Medium-phase microemulsion as well as preparation method and application thereof

Abstract

The invention provides a middle-phase microemulsion as well as a preparation method and application thereof. The middle-phase microemulsion comprises a surfactant, a surfactant additive, inorganic salt, crude oil and water, wherein the surface active agent is an anionic-nonionic surface active agent, the surface active agent comprises a surface active agent APEG-LY-SSS, the structural formula of the surface active agent is # imgabs0 #, x is more than or equal to 5 and less than or equal to 15, y is more than or equal to 2 and less than or equal to 20, z is more than or equal to 4 and less than or equal to 10, R1 is H or CH3, and R2 is C2-C18 alkyl, hydroxyethyl, hydroxypropyl or methoxyl group. The middle-phase microemulsion prepared by the method has excellent anti-adsorption performance, high temperature resistance and salt resistance and wide industrial application prospect.

Description

Technical Field

[0001] The invention relates to the field of oilfield chemistry, and in particular to a middle-phase microemulsion and a preparation method and application thereof. Background Art

[0002] Microemulsion refers to an isotropic colloidal dispersion system spontaneously formed by water, surfactants, cosolvents and oil. Due to its large specific surface area, small particle size, low interfacial tension and unique solubilization and penetration capabilities, it is widely used in the petroleum industry, especially in the field of enhanced oil recovery.

[0003] According to the equilibrium state of water and oil in microemulsion, Winsor subdivided microemulsion into four types. Among them, Winsor I type microemulsion is a multiphase system in which O / W type microemulsion and excess oil phase coexist, and Winsor II type microemulsion is a multiphase system in which W / O type microemulsion and excess water phase coexist. There is another morphological state between the above two multiphase systems, called Winsor III type microemulsion, which refers to the coexistence of oil and water bicontinuous phase microemulsion, in which the oil phase and the water phase are both continuous phase and dispersed phase, forming a network structure, without obvious oil droplets or water droplets, also called middle phase microemulsion. Winsor IV type microemulsion refers to a single-phase microemulsion, which can also be divided into three types: O / W type, W / O type and bicontinuous type.

[0004] For the Winsor III type microemulsion system, the middle phase microemulsion can form a miscible oil wall with the residual oil in the reservoir, which plays a vital role in microemulsion flooding, thereby achieving efficient displacement, which is much higher than the other two types of microemulsion oil washing efficiency. The Chinese invention patent (application number 202110388654.6) discloses an in-situ generated middle phase microemulsion oil washing system, which specifically discloses that the system composition includes anionic surfactants, non-ionic surfactants, co-surfactants and salts, and tests the oil washing efficiency at 25°C, but the temperature resistance and adsorption resistance of the system need to be improved.

[0005] Therefore, the middle phase microemulsion in the prior art has the problems of poor temperature resistance or poor adsorption resistance, and it is urgent to provide a middle phase microemulsion and a preparation method thereof to improve the above problems. Summary of the invention

[0006] The main purpose of the present invention is to provide a middle phase microemulsion and a preparation method and application thereof, so as to solve the problems of poor temperature resistance or poor adsorption resistance of the middle phase microemulsion in the prior art.

[0007] In order to achieve the above object, according to one aspect of the present invention, a middle phase microemulsion is provided, which includes a surfactant, a surfactant adjuvant, an inorganic salt, crude oil and water; wherein the surfactant is an anionic nonionic surfactant, and the surfactant includes a surfactant APEG-LY-SSS, and its structural formula is: Among them, 5≤x≤15, 2≤y≤20, 4≤z≤10, R1 is H or CH3, and R2 is a C2~C18 alkyl group, hydroxyethyl, hydroxypropyl or methoxy group.

[0008] Furthermore, in addition to the surfactant APEG-LY-SSS, the surfactant also includes one or more of sodium fatty alcohol polyoxyethylene ether sulfonate, sodium dodecyl sulfate, sodium alkyl diphenyl ether disulfonate or petroleum sulfonate, and sodium fatty alcohol polyoxyethylene ether sulfonate is further preferred; preferably, the weight ratio of the surfactant APEG-LY-SSS to the sodium fatty alcohol polyoxyethylene ether sulfonate is 1:(1 to 10) by weight percentage.

