Two-dimensional nano-carbon quantum chip based on oxidation cutting and preparation method and application of two-dimensional nano-carbon quantum chip

Abstract

The invention relates to the technical field of oilfield development, and discloses a two-dimensional nano carbon quantum sheet based on oxidation cutting and a preparation method and application thereof. The method comprises the following steps: (1) grinding and mixing salt crystals and melamine to obtain a salt-melamine compound, then carrying out ultrasonic mixing on the salt-melamine compound and ethylene tar in an organic solvent, and evaporating the obtained mixture to obtain a carbon nanosheet precursor; and (2) carrying out carbonization treatment on the carbon nanosheet precursor in an inert atmosphere, then carrying out acid pickling on the obtained carbonized solid, and then sequentially carrying out suction filtration, drying and grinding to obtain the two-dimensional carbon nanosheet. The two-dimensional carbon nanosheet based on oxidation cutting prepared by the method provided by the invention can improve microscopic oil washing efficiency and macroscopic sweep efficiency through a dual mechanism of reducing interfacial tension and optimizing rock wettability, and ultimately improves crude oil recovery efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield development, in particular to a two-dimensional nanocarbon quantum sheet based on oxidative cutting and a preparation method and application thereof. BACKGROUND

[0002] The preparation technology of two-dimensional nanocarbon quantum sheets (2D Nanocarbon Quantum Sheets, NQS) originated from the exploration of dimensional control of carbon materials. Early carbon material researches were mostly focused on zero-dimensional, one-dimensional and three-dimensional structures, while two-dimensional sheet structure became a key research direction to break through the performance bottleneck of traditional carbon materials due to its atomic-level thinness, high specific surface area and unique electronic conduction characteristics. The successful exfoliation of graphene in 2004 laid a methodological foundation for the preparation of two-dimensional carbon materials, but the lack of band gap of graphene limited its application in the field of optoelectronics, so researchers began to explore two-dimensional nanocarbon quantum sheets with controllable band gap. Early preparation was mainly based on the "top-down" strategy, such as mechanical exfoliation method and liquid phase exfoliation method. The former obtained a small amount of high-quality thin sheets by tape stripping of highly oriented pyrolytic graphite (HOPG), but it was difficult to scale production. The latter dispersed bulk carbon materials into sheet structure by means of ultrasonic, solvent intercalation and other means, which improved the yield, but the product size was uneven and the edge defects were more, which restricted its industrial application process. SUMMARY

[0003] The purpose of the present application is to overcome the problems of poor environmental protection, uncontrollable reaction, insufficient product performance, high industrialization threshold and limited application scenarios in the preparation process of traditional two-dimensional carbon nanomaterials, and to provide a two-dimensional nanocarbon quantum sheet based on oxidative cutting and a preparation method and application thereof. The two-dimensional nanocarbon quantum sheet based on oxidative cutting prepared according to the method of the present application can improve the micro-washing oil efficiency and macro-areal efficiency through the dual mechanisms of reducing the interfacial tension and optimizing the rock wettability, and ultimately improve the oil recovery.

[0004] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a two-dimensional nanocarbon quantum sheet based on oxidative cutting, which comprises the following steps:

[0005] (1) grinding and mixing salt crystals and melamine to obtain a salt-melamine composite, then ultrasonically mixing the salt-melamine composite and ethylene tar in an organic solvent, and evaporating the obtained mixture to obtain a carbon nanosheet precursor;

[0006] (2) carbonizing the carbon nanosheet precursor under an inert atmosphere, then acid washing the obtained carbonized solid, and then sequentially performing suction filtration, drying and grinding to obtain a two-dimensional carbon nanosheet;

[0007] (3) The two-dimensional carbon nanosheets and hydrogen peroxide are reacted, and then the resulting reaction product is separated into solid and liquid components.

[0008] Preferably, in step (1), the mass-volume ratio of the salt-melamine complex, the ethylene tar, and the organic solvent is 11 g:(0.1-0.8) g:(15-30) mL.

[0009] Preferably, the organic solvent is at least one selected from benzene, toluene, ethylbenzene, and xylene.

