Amphiphilic carbon dot reinforced thickening water flooding system suitable for high-salt oil reservoir and preparation method

Abstract

The invention discloses an amphiphilic carbon dot reinforced thickening water flooding system suitable for a high-salt oil reservoir and a preparation method. The amphiphilic carbon dot reinforced thickening water flooding system comprises liquid preparation water and a composite aggregate formed by CDs and an ampholytic surfactant, cDs are adsorbed on a linear micelle formed by the surfactant and are gathered at a plurality of micelle entanglement points; the particle size of the CDs is smaller than or equal to 1 nm, the surfaces of the CDs contain hydrophilic groups and hydrophobic groups at the same time, the hydrophilic groups are-CO-NH2 and-OH, and the hydrophobic groups are-N (CH3) 2 and-COOCH3; the CDs provided by the invention and the ampholytic surfactant have a synergistic effect and are mutually entangled to construct a stable three-dimensional space network structure, so that the ampholytic surfactant has excellent tackifying and salt-resistant performance, can still keep relatively high interfacial activity under hypersalinity, can improve the viscosity of the surfactant in hypersalinity water, and can remarkably improve the stability and the salt resistance.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry, and in particular to an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs and its preparation method. Background Technology

[0002] In the field of oil extraction, the efficient development of high-salinity reservoirs has always been a highly challenging issue. As extraction progresses, conventional oil resources are gradually decreasing, while high-salinity reservoirs are attracting increasing attention due to their abundant reserves. However, the high-salinity environment places stringent demands on the performance of oil displacement systems, making the improvement of oil displacement efficiency under high-salinity conditions a key research focus.

[0003] Micellar thickening, as an important oil displacement technique, plays a crucial role in improving the oil-water mobility ratio and sweep efficiency. Currently, common micellar thickening methods mainly rely on traditional surfactants forming micelle structures in aqueous solutions. However, traditional micellar thickening systems face numerous challenges in high-salinity reservoirs. High salinity significantly affects the solubility and micelle-forming ability of surfactants. The presence of salt ions compresses the electric double layer around surfactant molecules, reducing the electrostatic repulsion between surfactant molecules and making micelles prone to aggregation and precipitation, thus reducing the system's stability and thickening effect. Furthermore, conventional surfactants may interact with salt ions under high-salinity conditions, altering their surface activity and micelle structure, further weakening the performance of the micellar thickening system. Although compounding with carbon dots can improve interfacial activity, it cannot solve the problems of easy cross-flow of water-driven fluids and limited sweep range in high-salinity reservoirs, resulting in poor system stability and salt tolerance.

[0004] Therefore, there is a need to provide a technical solution to improve the stability and salt tolerance of water drive systems in high-salt reservoir environments. Summary of the Invention

[0005] In view of this, this application provides an amphiphilic carbon dot-enhanced thickening waterflooding system and its preparation method suitable for high-salt reservoirs, in order to solve the problem of how to improve the stability and salt tolerance of the waterflooding system in high-salt reservoir environments.

[0006] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, this application provides an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs, comprising a solution of water and a composite aggregate formed by CDs and an amphoteric surfactant; the CDs are adsorbed on linear micelles formed by the surfactant and aggregate at multiple micelle entanglement points; the particle size of the CDs is ≤1 nm, and the surface of the CDs simultaneously contains hydrophilic and hydrophobic groups, wherein the hydrophilic groups are -CO-NH2 and -OH, and the hydrophobic groups are -N(CH3)2 and -COOCH3.

[0007] Preferably, the amphoteric surfactant is a betaine-type surfactant and / or an imidazoline-type surfactant.

[0008] Preferably, the water used for preparing the solution is highly mineralized water with a total mineralization of 200,000-210,000 mg / L.

[0009] Preferably, based on 100 mL of water for preparing the solution, it contains 0.5-5.5 g of amphoteric surfactant and 0.1-1.2 g of CDs.

[0010] Preferably, the preparation method of CDs is as follows: S1. Mix acrylamide, N,N-dimethylacrylamide, methyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate to form a homogeneous reaction solution; S2. Under closed conditions, the homogeneous reaction liquid is subjected to hydrothermal treatment to obtain CDs.

