Nanosheet oil displacement agents, their preparation and use

Abstract

The application discloses a nanosheet oil displacement agent and a preparation and application thereof, the interfacial tension of the nanosheet oil displacement agent is 0.27-4.21 mN / m, and the preparation method comprises the following steps: S1, adopting methanol to dissolve sodium octadecyl benzene sulfonate and reacting with formaldehyde to obtain an auxiliary agent; S2, dispersing the auxiliary agent and a magnesium source in deionized water to form a dispersion liquid, adjusting the pH value of the dispersion liquid to be weak alkaline, then adding a precipitant to react, and after purification and drying treatment, a sheet-shaped magnesium hydroxide nanometer material is obtained; S3, reacting the sheet-shaped magnesium hydroxide nanometer material with 3-aminopropyl triethoxysilane, and after purification and drying treatment, a sheet-shaped silane modified magnesium hydroxide nanometer material is obtained; and S4, mixing the sheet-shaped silane modified magnesium hydroxide nanometer material with water, adding an amphoteric surfactant, and obtaining the nanosheet oil displacement agent. The method is simple, the production cost is low, the nanosheet oil displacement agent prepared by the method can effectively reduce the oil-water interfacial tension, and then the oil recovery rate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of nanosheet oil displacement agent and its preparation and application. BACKGROUND

[0002] With the increasingly serious energy problem, the development of low permeability reservoir has also become the focus of oil field research, and due to the complex pore throat structure, small pore size, large specific surface area of low permeability reservoir, the conventional oil displacement agent has the problem of injection difficulty. In addition, the development of natural fractures in the reservoir causes serious heterogeneity in low permeability reservoirs, and the remaining oil is difficult to be effectively produced, which also leads to the poor development effect of conventional surfactant flooding, polymer flooding and other technologies in low permeability reservoirs.

[0003] Nanomaterials not only have good injection capacity in low permeability pores, but also can effectively improve the micro-washing efficiency by changing the wettability of the reservoir, reducing the interfacial tension and stripping the oil film at the interface. The nanomaterial-based oil displacement technology system is the key to improving the recovery of low permeability reservoirs and has extremely important significance for oil and gas exploitation.

[0004] Traditional nanomaterials are mainly one-dimensional spherical nanoparticles (such as SiO2, TiO2, Al2O3, CuO, ZnO, etc.). Spherical nanoparticles usually have the advantages of simple manufacturing process and low cost, but have the disadvantages of easy aggregation, low contact efficiency with oil-water interface, small specific surface area, few active sites, and low modification efficiency.

[0005] Newly discovered two-dimensional sheet nanomaterials have the characteristics of large specific surface area, many active sites, and high contact efficiency with oil-water interface. However, the sheet nanomaterials currently used in oil displacement agents are mainly molybdenum disulfide and graphene oxide, and the preparation of such nanomaterials usually involves complex processes and high costs, which lack industrial value. SUMMARY

[0006] In order to prepare two-dimensional sheet nanomaterials for oil displacement with excellent performance at low cost, the present application is made.

[0007] As a first aspect of the present application, it relates to a nanosheet oil displacement agent, which has an interfacial tension of 0.27-4.21 mN / m.

[0008] As a second aspect of the present application, it relates to a method for preparing the above-mentioned nanosheet oil displacement agent, characterized in that the method comprises the following steps:

[0009] S1: Dissolving sodium octadecyl benzene sulfonate and formaldehyde in methanol to obtain an auxiliary agent;

[0010] S2: dispersing the auxiliary agent and the magnesium source prepared in S1 in deionized water to form a dispersion liquid, adjusting the pH value of the dispersion liquid to be weak alkaline, then adding a precipitator to react, and after purification and drying treatment, a flaky magnesium hydroxide nanomaterial is obtained;

[0011] S3: reacting the flaky magnesium hydroxide nanomaterial prepared in S2 with 3-aminopropyl triethoxysilane, and after purification and drying treatment, a flaky silane-modified magnesium hydroxide nanomaterial is obtained;

[0012] S4: mixing the flaky silane-modified magnesium hydroxide nanomaterial prepared in S3 with water, and adding an amphoteric surfactant to obtain a nanosheet oil displacement agent.

