VISCOELASTIC SURFACTANTS FOR SELF-DIVERTING ACID UNDER HIGH TEMPERATURE AND PREPARATION METHOD

Abstract

A viscoelastic surfactant (VES) for a self-diverting acid under high temperature has a structural formula shown as formula (I), wherein, n is saturated hydrocarbon with 2 to 8 carbon atoms; R.sub.1 is saturated or unsaturated hydrocarbon with 18 to 28 carbon atoms; R.sub.2 and R.sub.3 are independently methyl, ethyl or hydrogen, and R.sub.2 and R.sub.3 can be the same or different; and X.sup.− is any one of Cl.sup.−, Br.sup.−, CO.sub.3.sup.2−, SO.sub.4.sup.2−, HCOO.sup.− and CH.sub.3COO.sup.−. The method for preparing the surfactant includes subjecting a fatty acid and an organic amine to acid-amine condensation to obtain an intermediate. The intermediate reacts with a metal hydride to obtain a fatty amine. Then, an acid solution is used to protonate the fatty amine to obtain an ultra-long-chain viscoelastic cationic surfactant. The present invention also provides use of the surfactant as a thickener for a self-diverting acid.

Claims

1. A viscoelastic surfactant (VES) for a self-diverting acid under high temperature, wherein, the VES has the following structural formula: ##STR00003## wherein, n is saturated hydrocarbon with 2 to 8 carbon atoms; R.sub.1 is saturated alkyl or cis-22 carbon-9-alkenyl or cis-24 carbon-15-alkenyl with 18 to 28 carbon atoms; R.sub.2 and R.sub.3 are independently methyl, ethyl or hydrogen, and R.sub.2 and R.sub.3 can be the same or different; X.sup.− is any one of Cl.sup.−, Br.sup.−, F.sup.−, HCOO.sup.− and CH.sub.3COO.sup.−; and X.sup.2− is any one of CO.sub.3.sup.2−, SO.sub.4.sup.2.

2. A preparation method for preparing the VES for the self-diverting acid under high temperature according to claim 1, comprising the following steps: S1: adding a fatty acid and an organic amine to a reactor to form a S1 mixture, and heating the S1 mixture to 160° C. to 170° C.; conducting a S1 reaction for 11 h to 13 h and then stopping the S1 reaction to obtain a S1 reaction solution; pouring the S1 reaction solution into a cold acetone solution after the S1 reaction solution is cooled to 25° C. to 35° C., and stirring a resulting solution; then conducting a filtration to obtain a solid, and washing the solid obtained 2 to 3 times with acetone; and conducting lyophilization to obtain a white solid intermediate; wherein the organic amine and the fatty acid are used at a molar ratio of (1.1-15):1; S2: dissolving the white solid intermediate in tetrahydrofuran (THF) to obtain an intermediate solution, and adding the intermediate solution dropwise to a solution of a metal hydride in THF at 0° C. to 5° C. to form a S2 solution; heating the S2 solution to 65° C. to 85°C., and conducting a S2 reaction for 24 h to 36 h to obtain a S2 reaction solution; adding deionized water, a NaOH solution with a mass concentration of 10% to 20% and deionized water in sequence to the S2 reaction solution after the S2 reaction is completed; then conducting a first filtration, drying a first filtrate, and conducting a second filtration for the first filtrate; and removing solvent from a second filtrate obtained in the second filtration to obtain a fatty amine; wherein, the white solid intermediate and the metal hydride are used at a molar ratio of 1:(2.0-2.5); and the deionized water is added a first time to quench the metal hydride, then the NaOH solution is added to remove metal ions, and then the deionized water is added a second time to ensure that the metal hydride is completely quenched; and S3: mixing the fatty amine with an acid solution having a mass concentration of 10% to 20% to obtain a S3 solution, and thoroughly stirring the S3 solution to protonate the fatty amine, namely, to form a VES, wherein the fatty amine has a molar ratio of 1:2 with hydrogen ions in the acid solution.

