A multi-effect acid system for reducing fracture pressure of muddy reservoir and preparation method thereof

Abstract

The present invention belongs to the technical field of gas reservoir exploitation, and discloses a multi-functional acid system for reducing the fracture pressure of muddy reservoirs and a preparation method thereof. The mass percentage of each component in the multi-functional acid system is: hydrochloric acid 5-10.0%, hydrofluoric acid 5%, multi-functional acid 1.0-3.0%, corrosion inhibitor 3.0-5.0%, acidizing agent 0.5-1.0%, stabilizer 1.0-2.0%, and the balance is water. The multi-functional acid of the present invention has efficient and specific recognition of metal cations such as silicon ions, magnesium ions, and calcium ions produced during the acidification process of muddy reservoirs by using a tetrapod polycarboxylic acid skeleton; by introducing an amide group, the multi-functional acid is made more capable of binding to metal cations; by introducing a long-chain alkyl hydrophobic group, the cations can be more tightly wrapped to avoid the cations from contacting hydroxide to produce metal hydroxide precipitation and causing reservoir damage; the multi-functional acid system of the present invention can reduce the fracture pressure of the reservoir during fracturing construction.

Description

Technical Field

[0001] The invention belongs to the technical field of gas reservoir exploitation, and in particular relates to a multi-effect acid system for reducing the fracture pressure of muddy reservoirs and a preparation method thereof. Background Art

[0002] In recent years, the global demand for oil and gas resources has continued to increase, and their development remains a global hotspot. Increasing oil and gas field production is urgently needed. my country's oil and gas reservoirs are relatively complex, characterized by diverse rock and mineralogy, strong reservoir heterogeneity, and significant variations in permeability, making extraction challenging. Fracturing and acidizing technology is not only a leading technology for increasing and stabilizing production in development wells, but has also become an essential tool for discovering oil and gas or proving reserves in exploration wells. This technology has received significant attention both domestically and internationally, providing a powerful foundation for discovering oil and gas, verifying production rates, stabilizing and improving oil and gas recovery, and achieving economical and efficient extraction of oil and gas resources. Domestic researchers have developed a range of acid systems, including gel acid, cross-linked acid, foam acid, microlactic acid, composite acid, and retarded acid systems, as well as techniques such as pre-fluid acidizing, sand-added acidizing, multi-stage injection acidizing, and multi-component and multi-system alternating injection acidizing. These techniques are primarily targeted at acidizing and fracturing reservoirs with relatively pure mineral compositions. Carbonate reservoirs are primarily composed of dissolved calcite and dolomite, while sandstone reservoirs are primarily composed of dissolved quartz and feldspar. For oil and gas reservoirs with high shale content, due to their complex mineral salinity and poor plasticity, fracturing often results in high operating pressures, difficulty in fracturing the reservoir, and difficulty adding sand. Currently, there is no clear, effective acid system for reducing the fracture pressure of shale reservoirs.

[0003] Therefore, it is necessary to provide an acid system for reducing the fracture pressure of mud-containing reservoirs. By adopting the synergistic effect of a mixed acid solution of hydrochloric acid and hydrofluoric acid and multi-effect acid, the metal ions produced during the acidizing process can be stabilized, thereby ultimately achieving the purpose of reducing the fracture pressure of the formation and filling the gap in the field of fracturing acidizing in high-mud-content reservoirs. Summary of the Invention

[0004] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide an acid solution system for reducing the fracture pressure of muddy reservoirs. By adopting the synergistic effect of a mixed acid solution of hydrochloric acid and hydrofluoric acid and a multi-functional acid, the metal ions generated during the acidizing process are stabilized, thereby ultimately achieving the purpose of reducing the fracture pressure of the formation.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a multi-effect acid system for reducing the fracture pressure of muddy reservoirs, characterized by comprising the following steps:

[0007] Preparation of paiotropic acid;

[0008] mixing and stirring hydrochloric acid, hydrofluoric acid and water to obtain a mixed acid solution;

[0009] Adding a corrosion inhibitor, an acidifying drainage agent, a stabilizer and a multi-functional acid to the mixed acid solution and stirring to obtain a multi-functional acid system;

[0010] The mass percentage of each component in the polyfunctional acid system is as follows: hydrochloric acid 5-10.0%; hydrofluoric acid 5%; polyfunctional acid 1.0-3.0%; corrosion inhibitor 3.0-5.0%; acidifying drainage agent 0.5-1.0%; stabilizer 1.0-2.0%; and the balance is water.

[0011] Furthermore, the preparation of paiotropic acid comprises:

[0012] Preparation of amino esters protected with tert-butyloxycarbonyl groups using tert-butyl bromoacetate, anhydrous acetonitrile, triethylamine, and ethylenediamine with alkyl substituents of varying lengths;

[0013] Preparation of amides using amino esters protected with a tert-butyloxycarbonyl group;

[0014] Preparation of polyfunctional acids using amides.

[0015] Furthermore, amino esters protected with a tert-butyloxycarbonyl group were prepared using tert-butyl bromoacetate, anhydrous acetonitrile, triethylamine, and ethylenediamine with alkyl substituents of varying lengths, including:

[0016] Under argon protection, anhydrous acetonitrile, triethylamine, and ethylenediamine with alkyl substituents of different lengths are mixed and stirred to obtain a first solution;

[0017] dissolving tert-butyl bromoacetate in anhydrous acetonitrile and adding the solution dropwise thereto for reaction to obtain a first solid-liquid mixture, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine is 3-5:1;

[0018] filtering the first solid-liquid mixture to obtain a first filtrate, and performing reduced pressure distillation on the first filtrate to obtain a solid amino ester intermediate;

[0019] The solid amino ester intermediate is purified by column chromatography to obtain the amino ester protected by the tert-butyloxycarbonyl group.

