Silicon-based nanofluid and preparation method thereof

Abstract

The application discloses a silicon-based nanofluid and a preparation method thereof, and relates to the technical field of oil field chemistry. The preparation method comprises the following steps: nanosilica and a silane coupling agent are subjected to oxygen removal by nitrogen in an ethanol solution, and are subjected to closed stirring reaction at 70-80 DEG C for 6-8 hours; then diethanolamine is slowly added dropwise, and the mixture is uniformly stirred; after oxygen removal by nitrogen, the mixture is subjected to sealed stirring reaction; the product is collected, purified and dried to obtain tertiary amine functionalized SiO2; the tertiary amine functionalized SiO2 is dispersed in anhydrous acetonitrile, and is uniformly subjected to ultrasonic dispersion; then bromododecane is added, and the mixture is subjected to stirring reflux reaction under nitrogen protection at 80-85 DEG C for 24-48 hours; after cooling to room temperature, the solid product is centrifugally separated; and the product is purified and dried to obtain a silicon-based nanoreducer; the silicon-based nanoreducer and sodium alpha-alkenyl sulfonate are dispersed in water to obtain the silicon-based nanofluid; the interfacial tension between the silicon-based nanofluid and crude oil can reach 10 ‑1 mN / m, and the silicon-based nanofluid can effectively reduce the adhesion work and flow resistance of crude oil on the surface of rocks.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a silicon-based nanofluid and its preparation method. Background Technology

[0002] With the depletion of conventional oil and gas resources, unconventional oil and gas resources are expected to account for an increasingly larger share of total production. Heavy oil is a typical unconventional oil and gas resource, with abundant reserves, accounting for more than 70% of global oil reserves, and possessing enormous development potential. The high viscosity and poor fluidity of heavy oil pose significant challenges to its development and transportation; therefore, reducing its viscosity is a crucial measure for efficient development.

[0003] Currently, methods for reducing the viscosity of heavy oil are mainly divided into two categories: thermal recovery and cold recovery. Thermal recovery includes steam drive, steam-assisted gravity drive, electric heating, and in-situ combustion. Although thermal recovery technology has been successfully applied in heavy oil reservoirs, it suffers from significant heat loss and high development costs. In contrast, chemical viscosity reduction technology is simple to operate, has a wide range of applications, strong viscosity reduction effect, and higher economic benefits. Typically, water-soluble viscosity reducers are added to the injection water to emulsify the heavy oil and form a low-viscosity oil-in-water (O / W) emulsion, thereby reducing viscosity. Surfactants are widely used as the main water-soluble viscosity reducers; however, surfactants are heavily adsorbed on the reservoir rock surface, have poor affinity with heavy oil, and the resulting emulsions are highly unstable. Furthermore, their performance degrades significantly with increasing temperature and salinity. Therefore, there is an urgent need to develop more efficient viscosity reduction systems.

[0004] Compared to traditional chemical enhanced oil recovery (EOR) technologies, nanomaterials have attracted significant interest in the field due to their unique properties. Nano-displacement agents can further improve heavy oil extraction efficiency by enhancing wettability, reducing interfacial tension, generating separation pressure, and forming stable emulsions under harsh conditions. In recent decades, nanotechnology has rapidly become a new dominant technology, capable of competing with traditional methods both technically and economically. The application of nanotechnology in the oil and gas industry offers unprecedented opportunities for developing more economical, efficient, and environmentally friendly oil and gas extraction technologies.

[0005] For example, Chen et al. synthesized amphiphilic carbon nanotubes (HCNTs) through chemical modification. The nanofluid obtained by combining HCNTs with surfactants achieved a viscosity reduction rate of 99.19% for crude oil. Core displacement experiments showed that using nanofluids increased oil recovery by 29.55%, which was 9.49% higher than using surfactant systems alone. Liu et al. synthesized a bio-nanomaterial, Fe3O4@-SiO2-Ag (BNF). The results showed that BNF could reduce interfacial tension by 80%, stabilize oil-water emulsions for more than three months at 500 ppm, and significantly improve the static separation of oil droplets and the dynamic stripping of oil films, increasing oil recovery by 15.56% on the basis of waterflooding.