[0013] Further, the auxiliary agent has the following structural formula:

[0014]

[0015] Further, S1 specifically comprises the following steps:

[0016] S11: placing sodium octadecyl benzene sulfonate into a reaction container, and then adding methanol as a solvent;

[0017] S12: under the reflux temperature of 65-75°C, stirring at the rotation speed of 300-500 r / min, and adding formaldehyde into the reaction container at the speed of 2-3 mL / min to react;

[0018] S13: after the reaction is completed, removing the solvent by vacuum distillation and vacuum drying to obtain the auxiliary agent.

[0019] Further, the molar mass ratio of sodium octadecyl benzene sulfonate and formaldehyde in S11 is 1.0:2.0-3.0.

[0020] Further, S2 specifically comprises the following steps:

[0021] S21: adding the auxiliary agent and the magnesium source into deionized water according to the mass ratio of 1.0:1.0-8.0 to form a monomer solution, stirring the solution to form a dispersion liquid under the assistance of ultrasonic oscillation, and adjusting the pH value of the dispersion liquid to be 9-11 by using alkaline substances;

[0022] S22: stirring the dispersion liquid in S21 uniformly at 20-95°C at the rotation speed of 200-600 r / min, and adding a precipitator dropwise during the stirring process to prepare a suspension;

[0023] S23: continuously stirring the suspension in S22 at 20-95°C for more than 30-300 min, and then performing purification and drying treatment to obtain a flaky magnesium hydroxide nanomaterial.

[0024] Further, the magnesium source in S21 is at least one of magnesium chloride or magnesium nitrate.

[0025] Further, the alkaline substance in S21 is at least one of sodium hydroxide or ammonia.

[0026] Further, the precipitant in S22 is at least one of sodium hydroxide or ammonia.

[0027] Further, the mass ratio of the precipitant to the auxiliary agent in S22 is 2.0-6.0:1.0.

[0028] Further, S3 specifically comprises the following steps:

[0029] S31: adding the flaky magnesium hydroxide nanomaterial into anhydrous ethanol, and stirring under the assistance of ultrasonic oscillation to form a dispersion solution;

[0030] S32: uniformly stirring the dispersion solution in S31 at a speed of 400-600 r / min at 30-50°C, dropwise adding 3-aminopropyl triethoxysilane during the stirring process, and continuously stirring for 16-30 h after the dropwise addition is completed to obtain a suspension;

[0031] S33: purifying and drying the suspension obtained in S32 to obtain the flaky silane-modified magnesium hydroxide nanomaterial.

[0032] Further, the mass ratio of 3-aminopropyl triethoxysilane to the flaky magnesium hydroxide nanomaterial in S32 is 0.5-2.0:1.0.

[0033] Further, S4 specifically comprises the following steps:

[0034] S41: mixing the flaky silane-modified magnesium hydroxide nanomaterial prepared in S3 with water according to a mass ratio of 1.0-5.0:1000, and then ultrasonic dispersing for 0.5-1 h to obtain a flaky silane-modified magnesium hydroxide nanomaterial dispersion solution;

[0035] S42: uniformly dissolving the amphoteric surfactant in the flaky silane-modified magnesium hydroxide nanomaterial dispersion solution in S41 to obtain a nanosheet oil displacement agent.

[0036] Further, the mass ratio of the amphoteric surfactant to water in S42 is 1-10:1000.

[0037] Further, the amphoteric surfactant in S42 is one of dodecyl ethyloxy sulfobetaine, dodecyl dimethyl hydroxypropyl sulfobetaine, and dodecyl dimethyl sulfopropyl betaine.

[0038] As a third aspect of the present application, it relates to the application of the above-mentioned nanosheet oil displacement agent in oilfield exploitation.

[0039] The auxiliary agent plays the role of dispersant and structure directing agent in the preparation of magnesium hydroxide by the coprecipitation method, thereby assisting in controlling the formation of the sheet-shaped nanomaterial. When the auxiliary agent acts as a dispersant, it plays the role of enhancing steric hindrance, which can prevent the agglomeration of the nanomaterial, thereby controlling the particle size of the magnesium hydroxide nanomaterial. When the auxiliary agent acts as a structure directing agent, it has a direct guiding effect on the growth of magnesium hydroxide. The hydroxyl groups on the auxiliary agent form coordination bonds with magnesium ions, so that the auxiliary agent can be adsorbed on the surface of magnesium hydroxide. The benzene ring and long carbon chain on the auxiliary agent can inhibit the longitudinal growth of the magnesium hydroxide crystal, thereby guiding the formation of the sheet-shaped morphology of magnesium hydroxide, thereby realizing a method for stably preparing sheet-shaped magnesium hydroxide nanomaterial.

