Graphene surfactant, preparation method thereof, water drive system and application

Abstract

The invention belongs to the field of surfactants, and particularly discloses a graphene surfactant and a preparation method thereof. The preparation method comprises the following steps: preparing graphene oxide; the preparation method comprises the following steps: carrying out surface modification on graphene oxide by using a silane coupling agent to obtain surface-modified graphene oxide; and grafting an alkanolamide compound onto the graphene oxide subjected to surface modification, so as to obtain the graphene surfactant. The graphene surfactant prepared through the method has good surface activity and oil displacement capacity, the water injection pressure can be reduced, the water displacement effect can be improved, and after injected water is injected into a stratum, the problems that the injection pressure is high and the recovery rate is low generally existing in medium-low permeability reservoir water displacement can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of surfactants, and particularly relates to a graphene-based surfactant and a preparation method thereof, a water flooding system containing the graphene-based surfactant, the graphene-based surfactant, and the application of the water flooding system in oil production. Background Art

[0002] At present, in some oilfields, there are generally problems of high injection pressure and low recovery rate in water flooding of low-permeability reservoirs, which are mainly manifested in difficult oil production and easy water channeling. At the same time, there are no targeted chemical plugging removal, dredging, and production increase measures for medium and low-permeability water flooding, nor a series of independently developed chemical products. There is an urgent need to develop targeted chemical agents that can effectively reduce pressure and increase injection, improve the efficiency of oil washing and oil displacement, expand the scope of water injection coverage, and ultimately improve the water flooding effect.

[0003] Surfactants have been applied in the oil and gas industry for more than half a century. During this period, surfactants have been widely used as foaming agents, drainage aids, emulsifiers, demulsifiers, and defoaming agents, etc., and have been widely applied and developed in drilling engineering, wastewater treatment, and enhanced oil recovery. Surfactants can reduce the surface tension of the liquid phase. As its mass fraction increases, the surface tension first drops sharply, and when the mass fraction increases to a certain extent, the surface tension no longer changes.

[0004] Surfactants have a variety of properties, so the application of surfactants is also very extensive. Common surfactants are divided into anionic surfactants such as stearic acid and sodium dodecylbenzenesulfonate, cationic surfactants such as quaternary ammonium compounds, zwitterionic surfactants such as lecithin, amino acid type, and betaine type, and non-ionic surfactants such as fatty acid glycerides, sorbitan fatty acid esters, and polysorbates.

[0005] Graphene oxide itself has advantages such as small particle size, high operability, and rich oxygen-containing functional groups. By designing its modifying groups, functionalized graphene can be prepared, which can effectively improve oil recovery. In recent years, alkanolamide series surfactants have been widely studied, thanks to their good water hardness resistance, effective reduction of the oil-water interfacial tension, and applicability in a wide pH range, etc. They have good application prospects in oil exploitation. When such surfactants are grafted with graphene oxide to form functionalized graphene, they have excellent practical value. Carry out research on functionalized graphene modification technology, develop one or two kinds of functionalized graphene, clarify the grafted groups or small molecules, master the synthesis route and modification technology, so that it has good surface activity and oil displacement ability, can reduce the injection pressure of water injection, improve the water flooding effect, and solve the problems of high water flooding pressure and low recovery rate commonly existing in low-permeability reservoirs. At the same time, accumulate experience in graphene modification research, explore the application possibilities in anti-corrosion, heat insulation, and oil-water separation treatment, and lay a foundation for subsequent research. Summary of the Invention

[0006] The object of the present invention is to provide a graphene-based surfactant and a preparation method thereof, which can effectively solve the problems of high injection pressure and low recovery rate commonly existing in water flooding of medium and low permeability reservoirs.

[0007] According to the first aspect of the present invention, a preparation method of a graphene-based surfactant is provided, which comprises the following steps:

[0008] Prepare graphene oxide;

[0009] Surface-modify the graphene oxide with a silane coupling agent to obtain surface-modified graphene oxide;

[0010] Graft an alkanolamide compound onto the surface-modified graphene oxide to obtain a graphene-based surfactant.

