Preparation method of supramolecular nano-imbibition oil displacement agent and application thereof in fracturing

Abstract

The application discloses a preparation method of a supramolecular nanometer imbibition oil displacement agent and application of the supramolecular nanometer imbibition oil displacement agent in fracturing, and relates to the technical field of oilfield exploitation. Methoxy polyethylene glycol amine is added dropwise into an activated NCA solution prepared by reaction of L-glutamic acid-5-benzyl ester N-carboxylic anhydride and triphosgene, and then is reacted and precipitated to obtain a polyethylene glycol-polybenzyl glutamate block copolymer; the block copolymer is dissolved in a hydrogen bromide solution to obtain a debenzylated product; under initiation of ammonium persulfate, the debenzylated product is reacted with vinyl phosphonic acid to obtain a supramolecular nanometer imbibition oil displacement powder; and the supramolecular nanometer imbibition oil displacement agent is obtained by dissolving, homogenizing and sterilizing filtering the powder. The supramolecular nanometer imbibition oil displacement agent is chelated with calcium and magnesium ions through phosphonic acid groups to form a stable network, so that the supramolecular nanometer imbibition oil displacement agent has long-term and stable effects in high-temperature and high-salt reservoirs; the supramolecular nanometer imbibition oil displacement agent has a flexible size matched with a pore throat structure, and can trigger capillary spontaneous imbibition by using ultralow interfacial tension to achieve efficient oil displacement.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a method for preparing supramolecular nano-permeation displacement agents and their application in fracturing. Background Technology

[0002] In the field of oil extraction, the efficient development of high-temperature, high-salinity, heterogeneous reservoirs has long faced technical bottlenecks. Traditional chemical flooding agents are ineffective in reservoirs with salinity exceeding 5×10⁻⁶. 3 In reservoirs with ppm or temperatures above 120°C, molecular chain coiling and precipitation failure are prone to occur, making it difficult to achieve deep residual oil drive. While existing nanomaterials for oil displacement possess the advantage of small size, their applicability in mining areas is limited due to their reliance on external magnetic or electric fields for activation. For example, patent CN109251741A discloses a magnetic nanoparticle oil displacement agent and its preparation method. This patent describes a modified magnetic nanoparticle oil displacement agent grafted with surfactants, which requires an external magnetic field to achieve a magnetic aggregation effect, thereby improving oil washing efficiency and assisting in demulsification of produced fluids. Furthermore, the adaptability of supramolecular systems is mostly limited to mild environments. In complex reservoirs rich in calcium and magnesium ions, the assembled structure is prone to collapse. For instance, patent CN102408516B discloses a hydrolysis-resistant polymer for oil displacement and its preparation method. It introduces three temperature- and salt-resistant monomers to copolymerize with acrylamide, synthesizing acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / acrylic acid and N-vinylpyrrolidone / N,N-dimethylacrylamide quaternary copolymers. Compared with ordinary polyacrylamide-based oil displacement agents, the cost is increased by 30%-40%, and it still cannot meet the application requirements under higher temperature and salinity conditions. Especially for capillary-bound oil in micron-sized pore-throat networks, conventional techniques are unable to stably reduce the oil-water interfacial tension or generate spontaneous adsorption, resulting in an oil recovery increase of less than 20%. Therefore, there is an urgent need to develop a new type of oil displacement agent that combines salt and temperature resistance, self-driven adsorption capability, and no need for external field assistance, in order to overcome the economic development barriers of deep and complex oil reservoirs.

[0003] The purpose of this invention is to provide a method for preparing supramolecular nano-permeation displacement agents and their application in fracturing, so as to solve the problems mentioned in the background art. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] The preparation method of supramolecular nano-permeation displacement agent includes the following steps:

[0006] S1. Dissolve the N-carboxyl anhydride of L-glutamic acid-5-benzyl ester in anhydrous tetrahydrofuran, add triphosgene, and stir at 35-45℃ for 2-3 hours to obtain an activated NCA solution.

[0007] Furthermore, the ratio of L-glutamic acid-5-benzyl ester N-carboxylated intracyclic anhydride, anhydrous tetrahydrofuran, and triphosgene is (2.6-2.67) g: 50 mL: (0.32-0.34) g;

[0008] It should be noted that L-glutamic acid-5-benzyl ester N-carboxyl anhydride (NCA) reacts with triphosgene in tetrahydrofuran solvent. Triphosgene decomposes in situ to produce phosgene. The active chloroformyl group of phosgene attacks the nitrogen atom (N3 position) on the five-membered ring of NCA monomer, providing a highly reactive chloroformate intermediate (containing chloroformate group) for subsequent ring-opening polymerization. This significantly enhances the electrophilicity of the anhydride bond in the ring and ensures that NCA monomer is efficiently converted into a polymerizable form.

