Method for treating subterranean formations

A method for breaking an aqueous fracturing fluid which comprises injecting into a subterranean formation controlled release capsules comprising an enclosure member containing a breaker for the aqueous fracturing fluid;

• the enclosure member comprising a homopolymer or copolymer of ethylene, propylene, isobutylene, vinyl chloride, or vinylidene chloride which enclosure member is sufficiently permeable to at least one fluid existing in the subterranean environment or injected with the controlled release capsules such that the enclosure member is capable of releasing the breaker upon sufficient exposure to the fluid.

A fracturing fluid comprising a carrier fluid, a viscosifying polymer and controlled release capsules of an enclosure member enclosing a breaker for the viscosifying polymer wherein the enclosure member is sufficiently permeable to the carrier fluid or at least one fluid existing in the subterranean environment such that, upon sufficient exposure, the enclosure member is capable of rupturing, thereby releasing the breaker.

A method for breaking an aqueous fracturing fluid which comprises injecting into a subterranean formation a controlled release capsule comprising an enclosure member containing the breaker;

• the enclosure member being prepared from a material having a water vapor transmission rate as a 1 mil film of less than about 20 g/100 in.sup.2 /24 hours at 38.degree. C. and greater than about 0.01 g/100 in.sup.2 /24 hours at 38.degree. C. and being sufficiently permeable to at least one fluid existing in the subterranean environment or injected with the controlled release capsule such that the enclosure member is capable of releasing the breaker upon sufficient exposure to the fluid.

A method for breaking an aqueous fracturing fluid which comprises injecting into a subterranean formation controlled release capsules comprising an enclosure member containing a breaker for the aqueous fracturing fluid;

• the enclosure member comprising an epoxide, polycarbonate, or polymer of ethylene oxide or propylene oxide which enclosure member is sufficiently permeable to at least one fluid existing in the subterranean environment or injected with the controlled release capsules such that the enclosure member is capable of releasing the breaker upon sufficient exposure to the fluid.

A fracturing fluid comprising a carrier liquid, a viscosifying polymer and controlled release capsules of an enclosure member containing a breaker for the viscosifying polymer wherein the enclosure member is a homopolymer or copolymer of ethylene, propylene, isobutylene, vinyl chloride, or vinylidene chloride which enclosure member is sufficiently permeable to the carrier fluid or at least one fluid existing in the subterranean environment such that, upon sufficient exposure, the enclosure member is capable of rupturing, thereby releasing the breaker.

A fracturing fluid comprising a carrier liquid, a viscosifying polymer and controlled release capsules of an enclosure member containing a breaker for the viscosifying polymer wherein the enclosure member comprises an epoxide, polycarbonate, or a polymer of ethylene oxide or propylene oxide which enclosure member is sufficiently permeable to the carrier fluid or at least one fluid existing in the subterranean environment such that, upon sufficient exposure, the enclosure member is capable of rupturing, thereby releasing the breaker.