[0010] Preferably, the method further includes preparing the salt crystals by the following steps: mixing potassium chloride and calcium chloride at a mass ratio of 3:1-3, dispersing the resulting mixture in water and sonicating it, and then recrystallizing it.

[0011] Preferably, in step (2), the carbonization conditions include: a temperature of 700-900℃ and a time of 2-4h.

[0012] Preferably, in step (2), the concentration of the acid solution used in the pickling process is 0.5-2 mol / L.

[0013] Preferably, the inorganic acid used in the pickling process is at least one of hydrochloric acid, nitric acid, and sulfuric acid.

[0014] Preferably, in step (2), the pickling conditions include: a temperature of 70-90°C and a time of 12-48h.

[0015] Preferably, in step (3), the mass-volume ratio of the two-dimensional carbon nanosheets and the hydrogen peroxide solution is 1g:100-200mL.

[0016] Preferably, the hydrogen peroxide solution has a volume fraction of 5-12 vol%.

[0017] Preferably, in step (3), the reaction conditions include: a temperature of 140-200℃ and a time of 6-10h.

[0018] A second aspect of the present invention provides a two-dimensional carbon nanosheet based on oxidation cutting prepared by the method described above.

[0019] A third aspect of the present invention provides an oil displacement agent containing the two-dimensional nano-carbon quantum sheets based on oxidation cutting as described above.

[0020] According to the method for preparing two-dimensional carbon nanosheets based on oxidation cutting described in this invention, a eutectic salt system can be used as a template agent to achieve precise control over the size and morphology of the carbon sheets. Then, hydrogen peroxide is used to obtain the two-dimensional carbon nanosheets based on oxidation cutting. This preparation method is simple; hydrogen peroxide decomposes only into water and oxygen, leaving no harmful residues. The reaction conditions are mild, with low safety risks. Furthermore, the size and structure of the product can be precisely controlled by adjusting reaction parameters, avoiding the problems of high pollution, high energy consumption, and uneven product development associated with traditional methods. In addition, the two-dimensional carbon nanosheets based on oxidation cutting have functional groups such as hydroxyl and carboxyl groups on their surface, allowing the product to be stably dispersed in aqueous solution without the need for additional dispersants, exhibiting strong dispersion stability. The abundant functional groups on the particle surface give it superior interfacial activity compared to traditional nanomaterials. Attached Figure Description

[0021] Figure 1 The images shown are scanning electron microscope (SEM) images of two-dimensional carbon nanosheets prepared by oxidation cutting in Example 1 of the present invention, wherein (a) is an SEM image with a scale bar of 50 nm and (b) is an SEM image with a scale bar of 20 nm.

[0022] Figure 2 XPS spectra of two-dimensional carbon nanosheets and two-dimensional carbon nanosheets based on oxidative cutting prepared in Example 1 of this invention. Detailed Implementation

[0023] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The method for preparing two-dimensional carbon nanosheets based on oxidation cutting according to the present invention includes the following steps:

[0026] (1) Salt crystals and melamine are ground and mixed to obtain a salt-melamine composite. Then, the salt-melamine composite and ethylene tar are ultrasonically mixed in an organic solvent, and the resulting mixture is evaporated to obtain a carbon nanosheet precursor.

[0027] (2) The carbon nanosheet precursor is carbonized in an inert atmosphere, and then the resulting carbonized solid is acid washed, followed by filtration, drying and grinding to obtain two-dimensional carbon nanosheets.

[0028] (3) The two-dimensional carbon nanosheets and hydrogen peroxide are reacted, and then the resulting reaction product is separated into solid and liquid components.

[0029] In step (1), the mass-volume ratio of the salt-melamine complex, the ethylene tar and the organic solvent can be 11g:(0.1-0.8)g:(15-30)mL, preferably 11g:(0.2-0.4)g:(18-25)mL.

[0030] In the method described in this invention, the organic solvent can be at least one selected from benzene, toluene, ethylbenzene, and xylene. In the most preferred embodiment, the organic solvent is toluene.

