Polyethyleneimine modified graphene oxide composite material, and preparation method and application thereof

Abstract

The application relates to the field of oil exploitation, and discloses a polyethylene imine modified graphene oxide composite material, wherein the composite material comprises polyethylene imine and graphene oxide with multifunctional groups; the total content of hydroxyl and carboxyl contained in the graphene oxide is 4-6 wt%; and hydrogen bonds exist between nitrogen atoms of amino contained in the polyethylene imine and oxygen atoms in the graphene oxide. The polyethylene imine modified graphene oxide composite material provided by the application has excellent hydration inhibition performance, filtration reduction performance and temperature resistance when used as a shale inhibitor of a water-based drilling fluid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil exploitation, in particular to a polyethyleneimine modified graphene oxide composite material and a preparation method and application thereof. BACKGROUND

[0002] At present, the shale inhibitors commonly used in drilling fluids include inorganic salt shale inhibitors such as potassium chloride, and cationic ammonium salt shale inhibitors such as small cations and polyamines.

[0003] It is mentioned in “Graphene grafted with glucopyranose as a shale swelling inhibitor in water-based drilling mud” (Applied Clay Science) that the preparation process of glucopyranose grafted graphene (Glu-Gr) is complex and requires many raw materials. In order to prepare glucopyranose grafted graphene, graphene oxide nanosheets are first reacted with SOCl2 to obtain acyl chloride functionalized graphene oxide. Then, CH2OH-terminated glucopyranose and acyl chloride functionalized graphene oxide are reacted by condensation to obtain the final product Glu-Gr.

[0004] It is mentioned in “Graphene grafted with polyethyleneimine for enhanced shale inhibition in the water-based drilling fluid” (Environmental Nanotechnology, Monitoring & Management) that the preparation process of polyethyleneimine grafted graphene (PEI-Gr) is complex and time-consuming, and requires many raw materials. The reducing agent used is hydrogen peroxide. The solvent used to prepare the final product is tetrahydrofuran, and the reaction needs to be carried out under the action of a catalyst for 2 days.

[0005] The above shale inhibitors have the disadvantages of large addition amount, serious environmental pollution, weak temperature resistance, weak filtration loss reduction performance and hydration inhibition performance, etc. Therefore, it is necessary to develop shale inhibitors with more excellent performance. SUMMARY

[0006] The present application relates to the field of oil exploitation, in particular to a polyethyleneimine modified graphene oxide composite material and a preparation method and application thereof.

[0007] To achieve the above object, the polyethyleneimine modified graphene oxide composite material according to the first aspect of the present application comprises: polyethyleneimine and graphene oxide with multifunctional groups; the total content of hydroxyl and carboxyl contained in the graphene oxide is 4-6 wt%; and there is a hydrogen bond between the nitrogen atom of the amino contained in the polyethyleneimine and the oxygen atom in the graphene oxide.

[0008] The second aspect of the present application provides a preparation method of the polyethyleneimine modified graphene oxide composite material, which comprises:

[0009] (1) performing an oxidation reaction on single-layer graphite and an oxidizing agent, and then performing a reduction reaction on the obtained product with a reducing agent to obtain graphene oxide;

[0010] (2) performing a reaction on the graphene oxide and polyethyleneimine to obtain the composite material;

[0011] The mass ratio of the reducing agent to the single-layer graphite is 1-1.5:100.

[0012] The third aspect of the present application provides the polyethyleneimine modified graphene oxide composite material obtained by the preparation method.

[0013] The fourth aspect of the present application provides an application of the polyethyleneimine modified graphene oxide composite material as a shale inhibitor for water-based drilling fluid.

[0014] Through the above technical solution, the polyethyleneimine modified graphene oxide composite material provided by the present application has excellent inhibition hydration performance, filtration reduction performance and temperature resistance when used as a shale inhibitor for water-based drilling fluid. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the infrared spectrum of the polyethyleneimine modified graphene oxide composite material of Example 1;

[0016] Figure 2 is the rolling recovery rate of XC, GO1 / XC, S1 / XC, S2 / XC, S3 / XC, S4 / XC, S5 / XC, S6 / XC, D1 / XC and D2 / XC. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values should be understood to be approximate. The exact numerical values should be considered to be an approximation within the context of the range or value. The endpoints of the ranges of values and the individual values are not to be construed as being limited to the exact values recited as endpoints or middle points. The exact numerical values should be considered to be an approximation within the context of the range or value.

