Small-size high-viscosity microemulsion hydraulic drive integrated system and application

Abstract

The invention discloses a small-size high-viscosity microemulsion hydraulic drive integrated system and application. The small-size high-viscosity microemulsion hydraulic drive integrated system is prepared from the following components in percentage by weight: 1.75 to 5.85 percent of an amphiphilic polymer surfactant, 2.25 to 10.15 percent of a cosurfactant, 42.00 to 48.00 percent of water and 42.00 to 48.00 percent of oil. The preparation method of the amphiphilic high-molecular surfactant comprises the following steps: S1, preparing an organic acid aqueous solution of a polysaccharide compound, and adding short-chain alcohol; s2, adding an alcoholic solution of fatty aldehyde into the system; s3, adding a short-chain alcohol-water solution in which a reducing agent is dissolved into the system for multiple times; and S4, adding an alkali solution into the system until the pH value reaches 8-12. The synthetic raw materials of the microemulsion hydraulic drive integrated system are wide in source, are selected from shrimp shells, crab shells, wood and the like, and are green and environment-friendly; the size of the system is small, the system can smoothly enter pores of low-permeability and ultra-low-permeability oil reservoirs, the high-viscosity characteristic endows the system with excellent fracturing characteristic, shearing resistance and sand-carrying performance, the purpose of efficient displacement is achieved, and finally the improvement of the crude oil recovery rate of the low-permeability and ultra-low-permeability oil reservoirs is achieved.

Description

Technical Field

[0001] The present invention relates to a small-size high-viscosity microemulsion hydraulic drive integrated system and its application, belonging to the technical field of efficient oilfield exploitation. Background Art

[0002] China is rich in unconventional oil and gas resources with great potential. The efficient development of unconventional oil and gas is of great strategic significance for ensuring China's oil and gas security and optimizing the energy structure. However, the geological conditions of unconventional oil and gas are complex, and the physical properties of reservoirs are generally poor, which determines that fracturing is a necessary measure for industrial oil and gas exploitation. The "postnatal vulnerability" characteristic also puts forward strict reservoir protection requirements for the fracturing operation. Conventional water-based fracturing fluids have characteristics such as formation adsorption, incomplete gel breaking, high residue content, and difficult flowback, and are prone to cause blockage and pollution of porous media, fractures, and proppant-filled layers, resulting in a decline in permeability and poor exploitation effects after fracturing of oil and gas reservoirs, or even abnormal production. Therefore, it is urgent to study a reasonable development method for replenishing formation energy and improving recovery rate after fracturing development.

[0003] Currently, the fracturing-enhanced energy-drive integrated technology is considered an important technical means for the efficient development of unconventional oil reservoirs, and it needs to meet the requirements of the displacement-drive process of "small dosage, strong drag reduction, high oil drainage, and low damage". Displacement is a continuous energy-supplementing method. In particular, a chemical drive system with a size in the nanometer range can combine the displacement effect with the imbibition mechanism, effectively expand the microscopic swept volume of unconventional oil reservoirs, improve the oil displacement efficiency, and effectively reduce and resolve the risks of water flooding and injection failure. It is a better subsequent development method for unconventional oil reservoirs such as tight oil and shale oil. However, for tight oil reservoirs with complex geological conditions such as low permeability and extra-low permeability, the chemical drive systems that have been widely applied in conventional oil reservoirs have encountered serious challenges. For example, the losses such as adsorption, retention, and precipitation of surfactants during migration are relatively serious, greatly reducing the migration distance and oil displacement effect, making it impossible to effectively play the original technical advantages of the chemical drive system. Therefore, it is necessary to develop a new type of displacement-drive integrated system that can break through these limitations to meet the actual on-site application of unconventional oil reservoirs.

