insufficient temperature resistance and cannot be applied to ultra-deep and ultra-deep formations; (2) insufficient bonding strength and difficulty in effectively enhancing the mechanical properties of the rock surface; (3) insufficient sealing performance and uneven particle size distribution, making it difficult to form a stable sealing structure in microcracks and micropores.

[0007] Therefore, there is an urgent need to develop a wellbore strengthening agent that is suitable for drilling operations in deep and ultra-deep formations and has excellent temperature resistance and plugging performance. Summary of the Invention

[0008] In response to the deficiencies of the prior art, the present invention provides a high-temperature resistant 260°C resin-coated sand well wall strengthener, as well as a preparation method and application. The present invention uses a silane coupling agent to modify nano-SiO2 particles, and then uses two high-temperature resistant thermoplastic resins, polyethersulfone (PES) and liquid crystal polymer (LCP), to in-situ coat the modified SiO2 particles to prepare PES-LCP well wall strengthener microspheres. The present invention adjusts the glass transition temperature of the resin system through the synergistic effect of a polyethersulfone (PES) and liquid crystal polymer (LCP) blend system and modified nano-SiO2 particles, significantly improving the bonding strength between the coating and the core surface, ensuring that the plugging and strengthening effect can still be stably exerted under high-temperature conditions of 260°C, thereby effectively overcoming the problem of insufficient well wall strengthening performance of existing well wall strengtheners in deep formations.

[0009] The technical solutions of the present invention are as follows:

[0010] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0011] (1) adding SiO2 nanoparticles to a mixed solvent of anhydrous ethanol and toluene, stirring uniformly, adding a silane coupling agent, stirring uniformly, and reacting; after the reaction is completed, centrifuging, washing, and drying to obtain modified SiO2 particles;

[0012] (2) adding the liquid crystal polymer (LCP) solution to the polyethersulfone (PES) solution and stirring uniformly to obtain a PES-LCP composite resin solution;

[0013] (3) Add the modified SiO2 particles to a mixed solvent of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP), stir and then ultrasonically treat to obtain a dispersion; add the PES-LCP composite resin solution obtained in step (2) to the dispersion, stir evenly, and solidify in steps to obtain a SiO2-PES-LCP composite microsphere reaction liquid; cool, centrifuge, wash, and dry to obtain a high-temperature resistant 260°C resin-coated sand well wall strengthener.

[0014] Preferably, according to the present invention, the particle size of the SiO2 nanoparticles in step (1) is 200-500 nm.

[0015] Preferably, according to the present invention, the volume ratio of anhydrous ethanol to toluene in the mixed solvent in step (1) is 3-6:1, and the ratio of the volume of the mixed solvent to the mass of SiO2 nanoparticles is 4-10mL:1g.

[0016] According to the preferred embodiment of the present invention, the silane coupling agent in step (1) is 3-(methacryloyloxy)propyltrimethoxysilane (KH570) or vinyltriethoxysilane; the mass ratio of the silane coupling agent to the SiO2 nanoparticles is 0.05-0.15:1; after adding the silane coupling agent, the stirring time is 1-3 hours.

[0017] According to the preferred embodiment of the present invention, the reaction temperature in step (1) is 80-100° C., and the reaction time is 2-3 h.

[0018] According to the preferred embodiment of the present invention, the washing in step (1) is performed by sequentially washing with anhydrous ethanol and deionized water once each; and the drying is performed at 100-120° C. for 20-30 h.

[0019] According to the preferred embodiment of the present invention, the liquid crystal polymer (LCP) in step (2) is a thermotropic liquid crystal polymer, which is an aromatic copolyester and a common commercially available product.

[0020] Preferably, according to the present invention, the liquid crystal polymer (LCP) solution in step (2) is prepared according to the following method: heating N-methylpyrrolidone (NMP) to 60-80°C, adding the liquid crystal polymer (LCP) thereto, then heating to 120-150°C, and stirring at a constant temperature for 4-8 hours to obtain a liquid crystal polymer (LCP) solution; the ratio of the mass of the liquid crystal polymer (LCP) to the volume of N-methylpyrrolidone (NMP) is 0.1-0.5g:1mL.

