CN111793178B

CN111793178B - Amphiphilic montmorillonite and preparation method and application thereof

Info

Publication number: CN111793178B
Application number: CN202010698786.4A
Authority: CN
Inventors: 张静; 张侃; 王耀国
Original assignee: Ningbo Fengcheng Advanced Energy Materials Research Institute
Current assignee: Ningbo Fengcheng Advanced Energy Materials Research Institute Co ltd
Priority date: 2020-07-20
Filing date: 2020-07-20
Publication date: 2022-07-15
Anticipated expiration: 2040-07-20
Also published as: CN111793178A

Abstract

The application discloses an amphiphilic montmorillonite and a preparation method and application thereof, wherein the method comprises the following steps: adding a hydrophobic monomer and a surfactant into a water dispersion liquid containing montmorillonite and a hydrophilic monomer to obtain an off-white mixed solution; and adding an initiator into the grey-white mixed solution to obtain a reaction solution, and carrying out free radical polymerization reaction on the reaction solution to obtain the amphiphilic montmorillonite. The method obtains the amphiphilic montmorillonite by a free radical micelle method, avoids using an organic solvent, reduces the cost, avoids the steps of demulsification, oil-water separation and the like, reduces the production difficulty, improves the product yield, and has amphiphilic performance, stable performance and controllable particle size.

Description

Amphiphilic montmorillonite and preparation method and application thereof

Technical Field

The application relates to amphiphilic montmorillonite and a preparation method and application thereof, belonging to the technical field of oil displacement.

Background

In recent two years, China continuously becomes the world with the largest import of crude oil. The development report of oil and gas industry at home and abroad in 2018 shows that the dependence of the Chinese crude oil on the external environment is as high as 69.8 percent. National oil and gas resource dynamic evaluation 2010: the geological resource amount of China petroleum is 1037 hundred million tons, low-permeability and heavy oil low-grade resources account for about 2/3 of total petroleum resource amount, the development difficulty is large, and the estimated technical recovery ratio of low-permeability and heavy oil exploitation is only 12-14%.

In the water injection and oil displacement development process, the oil deposit rock is hydrated, scaled and expanded (clay), so that oil deposit pore channels are fine, the permeability is low, water cannot be injected into the oil deposit, oil cannot be produced, and the recovery ratio is seriously influenced. The development of an efficient and environment-friendly oil displacement agent for three-extraction of petroleum is an urgent strategic demand for realizing national energy safety in China. The nano material has higher reactivity due to the surface effect and the quantum size effect of the nano material, the size of the nano material can be controlled by a preparation method, and the nano material is subjected to functional modification of different functional groups, so that different application requirements can be met.

The existing synthesis technology for nanometer material oil displacement mainly comprises two types, one is a physical method, and nanometer materials are compounded with certain stable dispersing agents (polymers, surfactant) and the like to displace oil; one method is to graft some hydrophilic and lipophilic chain segments onto the nanometer material by chemical grafting method, mainly through aqueous solution polymerization, inverse emulsion polymerization, and inverse suspension polymerization, to finally realize oil displacement.

Application number 201610731002.7 discloses a preparation method of a graphene nano oil displacement agent, which comprises the steps of mixing graphene oxide with a polymer and a reducing agent, rapidly stirring and uniformly mixing under a certain condition, and cooling and drying to obtain the graphene nano oil displacement agent. In the method, the graphene, the polymer and the reducing agent are only mixed and compounded for use, and the graphene, the polymer and the reducing agent are not combined together through chemical bonds or other modes, so that chromatographic separation is easy to occur.

Application number 201410818901.1 discloses a preparation method of a nano oil displacement agent with intelligent characteristics. The temperature sensitive polymer, the hydrophilic polymer and the hydrophobic polymer are grafted to the surface of the nano particle through covalent bonds to prepare the composite nano particle with the temperature sensitive characteristic. The whole synthesis process in the method is up to 10 hours, the process is long, the manufacturing cost is high, and the method is not suitable for industrial production.