[0009] Furthermore, in terms of weight percentage, the components of the middle phase microemulsion include 0.5-4.5 wt % of a surfactant, 1.5-6.5 wt % of a surfactant adjuvant, 0.5-4.0 wt % of an inorganic salt, 85.0-97.5 wt % of crude oil and the balance of water.

[0010] Furthermore, the surfactant adjuvant is selected from alcohol solvents, preferably one or more of n-hexanol, n-butanol or n-pentanol; and the inorganic salt is preferably sodium chloride and / or potassium chloride.

[0011] Furthermore, the components of the middle phase microemulsion include 1.2-4.5wt% of surfactant, 2.5-5.5wt% of surfactant adjuvant, 0.5-2.5wt% of inorganic salt, 87.5-94.5wt% of crude oil and the balance of water; preferably, the water is reinjection sewage and / or tap water.

[0012] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing a middle phase microemulsion is provided, and the preparation method comprises: step S1, taking a surfactant auxiliary, an inorganic salt and water in a stoppered colorimetric tube and stirring them once to obtain a mixed solution; step S2, taking a surfactant and crude oil in the mixed solution and stirring them twice to obtain a middle phase microemulsion.

[0013] Furthermore, in terms of weight percentage, the weight ratio of surfactant adjuvant, inorganic salt and water is 1:(0.2-2.5):(30-70); preferably, the weight ratio of surfactant to crude oil is (0.01-0.30):1.

[0014] Furthermore, the rotation speed of the primary stirring is 100-500 rpm, the primary stirring time is 0.1-1.0 h, and the primary stirring temperature is 20-50°C.

[0015] Furthermore, the rotation speed of the secondary stirring is 200-400 rpm, the secondary stirring time is 0.5-2.0 h, and the secondary stirring temperature is 20-50° C.

[0016] According to another aspect of the present invention, there is provided a middle phase microemulsion or a middle phase microemulsion obtained by the preparation method of the middle phase microemulsion for use in the field of oil and gas field exploitation, deep water plugging and profile control or tertiary oil recovery technology in oil fields.

[0017] By applying the technical solution of the present invention, the prepared middle phase microemulsion has excellent anti-adsorption performance, strong temperature resistance and salt resistance, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 The graph shows the volume distribution of nanoparticle size of the middle phase microemulsion of Example 1 of the present invention. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] According to the background technology part of the present invention, the middle phase microemulsion in the prior art has the problem of poor temperature resistance or poor adsorption resistance. In view of the above problems, the present invention provides a middle phase microemulsion, which includes a surfactant, a surfactant adjuvant, an inorganic salt, crude oil and water; wherein the surfactant is an anionic nonionic surfactant, and the surfactant includes a surfactant APEG-LY-SSS, and its structural formula is: Among them, 5≤x≤15, 2≤y≤20, 4≤z≤10, R1 is H or CH3, and R2 is a C2~C18 alkyl group, hydroxyethyl, hydroxypropyl or methoxy group.

[0022] The middle phase microemulsion system provided by the present invention contains a surfactant component, wherein the surfactant is an anionic nonionic surfactant, especially the surfactant APEG-LY-SSS. Firstly, the surfactant has a large number of ethoxy groups on the side chain, so that the middle phase microemulsion system has excellent water solubility and surface activity. Secondly, the structural chain segment of the surfactant in the present invention has a large number of benzene ring groups, which can enhance the rigidity of its molecular chain and improve the temperature resistance and shear resistance; wherein the three oxygen atoms of the -SO3- structure in the sulfonic acid group have two π bonds and a negative charge, so that its stability is further enhanced, thereby being not affected by cations (such as Ca 2+ Mg 2+ etc.), so the sulfonate ions loaded on its chain segments make the surfactant have good temperature and salt resistance; finally, the hydrophobic long chains on its chain segments play a role in adjusting the HLB value of the surfactant, so that the surfactant can be applied to various oil phases, significantly improving its compatibility when preparing microemulsions, reducing surface interfacial tension, and improving its anti-adsorption performance. In summary, the surfactant APEG-LY-SSS in the present invention has a long chain structure in its structure that improves the temperature resistance and adsorption resistance of the middle phase microemulsion system to a certain extent, and the large amount of ethylene oxide structures contained in its structure also plays a role in reducing surface interfacial tension, thereby making the middle phase microemulsion system in the present invention have good temperature resistance and adsorption resistance. Experiments have shown that the viscosity of the middle phase microemulsion system in the present invention reaches 15mPa·s under the conditions of 95°C and 26000mg / L mineralization, and can form 10 -3 The ultra-low interfacial tension of mN / m, the adsorption amount in oil sands after 24 hours is about 9 mg / g, and it has good temperature resistance and anti-adsorption properties.

