Self-adaptive intelligent response type carbon quantum dot oil displacement agent and preparation method thereof

Abstract

The invention discloses a self-adaptive intelligent response type carbon quantum dot oil displacement agent and a preparation method thereof, and belongs to the technical field of petrochemical engineering. The preparation method comprises the following steps: dissolving glucose and urea in deionized water for carbonization reaction to obtain a product solution; carrying out first post-treatment on the product solution to prepare solid carbon quantum dot powder; adding N-isopropylacrylamide and a cross-linking agent N, N-methylene bisacrylamide into the carbon quantum dot solution, stirring and dissolving, and then adding an initiator ammonium persulfate to carry out free radical polymerization reaction to generate a modification layer; after the polymerization reaction is finished, carrying out secondary post-treatment to prepare functionalized carbon quantum dot powder; an emulsion is prepared from an aqueous solution of the functionalized carbon quantum dots and n-hexane, and the emulsion is subjected to ultrasonic treatment to prepare the self-adaptive intelligent response type carbon quantum dot oil-displacing agent. The oil-displacing agent prepared by the preparation method shows excellent self-adaptability under complex temperature change conditions, has good stability and is environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and particularly relates to an adaptive intelligent response type carbon quantum dot oil displacement agent and a preparation method thereof. Background Art

[0002] During the process of oilfield exploitation, traditional oil displacement technologies face many challenges, including low oil recovery rate, high cost, and environmental pollution. Traditional oil displacement agents usually rely on chemical surfactants. Although these surfactants can effectively reduce the interfacial tension between oil and water and promote the phase separation of oil and water, their performance is greatly affected by environmental factors such as temperature and salinity, resulting in poor stability in complex reservoir environments and often requiring a large amount of external energy for temperature control and adjustment. In addition, traditional oil displacement agents have poor adaptability under special reservoir conditions such as high temperature, low permeability, and heavy oil, resulting in low oil production efficiency and unable to meet the requirements of efficient development of modern oilfields.

[0003] Therefore, there is an urgent need for an intelligent response type oil displacement agent that has self - adaptability, good stability, and environmental friendliness under complex temperature change conditions. 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 an adaptive intelligent response type carbon quantum dot oil displacement agent and a preparation method thereof. The preparation method first prepares carbon quantum dots by a hydrothermal method using glucose and urea, then functionalizes the carbon quantum dots with poly(N - isopropylacrylamide), and finally prepares an adaptive intelligent response type carbon quantum dot oil displacement agent through emulsification. This oil displacement agent exhibits excellent self - adaptability under complex temperature change conditions, has good stability, and is environmentally friendly.

[0005] In order to achieve the above - mentioned purpose, the present invention adopts the following technical solutions: The present invention provides a preparation method of an adaptive intelligent response type carbon quantum dot oil displacement agent, comprising the following steps: Dissolve glucose and urea in deionized water to form a transparent solution. Carry out a carbonization reaction on the transparent solution, and after the carbonization reaction ends, cool to obtain a product solution. Perform a first post - treatment on the product solution to obtain a solid carbon quantum dot powder; Disperse the solid carbon quantum dot powder in deionized water to obtain a carbon quantum dot solution. Add N - isopropylacrylamide and N,N - methylenebisacrylamide to the carbon quantum dot solution, stir to dissolve, then add ammonium persulfate, and then heat to carry out a free - radical polymerization reaction to generate a modified layer. After the free - radical polymerization reaction ends, cool, and then perform a second post - treatment to obtain a functionalized carbon quantum dot powder. In this step, N - isopropylacrylamide undergoes self - polymerization under the action of a cross - linking agent (N,N - methylenebisacrylamide) and an initiator (ammonium persulfate); Dissolve the functionalized carbon quantum dot powder in deionized water to obtain an emulsifier solution; mix the emulsifier solution and n-hexane and then emulsify to prepare an emulsion, and ultrasonically treat the emulsion to prepare an adaptive intelligent response type carbon quantum dot oil displacement agent.

[0006] In one embodiment, the mass ratio of urea to glucose is 1:(2 - 2.4).

