Silicon / carbon-based nano chemically-energized polymer viscosity reducer and preparation method thereof

Abstract

The invention discloses a silicon / carbon-based nano chemically-energized polymer viscosity reducer and a preparation method thereof, and relates to the technical field of oilfield chemistry. The preparation method of the viscosity reducer comprises the following steps: modifying nano silicon dioxide or carbon quantum dots by using a silane coupling agent with double bonds, then sequentially adding N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, a sodium alpha-olefin sulfonate monomer and the modified nano silicon dioxide or the modified carbon quantum dots into deionized water, and uniformly stirring to obtain the viscosity reducer. A peroxide is used as an initiator, and a polymer chain is grafted to the hydrophobic nano silicon dioxide or the modified carbon quantum dots through a free radical copolymerization reaction in an aqueous solution to obtain a target product. The viscosity reducer disclosed by the invention has excellent long-term stability and shear resistance under the conditions of high temperature (130 DEG C) and high salinity (the degree of mineralization is 250,000 mg / L), can greatly reduce the viscosity of crude oil by 90% or more under the underground condition, and can reduce the oil-water interfacial tension and improve the oil displacement efficiency, thereby greatly improving the recovery rate of the crude oil.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, in particular to a silicon / carbon-based nano-chemically enabled polymer viscosity reducer and a preparation method thereof. Background Art

[0002] Polymer flooding is an important technology for enhancing oil recovery. It involves adding high-molecular-weight polymers to the injected water to increase its viscosity and improve the oil-water mobility ratio. However, traditional polymers can degrade under high-temperature and high-salinity conditions, thus affecting oil recovery efficiency. In recent years, the rise of nanotechnology has provided new methods for improving material properties at the molecular level, offering new insights into heavy oil recovery.

[0003] Among various nanomaterials, nano-silica and carbon quantum dots stand out due to their unique chemical structure and excellent physical properties, becoming a research hotspot in nanomaterials. Their surfaces contain a large number of active hydroxyl groups (-OH), which can be hybridized with organic compounds through surface modification to give nano-silica and carbon quantum dots more functional properties, such as hydrophilicity and surface activity. In addition, nano-silica and carbon quantum dots also have good thermal and chemical stability and can be used in high temperature and complex conditions. Therefore, the excellent properties of nano-silica and carbon quantum dots can be used to enhance the stability of polymer solutions and the oil displacement effect.

[0004] Feng Y et al. demonstrated that mixing nanosilica with HPAM can effectively improve the rheological properties and long-term stability of polymer solutions. Maghzi A et al. used microscopic displacement experiments to demonstrate that nanosilica with a certain degree of interfacial activity, assisted by HPAM, can improve the oil washing efficiency of medium-heavy oil. Currently, some oil displacement agents achieve oil displacement or viscosity reduction by introducing functional monomers into nanomaterials, but these still suffer from insufficient temperature and salt tolerance. For example, some viscosity reducers graft polymer chains onto nanomaterials through hydrogen bonding or physical adsorption. In high-temperature and high-salt environments, hydrogen bonds are easily degraded and dissociated, and under downhole shear forces, polymer chains are easily detached from the nanomaterial surface, reducing the displacement effect and potentially clogging formation pores. Summary of the Invention

[0005] In view of this, the present invention proposes a silicon / carbon-based nanochemically enabled polymer viscosity reducer and a preparation method thereof, which uses a silane coupling agent with a double bond to modify nano-silica / carbon quantum dots, and then reacts with N-hydroxymethyl acrylamide (NMA), sodium 2-acrylamido-2-methylpropanesulfonate (AMPS), and sodium α-olefin sulfonate (AOS) through free radical polymerization to obtain a silicon / carbon-based nanochemically enabled polymer viscosity reducer. The preparation method has the advantages of simple operation and low organic solvent consumption, and the viscosity reducer has the advantages of temperature resistance, salt resistance, and shear resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: A method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer comprises the following steps: S1, adding a silane coupling agent containing double bonds to the surface of nano-silica or carbon quantum dots to obtain modified nano-silica / carbon quantum dots; S2. Dissolve N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and sodium α-olefin sulfonate in deionized water in sequence, and adjust the pH value of the mixed solution to 6.0-8.0; add modified nano-silica / carbon quantum dots and an initiator to the mixed solution, and continue stirring the reaction under a nitrogen atmosphere. After the reaction is completed, naturally cool to room temperature to obtain a silicon / carbon-based nano-chemically enabled polymer viscosity reducer.

