Functionalized molybdenum disulfide nanosheets and their preparation method and application

Abstract

The present invention provides functionalized molybdenum disulfide nanosheets and a preparation method and application thereof. The preparation method comprises the following steps: mixing a solvent, 1 part by weight of thioctic acid, and 5 to 10 parts by weight of a first compound for 2 to 4 hours to obtain a mixture; adding 0.05 to 0.1 parts by weight of 1-hydroxybenzotriazole to the mixture, mixing for 24 to 48 hours, and drying to obtain an intermediate product; and ultrasonically treating or heat-treating the raw material-solution system to obtain the functionalized nanosheets, wherein the raw material-solution system comprises 5 to 10 parts by weight of molybdenum disulfide nanosheets, 1 part by weight of the intermediate product, and brine; and the first compound comprises an oxirane group and an alkylamine chain, wherein the alkylamine chain has 12 to 18 carbon atoms and the oxirane group has 2 to 15 carbon atoms. A nanofluid prepared from the functionalized molybdenum disulfide nanosheets can reduce oil / water interfacial tension, has good stability, significantly improves the recovery rate of low-permeability oil reservoirs, and reduces costs.

Description

Technical Field

[0001] The invention relates to a functionalized molybdenum disulfide nanosheet and a preparation method and application thereof, belonging to the technical field of petroleum extraction. Background Art

[0002] Against the backdrop of the rapid development of the petrochemical industry, the demand for oil resources continues to increase. Improving oil recovery is a crucial step in the oil development process, with significant potential economic value. Furthermore, as oil is mined, the proportion of low-permeability oilfields will continue to increase. There is an urgent need to effectively address the exploitation of low-permeability oilfields and promote the development of the oil industry.

[0003] Currently, oil reservoir development consists of three main stages: primary, secondary, and tertiary recovery. The combined recovery rate of primary and secondary recovery is only 50-60%, leaving a significant amount of oil trapped in the reservoir. Therefore, tertiary recovery (EOR) is essential to further enhance oil recovery. Tertiary oil recovery (EOR) typically uses various physical, chemical, or thermal methods to increase oil mobility in the reservoir, thereby improving oil recovery. Chemical methods are a common approach to EOR, typically injecting components such as polymers, surfactants, or a combination of these into the reservoir to alter the properties of the oil or rock, making it more fluid and thus enhancing recovery. However, polymers can clog the formation, causing irreversible damage to the reservoir. Another approach involves adding nanoparticles or functionalized nanoparticles to enhance oil recovery by modifying rock wettability, reducing interfacial tension, and increasing the viscosity of the injected fluid. Currently, nanomaterials used for oil displacement, including graphene, nanometal oxides, and some nanometallic oxides, suffer from high cost, poor dispersion stability, and limited effectiveness in enhancing oil recovery. Summary of the Invention

[0004] In response to the above-mentioned defects, the present invention provides a method for preparing functionalized molybdenum disulfide nanosheets. The functionalized molybdenum disulfide nanosheets obtained by this preparation method have a large specific surface area and low surface tension. Applying them to nanofluids can make the nanofluid have strong stability, greatly improve the recovery rate in low-permeability reservoirs, and also use seawater near the reservoir to reduce costs.

[0005] The present invention provides a functionalized molybdenum disulfide nanosheet, which is prepared according to the above method. The functionalized molybdenum disulfide nanosheet contains a large number of hydrophilic ethylene oxide groups and hydrophobic alkylamine chains on its surface, which can reduce the interfacial tension between oil and water, thereby significantly improving the recovery rate.

[0006] The present invention provides a nanofluid comprising the functionalized molybdenum disulfide nanosheets, thereby effectively improving the recovery rate of low-permeability oil reservoirs and thus improving the efficiency of oil production operations.

[0007] The present invention provides a displacement method, which achieves the purpose of improving the recovery rate by injecting nanofluid including functionalized molybdenum disulfide nanosheets into a reservoir.

