Temperature and pH dual-responsive oil displacement agent, preparation method and application thereof

Abstract

This invention discloses an oil displacement agent that responds to both temperature and pH, comprising first modified silicon quantum dots grafted with groups and groups, wherein the particle size of the first modified silicon quantum dots is less than 10 nm. The beneficial effects of this invention are: the oil displacement agent prepared by this invention has good stability, and under alkaline ground conditions at 25°C, it has strong hydrophilicity and good injectability. After entering an acidic formation environment at 65°C, it can quickly respond to undergo a hydrophilic-lipophilic balance transition, exhibiting high interfacial activity. The total recovery rate at 65°C is also above 52%. Overall, the oil displacement agent can be adapted to the actual formation parameters of different target reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of oilfield crude oil recovery technology, specifically relating to an oil displacement agent that responds to both temperature and pH, its preparation method, and its application. Background Technology

[0002] The exploration and development of unconventional oil and gas resources has gradually become a key focus of the petroleum industry. Low-permeability reservoirs, as typical unconventional reservoirs, are rich in reserves and have extremely high exploitation value. However, these reservoirs are often accompanied by problems such as high temperature and salinity, strong heterogeneity, and low permeability, which significantly reduce the displacement efficiency and migration capacity of traditional chemical injection agents within the formation. Therefore, there is an urgent need to design efficient and intelligent oil displacement materials to address the severe challenges facing the development of complex oil reservoirs.

[0003] Nanomaterials have shown great potential in enhancing oil recovery (EOR). Particle size, as a core parameter of nanoparticles, significantly affects their oil displacement efficiency. Generally, smaller-sized nanoparticles tend to have better dispersion stability and interfacial activity, and are more likely to migrate in low-permeability micropore throats, which is beneficial to improving the actual effect of injection agents. In recent years, quantum dots, as a novel zero-dimensional nanomaterial, have shown significant advantages in the field of enhanced oil recovery due to their extremely small size, extremely high specific surface area, and extremely strong stability. Numerous laboratory experiments and theoretical studies have fully confirmed that quantum dots can synergistically improve oil recovery through multiple mechanisms, including significantly reducing oil-water interfacial tension, changing rock surface wettability, increasing structural separation pressure, improving emulsion and foam stability, and improving water-oil mobility ratio. Among many quantum dot materials, silicon quantum dots (SiQDs) exhibit unique advantages in this field due to their excellent compatibility with reservoir rocks, environmental friendliness (low toxicity), wide availability of raw materials, relatively simple synthesis process, and mild reaction conditions.

[0004] However, existing silicon quantum dot oil displacement systems still have certain limitations. CN118956365A combines silicon quantum dot nanomaterials with zwitterionic surfactants to obtain a silicon quantum dot nanofluid with an average size of less than 20 nm. It has excellent interfacial activity and temperature-resistant negative charge, but the interfacial activity obtained solely through physical adsorption is prone to desorption under high temperature and high salt conditions, resulting in limited effectiveness. CN118995203B obtains silicon quantum dots with a Janus structure through a one-step method, which can significantly reduce the interfacial tension between oil and water. However, the preparation process of this material is relatively complex, and once traditional high-interfacial-activity nano-oil displacement agents enter the formation, their emulsification performance is uncontrollable. Excessive interfacial activity and strong emulsification can lead to difficulties in demulsification of injected and drained fluids, significantly increasing the cost and engineering difficulty of subsequent surface water treatment.

[0005] To address the existing problems, we propose an oil displacement agent that responds to both temperature and pH.

[0006] The information disclosed in this background section is only for understanding the background technology of the inventive concept, and therefore may include information that does not constitute prior art. Summary of the Invention

[0007] The purpose of this invention is to provide an oil displacement agent that responds to both temperature and pH, in order to solve the problems mentioned in the background art.

[0008] On one hand, this disclosure provides an embodiment of a temperature and pH dual-responsive oil displacement agent comprising grafted with Groups and The first modified silicon quantum dot has a particle size of less than 10 nm.

[0009] As an optional implementation, a first modified silicon quantum dot and a second modified silicon quantum dot are used, wherein the first modified silicon quantum dot comprises... Groups and The second modified silicon quantum dot includes groups, Groups, Groups and The particle size of both the first modified silicon quantum dot and the second modified silicon quantum dot is less than 10 nm.

[0010] As an optional implementation, the mass ratio of the first modified silicon quantum dot to the second modified silicon quantum dot is (70-95):(5-30).

[0011] As an optional implementation, the preparation steps of the first modified silicon quantum dot include:

[0012] 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained.

[0013] 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained.

[0014] 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product;

[0015] 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained.

[0016] 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots.

[0017] As an optional implementation, the molar ratio of 1,3-propanesulfonic acid lactone to γ-aminopropyltriethoxysilane is (0.3-0.5):1.

[0018] As an optional implementation, the molar ratio of maleic anhydride to γ-aminopropyltriethoxysilane is (0.55-0.75):1.

[0019] As an alternative implementation, the mass of the second intermediate product is 2.5-3.5 times that of the first intermediate product.

[0020] As an alternative implementation, the mass fraction of the first silicon quantum dot in water is 0.02%-0.10%.

[0021] As an optional implementation, the molar ratio of N-isopropylacrylamide, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and thermal initiator is 100:(0.8-1.2):(0.1-0.5).

[0022] As an alternative implementation, X is a natural number between 83 and 125.

[0023] As an optional implementation, the preparation steps of the second modified silicon quantum dots include:

[0024] 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the second silicon quantum dots are obtained.

