Microemulsion based on biosurfactant, its preparation method, application, and microemulsion type solubilizing imbibition agent prepared thereby

Abstract

The present invention provides a microemulsion based on a biosurfactant, a preparation method thereof, an application thereof, and a microemulsion type solubilizing imbibition agent prepared therefrom. In terms of mass percentage, the raw materials of the microemulsion include: 30-40% of a biosurfactant, 20-30% of an organic alcohol co-surfactant, 20-25% of an oil phase, and 5-30% of water; wherein, the biosurfactant is alkyl polyglycoside and / or rhamnolipid, and the rhamnolipid is R1 type rhamnolipid and / or R4 type rhamnolipid. The microemulsion and the microemulsion type solubilizing imbibition agent of the present invention have a smaller particle size and stronger stability, can freely flow in the micro-nano scale pores of ultra-low permeability-tight oil reservoirs, and improve the imbibition recovery rate of ultra-low permeability-tight oil reservoirs by reducing the oil-water interfacial tension, changing the wettability of the rock surface, solubilizing crude oil, reducing adsorption loss, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of microemulsions, and particularly relates to a microemulsion based on a biosurfactant, a preparation method thereof, an application thereof, and a microemulsion type solubilizing imbibition agent prepared therefrom. Background Art

[0002] With the continuous deepening of the exploration and development theory of ultra-low permeability - tight oil in lake basins, the exploration and development of continental ultra-low permeability - tight oil have made positive progress in recent years, showing huge resource potential and good development prospects. Due to the characteristics of ultra-low permeability - tight reservoirs, such as low permeability (generally less than 1 mD), small porosity (generally less than 10%), and extensive development of micro-nano pores, it is difficult to construct an effective displacement system. Currently, it is mainly developed through volume fracturing technology. However, after fracturing, only reservoir dissolved gas drive or depletion type exploitation is relied on, and the single-well production rate decreases rapidly and the recovery rate is low. The primary recovery rate is only 3 - 10%.

[0003] In order to solve the problems in the exploitation of ultra-low permeability - tight oil reservoirs and improve their development effects, enhanced oil recovery technologies such as gas injection development, water injection development, and imbibition oil displacement have been widely studied and field tested. Among them, gas injection development should pay attention to the acquisition and safety of gas sources; water injection development will have problems such as difficult injection and large migration resistance. Based on the characteristics of extensive development of micro-nano pores, strong heterogeneity, and strong capillary force in ultra-low permeability - tight oil reservoirs, imbibition oil displacement is an important measure to improve the recovery rate of ultra-low permeability - tight oil.

[0004] A microemulsion is an optically transparent and thermodynamically stable system formed by an oil phase, a water phase, a surfactant, and a co-surfactant, with a particle size between 1 - 100 nm and strong stability. However, in oil reservoir exploitation, microemulsions still have problems such as poor stability and difficulty in entering the deep part of the oil reservoir. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a microemulsion based on a biosurfactant, a preparation method thereof, an application thereof, and a microemulsion type solubilizing imbibition agent prepared therefrom, so as to obtain a microemulsion system with good solubilization performance.

[0006] To achieve the above purpose, the present invention provides a microemulsion based on a biosurfactant,

[0007] In terms of mass percentage, its raw materials include: 30 - 40% of biosurfactant, 20 - 30% of organic alcohol co-surfactant, 20 - 25% of oil phase, and 5 - 30% of water;

[0008] Among them, the biosurfactant is alkyl polyglycoside and / or rhamnolipid, and the rhamnolipid is R1 type rhamnolipid and / or R4 type rhamnolipid.

[0009] The structural formula of rhamnolipid of type R1 is as follows:

[0010]

[0011] The structural formula of rhamnolipid of type R4 is as follows:

[0012]

[0013] According to the specific embodiments of the present invention, preferably, the alkyl carbon chain length of the alkyl glycoside is 8 - 16, denoted as C8 - C16 alkyl glycoside. The HLB value of surfactants with a carbon chain length of 8 - 16 is 13 - 16, which are mainly hydrophilic surfactants and have good wetting, emulsifying and solubilizing effects.

[0014] According to the specific embodiments of the present invention, preferably, the organic alcohol co - surfactant includes one or a combination of two or more of n - propanol, n - butanol, n - pentanol and their isomers.