[0018] The polyethyleneimine-modified graphene oxide composite material of the present application comprises: polyethyleneimine and graphene oxide having multifunctional groups; the total content of hydroxyl and carboxyl groups contained in the graphene oxide is 4-6 wt%; and hydrogen bonds exist between the nitrogen atoms of the amino groups contained in the polyethyleneimine and the oxygen atoms in the graphene oxide.

[0019] In the present application, the multifunctional groups of the graphene oxide are selected from hydroxyl and / or carboxyl groups. The composite material contains oxygen-containing functional groups in the graphene oxide, and the oxygen atoms in the oxygen-containing functional groups can form hydrogen bonds with the nitrogen atoms of the amino groups contained in the polyethyleneimine, so that the composite material has excellent hydration inhibition performance, fluid loss reduction performance and temperature resistance. The polyethyleneimine has a hyperbranched structure, the branching degree of the polyethyleneimine is 30-35%, and the polyethyleneimine can be commercially available. The contact points between the polyethyleneimine and the graphene oxide are increased, and hydrogen bonds exist between the amino groups contained in the polyethyleneimine and the oxygen atoms in the oxygen-containing functional groups (hydroxyl and carboxyl groups) in the graphene oxide. When the total content of the hydroxyl and carboxyl groups contained in the graphene oxide is in the range of 4-6 wt%, the polyethyleneimine-modified graphene oxide composite material has excellent hydration inhibition performance, fluid loss reduction performance and temperature resistance.

[0020] In some embodiments of the present application, the weight average molecular weight of the polyethyleneimine is 5000-15000 g / mol. When the weight average molecular weight of the polyethyleneimine is in this range, the polyethyleneimine contains more amino sites, and the contact points between the polyethyleneimine and the graphene oxide are increased, so that the obtained polyethyleneimine-modified graphene oxide composite material has excellent hydration inhibition performance, fluid loss reduction performance and temperature resistance.

[0021] In some embodiments of the present application, the mass ratio of the polyethyleneimine to the graphene oxide in the composite material is 2-10:1. When the mass ratio is less than 2:1, there is a problem that the polyethyleneimine in the composite material is too little to provide too few amino groups for chemical hydration inhibition. When the mass ratio is greater than 10:1, there is a problem that too much polyethyleneimine in the composite material fails to be compounded with the graphene oxide, and the hydration inhibition reaches saturation. Therefore, when the mass ratio of the polyethyleneimine to the graphene oxide is 2-10:1, the polyethyleneimine-modified graphene oxide composite material has excellent hydration inhibition performance. The mass ratio of the polyethyleneimine to the graphene oxide is preferably 9-10:1, so that the polyethyleneimine-modified graphene oxide composite material has excellent hydration inhibition performance, fluid loss reduction performance and temperature resistance.

[0022] In some embodiments of the present application, the hydration inhibition performance of the composite material is that the swelling height caused by the water absorption hydration of bentonite is reduced by 50-55% by the composite material with a concentration of 0.4 wt%, and the composite material has excellent hydration inhibition performance.

[0023] The second aspect of the present application provides a preparation method of a polyethyleneimine modified graphene oxide composite material, wherein the method comprises:

[0024] (1) performing an oxidation reaction on single-layer graphite and an oxidizing agent, and then performing a reduction reaction on the obtained product and a reducing agent to obtain graphene oxide;

[0025] (2) performing a reaction on the graphene oxide and polyethyleneimine to obtain the composite material;

[0026] The mass ratio of the reducing agent to the single-layer graphite is 1-1.5:100.

[0027] In some embodiments of the present application, in step (1), before the oxidation reaction, the graphite is first peeled off with concentrated sulfuric acid to obtain single-layer graphite, and the weight ratio of the graphite to the concentrated sulfuric acid is 1:35-38.

[0028] In some embodiments of the present application, in step (1), the oxidizing agent is selected from one or more of sodium nitrate, potassium permanganate, and nitric acid.

[0029] In some embodiments of the present application, the reducing agent is selected from hydrazine hydrate.

[0030] In some embodiments of the present application, relative to 100 parts by weight of the graphite, the oxidizing agent is 200-400 parts by weight, and the reducing agent is 1-1.5 parts by weight.

