High-salt-resistance composite cleanup additive and preparation method thereof

Abstract

The invention discloses a high-salt-resistance composite cleanup additive and a preparation method thereof, and relates to the technical field of oilfield chemical additives. The invention discloses a high-salt-resistance composite discharge aiding agent. The cleaning agent is prepared from the following raw materials in parts by weight: 10 to 20 parts of modified sodium dodecyl benzene sulfonate, 5 to 10 parts of cocamidopropyl betaine, 8 to 15 parts of polyoxyethylene ether, 2 to 5 parts of nano silicon dioxide, 3 to 8 parts of sodium hexametaphosphate, 1 to 3 parts of low-molecular-weight polyacrylamide, 4 to 10 parts of modified polyacrylic acid-acrylamide copolymer, 15 to 30 parts of ethanol and 5 to 12 parts of ethylene glycol butyl ether. 2-6 parts of an imidazoline derivative, 3-7 parts of amino trimethylene phosphonic acid, 4-9 parts of sodium silicate and 2-5 parts of citric acid-sodium citrate. Aiming at development requirements of high-salt oil reservoirs, sodium dodecyl benzene sulfonate and the polyacrylic acid-acrylamide copolymer are modified, and raw materials are scientifically compounded, so that the cleanup additive shows high stability in a high-salt environment, can reduce interfacial tension and effectively regulate and control rock surface wettability, has foam stability and biodegradability, and can be widely applied to high-salt oil reservoirs. The method is suitable for high-salt complex oil reservoir operation scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemical additives, and specifically to a high salt-resistant composite drainage aid and a preparation method thereof. Background Art

[0002] In the context of the continuous expansion of oilfield development into deep and complex formations, the efficient exploitation of high-salt reservoirs has become an important technical problem faced by the global oil and gas industry. Such reservoirs generally have the characteristics of extremely high formation water salinity and complex ion composition (such as rich in high-valent ions such as Na⁺, Ca²⁺, Mg²⁺, etc.), resulting in multiple performance shortcomings of conventional drainage aids in application:

[0003] First of all, the molecular structure of the traditional surfactant sodium dodecylbenzenesulfonate is easily affected by the charge shielding effect of high-salt ions, and its adsorption ability at the oil-water interface or on the rock surface decreases significantly, which in turn causes problems such as the recovery of interfacial tension and the failure of wettability regulation, resulting in the difficulty of effectively discharging the working fluid from the formation pores. Secondly, conventional polyacrylamide will curl, flocculate or even precipitate due to the compression of the double electric layer by salt ions in a high-salt environment, not only losing the functions of viscosity increase and dispersion, but also possibly blocking the pore throats, further aggravating formation damage. In addition, the high-salt formation water is prone to complex physical and chemical reactions with the components in the drainage aid. For example, calcium and magnesium ions react with anionic surfactants to form insoluble salts, and cooperate with clay minerals to cause swelling migration, etc., resulting in the overall compatibility deterioration of the drainage aid and forming a risk of "secondary blockage".

[0004] At the environmental protection level, traditional drainage aids mostly rely on petroleum-based raw materials and have poor biodegradability. After their residual components stay in the high-salt formation for a long time, they may cause potential pollution to the surrounding ecological environment through groundwater circulation, and it is difficult to meet the strict requirements of current oilfield development for green chemical additives. Although the existing technology attempts to improve the performance of drainage aids by means of introducing salt-resistant monomers for modification and compounding inorganic salt stabilizers, the optimization of single components is difficult to build a multi-dimensional and synergistic salt-resistant mechanism, and there are still defects such as limited salt-resistant threshold, short action time, and insufficient multi-functional integration in extremely high-salt (salinity > 200,000 mg / L) and high-temperature (> 120 °C) formations.