[0009] S2. Add methoxy polyethylene glycol amine dropwise to the activated NCA solution and react at 45-55℃ for 24-36h under argon protection. Add the reaction solution to ice-cold ether to precipitate and centrifuge to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0010] Furthermore, the molecular weight of the methoxy polyethylene glycolamine is 1600-2400;

[0011] Furthermore, the ratio of the amount of methoxy polyethylene glycolamine, activated NCA solution and icy ether is (0.38-0.42) g:(45-55) mL:(400-600) mL;

[0012] It should be noted that the terminal amino group of the methoxy polyethylene glycol amine acts as a nucleophile, attacking the C5-carbonyl carbon activated by the strongly electron-activated group in the NCA, causing the five-membered ring to open and forming an unstable tetrahedral transition state. The chloroformate group (-OCOCl), as a highly efficient leaving group, is rapidly removed, decomposing into CO2 and HCl in the form of chloroformic acid, while simultaneously generating a new free amino group. This new amino group immediately serves as the nucleophilic initiation site for the next activated NCA monomer, initiating chain growth reactions sequentially. Under an inert atmosphere, the ring-opening polymerization process continues, generating an amphiphilic polyethylene glycol-polybenzyl glutamate block copolymer (mPEG-PBLG).

[0013] S3. Dissolve the polyethylene glycol-polybenzyl glutamate block copolymer in hydrogen bromide solution, stir at 0-5℃ for 4-6 h, centrifuge, and wash the precipitate three times with cold diethyl ether to obtain the debenzylated product.

[0014] Furthermore, the hydrogen bromide solution contains 30-33% hydrogen bromide by mass, and its solvent is acetic acid;

[0015] Furthermore, the ratio of the polyethylene glycol-polybenzyl glutamate block copolymer, hydrogen bromide solution, and cold diethyl ether is 1g:(5-10)mL:(15-30)mL;

[0016] It should be noted that the hydrogen bromide in the hydrogen bromide solution first protonates the carbonyl oxygen of the benzyl ester group in polybenzyl glutamate (PBLG), converting it into a highly reactive oxonium ion. This activation weakens the polarity of the carbon-oxygen bond of the benzyl ester group, allowing the bromide ion to attack the benzyl carbon atom, replacing it to generate the benzyl bromide byproduct, while simultaneously releasing the free polyglutamate carboxyl group (-COOH). Low temperature suppresses side reactions, acetic acid solvent provides a suitable polar environment to promote ionization, and cold ether washing effectively removes residual benzyl bromide, hydrogen bromide, and small molecule impurities, yielding a water-soluble polyethylene glycol-polyglutamate block copolymer (mPEG-PGA).

[0017] S4. Dissolve the debenzylated product in deionized water, add vinylphosphonic acid and ammonium persulfate, react at 55-65℃ under nitrogen protection for 4-8 hours, dialyze, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder.

[0018] Furthermore, the ratio of the debenzylated product, deionized water, vinylphosphonic acid, and ammonium persulfate is 1g:(20-50)mL:(1-5)mL:(0.1-0.3)g;

[0019] Furthermore, the dialysis step has a molecular weight cutoff of 3500 Da;

[0020] It should be noted that free radical polymerization occurs under the initiation of ammonium persulfate, introducing polyvinyl phosphonic acid chains. Small molecule byproducts are removed by dialysis, and freeze-drying yields phosphonic acid-functionalized polyethylene glycol-b-polyglutamic acid block copolymer (mPEG-PGA-PVPA, supramolecular nano-permeation oil displacement powder) with metal chelating ability.

[0021] S5. Disperse the supramolecular nano-permeation oil displacement powder in deionized water, stir at 400-600 r / min for 30-40 min at 25-40℃, sonicate in an ice bath for 3-5 min, and filter through a microporous membrane for sterilization to obtain the supramolecular nano-permeation oil displacement agent.

