Preparation method of surfactant-grafted superparamagnetic graphene oxide and oil displacement method

Abstract

The invention discloses a preparation method of surface active agent grafted superparamagnetic graphene oxide, the surface active agent grafted superparamagnetic graphene oxide can be aminated and can also be non-aminated, and in the surface active agent grafted superparamagnetic aminated graphene oxide, the surface active agent grafted superparamagnetic graphene oxide has a specific surface area, and the surface active agent grafted superparamagnetic graphene oxide has a specific surface area. Superparamagnetic Fe3O4 nano-particles are loaded between graphene layers, and the superparamagnetic Fe3O4 nano-particles are prepared by the following method: ferrite and alkali are mixed and reacted to obtain a Fe (OH) 2 colloidal solution, and the Fe (OH) 2 colloidal solution is dried to be oxidized. The invention further discloses an oil displacement method, before oil displacement, the acid-base property of the oil reservoir is determined, and then the corresponding superparamagnetic graphene oxide grafted with the surfactant is selected as the oil displacement agent according to different acid-base properties of the oil reservoir. Graphene oxide is improved according to the acid-base property of different oil reservoirs, the carrier recovery efficiency is improved by breaking the bonding effect of a carrier and a surfactant, the viscosity of crude oil is reduced, and the fluidity of the crude oil is improved.

Description

Technical Field

[0001] The invention relates to a preparation method of superparamagnetic graphene oxide grafted with a surfactant and an oil displacement method. Background Art

[0002] As oil fields enter the late stage of development with high water content and high recovery rate, they are generally faced with the dual challenges of high mining costs and low recovery rates. At this time, it is particularly important to develop new oil recovery technologies to improve oil recovery rates and slow down the rate of attenuation. At present, chemical composite flooding, foam flooding, microbial flooding and tertiary oil recovery technologies based on nanomaterials have made significant progress.

[0003] With the increasing demand for technologies to treat industrial oily wastewater and marine oil spills, efficient oil-water separation technology has become one of the hot topics in current research. Studies have shown that magnetic nanomaterials can respond magnetically under an external magnetic field, providing driving force for droplets and increasing the speed of oil-water separation.

[0004] Existing technology combines magnetic nanomaterials with graphene oxide to provide magnetic response properties for high-load carriers to achieve the purpose of recycling. The composite material prepared by combining layered graphene oxide with magnetic nanomaterials can significantly reduce the oil-water interfacial tension and achieve efficient emulsification by utilizing the amphiphilicity of graphene oxide without an external magnetic field. Under the condition of an external magnetic field, aggregation occurs through magnetic response, thereby quickly breaking the emulsion and facilitating recycling and reuse. After testing, the composite material still has a high oil-water separation efficiency after three cycles of placement-recovery-ethanol washing. Summary of the invention

[0005] The inventors found that in the prior art, when using products combining magnetic nanomaterials and graphene oxide for oil recovery, the recovery effect of the carrier is unstable. Further research found that it is because of the strong combination of the carrier and the surfactant that when the crude oil is emulsified, the carrier and the surfactant cannot be completely recovered using an external magnetic field. On this basis, the present invention was made. And in the process of implementing the present invention, the inventors unexpectedly found that by improving the graphene oxide according to the acidity and alkalinity of different oil reservoirs, while improving the recovery efficiency of the carrier by interrupting the bonding between the carrier and the surfactant, because the surfactant remains in the crude oil, the viscosity of the crude oil is reduced and its fluidity is improved, which provides convenience for the next step of pipeline collection and transportation of crude oil and effectively reduces energy consumption.

[0006] As one aspect of the present invention, it relates to a method for preparing superparamagnetic graphene oxide grafted with a surfactant. The superparamagnetic graphene oxide grafted with a surfactant may be amino-modified or non-amino-modified. In the superparamagnetic amino-modified graphene oxide grafted with a surfactant, superparamagnetic Fe3O4 nanoparticles are loaded between graphene layers. In the method, the superparamagnetic Fe3O4 nanoparticles are prepared by the following method: a ferrous salt is mixed with an alkali to react to obtain a Fe(OH)2 colloidal solution, which is then dried until oxidized.

[0007] The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

[0008] The alkali is sodium hydroxide, potassium hydroxide or ammonia water.

[0009] As another aspect of the present invention, it relates to an oil displacement method. Before oil displacement, the method first determines the acidity and alkalinity of the oil reservoir, and then selects the corresponding superparamagnetic graphene oxide grafted surfactant as an oil displacement agent according to the different acidity and alkalinity of the oil reservoir. Specifically, when the oil reservoir is an acidic oil reservoir, the superparamagnetic graphene oxide grafted surfactant is used as the oil displacement agent; when the oil reservoir is an alkaline oil reservoir, the superparamagnetic graphene oxide grafted surfactant is used as the oil displacement agent.