[0031] In the method described in this invention, the method further includes preparing the salt crystals according to the following steps: mixing potassium chloride and calcium chloride at a mass ratio of 3:1-3, then dispersing the resulting mixture in water and subjecting it to ultrasonic treatment, followed by recrystallization. The ultrasonic treatment conditions may include a frequency of 20-130 kHz and a time of 30-60 min. The salt crystals are a eutectic salt system and have a high specific surface area. The salt crystals can melt during the carbonization process, forming a liquid environment that allows the reactants to dissolve in the liquid phase, providing a uniform reaction temperature. The salt crystals can serve as a template agent, enabling precise control of the size and morphology of the carbon sheet. The salt crystals can effectively reduce the introduction of impurities, improve the purity of the carbon sheet, and avoid agglomeration, resulting in carbon sheets with uniform size distribution.

[0032] In step (1), the grinding and mixing time can be 3-12 minutes. Preferably, the grinding and mixing time is 5-8 minutes. The grinding and mixing process can be carried out in a mortar.

[0033] In step (1), the conditions for ultrasonic mixing may include a frequency of 20-130 kHz and a time of 0.1-2 h. Preferably, the conditions for ultrasonic mixing include a frequency of 80-130 kHz and a time of 0.5-1 h. The ultrasonic mixing process can be performed in an ultrasonic cleaner.

[0034] In step (1), the evaporation conditions may include a temperature of 70-95°C and a time of 3-5 hours. Preferably, the evaporation conditions include a temperature of 75-90°C and a time of 3.5-4 hours. The evaporation process can be carried out by heating in an oil bath. The evaporation process is used to remove and recover the organic solvent.

[0035] In step (2), the carbonization conditions may include a temperature of 700-900℃ and a time of 2-4 hours. Preferably, the carbonization conditions include a temperature of 750-850℃ and a time of 2.5-3.5 hours. The carbonization process can be carried out in a tubular furnace.

[0036] In the method described in this invention, the inert atmosphere can be provided by at least one of nitrogen, argon, and helium. In the most preferred embodiment, the inert atmosphere is provided by nitrogen. The gas flow rate of the inert atmosphere can be 200-500 mL / min, preferably 300-400 mL / min.

[0037] In step (2), the concentration of the acid solution used in the pickling process can be 0.5-2 mol / L, preferably 0.8-1.5 mol / L. The inorganic acid used in the pickling process can be at least one of hydrochloric acid, nitric acid, and sulfuric acid. In the most preferred embodiment, the inorganic acid used in the pickling process is hydrochloric acid. The mass-to-volume ratio of the carbonized solid to the acid solution used in the pickling process can be 0.5 g: 100-300 mL, preferably 0.5 g: 150-250 mL.

[0038] In step (2), the pickling conditions may include: a temperature of 70-90°C and a time of 12-48 hours. Preferably, the pickling conditions include: a temperature of 75-85°C and a time of 20-30 hours. The specific pickling process may include: mixing the carbonized solid with an acid solution, followed by ultrasonic treatment for 0.5-1 hours, and then heating to the target temperature. The pickling process is used to remove the salt crystals.

[0039] In step (2), the filtration conditions may include: a pressure of -0.12 to -0.08 MPa and a time of 10-30 min. Preferably, the filtration conditions include: a pressure of -0.11 to -0.09 MPa and a time of 20-30 min. The filtration process can be carried out using a circulating water vacuum pump and a filtration flask. In this invention, the pressure is gauge pressure.

[0040] In step (2), the drying conditions may include a temperature of 50-70°C and a time of 12-24 hours. Preferably, the drying conditions include a temperature of 55-65°C and a time of 15-20 hours. The drying process can be carried out in various conventional drying ovens available in the art.

[0041] In step (2), the grinding time can be 3-12 minutes. Preferably, the grinding time is 5-8 minutes. The grinding process can be carried out in a mortar.

[0042] In step (3), the mass-to-volume ratio of the two-dimensional carbon nanosheets and the hydrogen peroxide can be 1 g: 100-200 mL, preferably 1 g: 120-180 mL. Preferably, the hydrogen peroxide is used in the form of an aqueous solution. The volume fraction of the aqueous solution of hydrogen peroxide can be 5-12 vol%, preferably 7.5-10 vol%.