[0005] Therefore, the key to breaking through the traditional technical bottleneck lies in developing a new type of composite drainage aid that integrates "salt-resistant molecular design - multi-component synergy - environmentally friendly construction". Enhancing the salt ion tolerance ability of surfactants through molecular structure modification, realizing the synergistic effect of functions such as salt resistance, viscosity reduction, and scale prevention through multi-component compounding, and introducing biodegradable raw materials to reduce the environmental load have become the core paths to solve the triple challenges of "inefficient drainage - formation damage - ecological risk" in the development of high-salt reservoirs. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a high salt-resistant composite drainage aid and its preparation method, which solves the problems of poor salt resistance, low interfacial activity, fluid retention, and formation plugging of the drainage aid for high-salt reservoirs.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0008] A high salt-resistant composite drainage aid, comprising the following raw materials in parts by weight: 10-20 parts of modified sodium dodecylbenzenesulfonate, 5-10 parts of coconut oil amide propyl betaine, 8-15 parts of polyoxyethylene ether, 2-5 parts of nano-silica, 3-8 parts of sodium hexametaphosphate, 1-3 parts of low molecular weight polyacrylamide, 4-10 parts of modified polyacrylic acid-acrylamide copolymer, 15-30 parts of ethanol, 5-12 parts of ethylene glycol monobutyl ether, 2-6 parts of imidazoline derivative, 3-7 parts of aminotrimethylene phosphonic acid, 4-9 parts of sodium silicate, 2-5 parts of citric acid-sodium citrate.

[0009] The modified sodium dodecylbenzenesulfonate is prepared by quaternization modification and maleic anhydride grafting, and then loaded on nano-titanium dioxide.

[0010] The modified polyacrylic acid-acrylamide copolymer is a nano-cellulose reinforced long-chain alkyl modified polyacrylic acid-acrylamide copolymer.

[0011] Further, the degree of polymerization of the polyoxyethylene ether is 15; the particle size of the nano-silica is 20-50 nm, and the specific surface area ≥ 200 m 2 / g; the mass ratio of acrylic acid to acrylamide in the polyacrylic acid-acrylamide copolymer is 3:2.

[0012] Further, the specific preparation steps of the modified sodium dodecylbenzenesulfonate are as follows:

[0013] A1. Add sodium dodecylbenzenesulfonate to deionized water, stir to dissolve, and then slowly dropwise add trimethylamine ethanol solution, and stir and react at 50 °C for 2 h; after the reaction is completed, rotate and evaporate to remove ethanol to obtain quaternized sodium dodecylbenzenesulfonate.

[0014] A2. Mix the above quaternized product with maleic anhydride in toluene, add benzoyl peroxide, and stir and reflux at 80 °C for 4 h; after the reaction is completed, neutralize with sodium carbonate solution, then let stand for 2 h, separate the aqueous phase by liquid separation, and then distill off toluene to obtain maleic anhydride grafted quaternized sodium dodecylbenzenesulfonate.

[0015] A3. Disperse the second modified product and nano-titanium dioxide in isopropanol, ultrasonically disperse for 30 min, then stir and react at 60 °C for 6 h, filter, wash the filter cake with isopropanol, and then dry the product to obtain nano-titanium dioxide loaded maleic anhydride grafted quaternized sodium dodecylbenzenesulfonate.

[0016] Further, in the step A1, the dosage ratio of sodium dodecylbenzenesulfonate, deionized water, and trimethylamine ethanol solution is 50 g: 500 mL: 20 mL; the trimethylamine ethanol solution is prepared by dissolving 10 g of trimethylamine in 20 mL of absolute ethanol; the reaction stirring speed is 250 r / min; the rotary evaporation conditions are 60 °C, -0.09 MPa, and 100 r / min.

[0017] Further, in the step A2, the dosage ratio of maleic anhydride, toluene, and benzoyl peroxide is 30 g: 300 mL: 2 g; the mass fraction of the sodium carbonate solution is 8%; the reaction stirring speed is 300 r / min; the distillation conditions are 110 °C, -0.09 MPa;

[0018] Further, in the step A3, the dosage ratio of nano-titanium dioxide and isopropyl alcohol is 15 g: 400 mL; the stirring speed is 300 r / min, the temperature of isopropyl alcohol is 50 °C, the filter cake is washed 3 times, the product is pre-dried at 40 °C and -0.08 MPa for 3 h, and then dried at 60 °C and -0.09 MPa for 6 h.