[0011] Preferably, in step S1, acrylamide, N,N-dimethylacrylamide, and methyl methacrylate are dispersed in water to obtain a mixture; N,N'-methylenebisacrylamide and ammonium persulfate are added sequentially to the mixture to form a homogeneous reaction solution.

[0012] Preferably, in step S2, the hydrothermal treatment temperature is 190-200℃ and the time is 7-10h.

[0013] Preferably, the mass ratio of acrylamide, N,N-dimethylacrylamide, methyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate is 14-16:8-10:5-7:2:1.

[0014] Secondly, this application provides a method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs, comprising the following steps: At room temperature, CDs were dispersed in the solution water to obtain a CDs solution; Adding an amphoteric surfactant to a CDs solution and stirring until homogeneous yields an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salt reservoirs.

[0015] Thirdly, this application provides an application of an amphiphilic carbon point-enhanced thickening waterflooding system suitable for high-salinity reservoirs in mining high-salinity reservoirs with an oil content of 200,000-250,000 mg / L.

[0016] The beneficial effects of this application are as follows: The CDs proposed in this invention work synergistically with amphoteric surfactants to form a stable three-dimensional network structure, exhibiting excellent thickening and salt resistance properties. They can maintain high interfacial activity even under high salinity conditions, improve the viscosity of surfactants in high-salt water, and significantly enhance stability and salt resistance.

[0017] The amphiphilic carbonized polymer point-enhanced thickening waterflooding system proposed in this invention, suitable for high-salt reservoirs, has good viscosity-enhancing and salt-resistant properties. It exhibits good viscosity-enhancing properties under high-salt conditions (210,000 mg / L), with a viscosity-enhancing effect of up to 2 times. After aging for 15 and 30 days, the apparent viscosity is still higher than that of the system without added CDs.

[0018] The present invention provides an amphiphilic carbonized polymer point-enhanced thickening waterflooding system suitable for high-salinity reservoirs. It is low in cost, simple to prepare, easy to disperse (not dependent on ultrasonic dispersion), and convenient for large-scale field construction. Attached Figure Description

[0019] Figure 1 The apparent viscosity of 2g OAB with different concentrations of different types of nanoparticles (CDs, SiO2, TiO2); Figure 2 Schematic diagram of CDs material; Figure 3 Particle size distribution diagram; Figure 4 Cryo-transmission electron microscopy image of OAB / CDs. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] This application provides an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs, comprising a solution of water and a composite aggregate formed by CDs and an amphoteric surfactant. Compared with conventional amphiphilic carbon dots that use -COOH, -OH, or ether groups as hydrophilic groups and "alkyl chains / alkylbenzene rings" as hydrophobic groups, the CDs of this invention use -CO-NH2 as the core hydrophilic group. Its strong hydrogen bonding activity forms stable hydrogen bonds when combined with the amphoteric surfactant, which is the key to achieving excellent thickening under high salt conditions. At the same time, -N(CH3)2 and -COOCH3 are hydrophobic groups. The charged hydrophobic groups can form weak electrostatic interactions with the anionic ends of the amphoteric surfactant, further enhancing the "carbon dot-surfactant" combination. The CDs are adsorbed on linear micelles formed by the surfactant and aggregate at multiple micelle entanglement points. The particle size of the CDs is ≤1nm. The surface of the CDs contains both hydrophilic and hydrophobic groups, wherein the hydrophilic groups are -CO-NH2 and -OH, and the hydrophobic groups are -N(CH3)2 and -COOCH3.

[0022] The amphoteric surfactant molecules of the present invention can reduce the damage to the molecular conformation by salt ions through the charge shielding effect of their hydrophilic groups in a high-salt environment, thereby reducing the oil-water interfacial tension and improving the oil washing efficiency.

