Self-emulsifying nano-composite profile control and flooding agent for oil field and preparation process thereof

Abstract

The application relates to the technical field of chemical oil displacement, and particularly discloses a self-emulsifying nano composite profile control and displacement agent for oil fields and a preparation process thereof. The self-emulsifying nano composite profile control and displacement agent for oil fields is prepared from the following raw materials in a mass ratio of 100: 3-5 parts of amphiphilic nano silicon dioxide, 1-2 parts of amphoteric ion surfactant, 0.5-1 part of non-ionic surfactant, and the balance of water; the amphoteric ion surfactant comprises hydroxyl sulfobetaine and imidazoline; and the non-ionic surfactant is an ethoxy-propoxy block copolymer. The self-emulsifying nano composite profile control and displacement agent prepared by the application effectively realizes the balance between low interfacial tension and self-emulsifying efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical oil displacement, and more particularly to a self-emulsifying nano composite profile control and flooding agent for oilfields and a preparation process thereof. BACKGROUND

[0002] Profile control and flooding agent is a key technical means for enhancing oil recovery in oilfields, mainly including polymer flooding, polymer / surfactant binary complex flooding, and polymer / surfactant / alkali ternary complex flooding, etc. Among them, the alkali / surfactant / polymer ternary complex flooding can greatly improve the recovery rate, but the use of alkali can cause formation damage, equipment scaling, and difficulties in produced fluid treatment, etc., and also can reduce the efficiency of polymer and increase the operating cost. The alkali-free binary complex flooding avoids alkali damage, but the core surfactant (such as petroleum sulfonate) has poor salt tolerance, insufficient emulsification stability, and limited adaptability, etc.

[0003] The patent application file with publication number CN110129019A discloses a nano oil displacement agent for tertiary oil recovery, which comprises the following components in parts by weight: oil phase 3-6 parts, cationic and anionic complex surfactant 0.4-1.5 parts or anionic surfactant 1-5 parts, co-surfactant 0.02-0.2 parts, and water 88-98 parts. The oil phase comprises white oil and liquid paraffin in a weight ratio of 1:1, the cationic surfactant is hexadecyl trimethyl ammonium bromide, the anionic surfactant is sodium dodecyl benzene sulfonate, and the co-surfactant is n-butanol.

[0004] In this technical solution, the oil phase adopts white oil and liquid paraffin in a weight ratio of 1:1, which has the defects of poor synergy with surfactants, insufficient emulsification stability, and weak salt resistance; meanwhile, the core component cationic and anionic complex surfactant or anionic surfactant is prone to molecular chain rupture and decomposition failure at high temperature, and is prone to precipitation and separation in high salinity (especially high valence ions such as Ca 2+ , Mg 2+ ) and formation water, resulting in poor interfacial tension stability and difficulty in adapting to the mining needs of high-salt oil reservoirs. SUMMARY

[0005] To solve the above technical problems, the present application provides a self-emulsifying nano composite profile control and flooding agent for oilfields and a preparation process thereof.

[0006] In a first aspect, the present application provides a self-emulsifying nano composite profile control and flooding agent for oilfields, which adopts the following technical solution:

[0007] A self-emulsifying nano composite profile control and flooding agent for oilfields is prepared from the following 100 parts by mass of raw materials:

[0008] The mixture consists of 3-5 parts amphiphilic nano-silica, 1-2 parts amphoteric surfactant, 0.5-1 part nonionic surfactant, and the remainder is water.

[0009] The zwitterionic surfactants include hydroxysulfobetaines and imidazolines;

[0010] The nonionic surfactant is an ethoxy-propoxy block copolymer.

[0011] In this technical solution, amphiphilic nano-silica serves as the core emulsion stabilizer. It forms a dense solid interfacial film through self-assembly at the oil-water interface, effectively preventing droplet collision and aggregation through steric hindrance, thus providing physical stability to the emulsion. The zwitterionic surfactant, with its internal salt structure, forms stable hydrogen bonds with water molecules through strong hydrophilic groups in high-salt environments, preventing precipitation caused by salt ion competition for hydration. Simultaneously, its molecules are directionally adsorbed at the oil-water interface, significantly reducing interfacial tension and providing a foundation for crude oil self-emulsification. The ethoxy-propoxy block copolymer forms a steric hindrance layer based on its amphiphilic block structure, and its high cloud point ensures it does not fail at high temperatures, further enhancing emulsion stability. Through intermolecular synergy, these three components construct a stable oil-water interface system with low interfacial tension, strong steric hindrance, and salt resistance, achieving efficient crude oil self-emulsification and long-term stable regulation.

[0012] Preferably, the method for preparing the amphiphilic nano-silica includes the following steps:

[0013] A dispersion of nano-silica and an alcohol solution of long-chain alkylsilane were injected into the first reaction zone of the microchannel at a flow rate ratio of 1:(3~5). At the same time, an anhydrous ethanol solution of aminosilane was added, and the pH was adjusted to 9.5~10. The temperature was raised to 60~70℃, and the reaction was carried out for 40~50 min. The reaction solution was then transferred to the second reaction zone, and an anhydrous ethanol solution of acid anhydride silane and 4-(dimethylamino)pyridine was added. The pH was maintained at 9.5~10, and the temperature was raised to 70~80℃. The reaction was carried out for 40~50 min, and the solid and liquid were separated. The solution was washed and dried to obtain amphiphilic nano-silica.