[0015] According to the specific embodiments of the present invention, preferably, the oil phase includes one or a combination of two or more of cyclohexane, n - hexane, white oil, and oleic acid ester.

[0016] The present invention also provides a preparation method of the above - mentioned microemulsion based on biosurfactant, which includes the following steps: mixing the biosurfactant, organic alcohol co - surfactant, oil phase and water in proportion, and stirring until the solution becomes clear and transparent to obtain the microemulsion based on biosurfactant.

[0017] In the preparation method of the above - mentioned microemulsion of biosurfactant, preferably, the stirring is carried out in a constant - temperature water bath at 20 - 50 °C, and the stirring speed is 100 - 300 r / min.

[0018] According to the specific embodiments of the present invention, preferably, the preparation method of the microemulsion based on biosurfactant includes the following steps:

[0019] Mix the biosurfactant and the organic alcohol co - surfactant in proportion to obtain intermediate product A;

[0020] Mix the intermediate product A and the oil phase in proportion to prepare a binary mixture to obtain intermediate product B;

[0021] Dropwise add water to the intermediate product B at a stirring speed of 100 - 300 r / min until the solution becomes clear and transparent to obtain the microemulsion based on biosurfactant.

[0022] The present invention also provides a microemulsion type solubilizing imbibition agent, the components of which include the above-mentioned microemulsion based on biosurfactant and water. Among them, the mass percentage of the microemulsion based on biosurfactant is 0.1-0.7%.

[0023] In the microemulsion type solubilizing imbibition agent of the present invention, water serves as the outer phase, oil serves as the inner phase, and the surfactant forms an oil-in-water structure surrounding the oil phase, thereby forming a core-shell structure with the oil phase as the core and the surfactant as the shell.

[0024] The microemulsion type solubilizing imbibition agent provided by the present invention is a clear and transparent single-phase microemulsion system, uniformly distributed with a core-shell nanostructure having a water phase as the shell and an oil phase as the core, with small particle size, high stability, and excellent interfacial properties. During the imbibition oil production process in ultra-low permeability-tight oil reservoirs, the microemulsion type solubilizing imbibition agent of the present invention has lower adsorption loss, obvious solubilization effect on crude oil, higher imbibition utilization degree for the crude oil in micro-nano pore throats, realizes migration deeper inside the reservoir, and improves the spontaneous imbibition oil drainage effect of micro-fractures during the huff and puff construction process.

[0025] The present invention also provides an application of the above-mentioned microemulsion based on biosurfactant or the above-mentioned microemulsion type solubilizing imbibition agent in imbibition displacement oil production in ultra-low permeability oil reservoirs, wherein the core permeability of the ultra-low permeability oil reservoir is <1 md.

[0026] In the above application, preferably, the ultra-low permeability oil reservoir is an ultra-low permeability tight oil reservoir, and the core permeability of the ultra-low permeability tight oil reservoir is <0.1 md.

[0027] An ultra-low permeability tight oil reservoir refers to an unconventional oil reservoir with a permeability below 1 md. The conventional enhanced oil recovery methods have poor production effects and are no longer applicable to ultra-low permeability-tight oil reservoirs. Imbibition refers to the process of wetting phase fluid displacing non-wetting phase fluid. Due to the existence of nano-scale pore throats in ultra-low permeability-tight oil reservoirs, the capillary force is large, and the imbibition displacement of crude oil has a significant effect. Therefore, imbibition oil production has become the main production method for ultra-low permeability-tight oil reservoirs. In the above application, preferably, the droplet size of the microemulsion based on biosurfactant is 5-20 nm.

[0028] The microemulsion raw materials of the present invention are green, non-toxic, environmentally friendly, easy to degrade, and have a high safety index. The preparation method is simple and easy to obtain. It has good interfacial properties and imbibition oil drainage effects, and can be used as an efficient microemulsion type solubilizing imbibition agent for huff and puff production in ultra-low permeability tight oil reservoirs. The on-site application process is simple, the production cost is low, and it has good market application prospects.

