Composite oil-displacing agent capable of improving oil recovery efficiency and preparation method and application of composite oil-displacing agent

Abstract

The invention relates to a composite oil-displacing agent for improving oil recovery efficiency and a preparation method and application thereof, the composite oil-displacing agent is prepared from the following raw materials: a biological surfactant, a chemical surfactant, a biopolymer and water, and the biological surfactant comprises rhamnolipid, surfactin and lipopeptide. The oil-displacing agent provided by the invention improves the oil-displacing efficiency, enlarges the swept volume, improves the oil recovery efficiency, and provides a new technical approach for green deep potential tapping of oil reservoirs.

Description

Technical Field

[0001] The invention belongs to the field of oil recovery, and relates to a composite oil displacement agent for improving oil recovery efficiency, and a preparation method and application thereof. Background Art

[0002] The use of biological and chemical compounding is an emerging technology for oil field development in recent years. In the related technology, biological surfactants are compounded with chemical surfactants and chemical polymers (CN115232610A and CN109897621A) to achieve good results in improving oil recovery. However, the large-scale application of chemical agents injected into oil fields has increasingly polluted the environment, and it is necessary to conduct research on green, low-carbon, and environmentally friendly technologies for improving oil recovery.

[0003] Microbial Enhanced Oil Recovery (MEOR) technology usually uses microbial metabolism to produce surfactants to "dissolve" crude oil to enhance their microbial adsorption and bioavailability. Biosurfactants have unique environmental protection, strong biodegradability and adaptability to extreme environmental conditions (such as temperature, pH and salinity) to promote the emulsification of crude oil. In addition, biopolymers such as xanthan gum have good viscoelasticity, thermal stability and high salt resistance due to their stable two-dimensional spatial structure. Biosurfactants and biopolymers have the characteristics of low cost and environmental friendliness. Biosurfactants and biopolymers that can emulsify crude oil and expand the swept volume will gradually be applied to reservoir development. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a composite oil displacement agent for improving oil recovery efficiency and a preparation method and application thereof.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a composite oil displacing agent for improving oil recovery efficiency, wherein the raw materials for preparing the oil displacing agent include biological surfactants, chemical surfactants, biopolymers and water, and the biological surfactants include rhamnolipids, surfactants and lipopeptides.

[0007] Environmentally friendly biosurfactants and biopolymers are used, supplemented by a small amount of chemical surfactants to enhance the emulsification ability of the oil displacement agent. The three substances are compounded to form a composite oil displacement agent of new biochemical surfactants and biopolymers, providing a new generation of bio-oil recovery products for tertiary oil recovery technology, which can improve oil recovery efficiency and swept volume, and will further achieve cost reduction and efficiency improvement in oil extraction.

[0008] Biosurfactants and chemical surfactants work synergistically and are more densely arranged at the oil-water interface. Biopolymers have the properties of increasing viscosity and expanding the swept volume, reducing the oil-water mobility ratio, thereby achieving the purpose of improving the recovery efficiency of residual oil, providing a new technical approach for green deep potential tapping of oil reservoirs.

[0009] The present invention finds that rhamnolipid, surfactin and lipopeptide in the biosurfactant have a certain synergistic effect in the effect of emulsifying and degrading crude oil.

[0010] The rhamnolipid includes monorhamnolipid (structural formula: RhaC10C10), disrhamnolipid (structural formula: RhaRhaC10C10), and one or more rhamnolipids in the metabolites of Pseudomonas aeruginosa such as Pseudomonas aeruginosa WL-4 (CGMCC No. 24711), mixed in any proportion.

[0011] The lipopeptide includes a cyclic lipopeptide with a structural formula of N-GluLeuLeuValLeuAspLeu-C, a cyclic lipopeptide with a structural formula of N-GluLeuLeuVal(LeuAsp / AspLeu)Leu-C, and one or more combinations in any proportion of lipopeptides in the metabolites of Bacillus subtilis such as Bacillus subtilis WL-5 (CGMCC No. 24712).

[0012] The rhamnolipid and lipopeptide may be rhamnolipid and lipopeptide in the metabolites of Dietzia bacteria, such as Dietzia cercidiphylli ORF-0003 (CGMCC No. 16105).