[0025] 2) The second silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the second reaction solution was obtained.

[0026] 3) Add maleic anhydride to the second reaction solution, react and purify to obtain the third intermediate product;

[0027] 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in a fourth solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to a fifth solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction and bond breaking reaction. After the reaction and purification, the fourth intermediate product was obtained.

[0028] 5) Dissolve the third intermediate product prepared in step 3) in the sixth solvent and add a catalyst to obtain the first dispersion. Add the fourth intermediate product to the first dispersion and carry out the thiol-ene click reaction. After the reaction, purify to obtain the fifth intermediate product.

[0029] 6) Dissolve the fifth intermediate in the seventh solvent, add an appropriate amount of benzyl thiol, adjust the pH to alkaline, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the second modified silicon quantum dots.

[0030] As an optional implementation, the preparation method includes the following steps:

[0031] 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained.

[0032] 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained.

[0033] 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product;

[0034] 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained.

[0035] 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots.

[0036] 6) Mix an appropriate amount of the first modified silicon quantum dots with water to obtain an oil displacement agent.

[0037] As an optional implementation, the preparation method includes the following steps:

[0038] 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained.

[0039] 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained.

[0040] 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product;

[0041] 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained.

[0042] 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots.

[0043] 6) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the second silicon quantum dots are obtained.

[0044] 7) The second silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the second reaction solution was obtained.

[0045] 8) Add maleic anhydride to the second reaction solution, react and purify to obtain the third intermediate product;

[0046] 9) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in a fourth solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to a fifth solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, a fourth intermediate product was obtained.

[0047] 10) Dissolve the third intermediate in the sixth solvent and add a catalyst to obtain the first dispersion. Add the fourth intermediate to the first dispersion and carry out the thiol-ene click reaction. After the reaction, purify to obtain the fifth intermediate.

[0048] 11) Dissolve the fifth intermediate in the seventh solvent, add an appropriate amount of benzyl thiol, adjust the pH to alkaline, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the second modified silicon quantum dots.

[0049] 12) Mix appropriate amounts of first modified silicon quantum dots, second modified silicon quantum dots and water to obtain an oil displacement agent.

[0050] As an alternative implementation method, oil displacement agents are used to enhance oilfield recovery.

[0051] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application.

[0052] Compared with the prior art, the beneficial effects of the present invention are: the oil displacement agent prepared by the present invention has good stability, and under alkaline ground conditions at 25°C, it has strong hydrophilicity and good injectability. After entering the acidic formation environment at 65°C, it can quickly respond to the hydrophilic-lipophilic balance transition and has high interfacial activity. The total recovery rate at 65°C is also above 52%. Overall, the oil displacement agent can be adapted to the actual formation parameters of different target oil reservoirs. Attached Figure Description

[0053] Figure 1 The FTIR comparative analysis spectra of unmodified silicon quantum dots, the first intermediate product, and Examples 2 and 5 are shown.

[0054] Figure 2 XPS full-spectrum scanning analysis was performed on the spectra of Examples 2, 5, the first intermediate product, and the unmodified silicon quantum dots.

[0055] Figure 3 Transmission microscope images of Examples 2, 5, and Comparative Example 1 under acidic and alkaline conditions. Detailed Implementation

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0057] Example 1:

[0058] 1) Dissolve 2.21 g of 98% γ-aminopropyltriethoxysilane and 0.04 g of sodium ascorbate in 10 ml of deionized water and react at 70 °C for 40 min. After the reaction, a dispersion containing the first silicon quantum dots is obtained. Then, the pH of the dispersion containing the first silicon quantum dots is adjusted to 7 using hydrochloric acid. Tetrahydrofuran is then added to the dispersion containing the first silicon quantum dots to precipitate the silicon quantum dots. After centrifugation and purification, a concentrated solution is obtained. After lyophilization, the first silicon quantum dots are obtained.

[0059] 2) The first silicon quantum dots obtained in step 1) were added to 10 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for at least 10 min, and nitrogen gas was passed through for more than 5 min. Then 0.37 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 50 °C for 5 h to obtain the first reaction solution.

[0060] 3) Add 0.74 g of maleic anhydride to the first reaction solution and react at 25 °C for 5 h to obtain a solution containing the first intermediate product. Then, add 40 ml of ethyl acetate to the solution containing the first intermediate product to precipitate the first intermediate product. After centrifugation, collect the bottom precipitate, add the first intermediate product to deionized water and adjust the pH to 7.2. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the first intermediate product.

[0061] 4) Dissolve 100 mmol of N-isopropylacrylamide monomer, 0.8 mmol of 2-(dodecyltrithiocarbonyl)-2-methylpropionic acid, and 0.1 mmol of thermal initiator azobisisobutyronitrile in 30 ml of tetrahydrofuran. Purge with nitrogen for 5 min and react at 65 °C for 10 h to induce polymerization. Concentrate the product by rotary evaporation, add n-hexane to precipitate the product, centrifuge to purify, and vacuum dry the precipitate. Add the precipitate to 10 ml of anhydrous ethanol, purge with nitrogen, and add 10 mmol of reducing agent sodium triacetoxyborohydride. React at 25 °C for 2 h to induce reduction and bond breaking. After the solution changes from yellow to colorless, centrifuge to remove insoluble impurities, concentrate the reaction solution by rotary evaporation, add n-hexane to precipitate the product, and obtain the second intermediate product.

