Nano-fluid with anti-swelling and oil-displacing effects as well as preparation method and application of nano-fluid

Abstract

The invention discloses a nanofluid with anti-swelling and oil-displacing effects as well as a preparation method and application thereof, and belongs to the technical field of oil exploitation. The preparation method comprises the following steps: carrying out condensation reaction on aminated nano SiO2 and glycine to generate an amide-containing intermediate; the preparation method comprises the following steps: respectively mixing an amide-containing intermediate and 2, 3-epoxypropyl trimethyl ammonium chloride with a solvent A to prepare an amide-containing intermediate solution and a 2, 3-epoxypropyl trimethyl ammonium chloride solution, and carrying out quaternization reaction after mixing to synthesize the nanofluid with anti-swelling and oil-displacing effects. The nanofluid as an anti-swelling agent and an oil-displacing agent can be applied to the exploitation process of low-permeability oil reservoirs, after the nanofluid reaches the response temperature, amido bonds are broken, quaternary ammonium salt and aminated nano-SiO2 are released, the quaternary ammonium salt as the anti-swelling agent and the aminated nano-SiO2 as the oil-displacing agent can be used as an anti-swelling agent and an aminated nano-SiO2 oil-displacing agent, and the oil-displacing agent can be used as an The technical problem that a chemical agent with a single function is difficult to meet the requirements of low-permeability oil reservoirs can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil extraction, and particularly relates to a nanofluid having anti-swelling and oil-displacing effects, a preparation method thereof, and an application thereof. Background Art

[0002] For low-permeability oilfields, in order to improve the production efficiency, adding anti-swelling agents and oil-displacing agents is an essential measure. During the process of oilfield water injection production, due to the swelling of clay minerals when encountering water, it will cause the blockage of formation pores, resulting in the decrease of formation permeability, affecting the production efficiency and even making it impossible to carry out secondary water injection development. In order to better protect the reservoir and develop the oilfield, it is necessary to use anti-swelling agents to inhibit clay swelling. Common anti-swelling agents include inorganic salts, inorganic polymers, cationic surfactants, organic cationic polymers, and non-ionic surfactants. Inorganic salt anti-swelling agents are prone to failure when the external soil environment changes and are not resistant to water scouring, resulting in a short effective period; inorganic polymer anti-swelling agents can only form polymers through hydroxyl complexation in acidic or weakly acidic systems to achieve long-term stable clay, so their use has limitations; cationic surfactant anti-swelling agents are likely to change the soil from hydrophilic to lipophilic, thereby reducing the oil and gas phase permeability and generating polymer precipitation with anions, which is not conducive to subsequent oil displacement; organic cationic polymer anti-swelling agents have insignificant temperature resistance during use, and the synthesis process is relatively expensive; non-ionic surfactant anti-swelling agents have a cumbersome synthesis process and high costs. Oil-displacing agents are one of the important means to improve the oil recovery rate, and can improve the oil recovery rate by reducing the oil-water interfacial tension, changing the wettability of rocks, increasing the viscosity of the aqueous phase, etc. Common oil-displacing agents mainly include surfactant oil-displacing agents and polymer oil-displacing agents. Surfactant oil-displacing agents can effectively reduce the oil-water interfacial tension and have a strong displacement ability for residual oil. However, they are easily affected by formation rock adsorption and formation water salinity, resulting in a decline in their performance and low oil displacement efficiency. Polymer oil-displacing agents can improve the displacement efficiency by increasing the viscosity of the injected fluid, improving the mobility ratio, and increasing the sweep coefficient. However, they have poor salt resistance and temperature resistance and are not suitable for high-temperature and high-salt oil reservoirs, resulting in limitations in their application scope.

[0003] In view of the problems existing in the above-mentioned existing anti-swelling agents and oil-displacing agents, as well as the complex reservoir conditions, diverse fluid properties, and increasing development requirements, single-functional chemical agents are difficult to meet the needs of complex reservoirs. Therefore, there is an urgent need to design an intelligent response substance with integrated anti-swelling and oil-displacing functions, which can respond and release anti-swelling agents and oil-displacing agents at a specific temperature in the formation. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a nanofluid having anti-swelling and oil-displacing effects, a preparation method thereof, and an application thereof, so as to solve the technical problem that single-functional chemical agents are difficult to meet the needs of low-permeability reservoirs.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions: The present invention provides a preparation method of a nanofluid with swelling prevention and oil displacement effects, comprising the following steps: Condense amino-functionalized nano-SiO 2 and glycine to form an amide-containing intermediate; Mix the amide-containing intermediate and 2,3-epoxypropyltrimethylammonium chloride with solvent A respectively to prepare an amide-containing intermediate solution and a 2,3-epoxypropyltrimethylammonium chloride solution, and carry out a quaternization reaction after mixing to synthesize a nanofluid with swelling prevention and oil displacement effects.

[0006] In one embodiment, the mass concentration of the amide-containing intermediate solution is 1.5% - 2%; the mass concentration of the 2,3-epoxypropyltrimethylammonium chloride solution is 1.5% - 2%.

[0007] In one embodiment, the molar ratio of the amide-containing intermediate in the amide-containing intermediate solution to the 2,3-epoxypropyltrimethylammonium chloride in the 2,3-epoxypropyltrimethylammonium chloride solution is 1:1 - 1.5:1.

[0008] In one embodiment, the temperature of the quaternization reaction is 60°C - 80°C, and the time of the quaternization reaction is 6h - 12h; the solvent A is anhydrous ethanol or acetonitrile.