[0010] In a specific embodiment, the superparamagnetic graphene oxide of the amino-grafted surfactant is prepared by the following method:

[0011] (1) ferrous salt and alkali are mixed and reacted to obtain a Fe(OH)2 colloidal solution, which is dried and oxidized to generate superparamagnetic Fe3O4 nanoparticles, which are dispersed in an aqueous solution of graphene oxide using an ultrasonic cell wall disruptor to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles;

[0012] (2) The superparamagnetic graphene oxide prepared in step (1) is dispersed in DMF, and SOCl2 and DETA are added to react to obtain superparamagnetic amino-modified graphene oxide;

[0013] (3) The superparamagnetic amino-modified graphene oxide obtained in step (2) is mixed with a surfactant in a DMF solvent, and EDC and NHS are added to complete an amidation reaction to obtain a superparamagnetic amino-modified graphene oxide grafted with lauryl amide propyl betaine.

[0014] The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

[0015] The alkali is sodium hydroxide, potassium hydroxide or ammonia water.

[0016] Specifically, the superparamagnetic graphene oxide of the non-aminated grafted surfactant is prepared by the following method:

[0017] (1) ferrous salt and alkali are mixed and reacted to obtain a Fe(OH)2 colloidal solution, which is dried and oxidized to generate superparamagnetic Fe3O4 nanoparticles, which are dispersed in an aqueous solution of graphene oxide using an ultrasonic cell wall disruptor to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles;

[0018] (2) The superparamagnetic graphene oxide carrier obtained in step (1) is mixed with a surfactant in a DMF solvent, EDC and NHS are added, and an esterification reaction is completed to obtain a superparamagnetic graphene oxide grafted with cocamidopropyl betaine.

[0019] The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

[0020] The alkali is sodium hydroxide, potassium hydroxide or ammonia water.

[0021] The technical solution of the present invention is to use graphene oxide as a surfactant carrier, uniformly disperse the graphene oxide in N,N-dimethylformamide (DMF) by ultrasound, add 2.0mL of dichlorothionyl (SOCl2) and 5.0mL of diethylenetriamine (DETA) to the graphene oxide suspension, heat it to 80°C and keep it warm for 4 hours. After cooling, centrifuge the suspension at 10000rpm for 30 minutes to obtain a crude product of amino graphene oxide. Then wash it three times with DMF, alcohol and pure water. Before testing, seal the dried amino graphene oxide sample in a clean glass sample bottle. First, add an appropriate amount of divalent iron salt (Fe 2+ ) solution and alkaline solution are mixed to generate Fe(OH)2 colloidal solution, and the colloidal solution is placed in a forced air drying oven at an appropriate temperature and ventilated until it is dry and blackened, so that the Fe(OH)2 is partially oxidized and finally superparamagnetic Fe3O4 nanoparticles are generated. The obtained Fe3O4 nanoparticle suspension colloid is dispersed in an amination graphene oxide solution using an ultrasonic cell wall breaking machine, and the pH of the mixed solution is adjusted to a suitable acidity. Polyanion sodium tripolyphosphate (STPP) is added to the mixed solution to promote the precipitation of nano Fe3O4 crystal nuclei in the solution, generate nano or submicron magnetic nanoparticles, and coat the magnetic nano Fe3O4 particles to form a superparamagnetic amination graphene oxide carrier coated with nano magnetic Fe3O4 particles. The carrier is mixed with various surfactants (such as zwitterionic surfactants, anionic surfactants, etc.) in different proportions using DMF as a solvent, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) are added to complete amide reaction or hydrogen bonding to obtain a surfactant with superparamagnetic amino graphene oxide as a carrier.

[0022] Compared with traditional magnetic surfactants, the present invention has the function of adaptively separating carriers and surfactants. Generally, magnetic surfactants are a whole, and their purpose is to quickly separate the surfactant connected to the carrier from the emulsion through external magnetism to achieve the effect of rapid demulsification. The carrier and the surfactant in the present invention can break the chemical bond connecting the carrier and the surfactant under acidic or alkaline conditions, so that the carrier is separated under external magnetic field conditions, and part of the surfactant remains in the emulsion, which has the effect of emulsifying crude oil and is convenient for crude oil viscosity reduction and collection and transportation.

[0023] The present invention can load superparamagnetic Fe3O4 nanoparticles into graphene oxide sheets under mild conditions, impart superparamagnetism to the graphene oxide carrier, bidirectionally and reversibly regulate the oil-water emulsification performance according to changes in the external magnetic field, and carry out surfactant grafting modification on the carrier to make the carrier have oil-water interfacial activity, which can not only emulsify the oil and water efficiently, but also demulsify stably and quickly under the condition of an external magnetic field, thereby greatly improving the oil-water separation efficiency of oilfield produced fluid, simplifying the production process, and being recyclable and reusable to reduce costs, and ultimately achieving full-process regulation of the performance of the oil displacement surfactant.

