Stable solutions of zirconium hydroxyalkylethylene diamine complex and use in oil field applications

1. A clear, stable, salt-free solution comprising a complex having a 1:1 molar ratio of zirconium and N,N,N′,N′-tetrakis-(2-hydroxypropy1)-ethylene diamine, water and a solvent, wherein 0.5 to 20 moles of water per mole of zirconium is added and the solvent is selected from the group consisting of C 1 -C 6 alcohols.

2. The solution of claim 1 wherein the solvent is n-propanol.

3. A process to prepare a clear, stable, salt-free solution comprising (a) contacting a solution of a tetraalkyl zirconate in a C 1 -C 6 alcohol with one molar equivalent of N,N,N′,N′-tetrakis-(2-hydroxypropy1)-ethylene diamine to produce an initial solid reaction product, which is a slurry of zirconate-diamine; and (b) contacting the initial reaction product with 0.5 to 20 moles of water per mole of zirconium at a temperature in the range of 25° C. to 92° C. to produce a clear solution.

4. The process of claim 3 wherein step (a) is carried out at a temperature between 50° C. and 90° C.

5. The process of claim 3 wherein step (b) is carried out at a temperature in the range of 60° C. to 80° C.

6. The process of claim 4 wherein the amount of water added is between 1 and 5 moles of water per mole of zirconium.

7. A cross-linking composition comprising (a) an aqueous liquid; (b) a pH buffer; (c) a cross-linkable organic polymer; and (d) a solution comprising a complex having a 1:1 molar ratio of zirconium and N,N,N′,N′-tetrakis-(2-hydroxypropy1)-ethylene diamine, water and a solvent wherein 0.5 to 20 moles of water per mole of zirconium is added and the solvent is selected from the group consisting of C 1 -C 6 alcohols.

8. The cross-linking composition of claim 7 wherein the cross-linkable organic polymer is selected from the group consisting of solvatable polysaccharides, polyacrylamides and polymethacrylamides.

9. The cross-linking composition of claim 8 wherein the cross-linkable organic polymer is a solvatable polysaccharide.

10. The cross-linking composition of claim 8 wherein the cross-linkable organic polymer is selected from the group consisting of gums, gum derivatives and cellulose derivatives.

11. The cross-linking composition of claim 8 wherein the cross-linkable organic polymer is hydroxypropylguar, carboxymethylhydroxypropylguar, or carboxymethylcellulose.

12. The cross-linking composition of claim 7 wherein the cross-linkable polymer is mixed with an aqueous liquid.

13. The cross-linking composition of claim 12 wherein the aqueous liquid is an aqueous solution comprising a clay stabilizer.

14. The cross-linking composition of claim 13 wherein the clay stabilizer is hydrochloric acid, tetramethylammonium chloride or potassium chloride.

15. A method for hydraulically fracturing a subterranean formation comprising introducing into a subterranean formation at a flow rate and pressure sufficient to create, reopen and/or extend a fracture in the formation, (a) an aqueous liquid; (b) a pH buffer; (c) a cross-linkable organic polymer; and (d) a solution comprising a complex having a complex having a 1:1 molar ratio of zirconium and N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylene diamine, water and a solvent, wherein 0.5 to 20 moles of water per mole of zirconium is added and the solvent is selected from the group consisting of C1-C6 alcohols.

16. The method of claim 15 wherein the aqueous liquid, pH buffer, cross-linkable organic polymer; and solution of zirconium complex are contacted prior to their introduction into the subterranean formation.

17. The method of claim 15 wherein the subterranean formation is penetrated by a wellbore and contacting of the solution of zirconium complex (d) with the aqueous liquid (a) and the cross-linkable organic polymer (c) occurs in the wellbore.

18. The method of claim 15 further comprising introducing (e) proppant into the subterranean formation.

19. A method for plugging a permeable zone or leak in a subterranean formation comprising introducing into said zone or said leak, (a) an aqueous liquid; (b) a pH buffer; (c) a cross-linkable organic polymer; and (d) a solution comprising a complex having a 1:1 molar ratio of zirconium and N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylene diamine, water and a solvent, wherein 0.5 to 20 moles of water per mole of zirconium is added and the solvent is selected from the group consisting of C1-C6 alcohols.

20. The method of claim 19 wherein the aqueous liquid, pH buffer, cross-linkable organic polymer; and solution of zirconium complex are contacted prior to their introduction into the subterranean formation.

21. The method of claim 19 wherein the subterranean formation is penetrated by a wellbore and contacting of the solution of zirconium complex (d) with the aqueous liquid (a) and the cross-linkable organic polymer (c) occurs in the wellbore.