[0019] Positive charge groups are introduced through trimethylamine quaternization to form an intramolecular electrostatic balance with sulfonate negative charges, resisting the charge shielding effect of high-salt ions and avoiding the destruction of micelle aggregates. After grafting maleic anhydride, polar carboxylic acid groups are introduced into the molecular chain, enhancing the hydrogen bond interaction with the rock surface, increasing the ratio of hydrophilic-hydrophobic segments at the same time, optimizing the interfacial orientation arrangement efficiency, and reducing the interfacial tension. Nano-titanium dioxide combines with surfactant molecules through physical adsorption to form a "core-shell" structure, increasing the thickness and mechanical strength of the adsorption layer, forming a stable interfacial film in a high-salt environment, and preventing the intrusion of salt ions.

[0020] Further, the modified polyacrylic acid-acrylamide copolymer is prepared by the following specific steps:

[0021] B1. Dissolve the polyacrylic acid-acrylamide copolymer in deionized water, add glycidyl methacrylate, and stir and react at 40 °C for 3 h;

[0022] B2. Add dodecylamine to the above reaction product and stir and react at 50 °C for 4 h;

[0023] B3. Disperse the second modified product and nanocellulose in dimethyl sulfoxide, stir and react at 70 °C for 5 h, while assisted by ultrasonic oscillation at 30 kHz, with 10 min of ultrasonic treatment per hour. After the reaction, transfer the reaction solution to a dialysis bag and dialyze it in deionized water for 72 h, replacing the fresh deionized water every 8 h. Freeze the dialyzed solution at -40 °C for 4 h to completely freeze it into a solid state, and immediately transfer it to a freeze dryer for drying for 48 h to obtain a nanocellulose-reinforced long-chain alkyl-modified polyacrylic acid-acrylamide copolymer.

[0024] Further, in the step B1, the dosage ratio of polyacrylic acid-acrylamide copolymer, deionized water, and glycidyl methacrylate is 40 g: 600 mL: 15 g; the stirring speed is 350 r / min; in the step B2, the dosage of dodecylamine is 25 g, and the stirring speed is 350 r / min.

[0025] Further, in the step B3, the dosage ratio of nanocellulose to dimethyl sulfoxide is 10 g: 500 mL; the stirring speed is 400 r / min; the molecular weight cut-off of the dialysis bag is 10,000 Da, and the dialysis process is carried out in an environment at 4 °C; the conditions for freeze-drying are -50 °C and 0.05 mbar.

[0026] The hydrophobic long chain is grafted by dodecylamine, and a dynamic network structure is formed through hydrophobic association to resist the compression of salt ions on the polymer molecular chain and maintain the viscosity stability of the solution. The nanocellulose is uniformly dispersed in the polymer network and combined with carboxyl and amide groups through hydrogen bonds to form a three-dimensional steric barrier to prevent salt ions from approaching the polymer molecular chain and inhibit the precipitation of aggregates. The copolymer segment formed by acrylic acid and acrylamide maintains the negative charge density by dissociating carboxyl groups in a high-salt environment and forms a hydrogen bond network by combining with the hydroxyl groups of nanocellulose to enhance the salt resistance stability.

