An environmentally friendly nano-solvent for oilfield use and its preparation method

Abstract

This application relates to the technical field of chemical additives used in oilfield development, specifically disclosing an environmentally friendly nano-solvent for oilfields and its preparation method. The preparation method of an environmentally friendly nano-solvent for oilfields includes the following steps: S1: Under an inert atmosphere, N,N-dimethylformamide and hydroxyethyl cellulose are mixed evenly, then an organic base catalyst is added and mixed evenly. The mixture is heated to 35-45°C, aromatic acyl chloride is added, the temperature is raised to 75-85°C, and the reaction is carried out for 4-6 hours. After cooling, solid-liquid separation is performed, followed by washing, drying, and pulverization to obtain modified cellulose; S2: At 30-40°C, a co-solvent, xanthan gum, salt solution, and composite surfactant are mixed evenly, then the modified cellulose is added and mixed evenly. After dispersion, the environmentally friendly nano-solvent is obtained. The environmentally friendly nano-solvent obtained in this application has low interfacial tension and high viscosity reduction rate.

Description

Technical Field

[0001] This application relates to the technical field of chemical additives used in oilfield development, and more specifically, it relates to an environmentally friendly nano-solvent for oilfield use and its preparation method. Background Technology

[0002] In oilfield development, especially for heavy oil reservoirs, low-permeability reservoirs, and wellbore and near-wellbore areas clogged with organic scale, poor crude oil fluidity is a key issue restricting recovery rates. Therefore, injecting chemical solubilizers into the formation is one effective means to solve this problem. An ideal solubilizer can effectively emulsify crude oil, reduce its viscosity, and displace heavy organic deposits such as colloids and asphaltenes from the rock surface and pores, thereby achieving the goals of viscosity reduction, unclogging, and improved crude oil fluidity.

[0003] However, existing traditional solubilizers (such as conventional surfactants and organic solvents) have many limitations in practical applications: First, their solubilization and viscosity reduction efficiency is low, making it difficult to meet the extraction needs under complex formation conditions; second, to achieve effective solubilization and viscosity reduction, extremely high reagent dosages are often required, resulting in high extraction costs and poor economic efficiency; third, their temperature and salt resistance is poor, and they are prone to performance degradation or even failure in high-temperature and high-salt formation environments; and fourth, their environmental compatibility is insufficient, with some components easily polluting the formation ecology and surrounding environment, which is inconsistent with the current development trend of green oilfield development.

[0004] Patent application CN106520106A discloses a method for preparing a thick oil viscosity reducer. First, corn starch is used to prepare amylose. Then, camellia oil and rice bran oil are mixed and stirred with tea polyphenols and butylated hydroxyanisole to prepare a base oil. Then, maleic anhydride and octadecylamine are reacted to obtain maleic monooctadecylamide. This is then mixed with amylose and base oil to obtain the thick oil viscosity reducer.

[0005] In this technical solution, amylose, as a natural polymer, has a certain degree of hydrophilicity, but its molecular chain structure is regular and its interaction with heavy components such as gums and asphaltenes in heavy oil is weak. It is difficult to efficiently destroy the spatial network structure formed by heavy components, which often requires a high dosage to show a viscosity-reducing effect in practical applications. Camellia oil and rice bran oil, as conventional vegetable oils, have weak molecular polarity and mainly rely on the principle of like dissolves like to dilute crude oil, with limited emulsification and dispersion capabilities. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides an environmentally friendly nano-solvent for oil fields and its preparation method.

[0007] In a first aspect, this application provides a method for preparing an environmentally friendly nano-solvent for oilfield use, employing the following technical solution:

[0008] A method for preparing an environmentally friendly nano-solvent for oilfield use includes the following steps:

[0009] S1: Under an inert atmosphere, N,N-dimethylformamide and hydroxyethyl cellulose are mixed evenly, then an organic base catalyst is added and mixed evenly. The mixture is heated to 35~45℃, aromatic acyl chloride is added, the temperature is raised to 75~85℃, the reaction is carried out for 4~6 hours, cooled, solid-liquid separation is performed, the mixture is washed, dried, and pulverized to obtain modified cellulose.