[0062] 5) Dissolve 0.5g of the first intermediate in an aqueous ethanol solution, add triethylamine and 1.25g of the second intermediate, purge with nitrogen for 5 min, and carry out the thiol-ene click reaction at 65°C under light-protected conditions for 5 h. After the reaction is completed, remove the ethanol solvent by rotary evaporation and remove insoluble impurities by centrifugation to obtain the first modified silicon quantum dots.

[0063] 6) Mix the first modified silicon quantum dots with water (the content of the first modified silicon quantum dots in the water is 0.02%) to obtain an oil displacement agent.

[0064] Example 2:

[0065] 1) Dissolve 2.21 g of 98% γ-aminopropyltriethoxysilane and 0.04 g of sodium ascorbate in 20 ml of deionized water and react at 90 °C for 60 min. After the reaction, a dispersion containing the first silicon quantum dots is obtained. Then, the pH of the dispersion containing the first silicon quantum dots is adjusted to 8 using hydrochloric acid. Tetrahydrofuran is then added to the dispersion containing the first silicon quantum dots to precipitate the silicon quantum dots. After centrifugation and purification, a concentrated solution is obtained. After lyophilization, the first silicon quantum dots are obtained.

[0066] 2) The first silicon quantum dots obtained in step 1) were added to 20 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for 10 min, and nitrogen gas was passed through for 10 min. Then 0.49 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 60 °C for 6 h to obtain the first reaction solution.

[0067] 3) Add 0.64 g of maleic anhydride to the first reaction solution and react at 35 °C for 6 h to obtain a solution containing the first intermediate product. Then, add 200 ml of ethyl acetate to the solution containing the first intermediate product to precipitate the first intermediate product. After centrifugation, collect the bottom precipitate, add the first intermediate product to deionized water and adjust the pH to 8. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the first intermediate product.

[0068] 4) Dissolve 100 mmol of N-isopropylacrylamide as a monomer, 1.2 mmol of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid (chain transfer agent), and 0.5 mmol of benzoyl peroxide in 50 ml of N,N-dimethylformamide. Purge with helium for 30 min and react at 75 °C for 12 h to induce polymerization. Concentrate the product by rotary evaporation, add n-hexane to precipitate the product, centrifuge to purify, and vacuum dry the precipitate. Add the precipitate to 20 ml of isopropanol, purge with helium, and add 10 mmol of sodium borohydride. React at 35 °C for 4 h to induce a reduction bond breaking reaction. After the solution changes from yellow to colorless, centrifuge to remove insoluble impurities, concentrate the reaction solution by rotary evaporation, add n-hexane to precipitate the product, and obtain the second intermediate product.

[0069] 5) Dissolve 0.5g of the first intermediate in an aqueous methanol solution, add N,N-diisopropylethylamine and 1.75g ​​of the second intermediate, purge with helium for 30min, and carry out the thiol-ene click reaction at 75℃ under light-protected conditions for 6h. After the reaction is completed, remove the methanol solvent by rotary evaporation and remove insoluble impurities by centrifugation to obtain the first modified silicon quantum dots.

[0070] 6) Mix the first modified silicon quantum dots with water (the content of the first modified silicon quantum dots is 0.1%) to obtain an oil displacement agent.

[0071] Example 3:

[0072] 1) Dissolve 2.21 g of 98% γ-aminopropyltriethoxysilane and 0.04 g of sodium ascorbate in 15 ml of deionized water and react at 80 °C for 50 min. After the reaction, a dispersion containing the first silicon quantum dots is obtained. Then, the pH of the dispersion containing the first silicon quantum dots is adjusted to 7.5 using hydrochloric acid. Tetrahydrofuran is then added to the dispersion containing the first silicon quantum dots to precipitate the silicon quantum dots. After centrifugation and purification, a concentrated solution is obtained. After lyophilization, the first silicon quantum dots are obtained.

[0073] 2) The first silicon quantum dots obtained in step 1) were added to 15 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for at least 10 min, and nitrogen gas was purged for 10 min. Then 0.6 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 55 °C for 5.5 h to obtain the first reaction solution.

[0074] 3) Add 0.54 g of maleic anhydride to the first reaction solution and react at 30 °C for 5.5 h to obtain a solution containing the first intermediate product. Then, add 90 ml of ethyl acetate to the solution containing the first intermediate product to precipitate the first intermediate product. After centrifugation, collect the bottom precipitate, add the first intermediate product to deionized water and adjust the pH to 7.5. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the first intermediate product.

[0075] 4) 100 mmol of N-isopropylacrylamide as monomer, 1.0 mmol of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and 0.4 mmol of benzoyl peroxide were dissolved in 40 ml of 1,4-dioxane. Helium was introduced for 10 min, and the reaction was carried out at 70 °C for 11 h to induce polymerization. The product was concentrated by rotary evaporation, and hexane was added to precipitate the product. After centrifugation and purification, the precipitate was obtained and dried under vacuum. The precipitate was added to 15 ml of methanol, helium was introduced for 10 min, and 10 mmol of sodium borohydride was added. The reaction was carried out at 30 °C for 3 h to induce a reduction bond breaking reaction. After the solution changed from yellow to colorless, insoluble impurities were removed by centrifugation. The reaction solution was then concentrated by rotary evaporation, and hexane was added to precipitate the product to obtain the second intermediate product.

[0076] 5) Dissolve 0.5g of the first intermediate product in an aqueous ethanol solution, add pyridine catalyst and 1.5g of the second intermediate product, purge with inert helium gas for 10 min, and carry out the thiol-ene click reaction at 70℃ under light-protected conditions for 5.5 h. After the reaction is completed, remove the ethanol solvent by rotary evaporation and remove insoluble impurities by centrifugation to obtain the first modified silicon quantum dots.