[0011] According to an embodiment of the present invention, preparing graphene oxide includes:

[0012] Pre-oxidize graphene with potassium persulfate, phosphorus pentoxide, and concentrated sulfuric acid to obtain pre-oxidized graphene;

[0013] Completely oxidize the pre-oxidized graphene with concentrated sulfuric acid and sodium percarbonate to obtain graphene oxide.

[0014] According to an embodiment of the present invention, preparing graphene oxide includes: after completely oxidizing the pre-oxidized graphene with concentrated sulfuric acid and sodium percarbonate to obtain a completely oxidized pre-product, washing the completely oxidized pre-product to obtain graphene oxide.

[0015] According to an embodiment of the present invention, the washing process is carried out with hydrogen peroxide. According to an embodiment of the present invention, pre-oxidizing graphene with potassium persulfate, phosphorus pentoxide, and concentrated sulfuric acid to obtain pre-oxidized graphene includes:

[0016] Disperse graphene in water, control its concentration within the range of 1-5 mg / mL, and ultrasonicate for 0.5-1 hour to form a uniform graphene dispersion;

[0017] Dissolve concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate in a dissolution tank, add them to the graphene dispersion, and stir and react at 80-90 °C for 4-6 hours to obtain pre-oxidized graphene.

[0018] According to an embodiment of the present invention, the mass ratio of each substance added during the pre-oxidation process is: graphene: concentrated sulfuric acid: phosphorus pentoxide: potassium persulfate = 6-10: 0.3-0.4: 0.2-0.4: 1-2.

[0019] According to an embodiment of the present invention, pre-oxidized graphene is completely oxidized using concentrated sulfuric acid and sodium percarbonate to obtain graphene oxide, including:

[0020] Dissolve sodium percarbonate in water to prepare a sodium percarbonate solution;

[0021] Spray concentrated sulfuric acid and the sodium percarbonate solution onto the pre-oxidized graphene, and stir and react at 80 - 90 °C for 4 - 6 hours to obtain graphene oxide.

[0022] According to an embodiment of the present invention, during the complete oxidation process, the mass ratio of the substances added is: graphene: concentrated sulfuric acid: sodium percarbonate = 6 - 10: 0.2 - 0.3: 0.4 - 0.6.

[0023] According to an embodiment of the present invention, the silane coupling agent is vinyltriethoxysilane.

[0024] According to an embodiment of the present invention, the surface of graphene oxide is modified using a silane coupling agent to obtain surface-modified graphene oxide, including:

[0025] Mix vinyltriethoxysilane with water to prepare an aqueous solution of vinyltriethoxysilane;

[0026] Spray the aqueous solution of vinyltriethoxysilane onto the graphene oxide, and react at a temperature of 85 - 95 °C for 8 - 10 hours to obtain surface-modified graphene oxide.

[0027] According to an embodiment of the present invention, the mass ratio of graphene to vinyltriethoxysilane added is 6 - 10: 1 - 3.

[0028] According to an embodiment of the present invention, the alkanolamide compound is lauric acid diethanolamide.

[0029] According to an embodiment of the present invention, lauric acid diethanolamide is grafted onto the surface-modified graphene oxide to obtain a graphene-based surfactant, including:

[0030] Prepare a mixed solution of lauric acid diethanolamide by mixing lauric acid diethanolamide, water, and ethanol;

[0031] Spray the mixed solution of lauric acid diethanolamide onto the surface-modified graphene oxide, and stir at 50 - 60 °C for 4 - 6 h to obtain a graphene-based surfactant.

[0032] According to an embodiment of the present invention, when preparing the mixed solution of lauric acid diethanolamide, the mass ratio of lauric acid diethanolamide, water, and ethanol is 0.8 - 1: 0.8 - 1: 0.05 - 0.1.

[0033] According to an embodiment of the present invention, the mass ratio of graphene to diethanolamide laurate added is 6-10:60-70.

[0034] According to an embodiment of the present invention, the product obtained by grafting alkanolamide compounds onto surface-modified graphene oxide is dried and granulated to obtain the final granular graphene-based surfactant.

[0035] According to a second aspect of the present invention, there is provided a graphene-based surfactant prepared by the method according to the first aspect of the present invention.

[0036] According to a third aspect of the present invention, there is provided a water flooding system comprising the graphene-based surfactant according to the second aspect of the present invention.