[0010] S2: At 30~40℃, the cosolvent, xanthan gum, salt solution and composite surfactant are mixed evenly, and modified cellulose is added and mixed evenly. After dispersion, an environmentally friendly nano-solvent is obtained.

[0011] Preferably, the mass ratio of the hydroxyethyl cellulose, pyridine, and aromatic acyl chloride is 5:(1.1~1.3):(1.9~2.5).

[0012] Preferably, the mass ratio of the cosolvent, xanthan gum, salt solution, composite surfactant and modified cellulose is (10~12):(0.02~0.04):30:(1.5~2.0):10.

[0013] Preferably, the salt solution is a potassium chloride solution or a sodium chloride solution, with a mass fraction of 2% to 3%.

[0014] In this technical solution, firstly, a hydrophobic aromatic ring structure is covalently introduced into the hydrophilic skeleton of cellulose through the esterification reaction of aromatic acyl chloride and hydroxyethyl cellulose. The introduced aromatic ring can interact with polycyclic aromatic hydrocarbon components such as gums and asphaltenes in crude oil through π-π stacking and hydrophobic association. Secondly, the modified cellulose has both a hydrophilic skeleton and a hydrophobic aromatic ring, and it synergistically adsorbs with surfactants at the oil-water interface to form a composite interfacial film. The introduction of salt solution aims to adapt the product to a certain degree of mineralization during the preparation stage.

[0015] Preferably, the aromatic acyl chloride is selected from at least one of aromatic monoacyl chloride and aromatic diacyl chloride.

[0016] Preferably, the aromatic monoacyl chloride is selected from at least one of 2-naphthoyl chloride, 2-naphthoyl sulfonyl chloride, and biphenyl-4-carboxyl chloride.

[0017] Preferably, the aromatic diacyl chloride is 4,4'-biphenyldicarboxylic acid chloride.

[0018] In this technical solution, the bifunctionality of the aromatic diacyl chloride allows it to undergo esterification with the hydroxyl groups on two different hydroxyethyl cellulose molecular chains, thereby introducing covalent cross-linking points between the cellulose molecular chains. This structure helps to improve the structural stability and shear resistance of the modified cellulose under high temperature conditions.

[0019] Preferably, the organic base catalyst is pyridine.

[0020] In this technical solution, pyridine has the dual function of catalyst and acid binder, which can neutralize the HCl generated in the reaction and ensure that the esterification reaction proceeds efficiently and smoothly.

[0021] Preferably, in step S2, after dispersion, the step of adding silanized nano-silica is further included, wherein the amount of silanized nano-silica is 2% to 4% of the mass of the modified cellulose.

[0022] Preferably, the method for preparing the silanized nano-silica includes the following steps:

[0023] Nano-silica was dispersed in an aqueous ethanol solution, and octadecyltrimethoxysilane was added and mixed evenly. The pH was adjusted to 4.0-4.5, the temperature was raised to 50-60℃, and the reaction was carried out for 4-4.5 hours. The solid and liquid were separated, washed, and dried to obtain silanized nano-silica.

[0024] Preferably, the mass ratio of the nano-silica, the aqueous ethanol solution, and the octadecyltrimethoxysilane is 1:20:(0.4~0.6).

[0025] In this technical solution, these partially hydrophobic nanoparticles can spontaneously adsorb at the oil-water interface to form a solid particle film with a certain mechanical strength, which physically blocks the aggregation of droplets.

[0026] Preferably, in step S1, after the aromatic acyl chloride, a step of adding a long-chain aliphatic diacyl chloride is further included, wherein the mass ratio of the long-chain aliphatic diacyl chloride to the aromatic acyl chloride is (0.12~0.27):1.

[0027] Preferably, the long-chain aliphatic diacyl chloride is azelaic chloride.

[0028] In this technical solution, the introduction of long-chain aliphatic diacyl chloride flexible segments can adjust the hydrophilicity-hydrophobicity balance and molecular chain rigidity of modified cellulose, aiming to improve its interfacial behavior.