[0009] In one embodiment, the process of condensing amino-functionalized nano-SiO 2 and glycine to form an amide-containing intermediate is as follows: Disperse amino-functionalized nano-SiO 2 and glycine in solvent B respectively to obtain an amino-functionalized nano-SiO 2 suspension and a glycine solution; Add a condensing agent to the glycine solution, stir to activate the carboxyl group of glycine, and add the activated glycine solution to the amino-functionalized nano-SiO 2 suspension for condensation reaction, and then carry out separation, washing and drying in sequence.

[0010] In one embodiment, the solvent B is dimethyl sulfoxide or N,N-dimethylformamide; the condensing agent is a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and the molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide is 1:1 - 1:1.2.

[0011] In one embodiment, the mass fraction of the glycine solution is 1% - 1.5%; the amino-functionalized nano-SiO 2The mass fraction of the suspension is 1% - 1.5%; The glycine in the activated glycine solution and the aminated nano-SiO 2 in the suspension 2 have a molar ratio of 1:1 - 1:1.5.

[0012] In one embodiment, the temperature of the condensation reaction is 30°C - 50°C; the time of the condensation reaction is 12 h - 18 h.

[0013] The present invention also provides a nano-fluid with anti-swelling and oil-displacing effects prepared by the preparation method of the nano-fluid with anti-swelling and oil-displacing effects according to the above.

[0014] The present invention also provides an application of a nano-fluid with anti-swelling and oil-displacing effects prepared by the preparation method of the nano-fluid with anti-swelling and oil-displacing effects according to the above as an anti-swelling agent and an oil-displacing agent in the exploitation process of low-permeability oil reservoirs. After the nano-fluid with anti-swelling and oil-displacing effects reaches the response temperature, the amide bond breaks, releasing quaternary ammonium salt and aminated nano-SiO 2 , the quaternary ammonium salt is used as an anti-swelling agent, and the aminated nano-SiO 2 is used as an oil-displacing agent.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a preparation method of a nano-fluid with anti-swelling and oil-displacing effects. In this preparation method, H 2 N-SiO 2 and glycine undergo a condensation reaction to form a product containing an amide bond. Introducing the amide bond is the key to the application of this nano-fluid in the formation. The amide bond will break at the formation temperature, decomposing the main substances used as an anti-swelling agent and an oil-displacing agent. The reaction of the intermediate containing an amide structure and 2,3-epoxypropyltrimethylammonium chloride (EPTAC) introduces the quaternary ammonium salt, and the quaternary ammonium salt is the anti-swelling agent in this anti-swelling-oil-displacing integrated substance.

[0016] The present invention prepares a nano-fluid with anti-swelling and oil-displacing effects and its application in the exploitation process of low-permeability oil reservoirs. The above-mentioned substance can achieve the integration of anti-swelling and oil-displacing, specifically: after reaching the response temperature, the amide bond breaks, releasing quaternary ammonium salt and aminated nano-SiO 2 , the quaternary ammonium salt is used as an anti-swelling agent, and the aminated nano-SiO 2 is used as an oil-displacing agent. In this nano-fluid, the quaternary ammonium salt adsorbs on the clay mineral first, avoiding the adsorption loss of aminated nano-SiO 2 with the clay, improving the effective component of aminated nano-SiO 2 acting on oil displacement. The quaternary ammonium salt acts as both a sacrificial agent and an anti-swelling agent.

[0017] Aminated nano-SiO₂ in nanofluid 2 As a flooding agent, it has a large specific surface area and good dispersibility, and can enter the tiny pores in the oil reservoir. And aminated nano-SiO₂ 2 can interact with the acidic components in crude oil through the amino groups on its surface, reduce the interfacial tension between oil and water, and greatly improve the oil displacement efficiency. In addition, the nanofluid can enter the tiny pores to displace the residual oil through its nano-size effect, so its oil displacement efficiency is relatively high.

[0018] And in the formation temperature range of 80 °C to 90 °C, the amide bond in this nanofluid breaks to release quaternary ammonium salts. This temperature-responsive release method avoids the premature consumption of quaternary ammonium salts before reaching the formation, and can ensure slow and continuous release in a specific formation environment, extending its effective action time. In addition, the quaternary ammonium salts have stable chemical properties and can maintain their anti-swelling chemical activity for a long time, thus continuously playing the anti-swelling role. The aminated nano-SiO₂ in this nanofluid 2 has a large specific surface area, enhancing the contact area with crude oil and the oil displacement effect. And the nanofluid can also maintain good performance in high-temperature and high-salt oil reservoirs, with a wider application range. Brief Description of the Drawings

[0019] Figure 1 is the schematic diagram of the modification principle of SiO₂ amination by γ-aminopropyltrimethoxysilane; 2 Figure 2 is the reaction schematic diagram of H 2 N-SiO₂ 2 and glycine; Figure 3 is the reaction schematic diagram of the reaction involving amide intermediate and quaternary ammonium salt; Figure 4 is the slow-release equation of the anti-swelling and oil-displacing integrated nanofluid; Figure 5 is the anti-swelling rate test chart of nanofluids with different concentrations provided by the present invention; Figure 6 is the oil recovery test chart of water flooding and nanofluids with different concentrations provided by the present invention. Detailed Embodiments

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art for the present invention. In case of conflicts, the definitions in this specification shall prevail.