[0007] In one embodiment, the addition amount of deionized water in the transparent solution is 15 - 20 times the total mass of urea and glucose.

[0008] In one embodiment, the reaction temperature of the carbonization reaction is 160 - 180 °C, and the reaction time of the carbonization reaction is 8 - 10 h; The temperature for adding ammonium persulfate is 40 °C; The reaction temperature of the free radical polymerization is 60 - 70 °C, and the reaction time of the free radical polymerization is 4 - 6 h.

[0009] In one embodiment, the process of the first post-treatment is as follows: Filter to remove large particles with a microporous membrane with a particle size of 0.22 μm, use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities, and freeze-dry to obtain solid carbon quantum dot powder; The process of the second post-treatment is as follows: Use a dialysis bag with a cut-off molecular weight of 3000 Da to dialyze for 2 days to remove unpolymerized monomers, and freeze-dry to obtain functionalized carbon quantum dot powder.

[0010] In one embodiment, the mass ratio of the solid carbon quantum dot powder to deionized water in the carbon quantum dot solution is 1:(100 - 200).

[0011] In one embodiment, the addition amount of N-isopropylacrylamide is 20 - 30 times the mass of the solid carbon quantum dot powder, the addition amount of the cross-linking agent N,N'-methylenebisacrylamide is 0.5 - 0.8% of the mass of N-isopropylacrylamide, and the addition amount of the initiator ammonium persulfate is 1 - 1.2% of the mass of N-isopropylacrylamide.

[0012] In one embodiment, the mass ratio of the functionalized carbon quantum dot powder to deionized water in the emulsifier solution is 1:(100 - 120).

[0013] In one embodiment, the mass ratio of the emulsifier solution to n-hexane is 1:(0.6 - 0.8).

[0014] The present invention also provides an adaptive intelligent response type carbon quantum dot oil displacement agent prepared by the preparation method of the above-mentioned adaptive intelligent response type carbon quantum dot oil displacement agent.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a preparation method of an adaptive intelligent response type carbon quantum dot oil displacement agent. In this method, carbon quantum dot powder is first prepared by a hydrothermal method using glucose and urea, and then the carbon quantum dot powder is functionalized with poly N-isopropylacrylamide. Finally, the adaptive intelligent response type carbon quantum dot oil displacement agent is prepared by emulsification. The present invention combines the functionalized carbon quantum dots with the oil phase and the water phase through an emulsification technique to form a stable emulsion. In this process, the functionalized carbon quantum dots act as surfactants, which can effectively reduce the interfacial tension between the oil and water phases, enhance the affinity between the oil and water phases, enable the oil phase to form fine oil droplets in water, and improve the oil recovery rate during oilfield exploitation.

[0016] Furthermore, the raw materials glucose and urea used in the present invention are natural and non-toxic raw materials, which are widely sourced and inexpensive. The hydrothermal method is a green synthesis method. The reaction is carried out in a closed high-pressure reactor without the use of toxic organic solvents, and the above preparation method is relatively environmentally friendly.

[0017] The advantage of the adaptive intelligent response type carbon quantum dot oil displacement agent prepared by the present invention is that the carbon quantum dot oil displacement agent has self-adaptability to the reservoir environment temperature through surface functionalization. Specifically, at a lower temperature, the hydrogen bond interaction between the amide groups in the poly N-isopropylacrylamide molecules and water molecules is stronger, making it maintain good water solubility and the molecular chain in a swollen state, which helps the expansion of the water phase and the pushing of oil. When the temperature is higher, the hydrogen bond interaction weakens, while the hydrophobic interaction between the hydrophobic groups (isopropyl groups) in the poly N-isopropylacrylamide molecules strengthens, resulting in the contraction of the molecular chain, and the molecules begin to aggregate and are more inclined to interact with the oil phase, enhancing their dispersibility and emulsifying ability in the oil phase. Moreover, the nanoscale of the carbon quantum dots enables them to improve the oil-water phase behavior at the microscale, not only enhancing the stability of the oil-water interface, but also further promoting the stability and emulsification of the oil phase through their unique nano-effects (such as large specific surface area, good dispersibility, and enhanced interfacial activity), thereby improving the oil recovery rate and having good application prospects. Description of the Drawings