[0040] The sheet-shaped magnesium hydroxide nanomaterial prepared by the method of the present application can be modified by coupling with 3-aminopropyl triethoxysilane to become an amphiphilic sheet-shaped nanomaterial, which exhibits very good dispersibility in solution and has strong functions such as reducing interfacial tension, automatically adsorbing on the oil-water interface, etc., and can be compounded with surfactants to form a nanosheet oil displacement agent.

[0041] The present application uses low-cost magnesium salt as the main raw material, realizes the preparation of sheet-shaped magnesium hydroxide nanomaterial under the low-energy consumption coprecipitation method combined with an auxiliary agent, and on this basis, the sheet-shaped magnesium hydroxide nanomaterial is surface modified by a silane coupling agent, and then a kind of amphiphilic sheet-shaped oil displacement agent can be obtained by physical blending. The preparation method of the present application is simple and stable, and the raw material cost is low. A kind of sheet-shaped magnesium hydroxide nanomaterial with large specific surface area, many active sites and high oil-water interface contact efficiency can be stably and efficiently synthesized under low-cost conditions, thereby forming a low-cost amphiphilic nanosheet oil displacement system, which has industrial value. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 SEM picture of the sheet-shaped magnesium hydroxide nanomaterial prepared in Example 4;

[0043] Figure 2 SEM picture of the sheet-shaped magnesium hydroxide nanomaterial prepared in Comparative Example 1;

[0044] Figure 3 SEM picture of the sheet-shaped magnesium hydroxide nanomaterial prepared in Comparative Example 2. DETAILED DESCRIPTION

[0045] The following describes embodiments of the present application in detail: The embodiments of the present application are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and processes are given, but the protection scope of the present application is not limited to the following embodiments. The process parameters not specified in the following embodiments are usually according to conventional conditions.

[0046] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The endpoints of the ranges are provided as a separate value from but are included in the range. For values which are less than or greater than a stated range, the range is intended to include all values and sub-ranges between the stated values or sub-ranges. For values which are less than or greater than a maximum or minimum value, the value is intended to include all values and sub-ranges between the maximum and minimum values or to the maximum or minimum value. Any numerical values include all values about, adjacent to, and range between the recited values. In this application, the use of "about" means that natural, expected deviations and variations will occur in the mentioned parameter and that the disclosed embodiments do not exclude these deviations and variations.

[0047] Example 1

[0048] The auxiliary agent is prepared by the following steps:

[0049] Sodium octadecyl benzene sulfonate (4.32 g) and formaldehyde (0.6 g) are weighed according to the molar ratio of 1:2. The weighed sodium octadecyl benzene sulfonate is placed in a 250 mL three-necked flask, 50 mL of methanol is added as a solvent, and the formaldehyde is added dropwise at a stirring rate of 300 r / min at a reflux temperature of 65 DEG C (the dropwise adding speed is 2 mL / min), and the reaction is carried out for 3 h. After the reaction is completed, the solvent is removed by vacuum distillation and vacuum drying, and a viscous solid is obtained, which is the target product.

[0050] Example 2

[0051] The auxiliary agent is prepared by the following steps:

[0052] Sodium octadecyl benzene sulfonate (4.32 g) and formaldehyde (0.75 g) are weighed according to the molar ratio of 1:2.5. The weighed sodium octadecyl benzene sulfonate is placed in a 250 mL three-necked flask, 50 mL of methanol is added as a solvent, and the formaldehyde is added dropwise at a stirring rate of 400 r / min at a reflux temperature of 70 DEG C (the dropwise adding speed is 2.5 mL / min), and the reaction is carried out for 3 h. After the reaction is completed, the solvent is removed by vacuum distillation and vacuum drying, and a viscous solid is obtained, which is the target product.

[0053] Example 3

[0054] The auxiliary agent is prepared by the following steps:

[0055] Sodium octadecylbenzenesulfonate (4.32 g) and formaldehyde (0.9 g) were weighed out in a molar ratio of 1:3. The weighed sodium octadecylbenzenesulfonate was placed in a 250 mL three-necked flask, and 50 mL of methanol was added as solvent. Formaldehyde was added dropwise at a rate of 3 mL / min while stirring at 500 rpm under reflux at 75 °C for 3 h. After the reaction was complete, the solvent was removed by vacuum distillation and vacuum drying to obtain a viscous solid, which was the target product.