[0043] In step (3), the reaction conditions may include a temperature of 140-200℃ and a time of 6-10h. Preferably, the reaction conditions include a temperature of 150-180℃ and a time of 7-9h. The specific operation of the reaction includes: mixing the two-dimensional carbon nanosheets and hydrogen peroxide, then subjecting them to ultrasonic treatment at a power of 300-500W, followed by heating to the target temperature at a rate of 3-5℃ / min and then proceeding with the reaction. The reaction process can be carried out in a high-pressure reactor with a polytetrafluoroethylene liner.

[0044] In step (3), preferably, the solid-liquid separation is performed by centrifugation. The conditions for centrifugation may include: a rotation speed of 8000-10000 rpm and a time of 10-15 min. The centrifugation may be performed once or multiple times, preferably multiple times. The centrifugation process is repeated until the filtrate from the washed solid phase is neutral.

[0045] The present invention also provides two-dimensional carbon nanosheets based on oxidative cutting prepared by the above method. These two-dimensional carbon nanosheets based on oxidative cutting exhibit good dispersibility and stability, and possess excellent interfacial activity.

[0046] The present invention also provides an oil displacement agent containing the two-dimensional nano-carbon quantum sheets based on oxidation cutting as described above.

[0047] The following examples further illustrate the two-dimensional carbon nanosheets based on oxidation cutting described in this invention. These examples are implemented based on the technical solution of this invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this invention is not limited to the following examples.

[0048] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0049] Example 1

[0050] (1) Weigh 10g of potassium chloride and calcium chloride in a mass ratio of 3:2 and disperse them in deionized water. Then, sonicate them at a frequency of 80kHz for 40min to form a eutectic salt system. After recrystallization, salt crystals are obtained. Mix 1g of melamine with the salt crystals and grind them in a mortar for 5min. Then mix them with 0.5g of ethylene tar and 20mL of toluene and sonicate them at a frequency of 80kHz for 30min. Then evaporate them at 85℃ for 3.5h to obtain carbon nanosheet precursors.

[0051] (2) The carbon nanosheet precursor obtained in step (1) was placed in a tube furnace and nitrogen gas was introduced at a flow rate of 400 mL / min. Then, it was carbonized at 750 °C for 2.5 h. Then, 0.5 g of the carbonized solid was mixed with 200 mL of 1 mol / L hydrochloric acid solution and ultrasonically treated for 0.5 h. Then, it was heated to 80 °C for 24 h and filtered for 20 min under a pressure of -0.1 MPa. The solid was collected and placed in a drying oven and dried at 60 °C for 18 h. Then, it was transferred to a mortar and ground for 5 min to obtain two-dimensional carbon nanosheets.

[0052] (3) Add 1g of the two-dimensional carbon nanosheets obtained in step (2) to 150mL of hydrogen peroxide solution with a volume fraction of 7.5 vol%, and sonicate for 30min under a power of 400W. Then transfer it to a reaction vessel and react at 180℃ for 8h. Then centrifuge the obtained reaction product at a speed of 9000rpm for 12min, wash the separated solid product with deionized water, and repeat the centrifugation step until the washing filtrate is neutral to obtain two-dimensional carbon nanosheets A1 based on oxidation cutting.

[0053] Example 2

[0054] (1) Weigh 10g of potassium chloride and calcium chloride in a mass ratio of 3:2 and disperse them in deionized water. Then, sonicate them at a frequency of 80kHz for 40min to form a eutectic salt system. After recrystallization, salt crystals are obtained. Mix 1g of melamine with the salt crystals and grind them in a mortar for 5min. Then mix them with 0.25g of ethylene tar and 20mL of toluene and sonicate them at a frequency of 80kHz for 30min. Then evaporate them at 85℃ for 3.5h to obtain carbon nanosheet precursors.