[0020] Furthermore, when the solid amino ester intermediate is purified by column chromatography to obtain an amino ester protected by a tert-butyloxycarbonyl group, the first eluent used to purify the solid amino ester intermediate includes diethyl ether and n-hexane, and the volume ratio of diethyl ether to n-hexane is 1:100.

[0021] Further, the amide is prepared using an amino ester protected by a tert-butyloxycarbonyl group, comprising:

[0022] Under argon protection, dissolving the amino ester protected by the tert-butyloxycarbonyl group and 2-chloroacetoacetic acid in acetonitrile at a molar ratio of 1:1-2 to obtain a second solution;

[0023] adding potassium carbonate, potassium iodide, and sodium sulfate to the second solution and stirring, reacting under constant temperature reflux and cooling to room temperature to obtain a second solid-liquid mixture;

[0024] filtering the second solid-liquid mixture to obtain a second filtrate, and subjecting the second filtrate to reduced pressure distillation to obtain an amide intermediate;

[0025] The amide intermediate is purified by column chromatography to obtain amide.

[0026] Further, the amide intermediate is purified by column chromatography to obtain an amide, including:

[0027] The second eluent used to purify the amide intermediate includes ethyl acetate and n-hexane, and the volume ratio of ethyl acetate to n-hexane is 1:1.

[0028] Furthermore, when amide is used to prepare paeotropic acid, amide and anisole are dissolved in dichloromethane at a molar ratio of 1:5-10 and stirred to obtain a third solution;

[0029] adding a strong acid to the third solution and stirring under argon protection at room temperature to obtain a fourth solution, performing vacuum distillation on the fourth solution to obtain a residue, dissolving the residue in dichloromethane and performing vacuum distillation to obtain a concentrated solution, adding ether to the concentrated solution and ultrasonically stirring until a white paeotropic acid product appears, thereby obtaining a third solid-liquid mixture;

[0030] The third solid-liquid mixture is centrifuged to obtain a solid product, and the solid product is purified using an ion chromatography column to obtain paiocalcium chloride.

[0031] Furthermore, when the solid product is purified using an ion chromatography column to obtain paeotropic acid, the third eluent used to purify the amide intermediate includes hydrochloric acid.

[0032] Furthermore, the corrosion inhibitor includes one or more of imidazoline, benzimidazole, oleic acid imidazoline, 2-mercaptobenzimidazole, and 2-mercaptobenzothiazole.

[0033] Furthermore, the acidification drainage agent includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, cocamidopropyl betaine, dodecylhydroxysulfobetaine, and cetyltrimethylammonium chloride.

[0034] Furthermore, the stabilizer includes one or more of citric acid, gluconic acid, and sodium erythorbate.

[0035] On the other hand, the present invention discloses a multi-functional acid system for reducing the fracture pressure of muddy reservoirs, which is prepared by the above method. The mass percentage of each component in the multi-functional acid system is as follows: hydrochloric acid 5-10.0%; hydrofluoric acid 5%; multi-functional acid 1.0-3.0%; corrosion inhibitor 3.0-5.0%; acidizing agent 0.5-1.0%; stabilizer 1.0-2.0%; and the balance is water.

[0036] Furthermore, the paiotropic acid of the present invention has the following structure:

[0037]

[0038] The technical effects and advantages of the present invention are as follows:

[0039] 1. The polyfunctional acid of the present invention uses a tetrapod polycarboxylic acid skeleton and has high efficiency and specificity in recognizing metal cations such as silicon ions, magnesium ions, and calcium ions generated during the acidification process of muddy reservoirs.

[0040] 2. The amide group is introduced into the paiotropic acid of the present invention, so that the paiotropic acid has a stronger ability to bind to metal cations.

[0041] 3. The multifunctional acid of the present invention introduces a long-chain alkyl hydrophobic group, which can wrap the cations more tightly, preventing the cations from contacting hydroxide to produce metal hydroxide precipitation and cause reservoir damage.

[0042] 4. The multi-effect acid system of the present invention can reduce the fracture pressure of the reservoir during the fracturing operation.

[0043] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a flow chart of a method for preparing a multi-effect acid system for reducing the fracture pressure of mud-containing reservoirs. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] like Figure 1As shown, the present invention provides a method for preparing a multi-effect acid system for reducing the fracture pressure of muddy reservoirs, comprising the following steps:

[0047] Preparation of paiotropic acid;

[0048] Mixing and stirring hydrochloric acid, hydrofluoric acid and water to obtain a mixed acid solution;

[0049] Adding a corrosion inhibitor, an acidifying drainage agent, a stabilizer and a multi-functional acid to the mixed acid solution and stirring to obtain a multi-functional acid system;

[0050] The mass percentages of the components in the obtained pleiotropic acid system are as follows: hydrochloric acid 5-10.0%, hydrofluoric acid 5%, pleiotropic acid 1.0-3.0%, corrosion inhibitor 3.0-5.0%, acidifying drainage agent 0.5-1.0%, stabilizer 1.0-2.0%, and the balance is water.

