Binary flooding strong emulsifying active agent based on nano silicon dioxide grafted anionic-nonionic structure as well as preparation method and application of binary flooding strong emulsifying active agent

Abstract

The invention discloses a binary flooding strong emulsifying active agent based on a nano silicon dioxide grafted anionic-nonionic structure as well as a preparation method and application of the binary flooding strong emulsifying active agent, and belongs to the field of active agents. The binary flooding strong emulsifying active agent based on the nano silicon dioxide grafted anionic-nonionic structure comprises a nano silicon dioxide core, an alkyl chain hydrophobic middle layer and a sulfonate-polyether bifunctional outer layer, the alkyl chain hydrophobic intermediate layer is grafted to the surface of SiO2 through a silane coupling agent by a Si-O-Si covalent bond; and the sulfonate-polyether bifunctional outer layer is composed of a sulfonate group-SO3H and a polyoxypropylene-polyoxyethylene PO-b-EO block copolymer. According to the technology, a traditional physical compounding mode is broken through, a sulfonate group and a polyether chain segment are accurately anchored to a nano-carrier through chemical bonds, molecular-level synergy of anion and nonionic functions is achieved, and the system is endowed with ultralow interfacial tension, strong emulsifying capacity and long-acting stability while the consumption of sulfonate is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to a binary drive strong emulsification active agent based on nano-silicon dioxide grafting anionic-nonionic structure and a preparation method and application thereof, and belongs to the active agent field. BACKGROUND

[0002] In the oil field chemical flooding enhanced oil recovery technology, the polymer / surfactant binary composite flooding has become the core technology for the development of high water cut reservoirs by synergistically reducing the oil-water interfacial tension and improving the mobility control. However, the existing binary drive system faces the following key bottlenecks in practical application:

[0003] 1. Insufficient performance of surfactant: the traditional sulfonate surfactant (such as petroleum sulfonate) is difficult to achieve ultra-low interfacial tension (<10 -3 mN / m) under non-alkali conditions, and has poor resistance to high salinity (invalid when Ca 2+ >5000mg / L), which limits the oil displacement efficiency.

[0004] 2. Poor emulsion stability: the emulsification ability of conventional surfactants for high viscosity crude oil is insufficient, and the emulsion water separation rate is generally >50%, which cannot form stable emulsion to block large pores.

[0005] 3. Defects in the application of nanomaterials: the existing technology mainly adopts physical compounding of nanomaterials and surfactants (nano-SiO2 and alkyl polyglycoside compounding), which has problems such as nanometer particle agglomeration (Zeta potential difference leads to precipitation rate >30%), poor long-term stability, etc.

[0006] 4. Environmental protection and cost pressure: the imported extended surfactant is expensive (>30,000 yuan / ton), and the sulfonate-containing system is prone to cause difficulties in produced liquid treatment, which does not meet the green development trend.

[0007] In recent years, the chemical modification technology of nanomaterials provides a new direction for solving the above problems. Studies have shown that by chemically bonding an amphiphilic functional layer on the surface of nanoparticles, the material can be given self-interfacial activity. However, the existing modification method only introduces a single functional group, which cannot form an anionic-nonionic synergistic structure, resulting in difficulty in balancing emulsification performance and interfacial activity. Therefore, it is urgent to develop a binary drive active agent based on chemical grafting modification of nano-silicon dioxide to break through the bottlenecks of traditional technology.

[0008] The current surfactant technology for binary drive in oil fields mainly focuses on five types of systems: sulfonate-based surfactants, nanomaterial compounding systems, biological surfactants, gemini / oligomeric surfactants, and extended surfactants. Each type of technology has significant limitations. The sulfonate-based system (such as Petrostep S1) achieves 10-3 ~10 -2 mN / m level interfacial tension, but poor salt resistance (Ca 2+ >5000mg / L, the performance decay is >50%), and >30% sulfonate needs to be added; nanomaterial compound system (such as SiO2-alkyl glycoside compound) reduces the interfacial tension to 10 by physically mixing nanoparticles with surfactants. -1 mN / m level, but the difference in Zeta potential between nanoparticles and surfactants (SiO2-8mV vs surfactant-25mV) causes phase separation, and the precipitation rate is >30% in 7 days; although biosurfactants (such as rhamnolipids) are environmentally friendly, they are expensive (>50,000 yuan / ton), and the interfacial tension is only 10 -2 mN / m level and poor temperature resistance (>60℃ inactivation); Gemini surfactants achieve 10 -4 mN / m level ultra-low tension, but the synthesis process is complex (requires more than 5 steps of reaction), and industrial scale-up is difficult; Extended surfactants insert polyoxypropylene chains into the hydrophobic chain, and the interfacial tension can reach 10 -4 mN / m level, but rely on imported C12-14 branched alcohol raw materials, with a cost exceeding 30,000 yuan / ton. These technologies are limited by performance shortcomings (such as salt tolerance and emulsion stability), high costs (bio-based / extended), or difficulty in industrialization (gemini-based). There is an urgent need to develop new surfactant systems that combine ultra-low interfacial tension, strong emulsification, high cost-effectiveness, and ease of mass production.

