Biological nano imbibition oil displacement agent and preparation method thereof

Abstract

The invention relates to a biological nano imbibition oil-displacing agent and a preparation method thereof, and the biological nano imbibition oil-displacing agent comprises the following components in percentage by weight: 40-55wt% of dispersing agent; 20 to 35 wt% of first modified metal nanoparticles; 20 to 35 wt% of second modified metal nanoparticles; the dispersing agent is brevibacillus borsteri fermentation cell removal liquid; the first modified metal nanoparticles are biosurfactant modified metal nanoparticles; the second modified metal nanoparticles are plant extract modified bimetallic nanoparticles. The oil-displacing agent provided by the invention can reduce interfacial tension and capillary force, realizes the effect of efficiently stripping crude oil, and has important significance and economic value for the development efficiency of medium-low permeability reservoirs.

Description

Technical Field

[0001] The present invention belongs to the field of oil extraction, and in particular relates to a biological nano imbibition oil displacement agent and a preparation method thereof. Background Art

[0002] At present, some of the medium and low permeability reservoirs in offshore oilfields have fine pores and complex structures. When fluids flow through them, they are strongly affected by the phase interface, resulting in high injection pressure, low recovery rate, and poor development effect in this part of the reservoir. Currently, there is an overall phenomenon of "difficult to inject and difficult to produce", the degree of water drive utilization is low, the water drive recovery rate is less than 18%, and most of the crude oil remains in the reservoir, far lower than the recovery rate of 25% - 40% after water drive and chemical drive in medium and high permeability reservoirs. It can be seen that there is huge oil production potential in medium and low permeability reservoirs.

[0003] CN113527147A discloses a preparation method of an imbibition oil displacement agent with wettability, and CN114410286A discloses a temperature and salt resistant nano imbibition oil displacement agent and its preparation method and application. The imbibition oil displacement agents in the above patents are mainly composed of alkynediol polyoxyethylene ether surfactants. The introduction of conventional surfactants will affect the emulsification separation in the later stage of the produced fluid, reduce the demulsification efficiency of crude oil, resulting in difficult demulsification and dehydration of crude oil, and there are also problems of high raw material costs and environmental pollution. In view of the current water injection development status of medium and low permeability reservoirs in offshore oilfields, in order to improve the overall recovery rate of medium and low permeability reservoirs in the sea and achieve efficient development of oilfields, it is necessary to develop a new type of high-efficiency oil displacement imbibition agent. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a biological nano imbibition oil displacement agent and a preparation method thereof. This oil displacement agent can reduce the interfacial tension and capillary force, achieve the effect of efficiently stripping crude oil, and has important significance and economic value for the development efficiency of medium and low permeability reservoirs.

[0005] The first aspect of the present invention provides a biological nano imbibition oil displacement agent, and the components and percentage contents are as follows:

[0006] Dispersant, 40 - 55 wt%;

[0007] First modified metal nanoparticles, 20 - 35 wt%;

[0008] Second modified metal nanoparticles, 20 - 35 wt%.

[0009] Wherein, the dispersant is the cell-free fluid obtained by fermenting Brevibacillus borstelensis.

[0010] The first modified metal nanoparticles are biosurfactant-modified metal nanoparticles. The biosurfactant is at least one of rhamnolipid surfactant and lipopeptide surfactant. The metal nanoparticles are at least one of Ag, Cu, and Fe. The metal nanoparticles modified by the biosurfactant can exhibit higher surface activity, which helps to reduce the interfacial tension and capillary force and lower the structural separation pressure.

[0011] The second modified metal nanoparticles are plant extract-modified bimetallic nanoparticles. The plant extract is at least one of camphor leaf extract, camphor root extract, and camphor seed extract. The bimetal is at least one of Ag-Cu and Fe-Ni. Bimetallic nanoparticles have stronger metal activity than single metals. The bimetallic nanoparticles modified by the plant extract can have a higher ability to emulsify crude oil, thus achieving more efficient oil washing.

[0012] The displacing agent composed of a combination of a dispersant and two modified metal nanoparticles can penetrate into the tiny voids of medium and low permeability reservoirs, enter the nano-scale fine throats and micro throats, improve the reservoir wettability, communicate channels, reduce the adhesion work of crude oil on the rock surface, and improve the fluidity of crude oil, and can achieve the purposes of displacement, acidification, plugging removal, and injection enhancement.