[0004] The emergence of microemulsions has brought new progress to the integrated pressure displacement technology for unconventional reservoirs. A microemulsion is a highly dispersed system that is isotropic, thermodynamically stable, transparent or translucent, and spontaneously formed by two immiscible liquids, namely the oil phase and the water phase, under the action of surfactants and co-surfactants. The particle size of microemulsions is generally 1 - 100 nm, with high surface activity, good solubilization and wetting capabilities. The formation and arrangement of internal micelles can significantly reduce the adsorption loss of surfactants. In addition, microemulsions also have good viscosity and imbibition functions, can break through the application limits of traditional chemical flooding in unconventional reservoirs, and are expected to become a substitute chemical flooding technology for realizing integrated pressure displacement. The results of indoor core imbibition experiments and field huff and puff tests have confirmed that microemulsions can effectively improve the imbibition recovery rate of ultra-low permeability - tight reservoirs, indicating that they have great development potential in the field of unconventional EOR.

[0005] Currently, anionic surfactants, non-ionic surfactants, etc. are mainly used to prepare microemulsions for oil displacement. A mixture of equimolar cationic and anionic surfactants can prepare alcohol-free microemulsions, reducing environmental problems. However, for sandstone reservoirs, due to the negatively charged rock surface, cationic surfactants are less used for oil displacement, and there are few relevant literatures in the oil and gas industry. Table 1 lists the viscosities and particle sizes of microemulsions for oil displacement reported in the literature. It can be found that the existing systems cannot simultaneously achieve both small particle size (≤10 nm) and high viscosity characteristics (≥50 mPa·s), and cannot meet the requirements of integrated pressure displacement applications in low-permeability, ultra-low permeability - tight oil reservoirs. How to enhance the viscosity characteristics (≥50 mPa·s) of microemulsions while maintaining the characteristics of small droplets (≤10 nm), increase their sweep volume in micro-nano pore throats, improve the penetration ability and displacement efficiency in micro-nano pore matrixes, is a major technical problem that urgently needs to be solved for realizing integrated pressure displacement in unconventional reservoirs.

[0006] Table 1 Particle Sizes and Viscosities of Microemulsion Systems for Oil Displacement Reported in the Literature

[0007]

[0008] The formation and phase transition process of microemulsions depend on the curvature energy (bending energy) of the surfactant oil-water interface film. Their phase behavior is affected by various factors. Important influencing factors include the molecular properties of surfactants, pressure, temperature, salinity, the application of co-surfactants or cosolvents, the water-oil ratio, pH, and the properties of oils. The viscosity of microemulsions can be controlled by the type of hydrocarbon, the type of surfactant, the concentration of electrolyte, the amount of water, and co-surfactants. Due to the rapid development of the surfactant industry, traditional surfactants can no longer meet the needs of people's research and applications. New amphiphilic molecules, especially polymeric surfactants, have become a current research hotspot due to their unique properties. Their unique solution aggregation behavior and rheological behavior make them have broad application prospects in industries such as oil and gas fracturing, profile control and water shutoff, pharmaceutical carriers, daily necessities, and water treatment. The self-assembly of amphiphilic polymeric surfactants is one of the important means to obtain highly ordered structures at the nanoscale through the "bottom-up" method. Using driving forces such as crystallization driving, electrostatic interaction, and crosslinking, one-dimensional or two-dimensional nano- and micro-scale self-assembled morphologies can be controllably grown as self-assembly building units. Therefore, upgrading the base material of the microemulsion for enhanced oil recovery from conventional surfactants to amphiphilic polymeric surfactants, synthesizing amphiphilic polymeric surfactants with controllable hydrophilic and lipophilic groups, and introducing them into the preparation of microemulsions is a key way to achieve the small-size characteristics of microemulsions while enhancing their viscosity characteristics and obtaining an integrated pressure-drive system for unconventional reservoirs. Summary of the Invention

[0009] The object of the present invention is to provide an integrated pressure-drive system of small-size and high-viscosity microemulsion. Its small-size characteristics (<10 nm) ensure that it can smoothly enter the pores of low-permeability and extra-low-permeability reservoirs. The high-viscosity characteristics (>50 mPa·s) ensure its good sand-carrying performance and fracturing characteristics. At the same time, this system has excellent regulation effects on oil-water and solid-liquid interfaces, strong wetting reversal ability, can effectively mobilize various types of residual oil in porous media, achieve the purpose of efficient displacement, and ultimately improve the crude oil recovery rate of low-permeability and extra-low-permeability reservoirs.