[0024] The evaluation results of the characterization of the superparamagnetic graphene oxide carrier of the present invention show that the superparamagnetic graphene oxide surfactant carrier is still a nanosheet structure; the magnetic graphene oxide surfactant has the functional groups of graphene oxide and the functional groups of surfactant. The magnetization intensity of the magnetic graphene oxide surfactant carrier can reach 25emu / g, which is a strong magnetic material. The present invention can effectively graft surfactants, thereby achieving efficient emulsification of oil and water, and can also quickly demulsify under external magnetic field conditions, and is expected to become a new generation of intelligent surfactants for oilfield development. DETAILED DESCRIPTION

[0025] Example 1 (for acidic oil reservoirs)

[0026] (1) Preparation of superparamagnetic graphene oxide: First, Fe(NO3)2 solution and NaOH solution (molar ratio 1:1) were mixed and reacted to obtain Fe(OH)2 colloidal solution, which was placed in a forced air drying oven and ventilated at 50°C for 24 hours. It dried and turned black, and Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor. The pH was adjusted to 6, and STPP (600W, ultrasonic time of 2s, interval of 6s, a total of 2h) was added. Fe3O4 nanocrystal nuclei precipitated to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles, which was used as a carrier. The superparamagnetism of superparamagnetic graphene oxide comes from the interlayer loaded Fe3O4 nanoparticles.

[0027] (2) Preparation of superparamagnetic amino-modified graphene oxide: Ultrasonication for 1 h (P = 400 W), 0.3 g of the superparamagnetic graphene oxide prepared in step (1) was dispersed in 100 mL of DMF to form a suspension, 2.0 mL of SOCl2 and 5.0 mL of DETA were added, heated to 80°C for 4 h, cooled, and centrifuged at 10000 rpm for 30 minutes to obtain superparamagnetic amino-modified graphene oxide. Washed with DMF, alcohol and pure water three times, and freeze-dried to obtain dry superparamagnetic amino-modified graphene oxide.

[0028] (3) Superparamagnetic amino-graphene oxide grafted surfactant: Superparamagnetic amino-graphene oxide and lauryl amide propyl betaine are mixed in a DMF solvent at a molar ratio of 1:1, and EDC and NHS are added to complete the amidation reaction to obtain superparamagnetic amino-graphene oxide grafted with lauryl amide propyl betaine as an oil displacement agent.

[0029] Example 2 (for alkaline oil reservoirs)

[0030] (1) Preparation of superparamagnetic graphene oxide: First, FeCl2 solution and NaOH solution (molar ratio 1:1.2) were mixed and reacted to obtain Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 70°C for 18 hours, dried and turned black, and Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (600W, ultrasonic time of 3s, interval of 6s, a total of 2h), and Fe3O4 nanocrystal nuclei were precipitated to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles, which was used as a carrier.

[0031] (2) Superparamagnetic graphene oxide carrier loaded with surfactant: The superparamagnetic graphene oxide carrier and lauryl amide propyl betaine were mixed in a DMF solvent at a molar ratio of 1:1, and EDC and NHS were added to complete the esterification reaction to obtain superparamagnetic graphene oxide grafted with cocoamidopropyl betaine as an oil displacement agent.

[0032] Example 3 (for acidic oil reservoirs)

[0033] (1) Preparation of superparamagnetic graphene oxide carrier: First, an appropriate amount of FeSO4 solution and NaOH solution (molar ratio 1:1) were mixed and reacted to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 80°C for 24 hours, dried and turned black, and Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor, the pH was adjusted to 7, STPP was added (600W, ultrasonic time of 3s, interval of 4s, a total of 3h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0034] (2) Preparation of superparamagnetic amino-modified graphene oxide carrier: 0.2 g of the prepared superparamagnetic graphene oxide was dispersed in 80 mL of DMF by ultrasound for 1 h (P = 400 W) to form a suspension, 2.0 mL of SOCl2 and 5.0 mL of DETA were added to the suspension, heated to 80 ° C for 4 h, cooled, and centrifuged at 10000 rpm for 30 minutes to obtain superparamagnetic amino-modified graphene oxide. Washed with DMF, alcohol and pure water three times, and freeze-dried to obtain dry superparamagnetic amino-modified graphene oxide.

[0035] (3) Superparamagnetic amino graphene oxide carrier grafted with surfactant: Superparamagnetic amino graphene oxide and lauryl amide propyl hydroxyflavone betaine were mixed in a DMF solvent at a molar ratio of 1:1, and EDC and NHS were added to complete the amidation reaction to obtain superparamagnetic amino graphene oxide grafted with lauryl amide propyl hydroxyflavone betaine, which was used as an oil displacement agent.