[0021] ​The theories or mechanisms described and disclosed herein, whether right or wrong, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0022] In this text, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0023] In this text, unless otherwise specified, terms such as "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0024] In this text, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0025] The present invention provides a preparation method of a nanofluid having anti-swelling and oil-displacing effects. The preparation method is as follows: The nano-SiO is aminated with an amino-silane coupling agent. 2 The aminated nano-SiO 2 and glycine are subjected to a condensation reaction to generate an amide-containing intermediate; subsequently, the amide-containing intermediate and 2,3-epoxypropyltrimethylammonium chloride are subjected to a quaternization reaction to synthesize a nanofluid having anti-swelling and oil-displacing effects.

[0026] The present invention provides a preparation method of a nanofluid having anti-swelling and oil-displacing effects, comprising the following steps: Step 1: The nano-SiO is aminated with an amino-silane coupling agent to obtain aminated nano-SiO. 2 2 ; Step 2: The aminated nano-SiO 2 and glycine are subjected to a condensation reaction to generate an amide-containing intermediate; Step 3: The amide-containing intermediate and 2,3-epoxypropyltrimethylammonium chloride are respectively mixed with solvent A to prepare an amide-containing intermediate solution and a 2,3-epoxypropyltrimethylammonium chloride solution. After mixing, a quaternization reaction is carried out to synthesize a nanofluid having anti-swelling and oil-displacing effects.

[0027] In Step 1, the nano-SiO is aminated with an amino-silane coupling agent. 2Amination to obtain aminated nano-SiO 2 The process is as follows: S11: Prepare a nano-SiO 2 particle solution with deionized water as the solvent; prepare an amino silane coupling agent solution with deionized water as the solvent; ultrasonically disperse at room temperature for 25 min to 35 min.

[0028] S12: After mixing the nano-SiO 2 particle solution and the amino silane coupling agent solution, adjust the pH to 7 - 8 with phosphate buffer solution, stir in a water bath at 70°C to 80°C for 8 h to 10 h, and the amino silane coupling agent will aminate the nano-SiO 2 , and then successively carry out centrifugation, washing with deionized water and drying to obtain aminated nano-SiO 2 (H 2 N-SiO 2 ).

[0029] Among them, the mass concentration of the nano-SiO 2 particle solution is 1% - 1.5%; the mass concentration of the amino silane coupling agent solution is equal to that of the nano-SiO 2 particle solution; the solute mass in the amino silane coupling agent solution is equal to the solute mass in the nano-SiO 2 particle solution.

[0030] Among them, the amino silane coupling agent in the amino silane coupling agent solution is one of γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and N-cyclohexyl-γ-aminopropyltrimethoxysilane.

[0031] In step two, the process of the aminated nano-SiO 2 and glycine undergoing a condensation reaction to form an amide intermediate is as follows: S21: Disperse the aminated nano-SiO 2 and glycine in solvent B respectively. After the aminated nano-silica dissolves in the solvent, ultrasonically treat for 15 min to 30 min to respectively obtain an aminated nano-SiO 2 suspension and a glycine solution; S22: Add a condensing agent to the glycine solution, stir for 30 min to 60 min to activate the carboxyl group of glycine, add the activated glycine solution to the aminated nano-SiO 2 suspension, carry out a condensation reaction, and then successively carry out separation, washing and drying.

[0032] Among them, the mass fraction of the glycine solution is 1% - 1.5%; the mass fraction of the aminated nano-SiO 2 suspension is 1% - 1.5%; the activated glycine in the activated glycine solution and the aminated nano-SiO 2Aminated nano-SiO in suspension 2 The molar ratio is 1:1 to 1:1.5.

[0033] Among them, solvent B is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF); the condensing agent is a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N-hydroxysuccinimide (NHS), and the molar ratio of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide is 1:1 to 1:1.2.

[0034] Among them, the temperature of the condensation reaction is 30°C to 50°C, and the time is 12 h to 18 h.

[0035] In step three, the mass concentration of the amide intermediate solution is 1.5% to 2%; the mass concentration of the 2,3-epoxypropyltrimethylammonium chloride solution is 1.5% to 2%; the molar ratio of the amide intermediate in the amide intermediate solution to the 2,3-epoxypropyltrimethylammonium chloride in the 2,3-epoxypropyltrimethylammonium chloride solution is 1:1 to 1.5:1.

[0036] In step three, solvent A is absolute ethanol or acetonitrile. The temperature of the quaternization reaction is 60°C to 80°C, and the time is 6 h to 12 h.

[0037] The nano-fluid with anti-swelling and oil-displacing effects prepared by the above preparation method can achieve the integration of anti-swelling and oil-displacing. This substance is an intelligent responsive substance for the integration of anti-swelling and oil-displacing, and this substance can respond and release the anti-swelling agent and the oil-displacing agent at a specific formation temperature. After reaching the response temperature, the amide bond breaks, releasing the quaternary ammonium salt and aminated nano-SiO 2 , the quaternary ammonium salt is used as the anti-swelling agent, and aminated nano-SiO 2 is used as the oil-displacing agent. When in use, the two chemical agents exist separately and independently. The anti-swelling and oil-displacing effects only synergistically enhance each other without interfering with each other, and the anti-swelling effect is exerted at the far end. The anti-swelling agent not only has a long-lasting anti-swelling effect, but also can be used as a sacrificial agent to reduce the adsorption loss of the oil-displacing agent in the formation, thereby improving the oil-displacement efficiency. And the oil-displacing agent has excellent stability, is not easily affected by the formation environment, has a high oil-displacement efficiency and a wide application range. In addition, the quaternary ammonium salt has stable chemical properties and a long anti-swelling effective period. Aminated nano-SiO 2 As an oil-displacing agent, it has a large specific surface area and good dispersibility, and can enter the tiny pores in the oil reservoir, greatly improving the oil-displacement efficiency.

