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Schlumberger Technology Corporation

S Bruce McConnell

Kenneth H Nimerick

Erik B Nelson

Roger J Card

Brian Ainley

Curtis W Crown

L Jack Maberry

A method is provided for controlling the delay time of aqueous borate-crosslinked polysaccharide-based fluids for hydraulic fracturing and related applications which allows on-the-fly control of the delay time without comprising overall fluid integrity. Without having to modify the total boron content nor pH of the fracturing fluid, the delay time is controlled by adding a polyol to the fracturing fluid at a first rate, determining the resulting delay time and then adjusting the rate of the polyol addition to the fracturing fluid until the desired delay time is achieved.

On-the-fly control of delayed borate-crosslinking of fracturing fluids

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.degree. to 300.degree. F.

Method of using borate crosslinked fracturing fluid having increased

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Katy, TX, United States of America

S Bruce McConnell