Tri-cationic viscoelastic surfactant, preparation method and application thereof and clean fracturing fluid

Abstract

A three-poly cationic viscoelastic and a clean fracturing fluid containing the three-poly cationic viscoelastic surfactant are provided. N, N-dimethyl-1,3-propanediamine and epichlorohydrin are used to prepare an intermediate A, and then the intermediate A and a fatty acid amidopropyl dimethylamine is used to prepare the three-poly cationic viscoelastic surfactant. The preparation process is simple. The clean fracturing fluid including the three-poly cationic viscoelastic surfactant has excellent temperature and shear resistance, strong suspended sand performance, simple on-site preparation, automatic gel breaking, small damage to formation, low cost and simple preparation process. The clean fracturing fluid including the surfactant also has strong temperature resistance, and the viscosity of the product can be maintained at 42 mPa.Math.s after 80 minutes at 180 C. and 170 s.sup.1, which is higher than the viscosity requirement (>25 mPa.Math.s) of the clean fracturing fluid in on-site construction.

Claims

1. A tri-cationic viscoelastic surfactant, comprising a following structure: ##STR00007## wherein R is a saturated hydrocarbon chain with 17 to 21 carbon atoms or an unsaturated hydrocarbon chain with 17 to 21 carbon atoms.

2. The tri-cationic viscoelastic surfactant according to claim 1, wherein the R is a hydrophobic carbon chain of erucic acid, oleic acid or stearic acid.

3. A preparation method of the tri-cationic viscoelastic surfactant according to claim 1, comprising: (1) dissolving N, N-dimethyl-1,3-propanediamine in an organic solvent, adding epichlorohydrin and concentrated hydrochloric acid, performing a reflux reaction for 5-7 hours at 55-65 C., and then performing a distillation under reduced pressure and performing an extraction to obtain an intermediate A; wherein a molar ratio of the N, N-dimethyl-1,3-propanediamine to the epichlorohydrin to the concentrated hydrochloric acid is 1:(3-6):(1-1.5); (2) dissolving the intermediate A in the organic solvent, adding fatty acid amidopropyl dimethylamine, stirring and performing the reflux reaction for 11-13 h at 80-90 C. and 250-300 r/min, and then performing the distillation under reduced pressure to obtain the tri-cationic viscoelastic surfactant; a molar ratio of intermediate A to the fatty acid amidopropyl dimethylamine is 1:(3-3.1).

4. The preparation method of the tri-cationic viscoelastic surfactant according claim 3, comprising: (1) dissolving N, N-dimethyl-1,3-propanediamine in ethanol, adding epichlorohydrin and concentrated hydrochloric acid, performing the reflux reaction at 60 C. for 6 hours, and then performing the distillation under reduced pressure and performing the extraction to obtain the intermediate A; wherein the molar ratio of the N, N-dimethyl-1,3-propanediamine to the epichlorohydrin to the concentrated hydrochloric acid is 1:3.3:1; (2) dissolving the intermediate A in ethanol, adding the fatty acid amidopropyl dimethylamine, stirring and performing the reflux reaction for 12 h at 85 C. and 250-300 r/min, and then performing the distillation under reduced pressure to obtain the tri-cationic viscoelastic surfactant; the molar ratio of intermediate A to the fatty acid amidopropyl dimethylamine is 1:3.

5. The preparation method of the tri-cationic viscoelastic surfactant according to claim 3, wherein the fatty acid amidopropyl dimethylamine is a combination of one or more of erucamide propyl dimethylamine, oleic amide propyl dimethylamine and stearic amidopropyl dimethylamine.

6. The preparation method of the tri-cationic viscoelastic surfactant according to claim 3, wherein the organic solvent is ethanol or isopropanol.

7. A preparation method of a clean fracturing fluid, comprising the step of using the tri-cationic viscoelastic surfactant according to claim 1 in preparing the clean fracturing fluid and adding the tri-cationic viscoelastic surfactant into water to obtain the clean fracturing fluid.

8. A clean fracturing fluid, comprising: a counter-ion salt and the tri-cationic viscoelastic surfactant of claim 1.

9. The clean fracturing fluid according to claim 8, wherein the clean fracturing fluid comprises 1-3 wt % of the tri-cationic viscoelastic surfactant, 1-1.4 wt % of the counter-ion salt and a rest of the clean fracturing fluid is water.