[0038] The specific preparation process of a nano-fluid with anti-swelling and oil-displacing effects in the present invention is as follows: S1: Aminated nano-SiO 2Preparation: Prepare an amino-silane coupling agent solution with a mass concentration of 1% - 1.5% using deionized water as the solvent, and prepare an SiO 2 nanoparticle solution with a mass concentration of 1% - 1.5% using deionized water as the solvent. Ultrasonically disperse it at room temperature for 25 min - 35 min. After the particles are evenly dispersed, add an amino-silane coupling agent solution with the same mass concentration as the above SiO 2 nanoparticle solution and the same solute mass to the SiO 2 nanoparticle solution. Adjust the pH of the solution to 7 - 8 with phosphate buffer. Transfer this solution to a three-necked flask and stir it in a water bath at 70°C - 80°C for 8 h - 10 h. Separate the nanoparticles from the solvent with a centrifuge, and wash them three times repeatedly with deionized water. The obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) is placed in a vacuum drying oven at 100°C - 120°C and dried for 20 h - 24 h, then ground for standby.

[0039] S2: Preparation of amide intermediate: Disperse the above amino-functionalized nano-SiO 2 in a dispersion solvent, and ultrasonically treat it for 15 min - 30 min to obtain an amino-functionalized nano-SiO 2 suspension with a mass fraction of 1% - 1.5%. Prepare a glycine solution with a mass fraction of 1% - 1.5% using the same solvent. Add appropriate condensing agents to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 30 min - 60 min. Slowly drip the activated glycine solution into the amino-functionalized nano-SiO 2 suspension, and the molar ratio of the two is 1:1 - 1:1.5. Stir and react at 30°C - 50°C for 12 h - 18 h. After the reaction is completed, separate the product by centrifuge. Wash the product 3 - 5 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed amide intermediate product in a vacuum drying oven at 40°C - 60°C for 6 h - 8 h.

[0040] Among them, the molar ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide that make up the condensing agent is 1:1 - 1:1.2.

[0041] S3: Preparation of swelling prevention - oil displacement nanofluid: Prepare a 2,3 - epoxypropyltrimethylammonium chloride solution with a mass concentration of 1.5% - 2% and an amide intermediate solution using a solvent, and the molar ratio of the two is 1:1 - 1:1.5. Add the amide intermediate solution into a three - necked flask, and slowly add the 2,3 - epoxypropyltrimethylammonium chloride solution into the three - necked flask while continuously stirring. Heat the reaction system to 60°C - 80°C and react for 6h - 12h, during which continuous stirring is carried out and an inert gas is introduced for protection. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with swelling prevention and oil displacement effects.

[0042] In S1, the amino - silane coupling agent is specifically one of γ - aminopropyltrimethoxysilane, γ - ureidopropyltriethoxysilane, and N - cyclohexyl - γ - aminopropyltrimethoxysilane.

[0043] In S2, the step of dispersing the amino - functionalized nano - SiO 2 in a solvent, and the solvent is one of dimethyl sulfoxide (DMSO) and N,N - dimethylformamide (DMF).

[0044] In S2, the condensing agent is a mixed solvent of 1 - ethyl - 3 - (3 - dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N - hydroxysuccinimide (NHS), and the two are specifically mixed and used according to a molar ratio of 1:1 - 1:1.2.

[0045] In S3, the solvents of the amide intermediate solution and the 2,3 - epoxypropyltrimethylammonium chloride solution are one of absolute ethanol and acetonitrile.

[0046] Taking γ - aminopropyltrimethoxysilane in the amino - silane coupling agent as an example, the corresponding principle analysis is as follows: In order to overcome the difficulty that the chemical agents with single functions in the prior art are difficult to meet the requirements of low - permeability reservoirs, the present invention provides a nanofluid with swelling prevention and oil displacement effects. The amide bond breaks at 80°C - 90°C in the formation, decomposing into amino - functionalized nano - SiO 2 and quaternary ammonium salt, where the amino - functionalized nano - SiO 2 is an oil - displacement agent and the quaternary ammonium salt is a swelling - prevention agent.

[0047] First, use an amino - silane coupling agent to carry out the amino - functionalization of nano - SiO 2 , Figure 1 Figure for the modification principle of the amino - functionalization of nano - SiO 2 by γ - aminopropyltrimethoxysilane. The modification principles of the other two amino - silane coupling agents for the amino - functionalization of nano - SiO 2 are similar to Figure 1 this.

[0048] Secondly, the aminated nano-SiO 2 is abbreviated as H 2 N-SiO 2 . H 2 N-SiO 2 and glycine are subjected to a condensation reaction to form a product containing an amide bond. Figure 2 is the chemical equation of the condensation reaction, and a product containing an amide bond is formed through the condensation reaction. Introducing the amide bond is the key to the application of this nanofluid in the formation. The amide bond will break at 80 °C to 90 °C in the formation, and decompose the main substances as swelling inhibitors and oil displacement agents.

[0049] Finally, Figure 3 is the quaternization reaction of the intermediate containing an amide structure and 2,3-epoxypropyltrimethylammonium chloride (EPTAC). This reaction introduces a quaternary ammonium salt, and the quaternary ammonium salt is the swelling inhibitor in this swelling inhibition-oil displacement integrated substance.