[0029] Preferably, in step S1, after adding aromatic acyl chloride and reacting, the following steps are also included: adding 5% to 10% of a cyclodextrin derivative by mass of hydroxyethyl cellulose, keeping the temperature constant, reacting for 1 to 2 hours, cooling, separating the solid and liquid, washing, drying, pulverizing, and obtaining modified cellulose.

[0030] Preferably, the cyclodextrin derivative is hydroxypropyl-β-cyclodextrin or sulfobutyl-β-cyclodextrin.

[0031] In this technical solution, the hydrophobic cavity inside the cyclodextrin derivative can selectively encapsulate specific small-molecule organic components (such as some small-molecule waxes and gums) in crude oil. This encapsulation effect based on size and polarity matching breaks down the complex aggregate structure of crude oil, thereby further improving the overall solubilization efficiency.

[0032] Preferably, the composite surfactant comprises alkylphenol polyoxyethylene ether phosphate and isomeric tridecyl alcohol polyoxyethylene ether.

[0033] In this technical solution, alkylphenol polyoxyethylene ether phosphate and isomeric tridecyl alcohol polyoxyethylene ether are compounded to form a mixed adsorption layer at the oil-water interface by utilizing their different hydrophilic head groups and salt-calcium resistant properties, thereby synergistically reducing interfacial tension and broadening the applicable temperature and salt range of the system.

[0034] Preferably, the co-solvent includes sorbitol and ethylene glycol butyl ether.

[0035] In this technical solution, sorbitol, as a polyol, can help stabilize the system, and ethylene glycol butyl ether, as a co-solvent, can enhance the system's ability to penetrate and dissolve organic matter.

[0036] Secondly, this application provides an environmentally friendly nanosolvent prepared by the above-mentioned preparation method.

[0037] In this technical solution, the environmentally friendly nano-solvent is essentially a nanocomposite dispersion system with water as the continuous phase, containing specific modified cellulose, surfactants, cosolvents, and stabilizers. The modified cellulose provides strong interaction sites with crude oil components, the compounded surfactant system provides interfacial activity, and the nanoscale dispersion and optional solid nanoparticles together constitute an intrinsically stable composite system, intended for use in oilfield solubilization and viscosity reduction operations.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. This application achieves specific targeted binding and dismantling of the aggregation network of gums and asphaltenes through the π-π interaction between aromatic rings and heavy components of crude oil. Simultaneously, this structure endows modified cellulose with amphiphilicity, enabling it to self-assemble at the oil-water interface and participate in the construction of a composite interfacial film, synergistically reducing interfacial tension and enhancing emulsion stability. The combination of these two aspects, from molecular recognition to macroscopic emulsification, jointly achieves a synergistic improvement in low interfacial tension and high viscosity reduction rate.

[0040] 2. In this application, by introducing diacyl chloride, appropriate covalent cross-linking points are constructed between the modified cellulose molecular chains. This weakly cross-linked network significantly enhances the structural integrity and shear resistance of the modified cellulose in high-temperature aqueous solutions, making it less prone to excessive molecular chain extension or desorption in the high-temperature environment of oil reservoirs, thereby ensuring the durability of the solubilization effect. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0043] The degree of substitution (DS) of hydroxyethyl cellulose is 1.8 to 2.0.

[0044] Before use, hydroxyethyl cellulose is vacuum dried at 60°C for 2 hours, then pulverized and passed through a 500-mesh standard sieve for later use.

[0045] The particle size distribution of nano-silica is 50~100nm.

[0046] Example 1

[0047] The preparation method of the environmentally friendly nano-solvent for oilfield use in this embodiment includes the following steps:

[0048] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer and mix at 200 rpm for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 11 g of pyridine and stir for 10 min. Heat to 35°C and slowly add a mixture of 19.1 g of 2-naphthoyl chloride through a constant pressure dropping funnel. (Mixed with 60 mL of N,N-dimethylformamide), after addition, the temperature was raised to 75℃ and reacted for 4 h. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm, filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), washed with saturated sodium bicarbonate until no bubbles were generated, washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60℃, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose;