[0021] According to the preferred embodiment of the present invention, the weight average molecular weight of the polyethersulfone (PES) in step (2) is 30,000-150,000, more preferably 40,000-50,000.

[0022] According to the present invention, the polyethersulfone (PES) solution in step (2) is prepared according to the following method: a mixed solvent of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) is heated to 40-60°C, polyethersulfone (PES) is added thereto, and the mixture is stirred at a temperature of 60-80°C and a stirring rate of 600-3000 rpm for 3-6 hours to obtain a polyethersulfone (PES) solution; the volume ratio of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) in the mixed solvent is 6-8:2-4, and the ratio of the mass of the polyethersulfone (PES) to the volume of the mixed solvent is 0.15-0.4 g:1 mL.

[0023] According to the preferred embodiment of the present invention, the mass ratio of the liquid crystal polymer (LCP) in the liquid crystal polymer (LCP) solution to the polyethersulfone (PES) in the polyethersulfone (PES) solution in step (2) is 0.3-1.6:1; the liquid crystal polymer (LCP) solution is added dropwise to the polyethersulfone (PES) solution at a dropping rate of 1-2 drops / s; after the addition is completed, the stirring temperature is 60-80°C and the stirring time is 1-3h.

[0024] Preferably, according to the present invention, the volume ratio of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) in the mixed solvent in step (3) is 6-8:2-4; the ratio of the volume of the mixed solvent to the mass of the modified SiO2 particles is 4-10mL:1g; the modified SiO2 particles are added to the mixed solvent of N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) and stirred for 20-40min, and the ultrasonic treatment time is 20-40min.

[0025] According to the preferred embodiment of the present invention, the mass ratio of the total mass of polyethersulfone (PES) and liquid crystal polymer (LCP) in the PES-LCP composite resin solution in step (3) to the modified SiO2 particles is 1.6-2:1.

[0026] Preferably, according to the present invention, the PES-LCP composite resin solution in step (3) is added dropwise to the dispersion at 80-120° C. at a dropping speed of 0.5-1 mL / min.

[0027] Preferably, according to the present invention, after the PES-LCP composite resin solution is added in step (3), the stirring temperature is 80-120° C. and the stirring time is 4-6 h.

[0028] According to the preferred embodiment of the present invention, the stepwise curing step in step (3) is as follows: firstly heating to 130-150°C and standing to cure for 1-2 hours; and finally heating to 160-180°C and standing to cure for 1-2 hours.

[0029] According to the preferred embodiment of the present invention, the cooling step in step (3) is: cooling to room temperature at a cooling rate of 2-5°C / min; the washing is washing with anhydrous ethanol and deionized water once each in sequence; and the drying is vacuum drying at 70-100°C for 20-30h.

[0030] The present invention also provides a high-temperature resistant 260° C. resin-coated sand well wall strengthener, which is prepared by the above-mentioned preparation method.

[0031] According to the present invention, the application of the above-mentioned high temperature resistant 260°C resin coated sand well wall strengthener is used to stabilize the well wall of deep and ultra-deep fractured formations, and the depth of deep and ultra-deep fractured formations is ≥8000m.

[0032] Room temperature in the present invention has a well-known meaning, which refers to 25±5°C.

[0033] The technical features and beneficial effects of the present invention are as follows:

[0034] 1. The present invention first uses the silane coupling agent 3-(methacryloyloxy)propyltrimethoxysilane (KH570) or vinyltriethoxysilane to couple and modify the surface of SiO2 particles, significantly improving the interfacial bonding ability between SiO2 and the resin; then uses two high-temperature resistant thermoplastic resins, polyethersulfone (PES) and liquid crystal polymer (LCP), to in-situ coat the modified SiO2 particles to prepare SiO2-PES-LCP well wall reinforcement microspheres. Compared with a single resin system, the PES-LCP blended resin in the present invention not only has a suitable glass transition temperature and excellent shear strength, but also has both rigidity and toughness, and has stronger interfacial bonding with SiO2 particles and better dispersion stability, effectively improving the sealing performance and temperature resistance stability. In addition, the well wall reinforcement microspheres prepared by in-situ polymerization have uniform particle size and regular morphology, can achieve efficient well wall sealing and mechanical strengthening, and are suitable for drilling operations under complex well conditions at 260°C.