3. The preparation method according to claim 2, wherein the fatty acid is a combination of at least one or more of saturated or unsaturated fatty acids having 18 to 28 carbon atoms.

4. The preparation method according to claim 2, wherein the organic amine comprises a combination of one or more of N,N-dimethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-dimethyl-1,4-butanediamine, N,N-diethylethylenediamine, N,N-diethyl-1,3-propanediamine, ethylenediamine, propanediamine, butanediamine, pentanediamine, hexamethylenediamine, heptanediamine and octanediamine.

5. The preparation method according to claim 2, wherein the metal hydride comprises a combination of one or more of LiAlH.sub.4, LiBH.sub.4 and NaBH.sub.4.

6. The preparation method according to claim 2, wherein the acid solution comprises a combination of one or more of a HCl solution, a HBr solution, a HF solution, a H.sub.2SO.sub.4 solution, a H.sub.2CO.sub.3 solution, a HCOOH solution and a CH.sub.3COOH solution.

7. The preparation method according to claim 2, wherein, during the S1 reaction, circulating water cooling is continuously conducted to have the organic amine refluxed.

8. A method of using the VES of claim 1, comprising a step of using the VES as a thickener.

9. The method according to claim 8, comprising a step of mixing the VES with an acid solution having a mass concentration of 10% to 20%. wherein the acid solution having the mass concentration of 10% to 20% comprises a combination of one or more of a HCl solution, a HBr solution, a HF solution, a H.sub.2SO.sub.4 solution, a H.sub.2CO.sub.3 solution, a HCOOH solution and a CH.sub.3COOH solution, and the acid solution having the mass concentration of 10% to 20% is used at an amount allowing the VES as the thickening agent to have a mass concentration of 1% to 3% in an obtained viscous acid solution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a .sup.1H NMR spectrum for N-(cis-docosa-9-alkenyl-amidopropyl)-N,N-dimethyl tertiary amine.

[0034] FIG. 2 is a .sup.1H NMR spectrum for N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine.

[0035] FIG. 3 is a .sup.1H NMR spectrum for N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride.

[0036] FIG. 4 is a mass spectrum for N-(cis-docosa-9-alkenyl-aminopropyl-N,N-dimethyl tertiary amine hydrochloride.

[0037] FIG. 5 shows the theological behavior of a 3.0% N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine sulfate solution in a 10% H.sub.2SO.sub.4 solution at 150° C.

[0038] FIG. 6 shows the theological behavior of a 1.0% N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride solution in a 20% HCl solution at 150° C.

[0039] FIG. 7 is a mass spectrum for N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride that has been tested at 150° C. for viscosity.

[0040] FIG. 8 shows the acid-rock reaction kinetic curve for a 3.0% N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride solution in a 20% HCl solution at 150° C.

[0041] FIG. 9 shows contrast images of a Xinjiang outcrop before and after an acid-rock reaction.

[0042] FIG. 10 is a plot showing the viscosity of N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride that changes with the varying contents of HCl and CaCl.sub.2 in the acid solution at 150° C.

[0043] FIG. 11 is a .sup.1H NMR spectrum for N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine.

[0044] FIG. 12 shows the rheological behavior of a 3.0% N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine hydrochloride solution in a 10% HCl solution at 150° C.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The technical solution in the present invention will be clearly and completely described below in conjunction with examples. The described examples are merely some rather than all of the examples of the present invention. All other examples obtained by those skilled in the art based on the examples of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] As shown in FIGS. 1 to 12, a VES for a self-diverting acid under high temperature is provided, with the following structural formula:

##STR00002##

[0047] where, n is saturated hydrocarbon with 2 to 8 carbon atoms; R.sub.1 is saturated or unsaturated hydrocarbon with 18 to 28 carbon atoms; R.sub.2 and R.sub.3 are independently methyl, ethyl or hydrogen, and R.sub.2 and R.sub.3 can be the same or different; and X.sup.− is any one of Cl.sup.−, Br.sup.−, F.sup.−, CO.sub.3.sup.2−, SO.sub.4.sup.2−, HCOO.sup.− and CH.sub.3COO.sup.−.

