An environmentally friendly composite acid thickener for acid fracturing and preparation method thereof

Abstract

The invention belongs to the technical field of acid fracturing, and specifically relates to an environmentally friendly composite acid liquid thickener for acid fracturing and a preparation method thereof. The acid liquid thickener is prepared from the following raw materials in parts by weight: 80-100 parts of acrylamide; 30-40 parts of functional monomers; 15-20 parts of 2-vinylpiperazine; 10-15 parts of triallyl cyanurate; 5-10 parts of modified starch; 0.03-0.05 parts of a first initiator; 0.03-0.05 parts of a second initiator; 180-200 parts of water; 15-20 parts of a composite emulsifier; 12-15 parts of an inverting agent; 160-180 parts of white oil; the prepared acid liquid thickener has good thickening, high temperature stability, salt resistance and shear resistance, and the polymer molecular chain contains modified starch with good biodegradability. Compared with traditional polymer acid liquid thickeners, it has good environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of acid fracturing, and in particular relates to an environmentally friendly composite acid fluid thickener for acid fracturing and a preparation method thereof. Background Art

[0002] Thickened acid is a type of downhole working fluid used in oil and gas well stimulation operations. It refers to adding a thickener (or thickener, gelling agent, etc.) to an acid (such as hydrochloric acid) to increase the viscosity of the acid, thereby reducing the acid-rock reaction rate and improving the acid's ability to dissolve and communicate with deep formations. Commonly used acid thickeners include natural polymers (such as guar gum, sesbania gum, konjac gum), industrially synthesized polymers (such as modified polyacrylamide, carboxymethyl cellulose and its derivatives), etc. The performance of thickened acid is mainly determined by the thickener, and the molecular weight and structure of the thickener affect the viscosity of the acid. ; After the thickener is dissolved in the acid system, a spatial network structure will be formed, which can greatly increase the apparent viscosity of the system and effectively reduce the diffusion rate of hydrogen ions in the active acid, thereby delaying the reaction rate between the acid and the rock, reducing the consumption rate of the acid, and effectively increasing the action distance of the acid. Therefore, a thickener with strong thickening ability and stable performance can help improve the performance of the thickened acid system; At present, the common polyacrylamide acid thickeners on the market generally have problems such as slow dissolution, weak thickening ability, poor temperature and salt resistance, and poor acid stability, which limits the application of acid thickeners.

[0003] A Chinese patent application with application number CN202211380787.X discloses a cationic acid liquid thickener and a preparation method thereof. The raw materials of the cationic acid liquid thickener include: acrylamide, a cationic polyether hydrophobic monomer, and N-vinyl pyrrolidone. The provided cationic acid liquid thickener contains ethoxy units, hydrophobic long chains and rigid groups, which can effectively solve the technical problems of poor viscosity increasing effect, poor shear resistance and low temperature resistance of traditional acid liquid thickeners.

[0004] A Chinese patent with application number CN202310353554.9 discloses a heat-resistant acid liquid thickener and its preparation method and application. The acid liquid thickener includes acrylamide monomers, ammonium chloride monomers, long-chain alkylamines, functional monomers, tert-butyl 2-bromoisobutyrate, chain extenders, initiators and water. A functional monomer with two carbon-carbon double bonds is introduced, and a primary chain with free double bonds is generated through copolymerization with an acrylamide monomer containing a carbon-carbon double bond, and a star-branched polymer is further formed, thereby improving the temperature resistance and shear resistance of the acid liquid thickener.

