Oil-water separation membrane for oil field fracturing flow-back fluid and preparation method of oil-water separation membrane

Abstract

The invention belongs to the technical field of oil-water separation, and provides an oil-water separation membrane for oilfield fracturing flow-back fluid and a preparation method of the oil-water separation membrane. The preparation method comprises the following steps: by taking a red copper plate as an anode and a copper mesh as a cathode, carrying out electrochemical deposition in an electrolyte solution by adopting a dual-electrode system to obtain the copper mesh with deposited copper particles; soaking the copper mesh deposited with the copper particles in an alkaline oxidation solution to obtain an oil-water separation membrane; the alkaline oxidation solution is a mixed solution of NaOH, (NH4) 2S2O8 and water. The preparation method is simple, convenient and efficient, the small-size milky oil-water separation membrane is rapidly prepared through an electrochemical deposition and alkali-assisted oxidation two-step method, and the small-size milky oil-water separation membrane has excellent oil-water separation efficiency, high permeation flux and excellent stability.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-water separation, and in particular to an oil-water separation membrane for oilfield fracturing drainage fluid and a preparation method thereof. Background Art

[0002] Shale oil production uses large amounts of fracturing fluid, which carries a significant amount of oil sludge back to the surface. Leakage can cause severe environmental and water pollution, harming human health and causing significant economic losses. Traditional oil-water separation methods, such as centrifugation, biodegradation, gravity separation, chemical separation, and adsorption separation, suffer from low energy efficiency, poor separation performance, and difficulty in recycling, limiting their application in large-scale oil-water treatment.

[0003] Among various oil-water separation methods, membrane filtration is considered the most promising due to its high efficiency, low energy consumption, wide applicability, and simple operation. Membrane materials used for oil-water separation include cotton, sponge, fiber, and polymer membranes. These membrane materials are difficult to regenerate, have poor hydrophilicity, and suffer from poor mechanical properties. In comparison, inorganic metal mesh membranes offer multiple advantages, including high mechanical strength, excellent chemical stability, high flux, long life, and easy regeneration. They offer significant advantages in treating oil-water emulsions with high impurity content, such as fracturing flowback fluids.

[0004] Oil-water separation membranes made of superhydrophilic / underwater superoleophobic materials allow water to easily pass through due to their superhydrophilic surface properties, while their superoleophobic properties block the flow of oil and prevent oil contamination. Therefore, using metal mesh as a substrate and constructing the special wettability of superhydrophilic / underwater superoleophobic surfaces on it has broad prospects for oil-water separation. However, the preparation process is complex, requiring multiple steps and precise process control, and consumes a large amount of manufacturing materials, resulting in high manufacturing costs. This makes it difficult to apply the research results to actual production, which has become a pain point that needs to be addressed.

[0005] Therefore, it is of great significance to study and obtain an oil-water separation membrane for oilfield fracturing reverse flow fluid with improved separation efficiency and stability, simple process and low cost, and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to provide an oil-water separation membrane for oilfield fracturing reverse flow and a preparation method thereof in order to overcome the shortcomings of the prior art. The method of the present invention combines electrodeposition with alkali-assisted oxidation to solve the problems of low separation efficiency, poor stability and complex preparation process of the oil-water separation membrane in the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing an oil-water separation membrane for oilfield fracturing flowback fluid, comprising the following steps:

[0009] 1) Using a copper plate as an anode and a copper mesh as a cathode, electrochemical deposition is performed in an electrolyte solution using a double-electrode system to obtain a copper mesh with deposited copper particles;

[0010] 2) The copper mesh with deposited copper particles is immersed in an alkaline oxidizing solution to obtain an oil-water separation membrane. Step 2) The alkaline oxidizing solution is a mixture of NaOH, (NH4)2S2O8 and water.

[0011] Preferably, the copper plate in step 1) is obtained by polishing the surface of the copper plate with sandpaper;

[0012] The copper mesh is a pretreated copper mesh, and the pretreatment process is: the original copper mesh is immersed in dilute acid, anhydrous ethanol, and water in sequence for ultrasonic treatment, and the ultrasonic treatment time in the dilute acid, anhydrous ethanol, and water is independently 8 to 12 minutes; the dilute acid is dilute hydrochloric acid or dilute nitric acid.

[0013] Preferably, the copper plate and the copper mesh are of the same size; the mesh number of the copper mesh is 450-550 meshes.