[0051] Specifically, the preparation of paiotropic acid includes the following steps:

[0052] S1: tert-butyl bromoacetate, anhydrous acetonitrile, triethylamine and ethylenediamine with alkyl substituents of different lengths are used to prepare amino esters protected by tert-butyloxycarbonyl groups. Triethylamine and ethylenediamine with alkyl substituents of different lengths are added to anhydrous acetonitrile under argon protection and mixed and stirred to obtain a first solution. Tert-butyl bromoacetate is dissolved in anhydrous acetonitrile and added dropwise to the first solution to react. The reaction proceeds slowly and is monitored by thin layer chromatography. After the reaction is completed, the mixture is allowed to stand at room temperature overnight to obtain a yellow first solid-liquid mixture, wherein tert-butyl bromoacetate and the first solid-liquid mixture are separated. The molar ratio of ethylenediamine in the first solution is 3-5:1, and then the first solid-liquid mixture is filtered, and the filter cake is washed with acetonitrile to obtain a first filtrate. The first filtrate is subjected to reduced pressure distillation to obtain a white solid amino ester intermediate, and then the solid amino ester intermediate is purified by column chromatography to obtain an amino ester protected by a tert-butyloxycarbonyl group. The first eluent used to purify the solid amino ester intermediate includes diethyl ether and n-hexane, and the volume ratio of diethyl ether to n-hexane in the first eluent is 1:100. Through this step, the protection of the amino functional group on the ethylenediamine is achieved.

[0053] S2: preparing amides using the amino ester protected by the tert-butoxycarbonyl group prepared in S1, first dissolving the amino ester protected by the tert-butoxycarbonyl group and 2-chloroacetoacetic acid in acetonitrile in a molar ratio of 1:1-2 under argon protection to obtain a second solution, then adding potassium carbonate, potassium iodide and sodium sulfate to the second solution and stirring, reacting under constant temperature reflux, cooling to room temperature after the reaction to obtain a second solid-liquid mixture, then filtering the second solid-liquid mixture to obtain a second filtrate, performing reduced pressure distillation on the second filtrate to obtain an amide intermediate, and finally purifying the amide intermediate by column chromatography to obtain amide, wherein the second eluent used for purifying the amide intermediate comprises ethyl acetate and n-hexane, and the volume ratio of ethyl acetate to n-hexane in the second eluent is 1:1.

[0054] S3: Utilize the amide prepared in S2 to prepare paeotropic acid, first dissolve amide and anisole in dichloromethane in a molar ratio of 1:5-10 and stir to obtain a yellow third solution, then slowly add a certain amount of strong acid to the yellow third solution to remove the protecting group, wherein the strong acid includes trifluoroacetic acid or hydrochloric acid, and then stir under argon protection and room temperature to obtain a fourth solution, and perform vacuum distillation on the fourth solution to remove volatiles and dichloromethane solvent to obtain a residue, and dissolve the residue in dichloromethane and perform vacuum distillation to remove most of the dichloromethane to obtain a concentrated solution, and add ether to the concentrated solution and ultrasonically stir until a white paeotropic acid product appears to obtain a third solid-liquid mixture, and then centrifuge the third solid-liquid mixture to remove the solvent to obtain a solid product, and finally use an ion chromatography column to purify the solid product, vacuum distillate and vacuum dry to obtain paeotropic acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0055] Furthermore, the corrosion inhibitor in the multi-functional acid system includes one or more of imidazoline, benzimidazole, oleic acid imidazoline, 2-mercaptobenzimidazole, and 2-mercaptobenzothiazole.

[0056] Furthermore, the acidifying drainage agent in the multi-functional acid system includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, cocamidopropyl betaine, dodecylhydroxysulfobetaine, and cetyltrimethylammonium chloride.

[0057] Furthermore, the stabilizer in the paiocalcium chloride system includes one or more of citric acid, gluconic acid, and sodium erythorbate.

[0058] In another aspect, the present invention discloses a multi-functional acid system for reducing the fracture pressure of muddy reservoirs, which is prepared using the above method. The weight percentages of the components in the multi-functional acid system are as follows: hydrochloric acid 5-10.0%; hydrofluoric acid 5%; multi-functional acid 1.0-3.0%; corrosion inhibitor 3.0-5.0%; acidizing agent 0.5-1.0%; stabilizer 1.0-2.0%; and the balance is water. The multi-functional acid has the following structure:

[0059]

[0060] Example 1

[0061] A multi-functional acid system for reducing the fracture pressure of muddy reservoirs, wherein the mass content of each component is as follows: 5 parts of hydrochloric acid, 5 parts of hydrofluoric acid, 1 part of multi-functional acid; 3 parts of corrosion inhibitor, 0.5 parts of acidifying and drainage aid, 1 part of stabilizer, and 84.5 parts of water, totaling 100 parts, wherein the corrosion inhibitor is imidazoline, the acidifying and drainage aid is 0.5 parts of fatty alcohol polyoxyethylene ether, and the stabilizer is citric acid.