10. The clean fracturing fluid according to claim 8, wherein the counter-ion salt is one or more combinations of sodium salicylate, potassium chloride, carboxy benzene sulfonate, sodium benzoate and potassium hydrogen benzoate.

11. The preparation method of the clean fracturing fluid according to claim 7, wherein the R is a hydrophobic carbon chain of erucic acid, oleic acid or stearic acid.

12. The preparation method of the clean fracturing fluid according to claim 7, wherein the tri-cationic viscoelastic surfactant is obtained by a process comprising the following steps: (1) dissolving N, N-dimethyl-1,3-propanediamine in an organic solvent, adding epichlorohydrin and concentrated hydrochloric acid, performing a reflux reaction for 5-7 hours at 55-65 C., and then performing a distillation under reduced pressure and performing an extraction to obtain an intermediate A; wherein a molar ratio of the N, N-dimethyl-1,3-propanediamine to the epichlorohydrin to the concentrated hydrochloric acid is 1:(3-6):(1-1.5); (2) dissolving the intermediate A in the organic solvent, adding fatty acid amidopropyl dimethylamine, stirring and performing the reflux reaction for 11-13 h at 80-90 C. and 250-300 r/min, and then performing the distillation under reduced pressure to obtain the tri-cationic viscoelastic surfactant; a molar ratio of intermediate A to the fatty acid amidopropyl dimethylamine is 1:(3-3.1).

13. The preparation method of the clean fracturing fluid according to claim 12, wherein the tri-cationic viscoelastic surfactant is obtained by a process comprising the following steps: (1) dissolving N, N-dimethyl-1,3-propanediamine in ethanol, adding epichlorohydrin and concentrated hydrochloric acid, performing the reflux reaction at 60 C. for 6 hours, and then performing the distillation under reduced pressure and performing the extraction to obtain the intermediate A; the molar ratio of the N, N-dimethyl-1,3-propanediamine to the epichlorohydrin to the concentrated hydrochloric acid is 1:3.3:1; (2) dissolving the intermediate A in ethanol, adding the fatty acid amidopropyl dimethylamine, stirring and performing the reflux reaction for 12 h at 85 C. and 250-300 r/min, and then performing the distillation under reduced pressure to obtain the tri-cationic viscoelastic surfactant; the molar ratio of intermediate A to the fatty acid amidopropyl dimethylamine is 1:3.

14. The preparation method of the clean fracturing fluid according to claim 12, wherein the fatty acid amidopropyl dimethylamine is a combination of one or more of erucamide propyl dimethylamine, oleic amide propyl dimethylamine and stearic amidopropyl dimethylamine.

15. The preparation method of the clean fracturing fluid according to claim 12, wherein the organic solvent is ethanol or isopropanol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a rheological curve of the clean fracturing fluid prepared by 3% tri-cationic viscoelastic surfactant and 1.2% sodium salicylate of Embodiment 1;

(2) FIG. 2 shows a rheological curve of the clean fracturing fluid prepared by 1% tri-cationic viscoelastic surfactant and 1% sodium salicylate of Embodiment 1;

(3) FIG. 3 shows a rheological curve of the clean fracturing fluid prepared by 3% tri-cationic viscoelastic surfactant and 1.4% KCl of Embodiment 2;

(4) FIG. 4 shows a rheological curve of the clean fracturing fluid prepared by 1% tri-cationic viscoelastic surfactant and 1.2% KCl of Embodiment 2;

(5) FIG. 5 shows a rheological curve of the clean fracturing fluid prepared by 3% tri-cationic viscoelastic surfactant and 1.2% sodium salicylate of Embodiment 3;

(6) FIG. 6 shows a rheological curve of the clean fracturing fluid prepared by 1% tri-cationic viscoelastic surfactant and 1% sodium salicylate of Embodiment 3;

(7) FIG. 7 is a nuclear magnetic resonance spectra diagram of the erucic acid type tri-cationic viscoelastic surfactant of the present invention.

DETAILED DESCRIPTION

(8) The principles and characteristics of the present invention are described below with reference to the accompanying drawings. The embodiments are merely used to explain the present invention, and are not intended to limit the scope of the present invention. The preparation methods in the embodiments which do not indicate the specific conditions are usually in accordance with the conventional conditions, or the manufacturer recommended conditions. Reagents or instruments that do not indicate the manufacturer are conventional products that can be purchased in the market.