[0077] 6) Mix the first modified silicon quantum dots with water (the content of the first modified silicon quantum dots in the water is 0.05%) to obtain an oil displacement agent.

[0078] Example 4:

[0079] Preparation of the first modified silicon quantum dot:

[0080] The preparation of the first modified silicon quantum dot is the same as in Example 1.

[0081] Preparation of the second modified silicon quantum dots:

[0082] 1) Dissolve 2.21g of 98% γ-aminopropyltriethoxysilane and 0.04g of sodium ascorbate in 10ml of deionized water and react at 70℃ for 40min to obtain a dispersion containing second silicon quantum dots. Then, adjust the pH of the dispersion containing second silicon quantum dots to 7 using hydrochloric acid, add tetrahydrofuran to the dispersion to precipitate silicon quantum dots, centrifuge and purify to obtain a concentrated solution, freeze-dry to obtain second silicon quantum dots;

[0083] 2) The second silicon quantum dots obtained in step 1) were added to 10 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for 10 min, and nitrogen gas was passed through for 5 min. Then 0.37 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 50 °C for 5 h to obtain the second reaction solution.

[0084] 3) Add 0.74 g of maleic anhydride to the second reaction solution and react at 25 °C for 5 h to obtain a solution containing the third intermediate product. Then, add 40 ml of ethyl acetate to the solution containing the third intermediate product to precipitate the third intermediate product. After centrifugation, collect the bottom precipitate, add the third intermediate product to deionized water and adjust the pH to 7.2. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the third intermediate product.

[0085] 4) Dissolve 100 mmol of N-isopropylacrylamide as monomer, 0.8 mmol of 2-(dodecyltrithiocarbonyl)-2-methylpropionic acid, and 0.1 mmol of azobisisobutyronitrile in 30 mL of tetrahydrofuran. Purge with nitrogen for 5 min and react at 65 °C for 10 h to induce polymerization. Concentrate the product by rotary evaporation, add n-hexane to precipitate the product, centrifuge to purify, and vacuum dry the precipitate. Add the precipitate to 10 mL of anhydrous ethanol, purge with nitrogen, and add 10 mmol of sodium triacetoxyborohydride. React at 25 °C for 2 h to induce reduction and bond breaking. After the solution changes from yellow to colorless, centrifuge to remove insoluble impurities, concentrate the reaction solution by rotary evaporation, add n-hexane to precipitate the product, and obtain the fourth intermediate product.

[0086] 5) Dissolve 0.5g of the third intermediate in an aqueous ethanol solution and add triethylamine to obtain the first dispersion. Add 1.25g of the fourth intermediate to the first dispersion, purge with nitrogen for 5 min, and carry out a thiol-ene click reaction at 65℃ under light-protected conditions. After the reaction is complete, remove the ethanol solvent by rotary evaporation and purify to obtain the fifth intermediate.

[0087] 6) Dissolve 0.5g of the fifth intermediate product prepared in step 5) in an aqueous ethanol solution, add 0.05g of benzyl thiol, adjust the pH to alkaline, carry out the thiol-ene click reaction, purge with nitrogen for 5 min, react at 65℃ under light-protected conditions, and then purify to obtain the second modified silicon quantum dots.

[0088] A first modified silicon quantum dot, a second modified silicon quantum dot, and water were mixed (the mass ratio of the first silicon quantum dot to the second silicon quantum dot was 7:3, and the total content of the first silicon quantum dot and the second silicon quantum dot in the water was 0.02%) to obtain an oil displacement agent.

[0089] Example 5:

[0090] Preparation of the first modified silicon quantum dot:

[0091] The preparation of the first modified silicon quantum dots is the same as in Example 2.

[0092] Preparation of the second modified silicon quantum dots:

[0093] 1) Dissolve 2.21g of 98% γ-aminopropyltriethoxysilane and 0.04g of sodium ascorbate in 20ml of deionized water and react at 90℃ for 60min to obtain a dispersion containing second silicon quantum dots. Then, adjust the pH of the dispersion containing second silicon quantum dots to 7-8 using hydrochloric acid, add tetrahydrofuran to the dispersion to precipitate silicon quantum dots, centrifuge and purify to obtain a concentrated solution, freeze-dry to obtain second silicon quantum dots;

[0094] 2) The second silicon quantum dots obtained in step 1) were added to 20 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for at least 10 min, and nitrogen gas was passed through for more than 5 min. Then 0.49 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 60 °C for 6 h to obtain the second reaction solution.

[0095] 3) Add 0.64 g of maleic anhydride to the second reaction solution and react at 35 °C for 6 h to obtain a solution containing the third intermediate product. Then, add 200 ml of ethyl acetate to the solution containing the third intermediate product to precipitate the third intermediate product. After centrifugation, collect the bottom precipitate, add the third intermediate product to deionized water and adjust the pH to 7.5. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the third intermediate product.

[0096] 4) 100 mmol of N-isopropylacrylamide monomer, 1.2 mmol of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and 0.5 mmol of benzoyl peroxide were dissolved in 50 ml of N,N-dimethylformamide. Nitrogen gas was introduced for 30 min, and the mixture was reacted at 75 °C for 12 h to undergo polymerization. The product was concentrated by rotary evaporation, and hexane was added to precipitate the product. After centrifugation and purification, the precipitate was obtained and dried under vacuum. The precipitate was added to 20 ml of isopropanol, helium gas was introduced, and 10 mmol of sodium borohydride was added. The reaction was carried out at 35 °C for 4 h to perform a reduction bond breaking reaction. After the solution changed from yellow to colorless, insoluble impurities were removed by centrifugation. The reaction solution was then concentrated by rotary evaporation, and hexane was added to precipitate the product to obtain the fourth intermediate product.

