Patent ID: 6642185
Filing Date: 2003-11-04
Classification: C09K,Y10S

Abstract:
A method for braking viscosity of aqueous fluids gelled with borate crosslinked materials comprising:adding to an aqueous fluid gelled with at least one borate crosslinked polymer a material capable of releasing divalent cations, in an amount effective to reduce the pH of the fluid and remove at least a portion of borate ion from the crosslinked polymer; complexing the divalent cations with at least one pH buffer in the fluid, where the buffer is selected from the group consisting of hydroxides and carbonates; and reducing the pH of the fluid and removing at least a portion of borate ion from the crosslinked polymer where at least 80% of the divalent cations are slowly released over a period of time up to 48 hours, and where about 20% or less of the divalent cations are released in the first 10 minutes.