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Abstract

A particulate gel breaker for the controlled reduction in viscosity of aqueous acid compositions used in fracture acidizing of subterranean formations, such as in oil and gas wells, is formed for use with crosslinked polymer gels which are crosslinked with organometallic compounds, such as titanium or zirconium. The gel breaker is composed of particles containing complexing materials such as fluoride, phosphate, sulfate anions and multi-carboxylated compounds, which are capable of complexing with the organometallic crosslinking compounds of the gel. The particles are coated with a water insoluble wood resin coating which reduces the rate of release of the complexing materials of the particles so that the viscosity of the gel is reduced at a retarded rate. The gel can thus be introduced into the well at a sufficiently high viscosity for fracturing and to allow time for the acid to penetrate the formation before the acid is released.

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First Claim