Borate crosslinked guar fracturing fluids have recently been re-engineered to allow use at higher temperatures in both fresh water and seawater. A key part of this work involves control of the crosslink delay time of the fluid.
This report presents an overview of the technology available to control delay time with an emphasis on the types of processes used in current commercial systems.
Control of delay time requires control of either the pH or the availability of borate ions or both. To date, control of pH can be effective in freshwater systems. Control of borate is effective in both fresh water and seawater. This may be accomplished by using low-solubility borate species or complexing the borate with a variety of organic species.