An emulsifying acid nanoemulsifier, its preparation method and application

Abstract

This invention relates to the field of oil and gas reservoir acidification technology, specifically providing an emulsified acid nanoemulsifier, its preparation method, and its application. It is prepared by mixing modified nanoparticles, betaine surfactant, nonionic surfactant, cationic surfactant, ethanol, and synthetic ester in a mass ratio of 10–25:10–15:10–20:20–30:10–20:20–40, and then fully dispersing the mixture using a homogenizer at a stirring speed of 20,000–30,000 rpm. The nano-silica is grafted with sterically hindered groups, allowing it to adsorb at the oil-water interface under strong acid and strong ionic conditions, effectively inhibiting droplet aggregation and improving the stability of the emulsion under high temperature, high salt, and strong acid environments. This invention is used for the preparation of high-temperature emulsified acids. The resulting emulsified acid with an internal phase content of 70%–80% can remain stable for more than 2 hours at 180°C, exhibiting excellent slowing effect and a high final dissolution rate. It avoids the use of macromolecular polymers to stabilize the emulsion, effectively preventing residue damage to the reservoir.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas reservoir acidification technology, specifically relating to an emulsified acid nanoemulsifier, its preparation method, and its application. Background Technology

[0002] Carbonate reservoirs are among the most common types of oil reservoirs in my country, characterized by large reserves, wide distribution, and high exploration difficulty. Therefore, in-depth research into the development technology and enhanced oil recovery of carbonate reservoirs is a crucial issue in contemporary oil and gas resource development. For the characteristics of carbonate reservoirs, acid fracturing technology is generally employed. This involves pumping acid to open fractures in the reservoir, and then using the acid-rock reaction to prevent non-uniform etching within the fractures, leaving non-uniform etched channels for oil and gas flow after the fractures close. However, carbonate reservoirs are buried at great depths and have high formation temperatures. Conventional acid systems often fail due to the rapid acid-rock reaction, being exhausted near the wellbore. Therefore, the acid system used in carbonate fracturing needs to have a certain rate-retarding effect in high-temperature environments to achieve deep acid penetration and increase the acid's effective range.

[0003] Currently, commonly used slow-reaction acid systems include gelling acid, cross-linked acid, autogenous acid, and emulsified acid. Among these, gelling acid and cross-linked acid are more widely used. They primarily work by thickening the acid solution, increasing its apparent viscosity, and reducing the mass transfer rate of hydrogen ions from the acid solution to the rock face, thus effectively slowing down the acid-rock reaction rate. However, in high-temperature reservoir environments, gelling acid or cross-linked acid systems often use large amounts of high-molecular-weight thickeners or polymer thickeners with large molecular weights. Under high temperatures, these thickeners can easily react with acids and metal ions to form insoluble substances, blocking oil and gas channels and causing damage. Autogenous acid systems rely on a chemical reaction at high temperatures to produce HCl, which etches the rock surface. However, the amount of acid produced is insufficient or difficult to control, thus limiting their widespread application. Emulsified acid, on the other hand, uses an oil phase to encapsulate the acid, forming an oil-external phase emulsion. This emulsion carries the acid deep into fractures, where it breaks down under high temperature or strong ionic conditions, gradually releasing the acid to etch the rock face. Emulsified acid not only has good slow-reaction properties but also provides more effective protection for the tubing string. However, emulsified acids formulated with conventional surfactant emulsifiers often have poor stability and break down quickly at high temperatures, making it difficult for the acid to penetrate deeply. To improve the stability of emulsified acids and achieve deep acidification, researchers add polymer thickeners to enhance the stability of the emulsion, but this still carries the risk of residue damage. Summary of the Invention

[0004] The purpose of this invention is to provide an emulsified acid nanoemulsifier, its preparation method, and its application. This emulsified acid solution used for acid fracturing of carbonate rocks is stabilized under high-temperature conditions, slows down the acid-rock reaction rate, and enables deep penetration of the acid solution. At the same time, it avoids the residue damage caused by polymer thickeners and gels as acid solution stabilizers.