[0008] The present invention provides a method for preparing functionalized molybdenum disulfide nanosheets, comprising the following steps:

[0009] 1) mixing a solvent, 1 part by weight of lipoic acid, and 5 to 10 parts by weight of a first compound for 2 to 4 hours to obtain a mixture;

[0010] 2) adding 0.05 to 0.1 parts by weight of 1-hydroxybenzotriazole to the mixture, mixing for 24 to 48 hours, and drying to obtain an intermediate product;

[0011] 3) ultrasonically treating or thermally treating the raw material-solution system to obtain functionalized nanosheets;

[0012] The raw material-solution system comprises 5 to 10 parts by weight of molybdenum disulfide nanosheets, 1 part by weight of the intermediate product and salt water;

[0013] The first compound contains an ethylene oxide group and an alkylamine chain;

[0014] The number of carbon atoms in the alkylamine chain of the first compound is 12 to 18, and the number of ethylene oxide groups is 2 to 15.

[0015] Furthermore, in step 3), the ultrasonic treatment comprises ultrasonicating the raw material-solution system for 4 to 12 hours and then stirring for 24 to 48 hours;

[0016] The heat treatment comprises reacting the raw material-solution system at 60-80° C. for 24-48 hours.

[0017] Furthermore, the molybdenum disulfide nanosheet has a layer thickness of 1 to 1.5 nm, a length of 50 to 100 nm, and a width of 50 to 100 nm.

[0018] Furthermore, the first compound includes at least one of tallow amine polyoxyethylene ether compounds, octadecylamine polyoxyethylene ether compounds, and coconut oil amine polyoxyethylene ether compounds.

[0019] The present invention also provides a functionalized molybdenum disulfide nanosheet, which is prepared by any of the above methods for preparing the functionalized molybdenum disulfide nanosheet.

[0020] The present invention also provides a nanofluid comprising the functionalized molybdenum disulfide nanosheets prepared by any one of the above items or the functionalized molybdenum disulfide nanosheets described above.

[0021] Furthermore, the concentration of the functionalized molybdenum disulfide nanosheets is 10 to 1000 ppm.

[0022] Furthermore, the oil / water interfacial tension of the nanofluid is 10 -3 ~10 -2 mN / m.

[0023] Furthermore, the nanofluid also includes one of salt water and deionized water;

[0024] The concentration of the brine is 10,000 to 220,000 mg / L.

[0025] The present invention also provides a displacement method, which uses any of the nanofluids described above to recover oil from a reservoir.

[0026] The present invention uses a first compound containing ethylene oxide groups and alkylamine chains, lipoic acid, and molybdenum disulfide nanosheets as raw materials, and 1-hydroxybenzotriazole as a catalyst to prepare functionalized molybdenum disulfide nanosheets. The alkylamine chains in the first compound have 12 to 18 carbon atoms, and the number of ethylene oxide groups is 2 to 15. The functionalized molybdenum disulfide nanosheets have hydrophilicity and the alkylamine chains are hydrophobic. When applied to nanofluids, the ethylene oxide and alkylamine chains work synergistically to reduce oil / water interfacial tension, thereby improving oil recovery. The functionalized molybdenum disulfide nanosheets are in a sheet-like shape, so the nanofluid has a high recovery rate and stability even in low-permeability reservoirs. Furthermore, the nanofluid can utilize seawater near the reservoir, reducing water consumption costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an SEM image of the molybdenum disulfide nanosheets of Example 3 of the present invention;

[0028] Figure 2 This is an SEM image of the functionalized molybdenum disulfide nanosheets of Example 3 of the present invention;

[0029] Figure 3 FTIR image of the functionalized molybdenum disulfide nanosheets of Example 3 of the present invention;

[0030] Figure 4 Graph showing the relationship between the stability of the nanofluids of Example 3 of the present invention and Comparative Example 1 over time;

[0031] Figure 5 Graph showing the relationship between the interfacial tension between the nanofluids of Examples 1-3 of the present invention and Comparative Example 1 and crude oil over time;

[0032] Figure 6 Graph showing the relationship between the volume of water and nanofluid injected into the core pores and the oil recovery rate for Examples 1-3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] The first aspect of the present invention provides a method for preparing functionalized molybdenum disulfide nanosheets, comprising the following steps:

[0035] 1) mixing a solvent, 1 part by weight of lipoic acid, and 5 to 10 parts by weight of a first compound for 2 to 4 hours to obtain a mixture;