[0010] The integrated pressure-drive system of small-size and high-viscosity microemulsion provided by the present invention has the following mass percentage composition:

[0011] Amphiphilic polymeric surfactant 1.75% - 5.85%, co-surfactant 2.25% - 10.15%, water 42.00% - 48.00%, oil 42.00% - 48.00%.

[0012] Among them, the preparation method of the amphiphilic polymeric surfactant includes the following steps:

[0013] S1. Prepare an aqueous organic acid solution of a polysaccharide compound, add a short-chain alcohol, and stir to obtain a clear and transparent mixed system;

[0014] S2. Add an alcohol solution of fatty aldehyde to the said mixed system and stir.

[0015] S3. Add a short-chain alcohol-aqueous solution of reducing agent to the said mixed system obtained in step S2 in several portions (generally 3 to 5 times) and stir.

[0016] S4. Add an alkali solution to the said mixed system obtained in step S3 until the pH value reaches 8 to 12 to obtain the product.

[0017] In step S1, the mass ratio of the polysaccharide compound to the short-chain alcohol is 1:35 to 50.

[0018] In step S1, the polysaccharide compound is one of cyclodextrin, poly-D-glucosamine, N-acetylglucosamine, chitin, and cellulose.

[0019] The organic acid is one of tartaric acid, citric acid, acetic acid, salicylic acid, oxalic acid, and succinic acid.

[0020] The short-chain alcohol is one of ethanol, propanol, 1-propanol, 2-propanol, ethylene glycol, and glycerol.

[0021] In step S2, the fatty aldehyde is one of octanal, nonanal, decanal, undecanal, dodecanal, tridecanal, and myristaldehyde.

[0022] In step S2, the molar ratio of the polysaccharide compound to the fatty aldehyde is 1:0.005 - 0.25.

[0023] In step S3, the molar ratio of the polysaccharide compound to the reducing agent is 1:0.005 to 0.25.

[0024] In step S3, the reducing agent is one of LiAlH4, LiBH4, NaBH4, KBH4, and BH3.

[0025] In the short-chain alcohol-aqueous solution of the reducing agent in step S3, the volume ratio of the short-chain alcohol to water is 1:2 - 2:1.

[0026] In step S4, the alkali solution is one of sodium hydroxide solution, potassium hydroxide solution, ammonia water solution, sodium carbonate solution, and sodium bicarbonate solution.

[0027] In step S3, the time interval for adding the reducing agent is 2 to 4 hours, and continuous stirring is carried out for 24 to 48 hours after the last addition.

[0028] After step S4, the following post-treatment steps are included: filter, wash with ethanol and filter, repeat 3 - 5 times; then wash with deionized water and filter, repeat 3 - 5 times; finally, wash with ethanol once and filter out the product for drying.

[0029] The co-surfactant is one or a combination of two of isopropanol, triethylene glycol, isopropanol, n-butanol, n-pentanol, iso-pentanol, and n-hexanol;

[0030] The water is tap water;

[0031] The oil is one of turpentine, octyldodecanol, and white oil.

[0032] The particle size of the integrated system of the present invention is 7 - 9 nm, which can ensure its smooth entry into low-permeability and extra-low-permeability tight oil reservoirs; at 60 °C and a shear rate of 170 s -1 Under the condition of shearing for 3600 s, the viscosity remains basically unchanged within the shearing time range, and the viscosity value is maintained at 50 - 60 mPa·s, meeting the requirements for the viscosity of the clean fracturing fluid during the construction process.

[0033] The present invention also provides a preparation method for the integrated system, including the following steps: uniformly mixing the amphiphilic polymer surfactant, the oil, and the water, and then dropping the co-surfactant to obtain the integrated system.