[0031] In some embodiments of the present application, the temperature of the oxidation reaction is 90-95℃, and the time of the oxidation reaction is 1.5-2h.

[0032] In some embodiments of the present application, the temperature of the reduction reaction is 20-30℃, and the time of the reduction reaction is 20-30min.

[0033] In some embodiments of the present application, the reaction temperature is 60-80℃, and the reaction time is 6-8h.

[0034] In some embodiments of the present application, the mass ratio of the polyethyleneimine to the graphene oxide is 2-10:1, preferably 9-10:1.

[0035] In some embodiments of the present application, in step (2), the graphene oxide is dissolved in water before the reaction, and the concentration of the graphene oxide in water is 0.5-2 wt%.

[0036] The third aspect of the present application provides a polyethyleneimine modified graphene oxide composite prepared by the method.

[0037] The fourth aspect of the present application provides an application of the polyethyleneimine modified graphene oxide composite as a shale inhibitor for water-based drilling fluid.

[0038] The present application will be described in detail below by way of examples.

[0039] The expansion height was measured by a linear dilatometer, and the test method was shown in Test Example 1.

[0040] The API (mL) was measured by a filter loss instrument according to the API specification and the Chinese SY / T5621-93 standard.

[0041] The total content of hydroxyl and carboxyl groups in the graphene oxide was measured by Boehm titration.

[0042] The linear dilatometer was manufactured by Qingdao Haitongda, and the model was CPZ-2.

[0043] The filter loss instrument was manufactured by Qingdao Bairuida, and the model was ZNZ-S5.

[0044] The high-temperature roller furnace was manufactured by Qingdao Haitongda, and the model was BGRL-5.

[0045] In the following examples and comparative examples, the specific conditions not mentioned were carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned the manufacturer were conventional products that can be obtained by market purchase.

[0046] Preparation Example 1: Preparation of graphene oxide

[0047] To 120 mL of concentrated sulfuric acid (98.3 wt% concentration) (0 °C), 6 g of graphite powder (325 mesh) was added with stirring until fully dissolved, followed by the addition of 3 g of NaNO3. After the NaNO3 was fully dissolved, 15 g of KMnO4 was slowly added with stirring and the temperature was kept below 20 °C using an ice bath system. The mixture was stirred at 35 °C for 2 h, then diluted with 250 mL of deionized water, keeping the temperature below 50 °C using an ice bath system during dilution. After dilution was complete, the mixture was stirred for 2 h, then warmed to 90 °C for 15 min. The solution was then poured into 700 mL of deionized water and allowed to cool to room temperature. 0.06 mL of hydrazine hydrate was slowly added to give a golden yellow liquid. The solution was left to stand overnight, the supernatant was removed, and the lower layer was centrifuged at 8000 rpm for 20 min. The precipitate was washed with hydrochloric acid at a volume ratio of 1 : 10, then washed with deionized water three times, and the washing was repeated three times or more until the solution pH was neutral. The obtained solution was dialyzed using a dialysis bag with a molecular weight cut-off of 3500 for 2 weeks. The water was changed two or more times per day. The dialyzed solution was freeze-dried to obtain weakly reduced graphene oxide GO1.

[0048] wherein the total content of hydroxyl and carboxyl groups in the graphene oxide GO1 is 6 wt%.

[0049] Preparation Example 2: Preparation of graphene oxide

[0050] To 120 mL of concentrated sulfuric acid (98.3 wt% concentration) (0 °C), 6 g of graphite powder (325 mesh) was added with stirring until fully dissolved, followed by the addition of 3 g of NaNO3. After the NaNO3 was fully dissolved, 15 g of KMnO4 was slowly added with stirring and the temperature was kept below 20 °C using an ice bath system. The mixture was stirred at 35 °C for 2 h, then diluted with 250 mL of deionized water, keeping the temperature below 50 °C using an ice bath system during dilution. After dilution was complete, the mixture was stirred for 2 h, then warmed to 90 °C for 15 min. The solution was then poured into 700 mL of deionized water and allowed to cool to room temperature. 0.06 mL of hydrazine hydrate was slowly added to give a golden yellow liquid. The solution was left to stand overnight, the supernatant was removed, and the lower layer was centrifuged at 8000 rpm for 20 min. The precipitate was washed with hydrochloric acid at a volume ratio of 1 : 10, then washed with deionized water three times, and the washing was repeated three times or more until the solution pH was neutral. The obtained solution was dialyzed using a dialysis bag with a molecular weight cut-off of 3500 for 2 weeks. The water was changed two or more times per day. The dialyzed solution was freeze-dried to obtain weakly reduced graphene oxide GO1.

