A biological ternary composite oil displacement system and a preparation method thereof

Abstract

This invention belongs to the technical field of oil and gas field development and enhanced oil recovery, specifically relating to a bio-based ternary composite enhanced oil recovery system and its preparation method. The bio-based ternary composite enhanced oil recovery system of this invention, by weight, comprises: 800-2000 parts of biopolymer; 600-3000 parts of biosurfactant; 40-400 parts of bionanomaterials; and 200-800 parts of water. In the bio-based ternary composite enhanced oil recovery system provided by this invention, the composite enhanced oil recovery system of biopolymer, biosurfactant, and bionanomaterials fully leverages the synergistic effect of each component, demonstrating significant advantages in improving crude oil recovery and reducing environmental risks, and possessing good industrial application prospects and promotional value.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development and enhanced oil recovery technology, specifically relating to a biological ternary composite oil displacement system and its preparation method. Background Technology

[0002] As one of the most important energy sources today, efficient extraction technology for petroleum has always been a core research topic in the petroleum industry. With the large-scale development of conventional oil fields and the entry of oil reservoirs into the mid-to-late stages of extraction, crude oil extraction faces a series of problems such as declining recovery rates and increasing water cuts. There is an urgent need to develop efficient and environmentally friendly tertiary oil recovery technologies to improve crude oil recovery. Chemical flooding technology, as one of the important methods of tertiary oil recovery, has seen widespread attention given to technologies such as polymer flooding, surfactant flooding, and nanomaterial-assisted flooding.

[0003] Traditional chemical flooding systems mainly rely on petroleum-based polymers and synthetic surfactants. However, these chemicals suffer from poor biodegradability, high environmental toxicity, and limited resistance to high temperatures and salt concentrations, hindering green and sustainable oil extraction. Meanwhile, nanomaterials show promising potential in improving the stability and wettability of flooding systems, but their dispersibility and interfacial activity in high-salt, high-temperature reservoir environments still need improvement.

[0004] In recent years, bio-based materials have gradually become emerging materials in the oil extraction field due to their excellent biodegradability, environmental friendliness, and resource renewability. Biopolymers such as microbial extracellular polysaccharides, including xanthan gum and sodium alginate, possess excellent viscoelastic properties and solution stability, effectively improving the viscosity of displacement fluids and extending the advance time of the displacement front. Biosurfactants such as rhamnolipids and sophorolipids not only reduce the interfacial tension between oil and water but also possess good biocompatibility and interfacial activity. Bionanomaterials such as silver / copper nanomaterials and their composites help improve the transport efficiency and controlled release performance of the system in the reservoir's pore structure.

[0005] Currently, there is a lack of composite oil displacement systems that organically combine biopolymers, biosurfactants, and bionanomaterials to achieve synergistic effects. Such composite systems hold the promise of combining the advantages of each component to form a structurally stable, highly active, viscoelastically superior, and environmentally friendly green oil displacement system, particularly suitable for reservoir development under complex geological conditions such as high temperature and high salinity. Therefore, developing a biopolymer-biosurfactant-bionanomaterial composite oil displacement system and realizing its application in actual oil production processes has significant theoretical importance and broad application prospects. Summary of the Invention

[0006] To address the shortcomings of existing technologies, a biological ternary composite oil displacement system and its preparation method are provided.

[0007] Specifically, the present invention is achieved through the following technical solutions: A biological ternary composite oil displacement system, comprising, by weight: 800-2000 parts of biopolymer; 600-3000 parts of biosurfactant; 40-400 parts of bionanomaterial; and 200-800 parts of water.

[0008] In the aforementioned biological ternary composite oil displacement system, the biopolymer is a microbial extracellular polysaccharide; the biosurfactant is rhamnolipid; and the bionanomaterial is silver nanoparticles coated with rhamnolipid.

[0009] The preparation method of the above-mentioned biological ternary composite oil displacement system includes the following steps: S1: Disperse the bio-nanomaterials in deionized water according to the specified ratio and perform ultrasonic dispersion; S2: Add biopolymer and biosurfactant according to the ratio, stir, and obtain a bio-ternary composite oil displacement system.