[0009] The technical defects of the surfactant system used in binary flooding for enhancing oil field recovery are as follows:

[0010] 1. Limited performance of traditional sulfonate systems: Although sulfonate surfactants (such as petroleum sulfonates) can provide anionic active groups, they need to be added in high concentrations (>30%) to achieve 10 -3 mN / m level interfacial tension and poor salt resistance (Ca 2+ >5000mg / L), and its emulsification capacity is insufficient (water separation rate >50%), which cannot meet the strong emulsification requirements of high water-content reservoirs;

[0011] 2. Stability defects of nanocomposite systems: Physically compounded nanomaterials (such as SiO2) and sulfonates have a Zeta potential conflict (-8mV vs. -25mV), resulting in phase separation (precipitation rate >30% in 7 days), and nanoparticles cannot directly participate in interfacial activity;

[0012] 3. Conflict between environmental protection and cost: The produced fluid of the sulfonate system is difficult to treat, while high-performance extended surfactants (such as the Alfoterra series) rely on imported raw materials (C12-14 branched alcohols), with a cost of up to 20,000 to 30,000 yuan per ton. SUMMARY

[0013] To solve the above problems, the core purpose of the present application is to integrate sulfonate functional groups and polyether chain segments onto the surface of nanosilica by chemical grafting to construct a "sulfonate-polyether" bifunctional nanoreagent. The following breakthroughs are achieved:

[0014] 1. Functional synergistic effect: by chemical bonding, sulfonate groups (anionic active sites) and polyether chain segments (nonionic emulsifying function) are precisely anchored on the surface of nanosilica to form a "anion-nonionic synergistic" structure, achieving a 10 -4 ~10 -5 mN / m level of ultra-low interfacial tension at a low concentration of 0.3%, while reducing the emulsion water separation rate to <3%;

[0015] 2. Improved salt resistance: the rigid skeleton of the nanosilica core and the chemical bonding functional layer provide a steric hindrance effect, allowing the reagent to remain stable (interfacial tension fluctuation <10%) under conditions of salinity >3x10 4 mg / L (Ca 2+ ≤8000mg / L);

[0016] 3. Cost reduction and environmental protection: by immobilizing sulfonate groups on the nanocarrier, the amount of sulfonate is reduced by 80% (sulfonate accounts for <5% of the total active ingredients), significantly reducing the sulfur content of the produced fluid, and the use of domestic raw materials allows cost control at <10,000 yuan / ton.

[0017] The present application aims to break through the technical bottlenecks of traditional sulfonate systems through nanomaterial chemical modification technology, providing a new type of binary flooding active agent that combines ultra-low interfacial tension, strong emulsifying ability, high salt resistance, and low cost.

[0018] According to a first aspect of the present application, a binary flooding strong emulsification active agent based on nanosilica grafting anion-nonionic structure is provided. On the nanosubstrate, the synergistic effect of sulfonate groups and polyether groups is achieved to reduce interfacial tension and emulsification and stabilization.

[0019] A binary flooding strong emulsification active agent based on nanosilica grafting anion-nonionic structure, comprising a nanosilica core, an alkyl chain hydrophobic intermediate layer, and a sulfonate-polyether bifunctional outer layer.

[0020] The alkyl chain hydrophobic intermediate layer is grafted to the SiO2 surface through a silane coupling agent with a Si-O-Si covalent bond;

[0021] The sulfonate-polyether bifunctional outer layer is composed of sulfonate groups -SO3H and polyoxypropylene-polyoxyethylene PO-b-EO block copolymer.