[0013] The second aspect of the present invention is to provide a preparation method of the imbibition displacing agent, and the method includes the following steps:

[0014] (1) The preparation method of the cell-free fluid fermented by Brevibacillus borstelensis is as follows: a) First, prepare a basal medium: Mix 20 - 50 g of a certain amount of starch, 0.5 - 1 g of magnesium sulfate, 0.5 - 1 g of potassium chloride, 0.5 - 1 g of potassium dihydrogen phosphate, 0.15 - 0.3 mg of ferrous sulfate, 5.0 - 10 mg of manganese sulfate, 0.16 - 0.5 mg of copper sulfate, and 1000 - 2000 mL of distilled water evenly; b) Fermentation culture: Inoculate 2% - 5% (V / V) of the seed liquid, and the fermentation conditions are 30 - 40 °C, 100 - 150 rpm / min, and carry out constant temperature shaking culture for 48 - 96 h, and measure the surface tension of the fermented liquid after centrifugation to obtain the cell-free fluid fermented by Brevibacillus borstelensis.

[0015] (2) The preparation method of biosurfactant-modified metal nanoparticles is as follows: Select at least one of rhamnolipid surfactant and lipopeptide surfactant as the biosurfactant, and at least one of Ag, Cu, and Fe as the metal nanoparticles. Mix 20 - 50 mmol / L of the metal nanoparticle precursor solution and the biosurfactant in equal volume at a ratio of 1:1, adjust the pH of the mixed solution to 8 - 9, place the reactants in a constant temperature magnetic stirrer at 60 - 70 °C and react for 10 - 30 min. After the metal nanoparticle precursor solution and the biosurfactant solution are fully mixed, slowly add 1.0 - 1.5 mL of 20 mmol / L NaBH4 solution drop by drop and keep stirring. The reaction time is 1 - 2 h. Dry this liquid in an oven at 60 - 75 °C to obtain the biosurfactant-modified metal nanoparticles. The metal nanoparticle precursor solution is any one of AgNO3 solution, FeCl3 solution, and CuSO4 solution.

[0016] (3) The preparation method of plant extract-modified bimetallic nanoparticles is as follows: Select at least one of camphor leaf extract, camphor root extract, and camphor seed extract as the plant extract; and at least one of Ag-Cu and Fe-Ni as the bimetal. a) Preparation of the plant extract: Wash the camphor plant raw materials (at least one of camphor leaves, camphor roots, and camphor seeds) with deionized water, dry them at 60 °C for 24 hours until the plant raw materials are completely dry, then grind the plant raw materials into powder with a mortar or a traditional Chinese medicine grinder, and pass through a 60-mesh sieve to obtain a more uniform powder; then take 50 - 100 g of the powder and place it in 500 - 1000 mL of 65% ethanol solution (the ratio of material to liquid is 1:25 - 1:10), and perform ultrasonic extraction at 400 w for 10 - 30 min under the condition of normal temperature - 55 °C. The obtained solution is filtered under reduced pressure through a 0.22 μm filter membrane to obtain the plant extract solution. b) Add 30 - 50 mL of the plant extract solution to a 100 mL conical flask, and then add 0.5 mM of the first metal precursor solution and 0.5 mM of the second metal precursor solution with a volume ratio of 1:1 to the plant extract solution. After covering with a sealing film, place the reactants in a constant temperature water bath at 50 - 75 °C and react for 30 - 60 min. After filtering the reactants under reduced pressure through a microfiltration membrane, the obtained liquid is the bimetallic nanoparticle system. Dry this liquid in an oven at 60 - 75 °C, and then wash the powder three times with deionized water and dry it again to obtain the plant extract-modified bimetallic nanoparticles. The first metal precursor solution is AgNO3 solution, and the second metal precursor solution is CuSO4 solution. Or the first metal precursor solution is FeCl3 solution, and the second metal precursor solution is NiCl2 solution.

