Alkali-resistant resin coated quartz fracturing sand for oil field and preparation method of alkali-resistant resin coated quartz fracturing sand

Abstract

The invention relates to the technical field of quartz fracturing sand, in particular to alkali-resistant resin coated quartz fracturing sand for oil fields and a preparation method thereof.The alkali-resistant resin coated quartz fracturing sand is prepared from, by weight, 100 parts of quartz sand base material, 4.2-5.5 parts of alkali-resistant resin and 0.2-0.3 part of calcium stearate, wherein the alkali-resistant resin is prepared from the following raw materials: 40 to 50 parts of bisphenol A epoxy resin, 15 to 20 parts of modified branched polyimide, 1.5 to 3 parts of composite filler, 3.5 to 4.5 parts of phenolic aldehyde amine curing agent, 5 to 8 parts of ethanol, 5 to 8 parts of acetone, 0.4 to 0.6 part of defoaming agent and 0.6 to 0.8 part of flatting agent. And the composite filler containing the three-dimensional interlayer structure is added, so that the problems that the breakage rate of the quartz fracturing sand is increased and the permeability loss rate is relatively high due to the fact that the resin layer of the existing resin-coated quartz fracturing sand is degraded under the long-term alkaline condition are solved.

Description

Technical Field

[0001] The invention relates to the technical field of quartz fracturing sand, and in particular to quartz fracturing sand coated with an alkali-resistant resin for oil fields and a preparation method thereof. Background Art

[0002] In oilfield sand control measures, resin-coated quartz fracturing sand is widely used because it can form a high-permeability artificial well wall through consolidation. However, oilfield formation water often contains high concentrations of alkaline substances. Traditional phenolic resin or epoxy resin coatings are prone to hydrolysis, swelling and chemical bond breakage in a long-term alkaline environment, resulting in an increased breakage rate and a high permeability loss rate of the coated fracturing sand, which seriously restricts the use of resin-coated fracturing sand. For example, patent CN116904181A discloses a high-strength coated sand and its preparation method and application, in which high-strength coated fracturing sand is prepared with a specific high-activity polyphenol linear phenolic resin, thereby significantly improving the shear strength of the overall structure formed after curing, but it does not improve the problem of performance degradation of phenolic resin in a long-term alkaline environment. Summary of the invention

[0003] The object of the present invention is to provide an alkali-resistant resin-coated quartz fracturing sand for oil fields and a preparation method thereof. By adding a modified branched polyimide having a siloxane segment and an epoxy group and a composite filler having a three-dimensional interlayer structure into an alkali-resistant resin substrate, the problem of degradation of the resin layer of the existing resin-coated quartz fracturing sand under long-term alkaline conditions, which leads to an increase in the crushing rate of the quartz fracturing sand and a high permeability loss rate, is solved.