[0049] S2: At 35℃, 20g of sorbitol, 30g of ethylene glycol butyl ether, 0.1g of xanthan gum, and 150g of 2% NaCl aqueous solution were added to a stirrer. The stirrer was turned on and the speed was 500rpm. After stirring and mixing for 15min, 4g of alkylphenol polyoxyethylene ether phosphate and 4g of isotridecyl alcohol polyoxyethylene ether were added and stirred and mixed for 10min. Then, 50g of modified cellulose was slowly added and dispersed at high speed of 2000rpm for 20min. Then, the mixture was transferred to a high-pressure homogenizer and homogenized 4 times under a pressure of 70MPa, controlling the particle size D90≤100nm. Finally, the mixture was stirred at 200rpm for 10min to obtain an environmentally friendly nano-solvent.

[0050] Example 2

[0051] The preparation method of the environmentally friendly nano-solvent for oilfield use in this embodiment includes the following steps:

[0052] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 13 g of pyridine and stir for 10 min. Heat to 45°C and slowly add a mixture of 2-naphthoyl chloride (23 g of 2-naphthoyl chloride and...) through a constant pressure dropping funnel. (60 mL of N,N-dimethylformamide was added). After the reaction was completed, the temperature was raised to 85°C and the reaction was carried out for 6 hours. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm. The mixture was filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. Then it was washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60°C, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0053] S2: At 35℃, add 24g of sorbitol, 36g of ethylene glycol butyl ether, 0.2g of xanthan gum, and 150g of a 3% KCl aqueous solution to a stirrer. Turn on the stirrer and mix at 500 rpm for 15 minutes.

[0054] Add 5g of alkylphenol polyoxyethylene ether phosphate and 5g of isotridecyl alcohol polyoxyethylene ether, stir and mix for 10min, then slowly add 50g of modified cellulose, and disperse at high speed of 2000rpm for 20min. Then transfer to a high-pressure homogenizer and homogenize 4 times under 70MPa pressure, controlling the particle size D90≤100nm. Add 1g of silanized nano silica, and then stir at 200rpm for 25min to obtain an environmentally friendly nano-solvent.

[0055] The preparation method of silanized nano-silica includes the following steps:

[0056] Add 100g of an ethanol-water solution (ethanol to deionized water volume ratio 4:1) to a reactor, add 5g of nano-silica, transfer to an ultrasonic device, adjust the parameters to 200W, 30kHz, and ultrasonically treat for 15min. Then add 2g of octadecyltrimethoxysilane, stir and mix evenly, adjust the pH to 4.5 with 5% acetic acid solution, heat to 50℃ in a water bath, stir and react for 4h, centrifuge, wash until neutral, and dry at 60℃ to constant weight to obtain silanized nano-silica.

[0057] Example 3

[0058] The preparation method of the environmentally friendly nano-solvent for oilfield use in this embodiment includes the following steps:

[0059] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Raise the temperature to 40°C and slowly add a mixture of 2-naphthalenesulfonyl chloride (25 g of 2-naphthalenesulfonyl chloride and...) through a constant pressure dropping funnel. (75 mL of N,N-dimethylformamide was added). After the reaction was completed, the temperature was raised to 80°C and the reaction was carried out for 5 hours. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm. The mixture was filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. The mixture was then washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60°C, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0060] S2: At 35℃, 18g of sorbitol, 27g of ethylene glycol butyl ether, 0.15g of xanthan gum, and 150g of 2% KCl aqueous solution were added to a stirrer. The stirrer was turned on and the speed was 500rpm. After stirring and mixing for 15min, 4.5g of alkylphenol polyoxyethylene ether phosphate and 4.5g of isotridecyl alcohol polyoxyethylene ether were added. After stirring and mixing for 10min, 50g of modified cellulose was slowly added. The mixture was sheared and dispersed at 2000rpm for 20min. Then, it was transferred to a high-pressure homogenizer and homogenized 4 times under 70MPa pressure. The particle size D90≤100nm was controlled. 1.5g of silanized nano silica was added. Then, the mixture was stirred at 200rpm for 25min to obtain an environmentally friendly nano-solvent.