[0035] 2. The present invention improves the glass transition temperature and high-temperature shear stability of the resin system through the synergistic effect of the polyethersulfone (PES) and liquid crystal polymer (LCP) blend system and modified micron SiO2 particles, significantly improves the bonding strength between the coating and the core surface, and ensures that it can still stably exert the plugging and enhancement effect under high temperature conditions of 260°C. Therefore, the well wall strengthener of the present invention has excellent high-temperature resistance, and the PES-LCP system has a stable temperature resistance of ≥260°C, which is suitable for ultra-high temperature well wall plugging; the plugging performance is enhanced, nano-SiO2 replaces quartz sand, the filling is more uniform, and the crack plugging effect is improved.

[0036] 3. The well wall strengthening agent of the present invention has strong construction adaptability and does not require high-temperature cross-linking and curing, thereby improving construction efficiency; the interfacial bonding strength is enhanced, and the double-bond silane coupling agent enhances the bonding between PES-LCP and nano-SiO2 particles, thereby improving durability; it has excellent chemical stability and is resistant to acid and alkali corrosion, making it suitable for well wall plugging in complex formations. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific examples, but is not limited thereto.

[0038] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials used are commercially available unless otherwise specified.

[0039] The polyethersulfone (PES) used in the examples has a weight average molecular weight of 50,000 and is available from Wanli Plastics Materials Co., Ltd.

[0040] The liquid crystal polymer (LCP) is an aromatic copolyester copolymerized with p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and condensation monomers of terephthalic acid and p-hydroxyphenylacetic acid (HBA / HNA / TBA). The model is JUNLON LCPJ1000, with a melting range of 270°C-330°C. It is available from CGN Juner New Materials Co., Ltd.

[0041] The particle size of the SiO2 particles used in the examples is 300-400 nm.

[0042] Example 1

[0043] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0044] 1. SiO2 particle modification:

[0045] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0046] 2. Preparation of PES-LCP composite resin solution:

[0047] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 50 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 15 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0048] 3. In-situ lamination:

[0049] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0050] Example 2

[0051] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0052] 1. SiO2 particle modification:

[0053] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0054] 2. Preparation of PES-LCP composite resin solution:

[0055] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 45 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 20 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0056] 3. In-situ lamination:

[0057] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0058] Example 3

[0059] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0060] 1. SiO2 particle modification:

[0061] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0062] 2. Preparation of PES-LCP composite resin solution:

[0063] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 40 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 25 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0064] 3. In-situ lamination:

[0065] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0066] Example 4

[0067] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0068] 1. SiO2 particle modification:

[0069] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0070] 2. Preparation of PES-LCP composite resin solution:

[0071] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 35 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 30 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0072] 3. In-situ lamination:

[0073] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0074] Example 5

[0075] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0076] 1. SiO2 particle modification:

[0077] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0078] 2. Preparation of PES-LCP composite resin solution:

[0079] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 30 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 35 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0080] 3. In-situ lamination:

[0081] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0082] Example 6

[0083] A method for preparing a high-temperature resistant 260°C resin-coated sand well wall strengthening agent comprises the following steps:

[0084] 1. SiO2 particle modification:

[0085] Take 40g of SiO2 particles and add them to 250mL of mixed solvent (the mixed solvent is obtained by mixing anhydrous ethanol and toluene in a volume ratio of 4:1), stir evenly, add 4g of 3-(methacryloyloxy)propyltrimethoxysilane, and stir for 2h; then heat to 80℃ and react at 80℃ for 2.5h; after the reaction is completed, centrifuge the reaction solution, and wash the obtained solid with anhydrous ethanol and deionized water once each, and dry the washed solid at 100℃ for 24h to obtain modified SiO2 particles.