[0004] The purpose of the present invention can be achieved by the following technical scheme: a preparation method of alkali-resistant resin coated quartz fracturing sand for oil fields, comprising the following steps: weighing the following raw materials by weight: 100 parts of quartz sand substrate, 4.2-5.5 parts of alkali-resistant resin and 0.2-0.3 parts of calcium stearate, preheating the quartz sand substrate to 80-100°C, adding it to a sand mixer, then adding the alkali-resistant resin, stirring for 15-20 minutes, then adding the calcium stearate, continuing to stir for 15-20 minutes, pouring out, drying, curing at 140°C for 2 hours, cooling, crushing, sieving, and obtaining alkali-resistant resin coated quartz fracturing sand for oil fields; The quartz sand substrate is 80 mesh quartz sand from Yongshun Mining Products; The alkali-resistant resin is prepared by the following steps: weighing the following raw materials in parts by weight: 40-50 parts of bisphenol A epoxy resin, 15-20 parts of modified branched polyimide, 1.5-3 parts of composite filler, 3.5-4.5 parts of phenolic amine curing agent, 5-8 parts of ethanol, 5-8 parts of acetone, 0.4-0.6 parts of defoaming agent and 0.6-0.8 parts of leveling agent, mixing the bisphenol A epoxy resin, modified branched polyimide, composite filler, phenolic amine curing agent, ethanol, acetone, defoaming agent and leveling agent to prepare the alkali-resistant resin; The bisphenol A epoxy resin is the bisphenol A epoxy resin of Baling Petrochemical Co., Ltd. The phenalkamine curing agent is DMP-30; The defoamer is BYK-066N; The leveling agent is BYK-306; The modified branched polyimide is prepared by the following steps: Step A1: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone were mixed, and the mixture was reacted for 4-6 hours under nitrogen protection, at a stirring rate of 140-180 rpm and a temperature of 25-30° C., and then vacuum dried at a temperature of 140° C. for 1 hour, and then vacuum dried at a temperature of 240° C. for 1 hour to obtain intermediate 1; The dosage ratio of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone is 0.012-0.013 mol: 0.024-0.025 mol: 25-30 mL; During the reaction, in N-methylpyrrolidone, the amino group in 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane reacts with the anhydride group in 1,2,4-tricarboxylic anhydride to form an amide structure, which is then imidized at temperatures of 140°C and 240°C to obtain an intermediate 1 with carboxyl groups at both ends. Step A2: Mix the intermediate 1, trimethylolpropane and dimethylacetamide, stir at a stirring rate of 180-240 rpm and a temperature of 35-40° C., add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react for 10-12 hours, distill under reduced pressure, wash, and dry to obtain a branched polyimide; mix the branched polyimide, epichlorohydrin and dimethylacetamide, stir at a stirring rate of 180-240 rpm and a temperature of 65-68° C., react for 6-7 hours, distill under reduced pressure, add toluene and sodium hydroxide, cool to 25-30° C., continue to react for 6-7 hours, distill under reduced pressure, and dry to obtain a modified branched polyimide; The amount ratio of intermediate 1, trimethylolpropane, dimethylacetamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2.4-2.6g: 0.6-0.7g: 45-50mL: 1-1.1g: 0.05-0.06g; the amount ratio of branched polyimide, epichlorohydrin, dimethylacetamide, toluene and sodium hydroxide is 1.8-2.2g: 0.45-0.5g: 25-30mL: 8-10mL: 0.3-0.4g; During the reaction, under the action of dicyclohexylcarbodiimide and 4-dimethylaminopyridine, the hydroxyl group in trimethylolpropane reacts with the terminal carboxyl group in the intermediate 1 to undergo esterification, thereby forming a carboxyl-terminated branched structure to obtain a branched polyimide. The carboxyl group in the branched polyimide then reacts with epichlorohydrin, and sodium hydroxide is added to close the ring to form an epoxy group to obtain a modified branched polyimide.