[0005] To solve the above-mentioned technical problems, the present invention provides an emulsified acid nanoemulsifier, which is prepared by mixing modified nanoparticles, betaine surfactant, nonionic surfactant, cationic surfactant, ethanol, and synthetic ester in a mass ratio of 10-25:10-15:10-20:20-30:10-20:20-40, and then fully dispersing the mixture using a homogenizer at a stirring speed of 20,000-30,000 rpm.

[0006] Furthermore, the modified nanoparticles are prepared by grafting nano-silica with alkyl (aromatic) amide silane coupling agent and betaine silane coupling agent.

[0007] Furthermore, the alkyl (aromatic) amide silane coupling agent is prepared by dissolving alkyl (aromatic) acyl chloride and amino silane coupling agent in an organic solvent at a molar ratio of 1-2:1-3, with a reactant mass concentration of 10wt%-50wt%, a reaction temperature of 5-35℃, a reaction time of 2-5h, and removing the solvent by vacuum distillation after the reaction is completed.

[0008] Furthermore, the alkyl (aromatic) acyl chloride is any one of the alkyl or aromatic acyl chloride molecules with 5 to 14 carbon atoms among phenylacetyl chloride, n-valeryl chloride, isovaleryl chloride, n-hexanoyl chloride, isohexanoyl chloride, n-octanoyl chloride, isooctanoyl chloride, n-decanoyl chloride, isodecanyl chloride, cyclopentylformyl chloride, and cyclohexylformyl chloride;

[0009] The aminosilane coupling agent is any one of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, or 2-[(trimethoxysilyl)methyl]butane-1,4-diamine containing one or more primary or secondary amine structures;

[0010] The organic solvent is any one of the non-hydroxyl organic solvents among dichloromethane, tetrahydrofuran, toluene, and acetone.

[0011] Furthermore, the betaine silane coupling agent is prepared by reacting 1,3-propyl sulfonyl lactone with a tertiary amino silane coupling agent.

[0012] Furthermore, the betaine silane coupling agent is prepared by dissolving 1,3-propyl sulfonyl lactone and tertiary amino silane coupling agent in an organic solvent at a molar ratio of 1 to 1.3:1, with a reactant concentration of 5 wt% to 50 wt%, a reaction temperature of 30 to 60°C, and a reaction time of 2 to 5 h.

[0013] The organic solvent is any solvent that does not dissolve betaine salts, such as acetone or dichloromethane.

[0014] The tertiary amine silane coupling agent is any one of (N,N-dimethyl-3-aminopropyl)trimethoxysilane or N,N-diethyl-3-aminopropyltrimethoxysilane containing a tertiary amine structure.

[0015] Furthermore, the method for grafting and modifying nano-silica is as follows: alkyl (aromatic) amide silane coupling agent, betaine silane coupling agent and nano-silica are dispersed in an organic solvent at a mass ratio of 1-3:2-5:3-7, and the mixture is fully dispersed using a homogenizer. The stirring speed is 15000-30000 rpm, the reaction temperature is 40-60℃, and the reaction time is 5-6 h.

[0016] Furthermore, the synthetic ester is any one of ethyl acetate, butyl acetate, or isooctyl acetate with a melting point below 0°C.

[0017] This invention also provides an application of an emulsified acid nanoemulsifier. 2-7 parts of the above-mentioned nanoemulsifier are fully dispersed in 25-30 parts of an oil phase, and the oil phase is continuously stirred at a mechanical stirring speed of 2000 rpm to 5000 rpm. 63-73 parts of the prepared acid solution are dripped into the oil phase at a rate of 2-5 parts / min to ensure that the oil phase is always the dominant phase, thus obtaining an oil-in-acid system with an internal phase content of 63%-73%.

[0018] Furthermore, the acid solution is any one of conventional hydrochloric acid, terrine acid, organic acid, or autogenous acid; the oil phase is any one of diesel, white oil, or crude oil hydrocarbon fluids with a pour point below 0°C.