[0055] (2) The carbon nanosheet precursor obtained in step (1) was placed in a tube furnace and nitrogen gas was introduced at a flow rate of 400 mL / min. Then, it was carbonized at 750 °C for 2.5 h. Then, 0.5 g of the carbonized solid was mixed with 200 mL of 1 mol / L hydrochloric acid solution and ultrasonically treated for 0.5 h. Then, it was heated to 80 °C for 24 h and filtered for 20 min under a pressure of -0.1 MPa. The solid was collected and placed in a drying oven and dried at 60 °C for 18 h. Then, it was transferred to a mortar and ground for 5 min to obtain two-dimensional carbon nanosheets.

[0056] (3) Add 1g of the two-dimensional carbon nanosheets obtained in step (2) to 150mL of hydrogen peroxide solution with a volume fraction of 10 vol%, and sonicate for 30min under a power of 400W. Then transfer it to a reaction vessel and react at 180℃ for 8h. Then centrifuge the obtained reaction product at a speed of 9000rpm for 12min, wash the separated solid product with deionized water, and repeat the centrifugation step until the washing filtrate is neutral to obtain two-dimensional carbon nanosheets A2 based on oxidative cutting.

[0057] Example 3

[0058] (1) Weigh 10g of potassium chloride and calcium chloride in a mass ratio of 3:2 and disperse them in deionized water. Then, sonicate them at a frequency of 80kHz for 40min to form a eutectic salt system. After recrystallization, salt crystals are obtained. Mix 1g of melamine with the salt crystals and grind them in a mortar for 5min. Then mix them with 0.25g of ethylene tar and 20mL of toluene and sonicate them at a frequency of 80kHz for 30min. Then evaporate them at 85℃ for 3.5h to obtain carbon nanosheet precursors.

[0059] (2) The carbon nanosheet precursor obtained in step (1) was placed in a tube furnace and nitrogen gas was introduced at a flow rate of 400 mL / min. Then, it was carbonized at 750 °C for 2.5 h. Then, 0.5 g of the carbonized solid was mixed with 200 mL of 1 mol / L hydrochloric acid solution and ultrasonically treated for 0.5 h. Then, it was heated to 80 °C for 24 h and filtered for 20 min under a pressure of -0.1 MPa. The solid was collected and placed in a drying oven and dried at 60 °C for 18 h. Then, it was transferred to a mortar and ground for 5 min to obtain two-dimensional carbon nanosheets.

[0060] (3) Add 1g of the two-dimensional carbon nanosheets obtained in step (2) to 150mL of hydrogen peroxide solution with a volume fraction of 7.5 vol%, and sonicate for 30min under a power of 400W. Then transfer it to a reaction vessel and react at 150℃ for 8h. Then centrifuge the obtained reaction product at a speed of 9000rpm for 12min, wash the separated solid product with deionized water, and repeat the centrifugation step until the washing filtrate is neutral to obtain two-dimensional carbon nanosheets A3 based on oxidation cutting.

[0061] Example 4

[0062] (1) Weigh 10g of potassium chloride and calcium chloride in a mass ratio of 3:2 and disperse them in deionized water. Then, sonicate them at a frequency of 80kHz for 40min to form a eutectic salt system. After recrystallization, salt crystals are obtained. Mix 1g of melamine with the salt crystals and grind them in a mortar for 5min. Then mix them with 0.75g of ethylene tar and 20mL of toluene and sonicate them at a frequency of 80kHz for 30min. Then evaporate them at 85℃ for 3.5h to obtain carbon nanosheet precursors.

[0063] (2) The carbon nanosheet precursor obtained in step (1) was placed in a tube furnace and nitrogen gas was introduced at a flow rate of 400 mL / min. Then, it was carbonized at 750 °C for 2.5 h. Then, 0.5 g of the carbonized solid was mixed with 200 mL of 1 mol / L hydrochloric acid solution and ultrasonically treated for 0.5 h. Then, it was heated to 80 °C for 24 h and filtered for 20 min under a pressure of -0.1 MPa. The solid was collected and placed in a drying oven and dried at 60 °C for 18 h. Then, it was transferred to a mortar and ground for 5 min to obtain two-dimensional carbon nanosheets.

