Method of fracturing with delayed crosslinking of gelling agents

1. A method of fracturing a subterranean formation penetrated by a well comprising:

A. pumping into the well at a pressure sufficient to create a fracture an aqueous well treatment fluid comprising (a) a water-soluble gellant; and (b) a non-aqueous slurry, wherein the non-aqueous slurry comprises (i) a non-aqueous liquid immiscible in water; (ii) an oil-wetting surface active material; and (iii) a crosslinking agent; and

B. delaying crosslinking of the crosslinking agent and the gellant by absorbing at least a portion of the oil-wetting surface active material onto a surface of the crosslinking agent.

2. The method of claim 1 , wherein the water-soluble gellant in the aqueous well treatment fluid is from about 6 to about 15 pounds per 1,000 gallons of water in the aqueous well treatment fluid.

3. The method of claim 1 , wherein the viscosity of the aqueous well treatment fluid is less than 20 cP at 40 sec −1 .

4. The method of claim 1 , wherein the non-aqueous liquid is oil.

5. The method of claim 4 , wherein the oil is a non-polar oil having from C 3 -C 20 hydrocarbons.

6. The method of claim 4 , wherein the non-aqueous slurry further comprises an organophilic clay.

7. The method of claim 6 , wherein:

(a) from about 200 to about 235 pounds per barrel of the slurry is the oil;

(b) from about 0.3 to about 0.75 pounds per barrel of the slurry is the oil-wetting surface active material;

(c) from about 65 to about 135 pounds per barrel of the slurry is the crosslinking agent; and

(d) from about 6 to about 10 pounds per barrel of the slurry is the organophilic clay.

8. The method of claim 1 , wherein the water-soluble gellant is underivatized guar, derivatized guar, locust bean gum, tara gum, fenugreek gum, a cellulosic derivative or a mixture thereof.

9. The method of claim 1 , wherein the crosslinking agent is a borate salt.

10. The method of claim 1 , wherein the oil-wetting surface active material is a polyhydric ester.

11. The method of claim 10 , wherein the oil-wetting surface active material is a sorbitan ester.

12. The method of claim 10 , wherein the oil-wetting surface active material is an ethoxylated sorbitan ester.

13. The method of claim 1 , wherein the oil-wetting surface active material is an alkoxylated glyceride.

14. The method of claim 1 , wherein the oil-wetting surface active material is selected from the group consisting of sorbitan esters, ethoxylated sorbitan esters and alkoxylated glycerides.

15. The method of claim 1 , wherein the oil-wetting surface active material is an alkylene oxide adduct of a C 6 -C 30 alcohol or phenol.

16. The method of claim 1 , wherein the delay in the crosslinking is in a range of 90 seconds to 3 minutes.

17. A method of fracturing a subterranean formation penetrated by a well comprising:

A. pumping into the well at a pressure sufficient to create a fracture an aqueous well treatment fluid comprising (a) a water-soluble gellant; and (b) a non-aqueous slurry, wherein the non-aqueous slurry comprises (i) a non-aqueous liquid immiscible in water; (ii) a crosslinking agent; and (iii) an oil-wetting surface active material having affinity to absorb onto a surface of the crosslinking agent;

B. forming an oil-wet crosslinking agent by absorbing the oil-wetting surface active material onto the surface of the crosslinking agent;

C. delaying dissolution of the crosslinking agent in water by the presence of the absorbed oil-wetting surface active material on the surface of the crosslinking agent; and

D. delaying crosslinking between the crosslinking agent and the water-soluble gellant by the delayed dissolution of the crosslinking agent.

18. The method of claim 17 , wherein the non-aqueous slurry further comprises an organophilic clay.

19. The method of claim 17 , wherein the aqueous well treatment fluid pumped into the well has a viscosity less than 20 cP at 40 sec−1 and thermally thins under in-situ conditions in the subterranean formation.

20. The method of claim 17 , wherein the delay in the crosslinking is in a range of 90 seconds to 3 minutes.

21. A method of fracturing a subterranean formation penetrated by a well comprising:

A. pumping into the well at a pressure sufficient to create a fracture an aqueous well treatment fluid comprising (a) a water-soluble gellant; and (b) a non-aqueous slurry, wherein the non-aqueous slurry comprises (i) a non-aqueous liquid immiscible in water; (ii) an organophilic clay; (iii) a borate crosslinking agent; and (iv) an oil-wetting surface active material selected from the group consisting of sorbitan esters, ethoxylated sorbitan esters and alkoxylated glycerides; and

B. delaying crosslinking between the borate crosslinking agent and the water-soluble gellant by absorbing the oil-wetting surface active material onto a surface of the borate crosslinking agent.

22. A method of fracturing a subterranean formation penetrated by a well comprising:

A. pumping into the well at a pressure sufficient to create a fracture an aqueous well treatment fluid comprising (a) a water-soluble gellant; and (b) a non-aqueous slurry, wherein the non-aqueous slurry comprises (i) a non-aqueous liquid immiscible in water; (ii) an oil-wetting surface active material selected from the group consisting of sorbitan esters, ethoxylated sorbitan esters, alkoxylated glycerides and alkylene oxide adducts of a C 6 -C 30 alcohol or phenol; and (iii) a crosslinking agent; and

B. delaying crosslinking of the crosslinking agent and the gellant by absorbing the oil-wetting surface active material onto a surface of the crosslinking agent.

23. The method of claim 22 , wherein the water-soluble gellant is underivatized guar, derivatized guar, locus bean gum, tara gum, fenugreek gum, a cellulosic derivative or a mixture thereof.

24. The method of claim 22 , wherein the water-soluble gellant in the aqueous well treatment fluid is from about 6 to about 15 pounds per 1,000 gallons of water in the aqueous well treatment fluid.

25. The method of claim 22 , wherein the crosslinking agent is a borate salt.