[0034] Based on the integrated system, the present invention also provides a method for improving oil recovery, including the step of using the integrated system for oil recovery.

[0035] Aiming at the development bottleneck that the current microemulsions for oil displacement cannot simultaneously take into account the characteristics of small size and high viscosity, the present invention synthesizes a class of amphiphilic polymer surfactants through original use to prepare a microemulsion system that simultaneously has the characteristics of small size (particle size < 10 nm) and high viscosity (> 50 mPa·s).

[0036] The present invention has the following beneficial effects:

[0037] (1) The small-size and high-viscosity microemulsion pressure-driving integrated system of the present invention has a small-size characteristic that ensures it can smoothly enter the pores of low-permeability and extra-low-permeability oil reservoirs, has excellent oil-water and solid-liquid interface regulation effects, strong wetting reversal ability, can effectively mobilize various types of residual oil in porous media, and achieves the purpose of efficient displacement, ultimately realizing the improvement of the oil recovery rate of low-permeability and extra-low-permeability oil reservoirs.

[0038] (2) The high-viscosity characteristic of the small-size and high-viscosity microemulsion pressure-driving integrated system of the present invention can ensure that the system has excellent fracturing characteristics, including good shear resistance. At 60 °C and a shear rate of 170 s -1 Under the condition of shearing for 3600 s, the viscosity remains basically unchanged within the shearing time range, and the viscosity value is maintained at 50 - 60 mPa·s, meeting the viscosity requirements of the fracturing fluid used in oil fields.

[0039] (3) The small-size high-viscosity microemulsion hydraulic drive integrated system of the present invention has excellent proppant-carrying performance, and the settling velocity of different proppants in the fracturing fluid is 0.17mm·s -1 -0.71mm·s -1 , meeting the requirements of fracturing construction.

[0040] (4) The synthetic raw materials of the small-size high-viscosity microemulsion hydraulic drive integrated system of the present invention are widely sourced, taken from shrimp shells, crab shells, wood, etc., and have the characteristics of environmental friendliness, thus reducing the pollution and damage to the formation; there is no need for backflow after oil production operations, which can greatly reduce costs. Description of the Drawings

[0041] Figure 1 are the appearance photos of the middle-phase microemulsion in Examples 2, 4, and 6 of the present invention.

[0042] Figure 2 are the viscosities of the middle-phase microemulsion under the conditions of a shear rate of 170s -1 and shearing for 3600s in Examples 2, 4, and 6 of the present invention. Detailed Embodiments

[0043] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0044] Unless otherwise specified, the materials, reagents, etc. used in the following examples can all be obtained from commercial channels.

[0045] Example 1. Preparation of amphiphilic polymer surfactant

[0046] (1) Measure 2500 mL of deionized water with a graduated cylinder and place it in a beaker. Weigh 50.0 g of chitin and pour it into the beaker. Stir with a magnetic stirrer until it is completely wetted, and then add 2.86 mL of 0.10 mol / L acetic acid solution to the above beaker and stir for 3 days until the polysaccharide compound is completely dissolved;

[0047] (2) Add 2500 mL of ethanol to the beaker, mix evenly, and stir for 40 minutes until the mixed system is clear and transparent;

[0048] (3) Dissolve 1.42 g of dodecyl aldehyde in 50 mL of ethanol solution, and add it dropwise to the above reaction beaker and stir for 45 minutes;

[0049] (4) Dissolve 5.85 g of KBH4 in a mixed solution of 30 mL of water and 30 mL of ethanol, and add it to the above reaction beaker in three portions at intervals of 2 hours. After the last addition, continuously stir for 48 hours;

[0050] (5) Prepare 0.01 mol / L NaOH solution, drop it into the reaction beaker, and detect the pH of the solution in the beaker while dropping, requiring the pH to reach 8.