[0005] Although the above patents improve the performance of acid liquid thickeners in different ways, the polymerized monomers used all contain cationic monomers, which have problems such as low reactivity rate of cationic monomers and difficulty in controlling the synthesis process, which in turn affect the performance of the acid liquid thickener. Therefore, it is necessary to improve the acid liquid thickener to obtain an acid liquid thickener with good thickening properties, temperature and salt resistance, and good physical and chemical stability. Summary of the invention

[0006] The purpose of the present invention is to provide an environmentally friendly composite acid liquid thickener for acid fracturing and a preparation method thereof in view of the deficiencies in the prior art. The composite acid liquid thickener is formed by polymerization using acrylamide, functional monomers, 2-vinylpiperazine, triallyl cyanurate and modified starch as raw materials. The composite acid liquid thickener has good thickening properties, high temperature stability, salt resistance and shear resistance. The polymer molecular chain contains modified starch with good biodegradability. Compared with traditional polymer acid liquid thickeners, the composite acid liquid thickener has good environmental protection properties.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0008] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 80-100 parts of acrylamide; 30-40 parts of functional monomer; 15-20 parts of 2-vinylpiperazine; 10-15 parts of triallyl cyanurate; 5-10 parts of modified starch; 0.03-0.05 parts of a first initiator; 0.03-0.05 parts of a second initiator; 180-200 parts of water; 15-20 parts of a composite emulsifier; 12-15 parts of an inverting agent; and 160-180 parts of white oil.

[0009] Furthermore, the first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 1.5-2:1; and the second initiator is sodium bisulfite or sodium pyrosulfite.

[0010] Furthermore, the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 2-3:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10 or dodecylphenol polyoxyethylene ether OP-10.

[0011] In the technical solution of the present invention, the preparation method of the modified starch is: adding corn starch to water, dispersing it evenly, adding a modifying compound and potassium carbonate, maintaining the reaction temperature at 50-60°C, stirring the reaction for 6-8h, filtering, washing the solid with water, and drying to obtain the modified starch, wherein the modifying compound is:

[0012] The modified compound used in the method for preparing modified starch is prepared by step (3) in the method for preparing functional monomers.

[0013] Furthermore, the mass ratio of the corn starch, the modified compound and the potassium carbonate is 10:0.1-0.2:0.04-0.05.

[0014] In the technical solution of the present invention, the preparation method of the functional monomer is:

[0015] (1) adding allylamine to dichloromethane, slowly adding epichlorohydrin dropwise, maintaining the reaction temperature at 30-35°C, stirring the reaction for 2-3 hours, adding water for extraction, and concentrating the organic phase under reduced pressure to obtain modified allylamine; the molar ratio of allylamine to epichlorohydrin is 1:1-1.1;

[0016] (2) adding modified allylamine to N,N-dimethylformamide, adding 2,6-difluorobenzyl chloride, potassium iodide and potassium carbonate, stirring evenly, reacting at room temperature for 3-4 hours, adding water and ethyl acetate for extraction, and concentrating the organic phase under reduced pressure to obtain a modified allylamine derivative; the molar ratio of the modified allylamine, 2,6-difluorobenzyl chloride, potassium iodide and potassium carbonate is 1:1-1.1:1.1-1.2:1.1-1.2;

[0017] (3) Add the modified allylamine derivative and N,N'-carbonyldiimidazole to N,N-dimethylformamide, stir and react at room temperature for 5-6 hours, add 10.7 g of sodium p-aminobenzenesulfonate, maintain the reaction temperature at 70-80°C, stir and react for 5-6 hours, add water and ethyl acetate for extraction, and concentrate the aqueous phase under reduced pressure to obtain a modified compound with the structural formula:

[0018] ; The molar ratio of the modified allylamine derivative, N,N'-carbonyldiimidazole, and sodium p-aminobenzenesulfonate is 1:1.1-1.2:1-1.1;

[0019] (4) Add the modified compound and dodecyl dimethyl tertiary amine to ethanol, maintain the reaction temperature at 80°C, reflux for 9-10 hours, remove the ethanol, extract with water and ethyl acetate, and concentrate the aqueous phase under reduced pressure to obtain a functional compound with the structural formula:

[0020] ; The molar ratio of the modified compound and dodecyldimethyl tertiary amine is 1:1-1.1.