[0036] Example 4 (for alkaline oil reservoirs)

[0037] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeSO4 solution and KOH solution (molar ratio 1:1) were mixed and reacted to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 80°C for 12 hours to dry and turn black, so that the Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticle suspension colloid was dispersed in an aqueous solution of graphene oxide for 30 minutes (1600W) using an ultrasonic cell wall disruptor, the pH was adjusted to 5, and STPP was added (800W, ultrasonic time of 4s, interval of 6s, a total of 3h), and Fe3O4 nanocrystal nuclei were precipitated to form a superparamagnetic graphene oxide carrier with superparamagnetic Fe3O4 nanoparticles coated between layers.

[0038] (2) Superparamagnetic graphene oxide carrier grafted with surfactant: A superparamagnetic graphene oxide carrier and lauryl amide propyl hydroxyflavone betaine were mixed in a DMF solvent at a molar ratio of 1:1, and EDC and NHS were added to complete the esterification reaction to obtain superparamagnetic graphene oxide grafted with lauryl amide propyl hydroxyflavone betaine as an oil displacement agent.

[0039] Example 5 (for acidic oil reservoirs)

[0040] (1) Preparation of superparamagnetic graphene oxide carrier: First, an appropriate amount of FeCl2 solution and KOH solution (molar ratio 1:1) were mixed and reacted to obtain a Fe(OH)2 colloidal solution, which was dried and blackened in a forced air drying oven at 75°C for 12 hours to partially oxidize Fe(OH)2 and generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 30 minutes (1600W) using an ultrasonic cell wall disruptor, the pH was adjusted to 5, and STPP (800W, ultrasonic time of 3s, interval of 5s, a total of 2.5h) was added to precipitate nano-Fe3O4 nuclei, forming superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles, which was used as a carrier.

[0041] (2) Preparation of superparamagnetic amino-modified graphene oxide carrier: 0.25 g of the prepared amino-modified graphene oxide was dispersed in 100 mL of DMF by ultrasound for 1 h (P = 400 W) to form a suspension, 2 mL of SOCl2 and 5 mL of DETA were added to the suspension, heated to 80 ° C for 4 h, cooled, and the suspension was centrifuged at 10000 rpm for 30 minutes to obtain superparamagnetic amino-modified graphene oxide. It was washed three times with DMF, alcohol and pure water, and freeze-dried to obtain dry superparamagnetic amino-modified graphene oxide.

[0042] (3) Superparamagnetic amino-modified graphene oxide carrier grafted with surfactant: Superparamagnetic amino-modified graphene oxide and sodium α-lauryl polyether sulfate are mixed in a DMF solvent at a molar ratio of 1:1 to complete an amidation reaction to obtain superparamagnetic amino-modified graphene oxide grafted with sodium α-lauryl polyether sulfate as an oil-displacing agent.

[0043] Example 6 (for alkaline oil reservoirs)

[0044] (1) Preparation of superparamagnetic graphene oxide: First, Fe(NO3)2 solution and KOH solution (molar ratio 1:1) were mixed and reacted to obtain Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 80°C for 16 hours to dry and turn black, so that Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1800W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (800W, ultrasonic time of 3s, interval of 4s, total of 3h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0045] (2) Superparamagnetic graphene oxide carrier grafted with surfactant: Superparamagnetic graphene oxide and sodium dodecylbenzene sulfonate are mixed in a DMF solvent at a molar ratio of 1:1 to complete an esterification reaction to obtain superparamagnetic graphene oxide grafted with sodium dodecylbenzene sulfonate.

[0046] Example 7 (for acidic oil reservoirs)

[0047] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of Fe(NO3)2 solution and ammonia water (molar ratio 1:2) were mixed and reacted to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 60°C for 24 hours to dry and turn black, so that Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (600W, ultrasonic time of 2s, interval of 5s, a total of 4h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0048] (2) Preparation of superparamagnetic amino-modified graphene oxide: 0.2 g of superparamagnetic graphene oxide was uniformly dispersed in 100 mL of DMF by ultrasound for 60 min (P = 500 W) to form a suspension, 2 mL of SOCl2 and 5 mL of DETA were added to the suspension, heated to 80°C and kept warm for 5 h, cooled, and the suspension was centrifuged at 10,000 rpm for 30 min to obtain superparamagnetic amino-modified graphene oxide, which was washed three times with DMF, alcohol and pure water, and freeze-dried to obtain superparamagnetic amino-modified graphene oxide.

[0049] (3) Superparamagnetic aminated graphene oxide carrier grafted with surfactant: Superparamagnetic aminated graphene oxide and sodium α-olefin sulfonate are mixed in a DMF solvent at a molar ratio of 1:1 to complete an amidation reaction to obtain superparamagnetic graphene oxide grafted with sodium α-olefin sulfonate as an oil displacement agent.