[0022] Optionally, the size of the nanosilica core is 50-80 nm.

[0023] Optionally, the PDI of the nanosilica core is <0.1, and the specific surface area is ≥200 m 2 / g.

[0024] The nanosilica core provides mechanical stability as a rigid carrier, preventing the active component from agglomeration.

[0025] Optionally, the silane coupling agent is 3-methacryloyloxypropyl trimethoxysilane, KH-570.

[0026] Optionally, in the alkyl chain hydrophobic intermediate layer, the alkyl chain is a C16-C18 straight chain alkyl.

[0027] The alkyl chain hydrophobic intermediate layer is used to enhance hydrophobicity and promote the directional adsorption of the nanoparticle at the oil-water interface.

[0028] Optionally, in the sulfonate-polyether bifunctional outer layer, the number of PO chain segments is 10-20, the number of EO chain segments is 5-15, and the proportion of sulfonate is ≤5wt%.

[0029] Optionally, in the sulfonate-polyether bifunctional outer layer, the PO / EO chain segment ratio is (2:1)-(5:1), the polyether chain molecular weight Mn is 2500-3500, and the PDI is ≤1.2; the sulfonate substitution degree is ≥80%.

[0030] Optionally, the PO / EO chain segment ratio is 3:1-5:1, and the sulfonation degree is 80%-90%.

[0031] The sulfonate-polyether bifunctional outer layer serves as an active layer, wherein 1) sulfonate groups: terminal -SO3H groups are introduced through sulfonation reaction (substitution degree > 85%), providing anionic active sites; 2) polyether segments: PO-b-EO block copolymer (PO:EO = 3:1, Mn = 3000), imparting nonionic emulsification function; 3) synergistic mechanism: sulfonate reduces interfacial tension to 10 -5 mN / m level, and the polyether chain stabilizes the emulsion through a hydrogen bond network.

[0032] According to a second aspect of the present application, a preparation method of a binary strong emulsification active agent based on nanosilica grafting anionic-nonionic structure is provided.

[0033] The preparation method of the binary strong emulsification active agent based on nanosilica grafting anionic-nonionic structure described above, the preparation method comprises:

[0034] a) Method for synthesizing SiO2 core;

[0035] b) grafting C16-C18 alkyl chains on the SiO2 core after modification with silane coupling agent by RAFT polymerization, grafting density 2.5-3.0 chains / nm 2 ;

[0036] c) growing PO-b-EO chains by ATRP method, sulfonating the end by chlorosulfonic acid, reaction temperature 80-90℃, molar ratio of sulfonating agent 1:(1.1-1.3).

[0037] Optionally, step a) comprises:

[0038] mixing ethanol, ammonia water, and water, adding tetraethyl orthosilicate dropwise, reacting, washing, and drying to obtain SiO2 particles;

[0039] The molar ratio of the tetraethyl orthosilicate, ethanol, and ammonia water is 1:(20-30):(0.5-0.8).

[0040] The reaction condition is 5-8h at room temperature.

[0041] Optionally, step b) comprises:

[0042] b-1) dispersing the SiO2 particles in ethanol, adding a silane coupling agent, refluxing, centrifugal washing, and drying to obtain silane coupling agent-modified SiO2 particles;

[0043] b-2) mixing the silane coupling agent-modified SiO2 particles, alkyl acrylate, RAFT reagent, and initiator, stirring under an inert atmosphere, and reacting to obtain alkylated SiO2 particles.

[0044] Optionally, step c) comprises:

[0045] c-1) mixing the alkylated SiO2 particles, initiator, and catalyst, first reacting with PO monomers and then reacting with EO monomers to obtain PO-b-EO grafted SiO2 particles;

[0046] c-2) dispersing the PO-b-EO grafted SiO2 particles in dichloromethane, adding chlorosulfonic acid, stirring and reacting, centrifugal washing, and drying to obtain the binary flooding strong emulsifying active agent based on nano-silica grafted anion non-structure.

[0047] According to a third aspect of the present application, an application of the binary flooding strong emulsifying active agent based on nano-silica grafted anion non-structure is provided.

[0048] The application of the binary flooding strong emulsifying active agent based on nano-silica grafted anion non-structure in oil reservoir binary flooding, the concentration of the binary flooding strong emulsifying active agent based on nano-silica grafted anion non-structure is 0.1%-0.5%.