[0007] As a specific embodiment of the present invention, the nano-silica is solid hydrophobic nano-silica with a particle size of 5 to 50 nm; the particle size of the carbon quantum dots is 3 to 20 nm.

[0008] As a specific embodiment of the present invention, step S1 includes: S11, placing the nano-silica or carbon quantum dots in an oven to dry, thereby removing surface and internal moisture; S12. Add a silane coupling agent containing a double bond into an anhydrous organic solvent and stir until it is completely dissolved; add the dried nano-silica / carbon quantum dots into the silane coupling agent solution, continue stirring under a nitrogen atmosphere, and naturally cool to room temperature after the reaction is completed. Purify and dry to obtain modified nano-silica / carbon quantum dots.

[0009] As a specific embodiment of the present invention, the mass ratio of the dried nano-silica / carbon quantum dots to the silane coupling agent is 10:0.5-1.

[0010] As a specific embodiment of the present invention, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570), vinyltriethoxysilane, vinyltrimethoxysilane or γ-acryloxypropyltriethoxysilane.

[0011] As a specific embodiment of the present invention, the reaction conditions of the nano-silica / carbon quantum dots and the silane coupling agent are: reacting at 50-60° C. for 6-8 hours.

[0012] As a specific embodiment of the present invention, the mass ratio of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium α-olefin sulfonate is 1:1.2~3.6:1.2~3.6:1.2~3.6.

[0013] As a specific embodiment of the present invention, the initiator used is a peroxide, and the amount of peroxide used is 0.5% to 2% by weight of the total mass of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium α-olefin sulfonate.

[0014] As a specific embodiment of the present invention, the reaction conditions of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and sodium α-olefin sulfonate are: sealed and stirred at 50-60° C. for 2-8 hours.

[0015] A silicon / carbon-based nano-chemically enabled polymer viscosity reducer is prepared by the above-mentioned preparation method.

[0016] The present invention includes a silane coupling agent containing double bonds on the surface branches of nano-silica or carbon quantum dots. The silane coupling agent with double bonds can better participate in free radical polymerization reactions with polymer monomers, achieving a strong chemical bond connection between nano-silica / carbon quantum dots and polymers, and significantly improving the stability and durability of the viscosity reducer in high-temperature and high-salt environments. Among the monomers of the present invention, N-hydroxymethyl acrylamide (NMA) enhances the thermal stability, chemical stability and multifunctionality of the structure through its hydroxymethyl group, which makes it superior to traditional acrylamide in certain demanding applications; sodium α-olefin sulfonate (AOS) has excellent surface activity, environmental friendliness, hard water resistance, temperature resistance, salt resistance and economy compared to other sodium sulfonate salts. It can also better allow silica / carbon quantum dots to be evenly dispersed in water and better participate in polymerization reactions. The monomer combination of the present invention provides a wide range of performance adjustment space, allowing the viscosity reducer to adapt to various reservoir conditions and enhance the oil displacement effect. The high efficiency and controllability of the free radical polymerization reaction also make it easier to adjust the molecular weight and structure of the polymer, optimizing the performance of the viscosity reducer.

[0017] In summary, the technical effects of the present invention are: (1) The synthesis method of the silicon / carbon-based nanochemically enabled polymer viscosity reducer of the present invention is simple and the principle is reliable. The free radical polymerization reaction is carried out in deionized water, which reduces the consumption of organic solvents, is environmentally friendly, and reduces potential environmental impact. At the same time, the viscosity reducer of the present invention has high performance and low production cost, which makes it have significant economic advantages in large-scale industrial applications.

[0018] (2) The silicon / carbon-based nano-chemically enabled polymer viscosity reducer in the present invention can induce oil-water emulsification to form an oil-in-water emulsion, significantly reducing the viscosity of crude oil by more than 90%; at the same time, it can effectively increase the viscosity of the water phase, expand the sweep coefficient, reduce the oil-water interfacial tension, and improve the oil displacement efficiency, thereby significantly improving the crude oil recovery rate.