[0021] The present invention provides a method for preparing an environmentally friendly composite acid thickener for acid fracturing, which is characterized by comprising the following steps:

[0022] S1, adding acrylamide, functional monomer, 2-vinylpiperazine, triallyl cyanurate, and modified starch into water, mixing evenly, adding the first initiator, stirring evenly, and adjusting the pH value to 4.5-5 to obtain an aqueous phase solution;

[0023] S2, adding the composite emulsifier to the white oil, mixing thoroughly and evenly to obtain an oil phase solution;

[0024] S3, the aqueous solution obtained in step S1 and the oil phase solution obtained in step S2 are mixed evenly, the solution temperature is maintained at 18-20° C., a second initiator is added, and then the reaction temperature is maintained at 50-60° C., the polymerization reaction is carried out for 5-6 hours, an inverting agent is added, and the mixture is stirred evenly to obtain a composite acid liquid thickener.

[0025] The present invention also provides an environmentally friendly composite thickening acid, comprising the environmentally friendly composite acid liquid thickener for acid fracturing as described above; and also comprising hydrochloric acid, a clay stabilizer, an iron ion stabilizer, a corrosion inhibitor, and the like.

[0026] The present invention has the following beneficial effects:

[0027] In order to obtain an acid liquid thickener with good comprehensive performance, the present invention modifies the raw materials for polymerizing to form the thickener. On the one hand, -OH contained in the molecular chain of corn starch is reacted with -Cl in the structure of the modified compound, and the modified compound is grafted onto the molecular chain of corn starch to obtain modified starch. The allyl group can polymerize with -OH of the starch molecular chain under the action of a composite initiator and other monomers to form a denser and more stable network structure, thereby achieving a viscosity-increasing effect and improving the thermal stability and shear resistance of the polymer. On the other hand, the present invention uses a functional monomer for the preparation of the acid liquid thickener. The functional monomer is a zwitterionic compound with the same total amount of positive and negative charges. In the polymerization process, the functional monomer has better stability. The benzenesulfonic acid group contained in the functional monomer can synergistically improve the heat and salt resistance of the polymer. The difluorophenyl with strong hydrophobic effect, the long-chain alkane with hydrophobic effect and the difluorophenyl with strong hydrophobic effect contained in the modified starch in the functional monomer structure enhance the hydrophobic association within and between polymer molecules, improve the rigidity of the molecular chain, and thus improve the thermal stability and shear resistance of the polymer.

[0028] The invention uses acrylamide, functional monomers, 2-vinylpiperazine, triallyl cyanurate and modified starch as raw materials, and polymerizes to form a composite acid liquid thickener, which has good thickening properties, high temperature stability, salt resistance and shear resistance. The polymer molecular chain contains modified starch with good biodegradability. Compared with traditional polymer acid liquid thickeners, it has good environmental protection. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] In the technical solution of the present invention, the chemical reagents used are all commonly available on the market.

[0031] In the technical solution of the present invention, the preparation method of the functional monomer is:

[0032] (1) Add 5.7 g of allylamine to 500 mL of dichloromethane, slowly dropwise add 9.2 g of epichlorohydrin, maintain the reaction temperature at 35°C, stir and react for 3 h, add water for extraction, and concentrate the organic phase under reduced pressure to obtain 12.8 g of modified allylamine; the molar ratio of allylamine to epichlorohydrin is 1:1; the reaction process is:

[0033] ;

[0034] Modified allylamine: ESI (m / z): 150.6 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 5.85-5.88 (m, 1H), 5.52 (s, 1H), 5.37 (s, 1H), 5.17-5. 19 (m, 2H), 3.72-3.76 (m, 2H), 3.25-3.28 (m, 3H), 2.81-2.84 (m, 1H), 2.56-2.58 (m, 1H).