[0014] Preferably, the molar ratio of the nano-silica, long-chain alkylsilane, aminosilane and acid anhydride silane is 1:(0.15~0.25):(0.15~0.25):(0.23~0.38).

[0015] In this technical solution, hydrophobic alkyl chains and reactive amino functional groups are simultaneously introduced onto the surface of nanoparticles through the synergistic effect of long-chain alkylsilanes and aminosilanes. Subsequently, the added anhydride silane achieves effective grafting due to its dual reactivity: on the one hand, its highly reactive anhydride groups undergo ring-opening amidation reactions with the surface amino groups to generate amide bonds and release carboxyl groups in situ; at the same time, the alkoxy groups of the anhydride silane hydrolyze to silanols, which condense with the hydroxyl groups on the silica surface to achieve firm molecular anchoring and enhance the hydrophilic sites.

[0016] Preferably, the amount of 4-(dimethylamino)pyridine used is 1% to 2% of the mass of the acid anhydride silane.

[0017] Preferably, the long-chain alkylsilane is selected from either hexadecyltriethoxysilane or octadecyltrimethoxysilane.

[0018] Preferably, the aminosilane is selected from either 3-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

[0019] Preferably, the acid anhydride silane is 3-(triethoxysilyl)propylsuccinic anhydride.

[0020] Preferably, the hydroxysulfonate betaine is selected from any one of octadecyl hydroxysulfonate betaine, hexadecylpropyl hydroxysulfonate betaine, dodecyl hydroxysulfonate betaine, and cocamidopropyl hydroxysulfonate betaine.

[0021] Preferably, the imidazoline is selected from either cocoyl hydroxyethyl imidazoline or lauryl hydroxyethyl imidazoline.

[0022] In this technical solution, under high mineralization, hydroxyl groups in hydroxysulfobetaines form strong hydrogen bonds with water molecules, preventing Na+ from being absorbed into the water. + Ca 2+ Precipitation caused by competitive hydration; imidazoline derivatives, relying on the rigid structure of five-membered heterocyclic rings, not only improve temperature resistance but also achieve corrosion inhibition by forming a metal coordination film through heterocyclic nitrogen atoms. Simultaneously, they shield against calcium and magnesium interference, disrupt the high-colloidal crude oil interface film, and form an interlocking interfacial film with betaine, improving shear resistance. The combination of these two agents compensates for the deficiencies of single surfactants, ensuring efficient tension reduction and stable emulsification of the reflood control agent, making it suitable for complex reservoirs and providing long-term effectiveness.

[0023] Preferably, the ethoxy-propoxy block copolymer is selected from at least one of polyether 2010, polyether 2040, and polyether 2080.

[0024] In this technical solution, by adjusting the ethoxy / propoxy ratio, the hydrophilic-lipophilic balance value can be precisely controlled to match the viscosity of crude oil; its high turbidity point ensures that it does not precipitate in high-temperature reservoirs, and the block structure forms a steric hindrance layer on the surface of the emulsion droplets, which works synergistically with the adsorption film of the zwitterionic surfactant to prolong the stability period of the emulsion.

[0025] Preferably, the self-emulsifying nanocomposite modulator further includes 0.1 to 0.15 parts by weight of propylene glycol ethers.

[0026] Preferably, the propylene glycol ether is selected from either propylene glycol phenyl ether or dipropylene glycol butyl ether.

[0027] In this technical solution, propylene glycol ethers, by virtue of having both polar groups and weak hydrophobic chains, can be more deeply embedded in the composite interface layer formed by amphiphilic nano-silica and ethoxy-propoxy block copolymers. Without compromising its mechanical strength, it balances rigidity and flexibility, thereby obtaining a more stable ultra-low interfacial tension under high temperature and high salt conditions.

[0028] Preferably, the self-emulsifying nanocomposite modulator further includes 0.3 to 0.6 parts by weight of polymer microspheres.

[0029] Preferably, the method for preparing the polymer microspheres includes the following steps:

[0030] S11: Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone are added to deionized water in a molar ratio of (5~7):(2.5~3.5):(0.5~1.5), and 1%~2% of nano-montmorillonite and 0.3%~0.5% of disodium ethylenediaminetetraacetate are added and mixed evenly to obtain an aqueous phase;

[0031] S12: Mix white oil and emulsifier at a volume ratio of (3~5):1 to obtain an oil phase;

[0032] S13: Under an inert atmosphere, the aqueous phase is slowly added to the oil phase and mixed evenly. Then, an oxidation-reduction initiator is added, the temperature is raised to 50-60℃, and the reaction is carried out for 6-8 hours. After solid-liquid separation, the mixture is washed and dried to obtain polymer microspheres.

[0033] The volume ratio of the aqueous phase to the oil phase is 1:(4~6).

[0034] In this technical solution, the sulfonyl and pyrrolidone rings in the molecular chain are strong hydrophilic groups. After being injected into the formation, they absorb formation water and swell, which can effectively block high-permeability channels. The addition of nano-montmorillonite not only enhances the mechanical strength of the microspheres, but also improves their adsorption to the rock surface and prolongs the effective period of the blockage. At the same time, the microspheres can migrate in the formation with water drive to achieve deep profile adjustment and improve the water drive sweep efficiency.