[0017] (4) A certain amount of 40-55 wt% of the fermented cell-free liquid of Brevibacillus Potssteine ​​is taken, placed in a magnetic stirrer for dissolution, and fully stirred (100 r / min) for 30-60 min to form a uniform stabilizer liquid; then 20-35 wt% of biosurfactant-modified metal nanoparticles and 20-35 wt% of plant extract-modified metal nanoparticles are added to the uniform stabilizer liquid, followed by high-speed stirring for 1-2 h to disperse the emulsion into a uniform mucus, and then allowed to stand for 2-4 h to obtain a bionano-infiltration oil displacement agent.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] 1. The dispersant for the decellularized liquid of the fermentation of Brevibacillus Potsdam provided by the present invention has strong surface activity, and the surface tension of the fermentation liquid of Brevibacillus Potsdam is lower than 30mN / m; it can disperse the nanoparticles well and effectively prevent the sedimentation and agglomeration of the nanoparticles;

[0020] 2. The biosurfactant-modified metal nanoparticles and plant-modified bimetallic metal nanoparticles provided by the present invention can avoid self-aggregation of the nanoparticles, ensure that the nanoparticles can smoothly enter the dense pore throats, and maintain the metal activity of the nanoparticles, thereby ensuring that the nanoparticles clean the crude oil on the rock surface during the flow process, displace the crude oil, and realize the efficient development of medium and low permeability oil reservoirs;

[0021] 3. The bionano-imbibition oil displacement agent of the present invention does not affect the emulsification separation and demulsification performance of crude oil in the later stage after biodegradation, thereby reducing the later operation cost;

[0022] 4. The bionano-imbibition oil displacement agent of the present invention has the advantages of being green and environmentally friendly and can reduce damage to oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram of the crude oil adhesion state in the core at different time periods in the bio-nano-imbibition experiment in Example 1.

[0024] Figure 2 T2 spectra of water flooding and bio-nano flooding of rock samples. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0026] Example 1

[0027] (1) The preparation method of the cell-free fluid fermented by Brevibacillus borstelensis (CGMCC9981) is as follows: a) First, prepare the basal medium: Mix 20 g of a certain amount of starch, 0.5 g of magnesium sulfate, 0.5 g of potassium chloride, 0.5 g of potassium dihydrogen phosphate, 0.15 mg of ferrous sulfate, 5.0 mg of manganese sulfate, 0.16 mg of copper sulfate, and 1000 mL of distilled water evenly; b) Fermentation culture: Inoculate 5% (V / V) of the seed liquid, and the fermentation conditions are 40 °C, 150 rpm / min, and constant temperature shaking culture for 96 h. Measure the surface tension of the fermented liquid after centrifugation to obtain the cell-free fluid fermented by Brevibacillus borstelensis.

[0028] (2) The preparation method of the biosurfactant-modified metal nanoparticles is as follows: Mix the 50 mmol / L AgNO3 solution and the rhamnolipid biosurfactant in equal volume at a ratio of 1:1 (100 mL:100 mL). Adjust the pH of the mixed solution to 9. Place the reactants in a constant temperature magnetic stirrer at 70 °C and react for 10 min. After the AgNO3 solution and the rhamnolipid biosurfactant solution are fully mixed, slowly add 1.5 mL of 20 mmol / L NaBH4 solution drop by drop and continuously stir. The reaction time is 1 h, and the solution turns brown, indicating the generation of Ag NPs. Dry the liquid in an oven at 60 °C to obtain the biosurfactant-modified metal nanoparticles BSNP.

[0029] (3) The preparation method of the plant extract-modified bimetallic nanoparticles is as follows: Select the plant extract as the camphor leaf extract; the bimetal is Ag-Cu. a) Preparation of the plant extract: Wash the small-leaved camphor leaves with deionized water and dry them at 60 °C for 24 h until the leaves are completely dry. Remove the leaf veins and grind the leaves into a uniform powder with a mortar, and pass through a 60-mesh sieve; Take 100 g of the powder and place it in 1000 mL of 65% ethanol solution (material-liquid ratio 1:10), and perform ultrasonic extraction at 55 °C with 400 w for 10 min. The obtained solution is filtered under reduced pressure through a 0.22 μm filter membrane to obtain a solution labeled as the camphor leaf extract. b) Add 50 mL of the camphor leaf extract to a 100 mL conical flask, and then add a 0.5 mM AgNO3 solution and a 0.5 mM CuSO4·5H2O solution with a volume ratio of 1:1 (25 mL:25 mL) to the plant extract. Cover it with a sealing film and place the reactants in a constant temperature water bath at 75 °C and react for 30 min. It can be observed that the color of the reactants is more brownish-green than before, indicating the synthesis of silver-copper bimetallic nanoparticles (Ag-Cu bimetallic nanoparticles, Ag-Cu BNPs). After the reactants are filtered under reduced pressure through a 0.45 μm filter membrane, the obtained liquid is a bimetallic nanoparticle system. Dry this liquid in an oven at 60 °C, and then rinse the powder with deionized water three times and dry it again to obtain Ag-Cu BNPs.