[0019] The present invention also provides an application of an emulsified acid nanoemulsifier. 2-7 parts of the above-mentioned nanoemulsifier are fully dispersed in 25-30 parts of an oil phase, and the oil phase is continuously stirred at a mechanical stirring speed of 2000 rpm to 5000 rpm. 63-73 parts of the prepared acid solution are dripped into the oil phase at a rate of 2-5 parts / min to ensure that the oil phase is always the dominant phase, thereby obtaining an oil-in-acid system with an internal phase content of 63%-73%.

[0020] Furthermore, the acid solution is any one of conventional hydrochloric acid, terpineic acid, organic acid, or autogenous acid.

[0021] Furthermore, the oil phase is any one of diesel, white oil, or crude oil hydrocarbon fluids with a pour point below 0°C.

[0022] An emulsified acid nanoemulsifier is used for the preparation of high-temperature emulsified acid. The resulting emulsified acid with an internal phase content of 70% to 80% can remain stable for more than 2 hours at a high temperature of 180℃, with excellent slowing effect and a high final dissolution rate. This avoids the use of macromolecular polymers to stabilize the emulsion and effectively prevents residues from damaging the reservoir.

[0023] The beneficial effects of this invention are:

[0024] 1. The present invention provides an emulsified acid nanoemulsifier, which is composed of modified nanoparticles, betaine surfactant, nonionic surfactant, cationic surfactant, ethanol, and synthetic ester in a mass ratio of 10-25:10-15:10-20:20-30:10-20:20-40. The modified nanoparticles have a unique grafting structure and interfacial activity characteristics, which, in synergy with various surfactants and additives, can impart good stability to water-in-oil emulsions.

[0025] 2. The nano-emulsifier of the present invention is adsorbed at the oil-water interface, giving the interface good rigidity characteristics and good temperature stability and salt resistance, thus enabling the water-in-oil emulsion to have strong stability in high-temperature complex media environments.

[0026] 3. This invention can be used to prepare emulsified acid for acid fracturing of carbonate rocks at temperatures above 180°C. It can efficiently slow down the reaction rate of acid rocks, achieve deep penetration of acid, and avoid residue damage caused by polymer thickeners and gels as acid stabilizers. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the modified silica particles used as nanoemulsions.

[0029] Figure 2 This is a circuit diagram for the preparation of an alkyl (aromatic) amide silane coupling agent used in the modification of nanoparticles;

[0030] Figure 3 A circuit is prepared for another alkyl (aromatic) amide silane coupling agent used in the modification of nanoparticles;

[0031] Figure 4 A schematic diagram for the preparation of betaine silane coupling agents used in modified nanoparticles;

[0032] Figure 5 This is a schematic diagram of the surface structure of nanoparticles modified with the three silane coupling agents prepared in Examples 1, 2 and 3.

[0033] Figure 6 The change in particle size distribution curves before and after modification of nano-silica particles;

[0034] Figure 7 The demulsification of the emulsified acid prepared in Example 6 at high temperatures of 180°C, 160°C, and 140°C. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0036] This invention provides an emulsified acid nanoemulsifier, which is prepared by mixing modified nanoparticles, betaine surfactant, nonionic surfactant, cationic surfactant, ethanol, and synthetic ester in a mass ratio of 10-25:10-15:10-20:20-30:10-20:20-40, and then fully dispersing the mixture using a homogenizer at a stirring speed of 20,000-30,000 rpm. The synthetic ester is any one of ethyl acetate, butyl acetate, or isooctyl acetate with a melting point below 0°C.

[0037] Specifically, the modified nanoparticles were prepared by grafting nano-silica with alkyl (aromatic) amide silane coupling agents and betaine silane coupling agents. A schematic diagram of the surface structure of the modified nanoparticles is shown below. Figure 1 As shown;

[0038] Specifically, the alkyl (aromatic) amide silane coupling agent is prepared by dissolving alkyl (aromatic) acyl chloride and amino silane coupling agent in an organic solvent at a molar ratio of 1-2:1-3, with a reactant mass concentration of 10wt%-50wt%, a reaction temperature of 5-35℃, a reaction time of 2-5h, and removing the solvent by vacuum distillation after the reaction is completed.

