Biomass carbon / metal oxide nanoparticle and preparation method thereof, carbon-based nanomaterial emulsifier and application thereof

Abstract

This invention provides biomass carbon / metal oxide nanoparticles and their preparation method, as well as carbon-based nanomaterial emulsifiers and their applications. The preparation method of the biomass carbon / metal oxide nanoparticles includes: sequentially drying, carbonizing, and pulverizing biomass loaded with metal oxide precursors. The biomass carbon / metal oxide nanoparticles of this invention have strong emulsifying properties, low raw material costs, require no surface modification, have a simple preparation process, are highly practical, and are easy to promote and use. The carbon-based nanomaterial emulsifier containing biomass carbon / metal oxide nanoparticles can enhance the emulsifying ability of nanocomposite oil displacement systems, achieve efficient oil washing and emulsification diffusion, and solve the problem of poor emulsification and oil displacement effect in composite oil displacement systems under alkali-free conditions. This is of great significance for the efficient development of medium- and low-permeability reservoirs.

Description

Technical Field

[0001] This invention relates to the field of petroleum development technology, specifically to the field of enhanced oil recovery technology, and particularly to biomass carbon / metal oxide nanoparticles and their preparation methods, carbon-based nanomaterial emulsifiers and their applications. Background Technology

[0002] In most of my country's oilfields, the crude oil recovery rate after water injection development is generally no more than 40%, leaving a large portion of crude oil undeveloped and remaining in the formation. To further improve crude oil recovery and achieve increased and stable production in older oilfields, chemical flooding technology has been widely applied in my country and has achieved good industrial application results. Nanomaterials, by adsorbing at the oil-water interface, improve the viscoelasticity and stability of the oil displacement system and can also form stable emulsions, which is beneficial for improving crude oil recovery.

[0003] CN113248669B discloses a method for preparing amphiphilic graphene-based oil displacement materials, belonging to the field of oilfield chemical technology. It utilizes an interfacial reaction method to asymmetrically modify nano-graphene oxide to prepare Janus amphiphilic nano-graphene materials. Specifically, the hydrophobic side modification is achieved through the reaction of long-chain organic amines with the epoxy groups on the surface of graphene oxide, while the hydrophilic side modification is achieved through a grafting reaction on the surface of graphene oxide using cerium salt as an initiator and a compound containing polyoxyethylene segments as a monomer. This nano-graphene oil displacement material has advantages such as easy dispersion, good salt and temperature resistance, excellent long-term dispersion stability, small dosage, and good oil displacement effect, and can be used as an oil displacement agent in high-temperature and high-salinity oil reservoirs.

[0004] CN112980415B discloses a multi-grafted-site nano-carbon material, an active nano-carbon material, their preparation methods, and an oil displacement system for ultra-low permeability reservoirs. Under the action of a catalyst, the multi-grafted-site nano-carbon material is contacted with an activator to undergo an activation reaction, thereby obtaining the active nano-carbon material. Applying the surface-modified active nano-carbon to the oil displacement system for ultra-low permeability reservoirs can give the system high interfacial activity, reducing the oil-water interfacial tension by up to 10%. - 2 It is on the order of mN / m and can significantly improve the efficiency of oil washing.

[0005] However, the carbon nanoparticles used in the above-mentioned existing technologies all involve surface modification and have complex preparation processes. Therefore, it is necessary to develop biomass carbon / metal oxide nanoparticles and their preparation methods, as well as carbon-based nanomaterial emulsifiers and their applications. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides biomass carbon / metal oxide nanoparticles and their preparation method, carbon-based nanomaterial emulsifiers and their applications. The preparation method of the biomass carbon / metal oxide nanoparticles includes: sequentially drying, carbonizing and pulverizing biomass loaded with metal oxide precursors. The biomass carbon / metal oxide nanoparticles of the present invention have strong emulsifying properties, low raw material cost, no need for surface modification, simple preparation process, strong practicality, and are easy to promote and use. The carbon-based nanomaterial emulsifier containing biomass carbon / metal oxide nanoparticles can enhance the emulsification ability of nanocomposite oil displacement systems, achieve efficient oil washing and emulsification expansion, and solve the problem of poor emulsification and oil displacement effect of composite oil displacement systems under alkali-free conditions. It is of great significance for the efficient development of medium and low permeability reservoirs.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] One objective of this invention is to provide a method for preparing biomass carbon / metal oxide nanoparticles, the method comprising the following steps:

[0009] Biomass was soaked in an aqueous solution of metal oxide precursors, and then removed and subjected to drying, carbonization and pulverization processes in sequence to obtain biomass carbon / metal oxide nanoparticles.