[0030] (4) Take 40 wt% of the cell-free liquid fermented by Brevibacillus borstelensis, place it on a magnetic stirrer to dissolve, stir thoroughly (100 r / min) for 30 min to form a uniform stabilizer liquid; then add 30 wt% of biosurfactant-modified metal nanoparticles and 30 wt% of plant extract-modified metal nanoparticles to the uniform stabilizer liquid, and then stir at high speed for 1 h to disperse the emulsion to form a uniform mucus, and let it stand for 2 h to obtain the bio-nano imbibition oil displacement agent.

[0031] Take the bio-nano imbibition oil displacement agent prepared in Example 1 and verify its application effect on improving oil recovery through a static imbibition oil drainage experiment, including the following steps:

[0032] Step 1: A laboratory artificial columnar homogeneous core with a size of Φ2.5 cm × 3 cm, a permeability of 10 mD, and a porosity of 20%. The top, bottom, and side surfaces of the core are not sealed; Experimental oil: The experimental use of simulated formation oil is prepared by mixing crude oil and kerosene at a volume ratio of 5:1, with a viscosity of 5.69 mPa·s at 27°C and a density of 0.837 g / cm 3 , and a viscosity of 1.78 mPa·s at 40°C; Simulated formation water (self-made, salinity 20018 mg / L);

[0033] Step 2: Place the core in a vacuum drying dish and evacuate it for 24 h. After saturating it with simulated formation water under vacuum, continue to soak it in water for more than 48 h. Weigh the water-wet weight of the core using a balance and calculate the original water saturation.

[0034] Step 3: Displace with simulated formation oil at a rate of 0.1 mL / min to establish the irreducible water saturation until the displacement of more than 2 PV of simulated oil ends the displacement, calculate the saturated oil volume V o (mL) and oil saturation, then place the core in simulated oil and age it for more than 48 h, and finally weigh the oil-wet weight of the core.

[0035] Step 4: Place the core and imbibition fluids with different concentrations (5, 10, 20, 40, 60 ppm) in an oven at the experimental temperature and preheat for 1 h.

[0036] Step 5: Then place the core in the Amott bottle used in the experiment, seal the edge of the Amott bottle with Vaseline, pour the imbibition fluid into the corresponding Amott bottle, and finally place the imbibition experiment device in the oven and let it stand.

[0037] Step 6: Record the relationship between the volume of oil in the graduated glass tube (with a graduation accuracy of 0.01 mL) above the Amott bottle and time. Before each measurement, shake the bottle to make the oil adsorbed on the core separate from the core as much as possible. Calculate the static imbibition oil recovery rate ER (%) of the core according to the volume of produced oil phase Vol (mL). Keep calculating until the amount of produced oil stops increasing, and then calculate the final recovery rate.

[0038] See Figure 1 As shown, during the experiment, oil beads gradually start to emerge on the surface of the core saturated with crude oil at the initial stage of imbibition oil displacement. As the experiment progresses, the oil beads gradually become larger and rounder until finally they separate from the core surface and float on the liquid surface. As the experimental time increases, the speed at which the oil beads seep out of the core and separate from the core surface first increases, and more and more oil is discharged under the action of capillary force. After 20 h, the speed at which the oil beads seep out of the core and separate from the core surface starts to slow down, and after 56 h, less crude oil is discharged from the core surface.

[0039] Carry out an imbibition oil displacement evaluation experiment at a temperature of 60 °C. The relevant parameters of the core and the experimental results are shown in Table 1.

[0040] Take the bio-nano imbibition oil displacement agent prepared in Example 1 and verify its application effect on improving the recovery rate through a dynamic imbibition oil displacement experiment, including the following steps:

[0041] Step 1: Process the core sample into a core column with a diameter of 2.5 cm and a length of 6.0 cm, and wash and dry the core.

[0042] Step 2: Prepare a simulated formation water with a salinity of 20000 mg / L and a CaCl2 type, and saturate the core sample with the simulated formation water at a constant speed of 0.02 mL / min. The injection volume is 1 - 2 PV.

[0043] Step 3: Put the standard oil sample into the magnet cavity, adjust the parameters of the nuclear magnetic resonance instrument, perform central frequency correction, and determine parameters such as pulse width and central frequency.