[0051] wherein the total content of hydroxyl and carboxyl groups in the graphene oxide GO2 is 4 wt%.

[0052] Comparative Preparation Example 1: Preparation of graphene oxide

[0053] To 120 mL of concentrated sulfuric acid (98.3 wt% concentration) at 0 °C, 6 g of graphite powder (325 mesh) was added with stirring until fully dissolved. Then 3 g of NaNO3 was added. After the NaNO3 was fully dissolved, 15 g of KMnO4 was added slowly with stirring and the temperature was kept below 20 °C using an ice bath system. The mixture was stirred at 35 °C for 2 h, then diluted with 250 mL of deionized water while keeping the temperature below 50 °C using an ice bath system. After the dilution was complete, the mixture was stirred for 2 h and then warmed to 90 °C for 15 min. The solution was then poured into 700 mL of deionized water and cooled to room temperature. 0.5 mL of hydrazine hydrate was added slowly to obtain a golden yellow liquid. It was left to stand overnight, the supernatant was removed, and the lower liquid was centrifuged at 8000 rpm for 20 min. The precipitate was washed with hydrochloric acid at a volume ratio of 1 : 10, and then washed with deionized water three times. The washing operation was repeated three times until the solution pH was neutral. The obtained solution was dialyzed using a dialysis bag with a molecular weight cut-off of 3500 for 2 weeks. The water was changed more than twice a day. The dialyzed solution was freeze-dried to obtain graphene oxide GO3;

[0054] wherein the total content of the hydroxyl and carboxyl groups in the graphene oxide GO3 is 1 wt%.

[0055] Example 1

[0056] In 99 mL of deionized water, 1 g of graphene oxide GO1 obtained in Preparation Example 1 was added, and a GO1 solution with a concentration of 1 wt% was prepared by ultrasonic treatment for 30 minutes. 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching 35%, molecular weight 10000 g / mol) was added to the GO1 solution according to a mass ratio of polyethyleneimine to graphene oxide of 10: 1. The solution was stirred at 80 °C for 6 hours to obtain a black opaque polyethyleneimine modified graphene oxide composite material, denoted as S1.

[0057] Example 2

[0058] In 99 mL of deionized water, 1 g of graphene oxide GO2 obtained in Preparation Example 2 was added, and a GO2 solution with a concentration of 1 wt% was prepared by ultrasonic treatment for 30 minutes. 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching 35%, molecular weight 10000 g / mol) was added to the GO2 solution according to a mass ratio of polyethyleneimine to graphene oxide of 10: 1. The solution was stirred at 80 °C for 6 hours to obtain a black opaque polyethyleneimine modified graphene oxide composite material, denoted as S2.

[0059] Example 3

[0060] In 99 ml of deionized water, 1 g of graphene oxide GO1 obtained in Preparation Example 1 was added to prepare a GO1 solution having a concentration of 1 wt% by ultrasonic treatment for 30 minutes; 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching of 35%, molecular weight of 5000 g / mol) was added to the GO1 solution in a mass ratio of 10:1 of polyethyleneimine to graphene oxide; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine-modified graphene oxide composite material, which was designated as S3.

[0061] Example 4

[0062] In 99 ml of deionized water, 1 g of graphene oxide GO1 obtained in Preparation Example 1 was added to prepare a GO1 solution having a concentration of 1 wt% by ultrasonic treatment for 30 minutes; 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching of 35%, molecular weight of 1800 g / mol) was added to the GO1 solution in a mass ratio of 10:1 of polyethyleneimine to graphene oxide; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine-modified graphene oxide composite material, which was designated as S4.

[0063] Example 5

[0064] In 99 ml of deionized water, 1 g of graphene oxide GO1 obtained in Preparation Example 1 was added to prepare a GO1 solution having a concentration of 1 wt% by ultrasonic treatment for 30 minutes; 5 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching of 35%, molecular weight of 10000 g / mol) was added to the GO1 solution in a mass ratio of 5:1 of polyethyleneimine to graphene oxide; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine-modified graphene oxide composite material, which was designated as S5.