Embodiment 1

(9) The preparation method of the tri-cationic viscoelastic surfactant in this embodiment is as follows.

(10) Adding 60 mmol of N,N-dimethyl-1,3-propanediamine into a round bottom flask, using ethanol as solvent, adding 200 mmol of epichlorohydrin and 60 mmol of concentrated hydrochloric acid, refluxing at 60 C. for 6 hours, performing the distillation under reduced pressure after the reaction, and performing the extraction to obtain intermediate A. Dissolving the obtained intermediate A in ethanol, adding 180 mmol erucamide propyl dimethylamine, refluxing for 12 hours at 85 C. and 250 r/min, and distilling under reduced pressure after the reaction to remove the solvent ethanol, thus obtaining a yellowish viscous liquid, i.e., the tri-cationic viscoelastic surfactant.

(11) The critical micelle concentration of the surfactant in this embodiment is 1.4410.sup.4 mol/L.

(12) The rheological properties of the clean fracturing fluids prepared by 3% tri-cationic viscoelastic surfactant and 1.2% sodium salicylate at 180 C. and 170 s.sup.1, and 1% tri-cationic viscoelastic surfactant and 1% sodium salicylate at 140 C. and 170 s.sup.1 are shown in FIG. 1 and FIG. 2, respectively. The static suspended sand experiment shows that there is no obvious settlement after 2 hours, and the viscosity of the breaking fluid is 3.1 mPa.Math.s after gel breaking with 300% standard formation water.

Embodiment 2

(13) The preparation method of the tri-cationic viscoelastic surfactant in this embodiment is as follows.

(14) Adding 60 mmol of N,N-dimethyl-1,3-propanediamine into a round bottom flask, using ethanol as solvent, adding 200 mmol of epichlorohydrin and 60 mmol of concentrated hydrochloric acid, refluxing at 60 C. for 6 hours, performing the distillation under reduced pressure after the reaction, and performing the extraction to obtain intermediate A. Dissolving the obtained intermediate A in ethanol, adding 180 mmol oleic amide propyl dimethylamine, refluxing for 12 hours at 85 C. and 270 r/min, and distilling under reduced pressure after the reaction to remove the solvent ethanol, thus obtaining a yellowish viscous liquid, i.e., the tri-cationic viscoelastic surfactant.

(15) The critical micelle concentration of the surfactant in this embodiment is 1.5610.sup.4 mol/L.

(16) The rheological properties of the clean fracturing fluids prepared by 3% tri-cationic viscoelastic surfactant and 1.4% KCl at 160 C. and 170 s.sup.1, and 1% tri-cationic viscoelastic surfactant and 1.2% KCl at 140 C. and 170 s.sup.1 are shown in FIG. 3 and FIG. 4, respectively. The static suspended sand experiment shows that there is no obvious settlement after 2 hours, and the viscosity of the breaking fluid is 2.8 mPa.Math.s after gel breaking with 300% standard formation water.

Embodiment 3

(17) The preparation method of the tri-cationic viscoelastic surfactant in this embodiment s as follows.

(18) Adding 60 mmol of N,N-dimethyl-1,3-propanediamine into a round bottom flask, using ethanol as solvent, adding 200 mmol of epichlorohydrin and 60 mmol of concentrated hydrochloric acid, refluxing at 60 C. for 6 hours, performing the distillation under reduced pressure after the reaction, and performing the extraction to obtain intermediate A. Dissolving the obtained intermediate A in ethanol, adding 180 mmol stearic acid amide propyl dimethyl amine, refluxing for 12 hours at 85 C. and 280 r/min, and distilling under reduced pressure after the reaction to remove the solvent ethanol, thus obtaining a yellowish viscous liquid, i.e., the tri-cationic viscoelastic surfactant.

(19) The critical micelle concentration of the surfactant in this embodiment is 1.8410.sup.4 mol/L.

(20) The rheological properties of the clean fracturing fluids prepared by 3% tri-cationic viscoelastic surfactant and 1.2% sodium salicylate at 160 C. and 170 s.sup.1, and 1% tri-cationic viscoelastic surfactant and 1% sodium salicylate at 130 C. and 170 s.sup.1 are shown in FIG. 5 and FIG. 6, respectively. The static suspended sand experiment shows that there is no obvious settlement after 2 hours, and the viscosity of the breaking fluid is 2.1 mPa.Math.s after gel breaking with 300% standard formation water.