[0039] Specifically, the alkyl (aromatic) acyl chloride is any one of the alkyl or aromatic acyl chloride molecules with 5 to 14 carbon atoms among phenylacetyl chloride, n-valeryl chloride, isovaleryl chloride, n-hexanoyl chloride, isohexanoyl chloride, n-octanoyl chloride, isooctanoyl chloride, n-decanoyl chloride, isodecanyl chloride, cyclopentylformyl chloride, and cyclohexylformyl chloride, which provides sufficient lipophilicity to the nanoparticles.

[0040] Specifically, the aminosilane coupling agent is any one of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, or 2-[(trimethoxysilyl)methyl]butane-1,4-diamine containing one or more primary or secondary amine structures.

[0041] Specifically, the organic solvent is any one of the non-hydroxyl organic solvents among dichloromethane, tetrahydrofuran, toluene, and acetone.

[0042] Specifically, the betaine silane coupling agent is prepared by reacting 1,3-propyl sulfonyl lactone with a tertiary amino silane coupling agent. The reaction involves dissolving 1,3-propyl sulfonyl lactone and the tertiary amino silane coupling agent in an organic solvent at a molar ratio of 1 to 1.3:1, with a reactant concentration of 5 wt% to 50 wt%, a reaction temperature of 30 to 60°C, and a reaction time of 2 to 5 hours. The organic solvent can be any solvent that does not dissolve betaine inner salts, such as acetone or dichloromethane, allowing the reaction product to precipitate directly. The purified product can then be obtained through filtration and drying.

[0043] Specifically, the tertiary amine silane coupling agent is any one of (N,N-dimethyl-3-aminopropyl)trimethoxysilane or N,N-diethyl-3-aminopropyltrimethoxysilane containing a tertiary amine structure.

[0044] The method for grafting and modifying nano-silica is as follows: alkyl (aromatic) amide silane coupling agent, betaine silane coupling agent and nano-silica are dispersed in an organic solvent at a mass ratio of 1-3:2-5:3-7. The mixture is then fully dispersed using a homogenizer at a stirring speed of 15000-30000 rpm, a reaction temperature of 40-60℃, and a reaction time of 5-6 h.

[0045] This invention also provides an application of an emulsified acid nanoemulsifier. 2-7 parts of the nanoemulsifier are fully dispersed in 25-30 parts of an oil phase, and the oil phase is continuously stirred at a mechanical stirring speed of 2000-5000 rpm. 63-73 parts of the prepared acid solution are dripped into the oil phase at a rate of 2-5 parts / min to ensure that the oil phase remains the dominant phase, thus obtaining an oil-in-acid system with an internal phase content of 63%-73%. Specifically, the acid solution is any one of conventional hydrochloric acid, terpineic acid, organic acid, or autogenous acid, and the oil phase is any one of diesel, white oil, or crude oil hydrocarbon fluids with a pour point below 0℃.

[0046] Example 1

[0047] A method for preparing an alkyl (aromatic) amide silane coupling agent for grafted modified nanoparticles is described. Phenylacetyl chloride and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane are used as reactants, dissolved in dichloromethane at a 1:1 molar ratio. The reactant concentration is 30 wt%. The temperature is set at 35°C, with magnetic stirring and reflux for 4 hours. After the reaction, the solvent is removed by vacuum distillation. The reaction route is as follows: Figure 2 As shown.

[0048] Example 2

[0049] Another method for preparing the alkyl (aromatic) amide silane coupling agent used in the grafted modified nanoparticles involves using cyclopentylformyl chloride and 2-[(trimethoxysilyl)methyl]butane-1,4-diamine as reactants, dissolved in dichloromethane at a molar ratio of 2:1, with a reactant concentration of 35 wt%. The temperature is set at 35°C, with magnetic stirring and reflux for 6 hours. After the reaction is complete, the solvent is removed by vacuum distillation. The reaction route is as follows: Figure 3 As shown.