[0029] The technical solution provided by the present invention has the following beneficial effects:

[0030] The microemulsion prepared based on biosurfactant in the present invention selects rhamnolipids of R1 and R4 types, so that the further obtained microemulsion solubilizing imbibition agent has smaller particle size, stronger stability and solubilization effect, can flow freely in the micro-nano scale pores of ultra-low permeability-tight oil reservoirs, and can improve the imbibition recovery rate of ultra-low permeability-tight oil reservoirs by reducing the oil-water interfacial tension, changing the wettability of the rock surface, solubilizing crude oil, reducing adsorption loss, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the particle size distribution diagram (results of three measurements) of the microemulsion solubilizing imbibition agent in Example 2 of Experimental Example 1;

[0032] Figure 2 It is the transmission electron microscope scanning diagram of the emulsion solubilizing imbibition agent in Example 2 of Experimental Example 1;

[0033] Figure 3 It is the nuclear magnetic T2 spectrum diagram of the emulsion solubilizing imbibition agent in Example 2 of Experimental Example 5. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0035] Example 1

[0036] This example provides a microemulsion prepared based on biosurfactant. In terms of mass percentage, its raw materials include: 40% of R1 type rhamnolipid, 20% of n-propanol, 20% of cyclohexane, and 20% of deionized water;

[0037] Its preparation method includes the following steps:

[0038] (1) Mix the R1 type rhamnolipid and n-propanol in proportion to obtain intermediate product A;

[0039] (2) Mix intermediate product A with cyclohexane in proportion to obtain a quasi-binary mixture, that is, intermediate product B;

[0040] (3) Dropwise add deionized water to intermediate product B, and keep low-energy stirring at 200 r / min in a 30°C constant temperature water bath until the solution becomes clear and transparent to obtain a microemulsion based on biosurfactant.

[0041] This example also provides a microemulsion solubilizing imbibition agent. In terms of mass percentage, its composition is: 0.2% of the microemulsion based on biosurfactant in this example, and 99.8% of deionized water.

[0042] Example 2

[0043] This embodiment provides a microemulsion prepared based on a biosurfactant. In terms of mass percentage, its raw materials include: 40% of rhamnolipid of type R4, 30% of n-butanol, 23% of cyclohexane, and 7% of deionized water;

[0044] Its preparation method includes the following steps:

[0045] (1) Mix the rhamnolipid of type R4 and n-butanol in proportion to obtain intermediate product A;

[0046] (2) Mix intermediate product A and cyclohexane in proportion to obtain a quasi-binary mixture, i.e., intermediate product B;

[0047] (3) Dropwise add deionized water to intermediate product B, and maintain low-energy stirring at 200 r / min in a 30°C constant-temperature water bath until the solution becomes clear and transparent, obtaining a microemulsion based on the biosurfactant.

[0048] This embodiment also provides a microemulsion-type solubilizing and imbibition agent. In terms of mass percentage, its composition is: 0.3% of the microemulsion based on the biosurfactant of this embodiment, and 99.7% of deionized water.

[0049] Example 3

[0050] This embodiment provides a microemulsion prepared based on a biosurfactant. In terms of mass percentage, its raw materials include: 30% of C8 alkyl glycoside, 30% of n-pentanol, 25% of white oil, and 15% of deionized water;

[0051] Its preparation method includes the following steps:

[0052] (1) Mix the C8 alkyl glycoside and n-pentanol in proportion to obtain intermediate product A;

[0053] (2) Mix intermediate product A and white oil in proportion to obtain a quasi-binary mixture, i.e., intermediate product B;

[0054] (3) Dropwise add deionized water to intermediate product B, and maintain low-energy stirring at 200 r / min in a 30°C constant-temperature water bath until the solution becomes clear and transparent, obtaining a microemulsion based on the biosurfactant.

[0055] This embodiment also provides a microemulsion-type solubilizing and imbibition agent. In terms of mass percentage, its composition is: 0.5% of the microemulsion based on the biosurfactant of this embodiment, and 99.5% of deionized water.

[0056] Example 4

[0057] This embodiment provides a microemulsion prepared based on a biosurfactant. In terms of mass percentage, its raw materials include: 35% of C12 alkyl polyglycoside, 25% of n-butanol, 22% of n-hexane, and 18% of deionized water;

[0058] Its preparation method includes the following steps:

[0059] (1) Mix C12 alkyl polyglycoside and n-butanol in proportion to obtain intermediate product A;

[0060] (2) Mix intermediate product A with n-hexane in proportion to obtain a quasi-binary mixture, that is, intermediate product B;

[0061] (3) Dropwise add deionized water to intermediate product B, and maintain low-energy stirring at 200 r / min in a 30 °C constant temperature water bath until the solution becomes clear and transparent, obtaining a microemulsion based on a biosurfactant.