[0049] The active agent is used in a reservoir binary flooding system with a salinity of ≥3×10 4 mg / L, the active agent concentration is 0.1% to 0.5%, the system viscosity retention rate is ≥95% after being compounded with a polymer (such as HPAM), and the interfacial tension is ≤1×10 -4 mN / m.

[0050] The present application breaks through the technical bottleneck of traditional binary surfactants by precisely constructing a "sulfonate-polyether-nanocarrier" triad active structure through chemical bonding, which is embodied in the following three aspects:

[0051] Nanocarrier functionalization innovation: For the first time, nanosilica is upgraded from an auxiliary material for physical compounding to a functionalized carrier for chemical grafting. Through silane coupling agent (KH-570) and controlled polymerization technology (RAFT / ATRP), an alkyl chain hydrophobic layer and a sulfonate-polyether dual-functional active layer are successively constructed on the surface of SiO2, realizing "one core with dual effects". The nanocore provides rigid support and steric hindrance, and the sulfonate group (-SO3H) and the non-ionic polyether chain (PO-b-EO) respectively undertake the functions of ultra-low interfacial tension and strong emulsification, replacing the defect that more than 30% active ingredients need to be added in traditional sulfonate systems (the sulfonate proportion in this system is <5%).

[0052] Anionic-nonionic synergistic mechanism: Through molecular design, the sulfonate group and the polyether chain segment form a hydrogen bond network and charge balance synergistic effect at the nanointerface. The sulfonate reduces the interfacial tension to the order of 10 -5 mN / m, and the polyether chain anchors the oil phase through the hydrophobic action of the PO segment and stabilizes the water phase through the hydrophilic EO segment, making the emulsion water separation rate <3%, while the Zeta potential is stabilized at -35mV, solving the phase separation problem of physical compounding.

[0053] Process and performance adjustability: A stepwise controllable grafting process is developed to adapt to different reservoir requirements (≤8×10 4 mg / L) by adjusting the PO / EO chain segment ratio (3:1 to 5:1), the sulfonation degree (80% to 90%), and the nanocore size (50-80nm), ensuring the feasibility of industrial mass production.

[0054] The beneficial effects that can be produced by the present application include:

[0055] The binary strong emulsification active agent based on nano-silica grafting anionic-nonionic structure, and a preparation method and application thereof, constructs a "sulfonate-polyether" bifunctional active layer on the surface of nano-silica through a chemical grafting technology, and forms a nano-composite oil displacement agent with self-interface activity. The technology breaks through the traditional physical compounding mode, precisely anchors the sulfonate group and the polyether chain segment to the nano-carrier through a chemical bond, realizes the molecular-level cooperation of anion and non-ion function, reduces the sulfonate dosage, and endows the system with ultra-low interfacial tension, strong emulsification capacity and long-term stability. DETAILED DESCRIPTION

[0056] The present application will be described in detail below in conjunction with examples, but the present application is not limited to these examples.

[0057] Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels.

[0058] Unless otherwise specified, the test methods all adopt conventional methods, and the instrument settings all adopt the recommended settings of the manufacturers.

[0059] Example 1

[0060] 1. Synthesis of nano-SiO2 core:

[0061] (1) Raw material ratio:

[0062] Tetraethyl orthosilicate (TEOS): ethanol: ammonia water (28wt%): deionized water = 1 mol: 25 mol: 0.6 mol: 4 mol; the ammonia water concentration is strictly controlled at 0.5-0.7 mol / L;

[0063] (2) Reaction process:

[0064] a. Add ethanol, ammonia water and water into a three-necked flask, and stir at 25°C at 500 rpm for 10 min;

[0065] b. Slowly add TEOS (add completely within 30 min), and continue to react for 6 h; ensure monodispersity, and monitor PDI < 0.1 by dynamic light scattering (DLS);

[0066] c. Centrifuge (8000 rpm, 15 min) to obtain SiO2 particles, wash with ethanol for 3 times, and vacuum dry at 60°C for 12 h;

[0067] It is tested that the diameter of the nano-SiO2 core is 50-80 nm, the PDI is verified to be < 0.1 by DLS, and the specific surface area is ≥200 m 2 / g by BET test.