[0064] (3) Add 1g of the two-dimensional carbon nanosheets obtained in step (2) to 150mL of hydrogen peroxide solution with a volume fraction of 10vol%, and sonicate for 30min under a power of 400W. Then transfer it to a reaction vessel and react at 150℃ for 8h. Then centrifuge the obtained reaction product at a speed of 9000rpm for 12min, wash the separated solid product with deionized water, and repeat the centrifugation step until the washing filtrate is neutral to obtain two-dimensional carbon nanosheets A4 based on oxidative cutting.

[0065] Example 5

[0066] (1) Weigh 10g of potassium chloride and calcium chloride in a mass ratio of 3:2 and disperse them in deionized water. Then, sonicate them at a frequency of 80kHz for 40min to form a eutectic salt system. After recrystallization, salt crystals are obtained. Mix 1g of melamine with the salt crystals and grind them in a mortar for 5min. Then mix them with 0.5g of ethylene tar and 20mL of toluene and sonicate them at a frequency of 80kHz for 30min. Then evaporate them at 85℃ for 3.5h to obtain carbon nanosheet precursors.

[0067] (2) The carbon nanosheet precursor obtained in step (1) was placed in a tube furnace and nitrogen gas was introduced at a flow rate of 400 mL / min. Then, it was carbonized at 750 °C for 2.5 h. Then, 0.5 g of the carbonized solid was mixed with 200 mL of 1 mol / L hydrochloric acid solution and ultrasonically treated for 0.5 h. Then, it was heated to 80 °C for 24 h and filtered for 20 min under a pressure of -0.1 MPa. The solid was collected and placed in a drying oven and dried at 60 °C for 18 h. Then, it was transferred to a mortar and ground for 5 min to obtain two-dimensional carbon nanosheets.

[0068] (3) Add 1g of the two-dimensional carbon nanosheets obtained in step (2) to 150mL of hydrogen peroxide solution with a volume fraction of 20vol%, and sonicate for 30min under a power of 400W. Then transfer it to a reaction vessel and react at 150℃ for 8h. Then centrifuge the obtained reaction product at a speed of 9000rpm for 12min, wash the separated solid product with deionized water, and repeat the centrifugation step until the washing filtrate is neutral to obtain two-dimensional carbon nanosheets A5 based on oxidation cutting.

[0069] Example 6

[0070] Two-dimensional carbon nanosheets based on oxidative cutting were prepared according to the method of Example 1, except that in step (3), the volume fraction of hydrogen peroxide solution was 3 vol%, resulting in two-dimensional carbon nanosheets A6 based on oxidative cutting.

[0071] Example 7

[0072] Two-dimensional carbon nanosheets based on oxidation cutting were prepared according to the method of Example 1, except that in step (3), the reaction temperature was adjusted to 120°C to obtain two-dimensional carbon nanosheets A7 based on oxidation cutting.

[0073] Comparative Example 1

[0074] Commercially available molybdenum disulfide (MoS2) nanosheets were used as comparative sample D1. The molybdenum disulfide nanosheets were purchased from Sigma-Aldrich, catalog number: 901792-250MG, with a size of 50-1000 nm.

[0075] Comparative Example 2

[0076] Commercially available graphene oxide (GO) was used as a comparative sample D2. The graphene oxide was purchased from Suzhou CarbonFeng Technology Co., Ltd., model number: GO01L7440-44-0, with a size of 100-500nm.

[0077] Comparative Example 3

[0078] Two-dimensional carbon nanosheets based on oxidative cutting were prepared according to the method of Example 1, except that calcium chloride was not added in step (1) to obtain carbon nanosheet D3.

[0079] Comparative Example 4

[0080] Two-dimensional carbon nanosheets based on oxidative cutting were prepared according to the method of Example 1, except that in step (1), melamine was replaced with urea to obtain carbon nanosheet D4.