[0086] 2. Preparation of PES-LCP composite resin solution:

[0087] In a three-necked flask, 150 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3) was added, heated to 50°C and stirred for 30 minutes to obtain a uniform mixed solvent, and then 25 g of polyethersulfone (PES) was added to the mixed solvent, heated to 70°C, and stirred at 70°C and a stirring rate of 2000 rpm for 4 hours to obtain a polyethersulfone (PES) solution; 40 g of liquid crystal polymer (LCP) was added to 80°C NMP (80 mL), then heated to 130°C, and stirred at 130°C for 6 hours to obtain a liquid crystal polymer (LCP) solution; subsequently, the liquid crystal polymer (LCP) solution was added dropwise to the polyethersulfone (PES) solution at a drop rate of 1 drop / s; after the addition was completed, stirred at 70°C for 2 hours to form a uniform PES-LCP composite resin solution.

[0088] 3. In-situ lamination:

[0089] 35 g of the modified SiO2 particles obtained in step (1) were added to 200 mL of a mixed solvent (the mixed solvent was obtained by mixing DMAc and NMP in a volume ratio of 7:3), stirred for 30 min, and then ultrasonically treated (40 kHz, 30 min) to ensure that the SiO2 particles were uniformly dispersed to obtain a dispersion; the obtained dispersion was heated to 120°C at a heating rate of 5°C / min, and the PES-LCP composite resin solution obtained in step (2) was added dropwise to the dispersion at a rate of 0.8 mL / min at 120°C and 800 rpm. After the dropwise addition was completed, the mixture was stirred at 120°C for 5 h to allow the resin to uniformly coat the SiO2 particles; the mixture was then heated to 140°C at a heating rate of 5°C / min, allowed to stand for 2 h for preliminary curing, and then heated to 170°C at a heating rate of 5°C / min, allowed to stand for 1.5 h. After the curing was completed, the sample was slowly cooled to room temperature at a cooling rate of 2°C / min to prevent the microspheres from cracking due to thermal stress. Finally, the solid was collected by centrifugation (3000 rpm, 10 min), washed once with anhydrous ethanol and once with deionized water, and dried in vacuum at 80°C for 24 h to obtain stable SiO2-PES-LCP composite microspheres, which are high-temperature resistant 260°C resin-coated sand well wall strengtheners.

[0090] Comparative Example 1

[0091] Polyethersulfone (PES) is directly used as a well wall strengthener.

[0092] Comparative Example 2

[0093] Liquid crystal polymer (LCP) is directly used as a well wall strengthener.

[0094] Comparative Example 3

[0095] A method for preparing a well wall strengthening agent is as described in Example 1, except that liquid crystal polymer (LCP) is not added in step (2), and an equal mass of polyethersulfone (PES) is used instead.

[0096] Comparative Example 4

[0097] A method for preparing a well wall strengthening agent is as described in Example 1, except that: in step (2), polyethersulfone (PES) is not added and an equal mass of liquid crystal polymer (LCP) is used instead.

[0098] Comparative Example 5

[0099] A method for preparing a well wall strengthening agent is as described in Example 1, except that the SiO2 particles are not modified in step (1), and unmodified SiO2 particles are directly used in step (3).

[0100] Comparative Example 6

[0101] A method for preparing a well wall strengthening agent is as described in Example 1, except that the silane coupling agent used in step (1) is γ-aminopropyltriethoxysilane.

[0102] Comparative Example 7

[0103] A method for preparing a well wall strengthening agent is as described in Example 1, except that the silane coupling agent used in step (1) is trimethoxysilane.

[0104] Comparative Example 8

[0105] A method for preparing a well wall strengthening agent is as described in Example 1, except that in step (3), the amount of modified nano-SiO2 added is 15g.

[0106] Comparative Example 9

[0107] A method for preparing a well wall strengthening agent is as described in Example 1, except that in step (3), the amount of modified nano-SiO2 added is 45g.