[0006] Therefore, compared with traditional chemical flooding techniques for enhancing oil recovery, nanofluids have a better effect on increasing oil production. Thus, to address the current problem of low recovery rates in heavy oil reservoirs, designing efficient nanofluid flooding agents to form relatively stable O / W low-viscosity emulsions is key to solving this problem. Summary of the Invention

[0007] In view of this, the present invention proposes a silicon-based nanofluid and its preparation method. A silicon-based drag-reducing nano-agent is prepared by reacting silane-modified nano-silica with diethanolamine, and then compounded with sodium α-alkenyl sulfonate to obtain a silicon-based nanofluid. This nanofluid can achieve an interfacial tension of 10 with crude oil. -1 It is on the order of mN / m and synergistically improves reservoir wettability, reduces crude oil adhesion work, and induces the formation of Pickering emulsion, reducing flow resistance, thereby significantly improving crude oil recovery.

[0008] This invention discloses a method for preparing silicon-based nanofluids, comprising the following steps: Step S1: Nano-silica and silane coupling agent are purged with nitrogen in anhydrous ethanol solution for at least 30 min to remove oxygen. The reaction is carried out in a sealed environment at 70℃~80℃ for 6h~8h with stirring. Then, diethanolamine is slowly added dropwise and stirred vigorously until homogeneous. After purging with nitrogen for at least 30 min, the reaction is carried out in a sealed environment at 70℃~80℃ with stirring for 10h~12h. The product is collected, purified, and dried to obtain tertiary amine functionalized SiO2. Step S2: Disperse tertiary amine-functionalized SiO2 in anhydrous acetonitrile, ultrasonically disperse it evenly, add bromododecane, purge with nitrogen, stir and reflux at 80℃~85℃ for 24h~48h, cool to room temperature, centrifuge to separate the solid product, purify and dry to obtain silicon-based nano drag-reducing agent. Step S3: Disperse the silicon-based nano drag reducer and sodium α-olefin sulfonate in water and ultrasonically vibrate for 20-40 minutes to obtain the final product.

[0009] One embodiment of the present invention is that the particle size of the nano-silica is 10nm~30nm.

[0010] In one embodiment of the present invention, the ratio of nano-silica to silane coupling agent in step S1 is 1:0.5~3 by weight.

[0011] One embodiment of the present invention is that the silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0012] In one embodiment of the present invention, the ratio of nano-silica to diethanolamine in step S1 is 1:1 to 2.5 by weight.

[0013] In one embodiment of the present invention, the ratio of the tertiary amine functionalized SiO2 to bromododecane in step S2 is 1:1.2~1.5 by weight.

[0014] In one embodiment of the present invention, the ratio of silicon-based nano drag-reducing agent to sodium α-olefin sulfonate in step S3 is 1:0.2~0.5 by weight.

[0015] In one embodiment of the present invention, the total mass fraction of the silicon-based nano drag-reducing agent and sodium α-olefin sulfonate dispersed in water in step S3 is 0.3% to 0.5%.

[0016] One embodiment of the present invention is that the carbon chain range of the sodium α-alkenylsulfonate is C. n =14~16.

[0017] And silicon-based nanofluids prepared according to the above method.

[0018] The technical advantages of this invention are as follows: (1) The silicon-based nanofluid preparation method in this invention is simple, reliable in principle, and simple in synthesis process. It does not require an additional injection system and can be directly injected using water injection system and sewage injection, resulting in low preparation and construction costs.

[0019] (2) The interfacial tension between the silicon-based nanofluid and crude oil in this invention can reach 10. -1 Silicon-based nanofluids, on the order of mN / m, improve the wettability of oil reservoirs and can effectively reduce the adhesion work of crude oil on rock surfaces.

[0020] (3) The silicon-based nanofluid in this invention can be adsorbed at the oil-water interface to form a Pickering emulsion under shear action. The viscosity of the Pickering emulsion is lower than that of the oil phase, thereby reducing the flow resistance.

[0021] (4) The silicon-based nanofluid in this invention is suitable for medium and low permeability water injection development of oil reservoirs, including those with high temperature and high salinity, and has a wide range of applications. Attached Figure Description