[0050] The action mechanism of this nanofluid with swelling inhibition and oil displacement effects is based on its unique chemical structure and reaction characteristics in the reservoir environment. The nanofluid contains a specific amide bond structure. When the formation temperature reaches 80 °C to 90 °C, the amide bond breaks, decomposing the quaternary ammonium salt as a swelling inhibitor, and aminated nano-SiO 2 acts synergistically as an oil displacement agent. Figure 4 is the slow release equation of this nanofluid.

[0051] On the other hand, the present invention provides an application of a nanofluid with swelling inhibition and oil displacement effects prepared by the above preparation method in the exploitation of low-permeability oilfields.

[0052] At a formation temperature of 80 °C to 90 °C, the quaternary ammonium salt and aminated nano-SiO 2 are released through the breakage of the amide bond, respectively playing the roles of swelling inhibition and oil displacement. The quaternary ammonium salt, as a swelling inhibitor, has a long swelling inhibition effective period and can also reduce the adsorption loss of the oil displacement agent; aminated nano-SiO 2 as an oil displacement agent is not easily affected by the formation environment, has a high oil displacement efficiency and a wide application range, thereby achieving efficient oilfield exploitation.

[0053] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0054] In the following examples, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. In the following examples, various raw materials are used. Unless otherwise specified, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0055] Example 1 Prepare a 1% γ-aminopropyltrimethoxysilane solution with 1 g of γ-aminopropyltrimethoxysilane and 99 g of deionized water. Prepare a 1% SiO 2 nanoparticle solution with 1 g of SiO 2 nanoparticles and 99 g of deionized water, and ultrasonically disperse it at room temperature for 25 min. After the particles are evenly dispersed, add 50 g of the γ-aminopropyltrimethoxysilane solution and 50 g of the SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 7 with phosphate buffer. Transfer this solution to a three-necked flask, stir it in a 70 °C water bath for 10 h, separate the nanoparticles from the solvent with a centrifuge, wash it repeatedly with deionized water 3 times, and obtain the amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) and place it in a vacuum drying oven at 100 °C for drying for 24 h, then grind it for standby.

[0056] Disperse 1.1 g of the above amino-functionalized nano-SiO 2 in 108.9 g of DMSO and ultrasonically treat it for 30 min. Prepare a glycine solution with 99 g of DMSO and 1 g of glycine. Add 1 g of EDC·HCl and 0.6 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 30 min. Slowly add 50 g of the activated glycine solution dropwise to 50 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 30 °C for 18 h. After the reaction is completed, separate the product by centrifuge. Wash the product 5 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 40 °C for 8 h.

[0057] Prepare a 1.5% (by mass) solution of 2,3-epoxypropyltrimethylammonium chloride using 1 g of 2,3-epoxypropyltrimethylammonium chloride and 65.67 g of absolute ethanol. Prepare a solution containing an amide intermediate using 1.026 g of the amide intermediate and 67.374 g of absolute ethanol. Add 60 g of the solution containing the amide intermediate to a three-necked flask, and slowly add 60 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 60 °C and react for 12 h, continuously stirring and introducing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by centrifugation. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0058] Example 2 Prepare a 1.5% (by mass) solution of γ-ureidopropyltriethoxysilane using 1 g of γ-ureidopropyltriethoxysilane and 65.67 g of deionized water. Prepare a 1.5% (by mass) solution of SiO 2 nanoparticles using 1 g of SiO 2 nanoparticles and 65.67 g of deionized water, and ultrasonically disperse for 35 min at room temperature. After the particles are evenly dispersed, add 50 g of γ-aminopropyltrimethoxysilane solution and 50 g of SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 8 with phosphate buffer. Transfer this solution to a three-necked flask, stir for 8 h in a water bath at 80 °C, separate the nanoparticles from the solvent by centrifugation, and wash repeatedly with deionized water 3 times. Place the obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) in a vacuum drying oven at 120 °C for 20 h, then grind and set aside.

[0059] Disperse 0.73 g of the above amino-functionalized nano-SiO 2 in 47.94 g of DMF and ultrasonically treat for 15 min. Prepare a glycine solution using 65.67 g of DMF and 1 g of glycine. Sequentially add 1 g of EDC·HCl and 0.5 g of NHS to the glycine solution. Stir at room temperature to activate the carboxyl group of glycine for 60 min. Slowly add 40 g of the activated glycine solution dropwise to 40 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 50 °C for 12 h. After the reaction is completed, separate the product by centrifugation. Wash the product 3 times with a large amount of DMSO or DMF, and then wash several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 60 °C for 6 h.

[0060] Prepare a 2% 2,3-epoxypropyltrimethylammonium chloride solution with 1 g of 2,3-epoxypropyltrimethylammonium chloride and 49 g of acetonitrile, and prepare a solution containing an amide intermediate with 0.68 g of the amide intermediate and 33.32 g of acetonitrile. Add 30 g of the solution containing the amide intermediate to a three-necked flask, and slowly add 30 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 80 °C and react for 6 h, continuously stirring and passing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0061] Example 3 Prepare a 1.2% N-cyclohexyl-γ-aminopropyltrimethoxysilane solution with 1 g of N-cyclohexyl-γ-aminopropyltrimethoxysilane and 82.33 g of deionized water, and prepare a 1.2% SiO 2 nanoparticle solution with 1 g of SiO 2 nanoparticles and 82.33 g of deionized water, and ultrasonically disperse it for 30 min at room temperature. After the particles are evenly dispersed, add 50 g of γ-aminopropyltrimethoxysilane solution and 50 g of SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 7 with phosphate buffer solution. Transfer this solution to a three-necked flask, stir it in a 75 °C water bath for 9 h, separate the nanoparticles from the solvent by a centrifuge, and wash it 4 times repeatedly with deionized water. The obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) is placed in a vacuum drying oven at 110 °C and dried for 22 h and ground for standby.