[0035] Preferably, the redox initiator is selected from either ammonium persulfate-sodium bisulfite or potassium persulfate-sodium thiosulfate.

[0036] Preferably, the amount of the redox initiator is 1% to 1.5% of the total mass of the monomer.

[0037] Preferably, the self-emulsifying nanocomposite modulator further includes 0.5 to 1 part by weight of a metal coordination polymer.

[0038] Preferably, the preparation method of the metal coordination polymer includes the following steps:

[0039] Partially hydrolyzed polyacrylamide was added to water and mixed evenly. Zirconium oxychloride octahydrate was added, and the temperature was raised to 50-60℃. The reaction was carried out for 4-6 hours. 3-5 times the volume of anhydrous ethanol was added to the reaction solution, mixed, allowed to stand, and the solid and liquid were separated. The solution was washed and dried to obtain the metal coordination polymer.

[0040] Preferably, the degree of hydrolysis of the partially hydrolyzed polyacrylamide is 25% to 30%.

[0041] Preferably, the mass ratio of zirconium oxychloride octahydrate to partially hydrolyzed polyacrylamide is 1:(20~30).

[0042] In this technical solution, Zr 4+ It forms dynamic metal coordination bonds with the carboxyl groups on the partially hydrolyzed polyacrylamide chain. These bonds are temporarily broken by shearing during injection. After entering the formation, the coordination bonds recombine to form a cross-linked network, which increases the viscosity.

[0043] Secondly, this application provides a preparation process for a self-emulsifying nanocomposite modulator for oil fields, comprising the following steps:

[0044] Amphoteric and nonionic surfactants were added to deionized water and mixed evenly. Amphiphilic nano-silica was then added and mixed evenly. The mixture was heated to 40-50°C and kept at that temperature for 24-48 hours. After cooling, the emulsified nanocomposite modulator was obtained.

[0045] In this technical solution, amphiphilic nano-silica first forms a solid interface film, and then surfactant molecules are directionally adsorbed onto the film surface, constructing a dual barrier of solid film and surfactant adsorption film. At the same time, the low temperature of 40~50℃ can promote the directional adsorption of surfactant and the dispersion of the system, avoid the agglomeration caused by slow dispersion of nanoparticles or insufficient adsorption of surfactant at low temperature, and ensure the emulsification efficiency of the self-emulsifying nanocomposite modulator.

[0046] Preferably, after adding amphiphilic nano-silica, the step of adding polymer microspheres is also included.

[0047] Preferably, after adding amphiphilic nano-silica, the step of adding a metal coordination polymer is also included.

[0048] In summary, this application has the following beneficial effects:

[0049] 1. This application uses amphiphilic nano-silica, zwitterionic surfactant, and nonionic surfactant as the core components to synergistically construct a stable system: amphiphilic nano-silica self-assembles at the oil-water interface to form a solid interfacial film, preventing emulsion droplet aggregation; zwitterionic surfactant relies on its internal salt structure to resist salting out, while directional adsorption reduces interfacial tension; nonionic surfactant provides steric hindrance through its block structure, and its high cloud point enhances temperature resistance, thereby strengthening the stability of the modulator in high salinity environments and improving the self-emulsification efficiency of crude oil.

[0050] 2. In the preparation of amphiphilic nano-silica, this application constructs an amphiphilic structure on the surface of nanoparticles through the synergistic grafting of long-chain alkylsilanes, aminosilanes, and acid anhydride silanes; the carboxyl groups generated after the hydrolysis of acid anhydride silanes form intramolecular crosslinks with the amino groups remaining on the surface, which strengthens the bonding strength of the modified layer; thereby effectively inhibiting particle agglomeration in high-salt environments, significantly improving the dispersion stability of the modulator, and avoiding the risk of formation blockage during injection. Attached Figure Description

[0051] Figure 1 This is an optical micrograph of the emulsion formed by emulsifying the self-emulsifying nanocomposite modulator and crude oil in Example 1.

[0052] Figure 2 This is an optical micrograph of the emulsion formed by emulsifying the self-emulsifying nanocomposite modulator with crude oil in Comparative Example 3. Detailed Implementation

[0053] The present application will be further described in detail below with reference to the embodiments.

[0054] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0055] Nano-silica has a particle size distribution of 10~40nm and a specific surface area of ​​280~300m². 2 / g, purity 99.5%;

[0056] The mass fraction of the ethanol aqueous solution is 75%.

[0057] Preparation Examples 1-3: Amphiphilic Nano-Silica

[0058] Preparation Example 1

[0059] The preparation method of the amphiphilic nano-silica in this example includes the following steps:

[0060] S1: Add 0.2 mol of nano-silica to 100 g of ethanol aqueous solution, and sonicate for 15 min at 300 W and 20 kHz to obtain a dispersion.

[0061] S2: Add 0.04 mol of hexadecyltriethoxysilane to 150 g of ethanol aqueous solution and stir at 200 rpm for 15 min to obtain solution A;

[0062] S3: Add 0.04 mol of 3-aminopropyltriethoxysilane to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution B;

[0063] S4: Add 0.06 mol of 3-(triethoxysilyl)propylsuccinic anhydride and 0.27 g of 4-(dimethylamino)pyridine to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution C;

[0064] S5: The dispersion and solution A were simultaneously pumped into the first reaction zone of the microchannel reactor at a flow rate ratio of 1:4. At the same time, solution B was pumped in, and the pH was dynamically adjusted to 9.5 using 5% ammonia water. The temperature was raised to 65℃, and after reacting for 40 min, the reaction solution was transferred to the second reaction zone, and solution C was pumped in. The pH was adjusted to 9.5 using 5% ammonia water, and the temperature was raised to 75℃. After reacting for 40 min, the mixture was centrifuged, washed three times with deionized water and once with anhydrous ethanol, and dried at 80℃ to constant weight to obtain amphiphilic nano-silica.

