Dicarboxyl single-tailed ampholytic surfactant, discharge aiding agent for acidizing and fracturing and preparation method of dual-carboxyl single-tailed ampholytic surfactant

Abstract

The invention relates to the technical field of fracturing fluid additive preparation, discloses a dicarboxyl single-tailed ampholytic surfactant and a preparation method thereof, and further comprises a cleanup additive for acid fracturing and a preparation method thereof. The preparation method comprises the following steps: adding a required amount of dicarboxyl single-tailed ampholytic surfactant, sodium dodecyl benzene sulfonate and a glycosyl nonionic surfactant into a required amount of water, and uniformly stirring. The double-carboxyl single-tailed ampholytic surfactant has the characteristics of simple process, high product yield, biodegradability, safety and reliability, and the discharge aiding agent for acid fracturing obtained by compounding the double-carboxyl single-tailed ampholytic surfactant serving as a raw material with an anionic surfactant and a nonionic surfactant has the advantages of high efficiency, high efficiency and high efficiency. The surface and interfacial tension of the aqueous solution can be effectively reduced, and the industrial use standard of non-fluorocarbon discharge aiding agents is met.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of fracturing fluid additives, and is a dicarboxyl single-tail amphoteric surfactant, a drainage aid for acid fracturing and a preparation method thereof. Background Art

[0002] Acid fracturing transformation technology is an important measure for the efficient development of oil and gas fields. It is the main technical means to achieve the exploration and development of unconventional oil and gas resources, increase and stabilize the production of conventional oil and gas fields, and improve the effect of reservoir transformation. In the process of acid fracturing, it is usually necessary to rely on the formation pressure to quickly discharge the return fluid in the well to the ground. When the formation pressure gradually decreases, the return rate decreases significantly, and the residue in the return fluid will cause blockage after precipitation, resulting in secondary pollution of the formation, which seriously affects the construction efficiency and the effect of acid fracturing transformation. In order to solve the problem of difficulty in returning the return fluid after oil acid fracturing, the use of drainage aids is a conventional method.

[0003] A drainage aid is a type of fracturing fluid additive that can effectively reduce surface tension and interfacial tension, reduce capillary resistance, increase flowback rate and flowback ratio, and thus reduce formation damage. There are many types of drainage aids currently used at home and abroad, but most of them are prepared by compounding fluorocarbon surfactants with other surfactants. Fluorocarbon surfactants have high surface activity and can reduce surface tension to 23mN / m, but they are expensive, difficult to degrade, and have high biological toxicity. In view of this, the development of a green and environmentally friendly drainage agent system has become an urgent problem to be solved. Summary of the invention

[0004] The present invention provides a dicarboxyl single-tail amphoteric surfactant, a drainage aid for acid fracturing and a preparation method thereof, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of the existing fluorocarbon surfactants being difficult to degrade and having high biological toxicity.

[0005] One of the technical solutions of the present invention is achieved by the following measures: a dicarboxyl single-tail amphoteric surfactant, the structural formula of which is as follows:

[0006]

[0007] Wherein, R is an aliphatic hydrocarbon group of C12 to C16.

[0008] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0009] The above-mentioned dicarboxyl single-tail amphoteric surfactant is obtained by the following method:

[0010] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature to obtain a diester intermediate;

[0011] S2, adding bromoalkane to the reaction kettle containing the diester intermediate, heating and refluxing to continue the reaction, to obtain a diester single-tail surfactant;

[0012] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor, continuing the reaction, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0013] In the above step S1, the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.0 to 2.2.

[0014] In the above step S1, the temperature of the reactor is lowered to 0°C to 5°C by ice-water bath, and the reaction time is 22h to 26h.

[0015] In the above step S2, the molar ratio of N,N-dimethyl-1,3-propylenediamine to bromoalkane is 1:1.0 to 1.2.

[0016] In the above step S2, the temperature is raised to 70° C. to 80° C., and the reaction is refluxed for 8 h to 24 h.

[0017] In the above step S3, the pH value of the material in the reactor is adjusted to 6.8 to 7.2, and the reaction is continued for 2h to 6h.

[0018] The second technical solution of the present invention is achieved by the following measures: A method for preparing a dicarboxyl single-tail amphoteric surfactant is carried out according to the following method:

[0019] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature to obtain a diester intermediate;

[0020] S2, adding bromoalkane to the reaction kettle containing the diester intermediate, heating and refluxing to continue the reaction, to obtain a diester single-tail surfactant;

[0021] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor, continuing the reaction, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0022] The following is a further optimization and / or improvement of the second technical solution of the above invention:

[0023] In the above step S1, the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.0 to 2.2.