[0035] (2) Add 12.0 g of modified allylamine to 400 mL of N,N-dimethylformamide, add 13.0 g of 2,6-difluorobenzyl chloride, 14.6 g of potassium iodide, and 12.2 g of potassium carbonate, stir evenly, react at room temperature for 4 h, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain 18.6 g of modified allylamine derivative; the molar ratio of modified allylamine, 2,6-difluorobenzyl chloride, potassium iodide, and potassium carbonate is 1:1:1.1:1.1; the reaction process is:

[0036] ;

[0037] Modified allylamine derivative: ESI (m / z): 276.7 [M+H] + , 1H-NMR (600MHz, DMSO-d6, δppm): 7.74-7.78 (m, 1H), 7.40 (t, J=8.2Hz, 2H), 5.83-5.85 (m, 1H), 5.37 (s, 1H), 5.1 5-5.19 (m, 2H), 3.75-3.79 (m, 4H), 3.38-3.40 (m, 1H), 3.03-3.06 (m, 2H), 2.62-2.65 (m, 1H), 2.37-2.40 (m, 1H).

[0038] (3) 15.0 g of modified allylamine derivative and 9.7 g of N,N'-carbonyldiimidazole (CDI) were added to 250 mL of N,N-dimethylformamide, and the mixture was stirred at room temperature for 6 h. 10.7 g of sodium p-aminobenzenesulfonate was added, and the reaction temperature was maintained at 80°C. The mixture was stirred for 5 h. Water and ethyl acetate were added for extraction. The aqueous phase was concentrated under reduced pressure to obtain 22.4 g of modified compound. The molar ratio of modified allylamine derivative, N,N'-carbonyldiimidazole and sodium p-aminobenzenesulfonate was 1:1.1:1. The reaction process was as follows:

[0039] ;

[0040] Modified compound: ESI (m / z): 497.8 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 9.88 (s, 1H), 7.74-7.78 (m, 3H), 7.54 (d, J=8.6Hz, 2H), 7.40 (t, J=8.2Hz, 2H), 5.84-5.87 (m, 1H), 5. 15-5.20 (m, 2H), 4.93-4.97 (m, 1H), 3.65-3.70 (m, 3H), 3.45-3.50 (m, 1H), 3.03-3.05 (m, 2H), 2.71-2.75 (m, 1H), 2.46-2.49 (m, 1H).

[0041] (4) 20.0 g of the modified compound and 8.6 g of dodecyl dimethyl tertiary amine were added to 200 mL of ethanol, the reaction temperature was maintained at 80°C, and the reaction was refluxed for 10 h. The ethanol was removed, and the mixture was extracted with water and ethyl acetate. The aqueous phase was concentrated under reduced pressure to obtain 20.8 g of the functional compound. The molar ratio of the modified compound to dodecyl dimethyl tertiary amine was 1:1. The reaction process was as follows:

[0042] ;

[0043] Functional compound: ESI (m / z): 652.8 [M+H] + , 1H-NMR (600MHz, DMSO-d6, δppm): 9.88 (s, 1H), 7.90 (d, J=8.6Hz, 2H), 7.74-7.78 (m, 3H ), 7.40 (t, J=8.2Hz, 2H), 5.85-5.89 (m, 1H), 5.14-5.20 (m, 2H), 5.24-5.27 (m, 1H), 3. 59-3.62 (m, 3H), 3.30-3.36 (m, 7H), 3.22-3.27 (m, 2H), 3.02-3.05 (m, 2H), 2.71-2.74 (m, 1H), 2.46-2.50 (m, 1H), 1.71-1.76 (m, 2H), 1.25-1.29 (m, 18H), 0.88-0.92 (m, 3H).