[0022] Figure 1 The image shows the infrared characterization results of the silicon-based nano drag reducer and the unmodified nano silica in Example 1 of this invention. Figure 2 The graph shows the thermogravimetric analysis results of the silicon-based nano drag reducer and the unmodified nano silica in Example 1 of the present invention. Figure 3 The figure shows the test results of the interfacial tension reduction performance of the silicon-based nanofluid in Example 1 of the present invention; Figure 4 The figure shows the test results of the rock wettability improvement performance of the silicon-based nanofluid in Example 1 of the present invention; Figure 5 The figure shows the oil displacement performance test results of Embodiment 1 of the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0024] Example 1 (1) 3g of 20nm nano-silica was added to a 250 mL three-necked flask, followed by 150g of anhydrous ethanol. The mixture was ultrasonically vibrated for 30 min to ensure uniform dispersion of the nano-silica. Then, under an oil bath at 80℃, 3g of γ-glycidyl etheroxypropyltrimethoxysilane was added to the three-necked flask containing the nano-silica dispersion. Nitrogen was purged for 30 min to remove oxygen, and the mixture was sealed and stirred for 6 h to induce the grafting reaction. Subsequently, 4g of diethanolamine (DEA) was slowly added dropwise, and the mixture was stirred vigorously. After purging with nitrogen for 30 min to remove oxygen, the mixture was heated to 80℃ and reacted for 12 h under continuous stirring. The reaction product was repeatedly washed with anhydrous ethanol and deionized water, and finally dried under vacuum at 60℃ to obtain tertiary amine-functionalized SiO2.

[0025] (2) 1.0 g of tertiary amine functionalized SiO2 was dispersed in 50 mL of anhydrous acetonitrile and sonicated for 30 min. 1.2 g of bromododecane was added to the dispersion. Under nitrogen protection, the reaction mixture was heated to 80°C and stirred under reflux for 48 h. After the reaction was completed, it was cooled to room temperature. The solid product was then separated by centrifugation, washed with ethanol, and dried in a vacuum drying oven at 50°C for 24 h to obtain a silicon-based nano drag reducer with an amphiphilic quaternary ammonium salt on its surface.

[0026] (3) Disperse 0.3g of silicon-based nano drag reducer and 0.06g of sodium α-alkenyl sulfonate at room temperature in 100mL of formation water (mineralization 3×10⁻⁶). 4 Silicon-based nanofluids were obtained by ultrasonic oscillation for 30 minutes in a solution of (mg / L).

[0027] Example 2 (1) 3g of 20nm nano-silica was added to a 250 mL three-necked flask, followed by 150g of anhydrous ethanol. The mixture was ultrasonically vibrated for 30 min to ensure uniform dispersion of the nano-silica. Then, 5g of γ-glycidyl etheroxypropyltrimethoxysilane was added to the three-necked flask containing the nano-silica dispersion under an oil bath at 80℃. Nitrogen was purged for 30 min to remove oxygen, and the grafting reaction was carried out under sealed stirring for 8 h. Subsequently, 4g of diethanolamine (DEA) was slowly added dropwise, and the mixture was stirred vigorously. After purging with nitrogen for 30 min to remove oxygen, the temperature was raised to 80℃ and reacted for 12 h under continuous stirring. The reaction product was repeatedly washed with anhydrous ethanol and deionized water, and finally dried under vacuum at 60℃ to obtain tertiary amine-functionalized SiO2.

[0028] (2) 1.0 g of tertiary amine functionalized SiO2 was dispersed in 50 mL of anhydrous acetonitrile and sonicated for 30 min. 1.5 g of bromododecane was added to the dispersion. Under nitrogen protection, the reaction mixture was heated to 80°C and stirred under reflux for 48 h. After the reaction was completed, it was cooled to room temperature. The solid product was then separated by centrifugation, washed with ethanol, and dried in a vacuum drying oven at 50°C for 24 h to obtain a silicon-based nano drag reducer with an amphiphilic quaternary ammonium salt on its surface.

[0029] (3) Disperse 0.3g of silicon-based nano drag reducer and 0.06g of sodium α-olefin sulfonate at room temperature in 100mL of formation water (mineralization 3×10⁻⁶). 4 Silicon-based nanofluids were obtained by ultrasonic oscillation for 30 minutes in a solution of (mg / L).

[0030] Example 3 (1) 3g of 20nm nano-silica was added to a 250 mL three-necked flask, followed by 150g of anhydrous ethanol. The mixture was ultrasonically vibrated for 30 min to ensure uniform dispersion of the nano-silica. Then, 3g of γ-glycidyl etheroxypropyltrimethoxysilane was added to the three-necked flask containing the nano-silica dispersion under an oil bath at 80°C. Nitrogen was purged for 30 min to remove oxygen, and the mixture was sealed and stirred for 6 h to induce the grafting reaction. Subsequently, 6g of diethanolamine (DEA) was slowly added dropwise, and the mixture was stirred vigorously. After purging with nitrogen for 30 min to remove oxygen, the mixture was heated to 80°C and reacted for 12 h under continuous stirring. The reaction product was repeatedly washed with anhydrous ethanol and deionized water, and finally dried under vacuum at 60°C to obtain tertiary amine-functionalized SiO2.