[0037] According to a fourth aspect of the present invention, there is provided an application of the graphene-based surfactant according to the second aspect of the present invention in oil production.

[0038] According to a fifth aspect of the present invention, there is provided an application of the water flooding system according to the third aspect of the present invention in oil production.

[0039] Due to the above technical solutions, the present invention has the following beneficial effects compared with the prior art:

[0040] In the present invention, the silanol groups generated by the hydrolysis of the silane coupling agent react with the -OH on the surface of graphene oxide to form Si–O–C and Si–O–Si, and the amide of the alkanolamide compound generates free radicals to react with the amino group of the silane coupling agent to form an amide bond, thereby forming a functional graphene-based surfactant. This functional graphene-based surfactant has good surface activity and oil displacement ability, can reduce the injection pressure of water injection and improve the water flooding effect. After being injected into the formation with the injected water, it can effectively solve the problems of high injection pressure and low recovery rate commonly existing in water flooding of medium and low permeability reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 It is a flowchart of the preparation method of the graphene-based surfactant provided by the present invention;

[0043] Figure 2 It is a schematic diagram of the preparation route of graphene oxide provided by an embodiment of the present invention;

[0044] Figure 3 Schematic diagram of the preparation route of the graphene-based surfactant provided by an embodiment of the present invention. Detailed implementation manners

[0045] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] In order to solve the problems of high injection pressure and low recovery rate commonly existing in water flooding of medium and low permeability reservoirs mentioned in the background art, the present invention aims to provide a graphene-based surfactant and its preparation method.

[0047] According to the first aspect of the present invention, a preparation method of a graphene-based surfactant is provided. As Figure 1 shown, the preparation method includes the following steps: S1: Prepare graphene oxide; S2: Use a silane coupling agent to modify the surface of graphene oxide to obtain surface-modified graphene oxide;

[0048] S3: Graft an alkanolamide compound onto the surface-modified graphene oxide to obtain a graphene-based surfactant.

[0049] In the present invention, the silanol groups generated by hydrolysis of the silane coupling agent can react with -OH on the surface of graphene oxide to form Si–O–C and Si–O–Si, and the amide of the alkanolamide compound can generate free radicals to react with the amino group of the silane coupling agent to form an amide bond, thereby forming a functional graphene-based surfactant. This functional graphene-based surfactant has good surface activity and oil displacement ability, can reduce the injection pressure and improve the water flooding effect. After being injected into the formation with the injected water, it can effectively solve the problems of high injection pressure and low recovery rate commonly existing in water flooding of medium and low permeability reservoirs, and has significant economic and social benefits and broad application prospects.

[0050] Figure 2 Schematic diagram of the preparation route of graphene oxide provided by an embodiment of the present invention. As Figure 2 shown, the preparation of graphene oxide includes: S11: Pre-oxidize graphene using potassium persulfate, phosphorus pentoxide, and concentrated sulfuric acid to obtain pre-oxidized graphene; S12: Completely oxidize the pre-oxidized graphene using concentrated sulfuric acid and sodium percarbonate to obtain a graphene oxide pre-product; S13: Wash the graphene oxide pre-product to obtain graphene oxide.

[0051] The pre-oxidation process in step S11 can be carried out as follows: First, graphene is dispersed in water with its concentration controlled within the range of 1 - 5 mg / mL, and ultrasonic treatment is performed for 0.5 - 1 hour to form a uniform graphene dispersion; then, concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate are dissolved in a dissolution tank and added to the graphene dispersion, and stirring reaction is carried out at 80 - 90 °C for 4 - 6 hours to obtain pre-oxidized graphene. In this step, the mass ratio of the addition of each substance is: graphene: concentrated sulfuric acid: phosphorus pentoxide: potassium persulfate = 6 - 10: 0.3 - 0.4: 0.2 - 0.4: 1 - 2.

[0052] The complete oxidation process in step S12 can be carried out as follows: First, sodium percarbonate is dissolved in water to prepare a sodium percarbonate solution; then, concentrated sulfuric acid and the sodium percarbonate solution are sprayed into the pre-oxidized graphene, and stirring reaction is carried out at 80 - 90 °C for 4 - 6 hours to obtain oxidized graphene. In this step, the mass ratio of the addition of each substance is: graphene: concentrated sulfuric acid: sodium percarbonate = 6 - 10: 0.2 - 0.3: 0.4 - 0.6 (wherein, the graphene is based on the mass of the graphene before pre-oxidation).