[0065] Preparation Example 2

[0066] The preparation method of the amphiphilic nano-silica in this example includes the following steps:

[0067] S1: Add 0.2 mol of nano-silica to 100 g of ethanol aqueous solution, and sonicate for 15 min at 300 W and 20 kHz to obtain a dispersion.

[0068] S2: Add 0.03 mol of hexadecyltriethoxysilane to 150 g of ethanol aqueous solution and stir at 200 rpm for 15 min to obtain solution A;

[0069] S3: Add 0.03 mol of 3-aminopropyltriethoxysilane to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution B;

[0070] S4: Add 0.045 mol of 3-(triethoxysilyl)propylsuccinic anhydride and 0.27 g of 4-(dimethylamino)pyridine to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution C;

[0071] S5: The dispersion and solution A were simultaneously pumped into the first reaction zone of the microchannel reactor at a flow rate ratio of 1:3. At the same time, solution B was pumped in, and the pH was dynamically adjusted to 9.5 using 5% ammonia water. The temperature was raised to 60℃, and after reacting for 50 min, the reaction solution was transferred to the second reaction zone, and solution C was pumped in. The pH was adjusted to 9.5 using 5% ammonia water, and the temperature was raised to 70℃. After reacting for 50 min, the mixture was centrifuged, washed three times with deionized water and once with anhydrous ethanol, and dried at 80℃ to constant weight to obtain amphiphilic nano-silica.

[0072] Preparation Example 3

[0073] The preparation method of the amphiphilic nano-silica in this example includes the following steps:

[0074] S1: Add 0.2 mol of nano-silica to 100 g of ethanol aqueous solution, and sonicate for 15 min at 300 W and 20 kHz to obtain a dispersion.

[0075] S2: Add 0.05 mol of hexadecyltriethoxysilane to 150 g of ethanol aqueous solution and stir at 200 rpm for 15 min to obtain solution A;

[0076] S3: Add 0.05 mol of 3-aminopropyltriethoxysilane to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution B;

[0077] S4: Add 0.075 mol of 3-(triethoxysilyl)propylsuccinic anhydride and 0.23 g of 4-(dimethylamino)pyridine to 150 g of anhydrous ethanol and stir at 200 rpm for 15 min to obtain solution C;

[0078] S5: The dispersion and solution A are simultaneously pumped into the first reaction zone of the microchannel reactor at a flow rate ratio of 1:5. At the same time, solution B is pumped in, and the pH is dynamically adjusted to 10 using 5% ammonia water. The temperature is raised to 70℃, and after reacting for 45 min, the reaction solution is transferred to the second reaction zone, and solution C is pumped in. The pH is adjusted to 10 using 5% ammonia water, and the temperature is raised to 80℃. After reacting for 45 min, the mixture is centrifuged, washed three times with deionized water and once with anhydrous ethanol, and dried at 80℃ to constant weight to obtain amphiphilic nano-silica.

[0079] Preparation Examples 4-6 Polymer Microspheres

[0080] Preparation Example 4

[0081] The preparation method of the polymer microspheres in this example includes the following steps:

[0082] S11: Add 0.03 mol of acrylamide, 0.015 mol of 2-acrylamide-2-methylpropanesulfonic acid and 0.005 mol of N-vinylpyrrolidone to 30 g of deionized water, add 0.06 g of nano-montmorillonite and 0.018 g of disodium ethylenediaminetetraacetate, stir and mix at 500 rpm for 15 min to obtain the aqueous phase;

[0083] S12: Add white oil and Span 80 to a container at a volume ratio of 4:1, and stir at 500 rpm for 15 minutes to obtain the oil phase;

[0084] S13: Under an inert atmosphere, add an oil phase with a volume of 5 times that of the aqueous phase to the reactor, then slowly add the aqueous phase while stirring at 500 rpm. After the addition is complete, continue stirring for 10 min. Then slowly add an aqueous solution of ammonium persulfate and sodium bisulfite (0.03 g of ammonium persulfate, 0.03 g of sodium bisulfite, and 2 g of deionized water). Stir until uniform, heat to 55 °C, react for 7 h, centrifuge, wash 3 times with deionized water and 1 time with anhydrous ethanol, and dry at 50 °C to constant weight to obtain polymer microspheres.

[0085] The molar mass of acrylamide is 71.08 g / mol; the molar mass of 2-acrylamide-2-methylpropanesulfonic acid is 207.25 g / mol; the molar mass of N-vinylpyrrolidone is 111.14 g / mol; the amount of acrylamide used is 2.13 g, the amount of 2-acrylamide-2-methylpropanesulfonic acid used is 3.11 g, the amount of N-vinylpyrrolidone used is 0.56 g, and the total amount of the three monomers used is 5.8 g.