[0024] In the above step S1, the temperature of the reactor is lowered to 0°C to 5°C by ice-water bath, and the reaction time is 22h to 26h.

[0025] In the above step S2, the molar ratio of N,N-dimethyl-1,3-propylenediamine to bromoalkane is 1:1.0 to 1.2.

[0026] In the above step S2, the temperature is raised to 70° C. to 80° C., and the reaction is refluxed for 8 h to 24 h.

[0027] In the above step S3, the pH value of the material in the reactor is adjusted to 6.8 to 7.2, and the reaction is continued for 2h to 6h.

[0028] The third technical solution of the present invention is achieved by the following measures: a drainage aid for acid fracturing, the raw materials include 8.0% to 9.5% of dicarboxyl single-tail amphoteric surfactant, 0.5% to 1.0% of sodium dodecylbenzene sulfonate, 0.25% to 0.5% of sugar-based nonionic surfactant and the balance of water in weight percentage, and is obtained by the following method: add the required amount of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and sugar-based nonionic surfactant to the required amount of water and stir evenly to obtain the drainage aid for acid fracturing.

[0029] The following is a further optimization and / or improvement of the third technical solution of the above invention:

[0030] The above-mentioned sugar-based anionic surfactant is N-alkylglucamide.

[0031] The fourth technical solution of the present invention is achieved by the following measures: a method for preparing a drainage aid for acid fracturing, wherein the raw materials include 8.0% to 9.5% by weight of a dicarboxyl single-tail amphoteric surfactant, 0.5% to 1.0% by weight of sodium dodecylbenzene sulfonate, 0.25% to 0.5% by weight of a sugar-based nonionic surfactant and the remainder of water, and the method is as follows: add a required amount of a dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and a sugar-based nonionic surfactant to a required amount of water and stir evenly to obtain a drainage aid for acid fracturing.

[0032] The dicarboxyl single-tail amphoteric surfactant of the present invention has the characteristics of simple process, high product yield, biodegradability and safety and reliability. The acid fracturing drainage agent obtained by compounding anionic surfactant and nonionic surfactant with the dicarboxyl single-tail amphoteric surfactant of the present invention as a raw material can effectively reduce the interfacial tension of the aqueous solution, meet the industry use standards of non-fluorocarbon drainage agents, and at the same time, significantly reduce the total amount of surfactant in the drainage agent, thereby reducing the use cost. DETAILED DESCRIPTION

[0033] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0034] The present invention will be further described below in conjunction with embodiments:

[0035] Example 1: The dicarboxyl single-tail amphoteric surfactant has the following structural formula:

[0036]

[0037] Wherein, R is an aliphatic hydrocarbon group of C12 to C16.

[0038] Example 2: As an optimization of the above example, the dicarboxyl single-tail amphoteric surfactant is obtained by the following method:

[0039] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature to obtain a diester intermediate;

[0040] S2, adding bromoalkane to the reaction kettle containing the diester intermediate, heating and refluxing to continue the reaction, to obtain a diester single-tail surfactant;

[0041] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor, continuing the reaction, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0042] The chemical formula for the preparation method of the above-mentioned dicarboxyl single-tail amphoteric surfactant is as follows:

[0043] In step S1, preparation of diester intermediate:

[0044]

[0045] In step S2, preparation of diester single-tail surfactant:

[0046]

[0047] In step S3, preparation of dicarboxylic acid single-tail zwitterionic surfactant:

[0048]

[0049] Example 3: As an optimization of the above example, in step S1, the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.0 to 2.2.

[0050] Example 4: As an optimization of the above example, in step S1, the temperature of the reactor is lowered to 0°C to 5°C by an ice-water bath, and the reaction time is 22h to 26h.

[0051] Example 5: As an optimization of the above example, in step S2, the molar ratio of N,N-dimethyl-1,3-propylenediamine to brominated alkane is 1:1.0 to 1.2.

[0052] Example 6: As an optimization of the above example, in step S2, the temperature is raised to 70°C to 80°C, and the reflux reaction is carried out for 8h to 24h.

[0053] Example 7: As an optimization of the above example, in step S3, the pH value of the material in the reactor is adjusted to 6.8 to 7.2, and the reaction is continued for 2h to 6h.