[0065] Example 6

[0066] In 99 ml of deionized water, 1 g of graphene oxide GO1 obtained in Preparation Example 1 was added to prepare a GO1 solution having a concentration of 1 wt% by ultrasonic treatment for 30 minutes; 2 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching of 35%, molecular weight of 10000 g / mol) was added to the GO1 solution in a mass ratio of 2:1 of polyethyleneimine to graphene oxide; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine-modified graphene oxide composite material, which was designated as S6.

[0067] Comparative Example 1

[0068] In 99 mL of deionized water, 1 g of graphene oxide GO3 obtained from Comparative Preparation 1 was added, and a GO3 solution with a concentration of 1 wt% was prepared by ultrasonic treatment for 30 minutes; 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching 35%, molecular weight 10000 g / mol) was added to the GO3 solution according to a mass ratio of polyethyleneimine to graphene oxide of 10:1; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine modified graphene oxide composite material, denoted as D1.

[0069] Comparative Example 2

[0070] In 99 mL of deionized water, 1 g of graphene oxide GO4 obtained from Comparative Preparation 1 was added, and a GO4 solution with a concentration of 1 wt% was prepared by ultrasonic treatment for 30 minutes; 10 g of polyethyleneimine (PEI, hyperbranched structure, degree of branching 35%, molecular weight 10000 g / mol) was added to the GO4 solution according to a mass ratio of polyethyleneimine to graphene oxide of 10:1; the solution was stirred at 80°C for 6 hours to obtain a black opaque polyethyleneimine modified graphene oxide composite material, denoted as D2.

[0071] Structural characterization:

[0072] The polyethyleneimine modified graphene oxide composite material S1 was tested by infrared spectroscopy, and the results are shown in Figure 1 The mass of hydrogen atoms decreases after hydrogen bonding, causing the peak to shift to lower wavenumbers. In the spectrum of GO1 / bentonite, the stretching vibration peak of hydroxyl O-H was observed at 3468 cm -1 In the spectrum of S1 / bentonite, O-H was observed at 3414 cm -1 Red shift indicates the presence of hydrogen bonding between polyethyleneimine and graphene oxide.

[0073] Test Example 1: Evaluation of the inhibiting hydration performance of the composite material

[0074] The laboratory used a linear dilatometer to measure the swelling height of bentonite in deionized water and different inhibitor solutions over time. 5 g of bentonite was poured into a pressure tank, and a hydraulic machine was used to apply a pressure of 5 MPa for 10 minutes to form a soil block. After the linear dilatometer value was zeroed, the soil block was placed, and then the test was started and water and different concentrations of inhibitor solutions were injected to measure the swelling height of the bentonite over time, wherein the GO1, S1, S2, S3, S4, S5, S6, D1, D2 solution concentration was 0.4 wt%, and the KCl solution concentration was 4 wt%. The results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As shown in Table 1, in the study of linear expansion test, bentonite was hydrated in deionized water, 0.4wt% GO1, S1, S2, S3, S4, S5, S6, D1 and D2 solution, 4wt% KCl solution for 16 hours, which caused the expansion height of 5.82mm, 4.24mm, 2.74mm, 2.82mm, 2.91mm, 3.09mm, 3.01mm, 3.11mm, 2.92mm, 2.88mm and 2.96mm, respectively. The data showed that compared with deionized water, the expansion height caused by 0.4wt% concentration of S1 was reduced by 3.08mm, which was decreased by 52.9%, and the inhibition effect of hydration was excellent. At the same time, it can be observed that the inhibition performance of S1 is better than other graphene composites, graphene oxide GO1 and KCl, and the concentration of S1 is 1 / 10 of KCl. Compared with other graphene composites with the same concentration, the expansion height caused by S1 is reduced by 0.08-0.35mm. In addition to the role of plugging pores provided by graphene oxide as a nanomaterial, there are a large number of amino groups on the surface of S1, which are adsorbed on the clay surface and side by hydrogen bond and electrostatic adsorption, preventing water from invading, and S1 can significantly improve the inhibition of hydration capacity of GO. When the molecular weight of polyethyleneimine is 10000g / mol, the number of hydroxyl groups of graphene oxide GO2, GO3 and GO4 used in example 2, comparative example 1 and comparative example 2 is less than that of GO1, so the combination rate of graphene oxide and polyethyleneimine on S2, D1 and D2 obtained is lower, and the number of chemically inhibited hydration amino groups is less. When the graphene oxide used is graphene oxide GO1 obtained in preparation example 1, the molecular weight of polyethyleneimine used in example 3 and example 4 is different, so the number of amino groups provided by polyethyleneimine on S3 and S4 obtained is less, and the chemical inhibition of hydration capacity is lower. In examples 5 and 6, the content of polyethyleneimine is lower, and the number of amino groups provided is less, so the chemical inhibition of hydration capacity of S5 and S6 is lower.

