Magnetic nano oil displacement agent and preparation method thereof

Abstract

The invention relates to the technical field of chemical oil-displacing agents for tertiary oil recovery, and particularly discloses a magnetic nano oil-displacing agent and a preparation method thereof. The preparation method comprises the following steps: S1, taking purple phosphorus nanosheets, ferrous sulfate, ferric chloride and ammonia water as raw materials to react to obtain magnetic purple phosphorus nanosheets; s2, reacting the polymer A with ethylenediamine to obtain an aminated polymer A; s3, adding the aminated polymer A or polymer B and 4-dimethylaminopyridine 1, 3-dicyclohexylcarbodiimide into an aqueous solution of the magnetic purple phosphorus nanosheet, so as to obtain a modified magnetic purple phosphorus nanosheet; s4, performing ammonification reaction on the surfactant to obtain an aminated surfactant; and S5, adding an aminated surfactant into the modified magnetic purple phosphorus nanosheet aqueous solution, then adding N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, and carrying out a reaction to obtain the magnetic nano oil displacement agent. The oil-displacing agent disclosed by the invention can realize magnetic recovery while realizing a viscosity reduction effect so as to improve the oil recovery rate, and waste of raw materials is avoided.

Description

Technical Field

[0001] This invention relates to the field of tertiary oil recovery chemical flooding agents, specifically a magnetic nano-flooding agent and its preparation method. Background Technology

[0002] In recent years, global oil consumption has reached an alarming level, and some oil fields are facing difficulties in extraction. However, according to some studies, only about 30% of the oil has been successfully extracted after primary and secondary oil recovery, and a large amount of crude oil remains trapped in the rock layer.

[0003] To extract residual oil from reservoirs, tertiary oil recovery is necessary, and the techniques used in tertiary oil recovery are known as enhanced oil recovery (EOR) methods. Traditional EOR techniques include steam thermal recovery, microbial flooding, and chemical flooding. Recently, the combined use of nanoparticles and surfactants in tertiary oil recovery has proven effective and promising. However, nanoparticles and surfactants are expensive and cannot be efficiently recycled after use, resulting in high costs for tertiary oil recovery.

[0004] Chinese invention patent CN112251206A discloses a magnetic nano-oil displacement agent based on black phosphorus, which is composed of black phosphorus matrix, magnetic material, chitosan, polyethylene glycol modifier and betaine-type surfactant, realizing magnetic recovery and improving oil recovery rate.

[0005] The black phosphorus matrix used in this invention is less stable than purple phosphorus, resulting in inferior performance in many aspects. Furthermore, the magnetic material, surfactant, and polymer-modified black phosphorus matrix are simply mixed, with weak interactions between them, making it impossible to completely recover the surfactant and nanoparticles. Summary of the Invention

[0006] The purpose of this invention is to provide a magnetic nano-oil displacement agent and its preparation method to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S01: Disperse purple phosphorus nanosheets in deionized water, then add ferrous sulfate and ferric chloride solid powders and mix evenly. Add 25%~28% ammonia water and mix evenly. React at 40 ℃~80 ℃ for 3~6 h. Separate by magnetic adsorption, wash and dry to obtain magnetic purple phosphorus nanosheets. S02: Mix polymer A with deionized water, then add ethylenediamine and mix thoroughly. React at 20 ℃~30 ℃ for 24~36 h, and dry to obtain amination-treated polymer A; S03: Magnetic purple phosphorus nanosheets are dispersed in deionized water, and then aminated polymer A or polymer B, 4-dimethylaminopyridine, and 1,3-dicyclohexylcarbodiimide are added and mixed evenly. The mixture is reacted at 20 ℃~30 ℃ for 24~36 h, separated by magnetic adsorption, washed and dried to obtain modified magnetic purple phosphorus nanosheets. S04: Dissolve the surfactant in deionized water, then add hydroxylamine-O-sulfonic acid, react at 90 ℃~120 ℃ for 12~18 h, reflux the resulting pink product, add 25%~28% concentrated ammonia, stir magnetically, react at 80 ℃~100 ℃ for 6~10 h, reflux to obtain the aminated surfactant; S05: Modified magnetic purple phosphorus nanosheets were dispersed in deionized water, then an aminated surfactant was added and mixed evenly. N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were then added. The mixture was reacted at 20℃~30℃ for 24~36 h, separated by magnetic attraction, washed, and dried to obtain the magnetic nano-oil displacement agent.