[0036] 2) adding 0.05 to 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, mixing for 24 to 48 hours, and drying to obtain an intermediate product;

[0037] 3) ultrasonically treating or thermally treating the raw material-solution system to obtain functionalized nanosheets;

[0038] The raw material-solution system includes 5 to 10 parts by weight of molybdenum disulfide nanosheets, 1 part by weight of an intermediate product and salt water;

[0039] The first compound contains an ethylene oxide group and an alkylamine chain;

[0040] The number of carbon atoms in the alkylamine chain of the first compound is 12 to 18, and the number of ethylene oxide groups is 2 to 15.

[0041] Specifically, in step 1), the alkyl group in the alkylamine chain of the first compound is a straight chain, and the amino group therein is an imino group -NH-. During this process, lipoic acid and the first compound are fully mixed, laying the foundation for the subsequent dehydration condensation reaction.

[0042] The present invention does not impose too many restrictions on the type of solvent, for example, it can be selected from at least one of ethanol, dichloromethane, and N,N-dimethylformamide. When the aforementioned solvent is a mixture of multiple specific compounds, the present invention does not impose too many restrictions on the ratio between the specific compounds.

[0043] In step 2), 1-hydroxybenzotriazole acts as a catalyst to promote the dehydration condensation reaction between lipoic acid and the first compound to generate an intermediate product.

[0044] In step 3), the raw material-solution system is ultrasonically treated or heat-treated and then dried to obtain functionalized nanosheets; during this process, due to the presence of sulfur defects in the molybdenum disulfide nanosheets, the S atoms in the intermediate product can attach to the defect vacancies, thereby successfully grafting the intermediate product onto the surface of the molybdenum disulfide nanosheets to obtain the above-mentioned functionalized molybdenum disulfide nanosheets.

[0045] The present invention does not limit the preparation method of the molybdenum disulfide nanosheets. For example, the molybdenum disulfide nanosheets are prepared by a method comprising the following steps:

[0046] The molybdenum source, the sulfur source and the reducing agent are mixed in deionized water, and reacted under high temperature and high pressure to obtain a precipitated product. The precipitated product is washed with water and ethanol and dried to obtain the molybdenum disulfide nanosheets.

[0047] The present invention does not impose any particular restrictions on the types of the molybdenum source, sulfur source, and reducing agent. For example, the molybdenum source is selected from at least one of molybdenum oxide and ammonium molybdate, the sulfur source is selected from at least one of thioacetamide and thiourea, and the reducing agent is selected from at least one of ascorbic acid and urea. When the aforementioned three types of compounds are each a mixture of multiple specific compounds, the present invention does not impose any particular restrictions on the ratios of the individual specific compounds.

[0048] The present invention does not impose specific limitations on the concentration of the brine or the salt content of the brine. For example, the concentration of the brine can be 10,000 to 220,000 mg / L, and the salt content can be selected from at least one of sodium chloride, calcium chloride, magnesium chloride, sodium sulfate, and sodium bicarbonate. When the salt is selected from two or more of the aforementioned compounds, the present invention does not impose any specific limitations on the ratio of the specific compounds.

[0049] The present invention does not impose any particular restrictions on the drying temperature and drying time, as long as the intermediate product and the functionalized molybdenum disulfide nanosheet product are completely dried.

[0050] The present invention does not limit the sources of the components, and any commercially available product or a product prepared by a conventional preparation method well known to those skilled in the art may be used.