[0061] The preparation method of silanized nano-silica includes the following steps:

[0062] Add 100g of an ethanol-water solution (ethanol to deionized water volume ratio 4:1) to a reactor, add 5g of nano-silica, transfer to an ultrasonic device, adjust the parameters to 200W, 30kHz, and ultrasonically treat for 15min. Then add 3g of octadecyltrimethoxysilane, stir and mix evenly, adjust the pH to 4.0 with a 5% acetic acid solution, heat to 60℃ in a water bath, stir and react for 4.5h, centrifuge, wash until neutral, and dry at 60℃ to constant weight to obtain silanized nano-silica.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 3 is as follows:

[0065] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Heat to 40 °C and slowly add a mixture of biphenyl-4-formyl chloride (biphenyl-4-formyl chloride 24) through a constant pressure dropping funnel. (The mixture of g and 75 mL of N,N-dimethylformamide) was added, and the temperature was raised to 80℃ and reacted for 5 h. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm, filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), washed with saturated sodium bicarbonate until no bubbles were generated, washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60℃, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose;

[0066] Everything else is the same as in Example 3.

[0067] Example 5

[0068] The difference between this embodiment and embodiment 4 is that:

[0069] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the stirring speed to 200 rpm. Add 11 g of pyridine and stir for 10 min. Raise the temperature to 40°C and slowly add a mixture of 2-naphthoyl chloride and 4,4'-biphenyldicarboxylate chloride (16.1 g of 2-naphthoyl chloride and 4,4'-biphenyldicarboxylate chloride) through a constant pressure dropping funnel. (4'-Biphenyldicarboxylic acid 5.5g and N,N-dimethylformamide 60mL were mixed). After the addition was completed, the temperature was raised to 80℃ and the reaction was carried out for 5h. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300rpm. The mixture was filtered, washed 3 times with 0.1mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), washed with saturated sodium bicarbonate until no bubbles were generated, washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60℃, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0070] The rest is the same as in Example 4.

[0071] Example 6

[0072] The difference between this embodiment and embodiment 5 is as follows:

[0073] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the stirring speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Heat to 40 °C and slowly add a mixture of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and azeloyl chloride (15.2 g of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and 4,4'-biphenyldicarboxylate chloride) through a constant pressure dropping funnel. (4.1g of '-biphenyl dicarboxylate chloride, 2.4g of azeloyl chloride, and 75mL of N,N-dimethylformamide were mixed. After the addition was complete, the temperature was raised to 80℃ and the reaction was carried out for 5 hours. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300rpm. The mixture was filtered, washed 3 times with 0.1mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. Then it was washed 3 times with deionized water, dried in a vacuum drying oven at 60℃ to constant weight, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0074] The rest is the same as in Example 5.

[0075] Example 7

[0076] The difference between this embodiment and embodiment 6 is that:

[0077] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the stirring speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Heat to 40 °C and slowly add a mixture of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and azeloyl chloride (15.2 g of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and 4,4'-biphenyldicarboxylate chloride) through a constant pressure dropping funnel. (3.7g of '-biphenyl dicarboxylate chloride, 4.8g of azeloyl chloride, and 75mL of N,N-dimethylformamide were mixed. After the addition was complete, the temperature was raised to 80℃ and the reaction was carried out for 5 hours. After cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300rpm. The mixture was filtered, washed 3 times with 0.1mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. Then it was washed 3 times with deionized water, dried in a vacuum drying oven at 60℃ to constant weight, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0078] The rest is the same as in Example 6.

[0079] Example 8

[0080] The difference between this embodiment and embodiment 7 is as follows:

[0081] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Heat to 40 °C. Slowly add a mixture of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and azeloyl chloride (15.2 g of 2-naphthoyl chloride, 3.7 g of 4,4'-biphenyldicarboxylate chloride, 4.8 g of azeloyl chloride, and N,N-dimethylformamide) through a constant pressure dropping funnel. The mixture of 75 mL of amine was added, and the temperature was raised to 80 °C and reacted for 5 h. The temperature was then lowered to 60 °C, and a mixture of 2.5 g of hydroxypropyl-β-cyclodextrin and 10 mL of N,N-dimethylformamide was added. The mixture was reacted for 1 h, and after cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm. The mixture was filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. The mixture was then washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60 °C, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0082] The rest is the same as in Example 7.