[0056] Example 4

[0057] The steps for preparing magnesium hydroxide nanomaterials are as follows:

[0058] Take a 250ml beaker and add 0.5g of the auxiliary agent prepared in Example 1, 2g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 10 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and add 2g of ammonia solution dropwise in a 40℃ water bath while stirring at 400r / min. After the addition is complete, a suspension is obtained. Continue to react the suspension at 400r / min and 40℃ for 4 hours until the reaction is complete. Centrifuge the obtained product, wash it several times with ethanol, and dry it to obtain a dry powder product, which is magnesium hydroxide nanomaterial 1.

[0059] The obtained product was imaged using a scanning electron microscope (SEM), and the SEM images are as follows: Figure 1 As shown, it exhibits a well-formed flake shape with a particle size of approximately 150 nm.

[0060] Comparative Example 1

[0061] The steps for preparing magnesium hydroxide nanomaterials are as follows:

[0062] Take a 250ml beaker and add 0.5g sodium octadecylbenzenesulfonate, 2g MgCl2, and 100ml deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 10 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and add 4g of ammonia solution dropwise in a 40℃ water bath while stirring at 400 rpm. After the addition is complete, a suspension is obtained. Continue the reaction at 400 rpm and 40℃ for 4 hours until the reaction is complete. Centrifuge the obtained product, wash it several times with ethanol, and dry it to obtain a dry powder product, which is magnesium hydroxide nanomaterial 2.

[0063] The obtained product was imaged using a scanning electron microscope (SEM), and the SEM images are as follows: Figure 2 As shown, they are blocky with a particle size of approximately 200 nm.

[0064] Comparative Example 2

[0065] The magnesium hydroxide nanomaterial was prepared by the following steps:

[0066] A 250ml beaker was taken, 2g of MgCl2and 100ml of deionized water were added into the beaker, and a dispersion was formed by ultrasonic oscillation. The dispersion was adjusted to pH 10 using ammonia water. The dispersion after adjusting the pH was poured into a 250ml flask, and 4g of ammonia water solution was added dropwise under a 40°C water bath, while stirring at a speed of 400r / min. After the dropwise addition was completed, a suspension was obtained. The suspension was continuously reacted at a speed of 400r / min and a temperature of 40°C, and the reaction was completed after 4 hours. The product was separated by centrifugation, washed with ethanol several times, and dried to obtain a dry powder product, which was the magnesium hydroxide nanomaterial 3.

[0067] The obtained product was photographed by scanning electron microscopy, and the SEM picture is shown in Figure 3 , which is spherical with a particle size of about 110nm.

[0068] Example 5

[0069] The magnesium hydroxide nanomaterial was prepared by the following steps:

[0070] A 250ml beaker was taken, 2g of MgCl2and 100ml of deionized water were added into the beaker, and a dispersion was formed by ultrasonic oscillation. The dispersion was adjusted to pH 10 using ammonia water. The dispersion after adjusting the pH was poured into a 250ml flask, and 4g of ammonia water solution was added dropwise under a 40°C water bath, while stirring at a speed of 400r / min. After the dropwise addition was completed, a suspension was obtained. The suspension was continuously reacted at a speed of 400r / min and a temperature of 40°C, and the reaction was completed after 4 hours. The product was separated by centrifugation, washed with ethanol several times, and dried to obtain a dry powder product, which was the magnesium hydroxide nanomaterial 3.

[0071] The obtained product was photographed by scanning electron microscopy, and the SEM picture is shown in

[0072] Example 6

[0073] The magnesium hydroxide nanomaterial was prepared by the following steps:

[0074] A 250 ml beaker was taken, 0.5 g of the adjuvant prepared in Example 1, 4 g of MgCl2and 100 ml of deionized water were added into the beaker to form a dispersion liquid by ultrasonic oscillation. The pH value of the dispersion liquid was adjusted to 9 by sodium hydroxide. The dispersion liquid after pH adjustment was poured into a 250 ml flask, and 3 g of sodium hydroxide solution was added dropwise under a water bath at 95°C while stirring at a speed of 600 r / min. After the dropwise addition was completed, a suspension was obtained. The suspension was continuously reacted at a speed of 600 r / min and a temperature of 95°C, and the reaction was completed after 5 hours. The obtained product was centrifuged, washed with ethanol for multiple times and dried to obtain a dry powder product, which was a magnesium hydroxide nanomaterial 5.