[0062] This embodiment also provides a microemulsion-type solubilizing and imbibing agent. In terms of mass percentage, its composition is: 0.3% of the microemulsion based on a biosurfactant in this embodiment, and 99.7% of deionized water.

[0063] Example 5

[0064] This embodiment provides a microemulsion prepared based on a biosurfactant. In terms of mass percentage, its raw materials include: 30% of C16 alkyl polyglycoside, 20% of n-butanol, 25% of acrylic ester, and 25% of deionized water;

[0065] Its preparation method includes the following steps:

[0066] (1) Mix C16 alkyl polyglycoside and n-butanol in proportion to obtain intermediate product A;

[0067] (2) Mix intermediate product A with acrylic ester in proportion to obtain a quasi-binary mixture, that is, intermediate product B;

[0068] (3) Dropwise add deionized water to intermediate product B, and maintain low-energy stirring at 200 r / min in a 30 °C constant temperature water bath until the solution becomes clear and transparent, obtaining a microemulsion based on a biosurfactant.

[0069] This embodiment also provides a microemulsion-type solubilizing and imbibing agent. In terms of mass percentage, its composition is: 0.7% of the microemulsion based on a biosurfactant in this embodiment, and 99.3% of deionized water.

[0070] Comparative Example 1

[0071] This comparative example provides a microemulsion prepared based on a biosurfactant. Its raw materials and preparation method are the same as those in Example 2, except that the biosurfactant in this comparative example is rhamnolipid of type R2.

[0072] This comparative example also provides a microemulsion solubilizing and imbibing agent. By mass percentage, its composition is: 0.3% of the microemulsion based on biosurfactant of this comparative example, and 99.7% of deionized water.

[0073] Comparative Example 2

[0074] This comparative example provides a microemulsion prepared based on biosurfactant. Its raw materials and preparation method are the same as those of Example 1, except that the biosurfactant of this comparative example is rhamnolipid of R3 type.

[0075] This comparative example also provides a microemulsion solubilizing and imbibing agent. By mass percentage, its composition is: 0.2% of the microemulsion based on biosurfactant of this comparative example, and 99.8% of deionized water.

[0076] Experimental Example 1 Particle Size Test

[0077] The particle size distribution and morphological structure of the microemulsion solubilizing and imbibing agent of the above examples were tested by dynamic light scattering method and microscopy method.

[0078] Using a nano laser particle size and ZETA potential analyzer, the particle size distribution of the "core - shell structure" was quantitatively analyzed. Among them, the particle size distribution diagram of the microemulsion solubilizing and imbibing agent of Example 2 is as Figure 1 shown; using a transmission electron microscope, the particle size and morphological structure inside the microemulsion solubilizing and imbibing agent of Example 2 were observed, and the results are as Figure 2 shown.

[0079] The average particle sizes of the microemulsion solubilizing and imbibing agents of Examples 1 - 5 and Comparative Examples 1 - 2 are shown in Table 1, among which Example 2 has the smallest particle size of 5 nm.

[0080] Table 1 Average Particle Sizes of Microemulsion Solubilizing and Imbibing Agents

[0081]

[0082]

[0083] It can be seen from Comparative Examples 1 and 2 that compared with rhamnolipids of R2 and R4 types, using rhamnolipids of R1 and R4 types as biosurfactants in the present invention can obtain a microemulsion solubilizing and imbibing agent with a smaller particle size.

[0084] Experimental Example 2 Interfacial Tension Test

[0085] Surface tension test method: Using a Krüss K100 type surface tension meter, the surface tension between the microemulsion solubilizing and imbibing agent based on biosurfactant and crude oil was measured by the hanging - plate method in SY / T 5370 - 1999.

[0086] Interfacial tension test method: Using a TX-500 rotating drop interfacial tensiometer, the interfacial tension between the microemulsion solubilizing imbibition agent based on biosurfactant and crude oil was measured by the pendant drop method in SY / T 5370-1999. Keep the rotation speed at 6000 r / min and the time interval at 1 min, and measure the interfacial tension with crude oil.