[0108] Test example

[0109] The following performance evaluations were performed on the well wall strengtheners prepared in the examples and comparative examples:

[0110] (1) Effect of resin-coated sand wellbore strengthener on drilling fluid energy before and after aging at 260°C

[0111] Preparation of base slurry: Slowly add 16 g of bentonite to 400 mL of distilled water while stirring, and then hydrate at room temperature for 24 hours to prepare bentonite base slurry.

[0112] Sample preparation: Take 400 mL of base slurry respectively, add 2% (8 g) of the product of Example and Comparative Example, and stir at 3000 r / min for 20 min.

[0113] Performance testing: According to GB / T29170-2012, Laboratory Testing of Drilling Fluids in the Petroleum and Natural Gas Industry, the fluid loss at room temperature and pressure, the fluid loss at high temperature and high pressure at 260°C and 3.5 MPa, and the rheological parameters of the base slurry (apparent viscosity, plastic viscosity, and dynamic shear force) after aging at 260°C for 16 hours were tested. The experimental results are shown in Table 1.

[0114] Table 1 Rheological filtration properties of drilling fluids with wellbore reinforcement

[0115]

[0116]

[0117]

[0118] The results in Table 1 show that the well wall strengthening agent prepared by Examples 1-6 of the present invention has little effect on the rheological properties of the base slurry before and after hot rolling at 260°C for 16 hours, and effectively reduces the API fluid loss (FL API ) and high temperature and high pressure fluid loss (FL HTHP ). It still maintains good performance stability under the conditions of 260°C and aging for 16 hours. Specifically, the apparent viscosity (AV) of Examples 1-6 is maintained at 9.5-10.5 mPa·s, and the dynamic shear force (YP) is controlled between 1-2 Pa, indicating that the system has not undergone serious viscosity increase and the rheological properties are stable; at the same time, the filtration loss at room temperature and pressure is controlled between 27.5-33 mL, and the filtration loss at high temperature and high pressure is controlled between 41-52.5 mL, which is significantly better than the base slurry, showing good filtration loss reduction effect and thermal stability. This shows that the SiO2-PES-LCP system adopted in the present invention has little effect on the rheological properties of the base slurry flow, and can effectively reduce the filtration loss, which is beneficial to improving the stability of the well wall.

[0119] In contrast, Comparative Examples 1-9, under the same high-temperature aging conditions, generally experienced performance degradation and increased viscosity, with AV ranging from 12.5 to 14.5 mPa·s, unstable dynamic shear forces, and YP in some systems dropping to 0.5 Pa, indicating structural damage or gelation. Furthermore, fluid loss increased to 39-48 mL at room temperature and as high as 60.5-75 mL at high temperature, significantly reducing fluid loss performance and failing to effectively control drilling fluid loss.

[0120] (2) Particle size

[0121] 400 mL of an aqueous solution of each sample of the embodiment and the comparative example with a mass fraction of 3% was prepared, ultrasonically dispersed for 30 min, and the sample solution was placed in an aging tank and aged at 260 ° C for 16 h. After aging, it was cooled to room temperature and the particle size of the resin-coated sand well wall strengthener in the aged sample solution was measured using an ultra-high-speed intelligent particle size analyzer. The test results are shown in Table 2.

[0122] Table 2 Particle size of resin coated sand well wall strengthener (unit / μm)

[0123]

[0124]

[0125] As shown in Table 2, in the comparative examples, the particle size distribution is significantly affected by the resin type and filler properties. When only PES or LCP is used (Comparative Examples 1 and 2), the particle size is larger due to the lack of synergy. Unmodified silica (Comparative Example 5) is prone to agglomeration and has poor compatibility with the resin, resulting in higher D50 and D90 values. In contrast, after the introduction of modified silica (such as Comparative Examples 3, 4, 6, and 7), the dispersibility is enhanced and the particle size is significantly reduced. With the increase in the amount of modified SiO2, the particle size becomes further reduced. Since the amount of silica used is greater, the nucleation sites are more, and the resin is dispersed on multiple modified silica surfaces, limiting the growth size of individual particles. Therefore, in Comparative Example 9, a high content of nano-SiO2 is added, and the D50 drops to 4.6 μm and the D90 is within 9 μm. Overall, the SiO2-PES-LCP particle size in the examples is between 6 and 14.5 μm, which can block micron-sized pores.