[0005] The composite filler is prepared by the following steps: Step B1: Mix the carbon nanotubes and deionized water and disperse them ultrasonically for 15-20 minutes, then stir and add hexadecyltrimethylammonium bromide at a stirring rate of 120-140 rpm at room temperature, stir for 30-40 minutes, then add sodium molybdate dihydrate and thiourea, continue stirring for 15-20 minutes, transfer them into a reactor, react at a temperature of 180-210° C. for 24 hours, cool, centrifuge, dry, and then sinter for 2 hours at a temperature of 800° C. under nitrogen protection to obtain a precursor; The ratio of carbon nanotubes, deionized water, hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and thiourea is 0.1-0.12 g: 75-80 mL: 0.52-0.55 g: 0.72-0.73 g: 1.2-1.3 g; During the reaction and stirring process, since the hexadecyltrimethylammonium ions are positively charged and the molybdate ions are negatively charged, they attract and chelate each other under the action of electrostatic force, and during the hydrothermal reaction, the molybdate ions react with thiourea to form molybdenum disulfide and attach to the carbon nanotubes, and grow and agglomerate with the carbon nanotubes as templates, thereby forming a product with a three-dimensional interlayer structure. At the same time, due to the doping of hexadecyltrimethylammonium bromide, it forms defect sites between the molybdenum disulfide layers after calcination and carbonization, thereby preparing a precursor; The carbon nanotubes are Shanghai Gaibang Industrial W-600; Step B2: triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol and deionized water are mixed, stirred at a stirring rate of 120-140 rpm and a temperature of 60°C, and a precursor is added, reacted for 2-3 hours, filtered, washed, and dried to obtain a silane-modified precursor, and the silane-modified precursor, Tris-HCl buffer solution and ethanol solution are mixed, ultrasonically dispersed for 15-20 minutes, and then stirred at a stirring rate of 120-140 rpm and a temperature of 60°C and dopamine hydrochloride is added, reacted for 4-6 hours, centrifuged, washed, and dried to obtain a composite filler; The dosage ratio of triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol, deionized water and precursor is 0.05-0.08g: 30-35mL: 4-6mL: 2.3-2.5g; the mass concentration of Tris-HCl buffer solution is 1.6g / L, pH=8.5, the volume concentration of ethanol solution is 75%, and the dosage ratio of silane-modified precursor, Tris-HCl buffer solution, ethanol solution and dopamine hydrochloride is 1.2-1.4g: 15-20mL: 45-50mL: 0.4-0.42g; During the reaction, the precursor is modified by triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane to introduce a perfluorinated chain segment to obtain a silane-modified precursor, and then dopamine is polymerized on the surface of the silane-modified precursor in a Tris-HCl buffer solution and an ethanol solution to form a polydopamine layer to obtain a composite filler; Beneficial effects of the invention: The invention discloses an alkali-resistant resin-coated quartz fracturing sand for oil fields and a preparation method thereof. By adding a modified branched polyimide having a siloxane chain segment and an epoxy group to an alkali-resistant resin substrate and a composite filler having a three-dimensional interlayer structure, the problem that the resin layer of the existing resin-coated quartz fracturing sand deteriorates under long-term alkaline conditions, resulting in an increased crushing rate of the quartz fracturing sand and a reduced permeability loss rate is solved; during the alkali-resistant resin coating and curing process, the modified branched polyimide itself has a large number of epoxy groups and the presence of its branched structure, so that it can react with the radical epoxy resin and the amine curing agent to form a cross-linked network, and at the same time, due to the presence of its silicone The oxane chain segments make the cured resin layer have good alkali resistance, and also improve the mechanical properties of the resin layer to a certain extent, thereby reducing the crushing rate of quartz fracturing sand. Since the composite filler itself is a three-dimensional interlayer structure, the existence of its special structure can greatly increase the movement distance of alkaline substances in the resin matrix, thereby delaying the damage to the resin matrix. In addition, due to the introduction of perfluorosilane, its alkali resistance is also improved to a certain extent. Due to the presence of the polydopamine layer on its surface, the composite filler has active sites for reacting with the epoxy resin matrix, thereby improving the compatibility of the composite filler with the epoxy resin matrix, thereby further improving the mechanical properties of the quartz fracturing sand resin layer. DETAILED DESCRIPTION

