| abstract |
The present invention extends the temporary temperature range for the use of magnesium oxide-delayed borate-cross linking of a galactomannan gum fracturing fluid by adding fluoride ion which precipitates insoluble magnesium fluoride. Alternatively, a chelant for the magnesium ion may be added. With the precipitation of magnesium fluoride, or the chelation of the magnesium ion, insoluble magnesium hydroxide cannot form at elevated temperatures which would otherwise lower the pH and reverse the boron-crosslinking reacting. The addition effectively extends the use of such fracturing fluids to temperatures of about 275° to 300° F. |