[0062] Disperse 0.91 g of the above amino-functionalized nano-SiO 2 in 74.93 g of DMSO and ultrasonically treat it for 25 min. Prepare a glycine solution with 82.33 g of DMSO and 1 g of glycine. Add 1 g of EDC·HCl and 0.55 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 50 min. Slowly add 40 g of the activated glycine solution dropwise to 40 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 40 °C for 15 h. After the reaction is completed, separate the product by a centrifuge. Wash the product 5 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 50 °C for 7 h.

[0063] Prepare a 2,3-epoxypropyltrimethylammonium chloride solution with a mass concentration of 1.8% using 1 g of 2,3-epoxypropyltrimethylammonium chloride and 54.55 g of absolute ethanol. Prepare a solution containing an amide intermediate using 0.85 g of the amide intermediate and 46.37 g of absolute ethanol. Add 40 g of the solution containing the amide intermediate to a three-necked flask, and slowly add 40 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 70 °C and react for 9 h, continuously stirring and introducing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0064] Example 4 Prepare a γ-aminopropyltrimethoxysilane solution with a mass concentration of 1.4% using 1.5 g of γ-aminopropyltrimethoxysilane and 105.64 g of deionized water. Prepare a SiO 2 nanoparticle solution with a mass concentration of 1.4% using 1.5 g of SiO 2 nanoparticles and 105.64 g of deionized water, and ultrasonically disperse it for 32 min at room temperature. After the particles are evenly dispersed, add 50 g of the γ-aminopropyltrimethoxysilane solution and 50 g of the SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 8 with phosphate buffer. Transfer this solution to a three-necked flask, stir it in a 78 °C water bath for 10 h, separate the nanoparticles from the solvent with a centrifuge, and wash it 4 times repeatedly with deionized water. Place the obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) in a vacuum drying oven at 115 °C for 21 h and grind it for standby.

[0065] Disperse 0.844 g of the above amino-functionalized nano-SiO 2 in 59.44 g of DMSO and ultrasonically treat it for 22 min. Prepare a glycine solution using 70.43 g of DMSO and 1 g of glycine. Add 2 g of EDC·HCl and 1 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 40 min. Slowly add 50 g of the activated glycine solution dropwise to 50 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 45 °C for 16 h. After the reaction is completed, separate the product by a centrifuge. Wash the product 4 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 45 °C for 8 h.

[0066] Prepare a 1.7% 2,3-epoxypropyltrimethylammonium chloride solution with 1 g of 2,3-epoxypropyltrimethylammonium chloride and 57.82 g of acetonitrile solvent, and prepare an amide intermediate solution with 0.79 g of amide intermediate and 45.68 g of acetonitrile. Add 40 g of the amide intermediate solution to a three-necked flask, and slowly add 40 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 65 °C and react for 10 h, continuously stirring and passing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0067] Example 5 Prepare a 1.3% γ-ureidopropyltriethoxysilane solution with 1 g of γ-ureidopropyltriethoxysilane and 75.92 g of deionized water, and prepare a 1.3% SiO 2 nanoparticle solution with 1 g of SiO 2 nanoparticles and 75.92 g of deionized water, and ultrasonically disperse for 28 min at room temperature. After the particles are evenly dispersed, add 50 g of γ-aminopropyltrimethoxysilane solution and 50 g of SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 7 with phosphate buffer solution. Transfer this solution to a three-necked flask, stir at 74 °C in a water bath for 9 h, separate the nanoparticles from the solvent by a centrifuge, and wash repeatedly with deionized water 5 times. Place the obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) in a vacuum drying oven at 105 °C for 21 h and grind for standby.

[0068] Disperse 0.88 g of the above amino-functionalized nano-SiO 2 in 66.81 g of DMF and ultrasonically treat for 15 min. Prepare a glycine solution with 60.74 g of DMF and 0.8 g of glycine. Add 1.5 g of EDC·HCl and 0.9 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 55 min. Slowly add 50 g of the activated glycine solution dropwise to 50 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 35 °C for 17 h. After the reaction is completed, separate the product by a centrifuge. Wash the product 4 times with a large amount of DMSO or DMF, and then wash several times with absolute ethanol. Dry the washed amide intermediate product in a vacuum drying oven at 57 °C for 8 h.

[0069] Prepare a 2% 2,3-epoxypropyltrimethylammonium chloride solution with 1 g of 2,3-epoxypropyltrimethylammonium chloride and 49 g of absolute ethanol, and prepare an amide intermediate solution with 0.73 g of amide intermediate and 35.77 g of absolute ethanol. Add 30 g of the amide intermediate solution to a three-necked flask, and slowly add 30 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 72 °C and react for 10 h, continuously stirring and introducing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0070] Example 6 Prepare a 1.1% N-cyclohexyl-γ-aminopropyltrimethoxysilane solution with 0.8 g of N-cyclohexyl-γ-aminopropyltrimethoxysilane and 71.93 g of deionized water, and prepare a 1.1% SiO 2 nanoparticle solution with 1 g of SiO 2 nanoparticles and 89.91 g of deionized water, and ultrasonically disperse it at room temperature for 29 min. After the particles are evenly dispersed, add 50 g of γ-aminopropyltrimethoxysilane solution and 50 g of SiO 2 nanoparticle solution to the beaker, and adjust the pH of the solution to 8 with phosphate buffer. Transfer this solution to a three-necked flask, stir it in a 77 °C water bath for 9 h, separate the nanoparticles from the solvent with a centrifuge, and wash it 3 times repeatedly with deionized water. Place the obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) in a vacuum drying oven at 112 °C and dry it for 21 h, then grind it for standby.