[0008] Further, in step S01, the mass ratio of ferrous sulfate to ferric chloride solid powder is 1~3:1; the mass ratio of ammonia to deionized water is 1:2~8; the mass ratio of purple phosphorus nanosheets to deionized water is 1:550~1450; and the total mass of ferrous sulfate and ferric chloride solid powder accounts for 1~2% of the total mass of the reaction system.

[0009] Further, in step S02, the mass ratio of polymer A to ethylenediamine is 1~3:1, and the mass ratio of polymer A to deionized water is 1:40~80.

[0010] Further, in step S03, the mass ratio of the aminated polymer A or polymer B to the magnetic purple phosphorus nanosheets is 10~30:1; the mass ratio of the magnetic purple phosphorus nanosheets to deionized water is 1:550~1450; the mass ratio of 4-dimethylaminopyridine to 1,3-dicyclohexylcarbodiimide is 1:1.25~2.5; and the mass ratio of the magnetic purple phosphorus nanosheets to 4-dimethylaminopyridine is 1:4~8.

[0011] Furthermore, polymer A is one of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose; polymer B is one of carboxymethyl cellulose, carboxyethyl cellulose, and carboxypropyl methyl cellulose.

[0012] Further, in step S04, the mass ratio of the surfactant to hydroxylamine-O-sulfonic acid is 1~2:1; the mass ratio of the surfactant to deionized water is 1:2~8.

[0013] Furthermore, the surfactant is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate and cocamidopropyl hydroxysulfonate betaine, wherein the mass ratio of sodium fatty alcohol polyoxyethylene ether sulfate to cocamidopropyl hydroxysulfonate betaine is 1~5:1.

[0014] Further, in step S05, the mass ratio of the aminated surfactant to the modified magnetic purple phosphorus nanosheets is 50~150:1; the mass ratio of the modified magnetic purple phosphorus nanosheets to deionized water is 1:550~1450; the mass ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1~1.5; and the mass ratio of the magnetic purple phosphorus nanosheets to N-hydroxysuccinimide is 1:2~6.

[0015] The present invention also provides a magnetic nano-oil displacement agent prepared by the preparation method described above.

[0016] The present invention also provides an application of the magnetic nano-dispatch agent prepared by the above-described preparation method in tertiary oil recovery.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention uses ferrous sulfate and ferric chloride to generate magnetic materials in situ on the surface of purple phosphorus nanosheets, which enhances the bonding force between the magnetic materials and the purple phosphorus nanosheets, making them less likely to detach under complex conditions and enabling them to be recycled by applying an external magnetic field.

[0018] When the magnetic purple phosphorus nanosheets react further with the polymer, the polymer can form multiple long polymer chains on the surface of the magnetic purple phosphorus nanosheets. This improves the dispersibility, impact resistance, and toughness of the nano-oil displacement agent in water, thereby enhancing its viscosity-reducing ability. The long polymer chains not only increase the planar and vertical sweep volume of the nano-oil displacement agent but also increase the number of active sites, facilitating subsequent chemical modification.

[0019] When the modified magnetic purple phosphorus nanosheets react further with the aminated surfactant, the surfactant can make the polymer long chain have both lipophilic and hydrophilic groups. Due to the repulsive force between these two groups, the curling and entanglement within and between molecules are reduced, forming smaller emulsion microspheres during emulsification, which greatly reduces the viscosity of oil and thus improves oil recovery.

[0020] The magnetic nano-displacement agent of this invention has great potential for development in tertiary oil recovery due to its excellent performance. It can magnetize and modify purple phosphorus nanosheets and graft polymers and surfactants under relatively mild conditions. It also has the advantages of being recyclable and cost-effective, providing ideas for developing a new generation of displacement agents. Attached Figure Description

[0021] Figure 1 The magnetic field strength of the vibrating sample of the magnetic nano-oil displacement agent is shown in the needle diagram. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0023] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.1 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0024] S2: Weigh 0.1 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0025] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0026] S4: After the reaction was complete, the magnetic magnet was removed, and 0.1 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 2

[0027] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.11 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, magnetic separation was performed, followed by washing with water and separation again, repeated three times for purification. Magnetic purple phosphorus nanosheets were obtained by freeze-drying.