[0044] Step 4: After the core is evacuated, pressurize and saturate it with distilled water, place it in the instrument for nuclear magnetic resonance T2 testing, and invert the T2 relaxation time spectrum.

[0045] Step 5: Displace the distilled water in the core with an MnCl2 solution with a salinity of 50000 ppm and perform nuclear magnetic resonance T2 testing to observe whether a signal can be detected.

[0046] Step 6: Inject crude oil to displace at 0.5 mL / min to establish the irreducible water saturation, perform nuclear magnetic resonance T2 testing, and observe the signal intensity.

[0047] Step 7: Inject an MnCl2 solution with a salinity of 50000 ppm and the biosurfactant nano imbibition oil displacement agent of Example 1, conduct nuclear magnetic resonance T2 spectrum testing on the remaining oil state after core water flooding, and invert the T2 relaxation time spectrum.

[0048] See Figure 2 As shown, conduct nuclear magnetic resonance testing on the static imbibition process of the biosurfactant nano oil displacement system. From the results of the T2 spectrum, it can be seen that the envelope area of the imbibition T2 spectrum of the biosurfactant nano imbibition oil displacement agent of Example 1 significantly decreases, and the peak value of the remaining oil change is concentrated in the low pore distribution area, indicating that the biosurfactant nano imbibition oil displacement agent of Example 1 can effectively act on the crude oil in small pores.

[0049] Example 2

[0050] In this example, the preparation methods of the cell-free fermentation broth of Brevibacillus borstelensis (CGMCC9981), the biosurfactant-modified metal nanoparticles, and the plant extract-modified bimetallic nanoparticles are the same as those in Example 1.

[0051] Take 50 wt% of the cell-free fermentation broth of Brevibacillus borstelensis (CGMCC9981), place it in a magnetic stirrer to dissolve, stir well (100 r / min) for 60 min to form a uniform stabilizer liquid; then add 25 wt% of the biosurfactant-modified metal nanoparticles and 25 wt% of the plant extract-modified metal nanoparticles to the uniform stabilizer liquid, and then stir at high speed for 1.5 h to disperse the emulsion to form a uniform mucus, and let it stand for 3 h to obtain the biosurfactant nano imbibition oil displacement agent.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that the biosurfactant nano imbibition oil displacement agent in Example 1 does not contain the cell-free fermentation broth of Brevibacillus borstelensis (CGMCC9981), the biosurfactant-modified metal nanoparticles account for 50 wt% of the total mass of the biosurfactant nano imbibition oil displacement agent, and the plant extract-modified bimetallic nanoparticles account for 50 wt% of the total mass of the biosurfactant nano imbibition oil displacement agent. The results of the static imbibition oil drainage experiment are shown in Table 1.

[0054] Comparative Example 2

[0055] The difference from Example 1 is that the biosurfactant nano imbibition oil displacement agent in Example 1 does not contain the biosurfactant-modified metal nanoparticles, the cell-free fermentation broth of Brevibacillus borstelensis (CGMCC9981) accounts for 55 wt% of the total mass of the biosurfactant nano imbibition oil displacement agent, and the plant extract-modified bimetallic nanoparticles account for 45 wt% of the total mass of the biosurfactant nano imbibition oil displacement agent. The results of the static imbibition oil drainage experiment are shown in Table 1.

[0056] Comparative Example 3

[0057] The difference from Test Example 1 is that in Example 1, the bio-nano imbibition oil displacement agent does not contain plant extract-modified bimetallic nanoparticles. The fermentation cell-free fluid of Brevibacillus borstelensis (CGMCC 9981) accounts for 55 wt% of the total mass of the bio-nano imbibition oil displacement agent, and the biosurfactant-modified metal nanoparticles account for 45 wt% of the total mass of the bio-nano imbibition oil displacement agent. The results of the static imbibition oil displacement experiment are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] The results of the static imbibition oil displacement show that the bio-nano imbibition oil displacement agent of the present invention has excellent imbibition oil displacement effect.

[0062] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A biological nano-permeation oil displacement agent, the components and percentage contents are as follows: Dispersant, 40 - 55 wt%; First modified metal nanoparticles, 20 - 35 wt%; Second modified metal nanoparticles, 20 - 35 wt%; The dispersant is the cell-free fluid obtained by fermenting Brevibacillus borstelensis; The first modified metal nanoparticles are metal nanoparticles modified by biosurfactant. The biosurfactant is at least one of rhamnolipid surfactant and lipopeptide surfactant. The metal nanoparticles are at least one of Ag, Cu, and Fe; The second modified metal nanoparticles are bimetallic nanoparticles modified by plant extracts. The plant extracts are at least one of camphor leaf extract, camphor root extract, and camphor seed extract; The bimetal is at least one of Ag-Cu and Fe-Ni.