[0126] (3) Sealing performance of resin-coated sand well wall strengthener

[0127] 2% by mass of each example and comparative example sample was added to 400 mL of base slurry. Following the medium-pressure fluid loss test procedure, the conventional drilling fluid filter paper was replaced with a polytetrafluoroethylene (PTFE) microporous membrane with a pore size of 2 μm, designated PTFE-2. The blocking performance of the sample solution on the PTFE microporous membrane was measured. The experimental results are shown in Table 3.

[0128] Table 3 Blocking performance of microporous membranes in various embodiments and comparative examples

[0129]

[0130]

[0131] The data in the table show that the filter loss of the well wall strengthening agents prepared in Examples 1-6 and Comparative Examples 1-9 on the 2μm PTFE microporous filter membrane is much lower than the API filter loss of each, indicating that the particles used can form a dense filter cake with excellent micropore plugging performance. 50 In the range of 6-10μm, the larger the particle size, the better the bridging effect and the smaller the filtration loss; D 50 When the particle size is smaller than 4 μm or larger than 18 μm, effective plugging is difficult and the fluid loss increases. The overall fluid loss of the examples is significantly lower than that of all the comparative examples, further demonstrating that the SiO2-PES-LCP proposed in this invention can utilize the triple synergistic effect of "modified SiO2 particle skeleton + PES film-forming properties + LCP mechanical support" to ensure particle dispersion and enhance the resin coating effect, thereby achieving efficient plugging.

[0132] Comparative Examples 1 and 2 only add single resin (PES or LCP), both lacking inorganic skeletons and also lacking synergy between resins, and the plugging layer is loose, and the fluid loss is high. Although Comparative Examples 3 and 4 add modified SiO 2 , still using a single resin system, it is difficult to form an interpenetrating network structure, causing fluid loss to be still higher. SiO 2 in Comparative Example 5 is not processed with hydrophobic silane, and particle and resin compatibility are poor, and it is difficult to be evenly coated by resin, and the plugging layer is not dense, and fluid loss is large. Comparative Example 6 adopts aminosilane modification, and amino polarity is strong, increases particle hydrophilicity, weakens the interface bonding with hydrophobic resin, and plugging effect is limited. Comparative Example 7 uses methoxysilane to give particle hydrophobicity, but methyl is unreactive, and is difficult to be chemically bonded with resin, and fluid loss increases. Comparative Examples 8 and 9 only changed the amount of modified SiO2 added: when SiO2 was excessive (Comparative Example 9), there were more nucleation sites, the particle size of the microspheres was relatively small, they could better enter the micropores and form filter cakes, and the filtration loss was relatively low; when the SiO2 content was insufficient and the particle size was relatively large (Comparative Example 8), the particles were difficult to embed into the pores of the filter membrane, the gaps in the sealing layer were large, and the filtration loss was the highest.

[0133] (4) Glass transition temperature of resin-coated sand

[0134] The shear strength of core slices coated with PES-LCP wellbore reinforcement at 260°C was evaluated using a high- and low-temperature electronic universal testing machine. First, standard core slices with a diameter of 25 mm and a height of 10 mm were surface treated and evenly coated with the wellbore reinforcement. The resin-coated core slices were then placed in a hot press and hot-pressed at 280°C and 2 MPa for 30 minutes to melt the resin and fully penetrate the core surface, resulting in a uniform and dense reinforcement coating. After hot pressing, the samples were placed in a high-temperature furnace at 260°C for 16 hours. After removal, they were transferred to the temperature-controlled chamber of the high- and low-temperature electronic universal testing machine and maintained at 260°C. Shear loading was applied using a double-sided shear fixture at a rate of 0.5 mm / min. The maximum shear failure load, F (N), was recorded, and the shear strength, τ (MPa), was calculated as F / A, where A is the shear area. By comparing the examples and comparative examples, the enhancement effects of different SiO2-PES-LCP composite formulas on the core bonding and wall reinforcement performance were evaluated, and the high-temperature shear stability of the well wall strengthener was determined.