Application No. 201710944456.7 discloses a nano-silica composite oil displacement agent and an oil displacement method, wherein straight-chain fatty acid alkanolamide, polyalkyl benzene sulfonate, tetrakis (hydroxymethyl) phosphonium sulfate, biquaternary ammonium salt, biological enzyme, nano-silica sol, a polysilicon nano-material, glucoside, alkyl glycoside and the like are compounded together for secondary oil recovery of a low-permeability oil reservoir. The method adopts a physical method to compound various substances into one block, is tedious in industrial production, and is easy to generate a chromatographic separation effect when being actually used in an oil field, so that the effect is poor.

The preparation of the nano oil displacement agent generally grafts the nano particles with the monomer with the oleophilic group, and usually needs a plurality of steps, complex process and harsh conditions. The prepared product needs demulsification and separation of an oil-water mixture, and the problems of low yield of the obtained product, poor separation effect, unstable performance, uncontrollable particle size, high production cost, high production difficulty and the like exist.

Disclosure of Invention

According to one aspect of the application, the method for preparing the amphiphilic montmorillonite is provided, the amphiphilic montmorillonite is obtained by a free radical micelle method, an organic solvent is not used, the cost is reduced, the steps of demulsification, oil-water separation and the like are avoided, the production difficulty is reduced, the product yield is improved, and the product has amphiphilic performance, stable performance and controllable particle size.

The preparation method of the amphiphilic montmorillonite at least comprises the following steps:

(1) adding a hydrophobic monomer and a surfactant into an aqueous dispersion containing montmorillonite and a hydrophilic monomer to obtain an off-white mixed solution;

(2) and adding an initiator into the grey white mixed solution to obtain a reaction solution, and carrying out free radical polymerization reaction on the reaction solution to obtain the amphiphilic montmorillonite.

Optionally, the particle size of the montmorillonite in the aqueous dispersion in the step (1) is 60-300 nm.

Optionally, the particle size of the montmorillonite in the aqueous dispersion in step (1) is 60nm, 200nm or 300 nm.

Optionally, in the step (1), the mass ratio of the hydrophilic monomer to the montmorillonite is 2: 20-2: 50;

optionally, the upper limit of the mass ratio of the hydrophilic monomer to the montmorillonite is selected from 2:50, 2: 45. 2: 40; the lower limit is selected from 2:20, 2:25, 2: 30.

preferably, the mass of the hydrophobic monomer is 1.15-4.35% of that of the hydrophilic monomer;

optionally, the mass of the hydrophobic monomer is selected from 4.35%, 4.15%, 4%, 1.3%, 1.2% of the upper mass percentage limit of the hydrophilic monomer; the lower limit is selected from 4.35%, 4.15%, 4%, 1.3%, 1.2%, 1.15%.

Preferably, the mass of the surfactant is 3-5% of the total mass of the hydrophilic monomer and the hydrophobic monomer;

preferably, the concentration of the montmorillonite in the reaction liquid is 500-2000 ppm.

Preferably, the hydrophilic monomer in step (1) is selected from at least one of acrylamide monomer, acrylic monomer and sulfonate monomer;

preferably, the acrylamide monomer is selected from at least one of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and N-isopropylacrylamide;

preferably, the acrylic monomer is selected from at least one of acrylic acid, sodium acrylate and methacrylic acid;

preferably, the sulfonate monomer is selected from at least one of sodium p-styrene sulfonate, sodium methallyl sulfonate and sodium allyl sulfonate;

preferably, the hydrophobic monomer is a long-chain monomer with a carbon chain length of C12-C18;

preferably, the long-chain monomer is selected from at least one of stearyl acrylate or sodium alpha-olefin sulfonate (AOS);

preferably, the surfactant is selected from at least one of Sodium Dodecyl Sulfate (SDS) or sodium dodecyl sulfate (SDBS).

Optionally, the initiator in the step (2) is a water-soluble initiator, and the water-soluble initiator is at least one of potassium persulfate and ammonium persulfate.

Optionally, the mass of the initiator in the step (2) is 0.5-1% of the mass of the hydrophilic monomer.

Alternatively, the specific conditions of the radical polymerization reaction in step (2) include:

the reaction temperature is 60-80 ℃;

the reaction time is 3-5 h.

