Dowell Schlumberger Incorporated

Janet Gulbis

Milton T King

Harold D Brannon

George W Hawkins

Method of reducing the viscosity of a fracturing fluid containing a polymer by introducing both delayed breaker and nondelayed breaker into the fracturing fluid. Preferably, the relative amounts of delayed and undelayed breaker are determined by first determining the concentration of polymer in the fracture, determining the relationship of breaker concentration for a polymer concentration to proppant pack permeability, picking a desired proppant pack permeability, calculating the amount of breaker necessary to lessen the viscosity of the polymer concentration in the fracture to the desired permeability. This amount of breaker is X. Next, the minimum viscosity of the fracturing fluid which maintains the proppant in suspension in the fracture is determined. The amount of breaker Y which lessens the viscosity of the fracturing fluid no lower than this minimum viscosity is calculated for the bottom hole static temperature and an interval of time. The amount of delayed breaker Z which upon initial introduction into the fracturing fluid releases Y is calculated. Finally, if X is less than Y, no more than X amount of delayed breaker is introduced into the fracturing fluid; however if Y is less than X, no more than Z amount of delayed breaker is introduced into the fracturing fluid. Additionally, Y amount of nondelayed breaker may be introduced into the fracturing fluid at each of its treatment stages.

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Tulsa, OK, United States of America

Janet Gulbis