[0078] Test Example 2: Evaluation of Anti-filtration performance of composite materials

[0079] Preparation of xanthan gum solution: 0.9g xanthan gum (XC) was poured into 300mL deionized water and stirred until XC was dissolved to prepare 0.3wt% XC solution, then 0.6g of different nanomaterials was poured into the XC solution and stirred to prepare 0.2wt% GO1, S1, nano-silica, amino-nano-silica, nano-zinc oxide, graphite powder solution, respectively. The change of filtration loss of GO1 and S1 solution within 30 minutes was measured by medium pressure filtration device, and the filtration loss of the rest of the nanomaterials after 30 minutes was tested. Polytrifluoroethylene membrane (220nm) was selected instead of filter paper to better simulate the size of shale pores. The measured filtration loss is shown in Table 2-3.

[0080] Table 2

[0081]

[0082] Table 3

[0083] Inhibitors GO1 S1 Nano-silica Amino nano-silica Nano-zinc oxide Graphite powder Spurt / mm 8.8 8.2 34.5 36 30.5 32

[0084] The filtration volume was used to evaluate the plugging capacity, the smaller the filtration volume, the better the plugging capacity. As shown in Table 2, the filtration loss growth curves of S1 solution and GO1 solution are similar, and the filtration loss of S1 solution is less than that of GO1 solution. The plugging process of GO1 and S1 is that the adsorption of graphene oxide and graphene composite material on the surface of filter paper or membrane forms a smooth film, which prevents water from passing through the filter paper or membrane. Compared with GO1 and S1 solution, no film is formed in other nanomaterial solutions, and a large number of aggregated microparticles are observed, which cannot form a tight filter cake due to aggregation. The plugging capacity of GO1 and S1 is much better than that of other inorganic nanomaterials. As shown in Table 3, under certain conditions, the filtration loss of drilling fluid added with S1 is the lowest compared with the rest of the nanomaterials, in which the filtration loss of GO1 and S1 is 8.8 mL and 8.2 mL respectively, which is similar to the filtration loss of commonly used filtration reducers. While the filtration volumes of other nanomaterials are 34.5 mL, 36 mL, 30.5 mL and 32 mL, indicating that part of the water has passed through the filter paper.

[0085] Test Example 3: Evaluation of High Temperature Resistance of Composite Material

[0086] The shale was crushed and sieved between 6-10 meshes. 20 g of shale debris was poured into an aging tank containing 300 mL of XC, GO1 / XC, S1 / XC, S2 / XC, S3 / XC, S4 / XC, S5 / XC, S6 / XC, D1 / XC and D2 / XC solution. The concentration of XC is 0.3wt%, and the concentration of GO1, S1, S2, S3, S4, S5, S6, D1D2 is 0.2wt%. The aging tank was placed in a high temperature rolling furnace at 120℃ for 16h hot rolling, 105℃ drying for 48h, and weighing after 40 mesh sieving. The mass of shale before hot rolling is denoted as W1, and the mass of shale after hot rolling is denoted as W2. The rolling recovery rate is calculated as follows: recovery rate = W2 / W1. The measured rolling recovery rate is shown in Table 4. Figure 2

[0087] As shown in Table 4, the rolling recovery rate of XC is 0.8, and the rolling recovery rate of GO1, S1, S2, S3, S4, S5, S6, D1 and D2 is 0.9, which is much higher than that of XC. The rolling recovery rate of XC is the lowest among the five groups of solutions, and the rolling recovery rate of GO1, S1, S2, S3, S4, S5, S6, D1 and D2 is the highest among the five groups of solutions. The rolling recovery rate of XC is the lowest among the five groups of solutions, and the rolling recovery rate of GO1, S1, S2, S3, S4, S5, S6, D1 and D2 is the highest among the five groups of solutions. Figure 2 ​As shown, the rolling recovery rates of XC, GO1 / XC, S1 / XC, S2 / XC, S3 / XC, S4 / XC, S5 / XC, S6 / XC, D1 / XC and D2 / XC are 36.24%, 37.27%, 74.56%, 72.91%, 70.21%, 66.15%, 68.55%, 65.78%, 70.92% and 69.02%. It is further shown that the inhibition ability of the graphene composite is still superior to that of graphene oxide under high temperature conditions, and the inhibition performance of S1 is superior to that of other composites.