[0086] Preparation Example 5

[0087] The preparation method of the polymer microspheres in this example includes the following steps:

[0088] S11: Add 0.025 mol of acrylamide, 0.0175 mol of 2-acrylamide-2-methylpropanesulfonic acid and 0.0075 mol of N-vinylpyrrolidone to 30 g of deionized water, add 0.1 g of nano-montmorillonite and 0.03 g of disodium ethylenediaminetetraacetate, and stir at 500 rpm for 15 min to obtain the aqueous phase;

[0089] S12: Add white oil and Span 80 to a container at a volume ratio of 3:1, and stir at 500 rpm for 15 minutes to obtain the oil phase;

[0090] S13: Under an inert atmosphere, add an oil phase with a volume of 4 times that of the aqueous phase to the reactor, then slowly add the aqueous phase while stirring at 500 rpm. After the addition is complete, continue stirring for 10 min. Then slowly add an aqueous solution of ammonium persulfate and sodium bisulfite (0.05 g of ammonium persulfate, 0.04 g of sodium bisulfite, and 2 g of deionized water). Stir until uniform, heat to 50 °C, react for 8 h, centrifuge, wash 3 times with deionized water and 1 time with anhydrous ethanol, and dry at 50 °C to constant weight to obtain polymer microspheres.

[0091] The molar mass of acrylamide is 71.08 g / mol; the molar mass of 2-acrylamide-2-methylpropanesulfonic acid is 207.25 g / mol; the molar mass of N-vinylpyrrolidone is 111.14 g / mol; the amount of acrylamide used is 1.78 g, the amount of 2-acrylamide-2-methylpropanesulfonic acid used is 3.63 g, the amount of N-vinylpyrrolidone used is 0.83 g, and the total amount of the three monomers used is 6.24 g.

[0092] Preparation Example 6

[0093] The preparation method of the polymer microspheres in this example includes the following steps:

[0094] S11: Add 0.035 mol of acrylamide, 0.0125 mol of 2-acrylamide-2-methylpropanesulfonic acid and 0.0025 mol of N-vinylpyrrolidone to 30 g of deionized water, add 0.11 g of nano-montmorillonite and 0.02 g of disodium ethylenediaminetetraacetate, and stir at 500 rpm for 15 min to obtain the aqueous phase;

[0095] S12: Add white oil and Span 80 to a container at a volume ratio of 5:1, and stir at 500 rpm for 15 minutes to obtain the oil phase;

[0096] S13: Under an inert atmosphere, add an oil phase with a volume of 6 times that of the aqueous phase to the reactor, then slowly add the aqueous phase while stirring at 500 rpm. After the addition is complete, continue stirring for 10 min. Then slowly add an aqueous solution of ammonium persulfate and sodium bisulfite (0.03 g of ammonium persulfate, 0.02 g of sodium bisulfite, and 2 g of deionized water). Stir until uniform, heat to 60 °C, react for 6 h, centrifuge, wash 3 times with deionized water and 1 time with anhydrous ethanol, and dry at 50 °C to constant weight to obtain polymer microspheres.

[0097] The molar mass of acrylamide is 71.08 g / mol; the molar mass of 2-acrylamide-2-methylpropanesulfonic acid is 207.25 g / mol; the molar mass of N-vinylpyrrolidone is 111.14 g / mol; the amount of acrylamide is 2.49 g, the amount of 2-acrylamide-2-methylpropanesulfonic acid is 2.59 g, the amount of N-vinylpyrrolidone is 0.28 g, and the total amount of the three monomers is 5.36 g.

[0098] Preparation Examples 7-9: Metal Coordination Polymers

[0099] Preparation Example 7

[0100] The preparation method of the metal coordination polymer in this example includes the following steps:

[0101] 5g of partially hydrolyzed polyacrylamide with a degree of hydrolysis of 25% was added to 25g of deionized water and stirred at 300rpm for 60min. Zirconium oxychloride aqueous solution (0.2g zirconium oxychloride octahydrate and 4.8g deionized water) was added, and the mixture was heated to 55℃ and reacted for 5h. Then, 4 times the volume of anhydrous ethanol was added to the reaction solution, stirred and mixed for 60min, allowed to stand for 60min, centrifuged, and the solid product was collected. The product was washed three times with 50% ethanol aqueous solution and dried at 60℃ to constant weight to obtain the metal coordination polymer.

[0102] Preparation Example 8

[0103] 4g of partially hydrolyzed polyacrylamide with a degree of hydrolysis of 30% was added to 25g of deionized water and stirred at 300rpm for 60min. Zirconium oxychloride aqueous solution (0.2g zirconium oxychloride octahydrate and 4.8g deionized water) was added, and the mixture was heated to 50℃ and reacted for 6h. Then, 3 times the volume of anhydrous ethanol was added to the reaction solution, stirred for 60min, allowed to stand for 60min, centrifuged, and the solid product was collected. The product was washed three times with 50% ethanol aqueous solution and dried at 60℃ to constant weight to obtain the metal coordination polymer.

[0104] Preparation Example 9

[0105] 6g of partially hydrolyzed polyacrylamide with a degree of hydrolysis of 30% was added to 25g of deionized water and stirred at 300rpm for 60min. Zirconium oxychloride aqueous solution (0.2g zirconium oxychloride octahydrate and 4.8g deionized water) was added, and the mixture was heated to 60℃ and reacted for 4h. Then, 5 times the volume of anhydrous ethanol was added to the reaction solution, and the mixture was stirred for 60min. The mixture was allowed to stand for 60min, centrifuged, and the solid product was collected. The solid product was washed three times with a 50% ethanol aqueous solution and dried at 60℃ to constant weight to obtain the metal coordination polymer.