[0019] (3) The silicon / carbon-based nanochemically enabled polymer viscosity reducer of the present invention has excellent long-term stability, temperature resistance (130°C), salt resistance (mineralization 250,000 mg / L), and shear resistance. It is suitable for water injection development of heavy oil reservoirs including high temperature and high salinity, and has a wide range of heavy oil applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a reaction flow chart for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer in the present invention; Figure 2 This is the infrared characterization result of the silicon / carbon-based nano-chemically enabled polymer viscosity reducer of the present invention; Figure 3 This is a graph showing the thermogravimetric characterization results of the silicon / carbon-based nano-chemically enabled polymer viscosity reducer of the present invention; Figure 4 This is a microscopic morphology of the silicon / carbon-based nano-chemically enabled polymer viscosity reducer of the present invention; Figure 5 This is a graph showing the results of emulsion droplets in simulated formation water before and after intervention with the silicon / carbon-based nano-chemically enabled polymer viscosity reducer of the present invention; Figure 6 This is a graph showing the results of the silicon / carbon-based nano-chemically enabled polymer viscosity reducer of the present invention reducing the oil-water interfacial tension; Figure 7 This is an oil displacement performance evaluation diagram of Example 1 of the present invention; Figure 8 This is an oil displacement performance evaluation diagram of Example 2 of the present invention; Figure 9 This is an oil displacement performance evaluation diagram of Example 3 of the present invention; Figure 10 This is an oil displacement performance evaluation diagram of Example 4 in the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used therein are all commercially available unless otherwise specified.

[0022] Example 1

[0023] Step S1: 100 ml of ethanol was added to a 250 mL three-necked flask, 1 g of KH570 was slowly added to the ethanol, and stirred with a magnetic stirrer until completely dissolved. Then, 10 g of hydrophobic nano-silica (20 nm) was added, and ultrasonic oscillation was performed for 30 minutes to uniformly disperse the nano-silica. Then, nitrogen was passed through the flask to deoxygenate for 30 minutes, and the grafting reaction was carried out in a sealed and stirred oil bath at 60°C for 6 hours. The modified nano-silica was purified and dried to obtain the modified nano-silica. Step S2: Add 100 mL of deionized water, 4.5 g of N-hydroxymethyl acrylamide, 2.7 g of sodium 2-acrylamido-2-methylpropanesulfonate, and 1.8 g of α-olefin sulfonate to a 250 mL three-necked flask, stir until all solids are completely dissolved, and adjust the pH to 6.5 with 5% NaOH solution; stir magnetically and heat, and slowly add 1.5 g of the modified silica prepared in step S1 during the heating process; after the temperature is raised to 60°C, add 0.21 g of potassium persulfate as an initiator, deoxygenate with nitrogen for 30 minutes, and stir the reaction for 6 hours; after the reaction is completed, naturally cool to room temperature to obtain a silicon-based nanochemically enabled polymer viscosity reducer.

[0024] Example 2

[0025] Step S1: 100 ml of ethanol was added to a 250 mL three-necked flask, 1 g of KH570 was slowly added to the ethanol, and stirred with a magnetic stirrer until completely dissolved. Then, 10 g of hydrophobic nano-silica (20 nm) was added, and ultrasonic oscillation was performed for 30 minutes to uniformly disperse the nano-silica. Then, nitrogen was passed through the flask to deoxygenate for 30 minutes. The grafting reaction was carried out in a sealed and stirred oil bath at 60°C for 6 hours. The modified nano-silica was purified and dried to obtain the modified nano-silica. Step S2: Add 100 mL of deionized water, 3.6 g of N-hydroxymethyl acrylamide, 2.7 g of sodium 2-acrylamido-2-methylpropanesulfonate, and 2.7 g of α-olefin sulfonate to a 250 mL three-necked flask, stir until all solids are completely dissolved, and adjust the pH to 7.0 with 5% NaOH solution; stir magnetically and heat, and slowly add 1.5 g of the modified silica prepared in step S1 during the heating process; after the temperature is raised to 60°C, add 0.21 g of potassium persulfate as an initiator, deoxygenate with nitrogen for 30 minutes, and stir the reaction for 6 hours; after the reaction is completed, naturally cool to room temperature to obtain a silicon-based nanochemically enabled polymer viscosity reducer.