[0087] The measurement results are shown in Table 2. It can be seen from Table 2 that Examples 1-5 can all reduce the surface / interfacial tension. Among them, the interfacial tension in Examples 1-3 is significantly reduced; the ability of Comparative Examples 1-2 to reduce the interfacial tension is weak. Therefore, the R1 and R4 types of rhamnolipids used in the present invention can further reduce the surface tension of the microemulsion solubilizing imbibition agent and the interfacial tension between it and crude oil.

[0088] Table 2 Surface tension of microemulsion solubilizing imbibition agent and interfacial tension with crude oil

[0089] System Surface tension / (mN / m) Interfacial tension / (mN / m) Temperature / °C Example 1 27.6 1.76 25.2℃ Example 2 27.4 1.40 25.0℃ Example 3 27.4 1.46 25.1℃ Example 4 28.5 2.02 25.1℃ Example 5 29.3 2.37 25.2℃ Comparative Example 1 30.3 2.79 25.0℃ Comparative Example 2 30.8 3.01 24.9℃

[0090] Experimental Example 3 Wettability test

[0091] According to the petroleum and natural gas industry standard SY / T 5153-2017, the contact angle of the microemulsion solubilizing imbibition agent of the above examples was measured by the contact angle method in the wettability test method of reservoir rocks to simulate the wettability of reservoir cores. The quartz sheet was treated as required, and after sucking the oil drop with a micro syringe, the oil drop was injected under the quartz sheet, and the contact angle formed between the solid surface and the oil-water contact surface was measured with a contact angle measuring instrument. The measurement results are shown in Table 3.

[0092] Table 3 Wettability angle of microemulsion solubilizing imbibition agent

[0093] System Original wetting angle / ° Wetting angle after modification / ° Example 1 121 43 Example 2 124 27 Example 3 118 47 Example 4 122 52 Example 5 122 61 Comparative Example 1 120 71 Comparative Example 2 121 78

[0094] It can be seen from Table 3 that the wettability angles of the microemulsion solubilizing imbibition agents in Examples 1-5 can modify the lipophilic surface to a hydrophilic surface and have the ability of wettability reversal. Among them, the wettability angle of Example 2 is the smallest and the wettability reversal ability is the strongest. The wettability reversal abilities of Comparative Examples 1 and 2 are poor. The R1 and R4 types of rhamnolipids used in the present invention can improve the wettability of the microemulsion solubilizing imbibition agent.

[0095] Experimental Example 4 Crude oil solubilization performance test

[0096] The solubilization of oil by the microemulsion solubilizing imbibition agent can be macroscopically expressed by the mass solubilization ratio (WSR). It is calculated by Formula 1:

[0097]

[0098] In the formula, S oRefers to the concentration of dissolved petroleum, expressed in mg / L; S o，CMC Refers to the concentration of surfactant at the CMC value, which can dissolve petroleum, expressed in mg / L; C S Represents the concentration of surfactant corresponding to the dissolution of the above So concentration of petroleum, expressed in mg / L; C S,CMC Represents the CMC concentration of the surfactant, expressed in mg / L.

[0099] (1) Add 100 mL of kerosene to the 25 mL in the example to ensure maximum solubility. Seal the sample bottle with a screw cap and put on a PTFE-lined diaphragm to prevent the loss of kerosene by volatilization.

[0100] (2) Balance these samples on a reciprocating shaker for 48 hours at a temperature of 25 °C, and then centrifuge the samples with a Centrifuge Model 800 centrifuge. Centrifuge for 30 minutes at a speed of 3000 r / min to separate the undissolved kerosene.

[0101] (3) Determine the concentration of kerosene dissolved in water using an infrared oil analyzer according to the specification HJ970-2018.

[0102] Each group of tests is carried out three times, and the average value is taken as the test result of this test, as shown in Table 4.

[0103] Table 4 Solubilization coefficient of microemulsion solubilizing imbibition agent

[0104] System WSR Example 1 0.097 Example 2 0.148 Example 3 0.091 Example 4 0.084 Example 5 0.08 Comparative Example 1 0.065 Comparative Example 2 0.057

[0105] It can be seen from the test results that the microemulsion solubilizing imbibition agent in Example 2 has the highest solubilization ratio (WSR) and the strongest oil solubilization ability.