[0010] The above-mentioned preparation method of the bio-based ternary composite oil displacement system, wherein the biopolymer is prepared by the following method: S11: Inoculate Pseudomonas aeruginosa into nutrient medium 1 and incubate at a constant temperature; S12: After the culture is completed, the fermentation broth is separated to remove cells, and the supernatant is obtained; S13: Ethanol is added to the supernatant, and the mixture is incubated to obtain a biopolymer precipitate; S14: Separate and dry to obtain biopolymer.

[0011] The preparation method of the above-mentioned biological ternary composite oil displacement system, wherein the nutrient culture medium 1 comprises: 15-30 g / L glucose; 5-15 g / L corn steep liquor powder; 0.8-1.5 g / L sodium nitrate; 0.1-0.5 g / L calcium magnesium nitrate; 1.5-4.0 g / L dipotassium hydrogen phosphate; and 2-10 mL / L vegetable oil.

[0012] In the preparation method of the above-mentioned biological ternary composite oil displacement system, the biosurfactant is prepared by the following method: S21: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S22: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S23: The biosurfactant in the supernatant is extracted by acid precipitation, and after washing and drying, the biosurfactant is obtained.

[0013] The above-mentioned preparation method of the biological ternary composite oil displacement system, wherein the bio-nanomaterial is prepared by the following method: S31: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S32: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S33: After adjusting the concentration of the supernatant to the critical micelle concentration, mix it with AgNO3 solution and heat and stir. S34: Centrifugation, washing, and freeze-drying yield bio-nanomaterials.

[0014] The preparation method of the above-mentioned biological ternary composite oil displacement system, wherein the nutrient culture medium 2 comprises: 15-30 g / L glucose, 1-5 g / L L-glutamate sodium, 1.5-4.0 g / L K2HPO4, 0.5-3.0 g / L KH2PO4, 0.1-0.5 g / L MgSO4·7H2O, 0.03-0.10 g / L FeSO4·7H2O, 0.01-0.07 g / L CaCl2·2H2O, and 5-10 g / L NaCl.

[0015] In the preparation method of the above-mentioned biological ternary composite oil displacement system, the Pseudomonas aeruginosa is selected from one of the strains CGMCC No. 1.10452, CGMCC No. 1.238 and CGMCC No. 1.858 preserved by the China General Microbiological Culture Collection Center, or the strain ATCC No. 15692 preserved by the American Center for Type Culture Collection.

[0016] A biological ternary composite oil displacement system is prepared using the above-mentioned preparation method for biological ternary composite oil displacement systems.

[0017] The technical solution of the present invention has the following beneficial effects: The bio-based ternary composite oil recovery system provided by this invention, which combines biopolymers, biosurfactants, and bionanomaterials, fully leverages the synergistic effects of each component, demonstrating significant advantages in improving oil recovery and reducing environmental risks. It has promising prospects for industrial application and is worthy of widespread adoption. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0019] Figure 1 This is a scanning electron microscope image of bio-based Ag nanoparticles; Figure 2 This is a microscopic displacement diagram of a biological ternary composite displacement system. Detailed Implementation

[0020] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0021] A biological ternary composite oil displacement system, comprising, by weight: 800-2000 parts of biopolymer; 600-3000 parts of biosurfactant; 40-400 parts of bionanomaterial; and 200-800 parts of water.

[0022] The bio-based ternary composite enhanced oil recovery system provided by this invention, comprising biopolymers, biosurfactants, and bionanomaterials, fully leverages the synergistic effects of each component, exhibiting significant technological and application advantages. Firstly, the system utilizes natural, renewable biopolymers and biosurfactants, possessing excellent environmental compatibility and biodegradability, overcoming the environmental pollution and degradation problems of traditional chemical enhanced oil recovery agents, aligning with the trend of green and low-carbon development. Secondly, the biopolymer imparts excellent viscoelasticity to the system, effectively increasing the viscosity of the oil recovery fluid, delaying water channeling, and enhancing displacement efficiency; the biosurfactant significantly reduces oil-water interfacial tension, promoting the emulsification and stripping of residual oil, and improving crude oil utilization. Furthermore, the introduced bionanomaterials possess a large specific surface area and good dispersion stability, further enhancing the system's fluidity control capabilities and interfacial interactions, improving microscopic wettability and capillary forces, and effectively overcoming the limitations of reservoir pore structure. This composite system maintains good stability and oil recovery performance even under complex geological conditions such as high temperature and high salinity, demonstrating broad adaptability and practicality.