[0068] 2. Alkyl chain hydrophobic layer grafting (silane coupling + RAFT polymerization):

[0069] (1) Silane coupling pretreatment:

[0070] a. SiO2 was dispersed in 200 mL anhydrous ethanol, KH-570 was added, and refluxed at 80 °C for 4 h;

[0071] b. The unreacted KH-570 was removed by centrifugal washing, and the KH-570 modified SiO2 was dried at 60 °C to obtain (FTIR appeared C=C characteristic peak at 1637 cm-1);

[0072] (2) RAFT grafting polymerization:

[0073] Reaction system: KH-570 / SiO2, hexadecyl acrylate (HDA), RAFT reagent (CDB), AIBN initiator, toluene;

[0074] Reaction conditions: stirring at 70 °C under nitrogen protection for 12 h;

[0075] Post-processing: centrifugal removal of homopolymer, toluene washing 3 times, vacuum drying;

[0076] (3) Characterization and verification:

[0077] TGA showed that the grafting rate was 18.5% (600 °C weight loss); the grafting density was 2.8 chains / nm 2 (through TGA weight loss 18.5%), contact angle 112°;

[0078] FT-IR appeared characteristic peaks at 2920 cm -1 (C-H stretching vibration), 1730 cm -1 (ester C=O).

[0079] 3. Sulfonate-polyether bifunctional layer construction (ATRP polymerization + sulfonation):

[0080] (1) ATRP method for grafting PO-b-EO chain:

[0081] Raw materials: alkylated SiO2, hydroxyethyl methacrylate (HEMA) initiator, PO monomer (propylene oxide), EO monomer, CuBr / PMDETA catalyst system (molar ratio 1:2).

[0082] Reaction conditions: in a high-pressure reaction kettle (nitrogen protection, pressure maintained at 0.5 MPa), 80 °C stepwise polymerization: first pass in PO for 6 h, then pass in EO for 4 h;

[0083] (2) Terminal sulfonation reaction:

[0084] PO-b-EO grafted SiO2 was dispersed in dichloromethane (100 mL), chlorosulfonic acid was added, and stirred at 80 °C for 3 h, centrifugal washing to neutral, vacuum drying;

[0085] (3)Quality control: sulfonation degree by elemental analysis (S content ≥ 3.2wt%); GPC verified polyether chain Mn = 3000, PDI = 1.15.

[0086] PO:EO = 3:1, sulfonate substitution degree ≥ 80%, verified by FT-IR at 1045 cm-1(S=O) and 1100 cm-1(C-O-C) characteristic peaks.

[0087] Comparative example

[0088] The sulfonate system compounded with the performance closest extender surfactant and component similar nano-SiO2 is used as a control.

[0089] The core component of the extender surfactant is branched alkyl polyoxyethylene polyoxypropylene ether sulfonate, mainly from Sinochem.

[0090] The specific composition of the nano-SiO2 compounded sulfonate system: the nanoparticles are hydrophilic fumed silica (Evonik 2 P25), particle size 12 nm, specific surface area 200 m -4 / g; petroleum sulfonate (Sinopec SLPS type), average molecular weight 450, sulfonation degree ≥ 85%; compounding ratio: SiO2: SLPS-1 = 1:5 (mass ratio). The active agent and polymer HPAM are compounded, the active agent concentration is 0.3%, and the following performance tests are carried out.

[0091] The test results of the examples and the comparative example are as follows:

[0092]

[0093] The core advantages of the application are summarized as follows:

[0094] 1. The performance is superior to that of the extender surfactant:

[0095] (1) The interfacial tension is reduced by one order of magnitude (10 -4 →10 -5 mN / m), and the salt resistance is improved by 60% (5000 → 8000 mg / L Ca 2+ );

[0096] (2) The strong emulsification function (water separation rate < 3%) is realized through the hydrogen bond network of the polyether chain, filling the performance gap of the extender surfactant in the emulsification field.

[0097] 2. Defects of the nano-compounded system are solved:

[0098]

[0099] (1) Chemical bonding instead of physical compounding, solving the problem of phase separation caused by Zeta potential conflict (30 days without precipitation vs. 7 days precipitation > 30%);

[0100] (2) The utilization rate of sulfonate is increased by 6 times (30% to 5%), and the cost of the same interfacial activity is significantly reduced (0.8 to < 10,000 yuan / ton).

