Water-in-oil hydraulic fracturing fluid and method of using such

1. A hydraulic fracturing fluid for treating subterranean formations comprising a water-in-oil emulsion comprising an aqueous solution, an oil, and a first surfactant, wherein the first surfactant comprises:

a 4-mole or higher ethoxylate of a fatty amine represented by formula I:

wherein R 1 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 12 to 18 carbon atoms; and

wherein a and b are each integers independently ranging from 2 to 15 and

an emulsifying surfactant comprising an imidazoline represented by formula V:

wherein X 4 is one of the following: —NH 2 ,

and R 5 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms.

2. The hydraulic fracturing fluid of claim 1 , wherein the water-in-oil emulsion further comprises at least one secondary surfactant selected from:

(a) a second emulsifying surfactant comprising at least one of:

[[-an imidazoline represented by formula V:

wherein X 4 is one of the following: —OH, —NH 2 ,

and R 5 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms;]]

an amidoamine represented by formula VI:

wherein X 5 is one of the following: —OH, —NH 2 ,

and R 6 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms; and

a hydroxyalkyl carbamate represented by formula VII:

wherein R 7 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms, and each of R 8 and R 9 are one of the following: (i) R 8 ═R 9 ═—H, (ii) R 8 ═—H and R 9 ═—CH 2 OH, (iii) R 8 ═—CH 2 OH and R 9 ═—H, (iv) R 8 ═—H and R 9 ═—CH 3 , (v) R 8 ═—CH 3 and R 9 ═—H, (vi) R 8 ═—H and R 9 ═—C 2 H 5 , or (vii) R 8 ═—C 2 H 5 and R 9 ═—H;

(b) a phosphate ester of ethoxylated alcohol or alkylphenol represented by structure IV:

wherein

wherein k is an integer ranging from 1 to 20[[, or from 1 to 10, or from 1 to 6,]]and R 4 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 4 to 14 carbon atoms, alkylbenzene, or dialkylbenzene; and Y 3 ═—H or —X 3 ; or

(c) a combination thereof.

3. The hydraulic fracturing fluid of claim 2 , wherein the water-in-oil emulsion comprises about 40 to about 90 wt % of the aqueous solution, about 5 to about 55 wt % of the oil, about 0.5 to about 3 wt % of the first surfactant, greater than 0 to about 3 wt % of the emulsifying surfactant, and greater than 0 to about 3 wt % of the phosphate ester of ethoxylated alcohol or alkylphenol, based on the total weight of the water-in-oil emulsion.

4. The hydraulic fracturing fluid of claim 2 , wherein the at least one secondary surfactant comprises the phosphate ester of ethoxylated alcohol or alkylphenol represented by formula IV.

5. The hydraulic fracturing fluid of claim 4 , wherein the water-in-oil emulsion comprises about 70 to about 90 wt % of the aqueous solution, about 0.5 to about 3 wt % of the first surfactant, greater than 0 to about 3 wt % of the emulsifying surfactant, and greater than 0 to about 3 wt % of the phosphate ester of ethoxylated alcohol or alkylphenol, based on the total weight of the water-in-oil emulsion.

6. The hydraulic fracturing fluid of claim 1 , wherein the water-in-oil emulsion further comprises a pH modifier.

7. The hydraulic fracturing fluid of claim 6 , wherein the pH modifier is present in the water-in-oil emulsion in an amount of from greater than 0 to about 2 wt %, based on the total weight of the water-in-oil emulsion.

8. The hydraulic fracturing fluid of claim 6 , wherein the pH modifier is lime.

9. The hydraulic fracturing fluid of claim of claim 1 , wherein the hydraulic fracturing fluid further comprises a proppant.

10. A method for fracturing a subterranean formation, comprising injecting the hydraulic fracturing fluid of claim 9 into a subterranean formation at a pressure sufficient to fracture the formation.

11. A method of fracturing a subterranean formation, the subterranean formation being in fluid communication with the surface of a well, the method comprising:

a) injecting the hydraulic fracturing fluid of claim 9 into said well;

b) pressurizing said hydraulic fracturing fluid so as to cause the subterranean formation to fracture and allow the proppant to enter said fractures; and

c) adding acid to said hydraulic fracturing fluid so as to change the water-in-oil emulsion in the hydraulic fracturing fluid to an oil-in-water emulsion.

12. The method of claim 11 , wherein at least a portion of said hydraulic fracturing fluid containing an oil-in-water emulsion is pumped out of the subterranean formation after step c).

13. The method of claim 12 , wherein a base is added to said hydraulic fracturing fluid that has been pumped out of the subterranean formation so as to change the oil-in-water emulsion in the hydraulic fracturing fluid to a water-in-oil emulsion.

14. The method of claim 13 , wherein the emulsifying surfactant is a hydroxyalkyl carbamate represented by formula VII:

wherein R 7 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms, and each of R 8 and R 9 are one of the following: (i) R 8 ═R 9 ═—H, (ii) R 8 ═—H and R 9 ═—CH 2 OH, (iii) R 8 ═—CH 2 OH and R 9 ═—H, (iv) R 8 ═—H and R 9 ═—CH 3 , (v) R 8 ═—CH 3 and R 9 ═—H, (vi) R 8 ═—H and R 9 ═—C 2 H 5 , or (vii) R 8 ═—C 2 H 5 and R 9 ═—H.

15. The method of claim 14 , wherein no additional surfactant is added with the base.

16. A hydraulic fracturing fluid for treating subterranean formations comprising a water-in-oil emulsion comprising an aqueous solution, an oil, and a first surfactant comprising a 4-mole or higher ethoxylate of a fatty amine represented by formula I:

wherein R 1 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 12 to 18 carbon atoms; and

wherein a and b are each integers independently ranging from 2 to 15,

an emulsifying surfactant comprising an imidazoline represented by formula V:

wherein X 4 is one of the following: —OH, —NH 2 ,

and R 5 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 9 to 17 carbon atoms, and

a secondary surfactant comprising a phosphate ester of ethoxylated alcohol or alkylphenol represented by formula IV:

wherein

wherein k is an integer ranging from 1 to 20, and R 4 is a saturated or unsaturated, branched or straight chain, substituted or unsubstituted hydrocarbyl group having from 4 to 14 carbon atoms, alkylbenzene, or dialkylbenzene; and Y 3 ═—H or —X 3 .

17. The hydraulic fracturing fluid of claim 16 , wherein the water-in-oil emulsion further comprises a pH modifier.

18. The hydraulic fracturing fluid of claim 17 , wherein the pH modifier is present in the water-in-oil emulsion in an amount greater than 0 to about 2 wt %, based on the total weight of the water-in-oil emulsion.

19. The hydraulic fracturing fluid of claim 18 , wherein the pH modifier is lime.

20. The hydraulic fracturing fluid of claim 16 , wherein the hydraulic fracturing fluid further comprises a proppant.