[0023] Biopolymers In the bio-ternary composite oil displacement system of the present invention, the biopolymer endows the system with excellent viscoelasticity, effectively increases the viscosity of the oil displacement fluid, delays water channeling, and enhances the displacement efficiency.

[0024] In some preferred embodiments, the biopolymer is a microbial extracellular polysaccharide.

[0025] In some preferred embodiments, the biopolymer is prepared by the following method: S11: Inoculate Pseudomonas aeruginosa into nutrient medium 1 and incubate at a constant temperature; S12: After the culture is completed, the fermentation broth is separated to remove cells, and the supernatant is obtained; S13: Ethanol is added to the supernatant, and the mixture is incubated to obtain a biopolymer precipitate; S14: Separate and dry to obtain biopolymer.

[0026] Among them, the Pseudomonas aeruginosa ( Pseudomonas aeruginosa This invention has been publicly disclosed prior to the application date and is available to the public from such collections, such as the China General Microbiological Culture Collection Center (CGMCC No. 1.10452, CGMCC No. 1.238, or CGMCC No. 1.858) and the American Center for Type Culture Collection (ATCC No. 15692).

[0027] The nutrient culture medium 1 comprises: 15-30 g / L glucose; 5-15 g / L corn steep liquor powder; 0.8-1.5 g / L sodium nitrate; 0.1-0.5 g / L calcium magnesium nitrate; 1.5-4.0 g / L dipotassium hydrogen phosphate; and 2-10 mL / L vegetable oil. Adding vegetable oil to the culture medium promotes microbial fermentation.

[0028] More preferably, the biopolymer is prepared by the following method: S111: Pseudomonas aeruginosa was inoculated into nutrient medium 1 and cultured in a constant temperature shaker at 35-40℃ and 150-300 rpm for 60-96 h; S121: After the culture is completed, the collected fermented bacterial solution is centrifuged to remove cells. The centrifugation speed is 8000-12000 rpm and the time is 15-30 min. S131: Precipitate biopolymers by adding 2-5 times the volume of 99% ethanol to the cell-free supernatant and incubating the mixture at 15-20°C for 24-48 h. S141: Centrifuge the sample at 0-4℃ at 8000-10000 rpm for 15-30 min; discard the supernatant, resuspend the biopolymer-containing aggregates in 2-6 mL of deionized water, and dry the biopolymer at 50-80℃ for 18-36 h.

[0029] The amount of biopolymer produced is determined by dry weight and expressed in g / L culture.

[0030] Biosurfactants In the bio-ternary composite oil displacement system of the present invention, biosurfactants can significantly reduce the oil-water interfacial tension, promote the emulsification and stripping of residual oil, and improve the utilization rate of crude oil.

[0031] In some preferred embodiments, the biosurfactant is rhamnolipid.

[0032] In some preferred embodiments, the biosurfactant is prepared by the following method: S21: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S22: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S23: The biosurfactant in the supernatant is extracted by acid precipitation, and after washing and drying, the biosurfactant is obtained.

[0033] Among them, the Pseudomonas aeruginosa ( Pseudomonas aeruginosa This invention has been publicly disclosed prior to the application date and is available to the public from such collections, such as the China General Microbiological Culture Collection Center (CGMCC No. 1.10452, CGMCC No. 1.238, or CGMCC No. 1.858) and the American Center for Type Culture Collection (ATCC No. 15692).