[0026] Example 3

[0027] Step S1: 100 ml of ethanol was added to a 250 mL three-necked flask, 1 g of KH570 was slowly added to the ethanol, and stirred with a magnetic stirrer until completely dissolved. Then, 10 g of hydrophobic nano-silica (20 nm) was added, and ultrasonic oscillation was performed for 30 minutes to uniformly disperse the nano-silica. Then, nitrogen was passed through the flask to deoxygenate for 30 minutes, and the grafting reaction was carried out in a sealed and stirred oil bath at 60°C for 6 hours. The modified nano-silica was purified and dried to obtain the modified nano-silica. Step S2: Add 100 mL of deionized water, 2.7 g of N-hydroxymethyl acrylamide, 1.8 g of sodium 2-acrylamido-2-methylpropanesulfonate, and 4.5 g of α-olefin sulfonate to a 250 mL three-necked flask, stir until all solids are completely dissolved, and adjust the pH to 7.5 with 5% NaOH solution; stir magnetically and heat, and slowly add 1.5 g of the modified silica prepared in step S1 during the heating process; after the temperature is raised to 60°C, add 0.21 g of potassium persulfate as an initiator, deoxygenate with nitrogen for 30 minutes, and stir the reaction for 6 hours; after the reaction is completed, naturally cool to room temperature to obtain a silicon-based nanochemically enabled polymer viscosity reducer.

[0028] Example 4

[0029] Step S1 (laboratory-made carbon quantum dots): add 2.5g urea and 1.8g sodium citrate to the reaction vessel, grind them into fine powder particles, stir them thoroughly to mix them evenly, and heat them to 60°C in a water bath; add 1.1g of the modifier cetearyl alcohol polyoxyethylene ether-20 preheated to 60°C to the mixed powder of urea and sodium citrate, and stir quickly to a white paste; heat the white paste to 180°C and keep the reaction at a constant temperature for 2h to obtain a preliminarily synthesized brown-black solid product; mechanically grind the brown-black solid product into fine powder particles and transfer it into a beaker, add anhydrous ethanol as a cleaning agent, and repeatedly wash it three times with ultrasonic waves, and then dry it at 70°C to obtain a preliminarily purified brown-black powder product. The brown-black powder product after preliminary purification was dissolved in ultrapure water, and the obtained dark brown solution was placed in a centrifuge and centrifuged at a speed of 4000r / min for 20 minutes to separate impurities; the supernatant from the centrifuge bottle was filtered and purified using ultrafiltration membranes with pore sizes of 0.45 microns and 0.22 microns in sequence, and then the filtered solution was added to a dialysis bag with a cutoff molecular weight of 1000D and dialyzed continuously in ultrapure water for several hours. During this period, the ultrapure water outside the dialysis bag was replaced several times until the outside of the dialysis bag was a colorless clear liquid. The supernatant in the dialysis bag was then dried at 70°C to finally obtain a brown-black powdery solid, which is the tracer-activated carbon quantum dot (this preparation method is derived from patent application number CN202410846099). Step S2: 100 ml of ethanol was added to a 250 mL three-necked flask, 1 g of KH570 was slowly added to the ethanol, and stirred with a magnetic stirrer until completely dissolved. Then, 10 g of homemade carbon quantum dots were added and ultrasonically oscillated for 30 min to uniformly disperse the carbon quantum dots. After that, nitrogen was passed through the flask for deoxygenation for 30 min. The grafting reaction was sealed and stirred in an oil bath at 60°C for 6 h. The modified carbon quantum dots were purified and dried. Step S3: Add 100 mL of deionized water, 4.5 g of N-hydroxymethyl acrylamide, 2.7 g of sodium 2-acrylamido-2-methylpropanesulfonate, and 1.8 g of α-olefin sulfonate to a 250 mL three-necked flask, stir until all solids are completely dissolved, and adjust the pH to 8.0 with 5% NaOH solution; stir magnetically and heat, and slowly add 1.5 g of the modified carbon quantum dots prepared in step S1 during the heating process; after the temperature is raised to 60°C, add 0.26 g of potassium persulfate as an initiator, deoxygenate with nitrogen for 30 minutes, and stir the reaction for 6 hours; after the reaction is completed, naturally cool to room temperature to obtain a carbon-based nanochemically enabled polymer viscosity reducer.

[0030] To better illustrate the technical effects of the present invention, performance evaluations of relevant embodiments are provided below.