[0097] 5) Dissolve 0.5g of the third intermediate in an aqueous methanol solution and add pyridine to obtain the first dispersion. Add 1.75g ​​of the fourth intermediate to the first dispersion, purge with nitrogen for 30min, and allow the thiol-ene click reaction to occur at 75℃ under light-protected conditions. After the reaction is complete, remove the methanol solvent by rotary evaporation and purify to obtain the fifth intermediate.

[0098] 6) Dissolve 0.5g of the fifth intermediate product prepared in step 5) in an aqueous methanol solution, add 0.15g of benzyl thiol, adjust the pH to alkaline, carry out the thiol-ene click reaction, purge with inert nitrogen gas for 30min, react at 75℃ under light-protected conditions, and then purify to obtain the second modified silicon quantum dots.

[0099] A first modified silicon quantum dot, a second modified silicon quantum dot, and water were mixed (the mass ratio of the first silicon quantum dot to the second silicon quantum dot was 95:5, and the total content of the first silicon quantum dot and the second silicon quantum dot in the water was 0.1%) to obtain an oil displacement agent.

[0100] Example 6:

[0101] Preparation of the first modified silicon quantum dot:

[0102] The preparation of the first modified silicon quantum dot is the same as in Example 3.

[0103] Preparation of the second modified silicon quantum dots:

[0104] 1) Dissolve 2.21g of 98% γ-aminopropyltriethoxysilane and 0.04g of sodium ascorbate in 15ml of deionized water and react at 80℃ for 50min to obtain a dispersion containing second silicon quantum dots. Then, adjust the pH of the dispersion containing second silicon quantum dots to 7.5 with hydrochloric acid, add tetrahydrofuran to the dispersion to precipitate silicon quantum dots, centrifuge and purify to obtain a concentrated solution, freeze-dry to obtain second silicon quantum dots;

[0105] 2) The second silicon quantum dots obtained in step 1) were added to 15 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for 20 min, and nitrogen gas was purged for more than 10 min. Then 0.6 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 55 °C for 5.5 h to obtain the second reaction solution.

[0106] 3) Add 0.54 g of maleic anhydride to the second reaction solution and react at 30 °C for 5.5 h to obtain a solution containing the third intermediate product. Then, add 90 ml of ethyl acetate to the solution containing the third intermediate product to precipitate the third intermediate product. After centrifugation, collect the bottom precipitate, add the third intermediate product to deionized water and adjust the pH to 7.5. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the third intermediate product.

[0107] 4) 100 mmol of N-isopropylacrylamide monomer, 1.0 mmol of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid chain, and 0.3 mmol of 4,4'-azobis(4-cyanopentanoic acid) were dissolved in 40 ml of 1,4-dioxane. Helium was introduced for 10 min, and the reaction was carried out at 70 °C for 11 h to induce polymerization. The product was concentrated by rotary evaporation, and hexane was added to precipitate the product. After centrifugation and purification, the precipitate was obtained and dried under vacuum. The precipitate was added to 15 ml of methanol, nitrogen was introduced, and 10 mmol of sodium borohydride was added. The reaction was carried out at 30 °C for 3 h to induce a reduction bond breaking reaction. After the solution changed from yellow to colorless, insoluble impurities were removed by centrifugation. The reaction solution was then concentrated by rotary evaporation, and hexane was added to precipitate the product to obtain the fourth intermediate product.

[0108] 5) Dissolve 0.5g of the third intermediate in an aqueous methanol solution and add N,N-diisopropylethylamine to obtain the first dispersion. Add 1.5g of the fourth intermediate to the first dispersion, purge with nitrogen for 10 min, and allow the thiol-ene click reaction to occur at 70°C under light-protected conditions. After the reaction is complete, remove the methanol solvent by rotary evaporation and purify to obtain the fifth intermediate.

[0109] 6) Dissolve 0.5g of the fifth intermediate product prepared in step 5) in an aqueous methanol solution, add 0.1g of benzyl thiol, adjust the pH to alkaline, carry out the thiol-ene click reaction, purge with inert nitrogen gas for 10 min, react at 70℃ under light-protected conditions, and then purify to obtain the second modified silicon quantum dots.

[0110] A first modified silicon quantum dot, a second modified silicon quantum dot, and water were mixed (the mass ratio of the first silicon quantum dot to the second silicon quantum dot was 9:1, and the total content of the first silicon quantum dot and the second silicon quantum dot in the water was 0.05%) to obtain an oil displacement agent.

[0111] Comparative Example 1:

[0112] Compared with Example 3, 1,3-propanesulfonic acid lactone was not added in step 2) of Example 3, and the amount of maleic anhydride used in step 3) was 1.03g, while the rest was the same as in Example 3.

[0113] Comparative Example 2:

[0114] 1) Dissolve 2.21 g of 98% γ-aminopropyltriethoxysilane and 0.04 g of sodium ascorbate in 15 ml of deionized water and react at 80℃ for 50 min. After the reaction, a dispersion containing the first silicon quantum dots is obtained. Then, the pH of the dispersion containing the first silicon quantum dots is adjusted to 7.5 using hydrochloric acid. Tetrahydrofuran is then added to the dispersion containing the first silicon quantum dots to precipitate the silicon quantum dots. After centrifugation, a concentrated solution is obtained and lyophilized to obtain the first silicon quantum dots.