[0083] Example 9

[0084] The difference between this embodiment and embodiment 8 is as follows:

[0085] S1: Under a nitrogen atmosphere, add 500 mL of dehydrated N,N-dimethylformamide to the reactor. Turn on the stirrer at 200 rpm and stir for 10 min. Add 50 g of hydroxyethyl cellulose in 5 portions. After each addition, stir at 500 rpm for 30 min, then adjust the speed to 200 rpm. Add 12 g of pyridine and stir for 10 min. Heat to 40 °C. Slowly add a mixture of 2-naphthoyl chloride, 4,4'-biphenyldicarboxylate chloride, and azeloyl chloride (15.2 g of 2-naphthoyl chloride, 3.7 g of 4,4'-biphenyldicarboxylate chloride, 4.8 g of azeloyl chloride, and N,N-dimethylformamide) through a constant pressure dropping funnel. The mixture of 75 mL of amide was added, and the temperature was raised to 80 °C and reacted for 5 h. The temperature was then lowered to 55 °C, and a mixture of 5 g of sulfobutyl-β-cyclodextrin and 15 mL of N,N-dimethylformamide was added. The mixture was reacted for 2 h, and after cooling to room temperature, the reaction solution was poured into 5 times the volume of anhydrous ethanol at 300 rpm. The mixture was filtered, washed 3 times with 0.1 mol / L hydrochloric acid alcohol solution (ethanol and deionized water volume ratio 4:1), and washed with saturated sodium bicarbonate until no bubbles were generated. The mixture was then washed 3 times with deionized water, dried to constant weight in a vacuum drying oven at 60 °C, pulverized, and passed through a 500-mesh standard sieve to obtain modified cellulose.

[0086] The rest is the same as in Example 8.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is as follows:

[0089] 2-Naphthoyl chloride was replaced with an equimolar amount of dodecanoyl chloride (approximately 21.9 g);

[0090] Everything else is the same as in Example 1.

[0091] Performance testing

[0092] Working solution: The environmentally friendly nano-solvents prepared in Examples 1-9 and Comparative Example 1 were used to simulate formation water (ionic composition: Na). + 11000 mg / L, Ca 2+ 2000 mg / L, Mg 2+ 1500 mg / L, Cl - Dilute to 15500 mg / L, and mix the environmentally friendly nano-solvent with simulated formation water at a mass ratio of 25:75.

[0093] The viscosity of heavy oil from a certain oil field at 80℃ is 55000 mPa·s;

[0094] (1) Stability: Take 50 mL of the working solution and place it in a transparent glass bottle. Place it in an 80℃ constant temperature oven for 3 days and observe whether it separates into layers or precipitates. See Table 1 for details.

[0095] (2) Interfacial activity: Using a rotating drop interfacial tension meter, the above working fluid was used as the aqueous phase and heavy oil from a certain oil field was used as the oil phase. Under constant temperature of 80℃, the dynamic interfacial tension between oil and water was tested, and the lowest interfacial tension value when it reached equilibrium was recorded. See Table 1 for details.

[0096] (3) Viscosity reduction rate of heavy oil:

[0097] The working fluid and heavy oil from a certain oilfield were mixed in a sample cup at a mass ratio of 2:8. The cup was placed in an 80℃ constant temperature device and preheated for 15 minutes, during which time the mixture was stirred at 500 rpm for 10 minutes to ensure uniform system temperature and full action of the viscosity reducer. The mixture was then heated at 80℃ and a shear rate of 10 s⁻¹. -1 Under the same conditions, the apparent viscosity η of the mixed system was measured, and the viscosity η0 of the blank heavy oil was measured. The viscosity reduction rate (%) was calculated as [(η0-η) / η0]×100%, as shown in Table 1.