[0048] A method for preparing the VES for a self-diverting acid under high temperature is also provided. The method includes the following steps:

[0049] S1: A fatty acid and an organic amine are added to a reactor, and the mixture is heated to 160° C. to 170° C. and then reacts for 11 h to 13 h; the reaction is stopped, and the reaction solution is poured into a cold acetone solution after the reaction solution is cooled to 25° C. to 35° C.; the resulting solution is stirred and filtrated; and the obtained solid is washed 2 to 3 times with acetone, and lyophilized to obtain a white solid intermediate. During the reaction, circulating water cooling is continuously conducted to have the organic amine refluxed. The organic amine and the fatty acid are used at a molar ratio of (1.1-1.5):1.

[0050] The fatty acid is a combination of at least one or more of saturated or unsaturated alkyl fatty acids that have 18 to 28 carbon atoms. The organic amine includes a combination of one or more of N,N-dimethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-dimethyl-1,4-butanediamine, N,N-diethylethylenediamine, N,N-diethyl-1,3-propanediamine, ethylenediamine, propanediamine, butanediamine, pentanediamine, hexamethylenediamine, heptanediamine and octanediamine.

[0051] S2: The obtained intermediate is dissolved in THF, and the resulting solution is added dropwise to a solution of a metal hydride in THF at 0° C. to 5° C.; the resulting solution is heated to 65° C. to 85° C. and then reacts for 24 h to 36 h; deionized water, a NaOH solution with a mass concentration of 10% to 20% and deionized water are added in sequence to the reaction solution after the reaction is completed; the resulting solution is filtrated, and the filtrate is dried and filtrated once again; and the solvent is removed from the filtrate obtained in the second filtration to obtain a fatty amine. The intermediate and the metal hydride are used at a molar ratio of 1:(2.0-2.5). The deionized water is added the first time to quench the metal hydride, then the NaOH solution is added to remove metal ions, and then the deionized water is added the second time to ensure that the metal hydride is completely quenched. The metal hydride includes a combination of one or more of LiAlH.sub.4, LiBH.sub.4 and NaBH.sub.4.

[0052] S3: The fatty amine is mixed with an acid solution having a mass concentration of 10% to 20%, and the resulting solution is thoroughly stirred to protonate the tertiary fatty amine, namely, to form an ultra-long-chain VES. The fatty amine has a molar ratio of 1:2 with hydrogen ions (H.sup.+) in the acid solution. The acid solution includes a combination of one or more of a HCl solution, a HBr solution, a HF solution, a H.sub.2SO.sub.4 solution, a H.sub.2CO.sub.3 solution, a HCOOH solution and a CH.sub.3COOH solution.

[0053] In the preparation of the VES, the performance of the ultra-long-chain VES thickener can be adjusted by changing the types of the fatty acid, the organic amine and the acid solution.

[0054] Use of the VES for a self-diverting acid under high temperature as a thickener is provided.

[0055] The VES is mixed with an acid solution having a mass concentration of 10% to 20%, where the acid solution having a mass concentration of 10% to 20% includes a combination of one or more of a HCl solution, a HBr solution, a HF solution, a H.sub.2SO.sub.4 solution, a H.sub.2CO.sub.3 solution, a HCOOH solution and a CH.sub.3COOH solution, and the ultra-long-chain VES thickener has a mass concentration of 1% to 3% in the obtained viscous acid solution.

[0056] When the VES is used as a thickener in a self-diverting acid, an excellent viscosity-increasing effect can be achieved at a mass concentration of 1% for the VES, which results in a low economic cost and is in favor of the large-scale use.

[0057] The VES, as a thickener, has both excellent acid solution-thickening performance and prominent temperature-resistance. When the temperature is up to 150° C., a self-diverting acid based on the surfactant has a viscosity that is relatively stable and greater than 80 mPa.Math.s, which can meet the requirements for use in a harsh environment with strong acids, high temperature and the like.