[0071] Disperse 1.095 g of the above amino-functionalized nano-SiO 2 in 90.155 g of DMSO and ultrasonically treat it for 18 min. Prepare a glycine solution with 123.5 g of DMSO and 1.5 g of glycine. Add 2 g of EDC·HCl and 1.2 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 38 min. Slowly add 70 g of the activated glycine solution dropwise to 70 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 46 °C for 13 h. After the reaction is completed, separate the product by a centrifuge. Wash the product 4 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 54 °C for 7 h.

[0072] Prepare a 2,3-epoxypropyltrimethylammonium chloride solution with a mass concentration of 1.8% using 0.8 g of 2,3-epoxypropyltrimethylammonium chloride and 43.64 g of acetonitrile. Prepare a solution containing an amide intermediate using 0.82 g of the amide intermediate and 44.74 g of acetonitrile. Add 40 g of the solution containing the amide intermediate to a three-necked flask, and slowly add 40 g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 63 °C and react for 12 h, continuously stirring and introducing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with anti-swelling and oil-displacing effects.

[0073] Example 7 Prepare a 1% γ-aminopropyltrimethoxysilane solution using 1 g of γ-aminopropyltrimethoxysilane and 99 g of deionized water. Prepare a 1% SiO 2 nanoparticle solution using 1 g of SiO 2 nanoparticles and 99 g of deionized water, and ultrasonically disperse it at room temperature for 25 min. After the particles are evenly dispersed, add 50 g of the γ-aminopropyltrimethoxysilane solution and 50 g of the SiO 2 nanoparticle solution to a beaker, and adjust the pH of the solution to 7 with phosphate buffer. Transfer this solution to a three-necked flask, stir it in a 70 °C water bath for 10 h, separate the nanoparticles from the solvent by a centrifuge, and wash it 3 times repeatedly with deionized water. Place the obtained amino-functionalized nano-SiO 2 (H 2 N-SiO 2 ) in a vacuum drying oven at 100 °C for drying for 24 h and grind it for standby.

[0074] Disperse 1.1 g of the above amino-functionalized nano-SiO 2 in 108.9 g of DMF and ultrasonically treat it for 30 min. Prepare a glycine solution using 99 g of DMF and 1 g of glycine. Add 1 g of EDC·HCl and 0.6 g of NHS to the glycine solution in sequence. Stir at room temperature to activate the carboxyl group of glycine for 30 min. Slowly add 50 g of the activated glycine solution dropwise to 50 g of the amino-functionalized nano-SiO 2 suspension. Stir and react at 30 °C for 18 h. After the reaction is completed, separate the product by a centrifuge. Wash the product 5 times with a large amount of DMSO or DMF, and then wash it several times with absolute ethanol. Dry the washed product containing the amide intermediate in a vacuum drying oven at 40 °C for 8 h.

[0075] Prepare a 1.5% 2,3-epoxypropyltrimethylammonium chloride solution with 2g of 2,3-epoxypropyltrimethylammonium chloride and 131.33g of acetonitrile, and prepare a solution containing an amide intermediate with 1.36g of the amide intermediate and 89.31g of acetonitrile. Add 80g of the solution containing the amide intermediate to a three-necked flask, and slowly add 80g of the 2,3-epoxypropyltrimethylammonium chloride solution to the three-necked flask while continuously stirring. Heat the reaction system to 60°C and react for 12h, continuously stirring and introducing an inert gas for protection during this period. After the reaction is completed, stop heating and cool the reaction system to room temperature. Separate the unreacted solid impurities by a centrifuge. Collect the supernatant to obtain a nanofluid with swelling prevention and oil displacement effects.

[0076] Characterization and Testing To characterize the application performance of this nanofluid with swelling prevention and oil displacement effects, the following tests were carried out on it: Swelling Prevention Performance Test of a Nanofluid with Swelling Prevention and Oil Displacement Effects: Prepare solutions with different mass concentrations from the dried nanofluid powder, and use the centrifugation method to determine its swelling prevention rate. Examine the effect of nanofluid powder with different concentrations on the swelling prevention performance. The results are shown in Figure 5 .

[0077] It can be seen from Figure 5 that as the concentration of the nanofluid powder increases, its swelling prevention performance shows a trend of first increasing and then decreasing. When the mass concentration of the nanofluid powder solution is 0.4%, the swelling prevention rate is greater than 80%; when the mass concentration of the nanofluid powder solution is 0.8%, the swelling prevention rate reaches the maximum value of 91.67%, indicating that the nanofluid powder has a good effect on inhibiting clay swelling. Thus, the optimal use concentration of the nanofluid powder is determined to be 0.8%.

[0078] Simulation Oil Displacement Experiment: Take natural cores for indoor simulation oil displacement tests. Configure the mass concentrations of the oil displacement agent to be 0.2%, 0.4%, 0.6%, 0.8%, and 1%, and the injection volume to be 0.5PV. The results show that on the basis of the water flooding recovery rate, the crude oil recovery rate is increased by an average of 22.18% after adding the nanofluid. The test results are as shown in Figure 6 .