[0051] The present invention provides a method for preparing functionalized molybdenum disulfide nanosheets. A first compound containing an ethylene oxide group and an alkylamine chain is linked to the surface of a molybdenum disulfide nanosheet via a linker, lipoic acid, to produce the functionalized molybdenum disulfide nanosheets. The alkylamine chains have 12 to 18 carbon atoms, and the ethylene oxide groups have 2 to 15 carbon atoms. The alkylamine chains on the surface of the prepared functionalized molybdenum disulfide nanosheets are hydrophobic, while the ethylene oxide groups are hydrophilic. The alkylamine chains are hydrophobic and oleophilic, allowing them to interact with the oil phase, while the ethylene oxide is hydrophilic and oleophobic, allowing them to interact with water molecules through hydrogen bonds or other electrostatic interactions. This interaction disrupts the cohesive forces between water molecules and reduces the interfacial tension between oil and water, thereby improving oil recovery. The functionalized MoS2 nanosheets are flaky in shape, allowing them to penetrate smaller pores in the formation, significantly improving oil recovery in low-permeability reservoirs. Furthermore, the nanosheets form a "surface-to-surface" contact with the oil / water interface, creating a strong interfacial interaction that can further enhance oil recovery in low-permeability reservoirs. Furthermore, because the functionalized MoS2 nanosheets contain a high concentration of ethylene oxide groups, the resulting nanofluid exhibits excellent stability, even in highly salinized water. This nanofluid can also utilize seawater near the reservoir, reducing costs.

[0052] In addition, the preparation method is simple and convenient to operate, and the entire preparation process can be carried out at room temperature and pressure, with low risk and low energy consumption.

[0053] In one embodiment, in step 3), the ultrasonic treatment comprises ultrasonicating the raw material-solution system for 4 to 12 hours and then stirring for 24 to 48 hours;

[0054] The heat treatment comprises reacting the raw material-solution system at 60-80°C for 24-48 hours. When the ultrasonic treatment time and stirring time, or the reaction temperature, reaction time, and stirring time during the heat treatment are within the aforementioned ranges, sulfur defects on the molybdenum disulfide nanosheets and sulfur atoms in the intermediate product react better, thereby increasing the grafting rate of the molybdenum disulfide nanosheets.

[0055] The present invention does not specifically limit the stirring method. For example, the mixing can be performed by magnetic stirring or mechanical stirring.

[0056] In one embodiment, the MoS2 nanosheets have a thickness of 1 to 1.5 nm, a length of 50 to 100 nm, and a width of 50 to 100 nm. When the size of the MoS2 nanosheets is within the aforementioned range, the size of the resulting functionalized MoS2 nanosheets is also within the aforementioned range. When the size of the functionalized MoS2 nanosheets is within the aforementioned range, nanofluids containing the functionalized MoS2 nanosheets can more easily enter smaller pore throats, thereby improving the recovery efficiency of the nanofluid from low-permeability reservoirs.

[0057] The present invention does not impose too many restrictions on the first compound. For example, it can be selected from at least one of tallow amine polyoxyethylene ether compounds, octadecylamine polyoxyethylene ether compounds, and coconut oil amine polyoxyethylene ether compounds. It can be understood that the above three types of compounds include multiple specific compounds. The selected compounds in the present invention all meet the requirements that the number of carbon atoms in the alkylamine chain is 12 to 18 and the number of ethylene oxide groups is 2 to 15. Specifically, tallow amine polyoxyethylene ether compounds include PEG-5-tallowamine, PEG-10-tallowamine, and PEG-15-tallowamine; octadecylamine polyoxyethylene ether compounds include PEG-5-stearylamine, PEG-10-stearylamine, and PEG-15-stearylamine; and coconut oil amine polyoxyethylene ether compounds include PEG-5-coconutamine, PEG-10-coconutamine, and PEG-15-coconutamine. When the aforementioned first compound is a mixture of multiple specific compounds, the present invention does not impose too many restrictions on the ratio between the specific compounds.

[0058] A second aspect of the present invention provides functionalized molybdenum disulfide nanosheets prepared by any of the aforementioned methods for preparing functionalized molybdenum disulfide nanosheets. These functionalized molybdenum disulfide nanosheets contain hydrophilic ethylene oxide groups and hydrophobic alkylamine chains. When used in nanofluids, they can significantly reduce the interfacial tension between oil and water, enhance stability, and thereby improve oil recovery. Their sheet-like structure also enables good oil displacement in low-permeability reservoirs. Furthermore, nanofluids containing these functionalized molybdenum disulfide nanosheets can utilize seawater near the reservoir, resulting in low cost.