[0027] A preparation method of a high salt-resistant composite drainage aid specifically includes the following steps:

[0028] S1. Add deionized water to the reaction kettle, and then sequentially add modified sodium dodecylbenzenesulfonate, cocamidopropyl betaine, and polyoxyethylene ether, and stir at 40 °C until completely dissolved;

[0029] S2. Add nanosilica, sodium hexametaphosphate, low molecular weight polyacrylamide, and modified polyacrylic acid-acrylamide copolymer to the reaction kettle, increase the rotation speed and stir for 40 min to fully disperse and mix each component;

[0030] S3. Add ethanol and ethylene glycol monobutyl ether as cosolvents to the reaction kettle, and keep stirring at a constant speed for 20 min to promote uniform dispersion of the system;

[0031] S4, add imidazoline derivative, aminotri(methylenephosphonic acid) and sodium silicate in sequence, and continue stirring for 30 min to ensure that all raw materials react fully;

[0032] S5. Finally, add citric acid-sodium citrate to adjust the pH value of the system to 7-8. After stirring for 15 minutes, filter out the insoluble matter to obtain a finished product of a high salt-resistant composite drainage agent.

[0033] Furthermore, in step S1, the stirring speed is 300 r / min; in steps S2-S5, the stirring speed is 400 r / min.

[0034] The present invention provides a high salt resistance composite drainage agent and a preparation method thereof, which has the following beneficial effects:

[0035] 1. Deep modification to construct a multi-level salt resistance mechanism: Through the three modifications of sodium dodecylbenzene sulfonate, namely quaternization, maleic anhydride grafting and nano-titanium dioxide loading, a triple mechanism of charge balance, polar group enhancement and nano-adsorption enhancement is introduced at the molecular level: quaternization forms an intramolecular electrostatically stable structure to resist salt ion charge shielding; maleic anhydride grafting increases polar carboxylic acid groups to enhance the adsorption force on the rock surface; nano-titanium dioxide loading forms a physical barrier to enhance the mechanical strength of the interfacial film, so that a single component has multiple salt resistance functions, breaking through the salt resistance limit of traditional surfactants.

[0036] 2. Scientific compounding of multiple components to achieve synergistic performance: The synergistic system is constructed in the formula through "surface activity regulation-polymer stabilization-ion chelation-auxiliary function integration": salt-resistant surfactants modified sodium dodecylbenzene sulfonate and cocamidopropyl betaine dominate the interfacial activity; salt-resistant stabilizers sodium hexametaphosphate and sodium silicate chelate high-valent ions to reduce the ionic strength of the solution; co-solvents ethanol and ethylene glycol butyl ether improve the mutual solubility of components; anti-scaling and corrosion inhibitors aminotri (methylenephosphonic acid) and imidazoline derivatives simultaneously inhibit scaling and metal corrosion, avoid performance antagonism caused by the compatibility of multiple agents, and achieve an integrated effect of salt resistance, resistance reduction, and pest prevention.

[0037] 3. Refined preparation technology ensures stability: The modification process adopts refined operations such as gradient temperature control, ultrasonic dispersion, and vacuum drying to ensure that the molecular structure of the final product remains stable in a high-salt environment and avoid performance fluctuations caused by preparation defects.

[0038] 4. Green preparation and environmentally friendly characteristics: The modification process uses biodegradable raw materials such as nanocellulose, maleic anhydride and low-toxic solvents such as isopropyl alcohol and dimethyl sulfoxide to reduce the use of traditional organic solvents; the post-processing step uses freeze-drying rather than high-temperature evaporation to maximize the retention of biodegradable groups in the raw materials; the formula does not contain harmful ingredients such as sulfur and phosphorus, and the biodegradation rate is higher than that of traditional products, which is in line with the development trend of green chemical additives in oil fields and reduces the potential risks of operations to the formation and the surrounding environment. Specific embodiments

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0040] Example 1: Preparation of a high salt-resistant composite drainage aid, and the specific steps are as follows:

[0041] S1. Add 200 parts of deionized water into a reaction kettle, and then successively add 10 parts of modified sodium dodecylbenzenesulfonate, 5 parts of cocamidopropyl betaine, 8 parts of polyoxyethylene ether, and stir at a speed of 300 r / min at 40 °C until completely dissolved;

