Dowell Schlumberger Incorporated

The Dow Chemical Company

Milton T King

Vernon G Constien

Harold D Brannon

Janet Gulbis

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.

Method of optimizing the conductivity of a propped fractured formation

A method for breaking the fracturing fluid comprises injecting into the subterranean formation a controlled release breaker capsule including an enclosure material enveloping a breaker. The enclosure material is sufficiently permeable to at least one fluid existing in the subterranean environment or injected with the controlled release capsule such that the breaker capsule is capable of dissolving or eroding upon sufficient exposure to the fluid, thereby releasing the breaker. Using the method of the present invention, breaking of fracturing fluids is significantly improved when the temperature in the subterranean environment is from about 20.degree. C. to about 65.degree. C.

Method for treating subterranean formations

Improved fracturing processes are described which use novel aqueous hydraulic fracturing fluids. The fluids comprise: (a) an aqueous medium, and (b) a thickening amount of a thickener composition comprising (i) a water-soluble or water-dispersible interpolymer having pendant hydrophobic groups chemically bonded thereto, (ii) a nonionic surfactant having a hydrophobic group(s) that is capable of associating with the hydrophobic groups on said organic polymer, and (iii) a water-soluble electrolyte. Additionally, the fluids preferably contain a stabilizing amount of a thiosulfate salt. As an example, an interpolymer of acrylamide and dodecyl acrylate was used in combination with a nonionic surfactant (HLB of about 10 to about 14) to thicken a dilute aqueous solution of KCl and sodium thiosulfate; the aqueous solution had excellent properties for use as a high temperature hydraulic fracturing fluid.

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Tulsa, OK, United States of America

Milton T King