[0010] The preparation method of the present invention involves sequentially drying, carbonizing, and pulverizing biomass loaded with metal oxide precursors to obtain biomass carbon / metal oxide nanoparticles. The prepared biomass carbon / metal oxide nanoparticles have strong emulsifying properties, use biomass as the carbon source, have low raw material costs, do not require surface modification, have a simple preparation process, are highly practical, and are easy to promote and use.

[0011] As a preferred technical solution of the present invention, the biomass includes any one or a combination of at least two of straw, fruit shells or bamboo.

[0012] Preferably, the metal oxide precursor is a soluble metal salt.

[0013] Preferably, the metal ions of the soluble metal salt include Zn. 2+ Fe 3+ Ca 2+ Mg 2+ Co 2+ Ni 2+ Cu 2+ or Mn 2+ Any one or a combination of at least two of the above, wherein the anion of the soluble metal salt includes Cl. - ,Br - NO3- or CH3COO - Any one or at least two of them.

[0014] Preferably, the concentration of the aqueous solution of the metal oxide precursor is 1-20 wt%, such as 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%, 16 wt%, 18 wt%, or 20 wt%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] As a preferred technical solution of the present invention, the biomass is washed before soaking;

[0016] Preferably, the washing process includes washing the biomass in ethanol and water 2-5 times in sequence.

[0017] As a preferred technical solution of the present invention, the soaking time is 10-15h, such as 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h or 15h, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] Preferably, the drying temperature is 80-120℃, such as 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] Preferably, the drying time is 4-24h, such as 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] As a preferred embodiment of the present invention, the carbonization process is carried out in a muffle furnace.

[0021] Preferably, the carbonization process is carried out under a nitrogen protective atmosphere.

[0022] Preferably, the heating rate of the carbonization process is 5-20℃ / min, such as 5℃ / min, 7℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 13℃ / min, 15℃ / min, 17℃ / min, 18℃ / min or 20℃ / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] Preferably, the carbonization temperature is 600-900℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] Preferably, the temperature holding time for the carbonization treatment is 1-10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] As a preferred embodiment of the present invention, the pulverization process is mechanical pulverization.

[0026] Preferably, the mechanical pulverization includes any one of ball milling, disc milling, or air milling.

[0027] As a preferred technical solution of the present invention, the preparation method includes the following:

[0028] Biomass is washed 2-5 times in ethanol and water respectively, then soaked in a 1-20 wt% aqueous solution of metal oxide precursor for 10-15 h. After that, it is taken out and dried in an oven at 80-120 ℃ for 4-24 h. The dried product is then placed in a muffle furnace for carbonization under a nitrogen protective atmosphere. The heating rate of the carbonization process is controlled at 5-20 ℃ / min, the temperature is 600-900 ℃, and the temperature holding time is 1-10 h. After cooling to room temperature, the carbonized product is pulverized to obtain biomass carbon / metal oxide nanoparticles.

[0029] The biomass includes any one or a combination of at least two of straw, fruit shells, or bamboo; the metal oxide precursor is a soluble metal salt; and the metal ion of the soluble metal salt includes Zn. 2+ Fe 3+ Ca 2+ Mg 2+ Co 2+ Ni 2+ Cu 2+ or Mn 2+ Any one or a combination of at least two of the above, wherein the anion of the soluble metal salt includes Cl. - ,Br - NO3 - or CH3COO - The pulverization process is any one or a combination of at least two of the following: mechanical pulverization; the mechanical pulverization includes any one of ball milling, disc milling, or air milling.

[0030] A second objective of this invention is to provide biomass carbon / metal oxide nanoparticles, prepared using the preparation method described in one objective.

[0031] Preferably, the mass ratio of biomass carbon to metal oxide in the biomass carbon / metal oxide nanoparticles is 1:(5-6), such as 1:5, 1:51, 1:52, 1:53, 1:54, 1:55, 1:56, 1:57, 1:58, 1:59 or 1:6, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the particle size of the biomass carbon / metal oxide nanoparticles is 0.05-5 μm, such as 0.05 μm, 0.1 μm, 0.15 μm, 0.25 μm, 0.35 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.75 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0033] It is worth noting that the morphology of the biomass carbon / metal oxide nanoparticles described in this invention is an irregular, approximately spherical shape; the particle size of the biomass carbon / metal oxide nanoparticles described in this invention can be controlled by the type, concentration, and reaction ratio of metal ions.