[0014] Preferably, the electrolyte solution in step 1) is a mixture of CuSO4, H2SO4 and water, wherein the concentration of CuSO4 in the electrolyte solution is 0.6-0.65 mol / L, and the concentration of H2SO4 is 0.48-0.52 mol / L.

[0015] Preferably, the electrochemical deposition time in step 1) is 2 to 3 hours, and the current intensity is 0.34 to 0.38A.

[0016] Preferably, in step 1), the distance between the anode and cathode is 1.4-1.6 cm, and the area of ​​the anode and cathode is 3 cm×3 cm.

[0017] Preferably, in the alkaline oxidizing solution in step 2), the concentration of NaOH is 2.3-2.7 mol / L, and the concentration of (NH4)2S2O8 is 0.08-0.12 mol / L.

[0018] Preferably, the soaking treatment time in step 2) is 10 to 40 minutes.

[0019] The present invention also provides the oil-water separation membrane for oilfield fracturing discharge fluid prepared by the preparation method of the oil-water separation membrane for oilfield fracturing discharge fluid.

[0020] The beneficial effects of the present invention include the following:

[0021] 1) The preparation method of the present invention is simple and efficient. It uses a two-step process of electrochemical deposition and alkali-assisted oxidation to quickly prepare a super-hydrophilic copper mesh (oil-water separation membrane). It is simple to operate, does not require complex equipment, and is suitable for large-scale preparation.

[0022] 2) The electrochemical deposition of the present invention plays a role in pre-roughening treatment, further removing the oxide scale, activating and coarsening the copper mesh skeleton, increasing the specific surface area of ​​the copper mesh, and significantly improving the membrane-base bonding strength; electrochemical deposition can coarsen the copper mesh skeleton, significantly increase the thickness of the skeleton, and reduce the pore size of the copper mesh, thereby achieving the dual purposes of enhancing the mechanical strength of the copper mesh and adjusting the pore size of the copper mesh to limit oil droplets.

[0023] 3) The small-sized emulsion oil-water separation membrane of the present invention has excellent oil-water separation efficiency. After alkali-assisted oxidation treatment, its surface forms a super-hydrophilic structure, which can quickly adsorb water and repel oil, achieving efficient oil-water separation. The separation efficiency can reach more than 95%, and it is suitable for oily wastewater treatment.

[0024] 4) The small-sized emulsion oil-water separation membrane of the present invention has a high permeation flux. Its porous structure and super-hydrophilic surface significantly improve the water passing efficiency, and the permeation flux can reach 5000L / (m 2 h) and above, suitable for efficient oil-water separation and filtration.

[0025] 5) The small-scale emulsion oil-water separation membrane of the present invention exhibits excellent stability. After alkali-assisted oxidation treatment, the copper mesh surface forms a stable super-hydrophilic structure, which can withstand multiple cycles of use. Experiments have shown that its oil-water separation efficiency and permeation flux remain stable over long-term use, making it suitable for practical industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A device for performing oil-water separation using the oil-water separation membrane prepared by the present invention;

[0027] Figure 2 The XRD spectra of the pretreated copper mesh and oil-water separation membrane of Example 1;

[0028] Figure 3 These are SEM images of the copper mesh with deposited copper particles and the oil-water separation membrane surface of Example 1, wherein a) and b) are copper mesh with deposited copper particles, and c) and d) are oil-water separation membranes;

[0029] Figure 4 SEM images of the oil-water separation membranes of Examples 1-2 and Comparative Examples 3-4 at different times in an alkaline oxidizing solution, wherein a) is Example 1, b) is Example 2, c) is Comparative Example 3, and d) is Comparative Example 4;

[0030] Figure 5SEM images of the oil-water separation membranes of Example 1 and Comparative Example 3 at different times in an alkaline oxidizing solution, wherein a) and b) are from Example 1, and c) and d) are from Comparative Example 3;

[0031] Figure 6 are the contact angles of the copper mesh and the oil-water separation membrane of Example 1 with water and oil, wherein a is the contact angle of the copper mesh with water, b is the contact angle of the oil-water separation membrane with water, c is the contact angle of the copper mesh with oil, and d is the contact angle of the oil-water separation membrane with oil;

[0032] Figure 7 The separation capacity of the small-sized emulsion oil-water separation membranes prepared in Example 1 and Comparative Examples 1-2 for oil-water emulsions, wherein a is Comparative Example 1, b is Comparative Example 2, and c is Example 1;

[0033] Figure 8 These are the results of 10 stability tests on the small-sized emulsion oil-water separation membrane prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing an oil-water separation membrane for oilfield fracturing flowback fluid, comprising the following steps:

[0035] 1) Using a copper plate as an anode and a copper mesh as a cathode, electrochemical deposition is performed in an electrolyte solution using a double-electrode system to obtain a copper mesh with deposited copper particles;

[0036] 2) soaking the copper mesh with the deposited copper particles in an alkaline oxidizing solution to obtain an oil-water separation membrane;

[0037] Step 2) The alkaline oxidizing solution is a mixture of NaOH, (NH4)2S2O8 and water.