[0054] Example 8: A drainage aid for acid fracturing obtained by using the dicarboxyl single-tail amphoteric surfactant described in the above example as one of the raw materials, the raw materials comprising, by weight percentage, 8.0% to 9.5% of the dicarboxyl single-tail amphoteric surfactant, 0.5% to 1.0% of sodium dodecylbenzene sulfonate, 0.25% to 0.5% of a sugar-based nonionic surfactant and the remainder of water, and is obtained by the following method: Add the required amounts of the dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and sugar-based nonionic surfactant to the required amount of water and stir evenly to obtain the drainage aid for acid fracturing.

[0055] Example 9: As an optimization of the above example, the sugar-based anionic surfactant is N-alkylglucose amide, and its molecular structure is:

[0056]

[0057] Wherein, R is an aliphatic hydrocarbon group of C12 to C16.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The dicarboxyl single-tail amphoteric surfactant of the present invention is prepared by a "one-pot method", which is simple, has a high product yield, is safe and reliable, and the product is green and biodegradable.

[0060] (2) The dicarboxyl single-tail amphoteric surfactant of the present invention has good composite synergistic characteristics with anionic surfactants and nonionic surfactants, which can effectively reduce the interfacial tension of the aqueous solution surface, and at the same time significantly reduce the total amount of surfactant in the drainage agent, thereby reducing the cost of use.

[0061] Embodiment 10:

[0062] The dicarboxyl single-tail amphoteric surfactant is obtained by the following method:

[0063] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle to 0°C in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature for 22 hours to obtain a diester intermediate; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.0;

[0064] S2, adding hexadecane bromide to the reaction kettle containing the diester intermediate, heating to 70°C, and reflux to continue the reaction for 8 hours to obtain a diester single-tail surfactant; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to hexadecane bromide is 1:1.0;

[0065] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor to 6.8, continuing the reaction for 2 hours, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, recovering the solvent, and adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0066] The acid fracturing drainage agent is obtained by the following method:

[0067] The raw materials include 8.0% of dicarboxyl single-tail amphoteric surfactant, 0.5% of sodium dodecylbenzene sulfonate and 0.25% of N-hexadecyl glucamide and the balance of water by weight percentage, and are obtained by the following method: adding required amounts of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and N-hexadecyl glucamide to a required amount of water and stirring evenly to obtain a drainage agent for acid fracturing.

[0068] Embodiment 11:

[0069] The dicarboxyl single-tail amphoteric surfactant is obtained by the following method:

[0070] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle to 5°C in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature for 26 hours to obtain a diester intermediate; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.2;

[0071] S2, adding tetradecane bromide to the reaction kettle containing the diester intermediate, heating to 80°C, and reflux to continue the reaction for 24 hours to obtain a diester single-tail surfactant; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to tetradecane bromide is 1:1.2;

[0072] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor to 7.2, and continuing the reaction for 6 hours. After the reaction is completed, evaporating and concentrating the reaction product in the reactor, recovering the solvent, and adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0073] The acid fracturing drainage agent is obtained by the following method:

[0074] The raw materials include 9.5% of dicarboxyl single-tail amphoteric surfactant, 1.0% of sodium dodecylbenzene sulfonate, 0.5% of N-tetradecyl glucamide and the balance of water by weight percentage, and are obtained by the following method: adding required amounts of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and N-tetradecyl glucamide to a required amount of water and stirring evenly to obtain a drainage agent for acid fracturing.

[0075] Embodiment 12:

[0076] The dicarboxyl single-tail amphoteric surfactant is obtained by the following method:

[0077] S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle to 2°C in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature for 24 hours to obtain a diester intermediate; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.1;

[0078] S2, adding hexadecane bromide to the reaction kettle containing the diester intermediate, heating to 75°C, and reflux to continue the reaction for 18 hours to obtain a diester single-tail surfactant; wherein the molar ratio of N,N-dimethyl-1,3-propylenediamine to hexadecane bromide is 1:1.1;

[0079] S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor to 7.0, and continuing the reaction for 4 hours. After the reaction is completed, evaporating and concentrating the reaction product in the reactor, recovering the solvent, and adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

[0080] The acid fracturing drainage agent is obtained by the following method:

[0081] The raw materials include 9.0% of dicarboxyl single-tail amphoteric surfactant, 0.8% of sodium dodecylbenzene sulfonate and 0.4% of N-hexadecyl glucamide and the balance of water by weight percentage, and are obtained by the following method: adding required amounts of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and N-hexadecyl glucamide to a required amount of water and stirring evenly to obtain a drainage agent for acid fracturing.