[0059] A third aspect of the present invention provides a nanofluid comprising the functionalized molybdenum disulfide nanosheets prepared according to any of the above-mentioned methods or the functionalized molybdenum disulfide nanosheets described above. Because the functionalized molybdenum disulfide nanosheets contained in this nanofluid contain ethylene oxide groups and alkylamine chains, the ethylene oxide groups are hydrophilic and oleophobic, while the alkylamine chains are hydrophobic and oleophilic. The synergistic effect of the ethylene oxide groups can reduce the surface tension between oil and water, thereby improving oil recovery. Furthermore, the nanofluid exhibits high oil recovery and stability even in low-permeability reservoirs. Seawater near the reservoir can also be used, reducing costs.

[0060] It is understood that other components may be included in addition to the functionalized nanosheets. In one embodiment, the concentration of the functionalized molybdenum disulfide nanosheets is 10 to 1000 ppm. Within this concentration range, the nanofluid including the functionalized molybdenum disulfide nanosheets can achieve a low oil / water interfacial tension and achieve a good oil displacement effect.

[0061] In one embodiment, the oil / water interfacial tension of the nanofluid is 10 -3 ~10 -2Specifically, the concentration of functionalized molybdenum disulfide nanosheets in the nanofluid can be controlled so that the oil / water interfacial tension of the nanofluid is within the above range, thereby enabling the nanofluid to have a higher recovery rate.

[0062] In one embodiment, the nanofluid further comprises either brine or deionized water; the brine concentration is 10,000 to 220,000 mg / L. When the brine concentration is within this range, it does not adversely affect the oxirane groups in the functionalized molybdenum disulfide nanosheets, thereby enhancing their hydrophilicity. This allows the hydrophilic oxirane groups and hydrophobic alkylamine chains to work together more effectively, resulting in improved stability of the nanofluid comprising the functionalized molybdenum disulfide nanosheets. The brine in the present invention also comprises produced water from the reservoir, further reducing water consumption costs.

[0063] The present invention does not impose any specific restrictions on the type of salt in the brine. For example, the salt may be selected from at least one of sodium chloride, calcium chloride, magnesium chloride, sodium sulfate, and sodium bicarbonate. When the salt is selected from two or more of the aforementioned compounds, the present invention does not impose any specific restrictions on the ratio of the specific compounds.

[0064] A fourth aspect of the present invention provides a displacement method for oil reservoir recovery using the nanofluid of the third aspect. The nanofluid used in this displacement method comprises functionalized molybdenum disulfide nanosheets, the surfaces of which are bonded with hydrophilic ethylene oxide groups and hydrophobic alkylamine chains. The nanosheets interact synergistically with each other, interacting with water and oil, respectively, to reduce interfacial tension between the two, thereby increasing oil recovery. The nanofluid's flaky structure also helps achieve higher recovery rates and greater stability in low-permeability reservoirs. Furthermore, the nanofluid can utilize seawater near the reservoir or produced water from the reservoir, reducing costs.

[0065] Specifically, the nanofluid of the third aspect is continuously or alternately injected into the oil reservoir to reduce the interfacial tension between the oil reservoir and water, improve the oil displacement efficiency, and further increase the recovery rate to achieve oil reservoir exploitation.

[0066] Hereinafter, the nanofluid including the functionalized molybdenum disulfide nanosheets of the present invention will be described in detail through specific examples.

[0067] Example 1

[0068] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-5-tallowamine for 2 hours to obtain a mixture, wherein the PEG-5-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0069] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0070] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0071] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, mixing, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0072] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0073] Example 2

[0074] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-10-tallowamine for 2 hours to obtain a mixture, wherein the PEG-10-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0075] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0076] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0077] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0078] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0079] Example 3

[0080] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-tallowamine for 2 hours to obtain a mixture, wherein the PEG-15-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0081] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0082] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0083] 4) 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product were added to the above brine and ultrasonicated for 4 hours and then stirred for 24 hours. After drying at 80°C, functionalized molybdenum disulfide nanosheets of this embodiment were obtained, wherein the molybdenum disulfide nanosheets had a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm. The molybdenum disulfide nanosheets were subjected to SEM testing, and the test results were as follows: Figure 1 As shown;

[0084] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0085] Example 4

[0086] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-coconut amine for 2 hours to obtain a mixture, wherein the PEG-15-coconut amine contains an ethylene oxide group and an alkylamine chain. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0087] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0088] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0089] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0090] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0091] Example 5