[0006] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0007] Example 1 A method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields, comprising the following steps: weighing the following raw materials in parts by weight: 100 parts of a quartz sand substrate, 4.2 parts of an alkali-resistant resin, and 0.3 parts of calcium stearate, preheating the quartz sand substrate to 80° C., adding the alkali-resistant resin to a sand mixer, adding the alkali-resistant resin, stirring for 15 minutes, adding the calcium stearate, continuing to stir for 15 minutes, pouring out, drying, curing at 140° C. for 2 hours, cooling, crushing, and sieving to obtain quartz fracturing sand coated with an alkali-resistant resin for oil fields; The quartz sand substrate is 80 mesh quartz sand from Yongshun Mining Products; The alkali-resistant resin is prepared by the following steps: weighing the following raw materials in parts by weight: 40 parts of bisphenol A epoxy resin, 15 parts of modified branched polyimide, 1.5 parts of composite filler, 3.5 parts of phenolic amine curing agent, 5 parts of ethanol, 5 parts of acetone, 0.4 parts of defoaming agent and 0.6 parts of leveling agent, mixing the bisphenol A epoxy resin, modified branched polyimide, composite filler, phenolic amine curing agent, ethanol, acetone, defoaming agent and leveling agent to prepare the alkali-resistant resin; The bisphenol A epoxy resin is the bisphenol A epoxy resin of Baling Petrochemical Co., Ltd. The phenalkamine curing agent is DMP-30; The defoamer is BYK-066N; The leveling agent is BYK-306; The modified branched polyimide is prepared by the following steps: Step A1: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone were mixed, and the mixture was reacted for 4 h under nitrogen protection, at a stirring rate of 140 rpm and a temperature of 25° C., and then vacuum dried at a temperature of 140° C. for 1 h, and then vacuum dried at a temperature of 240° C. for 1 h to obtain intermediate 1; The dosage ratio of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone is 0.012 mol:0.024 mol:25 mL; Step A2: Mix the intermediate 1, trimethylolpropane and dimethylacetamide, stir at a stirring rate of 180 rpm and a temperature of 35° C., add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react for 10 hours, distill under reduced pressure, wash, and dry to obtain a branched polyimide; mix the branched polyimide, epichlorohydrin and dimethylacetamide, stir at a stirring rate of 180 rpm and a temperature of 65° C., react for 6 hours, distill under reduced pressure, add toluene and sodium hydroxide, cool to 25° C., continue to react for 6 hours, distill under reduced pressure, and dry to obtain a modified branched polyimide; The amount ratio of intermediate 1, trimethylolpropane, dimethylacetamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2.4g:0.6g:45mL:1g:0.05g; the amount ratio of branched polyimide, epichlorohydrin, dimethylacetamide, toluene and sodium hydroxide is 1.8g:0.45g:25mL:8mL:0.3g; The composite filler is prepared by the following steps: Step B1: Mix the carbon nanotubes and deionized water and disperse them ultrasonically for 20 minutes, then stir and add hexadecyltrimethylammonium bromide at a stirring rate of 120 rpm and room temperature, stir for 40 minutes, then add sodium molybdate dihydrate and thiourea, continue stirring for 15 minutes, transfer it into a reactor, react at a temperature of 210°C for 24 hours, cool, centrifuge, dry, and then sinter for 2 hours at a temperature of 800°C under nitrogen protection to obtain a precursor; The amount ratio of carbon nanotubes, deionized water, hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and thiourea is 0.1 g: 80 mL: 0.52 g: 0.73 g: 1.2 g; The carbon nanotubes are Shanghai Gaibang Industrial W-600; Step B2: triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol and deionized water are mixed, stirred at a stirring rate of 140 rpm and a temperature of 60°C, and a precursor is added, reacted for 2 hours, filtered, washed, and dried to obtain a silane-modified precursor, and the silane-modified precursor, Tris-HCl buffer solution and ethanol solution are mixed, ultrasonically dispersed for 20 minutes, and then stirred at a stirring rate of 120 rpm and a temperature of 60°C and dopamine hydrochloride is added, reacted for 6 hours, centrifuged, washed, and dried to obtain a composite filler; The dosage ratio of triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, ethanol, deionized water and precursor is 0.05g:35mL:4mL:2.3g; the mass concentration of Tris-HCl buffer solution is 1.6g / L, pH=8.5, the volume concentration of ethanol solution is 75%, and the dosage ratio of silane-modified precursor, Tris-HCl buffer solution, ethanol solution and dopamine hydrochloride is 1.4g:15mL:50mL:0.4g.