[0044] The invention uses allylamine as a raw material, and sequentially reacts with epichlorohydrin, 2,6-difluorobenzyl chloride and sodium p-aminobenzenesulfonate to obtain a modified compound containing an allyl group, a difluorophenyl group with a strong hydrophobic effect and a benzenesulfonic acid group with heat and salt resistance in the structure; then the modified compound is reacted with dodecyldimethyl tertiary amine to obtain a functional monomer containing an allyl group, a difluorophenyl group with a strong hydrophobic effect, a long-chain alkane with a hydrophobic effect and a benzenesulfonic acid group with heat and salt resistance in the structure. Example 1

[0045] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 100 parts of acrylamide; 40 parts of functional monomer; 18 parts of 2-vinylpiperazine; 15 parts of triallyl cyanurate; 10 parts of modified starch; 0.05 parts of a first initiator; 0.05 parts of a second initiator; 200 parts of water; 20 parts of a composite emulsifier; 14 parts of an inverting agent; 180 parts of white oil;

[0046] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 2:1; the second initiator is sodium bisulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 3:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10.

[0047] The preparation method of modified starch is as follows: corn starch is added to water, dispersed evenly, a modified compound and potassium carbonate are added, the reaction temperature is maintained at 60°C, the reaction is stirred for 7 hours, filtered, the solid is washed with water, and dried to obtain modified starch; the mass ratio of corn starch, modified compound and potassium carbonate is 10:0.2:0.05, and the amount of water used is 15 times the mass of corn starch.

[0048] A method for preparing an environmentally friendly composite acid thickener for acid fracturing comprises the following steps:

[0049] S1, adding acrylamide, functional monomer, 2-vinylpiperazine, triallyl cyanurate, and modified starch into water, mixing evenly, adding the first initiator, stirring evenly, and adjusting the pH value to 5 to obtain an aqueous phase solution;

[0050] S2, adding the composite emulsifier to the white oil, mixing thoroughly and evenly to obtain an oil phase solution;

[0051] S3, the aqueous solution obtained in step S1 and the oil phase solution obtained in step S2 are mixed evenly, the solution temperature is maintained at 20° C., a second initiator is added, and then the reaction temperature is maintained at 60° C., the polymerization reaction is carried out for 6 hours, an inverting agent is added, and the mixture is stirred evenly to obtain a composite acid liquid thickener. Example 2

[0052] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 90 parts of acrylamide; 35 parts of functional monomer; 20 parts of 2-vinylpiperazine; 10 parts of triallyl cyanurate; 8 parts of modified starch; 0.04 parts of a first initiator; 0.04 parts of a second initiator; 190 parts of water; 18 parts of a composite emulsifier; 15 parts of an inverting agent; and 170 parts of white oil.

[0053] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 1.5:1; the second initiator is sodium pyrosulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 2:1; and the reverse agent is dodecylphenol polyoxyethylene ether OP-10.

[0054] The preparation method of modified starch is as follows: corn starch is added to water, dispersed evenly, a modified compound and potassium carbonate are added, the reaction temperature is maintained at 55° C., the reaction is stirred for 8 hours, filtered, the solid is washed with water, and dried to obtain modified starch; the mass ratio of corn starch, modified compound and potassium carbonate is 10:0.15:0.04, and the amount of water used is 15 times the mass of corn starch.

[0055] A method for preparing an environmentally friendly composite acid thickener for acid fracturing comprises the following steps:

[0056] S1, adding acrylamide, functional monomer, 2-vinylpiperazine, triallyl cyanurate, and modified starch into water, mixing evenly, adding the first initiator, stirring evenly, and adjusting the pH value to 4.5 to obtain an aqueous phase solution;

[0057] S2, adding the composite emulsifier to the white oil, mixing thoroughly and evenly to obtain an oil phase solution;

[0058] S3, the aqueous solution obtained in step S1 and the oil solution obtained in step S2 are mixed evenly, the solution temperature is maintained at 18° C., a second initiator is added, and then the reaction temperature is maintained at 55° C., the polymerization reaction is carried out for 5 hours, an inverting agent is added, and the mixture is stirred evenly to obtain a composite acid liquid thickener. Example 3

[0059] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener is prepared from the following raw materials in parts by weight: 80 parts of acrylamide; 30 parts of functional monomer; 15 parts of 2-vinylpiperazine; 12 parts of triallyl cyanurate; 5 parts of modified starch; 0.03 parts of a first initiator; 0.03 parts of a second initiator; 180 parts of water; 15 parts of a composite emulsifier; 12 parts of an inverting agent; 160 parts of white oil;

[0060] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 1.8:1; the second initiator is sodium pyrosulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 2.5:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10.