[0092] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-tallowamine for 2 hours to obtain a mixture, wherein the PEG-15-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0093] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0094] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0095] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0096] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 2000 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0097] Example 6

[0098] 1) mixing ethanol, 1 part by weight of lipoic acid, and 8 parts by weight of PEG-15-tallowamine for 4 hours to obtain a mixture, wherein the PEG-15-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0099] 2) adding 0.08 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 48 hours, and drying at 80° C. to obtain an intermediate product;

[0100] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0101] 4) adding 8 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 6 hours, stirring for 36 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0102] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, with the concentration of the functionalized molybdenum disulfide nanosheets being 500 ppm, and then subjected to ultrasonic treatment for 6 h and magnetic stirring for 36 h to obtain the nanofluid of this embodiment.

[0103] Example 7

[0104] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-tallowamine for 2 hours to obtain a mixture, wherein the PEG-15-tallowamine contains an ethylene oxide group and an alkylamine chain. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0105] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0106] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, to obtain brine with concentrations of 39186 mg / L and 300000 mg / L, respectively;

[0107] 4) adding 10 parts by weight of the molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the 39186 mg / L saline solution, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain the functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0108] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with brine, wherein the brine concentration was 300,000 mg / L and the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0109] Example 8

[0110] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-tallowamine for 2 hours to obtain a mixture, wherein the PEG-15-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0111] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0112] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0113] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to a flask, heating in a water bath at 80° C. for 24 h, and drying at 80° C. after the reaction is complete to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0114] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this embodiment.

[0115] Comparative Example 1

[0116] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of octadecylamine for 2 hours to obtain a mixture, wherein the octadecylamine contains an alkylamine chain. Specifically, the number of carbon atoms in the alkylamine chain is shown in Table 2;

[0117] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0118] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0119] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this comparative example, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0120] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this comparative example.

[0121] Comparative Example 2

[0122] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-22-tallowamine for 2 hours to obtain a mixture, wherein the PEG-22-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0123] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0124] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0125] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this comparative example, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0126] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this comparative example.

[0127] Comparative Example 3

[0128] 1) mixing ethanol, 1 part by weight of lipoic acid, and 5 parts by weight of PEG-15-octylamine for 2 hours to obtain a mixture, wherein the PEG-15-octylamine contains an ethylene oxide group and an alkylamine chain. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0129] 2) adding 0.1 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 24 hours, and drying at 80° C. to obtain an intermediate product;

[0130] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0131] 4) adding 10 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 4 hours, stirring for 24 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this comparative example, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0132] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 4 h and magnetically stirred for 24 h to obtain the nanofluid of this comparative example.

[0133] Comparative Example 4

[0134] 1) mixing ethanol, 1 part by weight of lipoic acid, and 3 parts by weight of PEG-15-tallowamine for 1 hour to obtain a mixture, wherein the PEG-15-tallowamine contains ethylene oxide groups and alkylamine chains. Specifically, the number of carbon atoms in the alkylamine chain and the number of ethylene oxide groups are shown in Table 2;

[0135] 2) adding 0.01 parts by weight of 1-hydroxybenzotriazole to the above mixture, stirring under magnetic stirring for 12 hours, and drying at 80° C. to obtain an intermediate product;

[0136] 3) preparing a mixed aqueous solution of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate, wherein the mass ratio of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate, and sodium sulfate is 500:99:8:14:1, and the brine concentration is 39186 mg / L;

[0137] 4) adding 15 parts by weight of molybdenum disulfide nanosheets and 1 part by weight of the intermediate product to the brine, ultrasonicating for 2 hours, stirring for 12 hours, and drying at 80° C. to obtain functionalized molybdenum disulfide nanosheets of this embodiment, wherein the molybdenum disulfide nanosheets have a layer thickness of 1.2 nm, a length of 80 nm, and a width of 60 nm;

[0138] 5) The functionalized molybdenum disulfide nanosheets prepared above were mixed with the above brine, wherein the concentration of the functionalized molybdenum disulfide nanosheets was 500 ppm, and then treated under ultrasound for 2 h and magnetically stirred for 12 h to obtain the nanofluid of this embodiment.