[0013] Preferably, the raw materials for preparing the composite oil-displacing agent include, by weight, 2.5-7.5 parts of biological surfactants, 2.5-7.5 parts of chemical surfactants, 5-8 parts of biological polymers and water.

[0014] The mass fraction of the biosurfactant can be selected from 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, etc.; the mass fraction of the chemical surfactant can be selected from 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, etc.; the mass fraction of the biopolymer can be selected from 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be repeated here one by one.

[0015] When the raw materials for preparing the composite oil displacement agent are mixed in the above-mentioned specific proportion, the effect of emulsification and degradation of crude oil is best.

[0016] Preferably, the mass ratio of rhamnolipid, surfactin and lipopeptide in the biosurfactant is (2.5-7.5):(2.5-6.7):(2.5-6.7).

[0017] Among them, the specific point values ​​in (2.5-7.5) can be selected from 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, etc., and the specific point values ​​in (2.5-6.7) can be selected from 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.7, etc. Other specific point values ​​within the above numerical range can be selected, so they will not be listed here one by one.

[0018] Preferably, the chemical surfactant includes any one of Triton X-100, betaine or 3-(N,N-dimethylpalmitoylamino)propanesulfonate or a combination of at least two thereof.

[0019] Preferably, the chemical surfactant is a combination of Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate.

[0020] Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate among chemical surfactants have a certain synergistic effect in the emulsification and degradation of crude oil.

[0021] Preferably, the mass ratio of Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate is (3.3-7.5):(2.5-7.5):(3.3-5).

[0022] Among them, the specific point values ​​in (3.3-7.5) can be selected from 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, etc., among which the specific point values ​​in (2.5-7.5) can be selected from 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, etc., among which the specific point values ​​in (3.3-5) can be selected from 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, etc., and other specific point values ​​within the above numerical range can be selected, so they will not be listed one by one here.

[0023] Preferably, the biopolymer comprises xanthan gum and / or dextran.

[0024] Preferably, the biopolymer is a combination of xanthan gum and dextran.

[0025] Xanthan gum and dextran in biopolymers have a certain synergistic effect in the emulsification and degradation of crude oil.

[0026] Preferably, the mass ratio of xanthan gum to dextran in the biopolymer is (5-8):(5-6).

[0027] The specific point values ​​in (5-8) can be selected as 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8, etc., and the specific point values ​​in (5-6) can be selected as 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be listed here one by one.

[0028] In a second aspect, the present invention provides a method for preparing the composite oil displacement agent for improving oil recovery efficiency according to the first aspect, the preparation method comprising physically mixing a biological surfactant, a chemical surfactant, a biopolymer and water to obtain the composite oil displacement agent.

[0029] Preferably, the mixing temperature is 40-50°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, etc. Other specific point values ​​within the above numerical range can be selected, which will not be described here one by one.

[0030] In a third aspect, the present invention provides a use of the composite oil displacement agent for improving oil recovery efficiency according to the first aspect in oil production.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] Environmentally friendly biosurfactants and biopolymers are used, supplemented by a small amount of chemical surfactants to enhance the emulsification ability of the oil displacement agent. The three substances are compounded to form a composite oil displacement agent of new biochemical surfactants and biopolymers, providing a new generation of bio-oil recovery products for tertiary oil recovery technology, which can improve oil recovery efficiency and swept volume, and will further achieve cost reduction and efficiency improvement in oil extraction.

[0033] Biosurfactants and chemical surfactants work synergistically and are more densely arranged at the oil-water interface. Biopolymers have the properties of increasing viscosity and expanding the swept volume, reducing the oil-water mobility ratio, thereby achieving the purpose of improving the recovery efficiency of residual oil, providing a new technical approach for green deep potential tapping of oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram of the emulsification experiment of the biochemical surfactant combination system.

[0035] Figure 2 It is a structural model diagram of multi-media coexistence.

[0036] Figure 3 This is a graph showing how the center of mass of water, oil, betaine, xanthan gum and lipopeptide change over time.

[0037] Figure 4 It is a graph of the diffusion rates of water, oil, betaine, xanthan gum and lipopeptide.