[0034] The nutrient culture medium 2 comprises: 15-30 g / L glucose, 1-5 g / L L-glutamate sodium, 1.5-4.0 g / L K2HPO4, 0.5-3.0 g / L KH2PO4, 0.1-0.5 g / L MgSO4·7H2O, 0.03-0.10 g / L FeSO4·7H2O, 0.01-0.07 g / L CaCl2·2H2O, and 5-10 g / L NaCl.

[0035] More preferably, the biosurfactant is prepared by the following method: S211: Pseudomonas aeruginosa is inoculated into nutrient medium 2 for fermentation at a temperature of 35-40℃ and cultured in a constant temperature shaker at 150-300 rpm for 60-96 hours. S222: After centrifuging the supernatant at 8000-12000 rpm for 10-30 min, collect the supernatant containing biosurfactants; S233: Adjust the pH of the supernatant to 1-3 using 36-38% concentrated hydrochloric acid, let it stand overnight at 0-4℃, and collect the precipitate by centrifugation after the biosurfactant has precipitated out. Wash the precipitate with deionized water until neutral, and then dry the powder to obtain crude biosurfactant.

[0036] Bionanomaterials In the bio-ternary composite oil displacement system of the present invention, bio-nanomaterials have a large specific surface area and good dispersion stability, which can further enhance the system's fluidity regulation ability and interfacial interaction, improve micro-wetting and capillary force, and effectively overcome the limitations of reservoir pore structure.

[0037] In some preferred embodiments, such as Figure 1 As shown, the bio-nanomaterial is silver nanoparticles coated with rhamnolipid.

[0038] In some preferred embodiments, the bio-nanomaterials are prepared by the following methods: S31: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S32: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S33: After adjusting the concentration of the supernatant to the critical micelle concentration, mix it with AgNO3 solution and heat and stir. S34: Centrifugation, washing, and freeze-drying yield bio-nanomaterials.

[0039] Among them, the Pseudomonas aeruginosa ( Pseudomonas aeruginosa This invention has been publicly disclosed prior to the application date and is available to the public from such collections, such as the China General Microbiological Culture Collection Center (CGMCC No. 1.10452, CGMCC No. 1.238, or CGMCC No. 1.858) and the American Center for Type Culture Collection (ATCC No. 15692).

[0040] The nutrient medium 2 comprises: 15-30 g / L glucose, 1-5 g / L L-glutamate sodium, 1.5-4.0 g / L K2HPO4, 0.5-3.0 g / L KH2PO4, 0.1-0.5 g / L MgSO4·7H2O, 0.03-0.10 g / L FeSO4·7H2O, 0.01-0.07 g / L CaCl2·2H2O, and 5-10 g / L NaCl.

[0041] More preferably, the bio-nanomaterial is prepared by the following method: S311: Pseudomonas aeruginosa is inoculated into nutrient medium 2 for fermentation at a temperature of 35-40℃ and cultured in a constant temperature shaker at 150-300 rpm for 60-96 hours. S323: After centrifuging the supernatant at 8000-12000 rpm for 10-30 min, collect the supernatant containing biosurfactants; S333: Measure the critical micelle concentration (CMC) of the supernatant, at which silver nanoparticles are synthesized. Add 5-15 mL of 4-6 mM AgNO3 solution and 20-30 mL of CMC Pseudomonas aeruginosa fermentation supernatant to a conical flask, and bring the volume to 50 mL with deionized water. Stir magnetically at 60-90℃ for 5-10 h. When the solution color gradually changes from light green to light brown, it indicates the successful synthesis of silver nanoparticles. The surface plasmon resonance (SPR) band of the silver nanoparticles was detected by UV-Vis spectrophotometry, which confirms the successful synthesis of silver nanoparticles.

[0042] S344: The light brown solution was centrifuged at 8000-16000 rpm for 10-30 min and washed three times with anhydrous ethanol and deionized water respectively. The precipitate was redispersed in deionized water and then dehydrated using a vacuum freeze dryer to obtain silver nanoparticles.