[0028] S2: Weigh 0.11 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0029] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0030] S4: After the reaction was complete, the magnetic magnet was removed, and 0.11 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 3

[0031] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.12 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0032] S2: Weigh 0.12 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0033] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0034] S4: After the reaction was complete, the magnetic magnet was removed, and 0.12 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 4

[0035] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.13 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, magnetic separation was performed, followed by washing with water and separation again, repeated three times for purification. The resulting magnetic purple phosphorus nanosheets were then freeze-dried.

[0036] S2: Weigh 0.13 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0037] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0038] S4: After the reaction was complete, the magnetic magnet was removed, and 0.13 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 5

[0039] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.14 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0040] S2: Weigh 0.14 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0041] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0042] S4: After the reaction was complete, the magnetic magnet was removed, and 0.14 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 6

[0043] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.15 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0044] S2: Weigh 0.15 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0045] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0046] S4: After the reaction was complete, the magnetic magnet was removed, and 0.15 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 7

[0047] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.1 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0048] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0049] S3: Weigh 0.1 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0050] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0051] S5: After the reaction was complete, the magnetic magnet was removed, and 0.1 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 8

[0052] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.11 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, magnetic separation was performed, followed by washing with water and separation again, repeated three times for purification. Magnetic purple phosphorus nanosheets were obtained by freeze-drying.

[0053] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0054] S3: Weigh 0.11 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0055] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0056] S5: After the reaction was complete, the magnetic magnet was removed, and 0.11 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 9

[0057] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.12 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0058] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0059] S3: Weigh 0.12 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0060] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0061] S5: After the reaction was complete, the magnetic magnet was removed, and 0.12 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 10

[0062] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.13 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, magnetic separation was performed, followed by washing with water and separation again, repeated three times for purification. The resulting magnetic purple phosphorus nanosheets were then freeze-dried.

[0063] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0064] S3: Weigh 0.13 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0065] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0066] S5: After the reaction was complete, the magnetic magnet was removed, and 0.13 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 11

[0067] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.14 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0068] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0069] S3: Weigh 0.14 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0070] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0071] S5: After the reaction was complete, the magnetic magnet was removed, and 0.14 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Example 12

[0072] This embodiment provides a method for preparing a magnetic nano-oil displacement agent, comprising the following steps: S1: 0.15 g of purple phosphorus nanosheets were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic purple phosphorus nanosheets.

[0073] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0074] S3: Weigh 0.15 g of the magnetic purple phosphorus nanosheets prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic purple phosphorus nanosheets.

[0075] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0076] S5: After the reaction was complete, the magnetic magnet was removed, and 0.15 g of modified magnetic purple phosphorus nanosheets were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic purple phosphorus nanosheets were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Comparative Example 1

[0077] S1: 0.1 g of silica nanoparticles were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic silica nanoparticles.

[0078] S2: Add 3 g of hydroxyethyl cellulose to 100 mL of deionized water, sonicate for 10 min to disperse evenly, then add 2 mL of ethylenediamine while stirring and mix evenly. Stir at room temperature for 24 h, and freeze dry to obtain the product N-hydroxyethyl cellulose.

[0079] S3: Weigh 0.1 g of the magnetic silica nanoparticles prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of N-hydroxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain modified magnetic silica nanoparticles.

[0080] S4: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0081] S5: After the reaction was complete, the magnetic magnet was removed, and 0.1 g of modified magnetic silica nanoparticles were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic silica nanoparticles were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent. Comparative Example 2

[0082] S1: 0.1 g of silica nanoparticles were mixed with 70 mL of deionized water and sonicated for 10 min to form a uniform dispersion. Next, 1.17 g of ferric chloride hexahydrate and 1.2 g of ferrous sulfate heptahydrate were weighed and dissolved in 30 mL of deionized water, sonicated for 3 min, and then added to the 70 mL dispersion, sonicated again for 30 min. 20 mL of 28% ammonia solution was added to the above mixture, sonicated for 5 min, and then mechanically stirred at 80 ℃ for 2 h, followed by cooling to 40 ℃ and mechanically stirring for 1.5 h. Finally, the mixture was magnetically separated, washed with water, and separated again, repeated three times for purification, and then freeze-dried to obtain magnetic silica nanoparticles.