[0061] The preparation method of modified starch is as follows: corn starch is added to water, dispersed evenly, a modified compound and potassium carbonate are added, the reaction temperature is maintained at 50° C., the reaction is stirred for 6 hours, filtered, the solid is washed with water, and dried to obtain modified starch; the mass ratio of corn starch, modified compound and potassium carbonate is 10:0.1:0.045, and the amount of water used is 15 times the mass of corn starch.

[0062] A method for preparing an environmentally friendly composite acid thickener for acid fracturing comprises the following steps:

[0063] S1, adding acrylamide, functional monomer, 2-vinylpiperazine, triallyl cyanurate, and modified starch into water, mixing evenly, adding the first initiator, stirring evenly, and adjusting the pH value to 4.8 to obtain an aqueous phase solution;

[0064] S2, adding the composite emulsifier to the white oil, mixing thoroughly and evenly to obtain an oil phase solution;

[0065] S3. Evenly mix the aqueous solution obtained in step S1 and the oil solution obtained in step S2, maintain the solution temperature at 19° C., add the second initiator, and then maintain the reaction temperature at 50° C., perform the polymerization reaction for 5.5 hours, add an inverting agent, stir evenly, and obtain a composite acid liquid thickener. Example 4

[0066] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 90 parts of acrylamide; 30 parts of functional monomer; 16 parts of 2-vinylpiperazine; 13 parts of triallyl cyanurate; 7 parts of modified starch; 0.03 parts of a first initiator; 0.03 parts of a second initiator; 190 parts of water; 17 parts of a composite emulsifier; 15 parts of an inverting agent; and 180 parts of white oil.

[0067] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 1.5:1; the second initiator is sodium bisulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 3:1; and the reverse agent is dodecylphenol polyoxyethylene ether OP-10.

[0068] The preparation method of modified starch is as follows: adding corn starch to water, dispersing evenly, adding modified compounds and potassium carbonate, maintaining the reaction temperature at 60°C, stirring the reaction for 8 hours, filtering, washing the solid with water, and drying to obtain modified starch; the mass ratio of corn starch, modified compound, and potassium carbonate is 10:0.1:0.05, and the amount of water used is 15 times the mass of corn starch.

[0069] The preparation method of an environmentally friendly composite acid fluid thickener for acid fracturing is the same as that in Example 1.

[0070] Comparative Example 1

[0071] Compared with Example 1, this comparative example replaces the modified starch with corn starch.

[0072] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 100 parts of acrylamide; 40 parts of functional monomer; 18 parts of 2-vinylpiperazine; 15 parts of triallyl cyanurate; 10 parts of corn starch; 0.05 parts of a first initiator; 0.05 parts of a second initiator; 200 parts of water; 20 parts of a composite emulsifier; 14 parts of an inverting agent; 180 parts of white oil;

[0073] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 2:1; the second initiator is sodium bisulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 3:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10.

[0074] The preparation method of an environmentally friendly composite acid fluid thickener for acid fracturing is the same as that in Example 1.

[0075] Comparative Example 2

[0076] Compared with Example 1, the raw materials in this comparative example do not contain functional monomers.

[0077] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 100 parts of acrylamide; 18 parts of 2-vinylpiperazine; 15 parts of triallyl cyanurate; 10 parts of modified starch; 0.05 parts of a first initiator; 0.05 parts of a second initiator; 200 parts of water; 20 parts of a composite emulsifier; 14 parts of an inverting agent; and 180 parts of white oil.