[0008] Example 2 A method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields, comprising the following steps: weighing the following raw materials in parts by weight: 100 parts of a quartz sand substrate, 5.5 parts of an alkali-resistant resin and 0.2 parts of calcium stearate, preheating the quartz sand substrate to 80°C, adding it to a sand mixer, then adding the alkali-resistant resin, stirring for 20 minutes, then adding the calcium stearate, continuing to stir for 20 minutes, pouring it out, drying it, curing it at 140°C for 2 hours, cooling it, crushing it, and sieving it to obtain quartz fracturing sand coated with an alkali-resistant resin for oil fields; The quartz sand substrate is 80 mesh quartz sand from Yongshun Mining Products; The alkali-resistant resin is prepared by the following steps: weighing the following raw materials in parts by weight: 40 parts of bisphenol A epoxy resin, 15 parts of modified branched polyimide, 3 parts of composite filler, 4.5 parts of phenolic amine curing agent, 8 parts of ethanol, 5 parts of acetone, 0.6 parts of defoaming agent and 0.6 parts of leveling agent, mixing the bisphenol A epoxy resin, modified branched polyimide, composite filler, phenolic amine curing agent, ethanol, acetone, defoaming agent and leveling agent to prepare the alkali-resistant resin; The bisphenol A epoxy resin is the bisphenol A epoxy resin of Baling Petrochemical Co., Ltd. The phenalkamine curing agent is DMP-30; The defoamer is BYK-066N; The leveling agent is BYK-306; The modified branched polyimide is prepared by the following steps: Step A1: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone were mixed, and the mixture was reacted for 6 h under nitrogen protection, at a stirring rate of 180 rpm and a temperature of 25° C., and then vacuum dried at a temperature of 140° C. for 1 h, and then vacuum dried at a temperature of 240° C. for 1 h to obtain intermediate 1; The dosage ratio of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone is 0.012 mol:0.025 mol:25 mL; Step A2: Mix the intermediate 1, trimethylolpropane and dimethylacetamide, stir at a stirring rate of 240 rpm and a temperature of 35° C., add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react for 12 hours, distill under reduced pressure, wash, and dry to obtain a branched polyimide; mix the branched polyimide, epichlorohydrin and dimethylacetamide, stir at a stirring rate of 180 rpm and a temperature of 68° C., react for 6 hours, distill under reduced pressure, add toluene and sodium hydroxide, cool to 25° C., continue to react for 6 hours, distill under reduced pressure, and dry to obtain a modified branched polyimide; The amount ratio of intermediate 1, trimethylolpropane, dimethylacetamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2.6g: 0.6g: 50mL: 1g: 0.06g; the amount ratio of branched polyimide, epichlorohydrin, dimethylacetamide, toluene and sodium hydroxide is 1.8g: 0.45g: 30mL: 8mL: 0.3g; The composite filler is prepared by the following steps: Step B1: Mix the carbon nanotubes and deionized water and disperse them ultrasonically for 15 minutes, then stir and add hexadecyltrimethylammonium bromide at a stirring rate of 120 rpm and room temperature, stir for 30 minutes, then add sodium molybdate dihydrate and thiourea, continue stirring for 15 minutes, transfer them into a reactor, react at a temperature of 180°C for 24 hours, cool, centrifuge, dry, and then sinter for 2 hours at a temperature of 800°C under nitrogen protection to obtain a precursor; The amount ratio of carbon nanotubes, deionized water, hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and thiourea is 0.1 g:75 mL:0.52 g:0.72 g:1.2 g; The carbon nanotubes are Shanghai Gaibang Industrial W-600; Step B2: triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol and deionized water are mixed, stirred at a stirring rate of 120 rpm and a temperature of 60°C, and a precursor is added, reacted for 2 hours, filtered, washed, and dried to obtain a silane-modified precursor, and the silane-modified precursor, Tris-HCl buffer solution and ethanol solution are mixed, ultrasonically dispersed for 15 minutes, and then stirred at a stirring rate of 120 rpm and a temperature of 60°C and dopamine hydrochloride is added, reacted for 4 hours, centrifuged, washed, and dried to obtain a composite filler; The dosage ratio of triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, ethanol, deionized water and precursor is 0.05g:30mL:4mL:2.3g; the mass concentration of Tris-HCl buffer solution is 1.6g / L, pH=8.5, the volume concentration of ethanol solution is 75%, and the dosage ratio of silane-modified precursor, Tris-HCl buffer solution, ethanol solution and dopamine hydrochloride is 1.2g:15mL:45mL:0.4g.