[0053] The cleaning process in step S13 can be carried out using hydrogen peroxide. For example, hydrogen peroxide with a concentration of 28% is used for cleaning.

[0054] Figure 3 It is a schematic diagram of the preparation route of the graphene-based surfactant provided by an embodiment of the present invention. As shown in the figure, in this embodiment, in step S2, vinyltriethoxysilane is used to perform surface modification on the oxidized graphene to obtain surface-modified oxidized graphene, which specifically includes: mixing vinyltriethoxysilane with water to prepare a vinyltriethoxysilane aqueous solution; spraying the vinyltriethoxysilane aqueous solution into the oxidized graphene, and reacting at a temperature of 85 - 95 °C for 8 - 10 hours to obtain surface-modified oxidized graphene. The mass ratio of the addition of graphene to vinyltriethoxysilane is 6 - 10: 1 - 3 (wherein, the graphene is based on the mass of the graphene before pre-oxidation).

[0055] In this embodiment, in step S3, grafting lauric acid diethanolamide onto the surface-modified graphene oxide to obtain a graphene-based surfactant specifically includes: preparing a lauric acid diethanolamide mixed solution by mixing lauric acid diethanolamide, water, and ethanol; spraying the lauric acid diethanolamide mixed solution onto the surface-modified graphene oxide, and stirring at 50-60 °C for 4-6 h to obtain a graphene-based surfactant. Since the viscosity of the original lauric acid diethanolamide solution is relatively high, it needs to be diluted with water and ethanol during application. The mass ratio of lauric acid diethanolamide, water, and ethanol is (0.8-1):(0.8-1):(0.05-0.1). The mass ratio of graphene to lauric acid diethanolamide added is 6-10:60-70 (wherein, the graphene is calculated based on the mass of graphene before pre-oxidation).

[0056] According to a second aspect of the present invention, there is provided a graphene-based surfactant prepared by the method according to the first aspect of the present invention.

[0057] According to a third aspect of the present invention, there is provided a water flooding system comprising the graphene-based surfactant according to the second aspect of the present invention.

[0058] According to a fourth aspect of the present invention, there is provided an application of the graphene-based surfactant according to the second aspect of the present invention in oil production.

[0059] According to a fifth aspect of the present invention, there is provided an application of the water flooding system according to the third aspect of the present invention in oil production.

[0060] The present invention will be described in detail below through specific examples.

[0061] In the following examples, unless otherwise specified, various raw materials used are commercially available products. In the following examples, concentrated sulfuric acid is concentrated sulfuric acid with a mass fraction of 98%.

[0062] Example 1

[0063] Preparation of graphene oxide: Disperse graphene by high-speed stirring (3000 revolutions per minute) in water (70% of the total water volume required), and control its concentration within the range of 1 mg / mL. Ultrasonic for 0.5 hour to form a uniform graphene dispersion; dissolve concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate in a dissolution tank (the solution density is about 1.1), and then add it to the graphene dispersion. Stir and react at 80 °C for 4 hours to obtain pre-oxidized graphene; dissolve sodium percarbonate in water to prepare a sodium percarbonate solution; spray concentrated sulfuric acid and sodium percarbonate solution onto the pre-oxidized graphene, and stir and react at 80 °C for 4 hours to obtain a pre-product of graphene oxide; wash the pre-product of graphene oxide with hydrogen peroxide with a concentration of 28% to obtain graphene oxide.

[0064] Preparation of graphene-based surfactant: Mix vinyltriethoxysilane with water to prepare an aqueous solution of vinyltriethoxysilane; Spray the aqueous solution of vinyltriethoxysilane onto graphene oxide, and react at 85 °C for 8 hours to obtain surface-modified graphene oxide; Spray lauric acid diethanolamide onto the surface-modified graphene oxide, stir at 50 °C for 4 h, then dry the product in an oven and granulate it in a pulverizer to obtain the final granular graphene-grafted surfactant.