[0078] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 2:1; the second initiator is sodium bisulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 3:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10.

[0079] The preparation methods of modified starch and composite acid liquid thickener are the same as those in Example 1.

[0080] Comparative Example 3

[0081] Compared with Example 1, this comparative example replaces the modified starch with corn starch, and the raw material does not contain functional monomers.

[0082] An environmentally friendly composite acid thickener for acid fracturing, the acid thickener being prepared from the following raw materials in parts by weight: 100 parts of acrylamide; 18 parts of 2-vinylpiperazine; 15 parts of triallyl cyanurate; 10 parts of corn starch; 0.05 parts of a first initiator; 0.05 parts of a second initiator; 200 parts of water; 20 parts of a composite emulsifier; 14 parts of an inverting agent; and 180 parts of white oil.

[0083] The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 2:1; the second initiator is sodium bisulfite; the composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 3:1; and the reverse agent is nonylphenol polyoxyethylene ether NP-10.

[0084] The preparation method of an environmentally friendly composite acid fluid thickener for acid fracturing is the same as that in Example 1.

[0085] Performance Testing

[0086] Weigh 8g of the acid thickener prepared in Examples 1-4 and Comparative Examples 1-3, respectively, and slowly add them to 792mL of a 20% hydrochloric acid solution or a saline solution with a mineralization degree of 20000mg / L (the total amount of calcium and magnesium ions is 1572mg / L, and the mass fraction of hydrochloric acid is 20%), the addition time is less than 20s, and stirring is stopped after there is no insoluble matter and the phase is homogeneous, and the stirring is covered, and the mixture is allowed to stand at 30°C for 4h to allow it to fully swell to prepare a thickened acid, and the thickened acid is immediately measured at 170s by a six-speed viscometer. -1The shear rate, apparent viscosity η0 at 30°C and apparent viscosity η1 of the brine were recorded, and the dissolution time of the acid thickener in the hydrochloric acid solution was recorded; the thickened acid (hydrochloric acid solution) was allowed to stand at 120°C for 6 hours, cooled to 30°C, and the stability of the thickened acid was observed to determine whether it was precipitated or stratified, and the six-speed viscometer was used to measure the thickened acid at 170s -1 Shear rate, apparent viscosity η2 at 30°C, calculated viscosity retention rate = η2 / η0×100%; the results are shown in Table 1 below.

[0087] Table 1

[0088]

[0089] From the results in Table 1, it can be seen that the acid thickeners prepared in Examples 1-4 of the present invention are used in thickening acid. -1 The shear rate and the apparent viscosity at 30°C reach more than 75 mPa·s, the apparent viscosity of the brine reaches more than 69%, the viscosity retention rate at high temperature is more than 91%, and there is no stratification and precipitation, indicating that it has good thickening, high temperature stability, salt resistance and shear resistance. Compared with Comparative Examples 1-3, the modified starch grafted with a modified compound, the functional monomer and other raw materials are polymerized in Example 1 of the present invention, indicating that the two can work synergistically to improve the thermal stability, shear resistance and temperature and salt resistance of the polymer molecular chain.