Optionally, the aqueous dispersion containing montmorillonite and hydrophilic monomer in step (1) is prepared by the following method:

adding montmorillonite into water to obtain a mixed solution I;

dissolving a hydrophilic monomer in water to obtain a mixed solution II;

mixing the mixed solution I and the mixed solution II, and discharging oxygen to obtain the water dispersion containing the montmorillonite and the hydrophilic monomer;

optionally, by introducing N into a reactor containing mixed liquor I and mixed liquor II₂Exhausting;

preferably, montmorillonite with the particle size of 2-3um is added into water, and stirring is carried out for 15-60 min at 200-500 rpm, so as to obtain a mixed solution I.

Optionally, the content of montmorillonite in the mixed solution I is 0.001-0.003 g/mL.

Optionally, in step (2), the initiator is dissolved in water and N is introduced₂Or inert gas, and then adding into the white mixed solution.

In a specific embodiment, a preparation method of a novel nano oil displacement agent is provided, which comprises the following specific steps:

weighing a certain amount of montmorillonite in a 1L beaker, filling 900mL of water in the beaker, mechanically stirring at a certain rotating speed, and respectively stirring for different times to obtain montmorillonite dispersion liquids with the particle sizes of 60nm, 200nm and 300 nm;

preparing 80mL of hydrophilic monomer solution in the step (2): weighing a certain amount of hydrophilic monomer, dissolving the hydrophilic monomer in 80mL of deionized water, and magnetically stirring at 400r/s until the hydrophilic monomer is completely dissolved;

preparing 20mL of initiator solution in the step (3): weighing a certain amount of water-soluble initiator to dissolve in 20mL of deionized water;

step (4) putting the solution obtained in the step (1) and the step (2) into a clean two-mouth round-bottom flask with the volume of 2L, inserting a stirring paddle to seal the main bottle mouth, and introducing N from the side mouth₂Discharging oxygen for 30min, and sealing the side port with a thermometer with a plug after ventilation is finished;

step (5) adding hydrophobic monomer and surfactant into step (4) to feed N₂Fully dissolving in the solution (2);

step (6), opening the oil bath pan, and setting the temperature to be 60-80 ℃;

step (7) placing the mixed solution in the step (5) into an oil bath kettle in the step (6) for heating;

step (8) in the process of step (7), deoxidizing the initiator in step (3);

step (9) when the mixed solution in the step (7) is at the temperature of more than 45 ℃ of a right mouth thermometer (solution temperature) T, slowly adding the aerobic initiator in the step (8) into the mixed solution; after the initiator is added, the reaction is carried out for a period of time.

Diluting the synthesized material to 50ppm, testing the temperature resistance and salt tolerance stability of the material, and testing the particle size of the material;

and (11) diluting the synthesized materials with different particle sizes to 50ppm, and performing displacement experiments in 50mD, 200mD and 500mD cores respectively, wherein the oil displacement rate is more than 10%.

The relevant content in the technical scheme of the preparation method is explained as follows:

1. in the step (1), the content of montmorillonite is 1-2 g, the mechanical stirring speed is 200-500 rpm, and the stirring time is 15-60 min;

2. in the step (2), the hydrophilic monomer is acrylamide, acrylic acid, sulfonate and the like, and the mass ratio of the hydrophilic monomer to the montmorillonite is 2: 20-2: 50;

3. in the step (3), the initiator is one of potassium persulfate and ammonium persulfate, and the initiator accounts for 0.5-1% of the mass of the hydrophilic monomer;

4. in the step (4), the hydrophobic monomers are chain monomers such as octadecyl acrylate, AOS and the like, and the dosage of the hydrophobic monomers is 1.15-4.35% of that of the hydrophilic monomers; the surfactant is Sodium Dodecyl Sulfate (SDS), sodium dodecyl sulfate (SDBS) and the like, and the dosage of the surfactant is 3-5% of the total monomer;

5. in the step (9), the reaction time is 3-5 h.

In a second aspect of the present application, there is provided an amphiphilic montmorillonite prepared by the method of any one of the above.

In a third aspect of the application, an oil displacement agent is provided, which contains at least one of the amphiphilic montmorillonite prepared by the method in any one of the above.