[0038] Figure 5 It is the interaction curve of water, betaine, xanthan gum and lipopeptide with oil. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0040] The simulated formation water involved in the following content includes, by mass concentration, CaCl2 0.0789 g / L, MgCl2·6H2O 0.0341 g / L, Na2SO4 0.0136 g / L, Na2CO3 0.3595 g / L, NaHCO3 3.5824 g / L, NaCl 1.2139 g / L and water.

[0041] The sources of the functional ingredients contained in the products involved in the following embodiments and comparative examples are as follows (only the functional ingredients are reflected, and the necessary auxiliary ingredients contained in other commercially available raw materials are not repeated):

[0042] Rhamnolipid was purchased from Sigma-Aldrich under the trade name Rhamnolipid, product number R90;

[0043] Surfactin was purchased from MACKLIN with the trade name Surfactin, CAS number 24730-31-2;

[0044] Lipopeptide was purchased from MACKLIN under the trade name Lipopeptide (from Sodium Lipopeptide from Bacillus subtilis), CAS No. 171263-26-6;

[0045] Triton X-100 was purchased from Sigma-Aldrich Company under the trade name Triton TM X-100, product with CAS No. 9002-93-1;

[0046] Betaine was purchased from Sigma-Aldrich Company under the trade name of N-dodecyl-N,N-dimethyl-3-ammonium-1-propanesulfonate, CAS No. 14933-08-5;

[0047] Xanthan gum is purchased from Sigma-Aldrich with the trade name Xanthan, CAS No. 11138-66-2;

[0048] Dextran was purchased from Sigma-Aldrich with the trade name of Dextran (derived from Leuconostoc spp.) and CAS number 9004-54-0.

[0049] Example 1

[0050] The present embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 5 parts of biological surfactants, 5 parts of chemical surfactants, 6.5 parts of biopolymers and 83.5 parts of simulated formation water. The biological surfactants include rhamnolipids, surfactant and lipopeptides in a mass ratio of 5:4.5:4.5, the chemical surfactants include Triton X-100, betaine, and 3-(N,N-dimethylpalmitoylamino)propanesulfonate in a mass ratio of 5:5:4, and the biopolymers include xanthan gum and dextran in a mass ratio of 6.5:5.5.

[0051] The preparation method is as follows: mixing biological surfactant, chemical surfactant, biological polymer and simulated formation water at 45 DEG C to obtain the product.

[0052] Example 2

[0053] The present embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 2.5 parts of a biological surfactant, 2.5 parts of a chemical surfactant, 8 parts of a biopolymer and 87 parts of water. The biological surfactant includes rhamnolipid, surfactant and lipopeptide in a mass ratio of 2.5:6.5:6.5, the chemical surfactant includes Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate in a mass ratio of 3.3:2.5:5, and the biopolymer includes xanthan gum and dextran in a mass ratio of 5:6.

[0054] The preparation method thereof is as follows: mixing a biological surfactant, a chemical surfactant, a biological polymer and water at 50 DEG C to obtain the product.

[0055] Example 3

[0056] The present embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 7.5 parts of biological surfactants, 7.5 parts of chemical surfactants, 5 parts of biopolymers and 80 parts of simulated formation water. The biological surfactants include rhamnolipids, surfactant and lipopeptides in a mass ratio of 7.5:2.5:2.5, the chemical surfactants include Triton X-100, betaine, and 3-(N,N-dimethylpalmitoylamino)propanesulfonate in a mass ratio of 7.5:7.5:3.3, and the biopolymers include xanthan gum and dextran in a mass ratio of 8:5.

[0057] The preparation method is as follows: mixing biological surfactant, chemical surfactant, biological polymer and simulated formation water at 40 DEG C to obtain the product.

[0058] Example 4

[0059] This embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain Triton X-100, and its reduced mass is proportionally distributed to the mass of betaine and 3-(N,N-dimethylpalmitoylamino)propane sulfonate, while other components and contents remain unchanged.

[0060] The preparation method is as in Example 1.

[0061] Example 5

[0062] This embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain betaine, and its reduced mass is proportionally distributed to the mass of Triton X-100 and 3-(N,N-dimethylpalmitoylamino)propanesulfonate, while other components and contents remain unchanged.

[0063] The preparation method is as in Example 1.

[0064] Example 6

[0065] This embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain 3-(N,N-dimethylpalmitoylamino)propanesulfonate, and its reduced mass is proportionally distributed to the mass of Triton X-100 and betaine, while other components and contents remain unchanged.