[0043] On the other hand, the present invention also provides a method for preparing a biological ternary composite oil displacement system, comprising the following steps: S1: Disperse the bio-nanomaterials in deionized water according to the specified ratio and perform ultrasonic dispersion; S2: Add biopolymer and biosurfactant according to the ratio, stir, and obtain a bio-ternary composite oil displacement system.

[0044] In some preferred embodiments, the power of the ultrasound is 50-100 kW and the duration is 5-25 min.

[0045] The bio-nanomaterials, biopolymers, and biosurfactants mentioned herein are the same as those described in the bio-ternary composite oil displacement system provided in the first aspect of this invention, and this invention will not repeat them here.

[0046] Example The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0047] Example 1 First, the biopolymer was obtained. Specifically, *Pseudomonas aeruginosa* (CGMCC No. 1.858) was inoculated into a nutrient medium containing: 20 g / L glucose and 12 g / L corn steep liquor as carbon sources; 1.2 g / L sodium nitrate and 0.4 g / L calcium magnesium nitrate as nitrogen sources; and 2 g / L dipotassium hydrogen phosphate as phosphorus source. Adding 5 mL / L vegetable oil facilitated fermentation. The mixture was then cultured in a shaker at 37°C and 180 rpm for 72 h. After culture, the fermented broth was collected and separated (9400 rpm, 20 min) to remove cells. The biopolymer was then precipitated by adding twice the volume of 99% v / v ethanol to the cell-free supernatant and incubating the mixture at 20°C for 24 h. The sample was then separated (9400 rpm, 20 min, 4 °C), the supernatant was discarded, and the biopolymer-containing aggregates were resuspended in 2 mL of deionized water. The biopolymer was then dried at 60 °C for 24 h. The amount of biopolymer produced was determined by dry weight and expressed in g / L culture.

[0048] Then, the biosurfactant was obtained. The specific method was as follows: *Pseudomonas aeruginosa* (CGMCC No. 1.238) was inoculated into a nutrient medium containing 20 g / L glucose, 2 g / L L-glutamate, 3 g / L K₂HPO₄, 1 g / L KH₂PO₄, 0.5 g / L MgSO₄·7H₂O, 0.05 g / L FeSO₄·7H₂O, 0.05 g / L CaCl₂·2H₂O, and 5-10 g / L NaCl. Fermentation was carried out in the above nutrient medium at 37℃ and cultured on a constant-temperature shaker at 180 rpm for 72 h. The supernatant containing the biosurfactant was then collected after centrifugation at 8000 rpm for 10 min. The pH of the supernatant was adjusted to 2.0 using 37% concentrated hydrochloric acid, and the mixture was allowed to stand overnight at 4°C. After the biosurfactant rhamnolipid precipitated out, the precipitate was collected by centrifugation and washed with deionized water until neutral. The powder was then dried to obtain the crude biosurfactant.

[0049] Next, biosurfactants were used as stabilizers and reducing agents to synthesize bio-Ag nanoparticles. The specific method was as follows: *Pseudomonas aeruginosa* (accession number ATCC 15692) was activated, and a sterilized nutrient medium was prepared for use. The nutrient medium consisted of 20 g / L glucose, 2 g / L L-glutamate, 3 g / L K₂HPO₄, 1 g / L KH₂PO₄, 0.5 g / L MgSO₄·7H₂O, 0.05 g / L FeSO₄·7H₂O, 0.05 g / L CaCl₂·2H₂O, and 5-10 g / L NaCl. *Pseudomonas aeruginosa* was inoculated in a clean bench and cultured at 37°C in a shaker (180 rpm) for 72 h. After culture, the fermentation broth was centrifuged, filtered, and collected to obtain the *Pseudomonas aeruginosa* fermentation supernatant. The critical micelle concentration (CMC) of the supernatant was measured, and Ag nanoparticles were synthesized at this concentration. Specifically, 5 mL of 5 mM AgNO3 solution and 20 mL of Pseudomonas aeruginosa fermentation supernatant at the CMC concentration were added to an Erlenmeyer flask, and the volume was adjusted to 50 mL with deionized water. The mixture was magnetically stirred at 70 °C for 5 h. The solution color gradually changed from pale green to light brown. The light brown solution was centrifuged (12,000 rpm, 10 min) and washed three times with anhydrous ethanol and deionized water, respectively. The precipitate was redispersed in deionized water and then dehydrated using a vacuum freeze dryer to obtain biological Ag nanoparticles.