[0034] The biomass carbon / metal oxide nanoparticles described in this invention can be adsorbed onto the oil-water interface through interactions such as hydrogen bonds and π-π bonds, forming a three-dimensional barrier at the oil-water interface, which hinders the aggregation of crude oil droplets, thereby stabilizing the emulsion. Furthermore, the emulsification and thickening effects are significant, and it has broad application prospects in improving crude oil recovery.

[0035] The third objective of this invention is to provide a carbon-based nanomaterial emulsifier, wherein the dispersion prepared by mixing the biomass carbon / metal oxide nanoparticles described in the second objective with water is the carbon-based nanomaterial emulsifier.

[0036] Preferably, the mass percentage of biomass carbon / metal oxide nanoparticles in the carbon-based nanomaterial emulsifier is 0.001-0.05 wt%, such as 0.001 wt%, 0.003 wt%, 0.005 wt%, 0.007 wt%, 0.009 wt%, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, or 0.05 wt%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] The carbon-based nanomaterial emulsifier of this invention can significantly improve the stability and viscosity of emulsions by introducing biomass carbon / metal oxide nanoparticles.

[0038] The fourth objective of this invention is to provide an application of a carbon-based nanomaterial emulsifier, specifically applying the carbon-based nanomaterial emulsifier described in the third objective to an oil displacement system for medium- and low-permeability reservoirs.

[0039] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0040] (1) The preparation method of biomass carbon / metal oxide nanoparticles described in this invention uses biomass as the carbon source, which has low raw material cost and does not require surface modification. The preparation process is simple, practical, and easy to promote and use.

[0041] (2) The biomass carbon / metal oxide nanoparticles described in this invention can be adsorbed onto the oil-water interface through hydrogen bonds, π-π bonds and other interactions with crude oil, forming a three-dimensional barrier at the oil-water interface, which hinders the aggregation of crude oil droplets, thereby stabilizing the emulsion. Moreover, the emulsification and thickening effect is obvious, and it has a relatively broad application prospect in improving crude oil recovery.

[0042] (3) The carbon-based nanomaterial emulsifier of the present invention can significantly improve the stability and viscosity of the emulsion by introducing biomass carbon / metal oxide nanoparticles, which can enhance the emulsification ability of the nanocomposite oil displacement system, achieve efficient oil washing and emulsification expansion, solve the problem of poor emulsification and oil displacement effect of composite oil displacement system under alkali-free conditions, and is of great significance for the efficient development of medium and low permeability reservoirs. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the biomass carbon / zinc oxide nanoparticles obtained in Example 1;

[0044] Figure 2 This is the EDS spectrum of the biomass carbon / zinc oxide nanoparticles obtained in Example 1;

[0045] Figure 3 This is a scanning electron microscope image of the biomass carbon / copper oxide nanoparticles obtained in Example 2;

[0046] Figure 4 This is the EDS spectrum of the biomass carbon / copper oxide nanoparticles obtained in Example 2;

[0047] Figure 5 This is a scanning electron microscope image of the biomass carbon / iron oxide nanoparticles obtained in Example 3;

[0048] Figure 6 This is the EDS energy spectrum of the biomass carbon / iron oxide nanoparticles obtained in Example 3. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0050] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0051] Example 1

[0052] This embodiment provides a method for preparing biomass carbon / zinc oxide nanoparticles, the preparation method including the following:

[0053] Wheat straw was selected as the biomass. 5g of biomass was washed twice, once in 100mL of ethanol and once in 100mL of deionized water. Then, it was soaked in 100mL of 1wt% zinc acetate aqueous solution for 12h. After that, it was taken out and dried in an oven at 80℃ for 5h. The dried product was then placed in a muffle furnace for carbonization under a nitrogen protective atmosphere. The heating rate of the carbonization process was controlled at 5℃ / min, the temperature was 600℃, and the temperature holding time was 2h. After cooling to room temperature, the carbonized product was pulverized, including placing the carbonized product in a planetary ball mill and ball milling it at 400rpm for 12h to obtain biomass carbon / zinc oxide nanoparticles.