[0058] The strong acid-resistance and high temperature-resistance properties are analyzed for the VES as a thickener below in conjunction with typical examples:

EXAMPLE 1

[0059] (1) 16.92 g (0.05 mol) of cis-13-docosenoic acid (commonly known as “erucic acid”) and 7.66 g (0.075 mol) of N,N-dimethylpropanediamine (n=2, R.sub.2 and R.sub.3 were methyl groups) were weighed and added to a three-necked flask, and the mixture was gradually heated to 160° C. and reacted for 11 h; then the reaction was stopped, and the reaction solution was transferred to an acetone solution after the reaction solution was cooled to room temperature; and the resulting solution was stirred, filtered, and lyophilized to obtain a white solid powder, namely, N-(cis-docosa-9-alkenyl-amidopropyl)-N,N-dimethyl tertiary amine, with structural characterization shown as .sup.1H NMR spectrum (FIG. 1). The chemical shift of each proton peak for the compound had been found in the spectrum, and the integral area ratio of proton resonance peaks was in excellent agreement with the theoretical value, indicating that the compound had been successfully synthesized.

[0060] (2) The obtained N-(cis-docosa-9-alkenyl-amidopropyl)-N,N-dimethyl tertiary amine was added to a 500 mL round-bottom flask, and 100 mL of THF was added to dissolve the solid; and after the solid was completely dissolved, the resulting solution was cooled to 0° C., and a solution of LiAlH.sub.4 in THF was added dropwise; then the mixture was heated to 85° C. and reacted for 24 h; after the reaction was completed, deionized water, a 10% NaOH solution, and deionized water were added in sequence to the obtained reaction solution to quench the reaction; the resulting solution was filtered, and the filtrate was dried over anhydrous MgSO.sub.4 and filtered once again; and the final filtrate was subjected to rotary evaporation to remove the solvent to obtain N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine, with structural characterization shown as .sup.1H NMR spectrum (FIG. 2), where the N-(cis-docosa-9-alkenyl-amidopropyl)-N,N-dimethyl tertiary amine and the metal hydride were used at a molar ratio of 1:2.5. The chemical shift of each proton peak for the compound had been found in the spectrum, and the integral area ratio of proton resonance peaks was in excellent agreement with the theoretical value, indicating that the compound had been successfully synthesized.

[0061] (3) Temperature-resistance and shear-resistance test: N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine was mixed with a 10% H.sub.2SO.sub.4 solution and a 20% HCl solution separately, where, N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine had a molar ratio of 1:2 with H.sup.+ in the 10% H.sub.2SO.sub.4 or 20% HCl solution. The resulting mixtures were thoroughly stirred at 50° C. for 24 h to obtain N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine sulfate and N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrochloride (where, N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrochloride had structural characterization shown as the .sup.1H NMR spectrum of FIG. 3 and the mass spectrum of FIG. 4), respectively. Then, the N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine sulfate and N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrothloride were respectively mixed with a 15% H.sub.2SO.sub.4 solution and a 10% HCl solution to obtain a self-diverting acid of N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine sulfate and a self-diverting acid of N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrochloride, where the N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine sulfate and N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrothioride had a concentration of 3% and 1% in the respective acid solutions. The viscosity of the acid system was tested at different temperatures by Haake rheometer and the supporting PZ39 rotor/drum system thereof. The relationship of the viscosity of the obtained self-diverting acid system with temperature and time was tested at a shear rate of 170 s.sup.−1. The results are shown in FIG. 5 and FIG. 6. It can be seen that, when the temperature is stabilized at 150° C., the viscosity of the acid solution is relatively stable and greater than 80 mPa.Math.s, indicating that the ultra-long-chain VES obtained in this example has excellent temperature-resistance and shear-resistance as a thickener. After the test was completed, the acid solution was recovered. The resulting acid solution, which had the same appearance (colorless and transparent) as the acid solution before test, was lyophilized for mass spectrometry (FIG. 7). There is m/z=409.47 (M+H.sup.+) in the spectrum, which has a theoretical value of 409.45, demonstrating that the ultra-long-chain surfactant prepared in this example has a stable chemical structure and does not decompose and deteriorate in an environment with high temperature and strong acids.