[0051] (6) Filter out the reaction product, wash it with 1000 mL of ethanol and filter, repeat 5 times; then wash it with 1000 mL of deionized water and filter, repeat 4 times; finally, wash it once with 1000 mL of ethanol and filter out the product. Place it in a container, first dry it with a hair dryer for about 24 hours, and then transfer it to a freeze dryer for drying to obtain the amphiphilic polymer surfactant.

[0052] Example 2. Preparation of a small-size high-viscosity microemulsion hydraulic fracturing and displacement integrated system

[0053] In terms of weight percentage, the raw material composition of the small-size high-viscosity microemulsion hydraulic fracturing and displacement integrated system is as follows:

[0054] The amphiphilic polymer surfactant synthesized in Example 1 is 2.25 wt%, the co-surfactant n-butanol is 5.75 wt%, tap water is 46.00 wt%, and white oil is 46.00 wt%.

[0055] The small-size high-viscosity microemulsion hydraulic fracturing and displacement integrated system in this example is prepared through the following steps:

[0056] Mix the amphiphilic polymer surfactant synthesized in Example 1 with the oil phase and the water phase evenly, and then add the co-surfactant dropwise until a middle-phase microemulsion with a clear and transparent appearance and a light blue color is obtained ( Figure 1 Figure a in the middle), and its particle size is 7 - 9 nm. At 60 °C and a shear rate of 170 s -1 Shear for 3600 s, the viscosity remains basically unchanged within the shear time range, and the viscosity value is maintained at about 50 mPa·s ( Figure 2 Curve a in the middle).

[0057] When the fracturing fluid enters the formation, it will successively experience the processes of filtration loss, soaking well and imbibition, and displacement. In the early stage of the experiment, the experimental core needs to be saturated with simulated oil: (1) Simulated filtration loss stage: Set the filtration loss flow rate of the fracturing fluid to 0.1 mL / min and the temperature to 60 °C, and record the change of filtration loss pressure in real time during the filtration loss process. (2) Simulated soaking well and imbibition stage: After the filtration loss is completed, close the valves on both sides of the clamp and let the filtrate stay in the core for a period of time to simulate soaking the well. (3) Simulated displacement stage: At the same temperature and flow rate, use the fracturing fluid breaker to displace in the reverse direction, and record the change of the hydrogen signal intensity and pressure inside the core in real time. Calculate the oil recovery rate according to the change of the hydrogen signal intensity inside the core.

[0058] Further analyze the final production degree of each working fluid system. The final displacement production degree of the small-size high-viscosity microemulsion hydraulic fracturing and displacement integrated system is 38.6%. The system of the present invention has the characteristic of "producing more" in improving the oil production degree in the pressure displacement development of ultra-low permeability oil reservoirs.

[0059] Example 3. Synthesis of Amphiphilic Polymer Surfactant

[0060] (1) Measure 3500 mL of deionized water with a graduated cylinder and place it in a beaker. Weigh 75.0 g of poly-D-glucosamine and pour it into the beaker. Stir with a magnetic stirrer until it is completely dissolved and wetted. Then add 3.25 mL of 0.10 mol / L oxalic acid solution to the above beaker and stir for 3 days until the chitosan is completely dissolved;

[0061] (2) Add 3500 mL of ethanol to the beaker, mix well, and stir for 40 minutes until the mixed system is clear and transparent;

[0062] (3) Dissolve 2.90 g of lauraldehyde in 50 mL of ethylene glycol solution, and add it dropwise to the above reaction beaker, stirring for 45 minutes;

[0063] (4) Dissolve 3.56 g of NaBH4 in a mixed solution of 50 mL of water and 25 mL of ethanol, and add it to the above reaction beaker in three portions at intervals of 2 hours. After the last addition, stir continuously for 48 hours;

[0064] (5) Prepare 0.01 mol / L Na2CO3 solution, and drop it into the reaction beaker while detecting the pH of the solution in the beaker. The required pH is 8.