[0062] S10: Under argon protection, 300 mL of anhydrous acetonitrile and triethylamine (141.7 g, 1.4 mol) were added to a round-bottom flask, and ethylenediamine with alkyl substituents of different lengths was pushed into the solution using an injector and stirred to obtain a first solution. Tert-butyl bromoacetate was dissolved in 50 mL of anhydrous acetonitrile and loaded into a constant pressure low liquid funnel, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine was 3:1. The mixed solution of tert-butyl bromoacetate and anhydrous acetonitrile was slowly added dropwise to the round-bottom flask and stirred. The reaction proceeded slowly and was monitored by thin layer chromatography. The reaction was completed in about 4 hours. After standing at room temperature overnight, a yellow first solid-liquid mixture was generated. The insoluble residue in the first solid-liquid mixture was filtered out, and the filter cake was washed with acetonitrile to obtain a first filtrate. The solvent in the first filtrate was removed by reduced pressure distillation to obtain a white solid amino ester intermediate. Purifying the solid amino ester intermediate by column chromatography to obtain an amino ester, wherein a first eluent used in the purification process comprises diethyl ether and n-hexane, wherein the volume ratio of diethyl ether to n-hexane is 1:100;

[0063] Under argon protection, the amino ester synthesized in the previous step and 2-chloroacetoacetic acid were dissolved in 250 mL of acetonitrile to obtain a second solution, wherein the molar ratio of the amino ester to the 2-chloroacetoacetic acid was 1:1, and then 15 g of potassium carbonate, about 3 g each of potassium iodide and sodium sulfate were added to the second solution and stirred, and the mixture was reacted under constant temperature reflux for 3 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a second solid-liquid mixture, and then the second solid-liquid mixture was filtered to obtain a second filtrate. The second filtrate was subjected to reduced pressure distillation to obtain an amide intermediate, and finally the amide intermediate was purified by column chromatography to obtain an amide, and the second eluent used in the purification process included ethyl acetate and n-hexane, wherein the volume ratio of ethyl acetate to n-hexane was 1:1;

[0064] The Boc (tert-butoxycarbonyl) group-protected amide and anisole synthesized in the previous step are dissolved in 240 mL of dichloromethane and stirred to obtain a yellow third solution, wherein the molar ratio of the Boc (tert-butoxycarbonyl) group-protected amide and anisole is 1:5, and then a certain amount of strong acid (trifluoroacetic acid or hydrochloric acid) is slowly added to the yellow third solution to remove the protecting group, and stirred at room temperature under argon protection to obtain a fourth solution, and the fourth solution is subjected to reduced pressure distillation to remove volatiles and dichloromethane solvent to obtain a residue, and the residue is dissolved in dichloromethane and subjected to reduced pressure distillation to remove most of the dichloromethane to obtain a concentrated solution, and ether is added to the concentrated solution and ultrasonically stirred until a white paso acid product appears to obtain a third solid-liquid mixture, and then the third solid-liquid mixture is centrifuged to remove the solvent to obtain a solid product, and finally the solid product is purified using an ion chromatography column, distilled under reduced pressure and vacuum dried to obtain paso acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0065] S20: Add 5 parts of hydrochloric acid and 5 parts of hydrofluoric acid to 84.5 parts of water and stir for 10 minutes to prepare a conventional mixed acid solution.

[0066] S30: adding 1 part of paiocaltol, 3 parts of imidazoline, 0.5 parts of fatty alcohol polyoxyethylene ether, and 1 part of citric acid to the conventional mixed acid solution prepared in S20 while stirring, and stirring for 30 minutes to obtain a paiocaltol system.

[0067] Example 2

[0068] A multi-functional acid system for reducing the fracture pressure of muddy reservoirs, wherein the mass content of each component is as follows: 7.5 parts of hydrochloric acid, 5 parts of hydrofluoric acid, 2 parts of multi-functional acid; 4 parts of corrosion inhibitor, 0.75 parts of acidizing and drainage agent, 1.5 parts of stabilizer, and 79.25 parts of water, totaling 100 parts, wherein the corrosion inhibitor is benzimidazole, the acidizing and drainage agent is alkylphenol polyoxyethylene ether, and the stabilizer is gluconic acid.

[0069] S10: Under argon protection, 300 mL of anhydrous acetonitrile and triethylamine (141.7 g, 1.4 mol) were added to a round-bottom flask, and ethylenediamine with alkyl substituents of different lengths was pushed into the solution using an injector and stirred to obtain a first solution. Tert-butyl bromoacetate was dissolved in 50 mL of anhydrous acetonitrile and loaded into a constant pressure low liquid funnel, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine was 3:1. The mixed solution of tert-butyl bromoacetate and anhydrous acetonitrile was slowly added dropwise to the round-bottom flask and stirred. The reaction proceeded slowly and was monitored by thin layer chromatography. The reaction was completed in about 4 hours. After standing at room temperature overnight, a yellow first solid-liquid mixture was generated. The insoluble residue in the first solid-liquid mixture was filtered out, and the filter cake was washed with acetonitrile to obtain a first filtrate. The solvent in the first filtrate was removed by reduced pressure distillation to obtain a white solid amino ester intermediate. Purifying the solid amino ester intermediate by column chromatography to obtain an amino ester, wherein a first eluent used in the purification process comprises diethyl ether and n-hexane, wherein the volume ratio of diethyl ether to n-hexane is 1:100;

[0070] Under argon protection, the amino ester synthesized in the previous step and 2-chloroacetoacetic acid were dissolved in 250 mL of acetonitrile to obtain a second solution, wherein the molar ratio of the amino ester to the 2-chloroacetoacetic acid was 1:1, and then 15 g of potassium carbonate, about 3 g each of potassium iodide and sodium sulfate were added to the second solution and stirred, and the mixture was reacted under constant temperature reflux for 3 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a second solid-liquid mixture, and then the second solid-liquid mixture was filtered to obtain a second filtrate. The second filtrate was subjected to reduced pressure distillation to obtain an amide intermediate, and finally the amide intermediate was purified by column chromatography to obtain an amide, and the second eluent used in the purification process included ethyl acetate and n-hexane, wherein the volume ratio of ethyl acetate to n-hexane was 1:1;