[0115] 2) The first silicon quantum dots obtained in step 1) were added to anhydrous dimethyl sulfoxide, ultrasonically dispersed for at least 10 min, and nitrogen gas was passed through for more than 5 min. Then 0.49 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 55 °C for 5.5 h to obtain the first reaction solution.

[0116] 3) Add 0.64 g of maleic anhydride to the first reaction solution and react at 30 °C for 5.5 h to obtain a solution containing the first intermediate product. Then, add 90 ml of ethyl acetate to the solution containing the first intermediate product to precipitate the first intermediate product. After centrifugation, collect the bottom precipitate, add the first intermediate product to deionized water and adjust the pH to 7.5. Disperse the silicon quantum dots by ultrasonication, dialyze and freeze dry to obtain the first silicon quantum dots.

[0117] 4) Mix the first modified silicon quantum dots with water (the content of the first modified silicon quantum dots in the water is 0.05%) to obtain an oil displacement agent.

[0118] Comparative Example 3:

[0119] 1) Dissolve 2.21 g of 98% γ-aminopropyltriethoxysilane and 0.04 g of sodium ascorbate in 15 ml of deionized water and react at 80℃ for 50 min. After the reaction, a dispersion containing the first silicon quantum dots is obtained. Then, the pH of the dispersion containing the first silicon quantum dots is adjusted to 7.5 using hydrochloric acid. Tetrahydrofuran is then added to the dispersion containing the first silicon quantum dots to precipitate the silicon quantum dots. After centrifugation, a concentrated solution is obtained and lyophilized to obtain the first silicon quantum dots.

[0120] 2) The first silicon quantum dots obtained in step 1) were added to 15 ml of anhydrous dimethyl sulfoxide, ultrasonically dispersed for 10 min, and nitrogen gas was passed through for more than 5 min. Then 0.49 g of 1,3-propanesulfonic acid lactone was added, and the mixture was reacted at 55 °C for 5.5 h to obtain the first reaction solution.

[0121] 3) Add pyridine and 1.2g dodecyl chloride to the first reaction solution obtained in step 2), react at 30°C for 5h to carry out acylation reaction, then add 90ml ethyl acetate to precipitate, dialyze and freeze dry to obtain the first silicon quantum dots.

[0122] 4) Mix the first modified silicon quantum dots with water (the content of the first modified silicon quantum dots in the water is 0.05%) to obtain an oil displacement agent.

[0123] Comparative Example 4:

[0124] A commercially available spherical silicon-based nanoparticle oil displacement agent, C2, is produced by Dongying Fukos Petroleum Technology Co., Ltd.

[0125] The oil displacement agents prepared in Examples 1-6 and Comparative Examples 1-4 were tested for turbidity, oil-water interfacial tension and oil displacement performance.

[0126] To demonstrate the stepwise covalent grafting process of the three functional groups on the surface of silicon quantum dots from the perspective of surface elemental composition and relative atomic content, XPS full-spectrum scanning analysis was performed on unmodified silicon quantum dots, the first intermediate product, and Examples 2 and 5.

[0127] To demonstrate the successful covalent grafting of the three functional groups (negatively charged sulfonic acid group, pH-responsive carboxyl group, and temperature-responsive PNIPAM group) described in this invention, FTIR comparative analysis was performed on Examples 2 and 5, the first intermediate product, and unmodified silicon quantum dots.

[0128] To intuitively explore the synergistic effect of functional group ratio and pH environment on the dispersion state of silicon quantum dots at the microscale, the micromorphology of Examples 2 and 5 was characterized by transmission microscopy (TEM) under acidic (pH≈4) and alkaline (pH≈10) conditions, respectively. The dispersant was taken from field water in a block of Daqing Oilfield and filtered through a 0.45 μm pore size filter membrane.

[0129] Table 1 Turbidity Detection

[0130]

[0131] As can be seen from the results in Table 1, the turbidity of Examples 1-6, Comparative Examples 2 and 3 at 25°C and 65°C is all below 10, indicating that the oil displacement agents of Examples 1-6 are relatively stable. The turbidity of Comparative Examples 1 and 4 at 65°C is both above 10, indicating that the oil displacement agents of Comparative Examples 1 and 4 are unstable.

[0132] Table 2 Interfacial tension detection (different temperatures and pH values)

[0133]

[0134] As can be seen from the results in Table 2 at 25°C: The equilibrium interfacial tension of each sample in Examples 1-6 was not significantly different under acidic, neutral, and alkaline conditions. This is because the PNIPAM segments have strong hydrophilicity and provide steric hindrance at room temperature. Even for Examples 4-6, the benzene rings on the surface were covered by the extended PNIPAM chains, weakening the hydrophobic effect, so the interfacial tension was only slightly lower than that of Examples 1-3. The equilibrium interfacial tension of Comparative Example 1 was higher than that of Examples 1-6 under acidic conditions, but its equilibrium interfacial tension was basically the same as that of Examples 1-6 under neutral and alkaline conditions. This is because under acidic conditions, the carboxyl groups on the surface of Comparative Example 1 were completely protonated, lacking groups that provide electrostatic repulsion. The steric hindrance provided by PNIPAM alone was insufficient to maintain system stability, and the aggregated silicon quantum dots could not spontaneously diffuse to the interface to reduce the interfacial tension. The equilibrium tension performance of Comparative Example 2 was not significantly different from that of Examples 1-6. Comparative Example 4 was worse than Examples 1-6 because the diffusion coefficient of large-sized silica nanoparticles was significantly lower than that of extremely small silicon quantum dots, thus the effect of reducing interfacial tension was minimal.