[0022] Furthermore, the ratio of the supramolecular nano-permeation oil displacement powder to deionized water is (0.1-0.3) g: 100 mL;

[0023] Furthermore, the microporous filter membrane has a pore size of 0.22 μm;

[0024] It should be noted that after the supramolecular nano-permeation displacement agent is injected into the reservoir, its amphiphilic block structure spontaneously assembles into flexible nanofibers in the formation water. The phosphonic acid groups lock in divalent / trivalent metal cations (especially calcium and magnesium ions) in the formation water through chelation, endowing it with high-salt stability; the hydrophobic polyglutamic acid segment inserts into the crude oil phase to reduce the oil-water interfacial tension, while the hydrophilic polyethylene glycol segment anchors the aqueous phase, forming steric hindrance. The nanofibers, with their ultra-small size of 20-50 nm, penetrate deep into micron-level pores and throats, driving the spontaneous permeation and displacement of residual oil through capillary action. Simultaneously, the phosphonic acid group-metal chelate network maintains structural stability at high temperatures. The supramolecular nano-permeation displacement agent prepared in this invention can achieve efficient development of deep reservoirs and significantly improve the oil recovery rate of high-temperature, high-salt heterogeneous formations.

[0025] This invention also provides an application of a supramolecular nano-permeation displacement agent in fracturing.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The supramolecular nano-permeation displacement agent of this invention forms a stable network by chelating calcium and magnesium ions with phosphonic acid groups, giving it a long-term stable effect in high-temperature and high-salinity oil reservoirs; the self-assembled nanofibers, with their flexible size-matched pore-throat structure, utilize ultra-low interfacial tension to trigger spontaneous capillary permeation, efficiently displacing residual oil in microcracks; the preparation process avoids precious metal catalysts, and the water-based dispersion is directly injected, significantly reducing the cost and environmental risk of field application, providing an innovative solution for the development of deep and complex oil reservoirs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0029] Figure 1 The infrared spectrum of the supramolecular nano-permeation displacement agent prepared in Example 1 of this invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1, a method for preparing a supramolecular nano-permeation displacement agent, includes the following steps:

[0032] S1. Dissolve 2.64g of L-glutamic acid-5-benzyl ester N-carboxyl ring anhydride in 50mL of anhydrous tetrahydrofuran, add 0.33g of triphosgene, stir at 40℃ for 2h to obtain an activated NCA solution.

[0033] S2. 1.6g of methoxy polyethylene glycolamine with a molecular weight of 2000 was added dropwise to 200mL of activated NCA solution and reacted at 50℃ for 24h under argon protection. The reaction solution was added to 2000mL of ice-cold ether to precipitate, centrifuged, and dried to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0034] S3. Dissolve 1g of polyethylene glycol-polybenzyl glutamate block copolymer in 8mL of 33% hydrogen bromide solution, stir at 5℃ for 4h, centrifuge, wash the precipitate 3 times with 30mL of cold diethyl ether, and dry to obtain the debenzylated product.

[0035] S4. Dissolve 1g of the debenzylated product in 35mL of deionized water, add 3mL of vinylphosphonic acid and 0.2g of ammonium persulfate, react at 60℃ under nitrogen protection for 6h, dialyze at 3500Da, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder.

[0036] S5. Disperse 1g of supramolecular nano-permeation displacement powder in 500mL of deionized water, stir at 35℃ and 500r / min for 30min, sonicate in an ice bath for 4min, and filter through a 0.22μm microporous membrane for sterilization to obtain supramolecular nano-permeation displacement agent.

[0037] Example 2, S1: Dissolve 2.6g of L-glutamic acid-5-benzyl ester N-carboxyl ring anhydride in 50mL of anhydrous tetrahydrofuran, add 0.32g of triphosgene, stir at 40℃ for 2h to obtain an activated NCA solution;

[0038] S2. 1.52g of methoxy polyethylene glycolamine with a molecular weight of 2000 was added dropwise to 180mL of activated NCA solution and reacted at 50℃ for 24h under argon protection. The reaction solution was added to 2000mL of ice-cold ether to precipitate, centrifuged, and dried to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0039] S3. Dissolve 1g of polyethylene glycol-polybenzyl glutamate block copolymer in 5mL of 33% hydrogen bromide solution, stir at 5℃ for 4h, centrifuge, wash the precipitate 3 times with 30mL of cold diethyl ether, and dry to obtain the debenzylated product.

[0040] S4. Dissolve 1g of the debenzylated product in 20mL of deionized water, add 1mL of vinylphosphonic acid and 0.1g of ammonium persulfate, react at 60℃ under nitrogen protection for 6h, dialyze at 3500Da, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder.

[0041] S5. Disperse 0.5g of supramolecular nano-permeation displacement powder in 500mL of deionized water, stir at 500r / min for 30min at 35℃, sonicate in an ice bath for 4min, and filter through a 0.22μm microporous membrane for sterilization to obtain supramolecular nano-permeation displacement agent.