[0065] Feeding for producing 1000 parts of products

[0066]

[0067] Example 2

[0068] Preparation of graphene oxide: Disperse graphene in water (70% of the total water volume is required) by high-speed stirring (3000 revolutions per minute), control its concentration within the range of 3 mg / mL, and ultrasonicate for 1 hour to form a uniform graphene dispersion; After dissolving concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate in a dissolution tank (the solution density is about 1.1), add it to the graphene dispersion, and stir and react at 85 °C for 5 hours to obtain pre-oxidized graphene; Dissolve sodium percarbonate in water to prepare a sodium percarbonate solution; Spray concentrated sulfuric acid and sodium percarbonate solution onto the pre-oxidized graphene, and stir and react at 85 °C for 5 hours to obtain a pre-product of graphene oxide; Wash the pre-product of graphene oxide with 28% hydrogen peroxide to obtain graphene oxide.

[0069] Preparation of graphene-based surfactant: Mix vinyltriethoxysilane with water to prepare an aqueous solution of vinyltriethoxysilane; Spray the aqueous solution of vinyltriethoxysilane onto graphene oxide, and react at 90 °C for 9 hours to obtain surface-modified graphene oxide; Spray lauric acid diethanolamide onto the surface-modified graphene oxide, stir at 55 °C for 5 h, then dry the product in an oven and granulate it in a pulverizer to obtain the final granular graphene-grafted surfactant.

[0070] Feeding for producing 1000 parts of products

[0071]

[0072] Example 3

[0073] Preparation of graphene oxide: Graphene is dispersed in water (70% of the total water volume is required) by high-speed stirring (3000 revolutions per minute), and its concentration is controlled within the range of 5 mg / mL. After ultrasonic treatment for 1 hour, a uniform graphene dispersion is formed. After concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate are dissolved in a dissolution tank (the solution density is about 1.1), they are added to the graphene dispersion, and the mixture is stirred and reacted at 90 °C for 6 hours to obtain pre-oxidized graphene. Sodium percarbonate is dissolved in water to prepare a sodium percarbonate solution. Concentrated sulfuric acid and sodium percarbonate solution are sprayed into the pre-oxidized graphene, and the mixture is stirred and reacted at 90 °C for 6 hours to obtain a graphene oxide pre-product. The graphene oxide pre-product is washed with hydrogen peroxide with a concentration of 28% to obtain graphene oxide.

[0074] Preparation of graphene-based surfactant: Vinyltriethoxysilane is mixed with water to prepare an aqueous solution of vinyltriethoxysilane. The aqueous solution of vinyltriethoxysilane is sprayed into graphene oxide, and the reaction is carried out at 95 °C for 10 hours to obtain surface-modified graphene oxide. Diethanolamide laurate is sprayed into the surface-modified graphene oxide, and the mixture is stirred at 60 °C for 6 h. Then the product is dried in an oven and granulated in a pulverizer to obtain the final granular graphene-grafted surfactant.

[0075] Feeding for producing 1000 parts of products

[0076]

[0077] Indoor evaluation shows that the developed surfactant has excellent surface activity, and the specific indicators are as follows:

[0078]

[0079] The above are only several preferred embodiments of the present invention, but the present invention is not limited to the above specific implementation manners. The above specific implementation manners are illustrative rather than restrictive. Under the inspiration of the present invention and on the condition of following the spirit and principles of the present invention, researchers in this field can also make improvements and refinements, all of which fall within the protection scope of the present invention.

[0080] Matters not described in the present invention are well-known technologies.

Claims

1. A preparation method of a graphene-based surfactant, characterized in that, It includes the following steps: Prepare graphene oxide; Surface-modify graphene oxide with a silane coupling agent to obtain surface-modified graphene oxide; Graft an alkanolamide compound onto the surface-modified graphene oxide to obtain a graphene-based surfactant.

2. The preparation method according to claim 1, characterized in that, Prepare graphene oxide, including: Pre-oxidize graphene with potassium persulfate, phosphorus pentoxide, and concentrated sulfuric acid to obtain pre-oxidized graphene; Completely oxidize the pre-oxidized graphene with concentrated sulfuric acid and sodium percarbonate to obtain graphene oxide.