[0139] Test example

[0140] 1. The above Example 3 was subjected to SEM and FTIR tests. The test results are as follows: Figure 1-3 shown.

[0141] Figure 1 and Figure 2 They are SEM images of the molybdenum disulfide nanosheets and functionalized molybdenum disulfide nanosheets in Example 3, respectively. Figure 1 and Figure 2 It can be seen that the structure of the functionalized MoS2 nanosheets is consistent with that of the unfunctionalized MoS2 nanosheets and no obvious changes have occurred. Figure 3 This is the FTIR spectrum of the functionalized molybdenum disulfide nanosheets prepared in Example 3. Figure 3 It can be seen that at 3700~3000cm -1 The broad band between 1632 cm and 1632 cm is caused by the stretching of the intermolecular and intramolecular hydrogen bonds OH. -1 , 920cm -1 、620cm -1 and 460cm -1 The absorption peak at 1432 cm is caused by molybdenum disulfide. -1 The absorption peak at 1096 cm is caused by the CN stretching of the amide group. -1 The absorption peak at is caused by CO, which shows that the functionalized MoS2 nanosheets were successfully synthesized.

[0142] 2. Stability test

[0143] The nanofluids prepared in Example 3 and Comparative Example 1 were tested using a stability analyzer (λ=880 nm), and the stability of the nanofluids was evaluated using the stability kinetic index (TSI). The higher the TSI value, the more unstable the nanofluid. The test results are as follows: Figure 4 shown.

[0144] Figure 4 The stability curves of the nanofluids prepared in Example 3 and Comparative Example 1 are shown in FIG. Figure 4 It can be seen that the TSI value of the nanofluid of Example 3 is smaller than the TSI value of the nanofluid of Comparative Example 1, so the nanofluid of Example 3 has stronger stability.

[0145] 3. Interfacial tension test

[0146] The oil / water interfacial tension of the nanofluids prepared in Examples 1-3 and Comparative Example 1 was tested using a spinning drop interfacial tension meter at 30°C:

[0147] The crude oil and the above-mentioned nanofluid were mixed at 30°C using a spinning drop interfacial tension meter and measured to obtain the interfacial tension between the two phases as a function of time. The time was 2 h. If the measured value changed within the range of 1 to 2%, the measurement result was recorded. The measurement results are shown in Table 2.

[0148] Figure 5 is a graph showing the interfacial tension between the nanofluids and crude oil of Examples 1-3 and Comparative Example 1 changing with time, Figure 5 It can be seen that the interfacial tension of Example 3 is the smallest, reaching 0.006 mN / m, and the interfacial tension of Comparative Example 1 is the largest, which is 0.27 mN / m, proving that the functionalized molybdenum disulfide nanosheets of the present invention help reduce the interfacial tension between oil and water.

[0149] 4. Core flooding test

[0150] The nanofluids prepared in the above examples and comparative examples were subjected to core flooding tests. Sandstone cores were used as cores and the tests were conducted in an oil flooding device. The physical properties of the core samples are shown in Table 1.

[0151] Before starting the oil displacement test, the core was saturated with water for 24 hours. Then, oil with a viscosity of 100 cP was pumped into the core until no water flowed out. At this point, the core reached oil saturation, and the volume of crude oil pumped in when the core was saturated, V0, could be obtained. After oil saturation, water was injected at a rate of 0.3 mL / min until no oil was recovered. At this time, the volume of crude oil displaced by water was recorded as V1. Then, nanofluid was used for oil displacement. Nanofluid was injected into the core at a rate of 0.3 mL / min until the remaining oil was recovered. The volume of crude oil displaced by the nanofluid was measured as V2. The water recovery factor, nanofluid recovery factor, and total recovery factor can be calculated using Equations 1, 2, and 3, respectively:

[0152] Water flooding recovery rate (%) = V1 / V0 Formula 1

[0153] Nanofluid flooding recovery rate (%) = V2 / V0 Formula 2

[0154] Total recovery rate (%) = (V1 + V2) / V0 Formula 3

[0155] The test results are shown in Table 2.