[0018] Figure 1 It is the particle size distribution diagram of the carbon quantum dot oil displacement agent prepared in Example 3; Figure 2 It is the contact angle of the carbon quantum dot oil displacement agent prepared in Example 3 at different temperatures; Figure 3 It is the interfacial tension of the carbon quantum dot oil displacement agent prepared in Example 3. Detailed implementation manners

[0019] 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 phrases 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 with respect to the present invention. In case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] In this document, 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).

[0022] In this document, unless otherwise specified, the terms "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".

[0023] In this document, 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 as being within the scope described in this specification.

[0024] In recent years, temperature-responsive oil displacement agents, as a new type of intelligent oil displacement technology, have gradually become a research hotspot. Such oil displacement agents can automatically adjust their surface activity, hydrophilicity, and lipophilicity according to temperature changes, thereby optimizing the oil-water phase behavior and improving the oil recovery rate of oilfields. As a nanomaterial with excellent optical, electrical, and thermal properties, carbon quantum dots have become an ideal candidate material for temperature-responsive oil displacement agents due to their low toxicity, high thermal stability, and adjustable surface properties. Through surface modification and functionalization, carbon quantum dots can achieve intelligent response, that is, automatically adjust their properties when the temperature changes, thereby improving the oil displacement effect and adapting to the complex oilfield exploitation environment. Therefore, the development of carbon quantum dot-based self-adaptive intelligent response oil displacement agents can not only improve the oil recovery rate but also reduce energy consumption and environmental pollution, and has important industrial application prospects.

[0025] Based on the above concept, the present invention discloses an adaptive intelligent response type carbon quantum dot oil displacement agent and a preparation method thereof. Specifically, the preparation steps are as follows: S1: Dissolve a certain amount of glucose and urea in deionized water to form a uniform and transparent solution. Transfer the transparent solution to a high-pressure reaction kettle with a polytetrafluoroethylene liner and react at 160 - 180 °C for 8 - 10 h. After the carbonization reaction is completed, naturally cool the reaction kettle to room temperature to obtain a product solution. Filter out large particles using a microporous filter membrane, and use a dialysis bag to dialyze for 3 days to remove unreacted small molecule impurities, and then freeze-dry to obtain solid carbon quantum dot powder.

[0026] Among them, the mass ratio of urea to glucose is 1:(2 - 2.4), the addition amount of deionized water is 15 - 20 times the total mass of urea and glucose, the particle size of the microporous filter membrane is 0.22 μm, and the cut-off molecular weight of the dialysis bag is 1000 Da.

[0027] S2: Take a certain amount of the solid carbon quantum dot powder prepared in S1, ultrasonically disperse it in deionized water, and place it in a three-necked flask equipped with a stirring device. Add a certain amount of N-isopropylacrylamide and the cross-linking agent N,N'-methylenebisacrylamide, and stir to dissolve. Under stirring in a 40 °C water bath, add a certain amount of the initiator ammonium persulfate, and continue stirring for 10 min. Then quickly heat to 60 - 70 °C for free radical polymerization reaction for 4 - 6 h to polymerize and form a modified layer. After the reaction is completed, cool to room temperature, use a dialysis bag to dialyze for 2 days to remove unpolymerized monomers, and then freeze-dry to obtain functionalized carbon quantum dot powder.

[0028] Among them, the mass ratio of the solid carbon quantum dot powder to deionized water is 1:(100 - 200), the addition amount of N-isopropylacrylamide is 20 - 30 times the mass of the solid carbon quantum dot powder, the addition amount of N,N'-methylenebisacrylamide is 0.5 - 0.8% of the mass of N-isopropylacrylamide, the addition amount of ammonium persulfate is 1 - 1.2% of the mass of N-isopropylacrylamide, and the cut-off molecular weight of the dialysis bag is 3000 Da.