[0071] The Boc (tert-butoxycarbonyl) group-protected amide and anisole synthesized in the previous step are dissolved in 240 mL of dichloromethane and stirred to obtain a yellow third solution, wherein the molar ratio of the Boc (tert-butoxycarbonyl) group-protected amide and anisole is 1:5, and then a certain amount of strong acid (trifluoroacetic acid or hydrochloric acid) is slowly added to the yellow third solution to remove the protecting group, and stirred at room temperature under argon protection to obtain a fourth solution, and the fourth solution is subjected to reduced pressure distillation to remove volatiles and dichloromethane solvent to obtain a residue, and the residue is dissolved in dichloromethane and subjected to reduced pressure distillation to remove most of the dichloromethane to obtain a concentrated solution, and ether is added to the concentrated solution and ultrasonically stirred until a white paso acid product appears to obtain a third solid-liquid mixture, and then the third solid-liquid mixture is centrifuged to remove the solvent to obtain a solid product, and finally the solid product is purified using an ion chromatography column, distilled under reduced pressure and vacuum dried to obtain paso acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0072] S20: Add 7.5 parts of hydrochloric acid and 5 parts of hydrofluoric acid to 79.25 parts of water and stir for 10 minutes to prepare a conventional mixed acid solution.

[0073] S30: 2 parts of paicotinic acid, 4 parts of benzimidazole, 0.75 parts of alkylphenol polyoxyethylene ether, and 1.5 parts of gluconic acid were added to the conventional mixed acid solution prepared in S20 while stirring, and stirred for 30 minutes to obtain a paicotinic acid system.

[0074] Example 3

[0075] A multi-functional acid system for reducing the fracture pressure of muddy reservoirs, wherein the weight percentages of the components are as follows: 10 parts of hydrochloric acid, 5 parts of hydrofluoric acid, 3 parts of multi-functional acid; 5 parts of corrosion inhibitor, 1 part of acidizing and drainage aid, 2 parts of stabilizer, and 74 parts of water, for a total of 100 parts, wherein the corrosion inhibitor is 2-mercaptobenzimidazole, the acidizing and drainage aid is hexadecyltrimethylammonium chloride, and the stabilizer is sodium isoascorbate.

[0076] S10: Under argon protection, 300 mL of anhydrous acetonitrile and triethylamine (141.7 g, 1.4 mol) were added to a round-bottom flask, and ethylenediamine with alkyl substituents of different lengths was pushed into the solution using an injector and stirred to obtain a first solution. Tert-butyl bromoacetate was dissolved in 50 mL of anhydrous acetonitrile and loaded into a constant pressure low liquid funnel, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine was 3:1. The mixed solution of tert-butyl bromoacetate and anhydrous acetonitrile was slowly added dropwise to the round-bottom flask and stirred. The reaction proceeded slowly and was monitored by thin layer chromatography. The reaction was completed in about 4 hours. After standing at room temperature overnight, a yellow first solid-liquid mixture was generated. The insoluble residue in the first solid-liquid mixture was filtered out, and the filter cake was washed with acetonitrile to obtain a first filtrate. The solvent in the first filtrate was removed by reduced pressure distillation to obtain a white solid amino ester intermediate. Purifying the solid amino ester intermediate by column chromatography to obtain an amino ester, wherein a first eluent used in the purification process comprises diethyl ether and n-hexane, wherein the volume ratio of diethyl ether to n-hexane is 1:100;

[0077] Under argon protection, the amino ester synthesized in the previous step and 2-chloroacetoacetic acid were dissolved in 250 mL of acetonitrile to obtain a second solution, wherein the molar ratio of the amino ester to the 2-chloroacetoacetic acid was 1:1, and then 15 g of potassium carbonate, about 3 g each of potassium iodide and sodium sulfate were added to the second solution and stirred, and the mixture was reacted under constant temperature reflux for 3 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a second solid-liquid mixture, and then the second solid-liquid mixture was filtered to obtain a second filtrate. The second filtrate was subjected to reduced pressure distillation to obtain an amide intermediate, and finally the amide intermediate was purified by column chromatography to obtain an amide, and the second eluent used in the purification process included ethyl acetate and n-hexane, wherein the volume ratio of ethyl acetate to n-hexane was 1:1;

[0078] The Boc (tert-butoxycarbonyl) group-protected amide and anisole synthesized in the previous step are dissolved in 240 mL of dichloromethane and stirred to obtain a yellow third solution, wherein the molar ratio of the Boc (tert-butoxycarbonyl) group-protected amide and anisole is 1:5, and then a certain amount of strong acid (trifluoroacetic acid or hydrochloric acid) is slowly added to the yellow third solution to remove the protecting group, and stirred at room temperature under argon protection to obtain a fourth solution, and the fourth solution is subjected to reduced pressure distillation to remove volatiles and dichloromethane solvent to obtain a residue, and the residue is dissolved in dichloromethane and subjected to reduced pressure distillation to remove most of the dichloromethane to obtain a concentrated solution, and ether is added to the concentrated solution and ultrasonically stirred until a white paso acid product appears to obtain a third solid-liquid mixture, and then the third solid-liquid mixture is centrifuged to remove the solvent to obtain a solid product, and finally the solid product is purified using an ion chromatography column, distilled under reduced pressure and vacuum dried to obtain paso acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0079] S20: Add 10 parts of hydrochloric acid and 5 parts of hydrofluoric acid to 74 parts of water and stir for 10 minutes to prepare a conventional mixed acid solution.