[0079] It can be seen from Figure 6 the results that the crude oil recovery rate is significantly increased after adding the nanofluid. As the concentration increases, the oil displacement efficiency shows an increasing trend. After exceeding 0.8%, the increase in the recovery rate slows down. From an economic perspective, when designing the parameters of the oil displacement agent, 0.8% is selected as the optimal concentration.

[0080] In summary, the present invention relates to a nanofluid with swelling prevention and oil displacement effects. This substance can achieve integration of swelling prevention and oil displacement. After reaching the response temperature, the amide bond breaks, releasing quaternary ammonium salt and amino-functionalized nano-SiO 2 , the quaternary ammonium salt serves as a swelling inhibitor, and the amino-functionalized nano-SiO 2 serves as an oil displacement agent. In this fluid, the quaternary ammonium salt adsorbs to clay minerals first, avoiding the adsorption loss of amino-functionalized nano-SiO 2 with clay, and improving the effective component of amino-functionalized nano-SiO 2 acting on oil displacement. The quaternary ammonium salt acts as both a sacrificial agent and a swelling inhibitor. The amino-functionalized nano-SiO 2 as an oil displacement agent has a large specific surface area and good dispersibility, can enter the tiny pores in the oil reservoir, can reduce the oil-water interfacial tension, and greatly improve the oil displacement efficiency. The amino-functionalized nano-SiO 2 has good chemical stability, is not easily affected by the formation environment, and can stably play the role of oil displacement. Moreover, with a large specific surface area, it enhances the contact area and action effect with crude oil, and can also maintain good performance in high-temperature and high-salinity oil reservoirs, with a wider application range. In addition, at the formation temperature of 80°C to 90°C, the amide bond breaks to release the quaternary ammonium salt. This temperature-responsive release method avoids the premature consumption of the quaternary ammonium salt before reaching the formation, can ensure slow and continuous release in a specific formation environment, and prolongs its effective action time.

[0081] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a nanofluid having anti-swelling and oil displacement effects, characterized in that: The following steps are involved: The aminated nano-SiO2 and glycine are subjected to a condensation reaction to generate an amide-containing intermediate; The amide-containing intermediate and 2,3-epoxypropyltrimethylammonium chloride are respectively mixed with solvent A to prepare an amide-containing intermediate solution and a 2,3-epoxypropyltrimethylammonium chloride solution, and then mixed and subjected to quaternization reaction to synthesize a nanofluid with anti-swelling and oil displacement effects.

2. The method for preparing the nanofluid having anti-swelling and oil displacement effects according to claim 1, characterized in that: The mass concentration of the amide intermediate solution is 1.5% to 2%; the mass concentration of the 2,3-epoxypropyltrimethylammonium chloride solution is 1.5% to 2%.

3. The method for preparing the nanofluid having anti-swelling and oil displacement effects according to claim 1, characterized in that: The molar ratio of the amide-containing intermediate in the amide-containing intermediate solution to the 2,3-epoxypropyltrimethylammonium chloride in the 2,3-epoxypropyltrimethylammonium chloride solution is 1:1-1.5:

1.

4. The method for preparing the nanofluid with anti-swelling and oil displacement effects according to claim 1, characterized in that: The temperature of the quaternization reaction is 60° C. to 80° C., and the time of the quaternization reaction is 6 h to 12 h; and the solvent A is anhydrous ethanol or acetonitrile.

5. The method for preparing the nanofluid with anti-swelling and oil displacement effects according to claim 1, characterized in that: The process of the amination nano-SiO2 and glycine undergoing condensation reaction to generate an amide-containing intermediate is as follows: Dispersing aminated nano-SiO2 and glycine in solvent B respectively to prepare aminated nano-SiO2 suspension and glycine solution respectively; A condensation agent is added to the glycine solution, and the carboxyl group of the glycine is activated by stirring. The activated glycine solution is added to the amino-treated nano-SiO2 suspension to carry out a condensation reaction, and then separation, washing and drying are carried out in sequence.

6. The method for preparing the nanofluid having anti-swelling and oil displacement effects according to claim 5, characterized in that: The solvent B is dimethyl sulfoxide or N,N-dimethylformamide; the condensing agent is a mixture of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and the molar ratio of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide is 1:1~1:1.

2.

7. The method for preparing the nanofluid with anti-swelling and oil displacement effects according to claim 5, characterized in that: The mass fraction of the glycine solution is 1% to 1.5%; the mass fraction of the amino-modified nano-SiO2 suspension is 1% to 1.5%; The molar ratio of the activated glycine in the activated glycine solution to the aminated nano-SiO2 in the aminated nano-SiO2 suspension is 1:1-1:1.

5.

8. The method for preparing the nanofluid with anti-swelling and oil displacement effects according to claim 1, characterized in that: The temperature of the condensation reaction is 30° C. to 50° C.; the time of the condensation reaction is 12 h to 18 h.

9. A nanofluid with anti-swelling and oil displacement effects obtained according to the method for preparing a nanofluid with anti-swelling and oil displacement effects according to any one of claims 1 to 8.

10. A nanofluid with anti-swelling and oil displacement effects prepared by the method for preparing the nanofluid with anti-swelling and oil displacement effects according to any one of claims 1 to 8, used as an anti-swelling agent and an oil displacement agent in the exploitation process of low permeability oil reservoirs, characterized in that: The amide bond of the nanofluid with anti-swelling and oil-displacing effects breaks after reaching the response temperature, releasing quaternary ammonium salt and amination nano-SiO2, wherein the quaternary ammonium salt serves as an anti-swelling agent and the amination nano-SiO2 serves as an oil-displacing agent.

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