[0038] In the present invention, the copper plate in step 1) is preferably cut into a suitable size, and polished evenly and vigorously along a single direction (such as horizontally or vertically) with 200-grit sandpaper until the oxide layer is completely removed, revealing the copper plate with a metallic luster;

[0039] The copper mesh is preferably a pretreated copper mesh, and the pretreatment process is preferably: immersing the original copper mesh in dilute acid, anhydrous ethanol, and water in sequence for ultrasonic treatment, the ultrasonic treatment using an ultrasonic cleaning machine, the ultrasonic treatment power is preferably 75-85W, more preferably 80W, the frequency is preferably 35-45kHz, more preferably 40kHz, and the time for ultrasonic treatment in dilute acid, anhydrous ethanol, and water is independently preferably 8-12min, more preferably 9-11min, and more preferably 10min; the dilute acid is preferably dilute hydrochloric acid or dilute nitric acid, and the concentration of the dilute acid is preferably 0.1-1.0mol / L, more preferably 0.3-0.7mol / L, and more preferably 0.5mol / L.

[0040] In the present invention, the original copper mesh is immersed in dilute acid, anhydrous ethanol and water in sequence for ultrasonic treatment and the copper plate is polished with sandpaper in order to remove oil stains, impurities and oxide layers on the surfaces of the copper mesh and the copper plate.

[0041] In the present invention, the copper plate and the copper mesh have the same size; the sizes of the copper plate and the copper mesh can be cut or tailored according to actual needs; the mesh number of the copper mesh is preferably 450 to 550 meshes, and more preferably 500 meshes.

[0042] In the present invention, the electrolyte solution in step 1) is preferably a mixture of CuSO4, H2SO4 and water. In the electrolyte solution, the concentration of CuSO4 is preferably 0.6-0.65 mol / L, more preferably 0.61-0.64 mol / L, more preferably 0.625-0.63 mol / L, and the concentration of H2SO4 is preferably 0.48-0.52 mol / L, more preferably 0.49-0.51 mol / L, more preferably 0.5 mol / L.

[0043] In the present invention, the time of the electrochemical deposition in step 1) is preferably 2 to 3 hours, more preferably 2.2 to 2.8 hours, more preferably 2.5 hours, and the current intensity is preferably 0.34 to 0.38 A, more preferably 0.35 to 0.37 A, more preferably 0.36 A.

[0044] In the present invention, the distance between the anode and cathode in step 1) is preferably 1.4 to 1.6 cm, more preferably 1.45 to 1.55 cm, and more preferably 1.5 cm. The area of ​​the anode and cathode is preferably 3 cm×3 cm.

[0045] In the present invention, in the alkaline oxidizing solution in step 2), the concentration of NaOH is preferably 2.3-2.7 mol / L, more preferably 2.4-2.6 mol / L, more preferably 2.5 mol / L, and the concentration of (NH4)2S2O8 is preferably 0.08-0.12 mol / L, more preferably 0.09-0.11 mol / L, more preferably 0.1 mol / L.

[0046] In the present invention, the soaking treatment time in step 2) is preferably 10 to 40 minutes, more preferably 20 to 30 minutes, and even more preferably 25 minutes.

[0047] In the present invention, after the soaking treatment in step 2) is completed, washing and drying are carried out in sequence to obtain an oil-water separation membrane; the oil-water separation membrane is a super-hydrophilic copper mesh.

[0048] The present invention also provides the oil-water separation membrane for oilfield fracturing discharge fluid prepared by the preparation method of the oil-water separation membrane for oilfield fracturing discharge fluid.

[0049] The oil-water separation membrane of the present invention can be used for oil-water separation of oily wastewater and oil-water separation of small-sized emulsions of oilfield fracturing reverse flow fluid.

[0050] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] In the embodiment, the mesh number of the copper mesh is 500 meshes, and the copper mesh is a brass mesh.