[0031] 1. Gel Permeation Chromatography (GPC) Characterization of Silicon / Carbon-Based Nano-Chemical-Enabled Polymer Viscosity Reducers: The reaction process and product structure of the preparation of silicon / carbon-based nano-chemically enabled polymer viscosity reducer are as follows: Figure 1 The silicon / carbon-based nanochemically enabled polymer viscosity reducers in Examples 1, 2, 3, and 4 were characterized by gel permeation chromatography, and the number average molecular weights of the products are shown in Table 1. Comparing the molecular weights of the monomers used in the synthesis, N-hydroxymethyl acrylamide (NMA), sodium 2-acrylamido-2-methylpropanesulfonate (AMPS), and sodium α-olefin sulfonate (AOS), it can be found that the molecular weights of Examples 1, 2, 3, and 4 increased significantly. This is due to the growth of the molecular chains of the synthesized products after the polymerization reaction is completed.

[0032]

[0033] 2. Fourier transform infrared spectroscopy (FTIR) characterization of silicon / carbon-based nanochemically enabled polymer viscosity reducers: The silicon-based nano-chemical enabled polymer viscosity reducer products of Examples 1-4 were subjected to infrared characterization tests, and the results were as follows: Figure 2 shown.

[0034] For Examples 1-3, 429 cm -1 and 1633cm -1 The absorption peaks near the stretching vibration of Si-OH and surface water are 1107 cm -1and 803cm -1 The absorption peaks near the center are the antisymmetric and symmetric stretching vibration absorption peaks of Si-O-Si, 470 cm -1 Nearby is the Si-O-Si bending vibration peak, and the broad peak at 1000-1110 cm⁻¹ is the Si-OC vibration peak, indicating that the modified SiO2 is covalently linked to the polymer chain via the double bond of KH-570. The C=C stretching vibration peak at 1630-1680 cm⁻¹ for the three monomers is significantly reduced in intensity in Examples 1-3. Furthermore, C-H stretching vibration peaks appear at 1450-1470 cm⁻¹ and 2800-3000 cm⁻¹, indicating the opening of the double bond and the formation of a C-C backbone. The S=O symmetric / antisymmetric stretching vibration peaks at 1040 cm⁻¹ and 1190 cm⁻¹ are characteristic peaks of the sulfonic acid group, demonstrating that the sulfonic acid group was not hydrolyzed during the reaction, maintaining the product's salt resistance. Compared with the synthetic monomers, the OH stretching vibration peak (3300-3500 cm⁻¹) of Examples 1-3 weakened, and the CO stretching vibration peak (1100 cm⁻¹) enhanced, indicating that the hydroxymethyl group participated in the condensation.

[0035] For Example 4, 1607 cm -1 The absorption peak near the quantum dot aromatic condensed ring stretching vibration absorption peak; 2800-3000cm -1 The C-H stretching vibration peak appears, indicating that the double bond opens and forms a C-C main chain. -1 and 1186cm -1 The peaks of OH stretching vibration (3300-3500 cm) of Example 4 are the S=O symmetric / antisymmetric stretching vibration peaks, which are the characteristic peaks of sulfonic acid groups. This proves that the sulfonic acid groups are not hydrolyzed during the reaction, which can maintain the salt resistance of the product. -1) The CO stretching vibration peak (1104 cm -1 ) is enhanced, indicating that the hydroxymethyl group participates in the condensation, indicating that the carbon quantum dots are covalently linked to the polymer chain to form a carbon quantum dot-enabled polymer.

[0036] 3. Thermogravimetric (TGA) characterization of silicon / carbon-based nanochemically enabled polymer viscosity reducers: The silicon / carbon-based nano-chemically enabled polymer viscosity reducer products in Examples 1, 2, 3, and 4 were subjected to thermogravimetric testing. The results were as follows: Figure 3 It can be seen that the heat loss of the products of each example mainly occurs at 200-450°C, which is mainly caused by the thermal decomposition of the polymer chains grafted on the surface at high temperatures, which also proves the effectiveness of the polymer chains of the synthesized products at high temperatures.