[0009] Example 3 A method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields, comprising the following steps: weighing the following raw materials in parts by weight: 100 parts of a quartz sand substrate, 5.5 parts of an alkali-resistant resin and 0.3 parts of calcium stearate, preheating the quartz sand substrate to 100°C, adding it to a sand mixer, then adding the alkali-resistant resin, stirring for 20 minutes, then adding the calcium stearate, continuing to stir for 20 minutes, pouring it out, drying it, curing it at 140°C for 2 hours, cooling it, crushing it, and sieving it to obtain quartz fracturing sand coated with an alkali-resistant resin for oil fields; The quartz sand substrate is 80 mesh quartz sand from Yongshun Mining Products; The alkali-resistant resin is prepared by the following steps: weighing the following raw materials in parts by weight: 50 parts of bisphenol A epoxy resin, 20 parts of modified branched polyimide, 3 parts of composite filler, 4.5 parts of phenolic amine curing agent, 8 parts of ethanol, 8 parts of acetone, 0.6 parts of defoaming agent and 0.8 parts of leveling agent, mixing the bisphenol A epoxy resin, modified branched polyimide, composite filler, phenolic amine curing agent, ethanol, acetone, defoaming agent and leveling agent to prepare the alkali-resistant resin; The bisphenol A epoxy resin is the bisphenol A epoxy resin of Baling Petrochemical Co., Ltd. The phenalkamine curing agent is DMP-30; The defoamer is BYK-066N; The leveling agent is BYK-306; The modified branched polyimide is prepared by the following steps: Step A1: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone were mixed, and the mixture was reacted for 6 h under nitrogen protection, at a stirring rate of 180 rpm and a temperature of 30° C., and then vacuum dried at a temperature of 140° C. for 1 h, and then vacuum dried at a temperature of 240° C. for 1 h to obtain intermediate 1; The dosage ratio of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone is 0.013 mol:0.025 mol:30 mL; Step A2: Mix the intermediate 1, trimethylolpropane and dimethylacetamide, stir at a stirring rate of 240 rpm and a temperature of 40° C., add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react for 12 hours, distill under reduced pressure, wash, and dry to obtain a branched polyimide; mix the branched polyimide, epichlorohydrin and dimethylacetamide, stir at a stirring rate of 240 rpm and a temperature of 68° C., react for 7 hours, distill under reduced pressure, add toluene and sodium hydroxide, cool to 30° C., continue to react for 7 hours, distill under reduced pressure, and dry to obtain a modified branched polyimide; The amount ratio of intermediate 1, trimethylolpropane, dimethylacetamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2.6g: 0.7g: 50mL: 1.1g: 0.06g; the amount ratio of branched polyimide, epichlorohydrin, dimethylacetamide, toluene and sodium hydroxide is 2.2g: 0.5g: 30mL: 10mL: 0.4g; The composite filler is prepared by the following steps: Step B1: Mix the carbon nanotubes and deionized water and disperse them ultrasonically for 20 minutes, then stir and add hexadecyltrimethylammonium bromide at a stirring rate of 140 rpm and room temperature, stir for 40 minutes, then add sodium molybdate dihydrate and thiourea, continue stirring for 20 minutes, transfer them into a reactor, react at a temperature of 210°C for 24 hours, cool, centrifuge, dry, and then sinter under nitrogen protection at a temperature of 800°C for 2 hours to obtain a precursor; The amount ratio of carbon nanotubes, deionized water, hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and thiourea is 0.12 g: 80 mL: 0.55 g: 0.73 g: 1.3 g; The carbon nanotubes are Shanghai Gaibang Industrial W-600; Step B2: triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol and deionized water are mixed, stirred at a stirring rate of 140 rpm and a temperature of 60°C, and a precursor is added, reacted for 3 hours, filtered, washed, and dried to obtain a silane-modified precursor, and the silane-modified precursor, Tris-HCl buffer solution and ethanol solution are mixed, ultrasonically dispersed for 20 minutes, and then stirred at a stirring rate of 140 rpm and a temperature of 60°C and dopamine hydrochloride is added, reacted for 6 hours, centrifuged, washed, and dried to obtain a composite filler; The dosage ratio of triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, ethanol, deionized water and precursor is 0.08g:35mL:6mL:2.5g; the mass concentration of Tris-HCl buffer solution is 1.6g / L, pH=8.5, the volume concentration of ethanol solution is 75%, and the dosage ratio of silane-modified precursor, Tris-HCl buffer solution, ethanol solution and dopamine hydrochloride is 1.4g:20mL:50mL:0.42g.