[0080] S30: 3 parts of paiocaltol, 5 parts of 2-mercaptobenzimidazole, 1 part of hexadecyltrimethylammonium chloride, and 2 parts of sodium isoascorbate were added to the conventional mixed acid solution prepared in S20 while stirring, and stirred for 30 minutes to obtain a paiocaltol system.

[0081] Example 4

[0082] A multi-effect acid system for reducing the fracture pressure of muddy reservoirs, wherein the weight percentages of the components are as follows: 10 parts of hydrochloric acid, 5 parts of hydrofluoric acid, 3 parts of multi-effect acid; 5 parts of corrosion inhibitor, 1 part of acidizing and drainage aid, 2 parts of stabilizer, and 74 parts of water, for a total of 100 parts, wherein the corrosion inhibitor is 2-mercaptobenzothiazole, the acidizing and drainage aid is dodecylhydroxysulfobetaine, and the stabilizer is sodium isoascorbate.

[0083] S10: Under argon protection, 300 mL of anhydrous acetonitrile and triethylamine (141.7 g, 1.4 mol) were added to a round-bottom flask, and ethylenediamine with alkyl substituents of different lengths was pushed into the solution using an injector and stirred to obtain a first solution. Tert-butyl bromoacetate was dissolved in 50 mL of anhydrous acetonitrile and loaded into a constant pressure low liquid funnel, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine was 4:1. The mixed solution of tert-butyl bromoacetate and anhydrous acetonitrile was slowly added dropwise to the round-bottom flask and stirred. The reaction proceeded slowly, and the reaction process was monitored by thin layer chromatography. The reaction was completed in about 4 hours. After standing at room temperature overnight, a yellow first solid-liquid mixture was generated. The insoluble residue in the first solid-liquid mixture was filtered out, and the filter cake was washed with acetonitrile to obtain a first filtrate. The solvent in the first filtrate was removed by reduced pressure distillation to obtain a white solid amino ester intermediate. Purifying the solid amino ester intermediate by column chromatography to obtain an amino ester, wherein a first eluent used in the purification process comprises diethyl ether and n-hexane, wherein the volume ratio of diethyl ether to n-hexane is 1:100;

[0084] Under argon protection, the amino ester synthesized in the previous step and 2-chloroacetoacetic acid were dissolved in 250 mL of acetonitrile to obtain a second solution, wherein the molar ratio of the amino ester to the 2-chloroacetoacetic acid was 1:1.5, and then 15 g of potassium carbonate, about 3 g each of potassium iodide and sodium sulfate were added to the second solution and stirred, and the mixture was reacted under constant temperature reflux for 3 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a second solid-liquid mixture, and then the second solid-liquid mixture was filtered to obtain a second filtrate. The second filtrate was subjected to reduced pressure distillation to obtain an amide intermediate, and finally the amide intermediate was purified by column chromatography to obtain an amide, and the second eluent used in the purification process included ethyl acetate and n-hexane, wherein the volume ratio of ethyl acetate to n-hexane was 1:1;

[0085] The Boc (tert-butoxycarbonyl) group-protected amide and anisole synthesized in the previous step were dissolved in 240 mL of dichloromethane and stirred to obtain a yellow third solution, wherein the molar ratio of the Boc (tert-butoxycarbonyl) group-protected amide and anisole was 1:7.5, and then a certain amount of strong acid (trifluoroacetic acid or hydrochloric acid) was slowly added to the yellow third solution to remove the protecting group, and stirred at room temperature under argon protection to obtain a fourth solution, and the fourth solution was subjected to reduced pressure distillation to remove volatiles and dichloromethane solvent to obtain a residue, and the residue was dissolved in dichloromethane and subjected to reduced pressure distillation to remove most of the dichloromethane to obtain a concentrated solution, and ether was added to the concentrated solution and ultrasonically stirred until a white paso acid product appeared to obtain a third solid-liquid mixture, and then the third solid-liquid mixture was centrifuged to remove the solvent to obtain a solid product, and finally the solid product was purified using an ion chromatography column, distilled under reduced pressure and vacuum dried to obtain paso acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0086] S20: Add 10 parts of hydrochloric acid and 5 parts of hydrofluoric acid to 74 parts of water and stir for 10 minutes to prepare a conventional mixed acid solution.

[0087] S30: 3 parts of paiocaltrine, 5 parts of 2-mercaptobenzothiazole, 1 part of dodecylhydroxysulfobetaine, and 2 parts of sodium isoascorbate were added to the conventional mixed acid solution prepared in S20 while stirring, and stirred for 30 minutes to obtain a paiocaltrine system.

[0088] Example 5

[0089] A multi-functional acid system for reducing the fracture pressure of muddy reservoirs, wherein the weight percentages of the components are as follows: 10 parts of hydrochloric acid, 5 parts of hydrofluoric acid, 3 parts of multi-functional acid; 5 parts of corrosion inhibitor, 1 part of acidizing and drainage aid, 2 parts of stabilizer, and 74 parts of water, for a total of 100 parts, wherein the corrosion inhibitor is oleic imidazoline, the acidizing and drainage aid is cocoamidopropyl betaine, and the stabilizer is citric acid.