[0052] Example 1

[0053] The copper mesh was cut into 7cm×3cm rectangles and ultrasonically treated in dilute hydrochloric acid (concentration of 0.5mol / L), anhydrous ethanol, and deionized water in sequence using an ultrasonic cleaning machine. The ultrasonic treatment power was 80W and the frequency was 40kHz. The ultrasonic treatment time in dilute hydrochloric acid, anhydrous ethanol, and deionized water was 10 minutes each to remove oil, impurities, and oxides on the surface of the copper mesh; a 0.5mm thick copper plate was cut into 7cm×3cm rectangles, and the surface of the copper plate was evenly polished in a single direction (horizontally) with 200-grit sandpaper to remove oil, impurities, and oxides on the surface of the copper plate until the oxide layer was completely removed and the metallic luster was exposed.

[0054] The polished copper plate was used as the anode, and the pretreated copper mesh was used as the cathode. The distance between the anode and the cathode was fixed at 1.5 cm, and the area of ​​the anode and the cathode was 3 cm × 3 cm. A double-electrode system was used for electrochemical deposition of copper in an electrolyte solution consisting of CuSO4, H2SO4 and deionized water. The concentration of CuSO4 was 0.625 mol / L, and the concentration of H2SO4 was 0.5 mol / L. Electrochemical deposition was carried out for 2 h at a current intensity of 0.36 A to obtain a copper mesh with deposited copper particles.

[0055] The copper mesh with deposited copper particles was immersed in an alkaline oxidizing solution composed of NaOH, (NH4)2S2O8 and deionized water. The concentration of NaOH was 2.5 mol / L and the concentration of (NH4)2S2O8 was 0.1 mol / L. After immersion in the alkaline oxidizing solution for 30 minutes, the copper mesh was washed with deionized water and then dried at room temperature to obtain a small-sized emulsion oil-water separation membrane.

[0056] Example 2

[0057] The immersion treatment in the alkaline oxidizing solution was 40 minutes, and other process conditions were the same as those in Example 1.

[0058] Example 3

[0059] The distance between the anode and the cathode was fixed at 1.45 cm. The electrolyte solution consisted of CuSO4, H2SO4 and deionized water. The concentration of CuSO4 was 0.6 mol / L and the concentration of H2SO4 was 0.48 mol / L. Electrochemical deposition was carried out at a current intensity of 0.35 A for 2.5 h to obtain a copper mesh with deposited copper particles.

[0060] The alkaline oxidizing solution consists of NaOH, (NH4)2S2O8 and deionized water. The concentration of NaOH is 2.3 mol / L, and the concentration of (NH4)2S2O8 is 0.08 mol / L. After soaking in the alkaline oxidizing solution for 25 minutes, the copper mesh is washed with deionized water.

[0061] Other process conditions are the same as those in Example 1.

[0062] Example 4

[0063] The distance between the anode and the cathode was fixed at 1.55 cm. The electrolyte solution consisted of CuSO4, H2SO4 and deionized water. The concentration of CuSO4 was 0.65 mol / L and the concentration of H2SO4 was 0.52 mol / L. Electrochemical deposition was carried out at a current intensity of 0.38 A for 1.5 h to obtain a copper mesh with deposited copper particles.

[0064] The alkaline oxidizing solution consists of NaOH, (NH4)2S2O8 and deionized water. The concentration of NaOH is 2.7 mol / L, and the concentration of (NH4)2S2O8 is 0.12 mol / L. After soaking in the alkaline oxidizing solution for 20 minutes, the copper mesh is washed with deionized water.

[0065] Other process conditions are the same as those in Example 1.

[0066] Comparative Example 1

[0067] The electrochemical deposition time was 1 h, and other process conditions were the same as those in Example 1.

[0068] Comparative Example 2

[0069] The electrochemical deposition time was 1.5 h, and other process conditions were the same as those in Example 1.

[0070] Comparative Example 3

[0071] The immersion treatment in the alkaline oxidizing solution was 60 minutes, and other process conditions were the same as those in Example 1.

[0072] Comparative Example 4

[0073] The immersion treatment in the alkaline oxidizing solution was 90 minutes, and other process conditions were the same as those in Example 1.

[0074] The oil-water separation device prepared by the present invention is as follows: Figure 1 shown.

[0075] The performance tests were conducted on the oil-water separation membranes of Examples 1-2 and Comparative Examples 1-4.