[0135] As shown in Table 2 at 65°C, the equilibrium interfacial tensions of Examples 4-6 were lower than those of Examples 1-3 at the corresponding pH levels under different acidity and alkalinity conditions. They also exhibited a characteristic of lower interfacial tension under acidic conditions and higher interfacial tension under alkaline conditions. This is because the temperature response switch was triggered upon heating, causing the PNIPAM segments to rapidly hydrophobically shrink, significantly shifting the hydrophilic-lipophilic balance towards hydrophobicity, thus significantly reducing the interfacial tension. Furthermore, under acidic conditions, a large number of carboxyl groups on the silicon quantum dot surface protonated, transforming from strongly hydrophilic to weakly hydrophilic, further reducing the interfacial tension. For Examples 4-6, the shrinkage of PNIPAM resulted in a large number of exposed benzene rings on its surface, further promoting the shift in the hydrophilic-lipophilic balance, thus exhibiting stronger responsiveness and higher interfacial activity compared to Examples 1-3. However, for Comparative Examples 1-4, the interfacial tension increased after heating. In Comparative Example 1, the surface PNIPAM shrinks upon heating, no longer providing steric hindrance. Furthermore, due to the lack of electrostatic repulsion in the silicon quantum dots under acidic conditions, aggregation is more severe, further increasing the interfacial tension. Conversely, as pH increases, the deprotonation of carboxyl groups provides electrostatic repulsion, thus reducing the interfacial tension under alkaline conditions, although it remains relatively high. In Comparative Examples 2, 3, and 4, the interfacial tension increases upon heating. This is because heating promotes molecular thermal motion, leading to slight aggregation of the silicon quantum dots. Since they all lack temperature-responsive groups, they do not exhibit a temperature response. It is noteworthy that although Comparative Example 3 has a lower interfacial tension at room temperature than Examples 1-6, it lacks responsiveness, and its interfacial activity is significantly weaker than Examples 1-6 at high formation temperatures. This will result in greater injection difficulty and a lower actual oil displacement effect compared to Examples 1-6.

[0136] Table 3 Oil displacement performance (65℃)

[0137]

[0138] As can be seen from the results in Table 3, the nano-recovery rate, subsequent water-drive recovery rate and total recovery rate of Examples 1-3 are all higher than those of Comparative Examples 1-4, and the nano-drive recovery rate of Examples 4-6 is higher than that of Examples 1-3.

[0139] From the appendix Figure 1 It can be seen that the functional groups (sulfonic acid group, carboxyl group, PNIPAM group and benzyl group) described in this invention have been successfully grafted.

[0140] All samples were taken at 1080 cm⁻¹. -1 It exhibits strong peaks of asymmetric stretching vibrations of the Si-O-Si framework near the wavenumber, and at 3400-3500 cm⁻¹ -1 The presence of broad OH and NH stretching vibration absorption bands near the wavenumber confirms the synthesis of the amino-silicon quantum dot core. For the first intermediate product, compared to unmodified silicon quantum dots, the absorption band at 1180 cm⁻¹ is significantly higher. -1 A significant S=O asymmetric stretching vibration shoulder was formed near the wavenumber, directly confirming the initial introduction of the negatively charged sulfonic acid group (-SO3H), at 2900 cm⁻¹. -1 The intensity of the CH stretching vibration peak near the wavenumber increases significantly, reaching 1720 cm⁻¹. -1 A relatively obvious C=O stretching vibration peak appears near the wavenumber and at 1510 cm⁻¹. -1 The increased wavenumber of the CN stretching vibration peaks further confirms that maleic anhydride reacts with the remaining amino group to form an amide bond, providing an active site for the subsequent click reaction. For Example 2, compared to the first intermediate, the spectrum at 2900 cm⁻¹... -1 The intensity of the CH stretching vibration peak near the wavenumber increased significantly, preliminarily proving the successful grafting of the macromolecule PNIPAM. Furthermore, the peak intensity at 1720 cm⁻¹... -1 The enhanced C=O stretching vibration peak near the wavenumber is due to the introduction of more amide bonds by PNIPAM. For Example 5, at 760 cm⁻¹... -1 Characteristic peaks of the benzene ring appear near the wavenumber, and at 2900 cm⁻¹ -1 The intensity of the CH stretching vibration peak near the wavenumber further increases, indicating a successful grafting of the newly introduced benzyl group compared to Example 2.

[0141] From the appendix Figure 2 It can be seen that the functional groups (sulfonic acid group, carboxyl group, PNIPAM group and benzyl group) described in this invention have been successfully grafted.

[0142] All samples showed clearly detectable Si 2p peaks at approximately 100.2 eV, Si 2s peaks at approximately 165.6 eV, O 1s peaks at approximately 532.3 eV, C 1s peaks at approximately 284.0 eV, and N 1s peaks at approximately 400.5 eV, indicating that the silicon quantum dot surface possesses a Si-O-Si framework. For the first intermediate product, compared to the unmodified silicon quantum dots, the intensity of the S 2p peak at approximately 165.6 eV (overlapping with the Si 2s peak) increased. Since no silicon-based modifier was introduced, this preliminarily indicates successful grafting of sulfonic acid groups. The increased intensity of the O 1s peak at approximately 532.3 eV and the C 1s peak at approximately 284.0 eV further confirms the successful ring-opening reaction between the remaining amino groups on the silicon quantum dot surface and maleic anhydride. For Example 2, compared to the first intermediate product, the intensity of the S2p peak (overlapping with the Si2s peak) at approximately 165.6 eV was slightly increased. Since no silicon-based modifier was introduced, the click reaction can be preliminarily determined to have proceeded successfully. Simultaneously, the significantly increased intensities of the O1s peak at approximately 532.3 eV, the C1s peak at approximately 284.0 eV, and the N1s peak at approximately 400.5 eV further confirm the successful grafting of PNIPAM. For Example 5, the introduction of the benzyl group further increased the intensity of the C1s peak at approximately 284.0 eV compared to Example 2.