[0082] Embodiment 13:

[0083] Preparation of the dicarboxyl single-tail amphoteric surfactant:

[0084] S1, dissolve 0.1 mol of N,N-dimethyl-1,3-propylenediamine in 100 mL of anhydrous ethanol, stir evenly, lower the temperature by 2°C in an ice-water bath, slowly drop 0.2 mol of methyl acrylate, and continue the reaction for 24 hours after the dropwise addition is complete to obtain a diester intermediate;

[0085] S2, adding 0.1 mol of hexadecane bromide to the diester intermediate, stirring evenly, heating to 80°C, and refluxing for 8 hours to obtain a diester single-tail surfactant;

[0086] S3, slowly add 20% NaOH solution to the diester single-tail surfactant, adjust the pH to 7.0, continue the reaction for 2 hours, rotary evaporate to a small volume, recrystallize with ethyl acetate, and obtain a dicarboxyl single-tail amphoteric surfactant in a viscous liquid state with a yield of 93.6%.

[0087] Preparation of the drainage agent for acid fracturing:

[0088] Weigh 9.0 parts of dicarboxyl single-tail amphoteric surfactant, 0.5 parts of sodium dodecylbenzene sulfonate, 0.25 parts of N-hexadecyl glucose amide and 90.25 parts of water, stir at room temperature, and dissolve evenly to obtain a drainage agent for acid fracturing.

[0089] The performance of the drainage aid for acid fracturing prepared in Example 13 of the present invention was tested. The surface tension of the drainage aid for acid fracturing with a concentration of 0.3% was 23.281 mN / m, and the interfacial tension was 0.109 mN / m, which met the industry use standards for non-fluorocarbon drainage aids.

[0090] Embodiment 14:

[0091] The preparation of the dicarboxyl single-tail amphoteric surfactant is the same as in Example 13;

[0092] Preparation of the drainage agent for acid fracturing:

[0093] Weigh 9.0 parts of dicarboxyl single-tail amphoteric surfactant, 0.5 parts of sodium dodecylbenzene sulfonate, 0.5 parts of N-hexadecyl glucose amide and 90.0 parts of water, stir at room temperature, and dissolve evenly to obtain a drainage agent for acid fracturing.

[0094] The performance of the drainage aid for acid fracturing prepared in Example 14 of the present invention was tested. The surface tension of the drainage aid for acid fracturing with a concentration of 0.3% was 24.058 mN / m, and the interfacial tension was 0.085 mN / m, which met the industry use standards for non-fluorocarbon drainage aids.

[0095] Embodiment 15:

[0096] Preparation of the dicarboxyl single-tail amphoteric surfactant:

[0097] S1, dissolve 0.1 mol of N,N-dimethyl-1,3-propylenediamine in 100 mL of anhydrous ethanol, stir evenly, lower the temperature by 2°C in an ice-water bath, slowly drop 0.22 mol of methyl acrylate, and continue the reaction for 24 hours after the dropwise addition is complete to obtain a diester intermediate;

[0098] S2, add 0.11 mol of tetradecane bromide to the diester intermediate, stir evenly, heat to 80°C, and reflux for 12 hours to obtain a diester single-tail surfactant;

[0099] S3, slowly add 20% NaOH solution to the diester single-tail surfactant, adjust the pH to 7.0, continue the reaction for 2 hours, rotary evaporate to a small volume, recrystallize with ethyl acetate, and obtain a dicarboxyl single-tail amphoteric surfactant in a viscous liquid state with a yield of 94.7%.

[0100] Preparation of the drainage agent for acid fracturing:

[0101] Weigh 9.0 parts of dicarboxyl single-tail amphoteric surfactant, 0.5 parts of sodium dodecylbenzene sulfonate, 0.25 parts of N-tetradecyl glucamide and 90.25 parts of water, stir at room temperature, and dissolve evenly to obtain a drainage aid for acid fracturing.

[0102] The performance of the drainage aid for acid fracturing prepared in Example 15 of the present invention was tested. The surface tension of the drainage aid for acid fracturing with a concentration of 0.3% was 22.605 mN / m, and the interfacial tension was 0.009 mN / m, which met the industry use standards for non-fluorocarbon drainage aids.

[0103] Embodiment 16:

[0104] The preparation of the dicarboxyl single-tail amphoteric surfactant is the same as in Example 15;

[0105] Preparation of the drainage agent for acid fracturing:

[0106] Weigh 8.5 parts of dicarboxyl single-tail amphoteric surfactant, 1.0 part of sodium dodecylbenzene sulfonate, 0.5 part of N-tetradecyl glucose amide and 90.0 parts of water, stir at room temperature, and dissolve evenly to obtain a drainage agent for acid fracturing.