[0090] S10: Under argon protection, 300 mL of anhydrous acetonitrile and triethylamine (141.7 g, 1.4 mol) were added to a round-bottom flask, and ethylenediamine with alkyl substituents of different lengths was pushed into the solution using an injector and stirred to obtain a first solution. Tert-butyl bromoacetate was dissolved in 50 mL of anhydrous acetonitrile and loaded into a constant pressure low liquid funnel, wherein the molar ratio of tert-butyl bromoacetate to ethylenediamine was 5:1. The mixed solution of tert-butyl bromoacetate and anhydrous acetonitrile was slowly added dropwise to the round-bottom flask and stirred. The reaction proceeded slowly and was monitored by thin layer chromatography. The reaction was completed in about 4 hours. After standing at room temperature overnight, a yellow first solid-liquid mixture was generated. The insoluble residue in the first solid-liquid mixture was filtered out, and the filter cake was washed with acetonitrile to obtain a first filtrate. The solvent in the first filtrate was removed by reduced pressure distillation to obtain a white solid amino ester intermediate. Purifying the solid amino ester intermediate by column chromatography to obtain an amino ester, wherein a first eluent used in the purification process comprises diethyl ether and n-hexane, wherein the volume ratio of diethyl ether to n-hexane is 1:100;

[0091] Under argon protection, the amino ester synthesized in the previous step and 2-chloroacetoacetic acid were dissolved in 250 mL of acetonitrile to obtain a second solution, wherein the molar ratio of the amino ester to the 2-chloroacetoacetic acid was 1:2, and then 15 g of potassium carbonate, about 3 g of potassium iodide and sodium sulfate were added to the second solution and stirred, and the mixture was reacted under constant temperature reflux for 3 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a second solid-liquid mixture, and then the second solid-liquid mixture was filtered to obtain a second filtrate. The second filtrate was subjected to reduced pressure distillation to obtain an amide intermediate, and finally the amide intermediate was purified by column chromatography to obtain an amide, and the second eluent used in the purification process included ethyl acetate and n-hexane, wherein the volume ratio of ethyl acetate to n-hexane was 1:1;

[0092] The Boc (tert-butoxycarbonyl) group-protected amide and anisole synthesized in the previous step are dissolved in 240 mL of dichloromethane and stirred to obtain a yellow third solution, wherein the molar ratio of the Boc (tert-butoxycarbonyl) group-protected amide and anisole is 1:10, and then a certain amount of strong acid (trifluoroacetic acid or hydrochloric acid) is slowly added to the yellow third solution to remove the protecting group, and stirred at room temperature under argon protection to obtain a fourth solution, and the fourth solution is subjected to reduced pressure distillation to remove volatiles and dichloromethane solvent to obtain a residue, and the residue is dissolved in dichloromethane and subjected to reduced pressure distillation to remove most of the dichloromethane to obtain a concentrated solution, and ether is added to the concentrated solution and ultrasonically stirred until a white paso acid product appears to obtain a third solid-liquid mixture, and then the third solid-liquid mixture is centrifuged to remove the solvent to obtain a solid product, and finally the solid product is purified using an ion chromatography column, distilled under reduced pressure and vacuum dried to obtain paso acid, wherein the third eluent for purifying the amide intermediate includes hydrochloric acid.

[0093] S20: Add 10 parts of hydrochloric acid and 5 parts of hydrofluoric acid to 74 parts of water, stir for 10 minutes, and prepare a conventional mixed acid solution.

[0094] S30: 5 parts of paicotinic acid, 5 parts of oleic imidazoline, 1 part of cocamidopropyl betaine, and 2 parts of citric acid were added to the conventional mixed acid solution prepared in S20 while stirring, and stirred for 30 minutes to obtain a paicotinic acid system.

[0095] The core dissolution rate of mud-bearing bauxite reservoirs with different mud contents was investigated using the multi-effect acid system and other acid systems. The results are shown in Table 1:

[0096] Table 1

[0097]

[0098]

[0099] As shown in Table 1, the multi-effect acid system has a low dissolution rate of 7.4% for bauxite reservoirs; however, it has an excellent dissolution effect on mud-bearing bauxite reservoirs, with a dissolution rate of 56.61%, while other acid systems cannot achieve this effect, which fully demonstrates that the multi-effect acid system is most suitable for mud-bearing reservoirs.

[0100] In a constant temperature water bath at 90°C, the multi-effect acid system of Examples 1-5 was used to carry out a dissolution reaction with the core powder of core sample 2. After 1 hour, the reaction was completed. The acid dissolved the mud in the core powder (mass m1), and the mass of the core powder was reduced to m2. The weight loss of the core powder was measured and the dissolution rate was calculated. The calculation formula is: The results are shown in Table 2:

[0101] Table 2

[0102] <![CDATA[Mass m1 before reaction / g]]> <![CDATA[Mass m2 / g after reaction]]> Dissolution rate Example 1 50.13 23.96 52.2％ Example 2 50.08 23.19 53.7％ Example 3 50.36 22.76 54.8％ Example 4 50.25 55.56 55.1％ Example 5 50.47 19.23 61.9％

[0103] The dissolution rate of the multi-effect acid system prepared in each group of examples on the core powder reached more than 52%, which fully demonstrated that the multi-effect acid system has an excellent dissolution effect on the mud-bearing bauxite reservoir.