[0023] The CDs of this invention simultaneously possess hydrophilic groups (-CO-NH2, -OH) and hydrophobic groups (-N(CH3)2, -COOCH3) on their surface. The hydrophilic groups can form hydrogen bonds with water molecules in high-salt water, while the hydrophobic groups combine with the hydrophobic segments of amphoteric surfactants through hydrophobic association, forming "CDs-surfactant" composite aggregates. These composite aggregates further entangle with each other, constructing a stable three-dimensional network structure, significantly increasing the viscosity of the displacing solution. Furthermore, the network structure is less affected by salt ions, maintaining stable viscosity even under high salt conditions.

[0024] In some embodiments, the amphoteric surfactant is a betaine-type surfactant and / or an imidazoline-type surfactant.

[0025] Specifically, the betaine surfactant is selected from one or more of the following betaine surfactants: cocamidopropyl betaine (CAB-35), cocamidopropyl hydroxysulfonate betaine (CHSB), lauramide propyl betaine (LAB-35), lauramide propyl hydroxysulfonate betaine (LHSB), oleamide propyl betaine (OAB), oleamide propyl hydroxysulfonate betaine (OHSB), erucamide propyl betaine (EAB), and erucamide propyl hydroxysulfonate betaine (EHSB); the imidazoline surfactant is selected from one or more of the following imidazoline surfactants: lauryl amphoteric imidazoline (LAD), cocoamyl amphoteric imidazoline (CAD), sodium lauroyl amphoteric acetate (LAMC), and sodium cocoamyl amphoteric acetate (CAMC).

[0026] In some embodiments, the water used for preparing the solution is highly mineralized water with a total mineralization of 200,000-210,000 mg / L.

[0027] In some embodiments, based on 100 mL of water for preparation, the solution contains 0.5-5.5 g of amphoteric surfactant and 0.1-1.2 g of CDs.

[0028] In some embodiments, based on 100 mL of water for preparation, the solution contains 1.6-2.4 g of amphoteric surfactant and 0.15-0.45 g of CDs.

[0029] In some embodiments, the CDs are prepared as follows: S1. Mix monomer acrylamide, N,N-dimethylacrylamide, methyl methacrylate, crosslinking agent N,N'-methylenebisacrylamide, and initiator ammonium persulfate to form a homogeneous reaction solution; S2. Under closed conditions, the homogeneous reaction liquid is subjected to hydrothermal treatment to obtain CDs.

[0030] The amphiphilic carbonized polymer dots (CDs) with hydrophobic cores and hydrophilic surface structures prepared by hydrothermal method in this application have a particle size distribution of <1nm, which is much smaller than conventional nanoparticles and ordinary carbon dots, and has a stronger nano-effect.

[0031] In some embodiments, in step S1, acrylamide, N,N-dimethylacrylamide, and methyl methacrylate are dispersed in water to obtain a mixture; N,N'-methylenebisacrylamide and ammonium persulfate are added sequentially to the mixture to form a homogeneous reaction solution.

[0032] In some embodiments, in step S2, the hydrothermal treatment temperature is 190-200°C and the time is 7-10 hours.

[0033] In some embodiments, the mass ratio of acrylamide, N,N-dimethylacrylamide, methyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate is 14-16:8-10:5-7:2:1.

[0034] The CDs preparation method provided by this invention uses inexpensive and readily available raw materials, and the preparation cost is controllable. Therefore, the resulting CDs are low in cost and easy to disperse.

[0035] This application provides a method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs, comprising the following steps: At room temperature, CDs are stirred at 300-500 r / min for 10-20 min to disperse them in the solution water to obtain a CDs solution; Add the amphoteric surfactant to the CDs solution and stir at 300-500 r / min for 10-20 min until it is fully dissolved to obtain an amphiphilic carbon point enhanced thickening waterflooding system suitable for high-salt reservoirs.

[0036] This application provides an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for mining high-salinity reservoirs with a mineralization of not less than 210,000 mg / L.