[0106] Example 1

[0107] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0108] 1 g of octadecyl hydroxysulfonate betaine, 0.5 g of cocoyl hydroxyethyl imidazoline, and 0.75 g of polyether 2010 were added to 93.75 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano silica was slowly added, and the stirring speed was increased to 1000 rpm. The mixture was stirred for 60 min, heated to 45 °C, and kept at this temperature for 24 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0109] Among them, the amphiphilic nano-silica comes from preparation example 1.

[0110] Example 2

[0111] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0112] 0.7 g of dodecyl hydroxysulfobetaine, 0.3 g of cocoyl hydroxyethyl imidazoline, 1 g of polyether 2010 and 0.15 g of propylene glycol phenyl ether were added to 94.85 g of deionized water and stirred at 300 rpm for 10 min. Then, 3 g of amphiphilic nano silica was slowly added and the stirring speed was increased to 1000 rpm. The mixture was stirred for 50 min, heated to 40 °C and kept at that temperature for 48 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0113] Among them, the amphiphilic nano-silica comes from preparation example 2.

[0114] Example 3

[0115] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0116] 1.2 g of hexadecylpropylhydroxysulfonate betaine, 0.8 g of cocoyl hydroxyethyl imidazoline, 0.5 g of polyether 2040 and 0.1 g of dipropylene glycol butyl ether were added to 92.4 g of deionized water and stirred at 300 rpm for 15 min. Then, 5 g of amphiphilic nano-silica was slowly added and the stirring speed was increased to 1000 rpm. The mixture was stirred for 70 min, heated to 50 °C and kept at that temperature for 36 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0117] Among them, the amphiphilic nano-silica comes from preparation example 3.

[0118] Example 4

[0119] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0120] 1.2 g of cocamidopropyl hydroxysulfonate betaine, 0.8 g of lauryl hydroxyethyl imidazoline, 0.5 g of polyether 2010 and 0.1 g of dipropylene glycol butyl ether were added to 92.1 g of deionized water and stirred at 300 rpm for 15 min. Then, 5 g of amphiphilic nano-silica and 0.3 g of polymer microspheres were slowly added, and the stirring speed was increased to 1000 rpm. The mixture was stirred for 70 min, heated to 50 °C, and kept at this temperature for 36 h with continuous stirring at 150 rpm. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0121] Among them, the amphiphilic nano-silica came from preparation example 2; the polymer microspheres came from preparation example 4.

[0122] Example 5

[0123] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0124] 0.75 g of cocamidopropyl hydroxysulfonate betaine, 0.75 g of lauryl hydroxyethyl imidazoline, 0.75 g of polyether 2040 and 0.12 g of dipropylene glycol butyl ether were added to 93.13 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano-silica and 0.5 g of polymer microspheres were slowly added, and the stirring speed was increased to 1000 rpm. The mixture was stirred for 70 min, heated to 50 °C, and kept at this temperature for 36 h with continuous stirring at 150 rpm. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0125] Among them, the amphiphilic nano-silica came from preparation example 3; the polymer microspheres came from preparation example 5.

[0126] Example 6

[0127] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0128] 0.75 g of octadecyl hydroxysulfonate betaine, 0.75 g of cocoyl hydroxyethyl imidazoline, 0.75 g of polyether 2080 and 0.12 g of dipropylene glycol butyl ether were added to 92.53 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano-silica, 0.6 g of polymer microspheres and 0.5 g of metal coordination polymer were slowly added, and the stirring speed was increased to 1000 rpm and stirred for 70 min. The temperature was raised to 50 °C and kept at 36 h, with continuous stirring at 150 rpm during the process. After the heat preservation was completed, the mixture was naturally cooled to room temperature to obtain the emulsified nanocomposite modulator.

[0129] Among them, amphiphilic nano-silica came from preparation example 3; polymer microspheres came from preparation example 6; and metal coordination polymer came from preparation example 7.

[0130] Example 7

[0131] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0132] 0.75 g of octadecyl hydroxysulfonate betaine, 0.75 g of cocoyl hydroxyethyl imidazoline, 0.75 g of polyether 2080 and 0.12 g of dipropylene glycol butyl ether were added to 92.28 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano-silica, 0.6 g of polymer microspheres and 0.75 g of metal coordination polymer were slowly added, and the stirring speed was increased to 1000 rpm and stirred for 70 min. The temperature was raised to 50 °C and kept at 36 h, with continuous stirring at 150 rpm during the process. After the heat preservation was completed, the mixture was naturally cooled to room temperature to obtain the emulsified nanocomposite modulator.

[0133] Among them, the amphiphilic nano-silica came from preparation example 3; the polymer microspheres came from preparation example 6; and the metal coordination polymer came from preparation example 8.

[0134] Example 8

[0135] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this embodiment includes the following steps:

[0136] 0.75 g of octadecyl hydroxysulfonate betaine, 0.75 g of cocoyl hydroxyethyl imidazoline, 0.75 g of polyether 2080 and 0.12 g of dipropylene glycol butyl ether were added to 92.03 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano-silica, 0.6 g of polymer microspheres and 1 g of metal coordination polymer were slowly added, and the stirring speed was increased to 1000 rpm and stirred for 70 min. The temperature was raised to 50 °C and kept at 36 h, with continuous stirring at 150 rpm during the process. After the heat preservation was completed, the mixture was naturally cooled to room temperature to obtain the emulsified nanocomposite modulator.