[0050] Finally, the bio-ternary composite oil displacement nanofluid (BNF) was synthesized. The specific method was as follows: 100 mg of bio-Ag nanoparticles were weighed and redispersed in 500 mL of deionized water for ultrasonic dispersion at 60 kW for 10 min. Then, 1200 mg of the crudely extracted biopolymer and 1500 mg of the biosurfactant were weighed and placed in the aqueous solution containing the Ag nanoparticles. After complete dissolution, the mixture was stirred until homogeneous, thus obtaining the bio-ternary composite oil displacement nanofluid (BNF).

[0051] Performance testing The preparation methods of the biopolymers, biosurfactants, and bioAg nanoparticles used in the following test examples are the same as those disclosed in Example 1.

[0052] Test Example 1 Quartz sand (50, 80, and 120 mesh in a 3:2:1 ratio) was packed into the sand-filled pipe and repeatedly compacted, with a ring pressure of 6 MPa. The displacement equipment was connected, and the airtightness of the device was checked. 3 PV was injected into the sand-filled pipe at a flow rate of 0.5 mL / min using a peristaltic pump to saturate it. The pressure difference across the sand-filled pipe was recorded, and the permeability was calculated to be approximately 310 mD using Darcy's formula. The core was fully saturated with crude oil until oil flowed continuously from the outlet, with a saturated crude oil volume of 22.5 mL. Secondary oil recovery was simulated using formation water displacement, achieving a waterflood recovery rate of 45.10%. Finally, a 1000 ppm biopolymer unary system was injected for displacement, achieving a biopolymer unary system recovery rate of 7.15% and an overall recovery rate of 52.25%.

[0053] Test Example 2 The sand-filled pipe was treated using the same method as in Test Example 1, resulting in a core permeability of approximately 310 mD and 22.7 mL of saturated crude oil. Secondary oil recovery was simulated using formation water displacement, achieving a waterflood recovery rate of 44.18%. Subsequently, a binary composite flooding system of 1000 ppm biopolymer + 1200 ppm biosurfactant was injected, resulting in a waterflood recovery rate of 44.18%, a binary composite flooding recovery rate of 12.68%, and an overall recovery rate of 56.86%.

[0054] Test Example 3 The sand-filled pipe was treated using the same method as in Test Example 1, resulting in a core permeability of approximately 310 mD and 22.7 mL of saturated crude oil. Secondary oil recovery was simulated using formation water displacement, achieving a waterflood recovery rate of 44.79%. Subsequently, a ternary composite oil displacement system consisting of 1000 ppm biopolymer, 1200 ppm biosurfactant, and 80 ppm bio-Ag nanoparticles was injected. This resulted in a waterflood recovery rate of 44.79%, a ternary composite oil displacement recovery rate of 19.53%, and an overall recovery rate of 64.32%. The enhanced oil recovery rates of each displacement system are shown in Table 1.

[0055] Table 1. Enhanced Oil Recovery Effects of Different Bio-enhanced Oil Recovery Systems

[0056] Test Example 4 The microscopic displacement laboratory experiment of the bio-ternary composite nano-enhanced oil recovery system included the following steps: A microfluidic chip simulating formation pores (made of hydrophilic silicate glass with a porosity of approximately 15-20%) was fabricated, and simulated oil was added to the chip to saturate it. At room temperature, simulated formation water (total salinity of 15000 mg / L, mainly composed of carbonates and chloride ions) was injected into the chip inlet at a rate of 1.5 mL / min to simulate a water-driven oil reservoir development environment. When the water cut at the chip outlet was ≥98%, the distribution of remaining oil was recorded. Subsequently, a bio-ternary composite nano-enhanced oil recovery system comprising 1500 ppm biopolymer, 2000 ppm biosurfactant, and 100 ppm bionanomaterials was injected into the chip inlet until the water cut at the chip outlet was ≥98%, and the distribution of remaining oil was recorded.