[0090] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or device; although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly composite acid thickener for acid fracturing, It is characterized in that The acid liquid thickener is prepared from the following raw materials in parts by weight: 80-100 parts of acrylamide; 30-40 parts of functional monomer; 15-20 parts of 2-vinylpiperazine; 10-15 parts of triallyl cyanurate; 5-10 parts of modified starch; 0.03-0.05 parts of the first initiator; 0.03-0.05 parts of the second initiator; 180-200 parts of water; and 15-20 parts of a composite emulsifier. 12-15 parts of reverse agent; 160-180 parts of white oil; The functional monomers are: ； The preparation method of the modified starch is as follows: adding corn starch to water, dispersing it evenly, adding a modified compound and potassium carbonate, maintaining the reaction temperature at 50-60° C., stirring the reaction for 6-8 hours, filtering, washing the solid with water, and drying to obtain the modified starch; The modified compound is: 。 2. An environmentally friendly composite acid thickener for acid fracturing according to claim 1, It is characterized in that The preparation method of the functional monomer is: (1) Add allylamine to dichloromethane, slowly add epichlorohydrin, maintain the reaction temperature at 30-35°C, stir and react for 2-3 hours, add water for extraction, and concentrate the organic phase under reduced pressure to obtain modified allylamine; (2) Add the modified allylamine to N,N-dimethylformamide, add 2,6-difluorobenzyl chloride, potassium iodide, and potassium carbonate, stir evenly, react at room temperature for 3-4 hours, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain the modified allylamine derivative; (3) Add the modified allylamine derivative and N,N'-carbonyldiimidazole to N,N-dimethylformamide, stir and react at room temperature for 5-6 hours, add 10.7 g of sodium p-aminobenzenesulfonate, maintain the reaction temperature at 70-80°C, stir and react for 5-6 hours, add water and ethyl acetate for extraction, and concentrate the aqueous phase under reduced pressure to obtain the modified compound; (4) Add the modified compound and dodecyl dimethyl tertiary amine to ethanol, maintain the reaction temperature at 80°C, reflux for 9-10 hours, remove the ethanol, extract with water and ethyl acetate, and concentrate the aqueous phase under reduced pressure to obtain the functional compound.

3. An environmentally friendly composite acid thickener for acid fracturing according to claim 2, It is characterized in that The molar ratio of allylamine to epichlorohydrin in step (1) is 1:1-1.1; the molar ratio of modified allylamine, 2,6-difluorobenzyl chloride, potassium iodide and potassium carbonate in step (2) is 1:1-1.1:1.1-1.2:1.1-1.

2.

4. The environmentally friendly composite acid thickener for acid fracturing according to claim 2, It is characterized in that The molar ratio of the modified allylamine derivative, N,N'-carbonyldiimidazole and sodium p-aminobenzenesulfonate in step (3) is 1:1.1-1.2:1-1.1; the molar ratio of the modified compound and dodecyldimethyl tertiary amine in step (4) is 1:1-1.

1.

5. The environmentally friendly composite acid thickener for acid fracturing according to claim 1, It is characterized in that In the preparation method of modified starch, the mass ratio of corn starch, modified compound and potassium carbonate is 10:0.1-0.2:0.04-0.

05.

6. The environmentally friendly composite acid thickener for acid fracturing according to claim 1, It is characterized in that The first initiator is composed of azobisisobutyronitrile and ammonium persulfate in a mass ratio of 1.5-2:1; the second initiator is sodium bisulfite or sodium pyrosulfite.

7. The environmentally friendly composite acid thickener for acid fracturing according to claim 1, It is characterized in that The composite emulsifier is composed of Span 80 and Tween 80 in a mass ratio of 2-3:1; the reverse agent is nonylphenol polyoxyethylene ether NP-10 or dodecylphenol polyoxyethylene ether OP-10.

8. A method for preparing an environmentally friendly composite acid thickener for acid fracturing according to any one of claims 1 to 7, It is characterized in that The steps include: S1, adding acrylamide, functional monomer, 2-vinylpiperazine, triallyl cyanurate, and modified starch into water, mixing evenly, adding the first initiator, stirring evenly, and adjusting the pH value to 4.5-5 to obtain an aqueous phase solution; S2, adding the composite emulsifier to the white oil, mixing thoroughly and evenly to obtain an oil phase solution; S3, the aqueous solution obtained in step S1 and the oil phase solution obtained in step S2 are mixed evenly, the solution temperature is maintained at 18-20° C., a second initiator is added, and then the reaction temperature is maintained at 50-60° C., the polymerization reaction is carried out for 5-6 hours, an inverting agent is added, and the mixture is stirred evenly to obtain a composite acid liquid thickener.

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