[0065] (6) Filter out the reaction product, wash it with 1000 mL of ethanol and filter, repeat 4 times; then wash it with 1000 mL of deionized water and filter, repeat 3 times; finally, wash it once with 1000 mL of ethanol and filter out the product and place it in a container. First, dry it with a hair dryer for about 24 hours, and then transfer it to a freeze dryer for drying to obtain the amphiphilic polymer surfactant.

[0066] Example 4. Preparation of Small-Size High-Viscosity Microemulsion for Hydraulic Fracturing and Displacement Integrated System

[0067] The raw material composition of the small-size high-viscosity microemulsion for hydraulic fracturing and displacement integrated system by weight percentage:

[0068] 1.75 wt% of the amphiphilic polymer surfactant synthesized in Example 3, 3.75 wt% of co-surfactant n-butanol, 47.25 wt% of tap water, and 47.25 wt% of white oil.

[0069] The small-size high-viscosity microemulsion for hydraulic fracturing and displacement integrated system in this example is prepared by the following steps:

[0070] Mix the amphiphilic polymer surfactant synthesized in Example 3 with the oil phase and water phase evenly, and then add the co-surfactant dropwise until a middle-phase microemulsion with a clear and transparent appearance and a light blue color is obtained ( Figure 1 in Figure b of Medium), with a particle size of 7 - 9 nm, at 60 °C, a shear rate of 170 s -1Under the condition of shearing for 3600 s, the viscosity remains basically unchanged within the shearing time range, and the viscosity value is maintained at about 55 mPa·s( Figure 2 in curve b) of

[0071] According to the method in Example 2, the final recovery degree of each working fluid system was analyzed. The final displacement recovery degree of the small-size high-viscosity microemulsion hydraulic drive integrated system was 40.5%.

[0072] Example 5. Synthesis of amphiphilic polymer surfactant

[0073] (1) Measure 2000 mL of deionized water with a measuring cylinder and place it in a beaker. Weigh 40.0 g of poly-D-glucosamine and pour it into the beaker. Stir with a magnetic stirrer until it is completely dissolved and wetted. Then add 4.15 mL of 0.10 mol / L succinic acid to the above beaker and stir for 4 days until poly-D-glucosamine is completely dissolved;

[0074] (2) Add 2000 mL of ethylene glycol to the beaker, mix evenly, and stir for 60 minutes until the mixed system is clear and transparent;

[0075] (3) Dissolve 5.79 g of myristaldehyde in 60 mL of ethylene glycol solution, and add it dropwise to the above reaction beaker, stirring for 60 minutes;

[0076] (4) Dissolve 6.20 g of NaBH4 in a mixed solution of 60 mL of water and 60 mL of ethylene glycol, and add it to the above reaction beaker in three portions at intervals of 2 hours. After the last addition, stir continuously for 48 hours;

[0077] (5) Prepare 0.01 mol / L KOH solution, and drop it into the reaction beaker while detecting the pH of the solution in the beaker. The required pH is 10.

[0078] (6) Filter out the reaction product, wash it with 1000 mL of ethanol and filter, repeat 5 times; then wash it with 1000 mL of deionized water and filter, repeat 4 times; finally, wash it once with 1000 mL of ethanol and filter out the product and place it in a container. First, dry it with a hair dryer for about 24 hours, and then transfer it to a freeze dryer for drying to obtain the amphiphilic polymer surfactant.

[0079] Example 6. Preparation of small-size high-viscosity microemulsion hydraulic drive integrated system

[0080] In terms of weight percentage, the raw material composition of the small-size high-viscosity microemulsion hydraulic drive integrated system is as follows:

[0081] 1.80 wt% of the amphiphilic polymer surfactant synthesized in Example 5, 2.40 wt% of co-surfactant n-butanol, 47.90 wt% of tap water, and 47.90 wt% of white oil.