[0010] Comparative Example 1 Compared with Example 3, this comparative example is different in that the composite filler in the preparation process of the alkali-resistant resin in Example 3 is replaced by the silane-modified precursor in Example 3, and the other steps are the same.

[0011] Comparative Example 2 Compared with Example 3, this comparative example replaces the composite filler in the preparation process of the alkali-resistant resin in Example 3 with a mixture of Beike Nano MoS2-200nm and Shanghai Gaibang Industrial W-600 carbon nanotubes, wherein the ratio of molybdenum disulfide to carbon nanotubes is 0.2g:0.08g, and the other steps are the same.

[0012] Comparative Example 3 Compared with Example 3, this comparative example removes the modified branched polyimide in the preparation process of the alkali-resistant resin in Example 3, and the other steps are the same.

[0013] The alkali-resistant resin-coated quartz fracturing sand prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested for crushing rate under 50 MPa and 70 MPa conditions with reference to SY / T 5108-2018. The alkali-resistant resin-coated quartz fracturing sand was subjected to alkaline heat aging for 7 days at a temperature of 60°C and a pH of 10, and then its crushing rate was tested to evaluate its alkali resistance. The water phase permeability was measured at a flow rate of 2.0 mL / min using a core flow tester. The core length was 5.2 cm and the core diameter was 2.5 cm. The test results are as follows: Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Broken rate (%) 2.79 2.60 2.57 4.21 4.77 3.28 Breakage rate after alkali heat aging (%) 3.55 3.43 3.21 6.68 8.54 6.07 <![CDATA[Water phase permeability (μm 2 )]]> 1.281 1.272 1.257 1.394 1.593 1.415 It can be seen from the test results in the table shown that when Example 1, Example 2 and Example 3 are compared with Comparative Example 1, Comparative Example 2 and Comparative Example 3, Comparative Example 1 replaces the composite filler in the preparation process of the alkali-resistant resin of Example 3 with the silane-modified precursor of Example 3. Due to the lack of the polydopamine layer, it lacks the reaction site with the epoxy resin matrix, which leads to a decrease in its mechanical properties, thereby affecting its breakage rate. Comparative Example 2 replaces the composite filler in the preparation process of the alkali-resistant resin of Example 3 with a mixture of molybdenum disulfide and carbon nanotubes. Due to the lack of a special three-dimensional interlayer structure, its ability to block alkaline substances decreases, thereby affecting its alkali resistance. Comparative Example 3 removes the modified branched polyimide in the preparation process of the alkali-resistant resin of Example 3. Due to the lack of modified branched polyimide having siloxane segments and epoxy groups, its mechanical properties and alkali resistance are significantly reduced.

[0014] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0015] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields, characterized in that: The method comprises the following steps: weighing the following raw materials in parts by weight: 100 parts of a quartz sand substrate, 4.2-5.5 parts of an alkali-resistant resin and 0.2-0.3 parts of calcium stearate, preheating the quartz sand substrate to 80-100° C., adding the quartz sand substrate to a sand mixer, adding the alkali-resistant resin, stirring for 15-20 minutes, adding the calcium stearate, continuing to stir for 15-20 minutes, pouring out, drying, curing at 140° C. for 2 hours, cooling, crushing and sieving to obtain quartz fracturing sand coated with an alkali-resistant resin for oil fields; The alkali-resistant resin is prepared by the following steps: weighing the following raw materials in parts by weight: 40-50 parts of bisphenol A epoxy resin, 15-20 parts of modified branched polyimide, 1.5-3 parts of composite filler, 3.5-4.5 parts of phenolic amine curing agent, 5-8 parts of ethanol, 5-8 parts of acetone, 0.4-0.6 parts of defoaming agent and 0.6-0.8 parts of leveling agent, mixing the bisphenol A epoxy resin, modified branched polyimide, composite filler, phenolic amine curing agent, ethanol, acetone, defoaming agent and leveling agent to prepare the alkali-resistant resin; The modified branched polyimide is prepared by the following steps: Step A1: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone were mixed, and the mixture was reacted for 4-6 hours under nitrogen protection, at a stirring rate of 140-180 rpm and a temperature of 25-30° C., and then vacuum dried at a temperature of 140° C. for 1 hour, and then vacuum dried at a temperature of 240° C. for 1 hour to obtain intermediate 1; Step A2: The intermediate 1, trimethylolpropane and dimethylacetamide are mixed, and dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added under stirring at a rate of 180-240 rpm and a temperature of 35-40° C., and the mixture is reacted for 10-12 hours, and the mixture is distilled under reduced pressure, washed and dried to obtain a branched polyimide. The branched polyimide, epichlorohydrin and dimethylacetamide are mixed, and the mixture is reacted for 6-7 hours under stirring at a rate of 180-240 rpm and a temperature of 65-68° C., and the mixture is distilled under reduced pressure, and toluene and sodium hydroxide are added. The mixture is cooled to 25-30° C., and the reaction is continued for 6-7 hours, and the mixture is distilled under reduced pressure and dried to obtain a modified branched polyimide.