3. The preparation method according to claim 2, characterized in that, Prepare graphene oxide, including: After completely oxidizing the pre-oxidized graphene with concentrated sulfuric acid and sodium percarbonate to obtain a completely oxidized pre-product, wash the completely oxidized pre-product to obtain graphene oxide.

4. The preparation method according to claim 3, characterized in that, The washing process is carried out using hydrogen peroxide.

5. The preparation method according to claim 2, characterized in that, Pre-oxidize graphene with potassium persulfate, phosphorus pentoxide, and concentrated sulfuric acid to obtain pre-oxidized graphene, including: Disperse graphene in water, control its concentration within the range of 1 - 5 mg / mL, and ultrasonicate for 0.5 - 1 hour to form a uniform graphene dispersion; After dissolving concentrated sulfuric acid, phosphorus pentoxide, and potassium persulfate in a dissolution tank, add them to the graphene dispersion, and stir and react at 80 - 90 °C for 4 - 6 hours to obtain pre-oxidized graphene.

6. The preparation method according to claim 5, characterized in that, During the pre-oxidation process, the mass ratio of the added substances is: graphene: concentrated sulfuric acid: phosphorus pentoxide: potassium persulfate = 6 - 10: 0.3 - 0.4: 0.2 - 0.4: 1 - 2.

7. The preparation method according to claim 2, wherein Completely oxidize the pre-oxidized graphene with concentrated sulfuric acid and sodium percarbonate to obtain graphene oxide, including: Dissolve sodium percarbonate in water to prepare a sodium percarbonate solution; Spray concentrated sulfuric acid and the sodium percarbonate solution onto the pre-oxidized graphene, and stir and react at 80 - 90 °C for 4 - 6 hours to obtain graphene oxide.

8. The preparation method according to claim 7, characterized in that, During the complete oxidation process, the mass ratio of the added substances is: graphene: concentrated sulfuric acid: sodium percarbonate = 6 - 10: 0.2 - 0.3: 0.4 - 0.

6.

9. The preparation method according to claim 1, characterized in that, The silane coupling agent is vinyltriethoxysilane.

10. The preparation method according to claim 9, characterized in that, Surface-modify graphene oxide with a silane coupling agent to obtain surface-modified graphene oxide, including: Mix vinyltriethoxysilane with water to prepare an aqueous solution of vinyltriethoxysilane; Spray the aqueous solution of vinyltriethoxysilane onto graphene oxide, and react at 85 - 95 °C for 8 - 10 hours to obtain surface-modified graphene oxide.

11. The preparation method according to claim 10, characterized in that, The mass ratio of graphene to vinyltriethoxysilane added is 6 - 10: 1 - 3.

12. The preparation method according to claim 1, wherein The alkanolamide compound is lauric acid diethanolamide.

13. The preparation method according to claim 12, characterized in that, Graft lauric acid diethanolamide onto the surface-modified graphene oxide to obtain a graphene-based surfactant, including: Prepare a mixed solution of lauric acid diethanolamide by mixing lauric acid diethanolamide, water, and ethanol; Spray the mixed solution of lauric acid diethanolamide onto the surface-modified graphene oxide, and stir at 50 - 60 °C for 4 - 6 h to obtain a graphene-based surfactant.

14. The preparation method according to claim 13, wherein, When preparing the mixed solution of lauric acid diethanolamide, the mass ratio of lauric acid diethanolamide, water, and ethanol is 0.8 - 1: 0.8 - 1: 0.05 - 0.

1.

15. The preparation method according to claim 13, wherein, The mass ratio of graphene to diethanolamide laurate added is 6-10:60-70.

16. The preparation method according to claim 1, wherein The product obtained by grafting alkanolamide compounds onto surface-modified graphene oxide is dried and granulated to obtain the final granular graphene-based surfactant.

17. A graphene-based surfactant, characterized in that, It is prepared by the method described in any one of the above claims 1-16.

18. A water flooding system, characterized in that, It includes the graphene-based surfactant described in claim 17 above.

19. Application of the graphene-based surfactant described in claim 17 above in oil recovery.

20. Application of the water flooding system described in claim 18 above in oil recovery.

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