The beneficial effects that this application can produce include:

1) the invention adopts a free radical micelle method to synthesize the amphiphilic montmorillonite of the nano/polymer composite material with controllable particle size, the method obtains grey-white mixed liquid by adding hydrophobic monomers and surfactants into transparent aqueous solution of the montmorillonite and the hydrophilic monomers, namely micelle is formed, and initiator is added for reaction after the micelle is formed, thereby obtaining the amphiphilic montmorillonite, avoiding using organic solvent, reducing the cost, avoiding the steps of emulsion breaking, oil-water separation and the like, and overcoming the complexity and high cost of the traditional hydrophobic chain segment grafting nano material method (organic phase, reversed phase suspension, reversed phase emulsion);

2) the invention has simple process and stable repeatability;

3) the synthesized modified nano material has high mineralization degree (19 w NaCl +1w CaCl) at high temperature (90℃)₂ 2H₂0) In the environment, the temperature resistance and the salt tolerance can be still maintained, and particle precipitation cannot occur; and the nano modified materials with different grain diameters have good oil displacement effect in the corresponding pore throat rock cores.

Drawings

FIG. 1 is an infrared spectrum of montmorillonite before modification in example 1.

FIG. 2 is an infrared spectrum of the modified amphiphilic montmorillonite provided in example 1.

FIG. 3 is a photograph of a dispersion of the modified amphiphilic montmorillonite provided in example 1.

FIG. 4 is a photograph of a dispersion of the modified amphiphilic montmorillonite provided in example 1 after standing for 30 days.

FIG. 5 is a graph showing the recovery of the modified amphiphilic montmorillonite-forming dispersion provided in example 1.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

Unless otherwise specified, the starting materials and catalysts in the examples of the present application were commercially available, wherein montmorillonite was obtained from 2-3um particle size montmorillonite available from NANOCOR, USA;

octadecyl acrylate was purchased from 4813-57-4, a brocade biologies company;

AOS is model 68439-57-6, available from Lossen chemical Co., Ltd, Linyi.

EXAMPLE 1 preparation of amphiphilic montmorillonites

Weighing 2g of montmorillonite in a 1L beaker, filling 900mL of water in the beaker, and mechanically stirring for 15min at 500 rotating speed to obtain montmorillonite dispersion liquid (mixed liquid I) with the particle size of 60 nm;

preparing 80mL of hydrophilic monomer solution (mixed solution II) in the step (2): weighing 30g (the mass ratio of the hydrophilic monomer acrylamide to the montmorillonite is 2: 30) of hydrophilic monomer acrylamide, dissolving the hydrophilic monomer acrylamide in 80mL of deionized water, and magnetically stirring the mixture at 400r/s until the hydrophilic monomer acrylamide is completely dissolved;

preparing 20mL of initiator solution in the step (3): weighing 0.3g of initiator potassium persulfate (1 percent of the mass of the hydrophilic monomer) to be dissolved in 20mL of deionized water;

step (4) putting the mixed liquor I obtained in the step (1) and the mixed liquor II obtained in the step (2) into a clean two-neck round-bottom flask with the volume of 2L, inserting a stirring paddle to seal a main bottle mouth, and introducing N from a side mouth₂Discharging oxygen for 30min, and sealing the side port with a thermometer with a plug after ventilation is finished;

step (5) adding 1.305g of stearyl acrylate serving as a hydrophobic monomer (4.35 percent of the mass of the hydrophilic monomer) and 1.57g of sodium dodecyl benzene sulfonate serving as a surfactant (5 percent of the total mass of the hydrophilic monomer and the hydrophobic monomer) into the step (4) to feed N₂Fully dissolving the mixture in the solution to obtain a reaction solution;

step (6), opening the oil bath pan, and setting the temperature to be 70 ℃;

step (7), placing the reaction liquid obtained in the step (5) into the oil bath kettle in the step (6) for heating;

step (8) in the process of step (7), deoxidizing the initiator solution in step (3);

step (9) when the reaction solution in the step (7) is at the temperature of more than 45 ℃ of a right port thermometer (solution temperature) T, slowly adding the aerobic initiator solution in the step (8) into the reaction solution; and (3) reacting for 3 hours after the self-initiator is added, filtering and drying to obtain the amphiphilic montmorillonite.

Example 2

The preparation method is the same as that of the embodiment 1, the only difference is that the montmorillonite dispersion liquid with the particle size of 200nm is obtained by mechanically stirring the montmorillonite for 30min at the rotating speed of 400 in the step (1).