[0023] In a preferred embodiment, in addition to the surfactant APEG-LY-SSS, the surfactant also includes one or more of sodium alcohol polyoxyethylene ether sulfonate, sodium dodecyl sulfate, sodium alkyl diphenyl ether disulfonate or petroleum sulfonate, and sodium alcohol polyoxyethylene ether sulfonate is further preferred. In terms of weight percentage, the weight ratio of surfactant APEG-LY-SSS to sodium alcohol polyoxyethylene ether sulfonate is more preferably 1:(1 to 10), so as to further improve its compatibility in the preparation of the middle phase microemulsion, reduce the surface interfacial tension, and improve its anti-adsorption performance.

[0024] In a preferred embodiment, the components of the middle phase microemulsion include, by weight percentage, 0.5 to 4.5 wt % of a surfactant, 1.5 to 6.5 wt % of a surfactant adjuvant, 0.5 to 4 wt % of an inorganic salt, 85.0 to 97.5 wt % of crude oil and the remainder of water, thereby further improving the adsorption resistance and temperature resistance of the middle phase microemulsion system.

[0025] In order to further improve the solubilization and wetting effect of the middle phase microemulsion system and improve its dispersibility, the surfactant auxiliary is preferably an alcohol solvent, further selected from one or more of n-hexanol, n-butanol or n-pentanol, and the inorganic salt is further preferably sodium chloride and / or potassium chloride.

[0026] In order to further improve the anti-adsorption and temperature resistance of the middle phase microemulsion system, the components of the middle phase microemulsion preferably include 1.2-4.5wt% of a surfactant, 2.5-5.5wt% of a surfactant adjuvant, 0.5-2.5wt% of an inorganic salt, 87.5-94.5wt% of crude oil and the remainder of water; the water is further preferably reinjection sewage and / or tap water.

[0027] Another aspect of the present invention provides a method for preparing a middle phase microemulsion, the method comprising: step S1, taking a surfactant auxiliary, an inorganic salt and water in a stoppered colorimetric tube and stirring once to obtain a mixed solution; step S2, taking a surfactant and crude oil in the mixed solution and stirring twice to obtain a middle phase microemulsion. The middle phase microemulsion prepared by the method has excellent temperature resistance and adsorption resistance, and the preparation method is simple, easy to operate, suitable for large-scale production, and has broad industrial application prospects.

[0028] In a preferred embodiment, the weight ratio of surfactant adjuvant, inorganic salt and water is 1:(0.2-2.5):(30-70); thereby preparing the prepared middle phase microemulsion and further improving its temperature resistance and anti-adsorption properties. It is further preferred that the weight ratio of surfactant to crude oil is (0.01-0.3):1.

[0029] In order to further improve the uniform dispersion of the components in the middle phase microemulsion system, the first stirring speed is 100-500 rpm, the first stirring time is 0.1-1.0 h, and the first stirring temperature is 20-50°C; it is further preferred that the second stirring speed is 200-400 rpm, the second stirring time is 0.5-2.0 h, and the second stirring temperature is 20-50°C.