[0135] Table 4 Effect of glass transition temperature of well wall reinforcement on shear strength in Examples and Comparative Examples

[0136] sample Glass transition temperature (Tg, ℃) Shear strength (MPa) Example 1 245.0 3.0 Example 2 248.0 3.4 Example 3 252.0 3.8 Example 4 255.0 4.0 Example 5 258.0 4.1 Example 6 260.0 4.2 Comparative Example 1 230.0 1.0 Comparative Example 2 232.0 1.3 Comparative Example 3 234.0 1.4 Comparative Example 4 236.0 1.5 Comparative Example 5 238.0 1.6 Comparative Example 6 239.0 1.7 Comparative Example 7 240.0 1.8 Comparative Example 8 235.0 1.5 Comparative Example 9 230.0 1.0

[0137] As can be seen from Table 4, in terms of glass transition temperature (Tg), Examples 1-6 all have Tg above 245°C, with the highest reaching 260°C, demonstrating excellent thermal stability and the ability to maintain the integrity of the material structure under high-temperature conditions. The synergistic effect of the PES and LCP components in the system, coupled with the inorganic reinforcement of SiO2, ensures that the material maintains good phase stability even in high-temperature environments. In particular, after exceeding Tg, the molecular segments begin to undergo thermal motion, and the material gradually transforms from a glassy state to a highly elastic state, possessing a certain degree of plasticity and fluidity, which is conducive to deformation, sealing microcracks in the wellbore wall, and achieving bonding and consolidation.

[0138] In terms of shear strength, the examples all achieved strengths above 3.0 MPa, with the highest reaching 4.2 MPa, significantly exceeding the 1.0-1.8 MPa of the comparative examples. This demonstrates that the composite modification system employed not only maintains strong structural integrity at high temperatures but also enhances the material's bonding properties and mechanical strength through the movement and synergy between molecular segments, forming a denser and more stable sealing structure and enhancing the sealing layer's resistance to shear and thermal shock.

[0139] A comprehensive comparison shows that the comparative examples, due to a lack of coordinated design, generally have low glass transition temperatures, are susceptible to structural damage at high temperatures, and have significantly insufficient shear strength, making them difficult to meet the application requirements of high-temperature downhole operations. The SiO2-PES-LCP composite wellbore reinforcement proposed in this invention not only has a high Tg and strong thermal stability, but also achieves effective deformation, sealing, and bonding through segmental thermal motion at actual operating temperatures. Its overall performance is superior, making it suitable for stabilizing wellbore walls in high-temperature, complex downhole environments.

Claims

1. A method for preparing a high temperature resistant 260°C resin coated sand well wall strengthening agent, characterized in that: The steps are as follows: (1) adding SiO2 nanoparticles to a mixed solvent of anhydrous ethanol and toluene, stirring uniformly, adding a silane coupling agent, stirring uniformly, and reacting; after the reaction is completed, centrifuging, washing, and drying to obtain modified SiO2 particles; (2) adding the liquid crystal polymer solution to the polyethersulfone solution and stirring uniformly to obtain a PES-LCP composite resin solution; (3) Adding the modified SiO2 particles to a mixed solvent of N,N-dimethylacetamide and N-methylpyrrolidone, stirring and ultrasonically treating to obtain a dispersion; adding the PES-LCP composite resin solution obtained in step (2) to the dispersion, stirring evenly, and curing in steps to obtain a SiO2-PES-LCP composite microsphere reaction liquid; cooling, centrifuging, washing, and drying to obtain a high-temperature resistant 260°C resin-coated sand well wall strengthener.

2. The preparation method of the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The particle size of the SiO2 nanoparticles in step (1) is 200-500nm; the volume ratio of anhydrous ethanol and toluene in the mixed solvent is 3-6:1, and the ratio of the volume of the mixed solvent to the mass of the SiO2 nanoparticles is 4-10mL:1g.