Example 3

The preparation method is the same as that of the embodiment 1, and the only difference is that the montmorillonite dispersion liquid with the grain diameter of 300nm is obtained by mechanically stirring the montmorillonite for 60min at the rotating speed of 250 in the step (1).

Example 4

The same procedure as in example 1 was followed, except that in step (5) the hydrophobic monomer was replaced by octadecyl acrylate instead of AOS.

The parent montmorillonites provided in the examples were characterized:

the infrared spectrum measurement was performed on the montmorillonite before modification and the amphiphilic montmorillonite obtained by modification in example 1, and the results are shown in fig. 1 and 2. As can be seen from FIG. 1, for the montmorillonite before modification, it was 1000.38 cm^-1The position is the stretching vibration peak of Si-O in the montmorillonite. As shown in FIG. 2, the characteristic absorption peak of Si-O disappears in the amphiphilic montmorillonite compared with that of montmorillonite, and-NH with hydrophilicity is generated₂cm^-1Characteristic absorption peak and hydrophobic-CH₂cm^-1Characteristic absorption peak, which proves that hydrophilic and hydrophobic monomers and montmorillonite are subjected to in-situ polymerization reaction and are coated.

The amphiphilic montmorillonites provided in the other examples also have the same or similar characteristics, which proves that the amphiphilic montmorillonites are obtained.

Dispersing the amphiphilic montmorillonite provided in the embodiments 1 to 4 in water to obtain an aqueous dispersion with the amphiphilic montmorillonite content of 50ppm, and performing particle size test by using a particle size tester of a Markov Zetasizer Nano ZSE model, UK, wherein the particle size of the amphiphilic montmorillonite obtained in the embodiment 1 is 60.5nm, the particle size of the amphiphilic montmorillonite obtained in the embodiment 2 is 195.5nm, and the particle size of the amphiphilic montmorillonite obtained in the embodiment 3 is 298.0 nm.

The performance test of the amphiphilic montmorillonite provided by each embodiment is carried out:

(1) contact angle test:

the amphiphilic montmorillonoid prepared in examples 1 to 4 and the commercially available montmorillonoid before being modified were dispersed with deionized water, dropped on a glass slide, oven-dried, and then subjected to contact angle test of water and oil using a contact angle measuring instrument model JC2000DM, the test results are shown in table 1, wherein the reagent used for measuring the contact angle with oil was n-hexadecane.

Table 1 contact angle test results

	Water contact Angle (°)	Oil contact Angle (°)
			Montmorillonite (before modification)	95	70
Example 1 provides amphiphilic montmorillonites	55	25
			Example 2 amphiphilic montmorillonites	60	28
Example 3 amphiphilic montmorillonites provided	75	35
			Example 4 provides amphiphilic montmorillonites	72	33

As can be seen from the table, the water contact angle and the oil contact angle of the unmodified montmorillonite are respectively 95 degrees and 70 degrees, which indicates that the unmodified montmorillonite has weak hydrophilicity and strong lipophilicity. The water contact angle of the modified amphiphilic montmorillonite is reduced to 55-75 degrees, and the oil contact angle is reduced by 25-35 degrees. The modified amphiphilic montmorillonite has good hydrophilicity and lipophilicity, and further proves that the montmorillonite is successfully grafted by hydrophilic and hydrophobic monomers.

(2) And (3) testing the dispersibility:

respectively dispersing the amphiphilic montmorillonite prepared in the embodiments 1-4 in high-salinity water at 90 ℃, and observing the phenomenon, wherein the high-salinity water comprises 19w NaCl +1w CaCl₂ 2H₂O, wherein "19 w NaCl" means that the concentration of NaCl in said hypersalinity water is 190000ppm and "1 w CaCl₂ 2H₂O' refers to CaCl in the water with high mineralization degree₂ 2H₂The concentration of O is 10000ppm, and the content of amphiphilic montmorillonite in hypersalinity water is 50 ppm.

As shown in FIGS. 3 and 4, after 30 days of standing, the amphiphilic montmorillonite dispersions provided in examples 1 to 4 did not precipitate, and were still uniformly dispersed. The amphiphilic montmorillonite is proved to have good dispersibility in water with high mineralization degree at high temperature.