[0030] Another aspect of the present invention also provides a method for preparing the surfactant APEG-LY-SSS: after mixing allyl polyoxyethylene ether, sodium styrene sulfonate and deionized water, add to a three-necked flask equipped with a stirrer, stir in a constant temperature water bath at 40-60°C; add a mixed solution of acrylate monomer and isopropanol and an aqueous solution of ammonium persulfate under a water bath at 65-80°C, react for 1-5 hours, cool to room temperature, wash the product with acetone, dry and grind into powder. The acrylate monomer is one or more of lauryl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methyl methacrylate or octadecyl acrylate.

[0031] In order to further improve the reaction activity of surfactant APEG-LY-SSS, improve its reaction conversion rate and product yield, the weight ratio of allyl polyoxyethylene ether, sodium styrene sulfonate and deionized water is preferably (0.05-0.25):(0.05-0.15):1; the acrylate monomer preferably accounts for 35-50wt% of the mixed solution of acrylate monomer and isopropanol.

[0032] Another aspect of the present invention also provides an application of a middle phase microemulsion obtained by the middle phase microemulsion preparation method in the field of oil and gas field exploitation, deep water plugging and profile control, or tertiary oil recovery technology in oil fields.

[0033] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0034] Example 1

[0035] Take 2g of allyl polyoxyethylene ether, 1g of sodium styrene sulfonate and 10mL of deionized water, mix them, add them into a three-necked flask equipped with a stirrer, and stir them evenly in a constant temperature water bath at 60°C; add a mixed solution of lauryl acrylate and isopropanol and an aqueous solution of ammonium persulfate (2g of lauryl acrylate is dissolved in 2mL of isopropanol, and 0.32g of ammonium persulfate is dissolved in 0.68g of deionized water to form an initiator aqueous solution) dropwise at the same time under a 75°C water bath, react for 3h, cool to room temperature, wash the product with acetone, dry and grind it into powder, thereby preparing a surfactant APEG-LY-SSS, denoted as APEG-LY-SSS-A, whose structural formula is Where x=10, y=15, z=8.

[0036] 0.7 g of sodium chloride, 1.5 g of n-butanol and 2 g of water were added to a stoppered colorimetric tube and stirred once at a speed of 400 rpm, a stirring time of 0.5 h and a stirring temperature of 30°C to prepare a mixed solution of salt and n-butanol; 0.25 g of sodium polyoxyethylene fatty alcohol ether sulfonate, 0.15 g of APEG-LY-SSS-A and 0.3 g of sodium dodecyl sulfate were added to the mixed solution; 14 mL of reinjection sewage and 16 mL of crude oil were added for a second stirring at a speed of 300 rpm, a stirring time of 1 h and a stirring temperature of 30°C to obtain a middle phase microemulsion. Figure 1 The volume distribution diagram of nanoparticle size of the middle phase microemulsion is shown.

[0037] The components of the middle phase microemulsion include: 2.03wt% of surfactant, 3.19wt% of surfactant adjuvant, 2.03wt% of inorganic salt, 92.75wt% of crude oil and the balance of water; wherein the surfactant includes (relative to the total mass): 0.73wt% of sodium fatty alcohol polyoxyethylene ether sulfonate, 0.43wt% of APEG-LY-SSS-A, and 0.87wt% of sodium dodecyl sulfate.

[0038] Example 2

[0039] The only difference from Example 1 is that the raw materials of the middle phase microemulsion are 0.3 g of sodium chloride, 1.8 g of n-butanol, 0.15 g of sodium fatty alcohol polyoxyethylene ether sulfonate and 0.25 g of petroleum sulfonate.

[0040] The components of the middle phase microemulsion include: 1.59wt% of surfactant, 5.19wt% of surfactant adjuvant, 0.87wt% of inorganic salt, 92.35wt% of crude oil and the balance of water; wherein the surfactant includes (relative to the total mass): 0.44wt% of sodium fatty alcohol polyoxyethylene ether sulfonate, 0.43wt% of APEG-LY-SSS-A, and 0.72wt% of petroleum sulfonate.