[0075] The obtained product was photographed by a scanning electron microscope, and was in a good flaky shape with a particle size of about 170 nm.

[0076] Example 7

[0077] A nanosheet oil displacement agent was prepared, and the steps were as follows:

[0078] A 250 ml beaker was taken, 1 g of the flaky magnesium hydroxide nanomaterial 1 prepared in Example 4 and 100 ml of anhydrous ethanol were added into the beaker to form a dispersion liquid by ultrasonic oscillation. A 3-aminopropyltriethoxysilane solution 0.5 g was added dropwise under a water bath at 30°C while stirring at a speed of 400 r / min. After the dropwise addition was completed, the solution was continuously reacted at a speed of 400 r / min and a temperature of 30°C, and the reaction was completed after 16 hours. The obtained product was centrifuged, washed with ethanol for multiple times and dried to obtain a dry powder product. 1 g of the dry powder product was added into 1000 g of water, and ultrasonic dispersion was performed for 30 min to obtain a nanomaterial dispersion liquid. A surfactant, dodecyl ethoxy sulfobetaine, was added into the dispersion liquid according to a proportion of 0.1 wt%, and was uniformly dissolved to obtain a nanosheet oil displacement agent 1.

[0079] Example 8

[0080] A nanosheet oil displacement agent was prepared, and the steps were as follows:

[0081] Into a 250ml flask, 1g of the flaky magnesium hydroxide nanomaterial 2 prepared in Example 5 and 100ml of anhydrous ethanol were added to form a dispersion liquid by ultrasonic oscillation. A 3-aminopropyl triethoxysilane solution 1.3g was added dropwise under a 40°C water bath while stirring at a speed of 500r / min. After the dropwise addition was completed, the solution was continuously reacted at a speed of 600r / min and a temperature of 40°C, and the reaction was completed after 23 hours. The product was separated by centrifugation, washed with ethanol several times, and dried to obtain a dry powder product. 2.5g of the dry powder product was added to 1000g of water, and ultrasonic dispersion was performed for 45min to obtain a nanomaterial dispersion liquid. A surfactant, dodecyl dimethyl hydroxypropyl sulfobetaine, was added to the dispersion liquid in a proportion of 0.5wt%, and was uniformly dissolved to obtain a nanosheet oil displacement agent 2.

[0082] Example 9

[0083] A nanosheet oil displacement agent was prepared by the following steps:

[0084] Into a 250ml flask, 1g of the flaky magnesium hydroxide nanomaterial 3 prepared in Example 6 and 100ml of anhydrous ethanol were added to form a dispersion liquid by ultrasonic oscillation. A 3-aminopropyl triethoxysilane solution 2.0g was added dropwise under a 50°C water bath while stirring at a speed of 600r / min. After the dropwise addition was completed, the solution was continuously reacted at a speed of 600r / min and a temperature of 50°C, and the reaction was completed after 30 hours. The product was separated by centrifugation, washed with ethanol several times, and dried to obtain a dry powder product. 5g of the dry powder product was added to 1000g of water, and ultrasonic dispersion was performed for 60min to obtain a nanomaterial dispersion liquid. A surfactant, dodecyl dimethyl sulfopropyl betaine, was added to the dispersion liquid in a proportion of 1wt%, and was uniformly dissolved to obtain a nanosheet oil displacement agent 3.

[0085] Comparative Example 3

[0086] A nanosheet oil displacement agent was prepared by the following steps:

[0087] Into a 250ml flask, 1g of the flaky magnesium hydroxide nanomaterial prepared in Example 4 was added to 1000g of water, and ultrasonic dispersion was performed for 30min to obtain a nanomaterial dispersion liquid. A surfactant, dodecyl dimethyl sulfopropyl betaine, was added to the dispersion liquid in a proportion of 0.3wt%, and was uniformly dissolved to obtain a nanosheet oil displacement agent 4.