[0031] (2) 1.0 g of tertiary amine functionalized SiO2 was dispersed in 50 mL of anhydrous acetonitrile and sonicated for 30 min. 1.2 g of bromododecane was added to the dispersion. Under nitrogen protection, the reaction mixture was heated to 85°C and stirred under reflux for 24 h. After the reaction was completed, it was cooled to room temperature. The solid product was then separated by centrifugation, washed with ethanol, and dried in a vacuum drying oven at 50°C for 24 h to obtain a silicon-based nano drag reducer with an amphiphilic quaternary ammonium salt on its surface.

[0032] (3) Disperse 0.3g of silicon-based nano drag reducer and 0.06g of sodium α-olefin sulfonate at room temperature in 100mL of formation water (mineralization 3×10⁻⁶). 4 Silicon-based nanofluids were obtained by ultrasonic oscillation for 30 minutes in a solution of (mg / L).

[0033] Performance Evaluation I. Infrared characterization of silicon-based nanodrag reducing agents: Infrared characterization tests were performed on the silicon-based drag-reducing nanoparticles and the unmodified nano-silica in Example 1, and the results are as follows: Figure 1 As shown. In Figure 1 As can be seen, the infrared spectrum of unmodified nano-silica is at 3435.1 nm. - ¹ and 1629.5 cm - A characteristic peak appears at ¹, corresponding to the stretching vibration of Si-OH and the surface water molecule, respectively; 1103.3 cm⁻¹ - ¹ and 800.7 cm - The peak at ¹ belongs to the antisymmetric and symmetric stretching vibrations of Si-O-Si, 472.4 cm⁻¹. - The peak near ¹ corresponds to the bending vibration of Si-O-Si. Example 1 shows a peak at 2978.1 cm⁻¹. - The appearance of a new CH stretching vibration peak at position ¹ indicates successful grafting of organic matter onto the surface; 961.6 cm⁻¹ - The weakening of the peak intensity near ¹ indicates that the hydroxyl groups on the SiO2 surface participated in the reaction.

[0034] II. Thermogravimetric characterization of silicon-based nano drag-reducing agents: Thermogravimetric analysis (TGA) tests were performed on the silicon-based nano drag-reducing agent product from Example 1 and the unmodified nano silica, and the results are as follows: Figure 2 As shown. In Figure 2 As can be seen, the unmodified nano-silica exhibits a slight mass loss before 200℃, mainly due to the evaporation of surface water molecules and the decomposition of hydroxyl groups; the mass remains relatively stable after 200℃. The residual mass of the silicon-based nano-drag reducer is significantly reduced, with obvious heat loss in the 250~600℃ range. This is mainly attributed to the high-temperature decomposition of the organic materials grafted onto the particle surface, confirming the success of the surface modification.

[0035] III. Viscosity Performance Testing of Emulsion Systems: The mineralization degree is 3×10 4 mg / L (Ca 2+ Mg 2+ The concentrations were 2×10 3 Mineralized water with a mineralization of 3 × 10 mg / L was used to mix the silicon-based nano drag-reducing agent and sodium α-olefin sulfonate from Examples 1-3 with formation water (mineralization 3 × 10 mg / L). 4 A solution with a total mass concentration of 0.3% was prepared by dissolving the crude oil (mg / L) in water. The solution and dehydrated crude oil (shear rate 7.34 s⁻¹ at 75 °C) were then mixed in a graduated cylinder with a volume of 50 mL. -1 An emulsion system with a total volume of 30 mL was prepared using water-oil volume ratios of 4:6, 5:5, 6:4, 7:3, and 8:2 (with water contents of 40%, 50%, 60%, 70%, and 80% respectively). The mixture was then sealed. The mixture was stirred in a 75°C water bath for 30 min, and the emulsification was observed. After stirring, the shear rate was measured using a DV-III viscometer at 75°C to be 7.34 s⁻¹. -1 The apparent viscosity of the emulsion was tested, and the specific results are shown in Table 1.

[0036] Table 1. Viscosity of the emulsion formed by silicon-based nanofluids and crude oil As can be seen from the results in Table 1, the silicon-based nano-in-situ emulsifying drag reducer in each embodiment can be adsorbed at the oil-water interface under shear induction, and can form Pickering emulsion under conditions of water content of 40% to 80%. Since the Pickering emulsion has a lower viscosity than crude oil, it has the function of improving crude oil viscosity and increasing crude oil recovery rate.