[0041] Example 3

[0042] Take 2g of allyl polyoxyethylene ether, 1g of sodium styrene sulfonate and 10mL of deionized water, add to a three-necked flask equipped with a stirrer, and stir evenly in a constant temperature water bath at 50°C; add a mixture of hydroxyethyl methacrylate and isopropanol and an aqueous solution of ammonium persulfate (2g of hydroxyethyl methacrylate is dissolved in 2mL of isopropanol, and 0.32g of ammonium persulfate is dissolved in 0.68g of deionized water to form an initiator aqueous solution) at the same time under 80°C water bath conditions, react for 4h, cool to room temperature, wash the product with acetone, dry and grind into powder, thereby preparing the surfactant APEG-LY-SSS, denoted as APEG-LY-SSS-B. Its structural formula is Among them, x=8, y=20, z=4.

[0043] The preparation steps of the middle phase microemulsion are the same as those of Example 1, except that the raw materials used are 0.4 g potassium chloride, 0.16 g sodium fatty alcohol polyoxyethylene ether sulfonate, 0.1 g APEG-LY-SSS-B, and an additional 0.15 g petroleum sulfonate.

[0044] The components of the middle phase microemulsion include: 2.05wt% of surfactant, 4.33wt% of surfactant adjuvant, 1.16wt% of inorganic salt, 92.46wt% of crude oil and the balance of water; wherein the surfactant includes (relative to the total mass): 0.46wt% of sodium fatty alcohol polyoxyethylene ether sulfonate, 0.29wt% of APEG-LY-SSS-B, 0.43wt% of petroleum sulfonate and 0.87wt% of sodium dodecyl sulfate.

[0045] Example 4

[0046] Take 2g of allyl polyoxyethylene ether, 1g of sodium styrene sulfonate and 10mL of deionized water, add to a three-necked flask equipped with a stirrer, and stir evenly in a constant temperature water bath at 40°C; add a mixture of octadecyl acrylate and isopropanol, and an aqueous solution of ammonium persulfate (2g of octadecyl acrylate is dissolved in 2mL of isopropanol, and 0.32g of ammonium persulfate is dissolved in 0.68g of deionized water to form an initiator aqueous solution) at the same time in a water bath at 65°C, react for 5h, cool to room temperature, wash the product with acetone, dry and grind into powder. Thus, the surfactant APEG-LY-SSS is prepared, denoted as APEG-LY-SSS-C. Its structural formula is Among them, x=15, y=2, z=8.

[0047] The preparation steps of the middle phase microemulsion are the same as those in Example 1, except that the raw materials used are 0.6 g sodium chloride, 1.8 g n-butanol, 0.17 g sodium alcohol polyoxyethylene ether sulfonate, 0.1 g APEG-LY-SSS-C, and an additional 0.15 g sodium alkyl diphenyl ether disulfonate.

[0048] The components of the middle phase microemulsion include: 2.05wt% of surfactant, 5.13wt% of surfactant adjuvant, 1.71wt% of inorganic salt, 91.12wt% of crude oil and the balance of water; wherein the surfactant includes (relative to the total mass): 0.48wt% of sodium fatty alcohol polyoxyethylene ether sulfonate, 0.28wt% of APEG-LY-SSS-C, 0.43wt% of sodium alkyl diphenyl ether disulfonate and 0.85wt% of sodium dodecyl sulfate.

[0049] Example 5

[0050] The only difference from Example 1 is that the raw materials of the middle phase microemulsion are 0.5 g of sodium chloride, 1.8 g of n-butanol, 0.25 g of sodium fatty alcohol polyoxyethylene ether sulfonate, and 0.05 g of APEG-LY-SSS-A.

[0051] The components of the middle phase microemulsion include: 1.72wt% of surfactant, 5.16wt% of surfactant adjuvant, 1.43wt% of inorganic salt, 91.69wt% of crude oil and the remainder of water; wherein the surfactant includes (relative to the total mass): 0.72wt% of sodium fatty alcohol polyoxyethylene ether sulfonate, 0.14wt% of APEG-LY-SSS-A and 0.86wt% of sodium dodecyl sulfate.

