Oil well fracturing fluids
Additives useful in attenuating the crosslinking time of sparingly soluble borate minerals and the use of those additives in oil well fracturing fluids and methods are described.
1. A method for fracturing a formation accessible through a wellbore, the method comprising: providing a fracturing fluid including a viscosifying polysaccharide, 0.4 and 10 kg/m 3 of colemanite as a sole source of borate for crosslinking the viscosifying polysaccharide, and an effective amount of a metal sequestering agent including a chelating agent for chelating with calcium to viscosify the fracturing fluid 30 to 300 seconds after mixing the viscosifying polysaccharide, the colemanite and the metal sequestering agent; introducing the fracturing fluid to the wellbore to contact the formation; and pumping the fracturing fluid to induce and propagate a fracture in the formation.
2. The method for fracturing a formation of claim 1 wherein providing a fracturing fluid is conducted at surface.
3. The method for fracturing a formation of claim 1 wherein the fracturing fluid viscosifies when in the wellbore.
4. The method for fracturing a formation of claim 1 wherein in providing the fracturing fluid, the viscosifying polysaccharide is a guar or derivitized guar compound.
5. The method for fracturing a formation of claim 1 wherein the fluid is aqueous.
6. The method for fracturing a formation of claim 1 wherein the colemanite is added as a mixture in an aqueous liquid.
7. The method for fracturing a formation of claim 1 wherein the colemanite is added as a slurry in a liquid hydrocarbon.
8. The method for fracturing a formation of claim 1 wherein the chelating agent is nitrilotriacetic acid.
9. The method for fracturing a formation of claim 1 wherein the chelating agent is ethylenediaminetetraacetic acid.
10. The method for fracturing a formation of claim 1 wherein the chelating agent is diethylenetriaminepentaacetic acid.
11. The method for fracturing a formation of claim 1 wherein the chelating agent is hydroxyethylenediaminetriacetic acid.
12. The method for fracturing a formation of claim 1 wherein the chelating agent is methylglycinediacetic acid.
13. The method for fracturing a formation of claim 1 wherein the chelating agent is a monophosphate ester of triethanolamine.
14. The method for fracturing a formation of claim 1 wherein the chelating agent is a diphosphate ester of triethanolamine.
15. The method for fracturing a formation of claim 1 wherein the calcium is from the colemanite.
16. The method for fracturing a formation of claim 1 wherein the effective amount is less than 10 kg/m 3 .
17. The method for fracturing a formation of claim 1 wherein the effective amount is between 0.9 kg/m 3 and 10 kg/m 3 .