2. The bio-nano imbibition oil displacement agent according to claim 1, wherein The preparation method of the cell-free fluid obtained by fermenting Brevibacillus borstelensis is as follows: a) Prepare the basic medium: Mix 20 - 50 g of a certain amount of starch, 0.5 - 1 g of magnesium sulfate, 0.5 - 1 g of potassium chloride, 0.5 - 1 g of potassium dihydrogen phosphate, 0.15 - 0.3 mg of ferrous sulfate, 5.0 - 10 mg of manganese sulfate, 0.16 - 0.5 mg of copper sulfate, and 1000 - 2000 mL of distilled water evenly; b) Fermentation culture: Inoculate 2% - 5% (V / V) of the seed liquid, and the fermentation conditions are 30 - 40 °C, 100 - 150 rpm / min, and incubate at a constant temperature with shaking for 48 - 96 h. Measure the surface tension of the fermented liquid after centrifugation to obtain the cell-free fluid obtained by fermenting Brevibacillus borstelensis.

3. The bio-nano imbibition oil displacement agent according to claim 1, characterized in that, The preparation method of the metal nanoparticles modified by biosurfactant is as follows: Mix 20 - 50 mmol / L of the precursor solution of metal nanoparticles and the biosurfactant in an equal volume ratio of 1:1, adjust the pH of the mixed solution to 8 - 9, place the reactants in a constant temperature magnetic stirrer at 60 - 70 °C and react for 10 - 30 min. After the precursor solution of metal nanoparticles and the biosurfactant solution are fully mixed, slowly add the NaBH4 solution drop by drop and keep stirring. The reaction time is 1 - 2 h. Dry this liquid in an oven at 60 - 75 °C to obtain the metal nanoparticles modified by biosurfactant.

4. The bio-nano imbibition oil displacement agent according to claim 1, wherein The precursor solution of metal nanoparticles is AgNO3 solution, FeCl3 solution, or CuSO4 solution.

5. The bio-nano imbibition oil displacement agent according to claim 1, characterized in that, The preparation method of the bimetallic nanoparticles modified by plant extracts is as follows: a) Preparation of plant extracts: Wash the camphor plant raw materials with deionized water, dry them until the plant raw materials are completely dry, grind them into powder, and sieve them; Then place the powder in an ethanol solution, with a material-liquid ratio of 1:25 - 1:10, and perform ultrasonic extraction at room temperature - 55 °C for 10 - 30 min. The obtained solution is filtered under reduced pressure through a filter membrane to obtain the plant extract solution; b) adding a first metal precursor liquid and a second metal precursor liquid in a volume ratio of 1:1 to the plant extract solution, covering with a sealing film, placing the reactants in a constant temperature water bath at 50-75° C. for reaction for 30-60 minutes; filtering the reactants through a microfiltration membrane under reduced pressure to obtain a liquid that is a bimetallic nanoparticle system, drying the liquid in an oven at 60-75° C., then rinsing the powder with deionized water three times, and drying again to obtain bimetallic nanoparticles modified with plant extracts.

6. The bio-nano imbibition oil displacement agent according to claim 1, wherein, The first metal precursor liquid is AgNO3 solution, and the second metal precursor liquid is CuSO4 solution; or the first metal precursor liquid is FeCl3 solution, and the second metal precursor liquid is NiCl2 solution.

7. A preparation method of the biological nano imbibition oil displacement agent according to any one of claims 1 to 6, characterized in that, A certain amount of 40-55wt% of the fermented cell-free liquid of Brevibacillus Potssteine ​​is taken, placed in a magnetic stirrer for dissolution, and stirred fully to form a uniform dispersant liquid; then 20-35wt% of biosurfactant-modified metal nanoparticles and 20-35wt% of plant extract-modified metal nanoparticles are added to the uniform dispersant liquid, followed by high-speed stirring for 1-2 hours to disperse the emulsion to form a uniform mucus, and the mixture is allowed to stand for 2-4 hours to obtain a bionano-infiltration oil displacement agent.

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