[0029] S3: Take a certain amount of the functionalized carbon quantum dot powder prepared in S2 and dissolve it in deionized water to obtain an emulsifier solution. Mix the emulsifier solution and n-hexane in a certain proportion, and use a high-speed centrifuge for emulsification to obtain an emulsion. Ultrasonicate the emulsion for 30 - 40 min to obtain the adaptive intelligent response type carbon quantum dot oil displacement agent.

[0030] Among them, the mass ratio of the functionalized carbon quantum dot powder to deionized water is 1:(100 - 120), and the mass ratio of the emulsifier solution to n-hexane is 1:(0.6 - 0.8).

[0031] On the other hand, the present invention provides an adaptive intelligent response type carbon quantum dot oil displacement agent prepared by the above preparation method. With the change of the oilfield temperature, the temperature-responsive carbon quantum dot oil displacement agent can automatically adjust its hydrophilicity and lipophilicity according to the temperature change.

[0032] The following specific examples are used to further illustrate the present invention. It should be understood that these examples 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.

[0033] In the following examples, conventional instrument equipment in the art is used. For the experimental methods without specific conditions noted in the following examples, they are usually 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 stated, commercially available products are used, and their specifications are 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.

[0034] Example 1 This example provides a preparation method of an adaptive intelligent response type carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4 g of glucose and 2 g of urea in 90 g of deionized water to form a uniform and transparent solution. Transfer the solution to a high-pressure reaction kettle with a polytetrafluoroethylene lining and react at 160 °C for 8 h. After the reaction is completed, let the reaction kettle cool naturally to room temperature to obtain a product solution. Filter out large particles using a 0.22 μm microporous filter membrane, and use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities, and then freeze-dry to obtain solid carbon quantum dot powder.

[0035] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 50 g of deionized water, and place them in a three-necked flask with a stirring device. Add 10 g of N-isopropylacrylamide and 50 mg of N,N-methylenebisacrylamide to it and stir to dissolve. Under stirring in a 40 °C water bath, add 0.1 g of ammonium persulfate and continue stirring for 10 min. Then quickly heat to 60 °C and react for 6 h to polymerize and form a modified layer. After the reaction is completed, cool to room temperature, use a dialysis bag with a cut-off molecular weight of 3000 Da to dialyze for 2 days to remove unpolymerized monomers, and then freeze-dry to obtain functionalized carbon quantum dot powder.

[0036] S3: Dissolve 1 g of the functionalized carbon quantum dot powder prepared in S2 in 100 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 30 g of n-hexane and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonic the emulsion for 30 min to obtain the self-adaptive intelligent responsive carbon quantum dot oil displacement agent.

[0037] Example 2 This example provides a preparation method of a self-adaptive intelligent responsive carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4.8 g of glucose and 2 g of urea in 136 g of deionized water to form a uniform and transparent solution. Transfer the solution to a high-pressure reaction kettle with a polytetrafluoroethylene liner and react at 180 °C for 10 h. After the reaction, naturally cool the reaction kettle to room temperature to obtain a product solution. Filter to remove large particles with a 0.22 μm microporous filter membrane, and use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities, and then freeze-dry to obtain solid carbon quantum dot powder.

[0038] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 100 g of deionized water, and place them in a three-necked flask with a stirring device. Add 15 g of N-isopropylacrylamide and 120 mg of N,N-methylenebisacrylamide thereto and stir to dissolve. Under stirring in a 40 °C water bath, add 0.18 g of ammonium persulfate and continue stirring for 10 min. Then quickly heat to 70 °C and react for 4 h to polymerize to form a modified layer. After the reaction is completed, cool to room temperature, use a dialysis bag with a cut-off molecular weight of 3000 Da to dialyze for 2 days to remove unpolymerized monomers, and then freeze-dry to obtain functionalized carbon quantum dot powder.

[0039] S3: Dissolve 1 g of the functionalized carbon quantum dot powder prepared in S2 in 120 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 40 g of n-hexane and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonic the emulsion for 40 min to obtain the self-adaptive intelligent responsive carbon quantum dot oil displacement agent.