[0050] Example 3

[0051] The method for preparing the betaine silane coupling agent used in the grafted modified nanoparticles involves using 1,3-propyl sulfonyl lactone and (N,N-dimethyl-3-aminopropyl)trimethoxysilane as reactants, dissolved in acetone at a molar ratio of 1.2:1, with a reactant concentration of 25 wt%. The temperature is set at 50°C, magnetically stirred, and refluxed for 8 hours. After the reaction is complete, the precipitate is filtered out and dried to obtain the reaction product. The reaction route is as follows: Figure 4 As shown.

[0052] Example 4

[0053] One method for preparing the grafted modified nanoparticles is as follows:

[0054] (1) The specific parameters of the selected nano silica material are: spherical structure, average diameter 25.5 nm, purity 99.9%, specific surface area 300~400 m² / g; the nano silica raw material is calcined in a muffle furnace at 700℃ for 12 hours to activate the hydroxyl groups on the surface of the nanoparticles.

[0055] (2) The three silane coupling agents prepared in Example 1, Example 2 and Example 3 were dispersed in tetrahydrofuran with silica at a mass ratio of 1:1:3:3. The mass concentration of the reactants was 20wt%. The mixture was dispersed in a homogenizer at a speed of 30000rpm for 10min.

[0056] (3) Heat to 50°C, stir with a magnetic stirrer, and reflux for 6 hours;

[0057] (4) After the reaction was completed, the solvent was removed by vacuum distillation to obtain the grafted modified nanoparticles.

[0058] (5) The surface modification of the modified silica nanoparticles is as follows: Figure 5 As shown.

[0059] The average particle size of the selected nano-silica particles increased from 25.5 nm to 32.7 nm before and after modification. The particle size distribution curves before and after modification are shown in the figure. Figure 6 As shown. (Data comes from dynamic light scattering experiments: the modified and unmodified nano-silica particles were fully dispersed in tetrahydrofuran solvent at a concentration of 0.2 wt%, and the particle size distribution was analyzed by dynamic light scattering).

[0060] Example 5

[0061] The preparation method of the nanoemulsifier is as follows: the modified nanoparticles prepared in Example 4, dodecyl sulfobetaine (BS-12), lauryl alcohol polyoxyethylene ether, dodecyl trimethylammonium chloride, ethanol, and isooctyl acetate are mixed in a mass ratio of 10:10:20:20:10:30, and the mixture is fully dispersed using a homogenizer at a stirring speed of 30,000 rpm for 2 hours to obtain a uniform dispersion system.

[0062] Example 6

[0063] Preparation and performance evaluation of emulsified acids.

[0064] Emulsified acid was prepared by dispersing 2-7 parts of the nano-emulsifier prepared in Example 5 into 25-30 parts of 0# diesel oil. The oil phase was continuously stirred at a mechanical stirring speed of 5000 rpm. 65 parts of the prepared acid solution were dripped into the oil phase at a rate of 4 parts / min to ensure that the oil phase remained the dominant phase, resulting in an oil-in-acid system with an internal phase content of 65%. The acid solution contained 15 wt% HCl + 2.0 wt% Mannich base corrosion inhibitor + 0.8 wt% EDTA. The prepared emulsified acid was divided into three equal portions, and the demulsification rate was tested at 140℃, 160℃, and 180℃ respectively, as shown in the results. Figure 7 As shown in the figure. The test results show that the emulsified acid with an internal phase content of 65% prepared using the nano-emulsifier prepared in Example 5 had a demulsification rate of less than 60%, 45%, and 30% after 2 hours under high temperature conditions of 180℃, 160℃, and 140℃, respectively, which fully demonstrates the advantages of the nano-emulsifier under high temperature conditions.

[0065] Example 7

[0066] Erosion experiments were conducted on marble at 180°C using gelling acid, crosslinking acid, and emulsified acid prepared in step 6. The slowing effect of the acid solutions was analyzed. The results showed that after 2 hours, the emulsified acid prepared in step 6 had a erosion rate of only 18% on marble at 180°C, while the gelling acid and crosslinking acid had erosion rates of 28% and 25% on marble, respectively. This demonstrates the excellent slowing effect of the emulsified acid prepared in step 6.