[0081] Test case

[0082] The characterization and testing methods for the various physicochemical properties of the samples in the above embodiments and comparative examples are as follows:

[0083] (1) Determination of oil-water interfacial tension: The test samples were prepared into a 0.1 wt% solution with water, and the interfacial tension of each system was determined using dynamic droplet morphology analysis. A Tracker-H interfacial rheometer (Texex) was used for measurement. This instrument uses a control module to precisely regulate the droplet volume; the image acquisition module captures the droplet morphology in real time, and the image analysis and processing module calculates the droplet parameters, the dynamic expansion modulus of the interfacial film, and the dynamic interfacial tension. Simulated oil was used as the internal phase of the droplets. The simulated oil was prepared by mixing dehydrated crude oil from Changqing Oilfield with kerosene at a mass ratio of 1:3. The kerosene was sourced from Sinopharm Chemical Reagent Co., Ltd. The solution prepared from the test samples was used as the external phase of the droplets. During the experiment, the interfacial rheological test was performed using area sinusoidal oscillation, and the measurement temperature was 25℃. The results of the oil-water interfacial tension measurements for the above examples and comparative examples are shown in Table 1 below.

[0084] (2) Measurement of rock wall adhesion: The test samples were prepared with water to a 0.1% (w / w) solution. Outcrop sandstone cores were subjected to oleophilic treatment to simulate the original hydrophobic-oleophilic surface. The treated cores were immersed in the prepared solution and allowed to stand at room temperature for 48 hours to achieve interface wetting control. A set of samples was taken every 12 hours, and the static contact angle of water droplets in air and the contact angle of oil droplets underwater were measured using a JC2000D2 contact angle meter. Each experiment was repeated at least three times, and the average value was taken. The static contact angles of water droplets in air and the contact angles of oil droplets underwater for the samples in the above embodiments and comparative examples are shown in Table 2 below.

[0085] (3) Oil displacement performance test: The test sample was prepared with water to form a 0.1% (w / w) solution as the displacement fluid. The tight sandstone core was placed in a vacuum chamber and evacuated for 12 hours to saturate with simulated formation water. The mass increment of the core after saturation with water was accurately measured, and the pore volume of the core was calculated. Simulated oil was injected into the core to fully saturate it, and then aged in an 80℃ constant temperature environment for 21 days to establish a stable original oil-wet environment. The displacement experiment was carried out at 60℃. First, simulated formation water drive was carried out at a flow rate of 0.1 mL / min until the water content in the produced fluid at the outlet exceeded 98%, and the cumulative oil production at this time was recorded as the water drive recovery rate benchmark. Subsequently, the oil displacement agent injection stage was entered at the same temperature: the displacement fluid was injected at the same flow rate (0.1 mL / min) for 40 minutes. After this stage, the inlet and outlet valves were closed, and the system was allowed to stand at 60℃ for 12 hours to simulate the well shut-in and simmering process. Finally, the valve was reopened, and subsequent waterflooding was performed under the same conditions until the water cut of the produced fluid was again above 98%. Throughout the experiment, the dynamic changes in injection pressure, oil production, and fluid production were monitored and recorded. The core parameters and recovery rate test results from the above examples and comparative experiments are shown in Table 3.

[0086] (4) Morphology and size characterization: The morphology and size of the two-dimensional carbon nanosheets based on oxidation cutting were characterized by scanning electron microscopy. Figure 1 (a) shows a scanning electron microscope image of the two-dimensional carbon nanosheet A1 based on oxidation cutting, with a scale bar of 50 nm; Figure 1 (b) shows a scanning electron microscope image of the two-dimensional carbon nanosheet A1 based on oxidative cutting, with a scale bar of 20 nm.

[0087] (5) XPS test: The structure of the sample was characterized by XPS. Table 2 shows the XPS spectra of the two-dimensional carbon nanotube quantum slices prepared in Example 1 and the two-dimensional carbon nanotube quantum sheet based on oxidation cutting prepared in Example 1 (i.e., the two-dimensional carbon nanotube quantum sheet A1 based on oxidation cutting).