[0040] Example 3 This example provides a preparation method of a self-adaptive intelligent responsive carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4.5 g of glucose and 2 g of urea in 100 g of deionized water to form a homogeneous and transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 160 °C for 10 h. After the reaction is completed, let the reactor cool naturally to room temperature to obtain a product solution. Filter out large particles using a 0.22 μm microporous membrane, and use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities. Freeze-dry to obtain solid carbon quantum dot powder.

[0041] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 80 g of deionized water, and place them in a three-necked flask equipped with a stirring device. Add 12 g of N-isopropylacrylamide and 80 mg of N,N-methylenebisacrylamide to it and stir to dissolve. Under stirring in a 40 °C water bath, add 0.13 g of ammonium persulfate and continue stirring for 10 min. Then quickly heat to 60 °C and react for 6 h to polymerize and form a modified layer. After the reaction is completed, cool to room temperature, use a dialysis bag with a cut-off molecular weight of 3000 Da to dialyze for 2 days to remove unpolymerized monomers, and freeze-dry to obtain functionalized carbon quantum dot powder.

[0042] S3: Take 1 g of the functionalized carbon quantum dot powder prepared in S2 and dissolve it in 110 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 35 g of n-hexane and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonicate the emulsion for 40 min to obtain the self-adaptive intelligent response type carbon quantum dot oil displacement agent.

[0043] Example 4 This example provides a preparation method of a self-adaptive intelligent response type carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4.2 g of glucose and 2 g of urea in 110 g of deionized water to form a homogeneous and transparent solution. Transfer the solution to a high-pressure reactor with a polytetrafluoroethylene liner and react at 180 °C for 8 h. After the reaction is completed, let the reactor cool naturally to room temperature to obtain a product solution. Filter out large particles using a 0.22 μm microporous membrane, and use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities. Freeze-dry to obtain solid carbon quantum dot powder.

[0044] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 60 g of deionized water, and place them in a three-necked flask equipped with a stirring device. Add 12 g of N-isopropylacrylamide and 70 mg of N,N-methylenebisacrylamide thereto, and stir to dissolve. Under stirring in a 40 °C water bath, add 0.14 g of ammonium persulfate, and continue stirring for 10 min. Then quickly heat to 70 °C and react for 6 h to polymerize and form a modified layer. After the reaction is completed, cool to room temperature, dialyze for 2 days using a dialysis bag with a cut-off molecular weight of 3000 Da to remove unpolymerized monomers, and freeze-dry to obtain functionalized carbon quantum dot powder.

[0045] S3: Take 1 g of the functionalized carbon quantum dot powder prepared in S2 and dissolve it in 100 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 40 g of n-hexane, and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonicate the emulsion for 40 min to obtain the self-adaptive intelligent response type carbon quantum dot oil displacement agent.

[0046] Example 5 This example provides a preparation method of a self-adaptive intelligent response type carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4.3 g of glucose and 2 g of urea in 100 g of deionized water to form a uniform and transparent solution. Transfer the solution to a high-pressure reaction kettle with a polytetrafluoroethylene liner and react at 160 °C for 9 h. After the reaction is completed, naturally cool the reaction kettle to room temperature to obtain a product solution. Filter to remove large particles using a 0.22 μm microporous filter membrane, and dialyze for 3 days using a dialysis bag with a cut-off molecular weight of 1000 Da to remove unreacted small molecule impurities, and freeze-dry to obtain solid carbon quantum dot powder.

[0047] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 70 g of deionized water, and place them in a three-necked flask equipped with a stirring device. Add 14 g of N-isopropylacrylamide and 90 mg of N,N-methylenebisacrylamide thereto, and stir to dissolve. Under stirring in a 40 °C water bath, add 0.15 g of ammonium persulfate, and continue stirring for 10 min. Then quickly heat to 60 °C and react for 6 h to polymerize and form a modified layer. After the reaction is completed, cool to room temperature, dialyze for 2 days using a dialysis bag with a cut-off molecular weight of 3000 Da to remove unpolymerized monomers, and freeze-dry to obtain functionalized carbon quantum dot powder.