[0050] Example 8 (for alkaline oil reservoirs)

[0051] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeCl2 solution and ammonia water (molar ratio 1:2) were mixed to react to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 60°C for 24 hours to dry and turn black, so that Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1500W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (800W, ultrasonic time of 2s, interval of 6s, a total of 2h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0052] (2) Superparamagnetic graphene oxide carrier grafted with surfactant: Superparamagnetic graphene oxide and lauryl amide propyl betaine are mixed in a DMF solvent in a molar ratio of 1:1, and an esterification reaction is completed to obtain superparamagnetic graphene oxide grafted with lauryl amide propyl betaine as an oil displacement agent.

[0053] Example 9 (for acidic oil reservoirs)

[0054] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeSO4 solution and ammonia water (molar ratio 1:2) were mixed and reacted to obtain a Fe(OH)2 colloidal solution, which was dried and blackened in a forced air drying oven at 60°C for 24 hours to partially oxidize Fe(OH)2 and generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1500W) using an ultrasonic cell wall disruptor, the pH was adjusted to 5, STPP was added (600W, ultrasonic time of 3s, interval of 6s, total of 3h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0055] (2) Preparation of superparamagnetic amino-modified graphene oxide: 0.25 g of superparamagnetic graphene oxide was dispersed in 100 mL of DMF by ultrasound for 40 min (P = 500 W) to obtain a suspension, 2 mL of SOCl2 and 5 mL of DETA were added to the suspension, heated to 80°C for 5 h, cooled, and the suspension was centrifuged at 10,000 rpm for 30 minutes to obtain superparamagnetic amino-modified graphene oxide. It was then washed three times with DMF, alcohol, and pure water, and freeze-dried to obtain dry superparamagnetic amino-modified graphene oxide.

[0056] (3) Superparamagnetic amino graphene oxide carrier grafted with surfactant: Superparamagnetic amino graphene oxide and lauryl amide propyl hydroxyflavone betaine are mixed in a DMF solvent in a molar ratio of 1:1 to complete the amidation reaction to obtain superparamagnetic amino graphene oxide grafted with lauryl amide propyl hydroxyflavone betaine as an oil displacement agent.

[0057] Example 10 (for alkaline oil reservoirs)

[0058] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeSO4 solution and ammonia water (molar ratio 1:2.2) were mixed to react to obtain a Fe(OH)2 colloidal solution, which was dried and blackened in a forced air drying oven at 60°C for 24 hours to partially oxidize Fe(OH)2 to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (600W, ultrasonic time of 4s, interval of 6s, a total of 4h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0059] (2) Superparamagnetic graphene oxide carrier grafted with surfactant: Superparamagnetic graphene oxide and dodecyl dimethyl betaine are mixed in a DMF solvent at a molar ratio of 1:1, and an esterification reaction is completed to obtain superparamagnetic graphene oxide grafted with dodecyl dimethyl betaine as an oil displacement agent.

[0060] Example 11 (for acidic oil reservoirs)

[0061] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeSO4 solution and ammonia water (molar ratio 1:2.2) were mixed to react to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 60°C for 18 hours to dry and turn black, so that Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1800W) using an ultrasonic cell wall disruptor, the pH was adjusted to 5, STPP was added (600W, ultrasonic time of 2s, interval of 5s, total of 3h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0062] (2) Preparation of superparamagnetic amino-modified graphene oxide: 0.25 g of graphene oxide was uniformly dispersed in 100 mL of DMF by ultrasound for 50 min (P = 400 W) to form a suspension, 2 mL of SOCl2 and 5 mL of DETA were added to the suspension and heated to 80°C for 3 h, cooled, and the suspension was centrifuged at 10,000 rpm for 30 min to obtain superparamagnetic amino-modified graphene oxide, which was washed three times with DMF, alcohol and pure water, and freeze-dried to obtain dry superparamagnetic amino-modified graphene oxide.

[0063] (3) Superparamagnetic amino-treated graphene oxide carrier grafted with surfactant: A superparamagnetic amino-treated graphene oxide carrier and dodecyl dimethyl betaine are mixed in a DMF solvent in a molar ratio of 1:1 to complete an amidation reaction to obtain a superparamagnetic amino-treated graphene oxide grafted with dodecyl dimethyl betaine as an oil displacement agent.

[0064] Example 12 (for alkaline oil reservoirs)

[0065] (1) Preparation of superparamagnetic graphene oxide: First, an appropriate amount of FeSO4 solution and ammonia water (molar ratio 1:2.2) were mixed to react to obtain a Fe(OH)2 colloidal solution, which was placed in a forced air drying oven at 60°C for 20 hours to dry and turn black, so that Fe(OH)2 was partially oxidized to generate superparamagnetic Fe3O4 nanoparticles. The obtained superparamagnetic Fe3O4 nanoparticles were dispersed in an aqueous solution of graphene oxide for 20 minutes (1200W) using an ultrasonic cell wall disruptor, the pH was adjusted to 6, STPP was added (600W, ultrasonic time of 2s, interval of 5s, a total of 3h), Fe3O4 nanocrystal nuclei were precipitated, and superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles was formed, which was used as a carrier.