[0082] The small-size high-viscosity microemulsion hydraulic drive integrated system in this embodiment is prepared through the following steps:

[0083] Mix the amphiphilic polymer surfactant synthesized in Example 5 with the oil phase and the water phase evenly, and then add the co-surfactant dropwise until a middle-phase microemulsion with a clear and transparent appearance and a light blue color is obtained ( Figure 1 Figure c in -1 Figure c), with a particle size of 8-9 nm. At 60 °C and a shear rate of 170 s Figure 2 For 3600 s of shearing, the viscosity remains basically unchanged within the shearing time range, and the viscosity is maintained at about 58 mPa·s (

[0084] According to the method in Example 2, analyze the final recovery degree of each working fluid system. The final displacement and recovery degree of the small-size high-viscosity microemulsion hydraulic drive integrated system is 41.5%.

Claims

1. A small-size high-viscosity microemulsion hydraulic flooding integrated system, the mass percentage composition of which is as follows: Amphiphilic polymer surfactant 1.75%-5.85%, co-surfactant 2.25%-10.15%, water 42.00%-48.00%, oil 42.00%-48.00%.

2. The integrated system according to claim 1, characterized in that: The preparation method of the amphiphilic polymer surfactant comprises the following steps: S1. Prepare an organic acid aqueous solution of a polysaccharide compound, add a short-chain alcohol, and stir to obtain a clear and transparent mixed system; S2, adding an alcohol solution of fatty aldehyde to the mixed system and stirring; S3, adding a short-chain alcohol-water solution containing a reducing agent dissolved therein to the mixed system obtained in step S2 in multiple portions, and stirring; S4, adding an alkaline solution to the mixed system obtained in step S3 until the pH value reaches 8 to 12.

3. The integrated system according to claim 2, characterized in that: In step S1, the polysaccharide compound is one of cyclodextrin, poly-D-glucosamine, N-acetylglucosamine, chitin and cellulose; The organic acid is one of tartaric acid, citric acid, acetic acid, salicylic acid, oxalic acid and succinic acid; The short-chain alcohol is one of ethanol, propanol, 1-propanol, 2-propanol, ethylene glycol and glycerol.

4. The integrated system according to claim 2 or 3, characterized in that: In step S2, the fatty aldehyde is one of octanal, nonanal, decanal, undecanal, lauric aldehyde, tridecanal and myristic aldehyde; In step S3, the reducing agent is one of LiAlH4, LiBH4, NaBH4, KBH4 and BH3; In step S3, the reducing agent is a short-chain alcohol-water solution, and the volume ratio of the short-chain alcohol to water is 1:2-2:1; In step S4, the alkaline solution is one of sodium hydroxide solution, potassium hydroxide solution, ammonia solution, sodium carbonate solution and sodium bicarbonate solution.

5. The integrated system according to any one of claims 2 to 4, characterized in that: In step S3, the time interval for adding the reducing agent is 2 to 4 hours, and stirring is continued for 24 to 48 hours after the last addition; The following post-processing steps are included after step S4: washing with ethanol and filtering after filtering, repeating 3-5 times; then washing with deionized water and filtering, repeating 3-5 times; finally washing once with ethanol and filtering the product to dry.

6. The integrated system according to any one of claims 1 to 5, characterized in that: The co-surfactant is one or a combination of two of isopropyl alcohol, triethylene glycol, isopropyl alcohol, n-butyl alcohol, n-pentanol, isopentanol and n-hexanol; The water is tap water; The oil is one of turpentine, octyldodecanol and white oil.

7. The integrated system according to any one of claims 1 to 6, characterized in that: The particle size of the integrated system is 7-9 nm, and the shear rate is 170 s -1 The viscosity is 50-60 mPa·s under shearing conditions of 3600 s.

8. A method for preparing the integrated system according to any one of claims 1 to 7, comprising the steps of: uniformly mixing the amphiphilic polymer surfactant, the oil and the water, and then dropwise adding the co-surfactant.

9. Use of the integrated system according to any one of claims 1 to 7 in improving crude oil recovery.

10. The use according to claim 9, characterized in that: The integrated system is injected into the formation.

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