[0048] S3: Dissolve 1 g of the functionalized carbon quantum dot powder prepared in S2 in 120 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 30 g of n-hexane and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonic the emulsion for 30 min to obtain the self-adaptive intelligent response type carbon quantum dot oil displacement agent.

[0049] Example 6 This example provides a preparation method of a self-adaptive intelligent response type carbon quantum dot oil displacement agent. The specific steps are as follows: S1: Dissolve 4.5 g of glucose and 2 g of urea in 100 g of deionized water to form a uniform and transparent solution. Transfer the solution to a high-pressure reaction kettle with a polytetrafluoroethylene lining and react at 160 °C for 10 h. After the reaction is completed, naturally cool the reaction kettle to room temperature to obtain a product solution. Filter to remove large particles using a 0.22 μm microporous filter membrane, and use a dialysis bag with a cut-off molecular weight of 1000 Da to dialyze for 3 days to remove unreacted small molecule impurities, and then freeze-dry to obtain a solid carbon quantum dot powder.

[0050] S2: Take 0.5 g of the carbon quantum dots prepared in S1, ultrasonically disperse them in 90 g of deionized water, and place them in a three-necked flask with a stirring device. Add 14 g of N-isopropylacrylamide and 90 mg of N,N-methylenebisacrylamide thereto and stir to dissolve. Under stirring in a 40 °C water bath, add 0.16 g of ammonium persulfate and continue to stir for 10 min. Then quickly heat to 60 °C and react for 6 h to polymerize to form a modified layer. After the reaction is completed, cool to room temperature, and use a dialysis bag with a cut-off molecular weight of 3000 Da to dialyze for 2 days to remove unpolymerized monomers, and then freeze-dry to obtain a functionalized carbon quantum dot powder.

[0051] S3: Dissolve 1 g of the functionalized carbon quantum dot powder prepared in S2 in 110 g of deionized water to obtain an emulsifier solution. Mix 50 g of the solution with 40 g of n-hexane and use a high-speed centrifuge to emulsify to obtain an emulsion. Ultrasonic the emulsion for 40 min to obtain the self-adaptive intelligent response type carbon quantum dot oil displacement agent.

[0052] Performance Characterization To evaluate the relevant performance of the self-adaptive intelligent response type carbon quantum dot oil displacement agent, use a nanoparticle size and zeta potential analyzer to analyze the particle size of the carbon quantum dot oil displacement agent prepared in Example 3. The results are as Figure 1 shown. From Figure 1It can be seen that the particle size of the carbon quantum dot oil displacement agent prepared by the present invention is within 1-10 nm, which is an important characteristic of the carbon quantum dot material, indicating the successful preparation of carbon quantum dots. The contact angle of the carbon quantum dot oil displacement agent prepared in Example 3 with an oil-wetted glass plate at different temperatures was measured. The specific measurement method refers to the "Technical Specification for Oil Displacement Agents for Oilfield Fracturing Q / SY 8023-2023". The results are as Figure 2 shown. From Figure 2 it can be seen that when the temperature is low, the oil displacement agent of the present invention exhibits obvious hydrophilicity. When the temperature rises, the oil displacement agent molecules gradually become lipophilic, which helps to improve the distribution and flow of oil. The interfacial tension of the carbon quantum dot oil displacement agent prepared in Example 3 at 60 °C was measured. The results are as Figure 3 shown. From Figure 3 it can be seen that as time goes by, the oil-water interfacial tension of the carbon quantum dot oil displacement agent gradually decreases, indicating that it can effectively improve the oil recovery rate, especially in low-permeability and complex reservoir environments.