[0066] The preparation method is as in Example 1.

[0067] Example 7

[0068] This embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is different from that of Embodiment 1 only in that it does not contain xanthan gum, and its reduced mass is distributed to the mass of glucan, while other components and contents remain unchanged.

[0069] The preparation method is as in Example 1.

[0070] Example 8

[0071] This embodiment provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is different from that of Embodiment 1 only in that it does not contain glucan, and its reduced mass is distributed to the mass of xanthan gum, while other components and contents remain unchanged.

[0072] The preparation method is as in Example 1.

[0073] Comparative Example 1

[0074] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain rhamnolipid, and its reduced mass is proportionally distributed to the mass of surfactin and lipopeptide, while other components and contents remain unchanged.

[0075] The preparation method is as in Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain surfactant, and its reduced mass is proportionally distributed to the mass of rhamnolipid and lipopeptide, while other components and contents remain unchanged.

[0078] The preparation method is as in Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent differs from Example 1 only in that it does not contain lipopeptide, and its reduced mass is proportionally distributed to the mass of rhamnolipid and surfactin, while other components and contents remain unchanged.

[0081] The preparation method is as in Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 0.13% lipopeptide, 0.07% betaine and the remainder simulated formation water.

[0084] The preparation method is as in Example 1.

[0085] Comparative Example 5

[0086] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 0.1% lipopeptide, 0.1% betaine and the remainder simulated formation water.

[0087] The preparation method is as in Example 1.

[0088] Comparative Example 6

[0089] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 0.07% lipopeptide, 0.13% betaine and the remainder simulated formation water.

[0090] The preparation method is as in Example 1.

[0091] Comparative Example 7

[0092] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 0.05% lipopeptide, 0.15% betaine and the remainder simulated formation water.

[0093] The preparation method is as in Example 1.

[0094] Comparative Example 8

[0095] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent is composed of 0.02% lipopeptide and the remainder simulated formation water.

[0096] The preparation method is as in Example 1.

[0097] Comparative Example 9

[0098] This comparative example provides a composite oil-displacing agent for improving oil recovery efficiency. The composite oil-displacing agent comprises 0.02% betaine and the remainder simulated formation water.

[0099] The preparation method is as in Example 1.

[0100] Test Example 1

[0101] Emulsification effect test

[0102] Take 10g of the composite oil-displacing agent solution of Examples 1-8 and Comparative Examples 1-9 respectively in a sample bottle, then add 10g of kerosene, and stir at 3000r / min for 1min using a homogenizer (FSH-2A). Then pour into an emulsification tube and let stand for 48h, observe the stratification phenomenon, and record the volume of the emulsion layer.

[0103] The results of comparative stratification are as follows Figure 1 The emulsion layer volume results are shown in Table 1.

[0104] Table 1

[0105] sample Emulsion volume (mL) Example 1 14.5 Example 2 14.1 Example 3 13.9 Example 4 13.3 Example 5 13.2 Example 6 13.1 Example 7 13.6 Example 8 13.5 Comparative Example 1 13.3 Comparative Example 2 13.3 Comparative Example 3 13.2 Comparative Example 4 9.5 Comparative Example 5 11 Comparative Example 6 11.2 Comparative Example 7 12 Comparative Example 8 2 Comparative Example 9 6.5

[0106] From the data in Table 1, it can be seen that the combined emulsification layer with lipopeptide as biological surfactant and betaine as chemical surfactant has the following effect: Figure 1 , the biological surfactant lipopeptide and the chemical surfactant betaine were combined in the ratio of 2:1, 1:1, 1:2 and 1:3 respectively. The volume of the emulsion layer was 4.75-6 times that of the case when the lipopeptide was used alone, and 1.5-2 times that of the case when the betaine was used alone. The co-addition of biological surfactants and chemical surfactants has a better emulsification effect. There is a certain synergistic effect between the rhamnolipid, surfactant and lipopeptide in the biological surfactant, a certain synergistic effect between the chemical surfactant Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino) propanesulfonate, and a certain synergistic effect between xanthan gum and dextran in the biopolymer.