[0076] (1) Composition analysis: The surface of the oil-water separation membrane of Example 1 was characterized by an X-ray diffractometer (XRD, Bruker D8 Advance) to analyze the composition of the material surface.

[0077] The XRD spectra of the pretreated copper mesh and oil-water separation membrane of Example 1 are as follows: Figure 2 As shown, Cu(OH)2 refers to Cu(OH)2 / Cu, which is represented by Figure 2 It can be seen that the XRD spectrum of Cu shows obvious strong diffraction peaks at 2θ=43.259°, 50.466°, and 74.256°, corresponding to JCDF card 70-3038, which is a Cu crystal structure; the XRD spectrum of Cu(OH)2 / Cu shows diffraction peaks at 2θ=16.597°, 23.804°, 34.046°, and 39.790°, corresponding to JCPDF card 35-0505, which is an orthorhombic structure of Cu(OH)2, proving that the geometrically asymmetric structure of the copper mesh film surface is Cu(OH)2.

[0078] (2) Scanning electron microscopy analysis: The surface morphology of the copper mesh with deposited copper particles and the oil-water separation membrane of Example 1 was observed using a scanning electron microscope (SEM, ZEISS Merlin).

[0079] The SEM images of the copper mesh and the oil-water separation membrane surface on which the copper particles were deposited in Example 1 are shown in FIG. Figure 3 As shown, a) and b) are copper meshes with deposited copper particles, c) and d) are oil-water separation membranes. Figure 3 The surface of the copper mesh where copper particles were deposited showed copper particle protrusions of varying sizes (Figure b). The curved copper wire surface exhibited more copper particles due to the relatively high current density on the exposed curved wire, resulting in a greater amount of copper deposition (Figure a). A rough nanowire structure formed on the surface of the oil-water separation membrane (Figure d), indicating the formation of an asymmetric geometric structure on the metal substrate.

[0080] The SEM images of the oil-water separation membranes of Examples 1-2 and Comparative Examples 3-4 at different times in the alkaline oxidizing solution are shown in FIG. Figure 4 As shown, wherein a) is Example 1, b) is Example 2, c) is Comparative Example 3, d) is Comparative Example 4, Figure 4It can be seen that after 2 h of electrochemical deposition, as the alkali-assisted oxidation time increases, the nanowires become longer, but the structure also changes accordingly.

[0081] The SEM images of the oil-water separation membranes of Example 1 and Comparative Example 3 at different times in the alkaline oxidizing solution are shown in FIG. Figure 5 As shown, a) and b) are Example 1, c) and d) are Comparative Example 3. From Figure b), it can be seen that the nanowire structure is needle-shaped, and from Figure d), it can be seen that the nanowire structure is flower bud-shaped. The flower bud-shaped structure is not conducive to wettability, and a long alkali-assisted oxidation time will reduce the wettability.

[0082] (3) Surface wettability analysis

[0083] The contact angles of the copper mesh and oil-water separation membrane of Example 1 with water and oil are as follows: Figure 6 As shown, a is the contact angle between the copper mesh and water, b is the contact angle between the oil-water separation membrane and water, c is the contact angle between the copper mesh and oil, and d is the contact angle between the oil-water separation membrane and oil. Figure 6 It can be seen that the water contact angle decreases from 105° on the copper mesh surface to 0° on the oil-water separation membrane surface, and the oil-water separation membrane exhibits superhydrophilicity. The underwater oil contact angle increases from 113° on the copper mesh surface to 148° on the oil-water separation membrane surface, and the oil-water separation membrane exhibits superoleophobicity. The analysis shows that a layer of hydrophilic and oleophobic surface synergistic structure is effectively established on the surface of the copper mesh membrane.

[0084] (4) Oil-water emulsion separation test: 0.03 g of sodium dodecylbenzenesulfonate, 3 mL of toluene dyed with 0.01 g of Sudan red, and 90 mL of deionized water were placed in a container and stirred at a rate of 1000 r / min for 30 min using a magnetic stirrer to prepare a slightly orange uniform oil-in-water emulsion.

[0085] The separation ability of the small-sized emulsion oil-water separation membrane prepared in Example 1 and Comparative Examples 1-2 for oil-water emulsion is as follows: Figure 7 As shown, a is comparative example 1, b is comparative example 2, and c is embodiment 1. The results show that the brass mesh subjected to alkali-assisted oxidation for 30 minutes and electrodeposition for 1 hour and 1.5 hours did not achieve oil-water separation, while the brass mesh subjected to electrodeposition for 2 hours achieved an oil removal rate of 96% for the emulsion system.