[0066] (2) Superparamagnetic graphene oxide carrier grafted with surfactant: Superparamagnetic graphene oxide and cocamidopropyl betaine are mixed in a DMF solvent in a molar ratio of 1:1, and an esterification reaction is completed to obtain superparamagnetic graphene oxide grafted with cocamidopropyl betaine as an oil-displacing agent.

[0067] Example 13

[0068] Simulate the acidic reservoir (pH = 5), use the superparamagnetic amino-modified graphene oxide prepared by Examples 1, 3, 5, 7, 9, and 11 to carry out emulsification test with surfactant, record the emulsification ratio, and test the viscosity before and after recovery. The simulated acidic reservoir emulsification experiment was conducted with a concentration of 0.25%. After stabilization for 1 hour, the emulsification ratio was measured to be within the range of 68.5 ± 2.9%. Among them, Example 1 has the best emulsification effect, with an emulsification ratio of 71.4%.

[0069] The emulsification effect test of the oil-displacing agent obtained in Examples 1, 3, 5, 7, 9, and 11 showed that the emulsification ability of the displacement fluid prepared by the oil-displacing agent and water increased with the increase of the concentration of the oil-displacing agent (0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%) (emulsification ratios were 43.1±2.5%, 47.1±1.6%, 53.1±3.5%, 63.1±4.1%, 68.5±2.9%, 68.7±3.4%). When the concentration was 0.25%, the emulsification performance was most significantly improved.

[0070] Embodiment 14

[0071] Simulating alkaline reservoirs (pH = 9), the superparamagnetic graphene oxide prepared by Examples 2, 4, 6, 8, 10, and 12 was used to carry out emulsification tests with surfactants, the emulsification ratio was recorded, and the viscosity before and after recovery was tested. The emulsification experiment of the simulated alkaline reservoir was conducted with a concentration of 0.25%. After stabilization for 1 hour, the emulsification ratio was measured to be within the range of 72.1±4.2%. Among them, the emulsification effect of Example 2 was the best, with an emulsification ratio of 76.3%. This is mainly because the selection of different surfactants has an effect on the emulsification ratio, and the emulsification ratio of alkaline reservoirs is higher because it is easier to reduce interfacial tension and change the wettability of rocks.

[0072] The emulsification effect test of the oil-displacing agents obtained in Examples 2, 4, 6, 8, 10, and 12 showed that the emulsification ability of the displacement fluid prepared by the oil-displacing agent and water increased with the increase of the concentration of the oil-displacing agent (0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%) (emulsification ratios were 45.3±1.4%, 51.3±1.8%, 56.1±2.4%, 67.3±3.0%, 72.1±4.2%, 72.3±2.2%). When the concentration was 0.25%, the emulsification performance was most significantly improved.

[0073] Embodiment 15

[0074] Reservoirs with a pH of 5, 7, and 9 were simulated respectively, and the superparamagnetic graphene oxide prepared in Examples 1, 3, 5, 7, 9, 11 and 2, 4, 6, 8, 10, and 12 were respectively loaded with a surfactant for emulsification and then recovered for testing. After recovery, the surfactant was loaded for 5 cycles.

[0075] When the pH is 5, the recovery results of five cycles of Examples 1, 3, 5, 7, 9, and 11 are 80.1±2.3%, 76.3±2.6%, 72.4±1.4%, 68.6±1.3% and 66.5±2.3%, and the recovery results of five cycles of Examples 2, 4, 6, 8, 10, and 12 are 60.4±3.1%, 58.6±2.4%, 55.3±1.7%, 51.6±3.5% and 45.4±2.7%.

[0076] When the pH value was 7, the recovery results of Examples 1-12 after five cycles were 62.4±4.6%, 59.3±4.4%, 54.3±3.8%, 50.4±3.9% and 43.9±4.1%.

[0077] When the pH is 9, the recovery results of five cycles of Examples 1, 3, and 5 are 64.6±1.7%, 61.4±1.6%, 58.6±2.4%, 56.3±1.9% and 52.9±3.3%, and the recovery results of five cycles of Examples 2, 4, and 6 are 85.6±2.1%, 81.6±3.1%, 78.6±1.8%, 74.6±3.1% and 70.6±2.3%.

[0078] The recovery rates of Examples 1, 3, 5, 7, 9, and 11 are relatively high in acidic reservoirs, but low in alkaline or neutral reservoirs. Because the bonding between the carrier and the surfactant is disconnected, the carrier is recovered under an external magnetic field without the need to recover the surfactant, so the recovery rate is high. However, under neutral or alkaline conditions, the bonding between the carrier and the surfactant cannot be disconnected, and due to the interaction between the crude oil and the surfactant, the carrier cannot be more attracted by the external magnetic field, thereby reducing the recovery rate.