2. The method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields according to claim 1, characterized in that: In step A1, the usage ratio of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,2,4-benzenetricarboxylic anhydride and N-methylpyrrolidone is 0.012-0.013 mol: 0.024-0.025 mol: 25-30 mL.

3. The method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields according to claim 1, characterized in that: In step A2: the amount ratio of intermediate 1, trimethylolpropane, dimethylacetamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 2.4-2.6g: 0.6-0.7g: 45-50mL: 1-1.1g: 0.05-0.06g; the amount ratio of branched polyimide, epichlorohydrin, dimethylacetamide, toluene and sodium hydroxide is 1.8-2.2g: 0.45-0.5g: 25-30mL: 8-10mL: 0.3-0.4g.

4. The method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields according to claim 1, characterized in that: The composite filler is prepared by the following steps: Step B1: Mix the carbon nanotubes and deionized water and disperse them ultrasonically for 15-20 minutes, then stir and add hexadecyltrimethylammonium bromide at a stirring rate of 120-140 rpm at room temperature, stir for 30-40 minutes, then add sodium molybdate dihydrate and thiourea, continue stirring for 15-20 minutes, transfer them into a reactor, react at a temperature of 180-210° C. for 24 hours, cool, centrifuge, dry, and then sinter for 2 hours at a temperature of 800° C. under nitrogen protection to obtain a precursor; Step B2: triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol and deionized water are mixed, stirred at a stirring rate of 120-140 rpm and a temperature of 60°C, and a precursor is added, reacted for 2-3 hours, filtered, washed, and dried to obtain a silane-modified precursor, the silane-modified precursor, Tris-HCl buffer solution and ethanol solution are mixed, ultrasonically dispersed for 15-20 minutes, and then stirred at a stirring rate of 120-140 rpm and a temperature of 60°C and dopamine hydrochloride is added, reacted for 4-6 hours, centrifuged, washed, and dried to obtain a composite filler.

5. The method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields according to claim 4, characterized in that: In step B1, the ratio of carbon nanotubes, deionized water, hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and thiourea is 0.1-0.12 g: 75-80 mL: 0.52-0.55 g: 0.72-0.73 g: 1.2-1.3 g.

6. The method for preparing quartz fracturing sand coated with an alkali-resistant resin for oil fields according to claim 4, characterized in that: In step B2: the amount ratio of triethoxy (1H, 1H, 2H, 2H-nonafluorohexyl) silane, ethanol, deionized water and precursor is 0.05-0.08 g: 30-35 mL: 4-6 mL: 2.3-2.5 g; the mass concentration of Tris-HCl buffer solution is 1.6 g / L, pH = 8.5, the volume concentration of ethanol solution is 75%, and the amount ratio of silane-modified precursor, Tris-HCl buffer solution, ethanol solution and dopamine hydrochloride is 1.2-1.4 g: 15-20 mL: 45-50 mL: 0.4-0.42 g.

7. An alkali-resistant resin coated quartz fracturing sand for oil fields, characterized in that: Prepared according to any one of claims 1 to 6.