[0107] The performance of the drainage aid for acid fracturing prepared in Example 16 of the present invention was tested. The surface tension of the drainage aid for acid fracturing with a concentration of 0.3% was 23.037 mN / m, and the interfacial tension was 0.161 mN / m, which met the industry use standards for non-fluorocarbon drainage aids.

[0108] In summary, the dicarboxyl single-tail amphoteric surfactant of the present invention has the characteristics of simple process, high product yield, biodegradability and safety and reliability. The acid fracturing drainage agent obtained by compounding anionic surfactant and non-ionic surfactant with the dicarboxyl single-tail amphoteric surfactant of the present invention as a raw material can effectively reduce the interfacial tension of the aqueous solution and meet the industry use standards of non-fluorocarbon drainage agents. At the same time, it can significantly reduce the total amount of surfactant in the drainage agent and reduce the use cost.

[0109] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A dicarboxyl single-tail amphoteric surfactant, characterized in that The structural formula is as follows: Wherein, R is an aliphatic hydrocarbon group of C12 to C16.

2. The dicarboxyl single-tail amphoteric surfactant according to claim 1, characterized in that Obtained as follows: S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature to obtain a diester intermediate; S2, adding bromoalkane to the reaction kettle containing the diester intermediate, heating and refluxing to continue the reaction, to obtain a diester single-tail surfactant; S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor, continuing the reaction, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

3. The dicarboxyl single-tail amphoteric surfactant according to claim 2, characterized in that In step S1, the molar ratio of N,N-dimethyl-1,3-propylenediamine to methyl acrylate is 1:2.0 to 2.2; or / and, in step S1, the temperature of the reactor is lowered to 0°C to 5°C in an ice-water bath, and the reaction time is 22h to 26h.

4. The dicarboxyl single-tail amphoteric surfactant according to claim 2 or 3, characterized in that In step S2, the molar ratio of N,N-dimethyl-1,3-propylenediamine to bromoalkane is 1:1.0 to 1.2; or / and, in step S2, the temperature is raised to 70° C. to 80° C., and the reaction is refluxed for 8 h to 24 h.

5. The dicarboxyl single-tail amphoteric surfactant according to claim 2, 3 or 4, characterized in that In step S3, the pH value of the material in the reactor is adjusted to 6.8 to 7.2, and the reaction is continued for 2 h to 6 h.

6. A method for preparing a dicarboxyl single-tail amphoteric surfactant according to claim 1, 3, 4 or 5, characterized in that Proceed as follows: S1, adding N,N-dimethyl-1,3-propylenediamine to a reaction kettle containing anhydrous ethanol, stirring evenly, lowering the temperature of the reaction kettle in an ice water bath, and then adding methyl acrylate to the reaction kettle, reacting at room temperature to obtain a diester intermediate; S2, adding bromoalkane to the reaction kettle containing the diester intermediate, heating and refluxing to continue the reaction, and obtaining a diester single-tail surfactant; S3, adding sodium hydroxide to the reactor containing the diester single-tail surfactant, adjusting the pH value of the material in the reactor, continuing the reaction, and after the reaction is completed, evaporating and concentrating the reaction product in the reactor, adding ethyl acetate to the obtained concentrate for recrystallization to obtain a dicarboxylic acid single-tail amphoteric surfactant.

7. A drainage aid for acid fracturing prepared using the dicarboxyl single-tail amphoteric surfactant as one of claims 1 to 5 as one of the raw materials, characterized in that The raw materials include 8.0% to 9.5% of dicarboxyl single-tail amphoteric surfactant, 0.5% to 1.0% of sodium dodecylbenzene sulfonate, 0.25% to 0.5% of sugar-based nonionic surfactant and the balance of water in weight percentage, and are obtained by the following method: adding required amounts of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and sugar-based nonionic surfactant to a required amount of water and stirring evenly to obtain a drainage aid for acid fracturing.

8. The drainage aid for acid fracturing according to claim 7, characterized in that The sugar-based anionic surfactant is N-alkylglucamide.

9. A method for preparing a drainage aid for acid fracturing according to claim 8, characterized in that The raw materials include 8.0% to 9.5% of dicarboxyl single-tail amphoteric surfactant, 0.5% to 1.0% of sodium dodecylbenzene sulfonate, 0.25% to 0.5% of sugar-based nonionic surfactant and the balance of water by weight percentage, and are carried out according to the following method: adding required amounts of dicarboxyl single-tail amphoteric surfactant, sodium dodecylbenzene sulfonate and sugar-based nonionic surfactant to a required amount of water and stirring evenly to obtain a drainage agent for acid fracturing.

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