[0143] From the appendix Figure 3 It can be seen that for Examples 2 and 5, good monodispersity was maintained in the aqueous phase under both acidic and alkaline conditions. This is attributed to the constant electrostatic repulsion provided by the appropriate amount of sulfonic acid groups on the surface of the silicon quantum dots, which hindered the aggregation of silicon quantum dots. For Comparative Example 1, under alkaline conditions, the carboxyl groups on the surface of the silicon quantum dots were deprotonated, which significantly enhanced the electrostatic repulsion, thus maintaining monodispersity in the aqueous phase. However, under acidic conditions, the carboxyl groups were deprotonated, losing the electrostatic repulsion, and the silicon quantum dots aggregated significantly, exhibiting macroscopic instability.

[0144] Although embodiments of the invention have been presented and described (see the detailed description above), it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An oil displacement agent that responds to both temperature and pH, characterized in that, Including grafting Groups and The first modified silicon quantum dot has a particle size of less than 10 nm.

2. An oil displacement agent that responds to both temperature and pH, characterized in that, It includes a first modified silicon quantum dot and a second modified silicon quantum dot, wherein the first modified silicon quantum dot includes... Groups and The second modified silicon quantum dot includes groups, Groups, Groups and The particle size of both the first modified silicon quantum dot and the second modified silicon quantum dot is less than 10 nm.

3. The temperature- and pH-responsive oil displacement agent according to claim 2, characterized in that, The mass ratio of the first modified silicon quantum dot to the second modified silicon quantum dot is (70-95):(5-30).

4. The temperature- and pH-responsive oil displacement agent according to claim 1 or 2, characterized in that, The preparation steps of the first modified silicon quantum dot include: 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained. 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained. 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product; 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained. 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots.

5. The temperature- and pH-responsive oil displacement agent according to claim 2, characterized in that, The preparation steps of the second modified silicon quantum dots include: 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the second silicon quantum dots are obtained. 2) The second silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the second reaction solution was obtained. 3) Add maleic anhydride to the second reaction solution, react and purify to obtain the third intermediate product; 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in a fourth solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to a fifth solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction and bond breaking reaction. After the reaction and purification, the fourth intermediate product was obtained. 5) Dissolve the third intermediate product prepared in step 3) in the sixth solvent and add a catalyst to obtain the first dispersion. Add the fourth intermediate product to the first dispersion and carry out the thiol-ene click reaction. After the reaction, purify to obtain the fifth intermediate product. 6) Dissolve the fifth intermediate in the seventh solvent, add an appropriate amount of benzyl thiol, adjust the pH to alkaline, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the second modified silicon quantum dots.

6. A method for preparing an oil displacement agent that responds to both temperature and pH, characterized in that, The preparation method includes the following steps: 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained. 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained. 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product; 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained. 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots. 6) Mix an appropriate amount of the first modified silicon quantum dots with water to obtain an oil displacement agent.

7. A method for preparing an oil displacement agent that responds to both temperature and pH, characterized in that, The preparation method includes the following steps: 1) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the first silicon quantum dot is obtained. 2) The first silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the first reaction solution was obtained. 3) Add maleic anhydride to the first reaction solution, react and purify to obtain the first intermediate product; 4) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in the first solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to the second solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, the second intermediate product was obtained. 5) Dissolve the first intermediate in the third solvent, add the catalyst and an appropriate amount of the second intermediate, and carry out the thiol-ene click reaction. After the reaction, purify to obtain the first modified silicon quantum dots. 6) Take an appropriate amount of γ-aminopropyltriethoxysilane and sodium ascorbate and prepare a solution of the two. After reaction and purification, the second silicon quantum dots are obtained. 7) The second silicon quantum dot was added to anhydrous dimethyl sulfoxide, and then 1,3-propanesulfonic acid lactone was added. After the reaction, the second reaction solution was obtained. 8) Add maleic anhydride to the second reaction solution, react and purify to obtain the third intermediate product; 9) Using N-isopropylacrylamide as monomer, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as chain transfer agent, and adding a thermal initiator, the product was dissolved in a fourth solvent and polymerized under inert gas protection. After precipitation and purification, the product was added to a fifth solvent, inert gas was introduced, and a reducing agent was added to carry out a reduction bond breaking reaction. After the reaction and purification, a fourth intermediate product was obtained. 10) Dissolve the third intermediate in the sixth solvent and add a catalyst to obtain the first dispersion. Add the fourth intermediate to the first dispersion and carry out the thiol-ene click reaction. After the reaction, purify to obtain the fifth intermediate. 11) Dissolve the fifth intermediate in the seventh solvent, add an appropriate amount of benzyl thiol, adjust the pH to alkaline, carry out the thiol-ene click reaction, and purify after the reaction to obtain the second modified silicon quantum dots. 12) Mix appropriate amounts of first modified silicon quantum dots, second modified silicon quantum dots and water to obtain an oil displacement agent.

8. The application of an oil displacement agent that is both temperature and pH responsive, characterized in that, Oil displacement agents are used to improve the recovery rate of oil fields.

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