[0062] (4) Acid-rock reaction kinetics test: N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine was mixed with a 20% HCl solution, and the mixture was thoroughly stirred at 50° C. for 24 h to obtain a self-diverting acid of N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride. A Xinjiang outcrop with a cross-sectional area of 4.9 cm.sup.2 was adopted, and the acid-rock reaction kinetics test was conducted by a rotating disk reactor, with a temperature of 150° C., a pressure of 7.5 MPa and a rotational speed of 500 r/min. It can be seen from the results that the self-diverting acid has a reaction rate constant of K=7.4×10.sup.−6 (mol.Math.L).sup.−m.Math.mol/(cm.sup.2.Math.s), which is lower than that (K=3.5×10.sup.−5 (mol.Math.L).sup.−mmmol/(cm.sup.2.Math.s) of the control group (20% HCl) (FIG. 8), indicating that the self-diverting acid solution with ultra-long-chain VES as a thickener in this example has excellent rate-reducing performance, and can effectively extend the acidification time. The outcrop samples were observed after the test. Compared with the Outcrop corroded by 20% HCl, the outcrop corroded by the self-diverting acid solution with ultra-long-chain VES as a thickener in this example has uniform and smooth appearance, without obvious pitting corrosion, indicating that the self-diverting acid solution of this example has the ability to achieve uniform acidification. The details are shown in FIG. 9, where A shows the outcrop before the test, and B shows the outcrop reacted with a 20% HCl solution of N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine hydrochloride, and C shows the outcrop reacted with 20% HCl.

[0063] (5) Diverting ability test: In order to determine the variation tendency of the viscosity of the diverting acid in the reservoir, the concentrations of HCl and CaCl.sub.2 were calculated at different time points during the acid-rock reaction. A series of mixed solutions of HCl and CaCl.sub.2 were prepared, N-(cis-docosa-9-alkenyl-aminopropyl)-N,N-dimethyl tertiary amine was mixed with the above mixed solution of HCl and CaCl.sub.2, and the resulting mixture was thoroughly stirred at 50° C. for 24 h. The diverting ability was tested by Anton Paar rheometer and the supporting PR170/XL rotor/drum system thereof. With a temperature of 150° C., a shear rate of 170 s.sup.−1 and a pressure of 1 MPa, the viscosity of the self-diverting acid was determined at different time points. It can be seen from the results that the self-diverting acid based on N-(cis-docosa-9-alkenyl)-N,N-dimethyl tertiary amine hydrochloride has a viscosity which increases first and then decreases with the decreasing HCl concentration and the increasing Ca.sup.2+ concentration (FIG. 10), indicating that the self-diverting acid solution with ultra-long-chain VES as a thickener in this example has excellent diverting performance and thus can achieve the uniform acidification in a target reservoir.

[0064] It can be seen from Example 1 that the surfactant, as a thickener, has a stable chemical structure, and does not decompose even in a harsh environment with high temperature, strong acids or the like, which meets the requirements for use in a harsh environment with strong acids, high temperature or the like. The surfactant, as a thickener, can significantly slow the reaction of the acid solution with the formation rock to achieve the purpose of extending the acidification distance, increasing the acidification time, and uniform acidification.

EXAMPLE 2

[0065] (1) 14.22 g (0.05 mol) of octadecanoic acid (commonly known as “stearic acid”) and 5.61 g (0.055 mol) of N,N-dimethylpropanediamine (n=2, R.sub.2 and R.sub.3 were methyl groups) were weighed and added to a three-necked flask, and the mixture was gradually heated to 170° C. and reacted for 13 h; then the reaction was stopped, and the reaction solution was transferred to an acetone solution after the reaction solution was cooled to room temperature; and the resulting solution was stirred, filtered, and lyophilized to obtain a white solid powder, namely, N-(octadecylamidopropyl)-N,N-dimethyl tertiary amine.