[0042] Example 3, S1: Dissolve 2.67g of L-glutamic acid-5-benzyl ester N-carboxyl ring anhydride in 50mL of anhydrous tetrahydrofuran, add 0.34g of triphosgene, stir at 40℃ for 2h to obtain an activated NCA solution;

[0043] S2. 1.68 g of methoxy polyethylene glycol amine with a molecular weight of 2000 was added dropwise to 220 mL of activated NCA solution and reacted at 50 °C for 24 h under argon protection. The reaction solution was added to 2000 mL of ice-cold diethyl ether to precipitate, centrifuged, and dried to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0044] S3. Dissolve 1g of polyethylene glycol-polybenzyl glutamate block copolymer in 10mL of 33% hydrogen bromide solution, stir at 5℃ for 4h, centrifuge, wash the precipitate three times with 30mL of cold diethyl ether, and dry to obtain the debenzylated product.

[0045] S4. Dissolve 1g of the debenzylated product in 50mL of deionized water, add 5mL of vinylphosphonic acid and 0.3g of ammonium persulfate, react at 60℃ under nitrogen protection for 6h, dialyze at 3500Da, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder.

[0046] S5. Disperse 0.9g of supramolecular nano-permeation displacement powder in 300mL of deionized water, stir at 500r / min for 30min at 35℃, sonicate in an ice bath for 4min, and filter through a 0.22μm microporous membrane for sterilization to obtain supramolecular nano-permeation displacement agent.

[0047] Comparative Example 1

[0048] The preparation method of supramolecular nano-permeation displacement agent includes the following steps:

[0049] S1. Dissolve 2.64g of L-glutamic acid-5-benzyl ester N-carboxyl ring anhydride in 50mL of anhydrous tetrahydrofuran, add 0.33g of triphosgene, stir at 40℃ for 2h to obtain an activated NCA solution.

[0050] S2. 1.6g of methoxy polyethylene glycolamine with a molecular weight of 2000 was added dropwise to 200mL of activated NCA solution and reacted at 50℃ for 24h under argon protection. The reaction solution was added to 2000mL of ice-cold ether to precipitate, centrifuged, and dried to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0051] S3. Dissolve 1g of polyethylene glycol-polybenzyl glutamate block copolymer in 8mL of 33% hydrogen bromide solution, stir at 5℃ for 4h, centrifuge, wash the precipitate 3 times with 30mL of cold diethyl ether, and dry to obtain the debenzylated product.

[0052] S4. Disperse 1g of the debenzylated product in 500mL of deionized water, stir at 500r / min for 30min at 35℃, sonicate in an ice bath for 4min, and filter through a 0.22μm microporous membrane for sterilization to obtain a supramolecular nano-permeation oil displacement agent.

[0053] The difference between this comparative example and Example 1 is that step S4 was omitted, and the supramolecular nano-permeation displacement agent was prepared directly using the debenzylated product.

[0054] Comparative Example 2

[0055] The preparation method of supramolecular nano-permeation displacement agent includes the following steps:

[0056] S1. Dissolve 2.64g of L-glutamic acid-5-benzyl ester N-carboxyl ring anhydride in 50mL of anhydrous tetrahydrofuran, add 0.33g of triphosgene, stir at 40℃ for 2h to obtain an activated NCA solution.

[0057] S2. 1.6g of methoxy polyethylene glycolamine with a molecular weight of 2000 was added dropwise to 200mL of activated NCA solution and reacted at 50℃ for 24h under argon protection. The reaction solution was added to 2000mL of ice-cold ether to precipitate, centrifuged, and dried to obtain polyethylene glycol-polybenzyl glutamate block copolymer.

[0058] S3. Dissolve 1g of polyethylene glycol-polybenzyl glutamate block copolymer in 35mL of deionized water, add 3mL of vinylphosphonic acid and 0.2g of ammonium persulfate, react at 60℃ under nitrogen protection for 6h, dialyze at 3500Da, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder.

[0059] S4. Disperse 1g of supramolecular nano-permeation displacement powder in 500mL of deionized water, stir at 35℃ at 500r / min for 30min, sonicate in an ice bath for 4min, and filter through a 0.22μm microporous membrane for sterilization to obtain supramolecular nano-permeation displacement agent.

[0060] The difference between this comparative example and Example 1 is that step S3 was omitted, and supramolecular nano-permeation and oil displacement powder was prepared directly using polyethylene glycol-polybenzyl glutamate block copolymer.