(3) Testing the oil displacement effect:

respectively carrying out oil displacement tests on cores with different holes or roars by using the amphiphilic montmorillonite prepared in the embodiments 1-4, wherein the embodiment 1 corresponds to a 50mD core, the embodiment 2 corresponds to a 200mD core, and the embodiment 3 corresponds to a 500mD core;

during testing, the amphiphilic montmorillonite provided by the embodiments 1-4 is dispersed in simulated formation water (the mineralization degree is 5000 ppm) to obtain an aqueous dispersion liquid with the amphiphilic montmorillonite content of 50 ppm; after the displacement equipment carries out the water flooding process, the obtained water dispersion is injected into the rock core at the speed of 0.3mL/min to carry out the agent flooding process. And recording the oil output in the experimental process every 10-20 min (determining a time interval according to the oil output), and calculating the sectional recovery ratio and the final agent flooding recovery ratio according to the oil output. Taking example 1 as a representative, as shown in fig. 5, the result of displacement of the amphiphilic montmorillonite provided in example 1 dispersed in simulated formation water shows that the efficiency of amphiphilic montmorillonite agent displacement (corresponding to the nano displacement segment in fig. 5) is > 10%. The oil displacement efficiency of the amphiphilic montmorillonite provided by the embodiments 2-3 can reach more than 10%.

Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

Claims

1. The preparation method of the amphiphilic montmorillonite is characterized by at least comprising the following steps:

(1) adding a hydrophobic monomer and a surfactant into a water dispersion liquid containing montmorillonite and a hydrophilic monomer to obtain an off-white mixed solution;

(2) adding an initiator into the grey-white mixed solution to obtain a reaction solution, carrying out free radical polymerization reaction on the reaction solution, filtering and drying to obtain amphiphilic montmorillonite;

the particle size of the montmorillonite in the water dispersion liquid in the step (1) is 60-300 nm;

the mass of the surfactant is 3-5% of the total mass of the hydrophilic monomer and the hydrophobic monomer;

in the step (1), the mass ratio of the hydrophilic monomer to the montmorillonite is 2: 20-2: 50;

the mass of the hydrophobic monomer is 1.15-4.35% of that of the hydrophilic monomer;

the hydrophilic monomer in the step (1) is selected from at least one of acrylamide monomers, acrylic monomers and sulfonate monomers;

the acrylamide monomer is selected from at least one of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and N-isopropylacrylamide;

the acrylic monomer is selected from at least one of acrylic acid, sodium acrylate and methacrylic acid;

the sulfonate monomer is selected from at least one of sodium p-styrene sulfonate, sodium methallyl sulfonate and sodium allyl sulfonate;

the hydrophobic monomer is a long-chain monomer with a carbon chain length of C12-C18;

the long-chain monomer is selected from at least one of octadecyl acrylate or alpha-olefin sodium sulfonate.

2. The preparation method of claim 1, wherein the concentration of the montmorillonite in the reaction solution is 500 to 2000 ppm.

3. The method according to claim 1, wherein the surfactant is at least one selected from sodium lauryl sulfate and sodium lauryl sulfate.

4. The method according to claim 1, wherein the initiator in step (2) is a water-soluble initiator selected from at least one of potassium persulfate and ammonium persulfate.

5. The method according to claim 1, wherein the mass of the initiator in the step (2) is 0.5 to 1% of the mass of the hydrophilic monomer.

6. The production method according to claim 1, wherein the specific conditions of the radical polymerization in the step (2) include:

the reaction temperature is 60-80 ℃;

the reaction time is 3-5 h.

7. The method according to claim 1, wherein the aqueous dispersion of montmorillonite and hydrophilic monomer in step (1) is prepared by:

adding montmorillonite into water to obtain a mixed solution I;

dissolving a hydrophilic monomer in water to obtain a mixed solution II;

and mixing the mixed solution I and the mixed solution II, and discharging oxygen to obtain the water dispersion containing the montmorillonite and the hydrophilic monomer.

8. The preparation method of claim 7, wherein montmorillonite with a particle size of 2-3um is added into water, and the mixture is stirred at 200-500 rpm for 15-60 min to obtain the mixed solution I.

9. An amphiphilic montmorillonite prepared by the process of any one of claims 1 to 8.

10. An oil-displacing agent characterized by containing at least one amphiphilic montmorillonite prepared by the method of any one of claims 1 to 8.