[0037] IV. Performance test of interfacial tension reduction of silicon-based nanofluids: The interfacial tension (IFT) of crude oil (viscosity 723.7 mPa·s) was measured after being dropped into the formation water solution of Example 1 using a rotating drop interfacial tensiometer. Crude oil was also dropped into formation water not used in the example as a control group. The measured interfacial tension of the control group was 21.6 mN / m. The measurement results of Example 1 are as follows: Figure 3 As shown, the interfacial tension (IFT) of the system after mixing crude oil with the solution from Example 1 can be reduced to about 0.5 mN / m, proving that the silicon-based nanofluid in this invention has a good effect on reducing interfacial tension.

[0038] V. Performance test of silicon-based nanofluids in improving rock wettability: At 75°C, oleophilic rock sheets were immersed in the silicon-based nanofluid of Example 1. The initial contact angle between the rock sheet surface, simulated water, and crude oil was 136°. The improvement in wettability was evaluated by measuring the contact angle between the oleophilic rock sheet surface, simulated water, and crude oil. The results are as follows: Figure 4 As shown, from Figure 4 As can be seen, after soaking for 24 hours, the contact angle between the oleophilic rock surface, simulated water, and crude oil decreased from 136° to 44°, indicating that silicon-based nanofluids can improve the oleophilic surface of rocks into a hydrophilic surface, significantly improving wettability.

[0039] VI. Oil displacement performance test: Example 1 uses homogeneous core samples to study formation water (mineralization 3×10⁻⁶) at 75°C. 4 mg / L, Ca 2+ Mg 2+ The concentrations were 2×10 3 The oil displacement capacity of a silicon-based nanofluid with a mass concentration of 0.3% (mg / L) was assessed. The homogeneous core sample had a gas permeability of 200 mD, a diameter of 2.5 cm, and a length of 5 cm. The injection rate during the displacement process was 0.5 mL / min. The experimental results are as follows: Figure 5 As shown. By Figure 5 As can be seen, the recovery rate in the pre-water drive stage was 34%. Subsequently, the solution of Example 1 was injected. During the injection process, the injection pressure decreased, and O / W type emulsion was observed at the core outlet. This indicates that the silicon-based nanofluid emulsified with crude oil to form a low-viscosity emulsion, which improved the mobility ratio during the displacement process and ultimately increased the recovery rate by 24.75%.

[0040] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.

Claims

1. A method for preparing silicon-based nanofluids, characterized in that, Includes the following steps: Step S1: Nano-silica and silane coupling agent are purged with nitrogen in anhydrous ethanol solution for at least 30 min to remove oxygen. The reaction is carried out in a sealed environment at 70℃~80℃ for 6h~8h with stirring. Then, diethanolamine is slowly added dropwise and stirred vigorously until homogeneous. After purging with nitrogen for at least 30 min, the reaction is carried out in a sealed environment at 70℃~80℃ with stirring for 10h~12h. The product is collected, purified, and dried to obtain tertiary amine functionalized SiO2. Step S2: Disperse tertiary amine-functionalized SiO2 in anhydrous acetonitrile, ultrasonically disperse it evenly, add bromododecane, purge with nitrogen, stir and reflux at 80℃~85℃ for 24h~48h, cool to room temperature, centrifuge to separate the solid product, purify and dry to obtain silicon-based nano drag-reducing agent. Step S3: Disperse the silicon-based nano drag reducer and sodium α-olefin sulfonate in water and ultrasonically vibrate for 20-40 minutes to obtain the final product.

2. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The particle size of the nano-silica is 10nm~30nm.

3. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The ratio of nano-silica to silane coupling agent in step S1 is 1:0.5~3 by weight.

4. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

5. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The ratio of nano-silica to diethanolamine in step S1 is 1:1 to 2.5 by weight.

6. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The ratio of tertiary amine functionalized SiO2 to bromododecane in step S2 is 1:1.2~1.5 by weight.

7. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: By weight, the ratio of silicon-based nano drag-reducing agent to sodium α-olefin sulfonate in step S3 is 1:0.2~0.

5.

8. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The total mass fraction of the silicon-based nano drag reducer and sodium α-olefin sulfonate dispersed in water in step S3 is 0.3%~0.5%.

9. The method for preparing a silicon-based nanofluid according to claim 1, characterized in that: The carbon chain range of the sodium α-olefin sulfonate is C. n =14~16.

10. A silicon-based nanofluid, characterized in that, It is prepared by any one of the methods described in claims 1 to 9.

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