[0066] (2) The obtained N-(octadecylamidopropyl)-N,N-dimethyl tertiary amine was added to a 500 mL round-bottom flask, and 100 mL of THF was added to dissolve the solid. After the solid was completely dissolved, the resulting solution was cooled to 5° C. and a solution of LiAlH.sub.4 in THF was added dropwise. The mixture was then heated to 65° C. and reacted for 36 h. After the reaction was completed, deionized water, a 10% NaOH solution and deionized water were added in sequence to the obtained reaction solution to quench the reaction. The resulting solution was filtered and the filtrate was dried over anhydrous MgSO.sub.4 and filtered once again. The final filtrate was subjected to rotary evaporation to remove the solvent to obtain N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine, with structural characterization shown as .sup.1H NMR spectrum (FIG. 11), where the N-(octadecylamidopropyl)-N,N-dimethyl tertiary amine and the metal hydride were used at a molar ratio of 1:2. The chemical shift of each proton peak for the compound had been found in the spectrum, and the integral area ratio of proton resonance peaks was in excellent agreement with the theoretical value, indicating that the compound had been successfully synthesized.

[0067] (3) The N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine was mixed with a 10% HCl solution; and the mixture was thoroughly stirred at 50° C. for 24 h to obtain N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine hydrochloride, where the N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine had a molar ratio of 1:2 with H.sup.+ in the 10% HCl solution. Then, the N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine hydrochloride was mixed with a 10% HCl solution to obtain a self-diverting acid of N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine hydrochloride, where the N-(octadecylaminopropyl)-N,N-dimethyl tertiary amine hydrochloride had a concentration of 3% in the acid solution. The viscosity of the acid system was tested at different temperatures by Anton Paar rheometer and the supporting PR170/XL rotor/drum system thereof. The relationship of the viscosity of the obtained self-diverting acid system with temperature and time was tested at a shear rate of 170 s.sup.−. The results are shown in FIG. 12. It can be seen that, when the temperature is stabilized at 150° C., the viscosity of the acid solution is relatively stable and greater than 20 mPa.Math.s, indicating that the ultra-long-chain VES obtained in this example has excellent temperature-resistance as a thickener.

EXAMPLE 3

[0068] (1) 21.23 g (0.05 mol) of octacosanoic acid (commonly known as “montanic acid”) and 9.76 g (0.075 mol) of N,N-diethylpropanediamine (n=2, R.sub.2 and R.sub.3 were ethyl groups) were weighed and added to a three-necked flask. The mixture was gradually heated to 160° C. and reacted for 11 h. The reaction was stopped and the reaction solution was transferred to an acetone solution after the reaction solution was cooled to room temperature. The resulting solution was stirred, filtered, and lyophilized to obtain a white solid powder, namely, N-(octacosylamidopropyl)-N,N-diethyl tertiary amine.

[0069] (2) The obtained N-(octacosylamidopropyl)-N,N-diethyl tertiary amine was added to a 500 mL round-bottom flask and 100 mL of THF was added to dissolve the solid. After the solid was completely dissolved, the resulting solution was cooled to 0° C. and a solution of NaBH.sub.4 in THF was added dropwise. The mixture was then heated to 80° C. and reacted for 36 h, After the reaction was completed, deionized water, a 15% NaOH solution, and deionized water were added in sequence to the obtained reaction solution to quench the reaction. The resulting solution was filtered and the filtrate was dried over anhydrous MgSO.sub.4 and filtered once again. The final filtrate was subjected to rotary evaporation to remove the solvent to obtain N-(octacosylaminopropyl)-N,N-diethyl tertiary amine, where the N-(octacosylamidopropyl)-N,N-diethyl tertiary amine and the NaBH.sub.4 were used at a molar ratio of 1:2.