[0156] Figure 6 The relationship between the volume of water and nanofluid injected into the core pores and the oil recovery rate in Examples 1-3 and Comparative Example 1 is shown.

[0157] Table 1

[0158]

[0159] Table 2

[0160]

[0161]

[0162] From Table 2 we can see that:

[0163] The nanofluids prepared in Examples 1-8 have lower oil / water interfacial tension than the nanofluids in Comparative Examples 1-4, with the lowest reaching 0.006 mN / m. The corresponding nanofluid flooding recovery rate can reach 25.53%, and the total recovery rate can reach 69.66%, effectively improving the recovery rate of low permeability oil reservoirs.

[0164] Figure 6 is the relationship between the nanofluid injection pore volume and oil recovery rate, Figure 6 It can be seen that the oil recovery rate of the core samples after water injection is about 44%. After the nanofluid prepared in Comparative Example 1 is injected, the oil recovery rate is 16.12%. After the nanofluid prepared in Example 1 is injected, the increase in oil recovery rate is not very obvious compared with Comparative Example 1. After the nanofluid prepared in Example 2 and Example 3 is injected, the oil recovery rate is improved to varying degrees compared with Comparative Example 1, and the maximum increase can be 25.53%. This is due to the low oil / water interfacial tension of the nanofluids in Example 2 and Example 3, which enables efficient recovery of low permeability oil reservoirs.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing functionalized molybdenum disulfide nanosheets, characterized in that: The following steps are involved: 1) mixing a solvent, 1 part by weight of lipoic acid, and 5 to 10 parts by weight of a first compound for 2 to 4 hours to obtain a mixture; 2) adding 0.05 to 0.1 parts by weight of 1-hydroxybenzotriazole to the mixture, mixing for 24 to 48 hours, and drying to obtain an intermediate product; 3) ultrasonically treating or thermally treating the raw material-solution system to obtain functionalized nanosheets; The raw material-solution system comprises 5 to 10 parts by weight of molybdenum disulfide nanosheets, 1 part by weight of the intermediate product and salt water; The first compound contains an ethylene oxide group and an alkylamine chain; The number of carbon atoms in the alkylamine chain of the first compound is 12 to 18, and the number of ethylene oxide groups is 2 to 15.

2. The method for preparing functionalized molybdenum disulfide nanosheets according to claim 1, wherein: In step 3), the ultrasonic treatment comprises ultrasonicating the raw material-solution system for 4 to 12 hours and then stirring for 24 to 48 hours; The heat treatment comprises reacting the raw material-solution system at 60-80° C. for 24-48 hours.

3. The method for preparing functionalized molybdenum disulfide nanosheets according to claim 1 or 2, wherein: The molybdenum disulfide nanosheet has a layer thickness of 1 to 1.5 nm, a length of 50 to 100 nm, and a width of 50 to 100 nm.

4. The method for preparing functionalized molybdenum disulfide nanosheets according to any one of claims 1 to 3, characterized in that: The first compound includes at least one of tallow amine polyoxyethylene ether compounds, octadecylamine polyoxyethylene ether compounds, and coconut oil amine polyoxyethylene ether compounds.

5. A functionalized molybdenum disulfide nanosheet, characterized in that: The functionalized molybdenum disulfide nanosheets are prepared by the preparation method of any one of claims 1 to 4.

6. A nanofluid, characterized in that: The method comprises the functionalized molybdenum disulfide nanosheet prepared according to any one of claims 1 to 4 or the functionalized molybdenum disulfide nanosheet according to claim 5.

7. The nanofluid according to claim 6, characterized in that The concentration of the functionalized molybdenum disulfide nanosheets is 10 to 1000 ppm.

8. The nanofluid according to claim 6 or 7, characterized in that: The oil / water interfacial tension of the nanofluid is 10 -3 ~10 -2 mN / m.

9. The nanofluid according to any one of claims 6 to 8, characterized in that: The nanofluid also includes one of salt water and deionized water; The concentration of the brine is 10,000 to 220,000 mg / L.

10. A displacement method, characterized in that: The nanofluid according to any one of claims 6 to 9 is used to recover oil from a reservoir.

Images