[0104] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs, characterized in that: The steps include: Prepare paiotropic acid, which has the following structure: ； mixing and stirring hydrochloric acid, hydrofluoric acid and water to obtain a mixed acid solution; Adding a corrosion inhibitor, an acidifying drainage agent, a stabilizer and the multi-functional acid to the mixed acid solution and stirring to obtain a multi-functional acid system; The mass percentages of the components in the polyfunctional acid system are as follows: hydrochloric acid 5-10.0%; hydrofluoric acid 5%; polyfunctional acid 1.0-3.0%; corrosion inhibitor 3.0-5.0%; acidifying drainage agent 0.5-1.0%; stabilizer 1.0-2.0%; and the balance is water.

2. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 1, characterized in that: The method for preparing paiotropic acid comprises: Preparation of amino esters protected with tert-butyloxycarbonyl groups using tert-butyl bromoacetate, anhydrous acetonitrile, triethylamine, and ethylenediamine with alkyl substituents of varying lengths; preparing an amide using the amino ester protected by the tert-butyloxycarbonyl group; The amide is used to prepare paiotropic acid.

3. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 2, characterized in that: The method of preparing tert-butyloxycarbonyl protected amino esters using tert-butyl bromoacetate, anhydrous acetonitrile, triethylamine and ethylenediamine with alkyl substituents of different lengths comprises: Under argon protection, anhydrous acetonitrile, triethylamine, and ethylenediamine with alkyl substituents of different lengths are mixed and stirred to obtain a first solution; dissolving tert-butyl bromoacetate in anhydrous acetonitrile and adding the first solution dropwise thereto for reaction to obtain a first solid-liquid mixture, wherein the molar ratio of the tert-butyl bromoacetate to the ethylenediamine is 3-5:1; filtering the first solid-liquid mixture to obtain a first filtrate, and performing reduced pressure distillation on the first filtrate to obtain a solid amino ester intermediate; The solid amino ester intermediate is purified by column chromatography to obtain an amino ester protected by a tert-butyloxycarbonyl group.

4. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 3, characterized in that: The method of purifying the solid amino ester intermediate by column chromatography to obtain the amino ester protected by the tert-butyloxycarbonyl group comprises: The first eluent for purifying the solid amino ester intermediate includes diethyl ether and n-hexane, and the volume ratio of the diethyl ether to the n-hexane is 1:

100.

5. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 2, characterized in that: The method of preparing amide using the amino ester protected by the tert-butyloxycarbonyl group comprises: Under argon protection, dissolving the amino ester protected by the tert-butyloxycarbonyl group and 2-chloroacetoacetic acid in acetonitrile at a molar ratio of 1:1-2 to obtain a second solution; adding potassium carbonate, potassium iodide, and sodium sulfate to the second solution and stirring, reacting under constant temperature reflux and cooling to room temperature to obtain a second solid-liquid mixture; filtering the second solid-liquid mixture to obtain a second filtrate, and subjecting the second filtrate to reduced pressure distillation to obtain an amide intermediate; The amide intermediate is purified by column chromatography to obtain amide.

6. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 5, characterized in that: The amide intermediate is purified by column chromatography to obtain an amide, comprising: The second eluent used to purify the amide intermediate includes ethyl acetate and n-hexane, and the volume ratio of ethyl acetate to n-hexane is 1:

1.

7. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 2, characterized in that: The method of preparing paiotropic acid by utilizing the amide comprises: Dissolving the amide and anisole in a molar ratio of 1:5-10 in dichloromethane and stirring to obtain a third solution; adding a strong acid to the third solution and stirring under argon protection at room temperature to obtain a fourth solution, performing reduced pressure distillation on the fourth solution to obtain a residue, dissolving the residue in dichloromethane and performing reduced pressure distillation to obtain a concentrated solution, adding diethyl ether to the concentrated solution and ultrasonically stirring until a white paeotropic acid product appears, thereby obtaining a third solid-liquid mixture; The third solid-liquid mixture is centrifuged to obtain a solid product, and the solid product is purified using an ion chromatography column to obtain paiocalcium chloride.

8. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to claim 7, characterized in that: The method of using an ion chromatography column to purify the solid product to obtain a polyfunctional acid comprises: The third eluent used to purify the amide intermediate includes hydrochloric acid.

9. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to any one of claims 1 to 8, characterized in that: The corrosion inhibitor includes one or more of imidazoline, benzimidazole, oleic acid imidazoline, 2-mercaptobenzimidazole, and 2-mercaptobenzothiazole.

10. The method for preparing a multi-functional acid system for reducing the fracture pressure of muddy reservoirs according to any one of claims 1 to 8, characterized in that: The acidification drainage agent includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, cocamidopropyl betaine, dodecylhydroxysulfobetaine, and cetyltrimethylammonium chloride.

11. The method for preparing a multi-functional acid system for reducing fracture pressure of muddy reservoirs according to any one of claims 1 to 8, characterized in that: The stabilizer includes one or more of citric acid, gluconic acid, and sodium erythorbate.

12. A multi-effect acid system for reducing the fracture pressure of muddy reservoirs, characterized in that: The pleiotropic acid system is prepared by the method according to any one of claims 1 to 11, and the mass percentages of the components in the pleiotropic acid system are as follows: 5-10.0% hydrochloric acid; 5% hydrofluoric acid; 1.0-3.0% pleiotropic acid; 3.0-5.0% corrosion inhibitor; 0.5-1.0% acidizing agent; 1.0-2.0% stabilizer; and the balance is water.

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