[0083] S2: Weigh 0.1 g of the magnetic silica nanoparticles prepared above and disperse them in 100 mL of deionized water, then sonicate for 30 min. Weigh 0.060 g of 4-dimethylaminopyridine (DMAP) and 0.080 g of 1,3-dicyclohexylcarbodiimide (DCC), add them to the dispersion, and sonicate again for 30 min. After sonication, add 1.5 g of carboxyethyl cellulose and mechanically stir at room temperature for 24 h. After the reaction is complete, pour the resulting solution into a 50 mL centrifuge tube, centrifuge at 8000 r / min for 10 min to collect the precipitate, wash with deionized water, separate magnetically, repeat twice, and freeze-dry to obtain the modified magnetic silica nanoparticles.

[0084] S3: Weigh 10 g of cocamidopropyl hydroxysulfonate betaine (CHSB) and 5 g of sodium fatty alcohol polyoxyethylene ether sulfate (AES), mix with 85 mL of deionized water, and sonicate while stirring for 30 min until a clear solution is formed. Add 10 g of hydroxylamine-O-sulfonic acid to the above solution and mix thoroughly. Stir magnetically and reflux at 100 °C for 18 h. After the reaction is complete, add 15 mL of 28% ammonia solution, stir magnetically, and reflux at 80 °C for 8 h.

[0085] S4: After the reaction was complete, the magnetic magnet was removed, and 0.1 g of modified magnetic silica nanoparticles were added and dispersed in 100 mL of deionized water. The mixture was stirred while sonicated for 30 min until the modified magnetic silica nanoparticles were completely dispersed in the solution. Then, 0.200 g of N-hydroxysuccinimide (NHS) and 0.200 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added, and the mixture was mechanically stirred at room temperature for 24 h. After the reaction was complete, the mixture was magnetically separated, washed twice with 100 mL of deionized water to purify the product, and then freeze-dried to obtain the magnetic nano-oil displacement agent.

[0086] Performance testing The viscosity-reducing performance of the magnetic nano-oil displacement agents prepared in the various embodiments and comparative examples of the present invention was measured, and the results are shown in Table 1.

[0087] The magnetic nano-oil displacement agents prepared in Examples 1-12 and Comparative Examples 1-2 were prepared into a brine solution sample with a concentration of 420 mg / 100 g using brine with a salinity of 1.3 W. 30 g of the sample was mixed with 70 g of petroleum and stirred at 300 rpm for 2 min using a GZ-120-S type mechanical stirrer. The viscosity of the emulsion was measured at a temperature of 50 °C.

[0088] The brine with a mineralization of 13000 mg / L is prepared from sodium chloride, calcium chloride, magnesium chloride, sodium sulfate, sodium bicarbonate and deionized water. The sodium ion concentration is 4566.8 mg / L, the magnesium ion concentration is 33.2 mg / L, the calcium ion concentration is 210.5 mg / L, and the total ion concentration is 13000 mg / L.

[0089] The petroleum used in the test was Jin-12-P-45, which had an apparent viscosity of 9244 mPa·s at 50 ℃.

[0090] Table 1. Viscosity reduction performance test data of magnetic nano-oil displacement agents in Examples 1-12 and Comparative Examples 1-2.

[0091] According to the performance test data in Table 1: A comparison of data from Examples 1-6 and Examples 7-12 shows that the concentration of the oil displacement agent at the beginning of the preparation affects each step of the reaction. The preferred preparation concentration is 1 g / L. The reason for this is that at a lower concentration, the nano-oil displacement agent based on purple phosphorus is more evenly dispersed in deionized water, allowing for more grafting of polymers and surfactants.

[0092] Data comparisons of Examples 1 and 7, Examples 2 and 8, Examples 3 and 9, Examples 4 and 10, Examples 5 and 11, and Examples 6 and 12 show that the difference in viscosity reduction results is not significant when the preparation is carried out using the steps within the scope of the claims, regardless of whether polymer A or polymer B is used.

[0093] As can be seen from the table, the viscosity reduction rate of Examples 1-12 reached over 97%, indicating that this magnetic nano-oil displacement agent has a significant contribution to viscosity reduction.

[0094] Furthermore, comparing the data from Examples 1-12 and Comparative Examples 1-2, it can be seen that when using the magnetic nano-oil displacement agent of the present invention for viscosity reduction, the purple phosphorus nanosheets have a large specific surface area and many active sites, which can better carry out the next reaction and greatly improve the viscosity reduction rate.

[0095] like Figure 1 As shown, the magnetic needle test of the vibrating samples of the magnetic nano-oil displacement agents prepared in Examples 1 and 7 shows that the samples are magnetic and can be recovered by applying an external magnetic field.