[0079] The recovery rates of Examples 2, 4, 6, 8, 10, and 12 are relatively high in alkaline reservoirs, but low in acidic or neutral reservoirs. The esterification reaction is hydrolyzed under alkaline conditions, breaking the bonding between the carrier and the surfactant. The carrier is recovered under an external magnetic field without the need to recover the surfactant, so the recovery rate is high. However, the bonding cannot be broken under neutral or acidic conditions, and due to the interaction between the crude oil and the surfactant, the carrier can no longer be attracted by the external magnetic field, thereby reducing the recovery rate.

[0080] Example 16

[0081] The superparamagnetic amino-modified graphene oxide and superparamagnetic graphene oxide prepared in Examples 1-12 were subjected to scanning electron microscopy to detect their morphological characteristics. The results were basically similar, and the superparamagnetic graphene oxide was still a nanosheet structure, in which the black was magnetic nanoparticles under a high-resolution electron microscope.

[0082] Embodiment 17

[0083] The superparamagnetic amino-modified graphene oxide and superparamagnetic graphene oxide prepared in Examples 1-12 were subjected to FT-IR testing to detect changes in their functional groups.

[0084] The results of infrared characterization are slightly different. Superparamagnetic amino-modified graphene oxide has a wavelength of 1700 cm -1 There is an obvious amino peak at the center, which is almost consistent with the functional groups of superparamagnetic graphene oxide, and the functional groups after loading with surfactants are also reflected.

[0085] Embodiment 18

[0086] The superparamagnetic amino-treated graphene oxide and superparamagnetic graphene oxide prepared in Examples 1-12 were characterized by magnetic flux, proving that they possessed superparamagnetism.

[0087] The magnetic strength of both superparamagnetic amino-modified graphene oxide and superparamagnetic graphene oxide can reach over 23emu / g, which is close to the standard of strong magnetic materials and has recycling potential.

[0088] Embodiment 19

[0089] The superparamagnetic amino-modified graphene oxide and superparamagnetic graphene oxide prepared in Examples 1-12 were emulsified with a surfactant or with a surfactant alone, and the morphology of the emulsion droplets with and without the carrier was observed using a microscope.

[0090] Comparative Example 1

[0091] Magnetic graphene oxide is prepared with reference to patent publication CN107746053A. CN107746053A uses divalent iron and trivalent iron as iron sources, and uses strong alkali to grow Fe3O4 magnetic nanoparticles between graphene oxide layers, and generates magnetic graphene oxide in one go; while the present invention uses divalent iron as an iron source and reacts with alkali to generate Fe(OH)2 colloid, and gives enough oxygen to oxidize Fe3O4 magnetic nanoparticles through a blast drying oven, opens the graphene oxide layers through an ultrasonic cell crusher, and precipitates under weak acidity through sodium tripolyphosphate to generate magnetic graphene oxide. The method used in CN107746053A is that strong alkali is used to generate Fe3O4 magnetic nanoparticles between graphene oxide layers, and strong alkali will reduce graphene oxide, reduce the oxygen-containing functional groups of graphene oxide, and will affect the later loading of surfactants. Moreover, the Fe3O4 magnetic nanoparticles prepared by strong alkali have uneven particle sizes, and oversized Fe3O4 microspheres will have magnetism, causing magnetic graphene to agglomerate, which is not conducive to dispersion. The present invention first prepares Fe3O4 nanoparticles, and then uses an ultrasonic method to precipitate them between graphene oxide layers. The weakly acidic conditions will not reduce graphene oxide, will not reduce the content of oxygen-containing functional groups, and will not cause graphene oxide to agglomerate.

[0092] Comparative Example 2

[0093] Magnetic graphene oxide is prepared with reference to patent disclosure CN115261002A. CN115261002A firstly aminates graphene oxide, then uses divalent iron and trivalent iron as iron sources, and uses strong alkali to grow Fe3O4 magnetic nanoparticles between the aminated graphene oxide layers; while the present invention first uses divalent iron as an iron source and reacts with alkali to generate Fe(OH)2 colloid, then oxidizes it with sufficient oxygen through a blast drying oven to generate Fe3O4 magnetic nanoparticles, and then compounds it with graphene oxide under weak acidic conditions, and then performs amination modification. In contrast, the patent aminates graphene oxide first and then magnetizes it under strong alkali conditions, which will reduce the oxygen-containing functional groups of graphene oxide itself. Strong alkali will also affect the use of aminated functional groups, reduce the loading efficiency of surfactants, and easily agglomerate to affect oil displacement efficiency. This patent is advanced magnetization before amination, so there will be no agglomeration and no effect on the use of aminated functional groups.