[0042] S2. Add 2 parts of nano-silica, 3 parts of sodium hexametaphosphate, 1 part of low molecular weight polyacrylamide, and 4 parts of modified polyacrylic acid-acrylamide copolymer into the reaction kettle, and increase the stirring speed to 400 r / min and stir for 40 min;

[0043] S3. Add 15 parts of ethanol and 5 parts of ethylene glycol monobutyl ether into the reaction kettle, and keep stirring at the rotation speed for 20 min to promote uniform dispersion of the system;

[0044] S4. Successively add 2 parts of imidazoline derivative, 3 parts of aminotrimethylene phosphonic acid, and 4 parts of sodium silicate, and continue to stir at 400 r / min for 30 min to ensure that all raw materials react fully;

[0045] S5. Finally, add citric acid-sodium citrate to adjust the pH value of the system to 7, stir for 15 min, and then filter to remove insoluble substances to obtain the finished product of the high salt-resistant composite drainage aid.

[0046] Example 2: Preparation of a high salt-resistant composite drainage aid, and the specific steps are as follows:

[0047] S1. Add 200 parts of deionized water into a reaction kettle, successively add 20 parts of modified sodium dodecylbenzenesulfonate, 10 parts of cocamidopropyl betaine, 15 parts of polyoxyethylene ether, and stir at a speed of 300 r / min at 40 °C until completely dissolved;

[0048] S2. Add 5 parts of nano-silica, 8 parts of sodium hexametaphosphate, 3 parts of low molecular weight polyacrylamide, and 10 parts of modified polyacrylic acid-acrylamide copolymer into the reaction kettle, and increase the stirring speed to 400 r / min and continue to stir for 40 min;

[0049] S3. Add 30 parts of ethanol and 12 parts of ethylene glycol monobutyl ether into the reaction kettle, and keep stirring at the rotation speed for 20 min to promote uniform dispersion of the system;

[0050] S4. Add 6 parts of imidazoline derivative, 7 parts of aminotrimethylene phosphonic acid, and 9 parts of sodium silicate in sequence, and continue to stir at 400 r / min for 30 min to ensure that all raw materials react fully;

[0051] S5. Finally, add citric acid - sodium citrate to adjust the pH value of the system to 8. After stirring for 15 min, filter to remove insoluble substances to obtain the finished product of the high - salt - resistant composite drainage aid.

[0052] Example 3. The preparation of the high - salt - resistant composite drainage aid is as follows:

[0053] S1. Add 200 parts of deionized water into a reaction kettle, and add 15 parts of modified sodium dodecylbenzenesulfonate, 7 parts of cocamidopropyl betaine, and 11 parts of polyoxyethylene ether in sequence. Stir at 300 r / min at 40 °C until completely dissolved;

[0054] S2. Add 3 parts of nano - silica, 5 parts of sodium hexametaphosphate, 2 parts of low - molecular - weight polyacrylamide, and 7 parts of modified polyacrylic acid - acrylamide copolymer into the reaction kettle, and increase the stirring speed to 400 r / min and continue stirring for 40 min;

[0055] S3. Add 22 parts of ethanol and 8 parts of ethylene glycol monobutyl ether into the reaction kettle, and keep stirring for 20 min to promote uniform dispersion of the system;

[0056] S4. Add 4 parts of imidazoline derivative, 5 parts of aminotrimethylene phosphonic acid, and 6 parts of sodium silicate in sequence, and continue to stir at 400 r / min for 30 min to ensure that all raw materials react fully;

[0057] S5. Finally, add citric acid - sodium citrate to adjust the pH value of the system to 7.5. After stirring for 15 min, filter to remove insoluble substances to obtain the finished product of the high - salt - resistant composite drainage aid.