[0088] Test Example 1

[0089] The nanosheet oil displacement agents prepared in Examples 7, 8, 9 and Comparative Example 3 were tested for interfacial tension performance by means of an SVT20N interfacial tension meter.

[0090] First, the sample cell was filled with the nanosheet oil displacement agent prepared in Example 7, Example 8, Example 9 and Comparative Example 3 diluted into an oil displacement agent solution with a nanosheet mass concentration of 0.05wt%, then a certain volume of crude oil (Daqing oilfield) was injected into the center of the sample cell with a microsyringe, the rotation speed was adjusted to 6000rpm, the image acquisition system was used to capture the change of oil droplet pattern with time, and the oil-water interfacial tension at different times was calculated according to the oil droplet pattern. When the oil-water interfacial tension is stable and unchanged, it is the oil-water interfacial tension at the equilibrium of oil droplets. Refer to the industry standard SYT5370-1999, “Surface and Interfacial Tension Determination Method”. At the same time, the surfactants dodecyl ethoxy sulfobetaine (denoted as betaine 1), dodecyl dimethyl sulfopropyl betaine (denoted as betaine 2) and petroleum sulfonate were respectively prepared into 0.05wt% aqueous solution as a control group. The test results are shown in Table 1.

[0091] Table 1 Interfacial tension test results

[0092]

[0093] From the analysis of Table 1, it can be seen that the nanosheet oil displacement agent 1 and the nanosheet oil displacement agent 2 prepared in Example 7 and Example 8 can reduce the interfacial tension to 10 -1 mN / m order of magnitude, while the nanosheet oil displacement agent 4 prepared in Comparative Example 3 can only reduce the oil-water interfacial tension to 7.29mN / m. At the same time, the betaine 1, betaine 2 and petroleum sulfonate in the comparative group can reduce the oil-water interfacial tension to 3.34mN / m, 3.41mN / m and 1.68mN / m respectively, and the nanosheet oil displacement agent 1 and the nanosheet oil displacement agent 2 prepared in Example 7 and Example 8 show stronger interfacial activity.

[0094] Test Example 2

[0095] The nanosheet oil displacement agents prepared in Example 7, Example 8, Example 9 and Comparative Example 3 were subjected to oil displacement experiment test, and the steps were as follows:

[0096] An artificial core (φ2.5x5cm) was used for oil displacement comparison experiment, the core porosity was about 25%, the permeability was about 30mD, and after saturated with water, it was saturated with crude oil (viscosity 3.5mPa·s, 25℃), and after aging for 7d, displacement experiment was carried out. Water flooding was carried out at a speed of 0.1mL / min until the water content reached 98%, then 0.3PV of the oil displacement agent solution was injected into the core at a speed of 0.1mL / min, then subsequent water flooding was carried out at a speed of 0.1mL / min until the water content reached 98%, the enhanced oil recovery amplitude of the oil displacement agent was calculated according to the difference between the final oil recovery and the water flooding recovery, and the oil recovery enhancement amplitude of different oil displacement agents on crude oil is shown in Table 2.

[0097] Table 2 results of enhanced oil recovery test (mass fraction of oil displacement agent is 0.05wt%)

[0098]

[0099] From the analysis of Table 2, it can be seen that the nanosheet oil displacement agent 1 and the nanosheet oil displacement agent 2 prepared by the example 7 and the example 8 of the present application have higher enhanced recovery amplitude, which indicates that under the same experimental conditions, the oil displacement performance of the nanosheet oil displacement agent 1 and the nanosheet oil displacement agent 2 prepared by the example 7 and the example 8 of the present application is superior to that of the betaine 1, the betaine 2 and the petroleum sulfonate.

[0100] Although the specific embodiments of the present application have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details in accordance with all the teachings disclosed herein, and these changes are within the scope of protection of the present application. The entire scope of the present application is given by the appended claims and any equivalents thereof.