[0054] In this embodiment, the mass ratio of biomass carbon to zinc oxide in the biomass carbon / zinc oxide nanoparticles is 1:(5-6), and the particle size of the biomass carbon / zinc oxide nanoparticles is 0.5-2 μm. The scanning electron microscope image of the biomass carbon / zinc oxide nanoparticles obtained in this embodiment is shown below. Figure 1 As shown, the nanoparticles are irregularly shaped and approximately spherical; the EDS spectrum of the biomass carbon / zinc oxide nanoparticles obtained in this embodiment is shown below. Figure 2 As shown, the nanoparticles are mainly composed of C, O, and Zn, further proving that the nanomaterial is a biomass carbon / zinc oxide nanoparticle.

[0055] Example 2

[0056] This embodiment provides a method for preparing biomass carbon / copper oxide nanoparticles, the preparation method including the following:

[0057] Fruit shells were selected as biomass. 5g of biomass was washed twice, once in 100mL of ethanol and once in 100mL of deionized water. Then, it was soaked in 100mL of 15wt% copper nitrate aqueous solution for 12h. After that, it was taken out and dried in an oven at 90℃ for 6h. The dried product was then placed in a muffle furnace for carbonization under a nitrogen protective atmosphere. The heating rate of the carbonization process was controlled at 5℃ / min, the temperature was 800℃, and the temperature was held for 4h. After cooling to room temperature, the carbonized product was pulverized, including grinding it in a disc mill at 600rpm for 1h to obtain biomass carbon / copper oxide nanoparticles.

[0058] In this embodiment, the mass ratio of biomass carbon to copper oxide in the biomass carbon / copper oxide nanoparticles is 1:(5-6), and the particle size of the biomass carbon / copper oxide nanoparticles is 0.5-2 μm. The scanning electron microscope image of the biomass carbon / copper oxide nanoparticles obtained in this embodiment is shown below. Figure 3 As shown, the nanoparticles are irregularly shaped and approximately spherical; the EDS spectrum of the biomass carbon / copper oxide nanoparticles obtained in this embodiment is shown below. Figure 4 As shown, the nanoparticles are mainly composed of C, O, and Cu, further proving that the nanomaterial is a biomass carbon / copper oxide nanoparticle.

[0059] Example 3

[0060] This embodiment provides a method for preparing biomass carbon / iron oxide nanoparticles, the preparation method including the following:

[0061] Bamboo was selected as the biomass. 5g of biomass was washed twice, once in 100mL of ethanol and once in 100mL of deionized water. Then, it was soaked in 100mL of 20wt% ferric chloride aqueous solution for 12h. After that, it was taken out and dried in an oven at 80℃ for 5h. The dried product was then placed in a muffle furnace for carbonization under a nitrogen protective atmosphere. The heating rate of the carbonization process was controlled at 5℃ / min, the temperature was 700℃, and the temperature holding time was 2h. After cooling to room temperature, the carbonized product was pulverized, including placing the carbonized product in a planetary ball mill and ball milling it at 400rpm for 12h to obtain biomass carbon / iron oxide nanoparticles.

[0062] In this embodiment, the mass ratio of biomass carbon to iron oxide in the biomass carbon / iron oxide nanoparticles is 1:(5-6), and the particle size of the biomass carbon / iron oxide nanoparticles is 0.2-2 μm. The scanning electron microscope image of the biomass carbon / iron oxide nanoparticles obtained in this embodiment is shown below. Figure 5As shown, the nanoparticles are irregularly shaped and approximately spherical; the EDS spectrum of the biomass carbon / iron oxide nanoparticles obtained in this embodiment is shown below. Figure 6 As shown, the nanoparticles are mainly composed of C, O, and Fe, further proving that the nanomaterial is a biomass carbon / iron oxide nanoparticle.

[0063] Comparative Example 1

[0064] This comparative example provides a method for preparing biomass carbon nanoparticles, the method comprising the following steps:

[0065] Wheat straw was selected as biomass. 5g of biomass was washed twice, once in 100mL of ethanol and once in 100mL of deionized water. The product was then dried in an oven at 80℃ for 5h. The dried product was then carbonized in a muffle furnace under a nitrogen atmosphere. The heating rate of the carbonization process was controlled at 5℃ / min, the temperature was 600℃, and the temperature was held for 2h. After cooling to room temperature, the carbonized product was pulverized, including being ball-milled in a planetary ball mill at 400rpm for 12h to obtain biomass carbon nanoparticles.

[0066] In other words, compared to Example 1, the difference in this comparative example is that the aqueous solution of the metal oxide precursor was omitted, and the resulting nanoparticles do not contain metal oxides.