[0137] Among them, the amphiphilic nano-silica came from preparation example 3; the polymer microspheres came from preparation example 6; and the metal coordination polymer came from preparation example 9.

[0138] Comparative Example 1

[0139] The preparation method of the self-emulsifying nanocomposite modifier for oilfields in this comparative example includes the following steps:

[0140] 1 g of octadecyl hydroxysulfonate betaine, 0.5 g of cocoyl hydroxyethyl imidazoline, and 0.75 g of polyether 2010 were added to 93.75 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of nano silica was slowly added and the stirring speed was increased to 1000 rpm. The mixture was stirred for 60 min, heated to 45 °C, and kept at this temperature for 24 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0141] Comparative Example 2

[0142] The preparation method of the self-emulsifying nanocomposite modifier for oilfields in this comparative example includes the following steps:

[0143] 1.5 g of octadecyl hydroxysulfonate betaine and 0.75 g of polyether 2010 were added to 93.75 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano silica was slowly added and the stirring speed was increased to 1000 rpm. The mixture was stirred for 60 min, heated to 45 °C, and kept at this temperature for 24 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0144] Among them, the amphiphilic nano-silica comes from preparation example 1.

[0145] Comparative Example 3

[0146] The preparation method of the self-emulsifying nanocomposite modulator for oilfields in this comparative example includes the following steps:

[0147] 1 g of octadecyl hydroxysulfonate betaine and 0.5 g of cocoyl hydroxyethyl imidazoline were added to 94.5 g of deionized water and stirred at 300 rpm for 15 min. Then, 4 g of amphiphilic nano silica was slowly added and the stirring speed was increased to 1000 rpm. The mixture was stirred for 60 min, heated to 45 °C, and kept at this temperature for 24 h, with continuous stirring at 150 rpm during the process. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature to obtain the emulsified nanocomposite modulator.

[0148] Among them, the amphiphilic nano-silica comes from preparation example 1.

[0149] Performance testing

[0150] 1. Interfacial tension

[0151] The self-emulsifying nanocomposite modulator and crude oil were preheated in a 45℃ constant temperature drying oven for 30 min. A 50 mL beaker was taken and 30 mL of the preheated modulator was added. The beaker was placed on the constant temperature sample stage (45℃) of the interfacial tensiometer. After the temperature stabilized, the preheated crude oil was drawn up with a 10 μL syringe. The syringe needle was inserted 1 cm below the surface of the modulator liquid and the crude oil was slowly pushed out to form a droplet. After the droplet stabilized for 10 min, the dynamic interfacial tension between oil and water was measured and recorded until equilibrium was reached. The lowest interfacial tension value was recorded. See Table 1 for details.

[0152] 2. Self-emulsifying effect

[0153] Add the self-emulsifying nanocomposite modulator and crude oil to a glass tube at a volume ratio of 1:1. Gently invert the glass tube three times, then place it in a 45°C constant temperature water bath and start timing. Record the time from mixing to the system completely becoming an emulsion and the time of standing and stratification, as shown in Table 1.

[0154] One drop of the emulsion from Example 1 and Comparative Example 3 was placed on a glass slide, and the droplet size was observed under an optical microscope. See details below. Figure 1 and Figure 2 .

[0155] 3. Dispersion stability

[0156] Pour 50 mL of the self-emulsifying nanocomposite modulator into a pre-weighed glass tube, place it in a 45℃ constant temperature water bath, and let it stand at a constant temperature for 72 h. After standing, use a pipette to take 5 mL of liquid from the bottom of the graduated cylinder and put it into a pre-weighed centrifuge tube, which is recorded as m1. Place the centrifuge tube in a centrifuge and centrifuge at 4000 rpm for 30 min. Discard the supernatant and place the centrifuge tube in an 80℃ drying oven to dry to constant weight. Weigh it and record the weight as m2. Calculate the sedimentation rate, as shown in Table 1.

[0157] 4. Stratigraphic compatibility

[0158] The self-emulsifying nanocomposite modulator was mixed with formation water from Changqing Oilfield (mineralization of 60.1 g / L, main ion being Na+). + Ca 2+ Mg 2+ Cl - SO4 2- Mixtures were prepared at volume ratios of 1:9 and 3:7, with each mixture having a total volume of approximately 20 mL. The mixtures were gently inverted and shaken 10 times, and then placed in constant temperature ovens at 45℃, 60℃, and 80℃ respectively, and allowed to stand for 14 days. During this period, it was observed whether stratification, precipitation, or flocculation occurred. See Table 2 for details.

[0159] 5. Evaluation of Oil Recovery Efficiency

[0160] Core displacement experiments were conducted using a sand-filled tube model. All experiments were carried out at 45℃ to simulate the reservoir environment. The specific procedure was as follows: first, water flooding was performed (injecting formation water from Changqing Oilfield at a flow rate of 0.5 mL / min) until the water cut at the outlet reached 98%, and the water flooding recovery rate was recorded; then, a self-emulsifying nanocomposite modulator was injected, and water flooding continued until the water cut reached 98%, and the total recovery rate after modulator was recorded; see Table 2 for details.