[0058] Example 4. The preparation of modified sodium dodecylbenzenesulfonate is as follows:

[0059] A1. Add 50 g of sodium dodecylbenzenesulfonate into 500 mL of deionized water. After stirring and dissolving, slowly dropwise add 20 mL of an ethanol solution containing 10 g of trimethylamine, and stir and react at 250 r / min at 50 °C for 2 h; after the reaction ends, rotate and evaporate to remove ethanol under the conditions of 60 °C, - 0.09 MPa, and 100 r / min to obtain quaternized sodium dodecylbenzenesulfonate;

[0060] A2. Mix the above quaternized product with 30 g of maleic anhydride in 300 mL of toluene, add 2 g of benzoyl peroxide, and stir and reflux at 80 °C at 300 r / min for 4 h; after the reaction is completed, neutralize with a sodium carbonate solution with a mass fraction of 8%, then let it stand for 2 h, separate and remove the aqueous phase, and distill off toluene at 110 °C and -0.09 MPa to obtain maleic anhydride-grafted quaternized sodium dodecylbenzenesulfonate;

[0061] A3. Disperse the second modified product and 15 g of nano-titanium dioxide in 400 mL of isopropanol, ultrasonically disperse for 30 min, then stir and react at 60 °C at 300 r / min for 6 h, filter, wash the filter cake with isopropanol at 50 °C three times, and then pre-dry the product at 40 °C and -0.08 MPa for 3 h, and then continue to dry at 60 °C and -0.09 MPa for 6 h to obtain nano-titanium dioxide-loaded maleic anhydride-grafted quaternized sodium dodecylbenzenesulfonate.

[0062] Example 5. Prepare a modified polyacrylic acid-acrylamide copolymer, and the specific steps are as follows:

[0063] B1. Dissolve 40 g of polyacrylic acid-acrylamide copolymer in 600 mL of deionized water, add 15 g of glycidyl methacrylate, and stir and react at 40 °C at 350 r / min for 3 h;

[0064] B2. Add 25 g of dodecylamine to the above reaction product, and stir and react at 50 °C at 350 r / min for 4 h;

[0065] B3. Disperse the second modified product and 10 g of nano-cellulose in 500 mL of dimethyl sulfoxide, stir and react at 70 °C at 400 r / min for 5 h, and at the same time assist with 30 kHz ultrasonic oscillation, ultrasonic for 10 min every hour; after the reaction is completed, transfer the reaction solution to a dialysis bag with a molecular weight cut-off of 10,000 Da, place it in 20 L of deionized water for dialysis for 72 h, and change the fresh deionized water every 8 h until the conductivity of the dialysis external solution is close to that of deionized water. The dialysis process is carried out in a low-temperature environment of 4 °C. Freeze the dialyzed solution in a low-temperature refrigerator at -40 °C for 4 h to completely freeze the solution into a solid state. Immediately transfer it to a freeze dryer after pre-freezing and dry it at -50 °C and 0.05 mbar for 48 h to obtain a nano-cellulose-reinforced long-chain alkyl-modified polyacrylic acid-acrylamide copolymer.

[0066] Comparative Example 1. Prepare a high salt-resistant composite drainage aid, and the specific steps are as follows:

[0067] Keep the remaining steps unchanged, and only replace the modified sodium dodecylbenzenesulfonate in Example 3 with sodium dodecylbenzenesulfonate without any treatment to prepare a high salt-resistant composite drainage aid.

[0068] Comparative Example 2. Preparation of a highly salt-resistant composite drainage aid, the specific steps are as follows:

[0069] The remaining steps remain unchanged. Only the modified polyacrylic acid-acrylamide copolymer in Example 3 is replaced with an untreated polyacrylic acid-acrylamide copolymer to prepare a highly salt-resistant composite drainage aid.