[0067] Characterization Example 1

[0068] The dispersion prepared by combining the biomass carbon / zinc oxide nanoparticles obtained in Example 1 with formation water is a carbon-based nanomaterial emulsifier. The mass percentage of biomass carbon / metal oxide nanoparticles in the carbon-based nanomaterial emulsifier is 0.008 wt%. The viscosity and stability of the emulsion formed by the obtained carbon-based nanomaterial emulsifier and crude oil were tested.

[0069] The crude oil used in this characterization example was Xinjiang oil-water emulsion, and the test temperature was 78℃. Carbon-based nanomaterial emulsifier and crude oil were placed in beakers at water-to-oil volume ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1, respectively. The mixture was kept at 78℃ for 1 hour, then dispersed using an IKA homogenizer for 1 minute. The emulsification was observed visually to determine if phase separation had occurred. The relevant results are shown in Table 1. It can be seen that when the water-to-oil volume ratio is 6:4 or lower, the crude oil can emulsify to form a stable water-in-oil emulsion, with a maximum water content of 60%.

[0070] Characterization Example 2

[0071] The dispersion prepared by combining the biomass carbon / copper oxide nanoparticles obtained in Example 2 with formation water is a carbon-based nanomaterial emulsifier. The mass percentage of biomass carbon / metal oxide nanoparticles in the carbon-based nanomaterial emulsifier is 0.005 wt%. The viscosity and stability of the emulsion formed by the obtained carbon-based nanomaterial emulsifier and crude oil were tested.

[0072] The crude oil used in this characterization example was Jilin oil-water emulsion, and the test temperature was 66℃. Carbon-based nanomaterial emulsifier and crude oil were placed in beakers at water-to-oil volume ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1, respectively. The mixture was kept at 66℃ for 1 hour, then dispersed using an IKA homogenizer for 1 minute. The emulsification was observed visually to determine if phase separation had occurred. The relevant results are shown in Table 1. It can be seen that when the water-to-oil volume ratio is 6:4 or lower, the crude oil can emulsify to form a stable water-in-oil emulsion, with a maximum water content of 60%.

[0073] Characterization Example 3

[0074] The dispersion prepared by combining the biomass carbon / iron oxide nanoparticles obtained in Example 3 with formation water is a carbon-based nanomaterial emulsifier. The mass percentage of biomass carbon / metal oxide nanoparticles in the carbon-based nanomaterial emulsifier is 0.01 wt%. The viscosity and stability of the emulsion formed by the obtained carbon-based nanomaterial emulsifier and crude oil were tested.

[0075] The crude oil used in this characterization example was Changqing oil-water emulsion, and the test temperature was 88℃. Carbon-based nanomaterial emulsifier and crude oil were placed in beakers at water-to-oil volume ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1, respectively. The mixtures were kept at 88℃ for 1 hour, then dispersed using an IKA homogenizer for 1 minute. The emulsification was observed visually to determine if phase separation had occurred. The relevant results are shown in Table 1. It can be seen that when the water-to-oil volume ratio is 7:3 or lower, the crude oil can emulsify to form a stable water-in-oil emulsion, with a maximum water content of up to 70%.

[0076] Comparative Characterization Example 1

[0077] The dispersion prepared by combining the biomass carbon nanoparticles obtained in Comparative Example 1 with formation water is a carbon-based nanomaterial emulsifier. The mass percentage of biomass carbon nanoparticles in the carbon-based nanomaterial emulsifier is 0.008 wt%. The viscosity and stability of the emulsion formed by the obtained carbon-based nanomaterial emulsifier and crude oil were tested.

[0078] The crude oil used in this characterization example was Xinjiang oil-water emulsion, and the test temperature was 78℃. Carbon-based nanomaterial emulsifier and crude oil were placed in beakers at water-to-oil volume ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1, respectively, and kept at 78℃ for 1 hour. Afterward, the mixture was dispersed using an IKA homogenizer for 1 minute, and the emulsification was observed visually to determine if phase separation had occurred. The relevant results are shown in Table 1. It can be seen that the pure biomass carbon nanoparticles themselves have weak emulsifying ability and cannot form stable emulsions at high water content.