[0107] Test Example 2

[0108] Establishment of fluid model after polymer flooding

[0109] The molecular dynamics simulation method was used to construct a theoretical model of displacement pores based on the highly dispersed characteristics of the remaining oil after polymer flooding in Daqing Oilfield. The coexistence state and fluid phase characteristics of multiple fluids such as biosurfactants, chemical surfactants, biopolymers, water phase, and oil phase in the formation were tested by combining experimental data and simulation technology. Based on the above screening results, a structural model of multi-media coexistence consistent with the actual reservoir conditions was established, and molecular simulation tests were performed on the interaction and oil displacement performance of the oil displacement composite system of biosurfactant-chemical surfactant-biopolymer combined with different combinations and mixing ratios. The structural model of multi-media coexistence is as follows: Figure 3 shown.

[0110] Test Example 3

[0111] The concentrations of betaine, xanthan gum and lipopeptide in the mixed displacement aqueous solution were set to 0.1%, 0.1% and 0.1%, respectively. An optimized multiphase model was constructed and crude oil displacement tests were carried out to clarify the molecular interaction rules and oil displacement performance of the composite displacement system under this combination and mixing ratio during the displacement process.

[0112] Depend on Figure 3 It can be seen that within the displacement time of 6000ps, the range of the center of mass of each phase in the system is Inside, Figure 4This is the diffusion rate curve of water, oil, betaine, xanthan gum and lipopeptide. The study found that the diffusion rates of water and betaine are the fastest, and the diffusion rate of xanthan gum is close to that of crude oil. The displacement test results show that the multiphase fluidity in the displacement system is better, the displacement phenomenon is obvious, and the recovery rate of crude oil in the actual reservoir can be improved.

[0113] Figure 5 This is the interaction curve between water, betaine, xanthan gum and lipopeptide and oil. The study found that the interaction between betaine, xanthan gum and water and crude oil is less than 100 kcal / mol, and the interaction value between lipopeptide and crude oil after equilibrium is 250 kcal / mol.

[0114] The research results show that after adding three kinds of biosurfactants, chemical surfactants and biopolymers, the interaction between the mixed solution and crude oil molecules increases, which plays a major role in the crude oil displacement process. Therefore, the mixed solution has an obvious displacement effect.

[0115] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a composite oil-displacing agent for improving oil recovery efficiency and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0116] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0117] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A composite oil displacement agent for improving oil recovery efficiency, characterized in that: The raw materials for preparing the oil-displacing agent include biological surfactants, chemical surfactants, biological polymers and water, and the biological surfactants include rhamnolipids, surfactants and lipopeptides.

2. The composite oil displacement agent for improving oil recovery efficiency according to claim 1, characterized in that: The raw materials for preparing the composite oil displacement agent include, by weight, 2.5-7.5 parts of biological surfactant, 2.5-7.5 parts of chemical surfactant, 5-8 parts of biological polymer and water.

3. The composite oil displacement agent for improving oil recovery efficiency according to claim 1 or 2, characterized in that: The mass ratio of rhamnolipid, surfactin and lipopeptide in the biosurfactant is (2.5-7.5):(2.5-6.7):(2.5-6.7).

4. The composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 3, characterized in that: The chemical surfactant includes any one of Triton X-100, betaine or 3-(N,N-dimethylpalmitoylamino)propanesulfonate or a combination of at least two thereof.

5. The composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 4, characterized in that: The chemical surfactant is a combination of Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate; Preferably, the mass ratio of Triton X-100, betaine and 3-(N,N-dimethylpalmitoylamino)propanesulfonate is (3.3-7.5):(2.5-7.5):(3.3-5).

6. The composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 5, characterized in that: The biopolymers include xanthan gum and / or dextran.

7. The composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 6, characterized in that: The biopolymer is a combination of xanthan gum and dextran; Preferably, the mass ratio of xanthan gum to dextran in the biopolymer is (5-8):(5-6).

8. The method for preparing a composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 7, characterized in that: The preparation method comprises physically mixing a biological surfactant, a chemical surfactant, a biological polymer and water to obtain the product.

9. The method for preparing the composite oil displacement agent for improving oil recovery efficiency according to claim 8, characterized in that: The mixing temperature is 40-50°C.

10. Use of the composite oil displacement agent for improving oil recovery efficiency according to any one of claims 1 to 7 in oil production.

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