[0106] Experimental Example 5 Test of imbibition recovery rate and pore crude oil mobilization degree

[0107] (1) Use a core vacuum saturation experimental device to saturate the core by the method of vacuum pumping and high pressure. Dry the core, measure the dry weight, length and diameter, and use a vacuum pump to evacuate the core for 24 h; then, saturate with kerosene and pressurize to 10 MPa, and age for one week; take out the core and weigh it, and calculate the mass difference Δm of the core before and after oil saturation.

[0108] (2) Carry out a static imbibition experiment using the imbibition bottle method, and conduct nuclear magnetic resonance testing of rock samples based on the reference standard SY / T 6490-2014 to calculate the imbibition recovery rate of the microemulsion solubilizing imbibition agents in Examples 1-5 and the mobilization degree of each pore oil.

[0109] The imbibition recovery rate is as shown in Equation 2:

[0110]

[0111] The nuclear magnetic T2 spectrum of Example 2 is as Figure 3 shown, and the oil displacement degree of each pore can be calculated according to the T2 spectrum, as shown in Equation 3:

[0112]

[0113] where r oi is the imbibition recovery rate, %; v oi is the imbibition oil drainage volume, mL; ρ is the oil density, g / mL; Δm is the mass difference before and after saturation with kerosene, g; c i is the oil displacement degree of each pore, %; ΔT i is the change in the total T2 signal value in this pore; T i is the initial total T2 signal value in this pore.

[0114] The imbibition recovery rates and pore displacement degrees of the microemulsion solubilizing imbibition agents of Examples 1-5 and Comparative Examples 1-2 are shown in Tables 5 and 6.

[0115] Table 5 Imbibition recovery rates of microemulsion solubilizing imbibition agents based on biosurfactants

[0116] System Imbibition recovery rate / % Example 1 40 Example 2 43 Example 3 38 Example 4 36 Example 5 37 Comparative Example 1 33 Comparative Example 2 30

[0117] Table 6 Pore displacement degrees of microemulsion solubilizing imbibition agents based on biosurfactants

[0118] System Utilization degree of small pores / % Utilization degree of medium pores / % Utilization degree of large pores / % Example 1 56.64 50.34 -6.98 Example 2 60.75 46.74 -7.49 Example 3 55.93 48.56 -4.49 Example 4 50.78 47.90 1.32 Example 5 52.81 48.73 -1.54 Comparative Example 1 48.91 49.24 1.85 Comparative Example 2 46.81 47.19 6.00

[0119] From the above results, it can be seen that the microemulsion solubilizing imbibition agents of Examples 1-5 all show good recovery rates, and the displacement degrees of small pores all reach more than 50%. Among them, the recovery rate of Example 2 is as high as 43%, and the highest displacement degree of small pores reaches 60.75%. The recovery rates of Comparative Examples 1 and 2 are relatively low. It can be seen that the present invention improves the recovery rate of the microemulsion solubilizing imbibition agent by using R1 and R4 types of rhamnolipids.

Claims

1. A microemulsion solubilizing imbibition agent, which is used for imbibition displacement oil production in ultra-low permeability oil reservoirs with core permeability < 0.1 md. By mass percentage, the composition of the microemulsion solubilizing imbibition agent is: 0.3% of a microemulsion based on biosurfactant and 99.7% of deionized water; The droplet size of the microemulsion solubilizing and imbibing agent is 5 nm; By mass percentage, the raw materials of the biosurfactant-based microemulsion include: 40% of rhamnolipid of type R4, 30% of n-butanol, 23% of cyclohexane, and 7% of deionized water; The preparation method of the raw materials of the biosurfactant-based microemulsion comprises the following steps: (1) Mix rhamnolipid of type R4 and n-butanol in proportion to obtain intermediate product A; (2) Mix intermediate product A and cyclohexane in proportion to obtain a quasi-binary mixture, i.e., intermediate product B; (3) Dropwise add deionized water to intermediate product B, and keep low-energy stirring at 200 r / min in a 30 °C constant temperature water bath until the solution becomes clear and transparent to obtain the biosurfactant-based microemulsion.

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