Embodiment 4

(21) The preparation method of the tri-cationic viscoelastic surfactant in this embodiment is as follows.

(22) Adding 60 mmol of N,N-dimethyl-1,3-propanediamine into a round bottom flask, using ethanol as solvent, adding 180 mmol of epichlorohydrin and 72 mmol of concentrated hydrochloric acid, refluxing at 55 C. for 7 hours, performing the distillation under reduced pressure after the reaction, and performing the extraction to obtain intermediate A. Dissolving the obtained intermediate A in ethanol, adding 186 mmol stearic acid amide propyl dimethyl amine, refluxing for 13 hours at 80 C. and 300 r/min, and distilling under reduced pressure after the reaction to remove the solvent ethanol, thus obtaining a yellowish viscous liquid, i.e., the tri-cationic viscoelastic surfactant.

Embodiment 5

(23) The preparation method of the tri-cationic viscoelastic surfactant in this embodiment is as follows.

(24) Adding 60 mmol of N,N-dimethyl-1,3-propanediamine into a round bottom flask, using ethanol as solvent, adding 360 mmol of epichlorohydrin and 90 mmol of concentrated hydrochloric acid, refluxing at 65 C. for 5 hours, performing the distillation under reduced pressure after the reaction, and performing the extraction to obtain intermediate A. Dissolving the obtained intermediate A in ethanol, adding 183 mmol stearic acid amide propyl dimethyl amine, refluxing for 11 hours at 90 C. and 260 r/min, and distilling under reduced pressure after the reaction to remove the solvent ethanol, thus obtaining a yellowish viscous liquid, i.e., the tri-cationic viscoelastic surfactant.

(25) It should be noted that the fatty acid amidopropyl dimethylamine used in the embodiment of the present invention may be any two combinations of erucamide propyl dimethylamine, oleic amide propyl dimethylamine and stearic amide propyl dimethylamine, or the combination of erucamide propyl dimethylamine, oleic amide propyl dimethylamine and stearic amide propyl dimethylamine, in addition to the single components mentioned above. The counter-ion salt used in the embodiment of the present invention may also be any two, three, four or five combinations of sodium salicylate, potassium chloride, carboxy benzene sulfonate, sodium benzoate and potassium hydrogen benzoate.

(26) FIGS. 1-6 show rheological curves of the clean fracturing fluids prepared by the tri-cationic viscoelastic surfactants in the above-mentioned Embodiments 1-3. From the figures, it can be seen that the comparison of FIGS. 1, 3 and 5, and the comparison of FIGS. 2, 4 and 6 both illustrate a problem that when the dosages of the thickening agent are the same and the counter-ion is in the best dosage, the temperature resistance of erucic acid is the best. The temperature resistance of erucic acid with the same dosage in FIGS. 1, 3 and 5 can reach 180 C., and the viscosity of stearic acid is the lowest under the same conditions. Similarly, erucic acid and oleic acid can withstand temperature up to 140 C. at the same dosage in FIGS. 2, 4 and 6, but the viscosity of oleic acid is relatively low. Generally speaking, the clean fracturing fluid of the present invention has high temperature resistance, and the viscosity of the product can be maintained at 42 mPa.Math.s after 80 minutes at 130 C. and 170 s.sup.1, which is higher than the viscosity requirement (>25 mPa.Math.s) of the clean fracturing fluid for on-site operation.

(27) FIG. 7 is a nuclear magnetic resonance spectra diagram of erucic acid type tri-cationic viscoelastic surfactant according to an embodiment of the present invention, which determines the molecular structure of the tri-cationic viscoelastic surfactant.

(28) In summary, the tri-cationic viscoelastic surfactant and the clean fracturing fluid including the surfactant have excellent temperature and shear resistance, good prop-carrying capacity, easy preparation, automatic gel breaking, low damage to formation and low cost. The clean fracturing fluid including the surfactant also has high temperature resistance, and the viscosity of the product can be maintained at 42 mPa.Math.s after 80 minutes at 130 C. and 170 s.sup.1, which is higher than the viscosity requirement (>2.5 mPa.Math.s) of the clean fracturing fluid in on-site construction.

(29) The above-mentioned embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalents and improvements without departing from the spirit and principle of the present invention shall fall within the scope of the present invention.