[0052] Example 6

[0053] Take 2g of allyl polyoxyethylene ether, 1g of sodium styrene sulfonate and 10mL of deionized water, add to a three-necked flask equipped with a stirrer, and stir evenly in a constant temperature water bath at 40°C; add a mixture of ethyl acrylate and isopropanol and an aqueous solution of ammonium persulfate (2g of ethyl acrylate is dissolved in 2mL of isopropanol, and 0.32g of ammonium persulfate is dissolved in 0.68g of deionized water to form an initiator aqueous solution) at the same time in a water bath at 65°C, react for 5h, cool to room temperature, wash the product with acetone, dry and grind into powder. Thus, the surfactant APEG-LY-SSS is prepared, denoted as APEG-LY-SSS-D. Its structural formula is Among them, x=5, y=10, z=10.

[0054] Example 7

[0055] The only difference from Example 1 is that the surfactant used is APEG-LY-SSS-C, whose structural formula is R2, where the substituent is a carbon chain C18 alkane.

[0056] Comparative Example 1

[0057] The difference from Example 1 is that the surfactant APEG-LY-SSS-A is not added.

[0058] Comparative Example 2

[0059] The difference from Example 1 is that the weight ratio of surfactant APEG-LY-SSS-A to sodium fatty alcohol polyoxyethylene ether sulfonate is 1:0.1.

[0060] Comparative Example 3

[0061] The difference from Example 1 is that the weight ratio of surfactant APEG-LY-SSS-A to sodium fatty alcohol polyoxyethylene ether sulfonate is 1:15.

[0062] Comparative Example 4

[0063] The difference from Example 1 is: 0.1 wt% of surfactant.

[0064] Comparative Example 5

[0065] The difference from Example 1 is: 10 wt% of surfactant.

[0066] Performance Testing:

[0067] 1) Temperature resistance

[0068] The middle phase microemulsion was taken and used to prepare an aqueous solution with a mass concentration of 0.01% with clean water. The interfacial tension between the temperature-resistant and anti-adsorption middle phase microemulsion and crude oil was measured at 95°C using a spinning drop interfacial tension meter at a rotation speed of 3000-6000rpm.

[0069] 2) Salt tolerance

[0070] The middle phase microemulsion was taken and an aqueous solution with a mass concentration of 0.01% was prepared with clean water and 26000 mg / L mineralized brine respectively. The interfacial tension (in mN / m) between the temperature-resistant and adsorption-resistant middle phase microemulsion and crude oil was measured using a spinning drop interfacial tension meter at a rotation speed of 3000-6000 rpm and 25°C.

[0071] 3) Anti-adsorption

[0072] Take 10.00g of the treated oil sand and add it to a 150mL stoppered ground-mouth conical flask, then add 90g of a temperature-resistant and anti-adsorption middle phase microemulsion aqueous solution with a mass concentration of 0.01%, place the conical flask in a water bath constant temperature shaking box, shake it at a shaking frequency of 90 times / min for 24 hours, filter the clear liquid, test the absorbance of the clear liquid, and calculate the adsorption amount (unit: mg / g).

[0073] The middle phase microemulsions prepared in the above examples and comparative examples were subjected to the above performance tests, and the results are shown in Table 1 below.

[0074] Table 1

[0075]

[0076] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0077] From the test results of Examples 1 to 5 and Comparative Example 1, it can be found that when the anionic nonionic surfactant of the present invention is used, the surfactant includes the surfactant APEG-LY-SSS, the prepared middle phase microemulsion has excellent anti-adsorption performance, strong temperature resistance and salt resistance.

[0078] From the test results of Examples 1 to 5 and Comparative Examples 2 and 3, it can be found that when the technical scheme of the present invention is adopted, when the weight ratio of surfactant APEG-LY-SSS to sodium fatty alcohol polyoxyethylene ether sulfonate is 1:(1 to 10) by weight percentage, the prepared middle phase microemulsion has excellent anti-adsorption performance, strong temperature resistance and salt resistance.