[0098] Table 1. Performance tests of the environmentally friendly nano-solvents prepared in Examples 1-9 and Comparative Example 1

[0099]

[0100] Analysis of the performance test results of Example 1 and Comparative Example 1 shows that: in Comparative Example 1, the substitution of aromatic acyl chloride with dodecanoyl chloride weakens the interaction between the modified product and the heavy components of crude oil, disrupts the hydrophilic-hydrophobic balance of the system, and consequently causes slight stratification in terms of stability. The interface regulation ability and viscosity reduction efficiency also decrease accordingly.

[0101] Analysis of the performance test results of Examples 1-3 shows that: by introducing silanized nano-silica in Examples 2-3, the interfacial tension was further reduced and the viscosity reduction rate was improved, demonstrating the synergistic enhancement effect of nanoparticles.

[0102] Analysis of the performance test results of Examples 4-9 shows that by optimizing the types of acyl chlorides and introducing multiple functional components for synergistic modification, the interfacial tension and viscosity reduction rate show a gradual increasing trend. This indicates that, while ensuring sufficient aromatic ring action, a multi-level synergistic mechanism is formed by introducing diacyl chlorides to construct moderate crosslinks, utilizing aliphatic chains to improve interfacial film flexibility, and leveraging the inclusion effect of cyclodextrins, thereby achieving in-depth optimization of solubilizing performance.

[0103] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing an environmentally friendly nano-solvent for oilfield use, characterized in that, Includes the following steps: S1: Under an inert atmosphere, N,N-dimethylformamide and hydroxyethyl cellulose are mixed evenly, then an organic base catalyst is added and mixed evenly. The mixture is heated to 35-45°C, an aromatic acyl chloride is added, and the temperature is raised to 75-85°C. The reaction is carried out for 4-6 hours, cooled, and the solid and liquid are separated. The mixture is washed, dried, and pulverized to obtain modified cellulose. The aromatic acyl chloride is selected from at least one of aromatic monoacyl chloride and aromatic diacyl chloride. The aromatic monoacyl chloride is selected from at least one of 2-naphthoyl chloride, 2-naphthalenesulfonyl chloride, and biphenyl-4-carboxyl chloride. The aromatic diacyl chloride is 4,4'-biphenyldicarboxyl chloride. S2: At 30~40℃, the co-solvent, xanthan gum, salt solution and composite surfactant are mixed evenly, modified cellulose is added and mixed evenly, and after dispersion, silanized nano silica is added to obtain an environmentally friendly nano-solvent; the composite surfactant includes alkylphenol polyoxyethylene ether phosphate and isomeric tridecyl alcohol polyoxyethylene ether, and the amount of silanized nano silica is 2%~4% of the mass of modified cellulose; The preparation method of silanized nano silica is as follows: nano silica is dispersed in an aqueous ethanol solution, octadecyltrimethoxysilane is added and mixed evenly, the pH is adjusted to 4.0~4.5, the temperature is raised to 50~60℃, the reaction is carried out for 4~4.5h, the solid and liquid are separated, washed, and dried to obtain silanized nano silica.

2. The preparation method of the environmentally friendly nano-solvent for oilfield use according to claim 1, characterized in that, The organic base catalyst is pyridine, and the mass ratio of hydroxyethyl cellulose, pyridine and aromatic acyl chloride is 5:(1.1~1.3):(1.9~2.5).

3. The method for preparing environmentally friendly nano-solvents for oilfields according to claim 1, characterized in that, The mass ratio of the co-solvent, xanthan gum, salt solution, composite surfactant and modified cellulose is (10~12):(0.02~0.04):30:(1.5~2.0):

10.

4. The method for preparing environmentally friendly nano-solvents for oilfields according to claim 1, characterized in that, The salt solution is a potassium chloride solution or a sodium chloride solution, with a mass fraction of 2% to 3%.

5. The method for preparing environmentally friendly nano-solvents for oilfields according to claim 1, characterized in that, In step S1, after the aromatic acyl chloride, there is also a step of adding a long-chain aliphatic diacyl chloride, wherein the mass ratio of the long-chain aliphatic diacyl chloride to the aromatic acyl chloride is (0.12~0.27):

1.

6. An environmentally friendly nano-solvent prepared by the method for preparing an environmentally friendly nano-solvent for oil fields as described in any one of claims 1 to 5.

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