[0094] The emulsification ratio of the surfactant obtained in Comparative Example 1 (the concentration of the displacement fluid prepared by the oil displacement agent and water is 0.25%) is 58.3%, and the emulsification ratio of the surfactant obtained in Comparative Example 2 (0.25% concentration) is 61.7%. The emulsification effect of the comparative example is poorer than that of Examples 1-12.

[0095] The surfactants obtained in Examples 1-12 (the concentration of the displacement fluid prepared by the oil displacement agent and water is 0.25%) were used to test the viscosity of crude oil before and after emulsification, and the result of Example 5 was the best. The viscosity of Daqing crude oil before emulsification was 1209.6 mPa·s, and the viscosity was reduced to 608.4 mPa·s after emulsification by adding the surfactant obtained in Example 5 (concentration 0.25%), and the viscosity was 913.6 mPa·s after the carrier was recovered. Therefore, the retention of some surfactants after the carrier is recovered is helpful for the collection and transportation of crude oil.

[0096] Examples 13 and 14 compare the viscosity before and after recovery, and the crude oil emulsification effect of the carrier with surfactant (concentration 0.25%, wherein the carrier content is about 0.15%, and the surfactant content is about 0.1%) and the corresponding content of surfactant (0.1%). The addition of the carrier makes the crude oil droplets smaller and more uniform. Because of the presence of graphene, the droplets are smaller. Because the nanosheet structure and hydrophilicity can invade the interface between crude oil and water, the emulsification degree is further improved, making the droplets smaller.

Claims

1. A method for preparing superparamagnetic graphene oxide grafted with a surfactant, wherein the superparamagnetic graphene oxide grafted with a surfactant may be amino- or non-amino-, and in the superparamagnetic amino-graphene oxide grafted with a surfactant, superparamagnetic Fe3O4 nanoparticles are loaded between graphene layers, characterized in that: The superparamagnetic Fe3O4 nanoparticles are prepared by the following method: ferrous salt and alkali are mixed and reacted to obtain Fe(OH)2 colloidal solution, which is dried until oxidation occurs.

2. The method for preparing superparamagnetic graphene oxide grafted with surfactant according to claim 1, characterized in that: The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

3. The method for preparing superparamagnetic graphene oxide grafted with surfactant according to claim 1, characterized in that: The alkali is sodium hydroxide, potassium hydroxide or ammonia water.

4. An oil displacement method, characterized in that: Before oil displacement, the acidity and alkalinity of the reservoir are determined first, and then, according to the different acidity and alkalinity of the reservoir, the corresponding superparamagnetic graphene oxide grafted with a surfactant is selected as an oil displacement agent.

5. The method according to claim 4, characterized in that When the oil reservoir is an acidic oil reservoir, superparamagnetic graphene oxide with an amino-grafted surfactant is used as an oil-displacing agent; when the oil reservoir is an alkaline oil reservoir, superparamagnetic graphene oxide with an unaminated grafted surfactant is used as an oil-displacing agent.

6. The method according to claim 5, characterized in that The superparamagnetic graphene oxide of the amino-grafted surfactant is prepared by the following method: (1) ferrous salt and alkali are mixed and reacted to obtain a Fe(OH)2 colloidal solution, which is dried and oxidized to generate superparamagnetic Fe3O4 nanoparticles, which are dispersed in an aqueous solution of graphene oxide using an ultrasonic cell wall disruptor to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles; (2) The superparamagnetic graphene oxide prepared in step (1) is dispersed in DMF, and SOCl2 and DETA are added to react to obtain superparamagnetic amino-modified graphene oxide; (3) The superparamagnetic amino-modified graphene oxide obtained in step (2) is mixed with a surfactant in a DMF solvent, and EDC and NHS are added to complete an amidation reaction to obtain a superparamagnetic amino-modified graphene oxide grafted with lauryl amide propyl betaine.

7. The method of claim 6, characterized in that The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

8. The method of claim 6, characterized in that The alkali is sodium hydroxide, potassium hydroxide or ammonia water.

9. The method of claim 5, characterized in that The superparamagnetic graphene oxide of the non-aminated grafted surfactant is prepared by the following method: (1) ferrous salt and alkali are mixed and reacted to obtain a Fe(OH)2 colloidal solution, which is dried and oxidized to generate superparamagnetic Fe3O4 nanoparticles, which are dispersed in an aqueous solution of graphene oxide using an ultrasonic cell wall disruptor to form superparamagnetic graphene oxide with interlayer loaded Fe3O4 nanoparticles; (2) The superparamagnetic graphene oxide carrier obtained in step (1) is mixed with a surfactant in a DMF solvent, EDC and NHS are added, and an esterification reaction is completed to obtain a superparamagnetic graphene oxide grafted with cocamidopropyl betaine.

10. The method according to claim 9, characterized in that The ferrous salt is ferrous nitrate, ferrous chloride or ferrous sulfate.

11. The method of claim 9, characterized in that The alkali is sodium hydroxide, potassium hydroxide or ammonia water.