Claims

1. A method of preparing a nanosheet oil displacement agent, characterized by, The method comprises the following steps: S1: adopting methanol to dissolve sodium octadecyl benzene sulfonate and react with formaldehyde to obtain an auxiliary agent; S2: dispersing the auxiliary agent prepared in S1 and a magnesium source in deionized water to form a dispersion liquid, adjusting the pH value of the dispersion liquid to weak alkaline, then adding a precipitant to react, and after purification and drying treatment, flaky magnesium hydroxide nanomaterial is obtained; S3: reacting the flaky magnesium hydroxide nanomaterial prepared in S2 with 3-aminopropyl triethoxysilane, and after purification and drying treatment, flaky silane modified magnesium hydroxide nanomaterial is obtained; S4: mixing the flaky silane modified magnesium hydroxide nanomaterial prepared in S3 with water and adding an amphoteric surfactant to obtain a nanosheet oil displacement agent, wherein: The auxiliary agent has the following structural formula: 。 2. The method of claim 1, wherein, The S1 specifically comprises the following steps: S11: placing sodium octadecyl benzene sulfonate into a reaction container, and then adding methanol as a solvent; S12: under the reflux temperature of 65-75 DEG C, stirring at the rotating speed of 300-500 r / min, and adding formaldehyde into the reaction container at the speed of 2-3 mL / min to react; S13: after the reaction is completed, removing the solvent by reduced pressure distillation and vacuum drying to obtain the auxiliary agent.

3. The method of claim 2, wherein, The molar mass ratio of sodium octadecyl benzene sulfonate and formaldehyde in the S11 is 1.0:2.0-3.

0.

4. The method of claim 1, wherein, The S2 specifically comprises the following steps: S21: adding the auxiliary agent and the magnesium source into deionized water according to the mass ratio of 1.0:1.0-8.0 to form a monomer solution, stirring under the assistance of ultrasonic oscillation to make the solution form a dispersion liquid, and adjusting the pH value of the dispersion liquid to 9-11 by using an alkaline substance; S22: stirring the dispersion liquid in S21 uniformly at the rotating speed of 200-600 r / min under 20-95 DEG C, and adding a precipitant during the stirring process to prepare a suspension liquid; S23: continuously stirring the suspension liquid in S22 under 20-95 DEG C for more than 30-300 min, and then performing purification and drying treatment to obtain flaky magnesium hydroxide nanomaterial.

5. The method of claim 4, wherein, The magnesium source in the S21 is at least one of magnesium chloride or magnesium nitrate.

6. The method of claim 4, wherein, The alkaline substance in the S21 is at least one of sodium hydroxide or ammonia water.

7. The method of claim 4, wherein, The precipitant in the S22 is at least one of sodium hydroxide or ammonia water.

8. The method of claim 4, wherein, The mass ratio of the precipitant to the auxiliary agent in the S22 is 2.0-6.0:1.

0.

9. The method of claim 1, wherein, The S3 specifically comprises the following steps: S31: adding flaky magnesium hydroxide nanomaterial into anhydrous ethanol, and stirring under the assistance of ultrasonic oscillation to make the solution form a dispersion liquid; S32: stirring the dispersion liquid in S31 uniformly at the rotating speed of 400-600 r / min under 70-90 DEG C, adding 3-aminopropyl triethoxysilane during the stirring process, and continuously stirring for 16-30 h after the addition is completed to obtain a suspension liquid; S33: performing purification and drying treatment on the suspension liquid obtained in S32 to obtain flaky silane modified magnesium hydroxide nanomaterial.

10. The method of claim 9, wherein, The mass ratio of 3-aminopropyl triethoxysilane to flaky magnesium hydroxide nanomaterial in the S32 is 0.5-2.0:1.

0.

11. The method of claim 1, wherein, The S4 specifically comprises the following steps: S41: mixing the flaky silane-modified magnesium hydroxide nanomaterial prepared in S3 with water in a mass ratio of 1.0-5.0:1000, and then ultrasonic dispersion for 0.5-1 h to obtain a flaky silane-modified magnesium hydroxide nanomaterial dispersion liquid; S42: uniformly dissolving an amphoteric surfactant in the flaky silane-modified magnesium hydroxide nanomaterial dispersion liquid in S41 to obtain a nanosheet oil displacement agent.

12. The method of claim 11, wherein, The mass ratio of the amphoteric surfactant to water in S42 is 0.1-1.0:1000.

13. The method of claim 11, wherein, The amphoteric surfactant in S42 is one of dodecyl ethoxy sulfobetaine, dodecyl dimethyl hydroxypropyl sulfobetaine, and dodecyl dimethyl sulfopropyl betaine.

14. The method of claim 11, wherein, The interfacial tension of the nanosheet oil displacement agent is 0.27-4.21 mN / m.

15. Application of the nanosheet oil displacement agent in claim 1 to oilfield exploitation.

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