3. The preparation method of the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The silane coupling agent in step (1) is 3-(methacryloyloxy)propyltrimethoxysilane or vinyltriethoxysilane; the mass ratio of the silane coupling agent to the SiO2 nanoparticles is 0.05-0.15:1; after adding the silane coupling agent, the stirring time is 1-3 hours; The reaction temperature is 80-100° C., and the reaction time is 2-3 hours. The washing is performed by sequentially using anhydrous ethanol and deionized water for one wash each. The drying is performed at 100-120° C. for 20-30 hours.

4. The preparation method of the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The liquid crystal polymer in step (2) is a thermotropic liquid crystal polymer, which is an aromatic copolyester; the liquid crystal polymer solution is prepared according to the following method: heating N-methylpyrrolidone to 60-80°C, adding the liquid crystal polymer thereto, then heating to 120-150°C, and stirring at a constant temperature for 4-8 hours to obtain a liquid crystal polymer solution; the ratio of the mass of the liquid crystal polymer to the volume of N-methylpyrrolidone is 0.1-0.5g:1mL.

5. The method for preparing the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The weight average molecular weight of the polyethersulfone in step (2) is 30,000-150,000, preferably 40,000-50,000; the polyethersulfone solution is prepared according to the following method: heating a mixed solvent of N,N-dimethylacetamide and N-methylpyrrolidone to 40-60° C., adding polyethersulfone thereto, and stirring at a temperature of 60-80° C. and a stirring rate of 600-1000 rpm for 3-6 hours to obtain a polyethersulfone solution; the volume ratio of N,N-dimethylacetamide and N-methylpyrrolidone in the mixed solvent is 6-8:2-4, and the ratio of the mass of the polyethersulfone (PES) to the volume of the mixed solvent is 0.15-0.4 g:1 mL.

6. The method for preparing the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The mass ratio of the liquid crystal polymer in the liquid crystal polymer solution to the polyethersulfone in the polyethersulfone solution in step (2) is 0.3-1.6:1; the liquid crystal polymer solution is added dropwise to the polyethersulfone solution at a dropping rate of 1-2 drops / s; after the dropwise addition is completed, the stirring temperature is 60-80°C and the stirring time is 1-3h.

7. The method for preparing the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: The volume ratio of N,N-dimethylacetamide and N-methylpyrrolidone in the mixed solvent in step (3) is 6-8:2-4; the volume ratio of the mixed solvent to the mass of the modified SiO2 particles is 4-10 mL:1 g; the modified SiO2 particles are added to the mixed solvent of N,N-dimethylacetamide and N-methylpyrrolidone and stirred for 20-40 minutes, and the ultrasonic treatment time is 20-40 minutes; The mass ratio of the total mass of polyethersulfone and liquid crystal polymer in the PES-LCP composite resin solution to the modified SiO2 particles is 1.6-2:1; The PES-LCP composite resin solution is added dropwise into the dispersion at 80-120° C. at a dropping speed of 0.5-1 mL / min.

8. The method for preparing the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 1, characterized in that: After the PES-LCP composite resin solution in step (3) is added, the stirring temperature is 80-120° C. and the stirring time is 4-6 hours; The step-by-step curing steps are: first, heating to 130-150° C. and allowing to stand for curing for 1-2 hours; finally, heating to 160-180° C. and allowing to stand for curing for 1-2 hours; The cooling step comprises: cooling to room temperature at a rate of 2-5°C / min; the washing comprises washing with anhydrous ethanol and deionized water once each; and the drying comprises vacuum drying at 70-100°C for 20-30h.

9. A high temperature resistant 260°C resin coated sand well wall strengthener, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. The use of the high temperature resistant 260°C resin coated sand well wall strengthening agent according to claim 9, characterized in that: Used to stabilize the wellbore wall in deep and ultra-deep fractured formations. The depth of the well in deep and ultra-deep fractured formations is ≥8000m.

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