[0079] From the test results of Examples 1 to 5 and Comparative Examples 4 and 5, it can be found that when the components in the middle phase microemulsion of the present invention contain 0.5 to 4.5 wt % of a surfactant, the temperature resistance, salt resistance and anti-adsorption performance of the middle phase microemulsion are relatively strong, while when the content of the surfactant component in the middle phase microemulsion is higher than the upper limit value of the present invention or lower than the lower limit value of the present invention, the anti-adsorption and temperature resistance effects of the middle phase microemulsion are relatively poor.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A medium phase microemulsion, characterized in that: The middle phase microemulsion includes a surfactant, a surfactant adjuvant, an inorganic salt, crude oil and water; wherein the surfactant is an anionic nonionic surfactant, and the surfactant includes a surfactant APEG-LY-SSS, and its structural formula is: Among them, 5≤x≤15, 2≤y≤20, 4≤z≤10, R1 is H or CH3, and R2 is a C2~C18 alkyl, hydroxyethyl, hydroxypropyl or methoxy group.

2. The middle phase microemulsion according to claim 1, characterized in that In addition to the surfactant APEG-LY-SSS, the surfactant also includes one or more of sodium fatty alcohol polyoxyethylene ether sulfonate, sodium lauryl sulfate, sodium alkyl diphenyl ether disulfonate or petroleum sulfonate, and is further preferably sodium fatty alcohol polyoxyethylene ether sulfonate; Preferably, in terms of weight percentage, the weight ratio of the surfactant APEG-LY-SSS to the sodium fatty alcohol polyoxyethylene ether sulfonate is 1:(1-10).

3. The middle phase microemulsion according to claim 1 or 2, characterized in that: In terms of weight percentage, the components of the middle phase microemulsion include 0.5-4.5wt% of the surfactant, 1.5-6.5wt% of the surfactant adjuvant, 0.5-4.0wt% of the inorganic salt, 85.0-97.5wt% of the crude oil and the balance of water.

4. The medium phase microemulsion according to any one of claims 1 to 3, characterized in that The surfactant auxiliary agent is selected from alcohol solvents, preferably one or more of n-hexanol, n-butanol or n-pentanol; Preferably, the inorganic salt is sodium chloride and / or potassium chloride.

5. The medium phase microemulsion according to any one of claims 1 to 3, characterized in that The components of the middle phase microemulsion include 1.2-4.5 wt% of the surfactant, 2.5-5.5 wt% of the surfactant adjuvant, 0.5-2.5 wt% of the inorganic salt, 87.5-94.5 wt% of the crude oil and the balance of water; Preferably, the water is recycled sewage and / or tap water.

6. A method for preparing a medium-phase microemulsion according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Step S1, taking a surfactant adjuvant, an inorganic salt and water into a stoppered colorimetric tube and stirring them once to obtain a mixed solution; Step S2, adding a surfactant and crude oil to the mixed solution and stirring them twice to obtain the middle phase microemulsion.

7. The method for preparing the middle phase microemulsion according to claim 6, characterized in that: In terms of weight percentage, the weight ratio of the surfactant auxiliary agent, the inorganic salt and water is 1:(0.2-2.5):(30-70); Preferably, in terms of weight percentage, the weight ratio of the surfactant to the crude oil is (0.01-0.30):

1.

8. The method for preparing the middle phase microemulsion according to claim 6 or 7, characterized in that: The rotation speed of the primary stirring is 100-500 rpm, the primary stirring time is 0.1-1.0 h, and the primary stirring temperature is 20-50° C.

9. The method for preparing a medium phase microemulsion according to any one of claims 6 to 8, characterized in that: The secondary stirring has a rotation speed of 200-400 rpm, a secondary stirring time of 0.5-2.0 h, and a secondary stirring temperature of 20-50° C.

10. Use of the middle phase microemulsion according to any one of claims 1 to 5, or the middle phase microemulsion obtained by the preparation method of the middle phase microemulsion according to any one of claims 6 to 9 in the field of oil and gas field exploitation, deep water plugging and profile control, or tertiary oil recovery technology in oil fields.

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