[0053] In summary, the present invention provides a preparation method for an adaptive intelligent response type carbon quantum dot oil displacement agent as follows: Dissolve glucose and urea in deionized water for carbonization reaction to obtain a product solution; perform a first post-treatment on the product solution to obtain solid carbon quantum dot powder; add N-isopropylacrylamide and cross-linking agent N,N'-methylenebisacrylamide to the carbon quantum dot solution, stir and dissolve, and then add initiator ammonium persulfate for free radical polymerization reaction to form a modified layer; perform a second post-treatment after the polymerization reaction to obtain functionalized carbon quantum dot powder; use the aqueous solution of the functionalized carbon quantum dot and n-hexane to prepare an emulsion, and perform ultrasonic treatment on the emulsion to obtain an adaptive intelligent response type carbon quantum dot oil displacement agent. The adaptive intelligent response type carbon quantum dot oil displacement agent prepared by the above method can automatically adjust its hydrophilicity and lipophilicity according to temperature changes as the temperature of the oilfield changes. Moreover, the nano-scale of the carbon quantum dots not only enhances the stability of the oil-water interface, but also further promotes the stability and emulsification of the oil phase through its unique nano-effect, thereby improving the oil recovery rate and having good application prospects.

[0054] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. 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 an adaptive intelligent response carbon quantum dot oil displacement agent, characterized in that: The following steps are involved: dissolving glucose and urea in deionized water to form a transparent solution, and subjecting the transparent solution to a carbonization reaction to obtain a product solution; The product solution is subjected to a first post-treatment to obtain solid carbon quantum dot powder; Dispersing solid carbon quantum dot powder in deionized water to obtain a carbon quantum dot solution; adding N-isopropylacrylamide and a crosslinking agent to the carbon quantum dot solution, stirring and dissolving, and then adding an initiator to perform a free radical polymerization reaction to polymerize and generate a modified layer; and then performing a second post-treatment to obtain a functionalized carbon quantum dot powder; The functionalized carbon quantum dot powder is dissolved in deionized water to obtain an emulsifier solution; the emulsifier solution and n-hexane are mixed and emulsified to obtain an emulsion; the emulsion is ultrasonicated to obtain an adaptive intelligent response carbon quantum dot oil displacement agent.

2. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The mass ratio of urea to glucose is 1:(2-2.4).

3. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The amount of deionized water added to the transparent solution is 15 to 20 times the total mass of urea and glucose.

4. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The reaction temperature of the carbonization reaction is 160-180°C, and the reaction time of the carbonization reaction is 8-10 h; The temperature for adding the initiator is 40°C; the crosslinking agent is N,N-methylenebisacrylamide; the initiator is ammonium persulfate; The reaction temperature of the free radical polymerization is 60-70° C., and the reaction time of the free radical polymerization is 4-6 h.

5. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The process of the first post-processing is as follows: Large particles were removed by filtering with a microporous membrane with a particle size of 0.22 μm, and unreacted small molecule impurities were removed by dialyzing with a dialysis bag with a molecular weight cutoff of 1000 Da for 3 days, and solid carbon quantum dot powder was obtained by freeze drying; The process of the second post-processing is as follows: The unpolymerized monomers were removed by dialysis for 2 days using a dialysis bag with a molecular weight cutoff of 3000 Da, and the functionalized carbon quantum dot powder was obtained by freeze drying.

6. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The mass ratio of the solid carbon quantum dot powder to deionized water in the carbon quantum dot solution is 1:(100-200).

7. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The added amount of N-isopropylacrylamide is 20 to 30 times the mass of the solid carbon quantum dot powder, the added amount of the crosslinking agent is 0.5 to 0.8% of the mass of N-isopropylacrylamide, and the added amount of the initiator is 1 to 1.2% of the mass of N-isopropylacrylamide.

8. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The mass ratio of the functionalized carbon quantum dot powder to deionized water in the emulsifier solution is 1:(100-120).

9. The method for preparing the adaptive intelligent response type carbon quantum dot oil displacement agent according to claim 1, characterized in that: The mass ratio of the emulsifier solution to n-hexane is 1:(0.6-0.8).

10. An adaptive intelligent response type carbon quantum dot oil-displacing agent prepared according to the preparation method of the adaptive intelligent response type carbon quantum dot oil-displacing agent according to any one of claims 1 to 9.

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