[0079] Table 1

[0080]

[0081]

[0082] In summary, this invention provides biomass carbon / metal oxide nanoparticles and their preparation method, as well as carbon-based nanomaterial emulsifiers and their applications. The preparation method of the biomass carbon / metal oxide nanoparticles includes: sequentially drying, carbonizing, and pulverizing biomass loaded with metal oxide precursors. The biomass carbon / metal oxide nanoparticles of this invention have strong emulsifying properties, low raw material costs, require no surface modification, have a simple preparation process, are highly practical, and are easy to promote and use. The carbon-based nanomaterial emulsifier containing biomass carbon / metal oxide nanoparticles can enhance the emulsifying ability of nanocomposite oil displacement systems, achieve efficient oil washing and emulsification diffusion, and solve the problem of poor emulsification and oil displacement effects in composite oil displacement systems under alkali-free conditions. This is of great significance for the efficient development of medium- and low-permeability reservoirs.

[0083] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0084] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0085] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0086] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A carbon-based nanomaterial emulsifier, characterized in that, The dispersion prepared by mixing biomass carbon / metal oxide nanoparticles with water is a carbon-based nanomaterial emulsifier. The biomass carbon / metal oxide nanoparticles were prepared by the following method, which includes the following steps: Biomass was soaked in an aqueous solution of metal oxide precursors, and then removed and subjected to drying, carbonization and pulverization processes in sequence to obtain biomass carbon / metal oxide nanoparticles. The biomass includes any one or a combination of at least two of straw, fruit shells or bamboo; The metal oxide precursor is a soluble metal salt; The metal ions of the soluble metal salt include Zn. 2+ Fe 3+ Ca 2+ Mg 2+ Co 2+ Ni 2+ Cu 2+ or Mn 2+ Any one or a combination of at least two of the above, wherein the anion of the soluble metal salt includes Cl. - ,Br - NO3 - or CH3COO - Any one or at least two of them; The carbonization process is carried out at a temperature of 600-900℃.

2. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The concentration of the aqueous solution of the metal oxide precursor is 1-20 wt%.

3. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The biomass is washed before soaking.

4. The carbon-based nanomaterial emulsifier according to claim 3, characterized in that, The washing process involves sequentially washing the biomass in ethanol and water 2-5 times each.

5. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The soaking time is 10-15 hours.

6. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The drying process is carried out in an oven.

7. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The drying temperature is 80-120℃.

8. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The drying process takes 4-24 hours.

9. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The carbonization process is carried out in a muffle furnace.

10. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The carbonization process is carried out under a nitrogen protective atmosphere.

11. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The heating rate of the carbonization process is 5-20℃ / min.

12. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The carbonization process is carried out at a temperature of 1-10 hours.

13. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The pulverization process is mechanical pulverization.

14. The carbon-based nanomaterial emulsifier according to claim 13, characterized in that, The mechanical pulverization includes any one of ball milling, disc milling, or air milling.

15. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The preparation method of the biomass carbon / metal oxide nanoparticles includes the following: Biomass is washed 2-5 times in ethanol and water respectively, then soaked in a 1-20 wt% aqueous solution of metal oxide precursor for 10-15 h. After that, it is taken out and dried in an oven at 80-120 ℃ for 4-24 h. The dried product is then placed in a muffle furnace for carbonization under a nitrogen protective atmosphere. The heating rate of the carbonization process is controlled at 5-20 ℃ / min, the temperature is 600-900 ℃, and the temperature is held for 1-10 h. After cooling to room temperature, the carbonized product is pulverized to obtain biomass carbon / metal oxide nanoparticles. The biomass includes any one or a combination of at least two of straw, fruit shells, or bamboo; the metal oxide precursor is a soluble metal salt; and the metal ion of the soluble metal salt includes Zn. 2+ Fe 3+ Ca 2+ Mg 2+ Co 2+ Ni 2+ Cu 2+ or Mn 2+ Any one or a combination of at least two of the above, wherein the anion of the soluble metal salt includes Cl. - ,Br - NO3 - or CH3COO - The pulverization process is any one or a combination of at least two of the following: mechanical pulverization; the mechanical pulverization includes any one of ball milling, disc milling, or air milling.

16. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The mass ratio of biomass carbon to metal oxide in the biomass carbon / metal oxide nanoparticles is 1:(5-6).

17. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The biomass carbon / metal oxide nanoparticles have a particle size of 0.05-5 μm.

18. The carbon-based nanomaterial emulsifier according to claim 1, characterized in that, The biomass carbon / metal oxide nanoparticles in the carbon-based nanomaterial emulsifier are 0.001-0.05 wt%.

19. The application of a carbon-based nanomaterial emulsifier, characterized in that, The carbon-based nanomaterial emulsifier according to any one of claims 1-18 is applied to an oil displacement system for medium-low permeability reservoirs.

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