[0037] Source of raw materials The method for preparing CDs includes the following steps: CDs were prepared using a hydrothermal method. Specifically, 1.5 g of acrylamide (AM), 0.9 g of N,N-dimethylacrylamide (DMAM), and 0.6 g of methyl methacrylate (MMA) were added sequentially to a beaker, followed by 100 mL of deionized water. The mixture was magnetically stirred for 10 min until homogeneous. Then, 0.2 g of N,N'-methylenebisacrylamide (MBA) was added, and stirring continued for 5 min until completely dissolved. Next, 0.1 g of ammonium persulfate (APS) was added, and stirring was continued for 5 min to form a homogeneous reaction solution. The solution was transferred to a high-pressure reactor and reacted at 190 °C for 7 h. After the reaction, the oven was closed, and the reactor was allowed to cool naturally to room temperature. The brownish-yellow transparent suspension was removed, vacuum filtered through a 0.22 μm aqueous filter membrane, and the filtrate was transferred to a dialysis bag with a molecular weight cutoff of 3500 Da. The solution was then purified by dialyzing in deionized water for 48 h. Freeze-dry for 24 hours to obtain a light yellow fluffy solid powder, which is the amphiphilic carbonized polymer dots (CDs) with a particle size ≤1nm.

[0038] The following specific embodiments further illustrate this solution.

[0039] Example 1 A method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs includes the following steps: 0.3 g CDs were added to 100 mL of high mineral water and stirred at 500 r / min for 20 min to obtain a CDs solution. Weigh 2g of OAB into the CDs solution and stir with a mechanical stirrer at a stirring speed of 500r / min for 20min until it is fully dissolved to obtain an amphiphilic carbon point enhanced thickening water drive system suitable for high-salt reservoirs.

[0040] Example 2-3 A method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs is described. The other contents are the same as in Example 1, except that OAB is replaced sequentially with oleamidopropyl hydroxysulfonate betaine (OHSB) and erucamide propyl dimethyl betaine (EAB).

[0041] Examples 4-7 A method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs is described. The other contents are the same as in Example 1, except that the amount of OAB is adjusted from 2g to 1g, 3g, 4g, and 5g in sequence.

[0042] Examples 8-11 A method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs is described. The other contents are the same as in Example 1, except that the amount of 0.3g CDs is adjusted to 0.1g, 0.5g, 0.7g, and 0.9g in sequence.

[0043] Comparative Examples 1-3 A water-driven system comprising, in sequence, 2g OHSB, 2g EAB, and 2g OAB.

[0044] Comparative Examples 4-8 A water-driven system comprising, in sequence, 1gOAB, 2gOAB, 3gOAB, 4gOAB, and 5gOAB.

[0045] Comparative Examples 9-13 A water-driven system, otherwise identical to Example 1, except that 0.3g CDs are replaced sequentially with 0.1g SiO2, 0.3g SiO2, 0.5g SiO2, 0.7g SiO2, and 0.9g SiO2.

[0046] Comparative Examples 14-18 A water-drive system is identical to Example 1 except that 0.3g CDs are replaced sequentially with 0.1g TiO2, 0.3g TiO2, 0.5g TiO2, 0.7g TiO2, and 0.9g TiO2.

[0047] Comparative Example 19 A water-drive system, otherwise identical to Example 1, except that it does not contain CDs.

[0048] Comparative Examples 20-25 A water-driven system, otherwise identical to Example 1, except that the high-mineral water is replaced with distilled water, and the amounts of CDs are 0g, 0.1g, 0.3g, 0.5g, and 0.7g respectively.

[0049] Comparative Example 26 A water-drive system, otherwise identical to Example 1, except that CDs are replaced with amphiphilic carbon dots (the synthesis method of which can be found in Chinese Patent CN120504314A).

[0050] Comparative Example 27 A water-driven system, otherwise identical to Example 1, except that the amphoteric surfactant is replaced with lauryl dimethylamine oxide (OA-12, amine oxide amphoteric surfactant).