[0088] Table 1

[0089]

[0090]

[0091] As can be seen from Table 1, the two-dimensional carbon nanosheets based on oxidative cutting prepared in this invention can significantly reduce the oil-water interfacial tension of the system. This indicates that the two-dimensional carbon nanosheets based on oxidative cutting prepared in this invention have better oil-water interfacial activity than conventional nanomaterials, are more easily adsorbed on the oil-water interface, thus reducing the oil-water interfacial tension and better performing the oil washing performance.

[0092] Table 2

[0093]

[0094] As can be seen from Table 2, the glass slides treated with the two-dimensional carbon nanosheets based on oxidation cutting prepared in this invention exhibit hydrophilic / strong oleophobic properties underwater, indicating that the two-dimensional carbon nanosheets based on oxidation cutting prepared in this invention have better wetting control performance than conventional nanomaterials, thus playing a better role in crude oil stripping performance.

[0095] Table 3

[0096]

[0097] As shown in Table 3, the two-dimensional carbon nanosheets based on oxidation cutting prepared by this invention can significantly improve the oil displacement effect. The mechanism is mainly attributed to its synergistic regulatory effect on oil-water interfacial tension and reservoir rock wettability. Its oil recovery rate as an oil displacement agent is much higher than that of the comparative example, reaching a maximum of 63.28%.

[0098] The test results from the above examples and comparative examples show that the two-dimensional carbon nanosheets based on oxidative cutting prepared according to the method of the present invention have good dispersion stability and excellent interfacial activity. Through the dual mechanisms of reducing interfacial tension and optimizing rock wettability, they jointly improve the micro-washing efficiency and macro-sweeping efficiency, and significantly improve the crude oil recovery rate.

[0099] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing two-dimensional carbon nanosheets based on oxidation cutting, characterized in that, The method includes the following steps: (1) Salt crystals and melamine are ground and mixed to obtain a salt-melamine composite. Then, the salt-melamine composite and ethylene tar are ultrasonically mixed in an organic solvent, and the resulting mixture is evaporated to obtain a carbon nanosheet precursor. (2) The carbon nanosheet precursor is carbonized in an inert atmosphere, and then the resulting carbonized solid is acid washed, followed by filtration, drying and grinding to obtain two-dimensional carbon nanosheets. (3) The two-dimensional carbon nanosheets and hydrogen peroxide solution are reacted, and then the resulting reaction product is separated into solid and liquid components.

2. The method according to claim 1, characterized in that, In step (1), the mass-volume ratio of the salt-melamine complex, the ethylene tar, and the organic solvent is 11 g: (0.1-0.8) g: (15-30) mL; Preferably, the organic solvent is at least one selected from benzene, toluene, ethylbenzene, and xylene.

3. The method according to claim 1 or 2, characterized in that, The method further includes preparing the salt crystals according to the following steps: Potassium chloride and calcium chloride were mixed in a mass ratio of 3:1-3, the resulting mixture was then dispersed in water and subjected to ultrasonic treatment, followed by recrystallization.

4. The method according to claim 1, characterized in that, In step (2), the carbonization conditions include a temperature of 700-900℃ and a time of 2-4h.

5. The method according to claim 1 or 4, characterized in that, In step (2), the concentration of the acid solution used in the pickling process is 0.5-2 mol / L; Preferably, the inorganic acid used in the pickling process is at least one of hydrochloric acid, nitric acid, and sulfuric acid.

6. The method according to claim 1, 4, or 5, characterized in that, In step (2), the pickling conditions include a temperature of 70-90°C and a time of 12-48h.

7. The method according to claim 1, characterized in that, In step (3), the mass-volume ratio of the two-dimensional carbon nanosheets to the hydrogen peroxide solution is 1g:100-200mL; Preferably, the hydrogen peroxide solution has a volume fraction of 5-12 vol%.

8. The method according to claim 1 or 7, characterized in that, In step (3), the reaction conditions include a temperature of 140-200℃ and a time of 6-10h.

9. Two-dimensional carbon nanosheets based on oxidative cutting prepared by the method according to any one of claims 1-8.

10. An oil displacement agent, characterized in that, It contains the two-dimensional carbon nanosheet based on oxidation cutting as described in claim 9.

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