[0088] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A polyethyleneimine-modified graphene oxide composite material, characterized in that, The composite material comprises: polyethyleneimine and graphene oxide with multiple functional groups; the total content of hydroxyl and carboxyl groups in the graphene oxide is 4-6 wt%; there is a hydrogen bond between the nitrogen atom of the amino group in the polyethyleneimine and the oxygen atom in the graphene oxide; the weight-average molecular weight of the polyethyleneimine is 10000-15000 g / mol. In the composite material, the mass ratio of polyethyleneimine to graphene oxide is 9-10:1; The method for preparing the composite material includes: (1) A single-layer graphite is oxidized with an oxidizing agent, and the product is then reduced with a reducing agent to obtain graphene oxide; (2) The graphene oxide and polyethyleneimine are reacted to obtain the composite material; The mass ratio of the reducing agent to monolayer graphite is 1-1.5:

100.

2. The composite material according to claim 1, characterized in that, The degree of branching of the polyethyleneimine is 30-35%.

3. The composite material according to claim 1 or 2, characterized in that, The composite material with a concentration of 0.4 wt% reduces the swelling height caused by the hydration of bentonite by 50-55%.

4. A method for preparing the composite material according to any one of claims 1-3, characterized in that, include: (1) A single-layer graphite is oxidized with an oxidizing agent, and the product is then reduced with a reducing agent to obtain graphene oxide; (2) The graphene oxide and polyethyleneimine are reacted to obtain the composite material; The mass ratio of the reducing agent to monolayer graphite is 1-1.5:

100.

5. The preparation method according to claim 4, characterized in that, In step (1), before the oxidation reaction, the graphite is first stripped from concentrated sulfuric acid to obtain a single layer of graphite.

6. The preparation method according to claim 5, characterized in that, The weight ratio of graphite to concentrated sulfuric acid is 1:35-38.

7. The preparation method according to any one of claims 4-6, characterized in that, The oxidant is selected from one or more of sodium nitrate, potassium permanganate, and nitric acid; And / or, the reducing agent is selected from hydrazine hydrate; And / or, relative to 100 parts by weight of graphite, the oxidant is 200-400 parts by weight, and the reducing agent is 1-1.5 parts by weight; And / or, the oxidation reaction is carried out at a temperature of 90-95°C; the oxidation reaction is carried out for a time of 1.5-2 hours. And / or, the temperature of the reduction reaction is 20-30℃; the time of the reduction reaction is 20-30 min.

8. The preparation method according to any one of claims 4-6, characterized in that, In step (2), the reaction temperature is 60-80℃ and the reaction time is 6-8 h.

9. The preparation method according to claim 7, characterized in that, In step (2), the reaction temperature is 60-80℃ and the reaction time is 6-8 h.

10. The preparation method according to any one of claims 4-6 and 9, characterized in that, The mass ratio of polyethyleneimine to graphene oxide is 9-10:1; And / or, in step (2), the graphene oxide is dissolved in water before the reaction, and the concentration of the graphene oxide in the water is 0.5-2 wt%.

11. The preparation method according to claim 7, characterized in that, The mass ratio of polyethyleneimine to graphene oxide is 9-10:1; And / or, in step (2), the graphene oxide is dissolved in water before the reaction, and the concentration of the graphene oxide in the water is 0.5-2 wt%.

12. The preparation method according to claim 8, characterized in that, The mass ratio of polyethyleneimine to graphene oxide is 9-10:1; And / or, in step (2), the graphene oxide is dissolved in water before the reaction, and the concentration of the graphene oxide in the water is 0.5-2 wt%.

13. The application of the composite material according to any one of claims 1-3 as a shale inhibitor in water-based drilling fluid.

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