[0161] Table 1. Performance testing of self-emulsifying nanocomposite modulators in Examples 1-8 and Comparative Examples 1-3

[0162]

[0163] Table 2. Oil recovery performance testing of self-emulsifying nanocomposite modulators in Examples 1-8 and Comparative Examples 1-3.

[0164]

[0165] Based on Tables 1-2, analysis of Examples 1-8 and Comparative Examples 1-3 reveals that:

[0166] The self-emulsifying nanocomposite modulators prepared in Examples 1-8, based on the amphiphilic structure of amphiphilic nano-silica and the salt resistance of the composite surfactant, not only effectively resist the interference of high mineralization and ensure excellent formation compatibility (no stratification, no flocculation, no precipitation), but also simultaneously achieve low interfacial tension and rapid emulsification, ensuring that crude oil is effectively stripped away and forming a large number of tiny oil droplets, which significantly improves the recovery rate.

[0167] The introduction of polymer microspheres in Examples 4-5 and the further introduction of metal coordination polymers in Examples 6-8 not only participate in the emulsification process, but also effectively regulate the flow direction of the displacement fluid and expand the swept volume through physical blocking. Thus, on the basis of efficient oil washing, the oil displacement efficiency is further improved, and the recovery rate is improved stepwise.

[0168] In Comparative Examples 1-3, both the nanomaterials providing the amphiphilic structure and the surfactants with specific functions led to the disruption of the synergistic effect, resulting in a comprehensive decline in interfacial activity, emulsification efficiency and stability, and ultimately manifested as a decrease in recovery rate.

[0169] Combination Figure 1 and Figure 2 Analysis shows that although Comparative Example 3, through the synergistic effect of amphiphilic nano-silica and ionic surfactants, formed a robust emulsion with uniform oil droplet size and good dispersion, the number of oil droplets was relatively small, indicating limited emulsification efficiency and displacement capacity, resulting in a relatively low recovery rate. Optical microscopic images of Example 1 show that the oil droplets exhibit high density, high uniformity, and high dispersion. This fully demonstrates that the amphiphilic nano-silica and the two types of surfactants together form a more dense and stable composite interfacial film, which not only significantly improves emulsification efficiency and displaces more oil droplets, but also "locks" these high-density oil droplets in a uniform and dispersed state. This microscopically high-density, uniformly dispersed droplet morphology directly corresponds to its efficient stripping and carrying capacity for crude oil, resulting in a relatively high recovery rate.

[0170] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A self-emulsifying nanocomposite modifier for oilfields, characterized in that, It is prepared from the following 100 parts by weight of raw materials: The mixture consists of 3-5 parts amphiphilic nano-silica, 1-2 parts amphoteric surfactant, 0.5-1 part nonionic surfactant, and the remainder is water. The zwitterionic surfactants include hydroxysulfobetaines and imidazolines; The nonionic surfactant is an ethoxy-propoxy block copolymer; The preparation method of the amphiphilic nano-silica includes the following steps: A dispersion of nano-silica and an alcohol solution of long-chain alkylsilane were injected into the first reaction zone of the microchannel at a flow rate ratio of 1:(3~5). At the same time, an anhydrous ethanol solution of aminosilane was added, the pH was adjusted to 9.5~10, the temperature was raised to 60~70℃, and the reaction was carried out for 40~50 min. The reaction solution was then transferred to the second reaction zone, where an anhydrous ethanol solution of acid anhydride silane and 4-(dimethylamino)pyridine was added. The pH was maintained at 9.5~10, the temperature was raised to 70~80℃, and the reaction was carried out for 40~50 min. The solid and liquid were separated, washed, and dried to obtain amphiphilic nano-silica. The hydroxysulfonate betaines are selected from any one of octadecyl hydroxysulfonate betaine, hexadecylpropyl hydroxysulfonate betaine, dodecyl hydroxysulfonate betaine, and cocamidopropyl hydroxysulfonate betaine. The imidazoline is selected from either cocoyl hydroxyethyl imidazoline or lauryl hydroxyethyl imidazoline; The ethoxy-propoxy block copolymer is selected from at least one of polyether 2010, polyether 2040, and polyether 2080.

2. The self-emulsifying nanocomposite modifier for oilfields according to claim 1, characterized in that, The long-chain alkylsilane is selected from either hexadecyltriethoxysilane or octadecyltrimethoxysilane.

3. The self-emulsifying nanocomposite modifier for oilfields according to claim 1, characterized in that, The aminosilane is selected from either 3-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

4. The self-emulsifying nanocomposite modifier for oilfields according to claim 1, characterized in that, The acid anhydride silane is 3-(triethoxysilyl)propylsuccinic anhydride.

5. The self-emulsifying nanocomposite modifier for oilfields according to claim 1, characterized in that, The self-emulsifying nanocomposite modulator also includes 0.1 to 0.15 parts by weight of propylene glycol ethers.

6. A preparation process for a self-emulsifying nanocomposite modifier for oilfields as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Amphoteric and nonionic surfactants were added to deionized water and mixed evenly. Amphiphilic nano-silica was then added and mixed evenly. The mixture was heated to 40-50°C and kept at that temperature for 24-48 hours. After cooling, the emulsified nanocomposite modulator was obtained.

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