[0057] from Figure 2 It can be seen that the biological ternary composite nano-oil displacement system has the effects of emulsifying and washing oil and stripping oil droplets. The flake oil is dispersed through emulsification, and the number of island-shaped oil droplets increases, which improves the recovery rate.

[0058] Experimental results show that the bio-ternary composite oil recovery nanofluid can significantly improve the efficiency of tertiary oil recovery.

[0059] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0060] 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 describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A biological ternary composite oil displacement system, characterized in that, By weight, it includes: 800-2000 parts of biopolymer; 600-3000 parts of biosurfactant; 40-400 parts of bionanomaterial; and 200-800 parts of water.

2. The biological ternary composite oil displacement system according to claim 1, characterized in that, The biopolymer is a microbial extracellular polysaccharide; the biosurfactant is rhamnolipid; and the bionanomaterial is silver nanoparticles coated with rhamnolipid.

3. A method for preparing the bio-ternary composite oil displacement system according to claim 1 or 2, characterized in that, Includes the following steps: S1: Disperse the bio-nanomaterials in deionized water according to the specified ratio and perform ultrasonic dispersion; S2: Add biopolymer and biosurfactant according to the ratio, stir, and obtain a bio-ternary composite oil displacement system.

4. The preparation method according to claim 3, characterized in that, The biopolymer was prepared by the following method: S11: Inoculate Pseudomonas aeruginosa into nutrient medium 1 and incubate at a constant temperature; S12: After the culture is completed, the fermentation broth is separated to remove cells, and the supernatant is obtained; S13: Ethanol is added to the supernatant, and the mixture is incubated to obtain a biopolymer precipitate; S14: Separate and dry to obtain biopolymer.

5. The preparation method according to claim 4, characterized in that, The nutrient culture medium 1 comprises: 15-30 g / L glucose; 5-15 g / L corn steep liquor powder; 0.8-1.5 g / L sodium nitrate; 0.1-0.5 g / L calcium magnesium nitrate; 1.5-4.0 g / L dipotassium hydrogen phosphate; and 2-10 mL / L vegetable oil.

6. The preparation method according to claim 3, characterized in that, The biosurfactant was prepared by the following method: S21: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S22: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S23: The biosurfactant in the supernatant is extracted by acid precipitation, and after washing and drying, the biosurfactant is obtained.

7. The preparation method according to claim 3, characterized in that, The bio-nanomaterials were prepared by the following method: S31: Inoculate Pseudomonas aeruginosa into nutrient medium 2 and incubate at a constant temperature; S32: After the culture is completed, the fermentation broth is centrifuged and filtered to obtain a supernatant containing biosurfactants; S33: After adjusting the concentration of the supernatant to the critical micelle concentration, mix it with AgNO3 solution and heat and stir. S34: Centrifugation, washing, and freeze-drying yield bio-nanomaterials.

8. The preparation method according to claim 6 or 7, characterized in that, The nutrient medium 2 comprises: 15-30 g / L glucose, 1-5 g / L L-glutamate sodium, 1.5-4.0 g / L K2HPO4, 0.5-3.0 g / L KH2PO4, 0.1-0.5 g / L MgSO4·7H2O, 0.03-0.10 g / L FeSO4·7H2O, 0.01-0.07 g / L CaCl2·2H2O, and 5-10 g / L NaCl.

9. The preparation method according to any one of claims 4, 6-7, characterized in that, The *Pseudomonas aeruginosa* strain was selected from one of the strains CGMCC No. 1.10452, CGMCC No. 1.238, and CGMCC No. 1.858 preserved by the China General Microbiological Culture Collection Center, or strain ATCC No. 15692 preserved by the American Center for Type Culture Collection.

10. A biological ternary composite oil displacement system, characterized in that, It is prepared by the preparation method according to any one of claims 3-9.

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