[0070] (3) The N-(octacosylaminopropyl)-N,N-diethyl tertiary amine was mixed with a 15% H.sub.2SO.sub.4 solution and a 10% HCl solution separately, where the N-(octacosylaminopropyl)-N,N-diethyl tertiary amine had a molar ratio of 1:2 with H.sup.+ in the 15% H.sub.2SO.sub.4 or 10% HCl solution. The resulting mixtures were thoroughly stirred at 50° C. for 24 h to obtain N-(octacosylaminopropyl)-N,N-diethyl tertiary amine sulfate and N-(octacosylaminopropyl)-N,N-diethyl tertiary amine hydrochloride, respectively. Then the N-(octacosylaminopropyl)-N,N-diethyl tertiary amine sulfate and N-(octacosylaminopropyl)-N,N-diethyl tertiary amine hydrochloride were respectively mixed with a 15% H.sub.2SO.sub.4 solution and a 10% HCl solution to obtain a self-diverting acid based on N-(octacosylaminopropyl)-N,N-diethyl tertiary amine sulfate and a self-diverting acid based on (octacosylaminopropyl)-N,N-diethyl tertiary amine hydrochloride, respectively.

EXAMPLE 4

[0071] (1) 18.33 g (0.05 mol) of cis-15-tetracosenoic acid (commonly known as “nervonic acid”) and 7.21 g (0.055 mol) of octanediamine (n=8, R.sub.2 and R.sub.3 were hydrogens) were weighed and added to a three-necked flask, and the mixture was gradually heated to 165° C. and reacted for 12 h; then the reaction was stopped, and the reaction solution was transferred to an acetone solution after the reaction solution was cooled to room temperature; and the resulting solution was stirred, filtered, and lyophilized to obtain a white solid powder, namely, N-(cis-tetracosa-15-alkenyl-amidooctyl)amine.

[0072] (2) The obtained N-(cis-tetracosa-15-alkenyl-amidooctyl)amine was added to a 500 mL round-bottom flask, and 100 mL of THF was added to dissolve the solid; and after the solid was completely dissolved, the resulting solution was cooled to 0° C. and a solution of LiBH.sub.4 in THF was added dropwise. The mixture was then heated to 80° C. and reacted for 36 h. After the reaction was completed, deionized water, a 15% NaOH solution and deionized water were added in sequence to the obtained reaction solution to quench the reaction. The resulting solution was then filtered and the filtrate was dried over anhydrous MgSO.sub.4 and filtered once again. The final filtrate was subjected to rotary evaporation to remove the solvent to obtain N-(cis-tetracosa-15-alkenyl-aminooctyl)amine, where the N-(cis-tetracosa-15-alkenyl-amidooctyl)amine and the LiBH.sub.4 were used at a molar ratio of 1:2.

[0073] (3) The N-(cis-tetracosa-15-alkenyl-aminooctyl)amine was mixed with a 10% CH.sub.3COOH solution, where the N-(cis-tetracosa-15-alkenyl-aminooctyl)amine had a molar ratio of 1:2 with H.sup.+ in the 10% CH.sub.3COOH solution. The resulting mixture was thoroughly stirred at 50° C. for 24 h to obtain N-(cis-tetracosa-15-alkenyl-aminooctyl)amine acetate. Then, the N-(cis-tetracosa-15-alkenyl-aminooctyl)amine acetate was mixed with a 10% CH.sub.3COOH solution to obtain a self-diverting acid based on N-(cis-tetracosa-15-alkenyl-aminooctyl)amine acetate.

[0074] The above descriptions are merely preferred implementations of the present invention, and should not be construed as excluding other examples. It should be understood that the present invention is not limited to the form disclosed herein, and can be used in various other combinations, modifications and environments. Modifications can be made within the scope of the concept described herein through the above teachings or techniques or knowledges in related fields. Modifications and changes made by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope of the appended claims of the present invention.