[0037] 4. Transmission electron microscopy (TEM) characterization of silicon / carbon-based nanochemically enabled polymer viscosity reducers: The silicon-based nano-chemically enabled polymer viscosity reducer products in Examples 1, 2, 3, and 4 were characterized by transmission electron microscopy. The microscopic morphologies of the products are shown in FIG. Figure 4 As shown, the particle size of the example product is larger than the average particle size of the nano-silica and carbon quantum dots before modification, and a polymer coating layer can be clearly observed on the surface of the nanomaterial, proving that the three monomers have been successfully grafted onto the surface of the nano-silica and carbon quantum dots.

[0038] The above characterization tests show that Examples 1, 2, 3 and 4 all successfully prepared silicon / carbon-based nano-chemically enabled polymer viscosity reducers.

[0039] 5. Viscosity test of silicon / carbon-based nano-chemically enabled polymer viscosity reducer solution: Using simulated formation water (mineralization 25×10 4 mg / L, Ca 2+ Mg 2+ The concentrations were 1.2×10 4 mg / L) were used to prepare 1.0 wt% solutions of Examples 1, 2, 3, and 4, respectively. 0.5 wt% thiourea was then added, the mixture was sealed, and the mixture was aged at 130°C for 60 days. The viscosity of the solutions of each example at 90°C was measured using a DV-III viscometer. The results are shown in Table 2. It can be seen that the silicon / carbon-based nanochemically enabled polymer viscosity reducer maintains excellent stability under high temperature and high salinity conditions, with a viscosity retention rate exceeding 90%, effectively increasing the viscosity of the aqueous phase and thereby expanding the sweep coefficient.

[0040]

[0041] 6. Emulsification and viscosity reduction performance test of silicon / carbon-based nano-chemically enabled polymer viscosity reducer: Using simulated formation water (mineralization 25×10 4 mg / L, Ca 2+ Mg 2+ The concentrations were 1.2×10 4 mg / L) were used to prepare 0.3 wt% solutions of Examples 1, 2, 3 and 4. In a 50 mL graduated cylinder, the solutions and dehydrated crude oil (at 90 °C with a shear rate of 7.34 s -1 The viscosity was 723 mPa·s) and the mixed solution with a total volume of 30 mL was prepared at a water-oil volume ratio of 5:5, 6:4, 7:3, and 8:2; then, the mixed solution was stirred at 1000 r / min for 30 min in a 90°C water bath. The emulsification was observed and a DV-III viscometer was used at 90°C and a shear rate of 7.34 s -1 The viscosity of the emulsion was tested under the following conditions, and the results are shown in Table 3.

[0042] The results show that silicon / carbon-based nano-chemically enabled polymer viscosity reducers can form water-in-oil emulsions (such as Figure 5 It can significantly reduce the viscosity of crude oil, with the highest viscosity reduction rate reaching 96%, thereby significantly enhancing the fluidity of crude oil.

[0043]

[0044] VII. Test of the interfacial tension reduction performance of silicon / carbon-based nano-chemically enabled polymer viscosity reducers: Using simulated formation water (mineralization 10×10 4 mg / L, Ca 2+ Mg 2+ The concentrations were 0.5×10 3 mg / L) were used to prepare solutions of 0.3 wt% of Examples 1, 2, 3 and 4. The interfacial tension of crude oil in the aqueous solution of the examples and the simulated formation water was measured using a Kruess SDT spinning drop interfacial tension meter at 75°C. The measurement results are shown in the figure. Figure 6 As shown in the figure, the interfacial tension of crude oil in the four examples ranges from 0.086 to 0.98 mN / m, which is significantly lower than the interfacial tension of crude oil in formation water. This indicates that the silicon / carbon-based nanochemically enabled polymer viscosity reducer of the present invention can effectively reduce the oil-water interfacial tension.

[0045] 8. Physical simulation oil displacement performance test of silicon / carbon-based nano-chemically enabled polymer viscosity reducer: The homogeneous core was used to study the simulated formation water (mineralization 20×10 4 mg / L, Ca 2+ Mg 2+ The concentrations were 1×10 4 mg / L), wherein the gas permeability of the homogeneous core is 500 mD; the diameter is 2.5 cm, and the length is 5 cm; the injection rate during the displacement process is 0.2 mL / min, and the injection concentration of the nanochemically enabled polymer viscosity reducer is 0.6 PV.