[0070] Performance test

[0071] Test Items Test Standards Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Salt Tolerance (NaCl Tolerance) (mg / L) SY / T 5755-2016 20 21 22 10 12 Interfacial Tension (mN / m) SY / T 5370-2018 0.5 0.6 0.4 1.5 1.2 Wettability (Contact Angle, °) SY / T 5153-2017 70 68 73 45 52 Foam Half-life (min) SY / T 7494-2020 22 20 25 6 8 Biodegradation Rate (%) OECD 301B (2021) 60 58 63 35 38

[0072] The performance test results show that the highly salt-resistant composite drainage aids of Examples 1-3 have a salt tolerance of 200,000-220,000 mg / L, an interfacial tension as low as 0.4-0.6 mN / m, a wettability contact angle of 68-73°, a foam half-life of 20-25 min, and a biodegradation rate of 58%-63%; while Comparative Examples 1-2, due to lack of modification, have significantly inferior performance to the examples, indicating that the modification process and the compounding system effectively improve the salt resistance, interfacial activity, wettability, foam stability and environmental friendliness of the drainage aid. Among them, Example 3 has the best comprehensive effect.

[0073] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology make various modifications or supplements or use similar methods to replace the specific embodiments described, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A high salt-resistant composite drainage aid, characterized in that: It contains the following raw materials in parts by weight: 10 - 20 parts of modified sodium dodecylbenzenesulfonate, 5 - 10 parts of cocamidopropyl betaine, 8 - 15 parts of polyoxyethylene ether, 2 - 5 parts of nano - silica, 3 - 8 parts of sodium hexametaphosphate, 1 - 3 parts of low - molecular - weight polyacrylamide, 4 - 10 parts of modified polyacrylic acid - acrylamide copolymer, 15 - 30 parts of ethanol, 5 - 12 parts of ethylene glycol monobutyl ether, 2 - 6 parts of imidazoline derivative, 3 - 7 parts of aminotrimethylenephosphonic acid, 4 - 9 parts of sodium silicate, 2 - 5 parts of citric acid - sodium citrate; The modified sodium dodecylbenzenesulfonate is prepared by quaternization modification and maleic anhydride grafting, and then loaded on nano - titanium dioxide; The modified polyacrylic acid - acrylamide copolymer is a long - chain alkyl - modified polyacrylic acid - acrylamide copolymer reinforced by nano - cellulose.

2. The high-salt-resistant composite flowback aid according to claim 1, characterized in that: The degree of polymerization of the polyethylene oxide ether is 15; the particle size of the nano-silica is 20 - 50 nm, and the specific surface area is ≥ 200 m 2 / g; the mass ratio of acrylic acid to acrylamide in the polyacrylic acid-acrylamide copolymer is 3:

2.

3. The high-salt-resistant composite drainage aid according to claim 1, wherein: The specific preparation steps of the modified sodium dodecylbenzenesulfonate are as follows: A1. Add sodium dodecylbenzenesulfonate to deionized water, stir to dissolve it, and then slowly dropwise add trimethylamine ethanol solution. Stir and react at 50 °C for 2 h; after the reaction is completed, rotate and evaporate to remove ethanol to obtain quaternized sodium dodecylbenzenesulfonate; A2. Mix the above quaternized product with maleic anhydride in toluene, add benzoyl peroxide, and stir and reflux at 80 °C for 4 h; after the reaction is completed, neutralize with sodium carbonate solution, then let it stand for 2 h, separate and remove the aqueous phase, and then distill to remove toluene to obtain maleic anhydride - grafted quaternized sodium dodecylbenzenesulfonate; A3. Disperse the second - modified product and nano - titanium dioxide in isopropanol, ultrasonically disperse for 30 min, then stir and react at 60 °C for 6 h, filter, wash the filter cake with isopropanol, and then dry the product to obtain nano - titanium dioxide - loaded maleic anhydride - grafted quaternized sodium dodecylbenzenesulfonate.

4. A high salt-resistant composite flowback aid according to claim 3, characterized in that: In the step A1, the dosage ratio of sodium dodecylbenzenesulfonate, deionized water, and trimethylamine ethanol solution is 50 g:500 mL:20 mL; The trimethylamine ethanol solution is prepared by dissolving 10 g of trimethylamine in 20 mL of absolute ethanol; the reaction stirring speed is 250 r / min; the rotary evaporation conditions are 60 °C, - 0.09 MPa, and 100 r / min.