[0101] 3. Double breakthrough of industrialization and environmental protection:

[0102] (1) All raw materials (SiO2, C16 alkyl chain, PO / EO monomer) can be localized, and the dependence on imported branched alcohol is eliminated;

[0103] (2) The sulfonate dosage is reduced by 80%, and the sulfur content of the produced liquid is reduced to 1 / 5 of the traditional system, meeting the requirements of green oilfield development.

[0104] The present application is through the "nano-carrier functionalization + anion-nonionic synergistic" innovative design, which comprehensively surpasses the prior art in interfacial activity, emulsifying capacity, salt resistance and cost control, and provides a new generation of binary flooding solution for high-salt high-water oil reservoirs.

[0105] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, the present application is not limited thereto. Any skilled person in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solution.

Claims

1. A binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure, characterized in that: The binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure comprises a nano-silica core, an alkyl chain hydrophobic middle layer and a sulfonate-polyether dual-functional outer layer; The alkyl chain hydrophobic intermediate layer is grafted to the SiO2 surface via Si-O-Si covalent bonds through a silane coupling agent; The sulfonate-polyether bifunctional outer layer is composed of a sulfonate group -SO3H and a polyoxypropylene-polyoxyethylene PO-b-EO block copolymer.

2. The binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure according to claim 1, characterized in that: The size of the nano-silicon dioxide core is 50-80 nm.

3. The binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure according to claim 1, characterized in that: In the alkyl chain hydrophobic middle layer, the alkyl chain is a C16-C18 straight chain alkyl.

4. The binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure according to claim 1, characterized in that: In the sulfonate-polyether bifunctional outer layer, the number of PO chain segments is 10-20, the number of EO chain segments is 5-15, and the proportion of sulfonate is ≤5wt%.

5. The binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure according to claim 1, characterized in that: In the sulfonate-polyether bifunctional outer layer, the PO / EO chain segment ratio is (2:1)-(5:1), the polyether chain molecular weight Mn=2500-3500, PDI≤1.2; and the sulfonate substitution degree is ≥80%.

6. The method for preparing the binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure according to any one of claims 1 to 5, characterized in that: The preparation method comprises: a) Method to synthesize SiO2 core; b) After the SiO2 core is modified with a silane coupling agent, C16-C18 alkyl chains are grafted via RAFT polymerization with a grafting density of 2.5-3.0 chains / nm 2 ; c) PO-b-EO chains were grown by ATRP and the ends were sulfonated by chlorosulfonic acid at a reaction temperature of 80-90°C and a sulfonating agent molar ratio of 1:(1.1-1.3).

7. The preparation method according to claim 6, characterized in that Step a) comprises: Mix ethanol, ammonia water and water, add ethyl orthosilicate dropwise, react, wash and dry to obtain SiO2 particles; The molar ratio of the tetraethyl orthosilicate, ethanol and ammonia water is 1:(20-30):(0.5-0.8); The reaction conditions are room temperature for 5-8 hours.

8. The preparation method according to claim 6, characterized in that Step b) comprises: b-1) dispersing SiO2 particles in ethanol, adding a silane coupling agent, refluxing, centrifuging, washing, and drying to obtain SiO2 particles modified with a silane coupling agent; b-2) SiO2 particles modified with a silane coupling agent, an alkyl acrylate, a RAFT agent, and an initiator are mixed, stirred, and reacted under an inert atmosphere to obtain alkylated SiO2 particles.

9. The preparation method according to claim 6, characterized in that Step c) comprises: c-1) mixing alkylated SiO2 particles, an initiator, and a catalyst, first adding PO monomer to react, and then adding EO monomer to react, to obtain PO-b-EO grafted SiO2 particles; c-2) dispersing the PO-b-EO grafted SiO2 particles in dichloromethane, adding chlorosulfonic acid, stirring for reaction, centrifuging and washing, and drying to obtain the binary flooding strong emulsifying active agent based on nano-silica grafted anionic non-structure.

10. Use of the nano-silica grafted anionic non-structural binary flooding strong emulsifying active agent according to any one of claims 1 to 5 in binary flooding of oil reservoirs, characterized in that: The concentration of the binary flooding strong emulsifying active agent based on nano-silicon dioxide grafted anionic non-structure is 0.1%-0.5%.

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