[0046] The experimental results of Example 1 are as follows Figure 7 As shown, the recovery factor of the water flooding stage is 40.2%. Subsequently, a solution of the system of Example 1 with a concentration of 0.3 wt% was injected. During the injection process, the injection pressure first decreased and then increased. The displaced liquid was observed at the core outlet. It can be found that the silicon-based nano-chemically enabled polymer viscosity reducer formed a low-viscosity O / W emulsion during the process of displacing crude oil, ultimately increasing the recovery factor by 25.4%.

[0047] The experimental results of Example 2 are as follows Figure 8As shown, the recovery factor of the first water flooding stage is 39.8%; then, a solution of the system of Example 2 with a concentration of 0.3 wt% is injected. During the injection process, the injection pressure first decreases and then increases. By observing the displaced liquid at the core outlet, it can be found that the silicon-based nano-chemically enabled polymer viscosity reducer forms a low-viscosity O / W emulsion during the process of displacing crude oil, ultimately increasing the recovery factor by 28.7%.

[0048] The experimental results of Example 3 are as follows Figure 9 As shown, the recovery factor of the front water flooding stage is 43.8%; then, a solution of the system of Example 3 with a concentration of 0.3 wt% is injected. During the injection process, the injection pressure first decreases and then increases. By observing the displaced liquid at the core outlet, it can be found that the silicon-based nano-chemically enabled polymer viscosity reducer forms a low-viscosity O / W emulsion during the process of displacing crude oil, ultimately increasing the recovery factor by 27.3%.

[0049] The experimental results of Example 4 are as follows Figure 10 As shown, the recovery factor of the water flooding stage was 38.12%. Subsequently, a solution of the system of Example 4 with a concentration of 0.3 wt% was injected. During the injection process, the injection pressure first decreased and then increased. The displaced liquid was observed at the core outlet. It was found that the carbon-based nano-chemically enabled polymer viscosity reducer formed a low-viscosity O / W emulsion during the process of displacing crude oil, ultimately increasing the recovery factor by 22.6%.

[0050] 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 changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer, characterized in that: The following steps are involved: S1, adding a silane coupling agent containing double bonds to the surface of nano-silica or carbon quantum dots to obtain modified nano-silica / carbon quantum dots; S2. Dissolve N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and sodium α-olefin sulfonate in deionized water in sequence, and adjust the pH value of the mixed solution to 6.0-8.0; add modified nano-silica / carbon quantum dots and an initiator to the mixed solution, and continue stirring the reaction under a nitrogen atmosphere. After the reaction is completed, naturally cool to room temperature to obtain a silicon / carbon-based nano-chemically enabled polymer viscosity reducer.

2. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The nano-silica is solid hydrophobic nano-silica with a particle size of 5-50 nm; the particle size of the carbon quantum dots is 3-20 nm.

3. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: Step S1 includes: S11, placing the nano-silica or carbon quantum dots in an oven to dry; S12. Add a silane coupling agent containing a double bond into an anhydrous organic solvent and stir until it is completely dissolved; add the dried nano-silica / carbon quantum dots into the silane coupling agent solution, continue stirring under a nitrogen atmosphere, and naturally cool to room temperature after the reaction is completed. Purify and dry to obtain modified nano-silica / carbon quantum dots.

4. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 3, characterized in that: The mass ratio of the dried nano-silica / carbon quantum dots to the silane coupling agent is 10:0.5-1.

5. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The silane coupling agent is γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane or γ-acryloxypropyltriethoxysilane.

6. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The reaction conditions of the nano-silica / carbon quantum dots and the silane coupling agent are: reacting at 50-60° C. for 6-8 hours.

7. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The mass ratio of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium α-olefin sulfonate is 1:1.2-3.6:1.2-3.6:1.2-3.

6.

8. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The initiator used is peroxide, and the amount of the peroxide used is 0.5% to 2% of the total mass of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium α-olefin sulfonate in parts by weight.

9. The method for preparing a silicon / carbon-based nano-chemically enabled polymer viscosity reducer according to claim 1, characterized in that: The reaction conditions of the modified nano-silica / carbon quantum dots, N-hydroxymethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and sodium α-olefin sulfonate are: sealed and stirred at 50-60° C. for 2-8 hours.

10. A silicon / carbon-based nano-chemically enabled polymer viscosity reducer, characterized in that: The method is as described in any one of claims 1 to 9.

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