[0067] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An emulsified acid nanofluidifier characterized by, The modified nanoparticles, betaine surfactant, non-ionic surfactant, cationic surfactant, ethanol and synthetic ester are mixed in a mass ratio of 10-25:10-15:10-20:20-30:10-20:20-40, and a homogenizing disperser is used to fully disperse them at a stirring speed of 20,000-30,000 rpm to obtain the mixture; The modified nanoparticles are obtained by grafting and modifying nano-silica with alkyl or aromatic amide silane coupling agent and betaine silane coupling agent; The alkyl or aromatic amide silane coupling agent is dissolved in an organic solvent at a molar ratio of 1-2:1-3, the mass concentration of the reactants is 10wt%-50wt%, the reaction temperature is 5-35℃, the reaction time is 2-5h, and the solvent is removed by reduced pressure distillation after the reaction to obtain the alkyl or aromatic amide silane coupling agent; The alkyl or aromatic amide chloride is any one of phenylacetyl chloride, n-pentanoyl chloride, iso-pentanoyl chloride, n-hexanoyl chloride, iso-hexanoyl chloride, n-octanoyl chloride, iso-octanoyl chloride, n-decanoyl chloride, iso-decanoyl chloride, cyclopentyl formic chloride, and cyclohexyl formic chloride; The amino silane coupling agent is any one of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, and 2-[(trimethoxysilyl)methyl]butane-1,4-diamine; The betaine silane coupling agent is obtained by reacting 1,3-propyl sulfolactone with a tertiary amine silane coupling agent, and the tertiary amine silane coupling agent is any one of (N,N-dimethyl-3-aminopropyl)trimethoxysilane and N,N-diethyl-3-aminopropyl trimethoxysilane; The betaine surfactant is dodecyl sulfobetaine, the non-ionic surfactant is lauryl alcohol polyoxyethylene ether, and the cationic surfactant is dodecyl trimethyl ammonium chloride.

2. The emulsified acid nanoemulsifier of claim 1, wherein, The organic solvent is any one of dichloromethane, tetrahydrofuran, toluene, and acetone.

3. The emulsified acid nanoemulsifier of claim 1, wherein, The betaine silane coupling agent is obtained by dissolving 1,3-propyl sulfolactone and a tertiary amine silane coupling agent in an organic solvent at a molar ratio of 1-1.3:1, the concentration of the reactants is 5wt%-50wt%, the reaction temperature is 30-60℃, and the reaction time is 2-5h. The organic solvent is any one of acetone and dichloromethane.

4. The emulsified acid nanoemulsifier of claim 1, wherein, The method for grafting and modifying the nano-silica comprises dispersing the alkyl or aromatic amide silane coupling agent, the betaine silane coupling agent, and the nano-silica in an organic solvent at a mass ratio of 1-3:2-5:3-7, fully dispersing them by using a homogenizing disperser at a stirring speed of 15,000-30,000 rpm, and reacting at a temperature of 40-60℃ for 5-6h.

5. The emulsified acid nanoemulsifier of claim 1, wherein, The synthetic ester is any one of ethyl acetate, butyl acetate, and iso-octyl acetate.

6. Use of an emulsified acid nanoemulsifier characterized in that, Take 2-7 parts of the nano-emulsifier as claimed in any one of claims 1-5 to be fully dispersed in 25-30 parts of oil phase, and continuously stir the oil phase at a mechanical stirring speed of 2000 rpm-5000 rpm, drop 63-73 parts of prepared acid liquid into the oil phase at a speed of 2-5 parts / min to ensure that the oil phase is always the dominant phase, to prepare an oil-in-acid system with an internal phase content of 63%-73%.

7. Use of an emulsified acid nanoemulsifier according to claim 6, characterized in that, The acid liquid is any one of conventional hydrochloric acid, mud acid, organic acid, and self-generating acid; and the oil phase is any one of diesel oil, white oil, or crude oil with a condensation point lower than 0℃.

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