[0086] (5) Stability test

[0087] In practical oil-water separation, the stability of the oil-water separation membrane is equally important. After each oil-water emulsion separation experiment (using the same method as the oil-water emulsion separation test), the small-scale emulsion oil-water separation membrane prepared in Example 1 was rinsed on both sides for 1 minute using an ethanol wash bottle. The copper mesh was then rinsed on both sides for 1 minute using a distilled water wash bottle. After drying, the oil-water emulsion separation experiment was repeated. The removal rate of the filtrate obtained after each test was measured.

[0088] The results of 10 stability tests of the small-sized emulsion oil-water separation membrane prepared in Example 1 are as follows: Figure 8 The results show that the brass mesh that has been electroplated for 2 hours and then oxidized for 30 minutes with alkali has good stability in oil removal rate for the emulsion system, and still has an oil removal rate of 95% after 10 times of use and cleaning.

[0089] The present invention uses a high-mesh copper mesh as a substrate and adopts a method of electrochemical copper deposition combined with alkali-assisted oxidation to prepare a copper-based oil-water separation membrane with copper hydroxide nanowires grown thereon; the oil-water separation membrane material prepared by the present invention has excellent superhydrophilicity in the air, and water droplets in the air can quickly spread out on the membrane surface; it has excellent oleophobicity underwater, and the underwater membrane surface can quickly repel oil droplets. The copper-based oil-water separation membrane is used for oil-water separation performance testing of ordinary oil-water mixtures and oil-water emulsions. The test results show that the special wetting properties of the oil-water separation membrane of the present invention can achieve the purpose of oil-water separation with different emulsification degrees. By changing the preparation conditions of the oil-water separation membrane, not only can the separation of simple oil-water mixtures be achieved, but also the demulsification separation of water-in-oil emulsions can be satisfied. During the separation process, the oil-water separation membrane exhibits excellent oil-water separation performance. At the same time, the oil-water separation membrane material is easy to clean and has excellent application value.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an oil-water separation membrane for oilfield fracturing backflow fluid, characterized in that: The following steps are included: 1) Using a copper plate as an anode and a copper mesh as a cathode, electrochemical deposition is performed in an electrolyte solution using a double-electrode system to obtain a copper mesh with deposited copper particles; 2) soaking the copper mesh with the deposited copper particles in an alkaline oxidizing solution to obtain an oil-water separation membrane; Step 2) The alkaline oxidizing solution is a mixture of NaOH, (NH4)2S2O8 and water.

2. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 1, characterized in that: Step 1) The copper plate is obtained by polishing the surface of the copper plate with sandpaper; The copper mesh is a pretreated copper mesh, and the pretreatment process is: the original copper mesh is immersed in dilute acid, anhydrous ethanol, and water in sequence for ultrasonic treatment, and the ultrasonic treatment time in the dilute acid, anhydrous ethanol, and water is independently 8 to 12 minutes; the dilute acid is dilute hydrochloric acid or dilute nitric acid.

3. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 1 or 2, characterized in that: The copper plate and the copper mesh have the same size; the mesh number of the copper mesh is 450-550 meshes.

4. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 1, characterized in that: Step 1) The electrolyte solution is a mixture of CuSO4, H2SO4 and water, wherein the concentration of CuSO4 in the electrolyte solution is 0.6-0.65 mol / L, and the concentration of H2SO4 is 0.48-0.52 mol / L.

5. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 1 or 4, characterized in that: The electrochemical deposition time in step 1) is 2 to 3 hours, and the current intensity is 0.34 to 0.38A.

6. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 5, characterized in that: In step 1), the distance between the anode and the cathode is 1.4 to 1.6 cm, and the area of ​​the anode and the cathode is 3 cm×3 cm.

7. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 5, characterized in that: In step 2), the concentration of NaOH in the alkaline oxidizing solution is 2.3-2.7 mol / L, and the concentration of (NH4)2S2O8 is 0.08-0.12 mol / L.

8. The method for preparing an oil-water separation membrane for oilfield fracturing drainage according to claim 6 or 7, characterized in that: The soaking time in step 2) is 10 to 40 minutes.

9. The oil-water separation membrane for oilfield fracturing flowback fluid prepared by the method for preparing the oil-water separation membrane for oilfield fracturing flowback fluid according to any one of claims 1 to 8.

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