[0051] Testing and Evaluation Viscosity tests were performed on the water-driven system of Example 1: a DVⅢpro viscometer (Brookfield, USA) was used at room temperature for 170 seconds. -1 The apparent viscosity of the system solution was measured under the following conditions: 60 mL of the prepared amphiphilic carbonized polymer-enhanced thickening waterflooding system suitable for high-salt reservoirs was transferred to a 100 mL PTFE-lined autoclave and aged in a 90℃ oven for 15 days and 30 days. After aging, the reactor was allowed to cool naturally to room temperature. The solution was then removed and the apparent viscosity of the system solution was measured using a DVⅢpro viscometer. The results are shown in Table 1.

[0052] Table 1. Apparent viscosity of 2g OAB after aging with the addition of 0.3g CDs (unit: mPa·s)

[0053] The above results demonstrate that the system performs excellently in high-temperature and high-salt environments. At the same time, the system is low in cost, simple to prepare, and easy to implement on a large scale in the field.

[0054] Viscosity tests were performed on the water-driven systems of other embodiments and comparative examples: a DVⅢpro viscometer (Brookfield, USA) was used at room temperature for 170 seconds. -1 The apparent viscosity of the system solution was measured under the specified conditions, and the results are shown in Table 2.

[0055] Table 2. Apparent viscosity (mPa·s) of 2g of different types of zwitterionic surfactants with and without the addition of 0.3g CDs.

[0056] Table 3 Apparent viscosity of OAB with and without the addition of 0.3 g CDs at different concentrations (unit: mPa·s)

[0057] Table 4. Apparent viscosity (mPa·s) of 2g OAB with different types of nanoparticles (CDs, SiO2, TiO2)

[0058] Table 5. Apparent viscosity of 2g OAB with different concentrations of CDs added to different water solutions (unit: mPa·s)

[0059] Table 6 Apparent viscosity of different types of amphiphilic carbon dots (unit: mPa·s)

[0060] Experimental results show that, compared with the control examples, adding CDs significantly improves the viscosity of OAB compared to OHSB and EAB. The control examples also show that with increasing nanoparticle count, the apparent viscosity of the system initially increases and then decreases, reaching its maximum at 0.3g. Therefore, 0.3g is the optimal amount of CDs. Furthermore, compared with systems adding SiO2 and TiO2, adding CDs significantly increases the apparent viscosity, confirming that the amphiphilic carbonized polymer-based point-enhanced thickening waterflooding system suitable for high-salinity reservoirs has excellent viscosity-enhancing effects (see...). Figure 1 (The yellow dotted line represents the apparent viscosity of a single 2g OAB).

[0061] CDs, as novel nanoparticles, possess both hydrophilic (-CO-NH2, -OH) and hydrophobic (-N(CH3)2, -COOCH3) groups on their surface. A schematic diagram of their molecular structure is shown below. Figure 2 As shown.

[0062] The particle size distribution diagrams of CDs and OAB are as follows: Figure 3 As shown, the single system OAB mainly exists in deionized water in the form of monomers or small aggregates. After the addition of CDs, the hydrodynamic diameter increases and the distribution becomes wider, suggesting that the system can form longer linear WLMs and larger-scale three-dimensional entangled networks, which increases the viscosity of the system and helps its stability in high-salt environments. Cryo-transmission electron microscopy (cryo-TEM) images of CDs and OAB are shown below. Figure 4 As shown. Figure 4The arrangement of CDs along linear micelles in the OAB / CDs system is clearly shown (marked by yellow circles), indicating that CDs tend to adsorb onto linear micelles. Furthermore, red circles mark the aggregation of CDs at multiple micelle entanglement points, enhancing entanglement strength. The presence of CDs not only increases micelle rigidity and reduces deformation but also participates in micelle formation, strengthening the overall network structure. This invention provides a method for synthesizing amphiphilic carbonized polymer dots suitable for high-salinity reservoirs, and particle size distribution analysis and cryo-electron microscopy experiments clarify the synergistic effect of CDs and surfactants.

[0063] In Comparative Example 26, the amphiphilic carbon dots described in Chinese Patent CN120504314A were prepared by a solvothermal reaction of alkylphenol polyoxyethylene ether and glucose as raw materials. They have no cross-linked structure, and their hydrophobic groups are neutral alkylbenzene rings without potential points. In this application, the hydrophobic tertiary amine group (-N(CH3)2) of the CDs is protonated under high salt conditions (-N... + (CH3)2H), positively charged, can react with the -COO group of betaine. - The formation of a weak electrostatic attraction between positive and negative molecules strengthens the binding of carbon dots and betaine, promoting the tight aggregation of composite micelles and providing the core driving force for thickening.