[0061] test:

[0062] I. Testing of interfacial tension

[0063] The interfacial tension of the nano-oil displacement agent in the examples and comparative examples was tested using a TX-500C interfacial tension meter. The test temperature was set to 100°C, and the test crude oil was experimental standard dehydrated crude oil with a wax content of 35%.

[0064] The test results are shown in Table 1.

[0065] II. Oil Displacement Efficiency Test

[0066] Oil displacement experiments were conducted using a core displacement device to simulate reservoir conditions. Multiple artificial heterogeneous cores were taken, and the basic parameters of the cores were measured and recorded. The experimental temperature was 120℃, and the original oil saturation was recorded. Subsequently, water flooding was carried out until the water cut reached 95%. After the water flooding was completed, supramolecular nano-permeation displacement agents prepared in the examples and comparative examples were injected respectively, and the primary recovery rate of the cores was recorded.

[0067] The test results are shown in Table 1.

[0068] III. Salt resistance test

[0069] The supramolecular nano-permeation displacement agents prepared in the examples and comparative examples were tested for salt resistance under different salinity levels.

[0070] The test results are shown in Table 2.

[0071]

[0072] As shown in Table 1, compared with Comparative Examples 1-2, the supramolecular nano-permeation displacement agents prepared in Examples 1-3 have extremely low interfacial tension and a stable primary recovery rate of over 34%.

[0073]

[0074] As shown in Table 2, compared with Comparative Examples 1-2, the viscosity of the system in Examples 1-3 at the same salinity is significantly better than that in Comparative Examples 1-2, indicating that the supramolecular nano-permeation displacement agent prepared in Examples 1-3 has better salt resistance.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0076] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the scope defined by the invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A method for preparing a supramolecular nano-permeation displacement agent, characterized in that: Includes the following steps: S1. Dissolve L-glutamic acid-5-benzyl ester-N-carboxyl ring anhydride in anhydrous tetrahydrofuran, add triphosgene, and stir at 35-45℃ for 2-3 hours to obtain an activated NCA solution. The ratio of L-glutamic acid-5-benzyl ester-N-carboxylic acid anhydride, anhydrous tetrahydrofuran, and triphosgene used is (2.6-2.67) g: 50 mL: (0.32-0.34) g; S2. Add methoxy polyethylene glycol amine dropwise to the activated NCA solution and react at 45-55℃ for 24-36h under argon protection. Add the reaction solution to ice-cold ether to precipitate and centrifuge to obtain polyethylene glycol-polybenzyl glutamate block copolymer. The molecular weight of the methoxy polyethylene glycol amine is 1600-2400; The ratio of the amount of methoxy polyethylene glycolamine, activated NCA solution and icy ether is (0.38-0.42) g: (45-55) mL: (400-600) mL; S3. Dissolve the polyethylene glycol-polybenzyl glutamate block copolymer in hydrogen bromide solution, stir at 0-5℃ for 4-6 h, centrifuge, and wash the precipitate three times with cold diethyl ether to obtain the debenzylated product. The ratio of the polyethylene glycol-polybenzyl glutamate block copolymer, hydrogen bromide solution and cold diethyl ether is 1g:(5-10)mL:(15-30)mL; S4. Dissolve the debenzylated product in deionized water, add vinylphosphonic acid and ammonium persulfate, react at 55-65℃ under nitrogen protection for 4-8 hours, dialyze, freeze, and dry to obtain supramolecular nano-permeation oil displacement powder. The ratio of the debenzylated product, deionized water, vinylphosphonic acid, and ammonium persulfate is 1g:(20-50)mL:(1-5)mL:(0.1-0.3)g; S5. Disperse the supramolecular nano-permeation oil displacement powder in deionized water, stir at 400-600 r / min for 30-40 min at 25-40℃, sonicate in an ice bath for 3-5 min, and filter through a 0.22μm microporous membrane for sterilization to obtain the supramolecular nano-permeation oil displacement agent. The ratio of the supramolecular nano-permeation oil displacement powder to deionized water is (0.1-0.3) g: 100 mL.

2. The preparation method of the supramolecular nano-permeation displacement agent according to claim 1, characterized in that: In step S3, the hydrogen bromide solution contains 30-33% hydrogen bromide by mass, and the solvent is acetic acid.

3. The application of the supramolecular nano-permeation displacement agent prepared by the preparation method according to any one of claims 1-2 in fracturing.

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