5. The high-salt-resistant composite flowback aid according to claim 3, wherein: In the step A2, the dosage ratio of maleic anhydride, toluene, and benzoyl peroxide is 30 g:300 mL:2 g; the mass fraction of the sodium carbonate solution is 8%; the reaction stirring speed is 300 r / min; the distillation conditions are 110 °C, - 0.09 MPa; In the step A3, the dosage ratio of nano - titanium dioxide and isopropanol is 15 g:400 mL; the stirring speed is 300 r / min, the temperature of isopropanol is 50 °C, wash the filter cake 3 times, pre - dry the product at 40 °C and - 0.08 MPa for 3 h, and then continue to dry at 60 °C and - 0.09 MPa for 6 h.

6. The high salt-resistant composite flowback aid according to claim 1, wherein: The specific preparation steps of the modified polyacrylic acid - acrylamide copolymer are as follows: B1. Dissolve the polyacrylic acid - acrylamide copolymer in deionized water, add glycidyl methacrylate, and stir and react at 40 °C for 3 h; B2. Add dodecylamine to the above reaction product, and stir and react at 50 °C for 4 h; B3. Disperse the second modified product and nano-cellulose in dimethyl sulfoxide, stir and react at 70 °C for 5 h, while assisted by ultrasonic oscillation at 30 kHz, with 10 min of ultrasonic treatment per hour; after the reaction, transfer the reaction solution to a dialysis bag and dialyze it in deionized water for 72 h, replacing the fresh deionized water every 8 h; freeze the dialyzed solution at -40 °C for 4 h to completely freeze it into a solid state, and immediately transfer it to a freeze dryer after pre-freezing for drying for 48 h to obtain a long-chain alkyl-modified polyacrylic acid-acrylamide copolymer reinforced with nano-cellulose.

7. The high-salt-resistant composite drainage aid according to claim 6, characterized in that: In the step B1, the dosage ratio of polyacrylic acid-acrylamide copolymer, deionized water, and glycidyl methacrylate is 40 g: 600 mL: 15 g; the stirring speed is 350 r / min; in the step B2, the dosage of dodecylamine is 25 g, and the stirring speed is 350 r / min.

8. The high salt-resistant composite flowback aid according to claim 6, wherein: In the step B3, the dosage ratio of nano-cellulose to dimethyl sulfoxide is 10 g: 500 mL; the stirring speed is 400 r / min; the molecular weight cut-off of the dialysis bag is 10,000 Da, and the dialysis process is carried out in a 4 °C environment; the conditions for freeze-drying are -50 °C and 0.05 mbar.

9. A preparation method of a high salt-resistant composite flowback aid, characterized in that: Specifically, it includes the following steps: S1. Add deionized water to the reaction kettle, and then successively add modified sodium dodecylbenzenesulfonate, cocamidopropyl betaine, and polyoxyethylene ether, and stir at 40 °C until completely dissolved; S2. Add nano-silica, sodium hexametaphosphate, low-molecular-weight polyacrylamide, and modified polyacrylic acid-acrylamide copolymer to the reaction kettle, increase the rotation speed and stir for 40 min to fully disperse and mix each component; S3. Add ethanol and ethylene glycol monobutyl ether to the reaction kettle as co-solvents, and keep stirring at the rotation speed for 20 min to promote uniform dispersion of the system; S4. Successively add imidazoline derivative, aminotrimethylene phosphonic acid, and sodium silicate, and continue stirring for 30 min to ensure that all raw materials react fully; S5. Finally, add citric acid-sodium citrate to adjust the pH value of the system to 7-8, stir for 15 min, and then filter to remove insoluble substances to obtain the finished product of the high-salt-resistant composite drainage aid.

10. The preparation method of a high salt-resistant composite drainage aid according to claim 9, characterized in that: In the step S1, the stirring speed is 300 r / min; in the steps S2-S5, the stirring speed is 400 r / min.