[0064] In Comparative Example 27, the N-oxide structure of OA-12 prevents it from forming a dual effect of "strong electrostatic + strong hydrogen bond" with CDs, unlike the betaine type, resulting in a worse thickening effect under high salt conditions.

[0065] The CDs proposed in this invention work synergistically with amphoteric surfactants to form a stable three-dimensional network structure, exhibiting excellent thickening and salt resistance properties. They can maintain high interfacial activity even under high salinity conditions, improve the viscosity of surfactants in high-salt water, and significantly enhance stability and salt resistance.

[0066] The amphiphilic carbonized polymer point-enhanced thickening waterflooding system proposed in this invention, suitable for high-salt reservoirs, has good viscosity-enhancing and salt-resistant properties. It exhibits good viscosity-enhancing properties under high-salt conditions (210,000 mg / L), with a viscosity-enhancing effect of up to 2 times. After aging for 15 and 30 days, the apparent viscosity is still higher than that of the system without added CDs.

[0067] The present invention provides an amphiphilic carbonized polymer point-enhanced thickening waterflooding system suitable for high-salinity reservoirs. It is low in cost, simple to prepare, easy to disperse (not dependent on ultrasonic dispersion), and convenient for large-scale field construction.

[0068] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A waterflooding system for enhancing and thickening waterflooding with amphiphilic carbon dots, suitable for high-salinity reservoirs, characterized in that, The mixture includes a solution of water and a composite aggregate formed by CDs and an amphoteric surfactant; the CDs are adsorbed on linear micelles formed by the surfactant and aggregate at multiple micelle entanglement points; the particle size of the CDs is ≤1 nm, and the surface of the CDs simultaneously contains hydrophilic and hydrophobic groups, wherein the hydrophilic groups are -CO-NH2 and -OH, and the hydrophobic groups are -N(CH3)2 and -COOCH3.

2. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 1, characterized in that, The amphoteric surfactant is a betaine-type surfactant and / or an imidazoline-type surfactant.

3. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 1, characterized in that, The solution water is highly mineralized water with a total mineralization of 200,000-210,000 mg / L.

4. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 1, characterized in that, Based on 100 mL of prepared water, it contains 0.5-5.5 g of amphoteric surfactants and 0.1-1.2 g of CDs.

5. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 1, characterized in that, The CDs are prepared as follows: S1. Mix acrylamide, N,N-dimethylacrylamide, methyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate to form a homogeneous reaction solution; S2. Under closed conditions, the homogeneous reaction liquid is subjected to hydrothermal treatment to obtain the CDs.

6. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 5, characterized in that, In step S1, acrylamide, N,N-dimethylacrylamide, and methyl methacrylate are dispersed in water to obtain a mixture; N,N'-methylenebisacrylamide and ammonium persulfate are added sequentially to the mixture to form a homogeneous reaction solution.

7. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 5, characterized in that, In step S2, the hydrothermal treatment temperature is 190-200℃ and the time is 7-10h.

8. The amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs according to claim 5, characterized in that, The mass ratio of acrylamide, N,N-dimethylacrylamide, methyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate is 14-16:8-10:5-7:2:

1.

9. A method for preparing an amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salinity reservoirs as described in any one of claims 1-8, characterized in that, Includes the following steps: At room temperature, CDs were dispersed in the solution water to obtain a CDs solution; The amphoteric surfactant is added to the CDs solution and stirred until homogeneous to obtain the amphiphilic carbon dot-enhanced thickening waterflooding system suitable for high-salt reservoirs.

10. The application of an amphiphilic carbon point enhanced thickening waterflooding system as described in any one of claims 1-8 in the exploitation of high-salinity oil reservoirs with a mineralization of 200,000-250,000 mg / L.

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