[0096] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0097] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a magnetic nano-oil displacement agent, characterized in that, Includes the following steps: S01: Disperse purple phosphorus nanosheets in deionized water, then add ferrous sulfate and ferric chloride solid powders and mix evenly, add ammonia water and mix evenly, react at 40 ℃~80 ℃ for 3~6 h, separate by magnetic adsorption, wash and dry to obtain magnetic purple phosphorus nanosheets; S02: Mix polymer A with deionized water, then add ethylenediamine and mix thoroughly. React at 20 ℃~30 ℃ for 24~36 h, and dry to obtain amination polymer A; S03: Magnetic purple phosphorus nanosheets are dispersed in deionized water, and then aminated polymer A or polymer B, 4-dimethylaminopyridine, and 1,3-dicyclohexylcarbodiimide are added and mixed evenly. The mixture is reacted at 20 ℃~30 ℃ for 24~36 h, separated by magnetic adsorption, washed and dried to obtain modified magnetic purple phosphorus nanosheets. S04: Dissolve the surfactant in deionized water, then add hydroxylamine-O-sulfonic acid, react at 90 ℃~120 ℃ for 12~18 h, reflux the resulting pink product, add 25%~28% concentrated ammonia, stir magnetically, react at 80 ℃~100 ℃ for 6~10 h, reflux to obtain the aminated surfactant; S05: Modified magnetic purple phosphorus nanosheets were dispersed in deionized water, then an aminated surfactant was added and mixed evenly. N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were then added. The mixture was reacted at 20 ℃~30 ℃ for 24~36 h, separated by magnetic attraction, washed, and dried to obtain the magnetic nano-oil displacement agent.

2. The method for preparing a magnetic nano-oil displacement agent according to claim 1, characterized in that, In step S01, the mass ratio of ferrous sulfate to ferric chloride solid powder is 1~3:1; the mass ratio of ammonia to deionized water is 1:2~8; the mass ratio of purple phosphorus nanosheets to deionized water is 1:550~1450; and the total mass of ferrous sulfate and ferric chloride solid powder accounts for 1~2% of the total mass of the reaction system.

3. The method for preparing a magnetic nano-oil displacement agent according to claim 1, characterized in that, In step S02, the mass ratio of polymer A to ethylenediamine is 1~3:1, and the mass ratio of polymer A to deionized water is 1:40~80.

4. The method for preparing a magnetic nano-oil displacement agent according to claim 1, characterized in that, In step S03, the mass ratio of the aminated polymer A or polymer B to the magnetic purple phosphorus nanosheets is 10~30:1; the mass ratio of the magnetic purple phosphorus nanosheets to deionized water is 1:550~1450; the mass ratio of 4-dimethylaminopyridine to 1,3-dicyclohexylcarbodiimide is 1:1.25~2.5; and the mass ratio of the magnetic purple phosphorus nanosheets to 4-dimethylaminopyridine is 1:4~8.

5. The method for preparing a magnetic nano-oil displacement agent according to claim 4, characterized in that, Polymer A is one of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose; polymer B is one of carboxymethyl cellulose, carboxyethyl cellulose, and carboxypropyl methyl cellulose.

6. The method for preparing a magnetic nano-oil displacement agent according to claim 1, characterized in that, In step S04, the mass ratio of the surfactant to hydroxylamine-O-sulfonic acid is 1~2:1; the mass ratio of the surfactant to deionized water is 1:2~8.

7. The method for preparing a magnetic nano-oil displacement agent according to claim 6, characterized in that, The surfactant is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate and cocamidopropyl hydroxysulfonate betaine, wherein the mass ratio of sodium fatty alcohol polyoxyethylene ether sulfate to cocamidopropyl hydroxysulfonate betaine is 1~5:

1.

8. The method for preparing a magnetic nano-oil displacement agent according to claim 1, characterized in that, In step S05, the mass ratio of the aminated surfactant to the modified magnetic purple phosphorus nanosheets is 50~150:1; the mass ratio of the modified magnetic purple phosphorus nanosheets to deionized water is 1:550~1450; the mass ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1~1.5; and the mass ratio of the magnetic purple phosphorus nanosheets to N-hydroxysuccinimide is 1:2~6.

9. A magnetic nano-oil displacement agent prepared by the preparation method according to any one of claims 1-8.

10. The application of a magnetic nano-dispatch agent prepared by the preparation method according to any one of claims 1-8 in tertiary oil recovery.

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